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THE UNIVERSITY OF MAINE: MECHANICAL ENGINEERING DEPARTMENT

Senior Design Capstone EnviRobot

Emmanuel Marsh-Sachs Brian Farnsworth

Rebecca Hanks Erik Ozelius

Keith Pearson Kyle Staples Josh Stubbs

5/4/2013

This report describes the design and fabrication of robotic subsystems that have the purpose of helping to create and sustain a healthy environment. The Mechanical Engineering senior design project EnviRobot promotes this healthy environment through the use of three subsystems: a planting subsystem, an air purification subsystem, and a data acquisition subsystem. These subsystems are conceived as possible attachments to a mobile robot platform capable of incursions into areas that have been adversely affected by a man-made or natural disaster.

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TABLE OF CONTENTS

Introduction ............................................................................................................................................................ 1

Design Overview .................................................................................................................................................... 2

Final Design Descriptions ................................................................................................................................... 3

Planting Subsystem ............................................................................................................................................................ 3

Data Acquisition Subsystem ........................................................................................................................................... 4

Air Purification Subsystem ............................................................................................................................................. 6

Fabrication ............................................................................................................................................................... 7

Planting Subsystem ............................................................................................................................................................ 7

Air Purification subsystem Fabrication ..................................................................................................................... 8

Final Testing ............................................................................................................................................................ 9

Design Concepts .................................................................................................................................................. 10

Phase 1 Design ................................................................................................................................................................... 10

Focusing on the Mission ...................................................................................................................................................... 10

Mobility....................................................................................................................................................................................... 10

Power Systems......................................................................................................................................................................... 11

Solar Power Design ............................................................................................................................................................... 14

Sensors ........................................................................................................................................................................................ 15

Planting ...................................................................................................................................................................................... 16

Proof of Concept - Mindstorm .......................................................................................................................................... 17

Pursuit of a Patent ................................................................................................................................................................ 18

Phase 2: Refining The Design....................................................................................................................................... 18

Refinement Goals ................................................................................................................................................................... 18

Mobility....................................................................................................................................................................................... 19

Power Systems......................................................................................................................................................................... 19

Sensors ........................................................................................................................................................................................ 22

Planting ...................................................................................................................................................................................... 23

Robot Chassis Design and FEA Analysis ...................................................................................................................... 25

Proof of Concept ..................................................................................................................................................................... 26

Phase 2.5 Design ............................................................................................................................................................... 29

Mobile Robot ............................................................................................................................................................................ 29

Post Phase 2.5 Design ..................................................................................................................................................... 30

Shifting Focus To the Subsystems .................................................................................................................................. 30

Planting Subsystem ............................................................................................................................................................... 30

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Data Acquisition Subsystem ............................................................................................................................................. 30

Air Purification Subsystem ................................................................................................................................................ 31

Oil Subsystem ........................................................................................................................................................................... 32

Herbicide Sprayer Subsystem........................................................................................................................................... 32

Phase 3 Design ................................................................................................................................................................... 34

Planting Subsystem ............................................................................................................................................................... 34

Data Acquisition Subsystem ............................................................................................................................................. 35

Air Purification Subsystem ................................................................................................................................................ 36

Suggestions for Improvement ........................................................................................................................ 37

Conclusions ........................................................................................................................................................... 38

INTRODUCTION

In the world that we live in today, automation and robotics can be seen all around us. Automated cars built largely by robotic devices now dominate our motorways and in some cases, even navigate the roads without drivers, guided by GPS devices. Robots can be very cost effective and are sought after in industry due to their long operating hours and the precision they can attain. The idea that many of the items we depend upon from day to day are manufactured and produced by robotic systems is an important and powerful concept to understand as engineers. While some uses of robotics technology can be highly controversial – think about Armed Drone Aircraft and deep-sea oil exploration for instance - with these powerful ideas also comes the chance to produce something for the greater good of the planet.

Often, it seems there are an overwhelming amount of devices relying on robotics that, at the end of the day, do our world more harm than good. As seniors approaching graduation, our team felt as though we should produce something that would not only help the people of our world, but also some of the planet’s other inhabitants: insects, trees, and plants. The problem then was to figure out how we, as a small group of seniors, might incorporate robotics into an idea or concept that would be original and beneficial to the earth.

EnviRobot is a project focused on designing mobile robotic components that can have a positive impact on the earth by promoting clean, healthy, and diverse ecosystems with minimal harmful impacts on the environment. This was accomplished by designing and building several robotic subsystem attachments that could be mounted onto a supervisory controlled mobile platform. Each of the subsystems have the ability to assist in a multitude of environmental issues, which would allow the user to remotely monitor and rehabilitate an affected habitat.

The first subsystem developed to accomplish these tasks is a device with the capabilities of planting seeds in an affected area. When large portions of a forest are destroyed, the soil left over is rich with nutrients and has everything that is required to regrow into a lush and thriving system. Despite this, one of the major concerns of such a situation is that it is often a lengthy process to regrow into a mature forest. Another concern with slow regrowth after a natural disaster is the occurance of mudslides and sediment pollution in lakes, rivers, and streams. All of these can cause further damage, and may even lead to a tragedy like the potential loss of an endangered species. This loss affects the biodiversity of the ecosystem, and the strength of the system lies within its diversity. As one member of the web is adversely affected, the rest of the chain feels the effect, putting more and more plants, animals, and wildlife in danger. This subsystem allows a user to remotely plant appropriate seeds in the soil in an attempt to stabilize the situation and decrease natural recovery time.

In order to target specific areas for rehabilitation, a second subsystem has been developed to acquire useful data about the affected areas and to transmit that data to anyone who might need it. This data can be used to decide upon optimal locations for plant repopulation. There are many other secondary functions of this subsystem. These include the ability to supervise and monitor designated locations, thus increasing the reaction time to certain events like a forest fire.

The third subsystem is designed to purify the air within an enclosed space. This system can be used in conjunction with other environmental cleanup efforts to assist in making the local air cleaner and safer to breathe. The robot can be deployed into a hazardous or otherwise unsafe area

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to purify the air, allowing for human occupation at a later time. This subsystem is the focus of the laboratory experiments; tests will concentrate on fluid flow analysis and optimization of the duct geometry and fan configuration.

DESIGN OVERVIEW

The original goal of the Envirobot project was to create a mobile robotic platform that could incorporate multiple subsystems to allow it to either return a damaged ecosystem to health or maintain a system that was in a precarious state of balance. The mobile robot would be able to be directed into a zone that was damaged by a natural or man-made disaster and work to clean it up. At the very least, it would plant the groundwork for later, more in-depth restoration efforts. Each subsystem would be mounted on a platform with an attachment mechanism that would allow it to be attached onto the robot in a very small amount of time and with relative ease. That way, it could return to the operator after completing one task and be immediately outfitted for a second before being sent back out. The robot would have a permanent supervisory control system in order to give the operator the control to combat any issues that could arise while in the field. Each subsystem would have a separate control system that was routed to the same monitor display, allowing the operator to keep track of all of the systems at all times.

The final result of the project, however, was slightly less than intended, although it did remain true to the initial ideals on which the project was based. The actual mobile robot that would serve as a platform for the attachments was unable to be constructed due to time and other constraints. However, this was not the most important aspect of the project, as mobile bases for robots are not difficult to come by, and nearly all come equipped with a control system already in place. As we discovered, the task of designing a mobile robot from nothing is enough work for an entire capstone design project on its own. Without time for two design projects, we chose to focus on the aspect that was more in tune with the original idea of environmental restoration.

The more important aspect of the project was the subsystems, so they were the focus over the course of the later design phases. In the end, the subsystems that were fabricated were the air purification and planting subsystems. The data acquisition subsystem was fully designed, but due to costs and time restraints was not constructed. Each subsystem is detailed in its own subtitled section.

All of the subsystems were constructed so that, should a mobile platform come into the equation at a later date, they would be able to be mounted on said platform without any great degree of difficulty. This was accomplished by creating a platform from wooden boards and then mounting the subsystems on their respective platforms. Although the size of the subsystems varied, they were near enough in size and weight that they could be designed to fit on the same platform without a great deal of problems. When a mobile platform is obtained for these subsystems, the design of the mounting platform would allow them to be interchangeably mounted on a mobile robot without difficulty.

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FINAL DESIGN DESCRIPTIONS

PLANTING SUBSYSTEM

The planting subsystem was created to restore plant or tree life in an area that had been burned down by a forest fire or torn up by another natural disaster. After testing the soil to ensure that the seed being planted was going to grow in the environment, the planting subsystem would be activated, drilling a hole in the ground at that location and depositing a number of seeds specified by the operator into the ground at that location. Although the design was made for a single size of seed in order to allow a reasonable build, the scaling of the system could easily be adjusted to allow for planting of any size of seed.

Two main pieces make up the planting subsystem. The first is the hopper mechanism, which incorporates the storage unit and the system that decides how many seeds to distribute at a given time. This is the area in which the seeds are both carried and stored until the command is given by the operator to activate the mechanism. Once the command is given, the first part of the distribution device, a ratchet gear driven by a stepper motor, begins to turn, allowing seeds from the hopper to funnel down into the tube connecting the hopper to the next section of the system. This continues until the operator gives the command to cease or it reaches a set amount that it has distributed. The SolidWorks model of the hopper and the fabricated version can be seen in Figure 1 and Figure 2.

FIGURE 1: SOLIDWORKS MODEL OF HOPPER

ASSEMBLY

FIGURE 2: COMPLETED MODEL OF HOPPER

ASSEMBLY

The second part of the planting subsystem was the distribution system. Even with the hopper mechanism controlling how many seeds are released, it does not matter unless there is somewhere for them to go. The distribution mechanism utilizes a drill, stored inside a sleeve that is extended over the edge of the platform, to bore a hole in the ground at a location specified by the operator. The seeds that have been released will meanwhile be held at the end of the tube that they were deposited into until the hole has been finished, and then will be released through a mechanism that allows them to fall into the hole that has been made by the drill. Figure 3 and Figure 4 show the design model and completed product of this portion of the subsystem.

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FIGURE 3: SOLIDWORKS MODEL OF PLANTING

DRILL ASSEMBLY

FIGURE 4: COMPLETED MODEL OF PLANTING DRILL

ASSEMBLY

The completed subsystem, encompassing both halves, can be seen in Figures 5 and 6.

FIGURE 5: SOLIDWORKS MODEL OF FULL PLANTING

SUBSYSTEM

FIGURE 6: COMPLETED MODEL OF FULL PLANTING

SUBSYSTEM

The control system for the planting mechanism controls three motors. The first motor is a stepper motor that drives the ratchet gear distribution mechanism underneath the hopper, the second is a stepper motor that will lower the drill into the ground, and the third is a DC motor that will drive the drill. The controller that is being used to give commands to the motors is an Arduino Mega, which we will program using open source programming and use to run the motors in the manner desired. To transmit the commands to the motors, however, the Arduino needs to be connected to a driver chip, and the driver chips that we have chosen for this task are different for the stepper motors and the DC motor. For the stepper motors, we are using the Big Easy Driver Bipolar Motor Controller, one for each, and for the DC motor we are using a Pololu High Current Motor Driver Board. From these drivers, the commands can be transmitted to the motors.

DATA ACQUISITION SUBSYSTEM

Data acquisition is an important part of an environmental cleanup or regrowth project. Without the ability to evaluate the conditions of the surrounding area, there would be no way to assess what the robot would need to do in order to complete its task. There would also be no way for the supervisor of the robot to be able to tell what commands to give in terms of movement when they could not see the area in front of the robot. While a completely autonomous robot would rule

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out the concerns of the latter issue, the task of making it autonomous was beyond our scope for the time that we had available.

The data acquisition system ended up being comprised of two parts. The first was a soil penetrometer mounted on an assembly that would allow it to be lowered into the soil below. The penetrometer’s function is to provide the operator of the robot with data about the soil density and composition in the area around the robot. This is useful when it comes to deciding where to plant seeds, as the soil composition is a key factor in such a decision. As there are seeds that grow differently depending on areas, the soil composition is also very important in figuring out what seeds to plant in a certain location, as this may be different from what needs to be planted a thousand feet in another direction. The data acquisition subsystem was not fabricated due to its high cost, but the SolidWorks models of the design can be seen in Figure 7 and Figure 8 below.

FIGURE 7: SOLIDWORKS MODEL OF FINAL

SENSOR ASSEMBLY IN VERTICAL POSITION

FIGURE 8: SOLIDWORKS MODEL OF FINAL SENSOR

ASSEMBLY IN HORIZONTAL POSITION

The second part of the data acquisition subsystem was the camera that would be used by the operator to control the robot. Mounted on top of the mobile platform, the camera would allow the operator to see the entire surrounding area and make command decisions based on what they could see. In an area affected by a natural disaster, this is incredibly important, as being unable to see an obstruction in the path of the robot would prevent the robot from moving forward and make it unable to complete the task that it was designed to do. It is also important when it comes to the operation of the subsystems, as being unable to tell what is happening around the robot would force the operator to make inaccurate decisions on how and where to operate any of the given systems. A SolidWorks model of the camera can be seen in Figure 9, and an image of our camera can be seen in Figure 10.

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FIGURE 9: SOLIDWORKS MODEL OF CAMERA

ASSEMBLY FOR DATA ACQUISITON SUBSYSTEM

FIGURE 10: ACTUAL CAMERA FOR DATA

ACQUISITION SUBSYSTEM

AIR PURIFICATION SUBSYSTEM

A robot can easily navigate through an area where it would be hazardous or otherwise unsafe for humans to move around, such as through smoky air or through air that has a high concentration of ash particles. That was the motivation behind the creation of a subsystem that can purify the air in its immediate vicinity, cleansing it of any dangerous material or composition before returning the clean air back into the environment it came from. The usefulness of this system is not limited to areas that are affected by natural disasters; it could also be used in domestic situations for the same purpose. Imagine some form of robotic aircraft that flies around a city and reduces smog.

A comparison of the SolidWorks model and the assembled air purification subsystem can be seen below in Figures 11-12. This system consists of a duct with a fan at one end, a filter inside, and an opening for the filtered air to be expelled from. There is a straight portion of ductwork before and after the filter to allow for velocity measurements to be taken. The straight portion before the filter is elongated so that the airflow will pass through the filter in a more ordinary fashion. The filter being used is a HEPA filter, and is enough to remove a great majority of harmful particles from the air that passes through. The fan, which is a DC centrifugal style blower, can provide a flow rate of 105 CFM (cubic feet per minute) at max power.

FIGURE 11: SOLIDWORKS MODEL OF AIR

PURIFICATION SUBSYSTEM

FIGURE 12: COMPLETED AIR PURIFICATION

SUBSYSTEM

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FABRICATION

PLANTING SUBSYSTEM

Once the design of the planting subsystem was settled, construction began. The most obvious place to start building was the hopper bucket. We decided to construct as many of the individual components as possible out of wood. We incorporated a “butcher-block” assembly method for the walls of the hopper. This meant that instead of just cutting a board to the correct dimension, we cut strips of wood, glued the strips face to face and cut the correct shapes out of these new “butcher-block” slabs. The advantage of this type of construction is to utilize the side grain strength of the wood. The walls will resist a greater outward force by relying on this construction method. The actual wall construction went well, but the angled, mitered cuts to create the inverted pyramid hopper proved challenging. Creating the design in SolidWorks was relatively straightforward; however, recreating this type of geometry in wood was one of the more challenging aspects of the capstone project.

We next tackled the base platform of the hopper. This was a “butcher-block” style flat platform that all of the individual components were mounted on. We used a plywood form backer to lend more strength to the platform. On the platform, we cut and glued strips of wood for strength and aesthetics. Next, “1 x 6’s” were ripped and cut to length to be used for the trim around the platform. We not only constructed the base for the hopper/planter subsystem, but also used the same process and materials to construct the base platform for the air purification subsystem. The major difference comparing the two platforms is the size difference, as the air purification subsystem is significantly larger than the planter system.

The planting motor housing was next on the agenda to construct. The geometry was considerably less complicated than the hopper. Everything was designed as variations of rectangles with ninety-degree angles. At this point, the construction process sped up and all of the housing and supports were quickly constructed. The major criteria for this housing unit were that it had to encompass the metal motor casing perfectly. If we were careless in the construction of the housing, we would run into problems down the road when we constructed the guide pieces that this housing would slide up and down through. We also cut half inch strips of plastic from a traditional plastic cutting board and screwed the strips onto the inside of the outer housing case to provide a low friction sliding surface to allow the stepper motor to raise and lower the planter motor. We also had to router out a track in order to secure the rack for the rack and pinion gear setup into the outer surface of the motor housing. This allowed the stepper motor to raise and lower the planter motor and planter housing unit. The entire outer housing unit was mounted with heavy duty screws onto the base platform. The outer housing overhangs the base platform, allowing the planter to deploy the digger shaft into the soil to prepare a hole to accept a seed.

We next jumped over to the hopper feeding wheel. The point of this component was to separate individual seeds and feed them one at a time into a hose, which would send each seed to the planter motor. We decided to construct this paddle out of a plastic cutting board, since it was an inexpensive material that was easy to cut into the unusual shape of this particular part. The shape was rendered in SolidWorks, a copy of which we printed out and traced onto the cutting board. A dremel tool and jigs were then used to cut out the shape. The paddle wheel was press-fit onto a

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shaft to turn within the bottom pieces of the hopper bucket, giving the system a “gumball machine” type operation for seed dispensing.

The metal components were the next hurdle to overcome. We started by welding a rectangular box, which houses the motor and planting shaft. This was made out of 16 gauge sheet metal cut into the appropriate size rectangles. Holes were drilled and countersunk into the sheet metal to mount the drill motor and to secure the metal housing to the wooden sleeve that encased it. Next, a variety of shafts had to be made. The first shaft made was the planting gear shaft. This was by far the most complicated piece to make. First, a piece of ½ inch metal stock was cut to the correct length. Using a mill, a hole was drilled into the center of one of the ends for the motor shaft to be inserted in to. Next, the majority of the other end of the shaft was milled down to ¼ inch with the same mill to be able to attach to the planting gear. The next piece to be made was the gear shaft that would mesh with the rack gear on the drill housing. This was made in a very similar fashion to the previous piece: a ½ inch piece of stock was cut and a hole was milled into the end. This piece was welded to the spur gear with a MIG welder. Both shafts were then completed by drilling and tapping set screw holes to be able to transmit power from the motors they were to be attached to. The final metal piece that was made was the drill itself. This was simply made by welding sharpened wood spade bits to a piece of 3/8 inch steel shaft, creating dual cutting blades, which would easily cut through soil and prepare a hole in which a seed would be deployed.

The final step of the fabrication process was to connect all of the hopper paddle wheel pieces to the stepper motor and onto the hopper bucket. These pieces were all screwed down onto the platform next to the digger-motor housing. The hopper bucket was supported by four upright legs, and the final connection is a half inch inner diameter plastic tube connecting the paddle wheel housing to the digger-motor housing.

AIR PURIFICATION SUBSYSTEM FABRICATION

The air purification subsystem was assembled in four different phases. First, the ductwork was created to match the required design specifications. Secondly, holes were drilled at mounting points where the subsystem would later be bolted together and holes were also drilled at specified velocity measurement locations. Next, the fan was attached to the duct inlet and accommodations were made to ensure that the flow rate through the filter was correct and no flow would be lost through the ductwork. Finally, the filter was screwed into the assembly and finishing touches were made.

The ductwork was ordered from Tri City Sheet Metal and custom built according to our design specifications. The ductwork is comprised of four different sections. There are two square-to-round portions that are used as the expansion and contraction portions of the duct and there are two straight portions, which are placed before and after the filter location. The round portion of the expansion was sized to fit the fan outlet diameter, which is 3 inches. The longer of the two straight ducts is placed before the filter so that the airflow will return to ordinary flow, before passing through the filter. The length of this portion is equal to four times the diameter of the fan outlet.

Mounting holes were drilled into the ductwork by using a drill press. There were 8 holes drilled on the ends of each piece of duct that were 3/8 inches in diameter. This allowed the pieces of the ductwork to be bolted together. Five holes were also drilled on each straight duct along a single cross section on top of the duct. These were drilled about an inch away from the end where

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the filter would later be screwed into each piece. These holes were drilled to allow an anemometer probe to be placed into the duct at these locations to take velocity readings during an experiment.

Now, the ductwork was ready to accept the DC blower (fan). The blower outlet was placed into the duct inlet and a crimping tool was used so that the two pieces would fit tightly. Another problem had to be solved though. The blower when wired directly into our 12V battery would produce a flow rate of 105 CFM. The filter was rated for use between flow rates of 35-55 CFM. In order to solve this problem, we designed a circuit with a potentiometer that would control the flow rate of the blower, by varying the resistance through the circuit. Resistors where also added into the circuit to help dissipate some of the heat, since the potentiometer was only rated to handle 5W of power. Weatherproof stripping was also added to the ductwork to seal the small cracks at the connections and prevent any air from exiting through them.

Once the filter arrived, it was screwed into the duct by drilling wood screws into the plywood casing in which it was enclosed. Final touches on the assembly included sealing the holes drilled for velocity measurement with rubber stoppers, screwing the assembly down into a wooden base with a holder for the fan, and fastening the duct down onto the base with a metal strap.

FINAL TESTING

Looking back and evaluating the entire fabrication process, several things can be noted. Overall, the decision to utilize wood for the majority of the project was a wise decision. Wood is not only a renewable resource, but all of the necessary tools to construct the subsystems were accessible; consequently, Crosby lab was not the only option during the busiest parts of the semester. Subcontracting out the duct work for the air-purification subsystem was also a good idea, due to the complex geometry of ducts and lack of access to the appropriate tools to accomplish this task.

An area of the project that could have been improved upon pertained to the fabrication of the hopper paddle wheel. This was the component that feeds one seed at a time into a rubber hose and ultimately to the planter motor. Two facets of this piece needed improvement. First, a decision was made to press fit the plastic wheel onto the smooth drive shaft, relying on friction and the deformation of the plastic to keep the wheel attached to the shaft. Due to the high levels of torque the paddle wheel experienced, the wheel ultimately ended up slipping and the seeds were not dispensed properly. The second aspect of the paddle wheel that could have been improved had to do with the teeth spacing. At the time of construction, the size of the seed had yet to be determined, consequently, the tooth spacing was too large. This allowed several seeds to enter the gap between teeth, which led to the paddle wheel becoming jammed.

Another area of improvement for the project was motor sizing. The motors were sized according to torque specifications, not speed. Ultimately, the stepper motors had the necessary amount of torque, but moved so slowly that demonstrations were impractical. If this were to be built again, different stepper motors would be purchased to create a better balance between strength and speed. There were two stepper motors used in the planting mechanism, each with different requirements. Out of convenience, the motor chosen for the high torque application was

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also used for the lower torque process. Ideally, two different motors with different specifications could be used to optimize the functionality of the subsystem.

Overall, most of the design choices worked well for the final project, especially the use of wood where possible. Wood was cheap, readily available, and production never had to stop due to lack of supplies. Access to tools was rarely restricted, except during the metal fabrication processes. Ultimately, everything turned out how the project was envisioned to be, with only minor hiccups along the way, which were easily overcome.

DESIGN CONCEPTS

PHASE 1 DESIGN

FOCUSING ON THE MISSION

In this initial design phase, there were an extremely large amount of unknowns involved with the process of creating the mobile robot. Many questions regarding size, mobility, and planting area started to repeat themselves and we found ourselves going in circles when it came down to these big questions.

When we realized that there were too many variables in the problem, we also realized that we had to make some assumptions about the carrying capacity, area of repopulation, and several other factors. Initially, a lot of research was done as a team regarding the sizes and densities of certain seeds like corn, peas, and a multitude of tree seeds. This data gave us a good concept of the weight we could carry as well as the size that the planting apparatus would have to be to plant a desired seed.

We began with the idea of building a complete mobile robot from scratch that would be used to plant seeds and acquire data about the environment. The project was broken into four groups: planting, mobility, power systems and sensors. Each group was responsible for researching their topic, creating designs within SolidWorks, and ensuring that their design would be easily integrated into the robot. Each subsystem is detailed below.

MOBILITY

After researching commercially available tracks, it became clear that building the tracks would be more cost effective and would better meet the needs of our robot. We estimated the final weight of our robot at around 200 lbs, and with this in mind we decided to make each track 6 inches in width to help better distribute the weight of the robot. At this width, two driving chains are needed to keep the tracks stable while moving, so we decided to weld each chain to a small piece of steel in order to hold the chains together. This is illustrated in Figure 13.

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FIGURE 13: SOLIDWORKS MODEL OF A SINGLE TRACK LINK

POWER SYSTEMS

In order to ensure the success of the EnviRobot, careful design of the power system was crucial. There were several subsystems that needed to be integrated together in order to complete a fully functioning power system. Our team had to work on sizing the motors, choosing batteries for ample power storage, and integrating a solar regeneration system. Four capable motors were sized and selected. Allowing room for implementation of a spur gear transmission was important, since high-speed power was not as necessary as low-end torque for this application.

The robot was going to be driven using the “tank drive” method. This meant that turning left or right would be achieved by controlling the motors supplying torque to each track at different speeds. The robot would then turn in the direction of the motor that was operating at lower speed.

MOTOR SIZING

It was decided early on in the design process that electric motors were going to be used to provide power for this robot. The power systems team also narrowed the selection down to DC stepper motors for ease of control. A stepper motor works on the same principles of a regular DC motor. The main difference is that there are equally spaced magnets called poles, which allows voltages to be supplied at each pole individually for more precise position control.

Four motors, which were required to power the proposed mobility design, were selected, and ample space was left in the design to incorporate a spur gear transmission. Because the front motors need to be able to turn the mobile arms over obstacles like downed trees, the torque requirement on the two motors in the front of the robot would be greater than the torque requirement on the back two motors. The two selected motors for the back were the 34Y High-Torque Stepper motors shown in Figure 14. These motors weighed 8.4 lbs. each and could provide a peak torque of 1200 ounce-inches. A schematic of the 34Y motor created in a SolidWorks drawing can be seen below in Figure 15.

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FIGURE 14: 34Y HIGH-TORQUE STEPPER MOTOR

FIGURE 15: 34Y HIGH-TORQUE STEPPER MOTOR

The two selected motors for the front were slightly bigger and more powerful. These 34K motors weighed 15.1 lbs. each and could provide a peak torque of 2725 ounce-inches. An image of this motor can be seen below in Figure 16.

FIGURE 16: 34K HIGH-TORQUE STEPPER MOTOR

A SolidWorks drawing schematic of the 34K motor can be seen below in Figure 17.

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FIGURE 17: 34K HIGH-TORQUE STEPPER MOTOR

BATTERY SELECTION

Four main factors had to be considered when selecting the batteries for our robot: battery life, accommodation of solar regeneration, weight, and size. It was decided early on that Lithium-Ion batteries were going to be used for this project due to their high energy density. This allows the batteries to supply power to the robot for a longer duration between recharge cycles and it also allows the batteries to be lightweight. Two 20AH/12V, Lithium-Ion batteries were chosen. An image of the battery modeled in SolidWorks can be seen in Figure 18.

FIGURE 18: SOLIDWORKS SIZING MODEL OF BATTERY

In this design, the batteries were wired in series in order to double the effective voltage supplied. This was done because the controller chassis that was selected for use on the robot required 24 volts, and wiring two 12V batteries in series instead of buying one 24V battery would cut costs significantly. A list of specifications for the selected batteries can be seen in Table 1 below.

TABLE 1: SPECIFICATIONS OF LITHIUM ION BATTERIES

Voltage (V) Duration

(AH)

Weight (lb) Length (in.) Width (in.) Height (in.)

12 20 7.4 8.8 3.85 6.5

Since the batteries were wired together in series, not parallel, the power life ratings do not

combine additively. This gives our robot a total of slightly less than 20AH to consume. This is because fully depleting Lithium-Ion batteries before recharge significantly decreases the capacity of

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the batteries. This also does not take into account the projected power gain from the solar regeneration system. A simple equation below shows the projected life of our robot between recharging.

(

) EQUATION 1

LB = Life of the Battery (Amp-hours)

LC = Life Consumed by the Robot in one Hour (Amp-hours)

t = Time Remaining Before Recharge (Hours)

Assuming a consumption of 5 Amp-hours from the robot in one hour:

(

)

(

)

This battery selection provided a cost effective and lightweight solution for the phase 1 design.

SOLAR POWER DESIGN

Solar power is a quickly growing technology in power regeneration. This is why we decided to incorporate a solar system into the Envirobot. Our initial design involved using a Suntech 20W Solar Panel mounted flat on the top of the robot chassis. This 90-degree mount angle was justified as the best mounting angle by consulting with our power systems advisor, Professor David Dvorak. This panel would be wired into a circuit with the batteries and a charge controller to prevent uneven charging and overcharging. A SolidWorks model of the solar panel can be seen in Figure 19 below.

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FIGURE 19: SOLIDWORKS MODEL OF SUNTECH 20W SOLAR PANEL

SENSORS

FIGURE 20: SOLIDWORKS MODEL OF PHASE 1 SENSOR ASSEMBLY

One of the capabilities we found was very important for the robot was its data acquisition ability. The ability to retrieve data from an area in need of regrowth is extremely useful, since acquiring data about the surrounding area can be helpful in deciding how many seeds to plant and which type of seeds would grow best in a given area. It can also provide information about areas to avoid. One of the important factors in the research of sensors was what the robot should be sensing. Since a user-controlled robot seemed more viable than an autonomous one, cameras would be necessary in order to allow the user to make decisions based on the visual surroundings. Depth sensing was discussed, but a camera seemed useful enough for our purposes. The next most important type of sensor was the soil sensor. We knew that factors such as pH, salinity, and moisture content were important factors from a planting standpoint.

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After considerable research, we learned that many of the soil analysis technologies exist only in laboratory environments and are not portable. In most cases, soil samples are taken back to a lab for chemical analysis. However, we did find a sensor that was able to measure soil moisture content in the field. The Phase 1 design utilized the Stevens Hydra Probe Soil sensor, which measured, among other factors, the water content of soil. Soil moisture content is important for the growth of new seeds, so this sensor could help us choose the best possible locations for planting. The probe has an attachment that can record and transmit data to a computer for further analysis, and the sensor has prongs that need to be inserted into the soil so electrical signals can be sent out to measure the moisture content. We designed a mechanism, as shown in Figure 20, to deploy the sensor. This mechanism employs a motor to drive the sensor into the ground.

PLANTING

At the early aspects of the design phase, not much time was spent deciding any specific seed or plant, because with the use of SolidWorks the design could just be scaled to match the required dimensions. Instead the primary focus covered three topics: the initial concepts of planting methods, the initial estimate of weights and sizes, and also the initial estimate of a budget for the production of the said robotic planting device.

A large problem that was faced with planting was the method in which one would actually plant a seed using a robotic apparatus. For obvious reasons, when creating a mechanism to do a specific task, the true difficulty is not in completing the task, but to complete the task without overcomplicating the design. The introductory design process consists of looking at the task being performed and actually figure out ways in which the cost or method could be reduced and simplified.

FIGURE 21: SOLIDWORKS MODEL OF “SHOVEL-WHEEL” PLANTING MECHANISM

This process of reducing and simplifying the methods used produced the first planting design, which incorporated a “shovel-wheel” mechanism to perform the task of planting the seeds. A SolidWorks model of the “shovel-wheel” mechanism can be seen in Figure 21 above. The planting mechanism also requires seeds to dispense into the mechanism, which can be accomplished by using a gravity fed hopper. Since our team wanted to try to cut costs where necessary, especially since the other portions of the project appeared to have high costs associated with them, our team decided that in this introductory design phase a gravity fed hopper would suffice. The gravity fed hopper can be seen in Figure 22 below.

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FIGURE 22: SOLIDWORKS MODEL OF HOPPER USED WITH “SHOVEL-WHEEL” MECHANISM

This mechanism had its pros and cons, but it became apparent after further investigation that this would not work in our final design. To see why this design failed where our phase 2 design succeeded, please refer to the phase 2 planting section.

PROOF OF CONCEPT - MINDSTORM

In order to rapidly test mobility designs, a Lego Mindstorms kit was purchased. The kit contains three servo motors and an Intelligent Brick, the latter used for controlling the motors and reading inputs from sensors included in the kit. The Mindstorms is controlled using software created by National Instruments which is a derivative of LabVIEW. The software is a block based programming language that allows the user to very easily control the movement of the Mindstorms robot. For example, using the “Move” block, the user can select the power at which to turn the servo motor as well as how much to move the motor in degrees or rotations and in which direction. For our purposes, we created a tracked robot with a one degree of freedom arm in the front as shown in Figure 23. Our main goal was to determine how well the arm performed in assisting the robot over a log twice the size of the tank tracks. Through testing, we have determined that the arm does help pull the Mindstorms up onto the log.

FIGURE 23: LEGO MINDSTORMS CLIMBING OVER WATER FILTER USED AS A LOG.

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PURSUIT OF A PATENT

Whenever an original idea is conceptualized that is both reasonable and profitable, it is important to get this idea protected. The current method for protecting an idea in the United States is to get an approved patent with the U.S.P.T.O. After doing numerous searches on the uspto.gov website, our team realized that the idea of an environmental restoration robot was an original one and decided to proceed with writing a patent. It would be a great accomplishment to get a provisional patent with the U.S.P.T.O. and it proved to be a valuable learning experience along the way.

There are three different kinds of patents. Design patents are patents on one specific design for a product. Conceptual patents are patents on a wide range of designs for a solution to a problem. Method patents are patents on a separate method of creating a known solution to a problem. Each type of patent is slightly different in the way that it is written. First, our team started out by writing a design patent and later switched to a conceptual patent. The composition of each patent type, our writing process, and the reason for the change is explained in more detail below.

DESIGN PATENT

The process of writing the design patent began by ensuring that our concept had not yet been patented within the United States. After doing numerous searches of existing patents, and patent applications we determined that our concept had not been patented. This began the research phase into how a patent is written including the language used, and how to fully encompass our concept. When we began the patent we were still in the beginning of the design phase, and the drawings and SolidWorks models were not finalized. This made creating figures for the patent difficult and we decided to start on the claims before working on the figures and detailed description. In the claims section our goal was to cover as much about the concept as we could while keeping in mind future expansion of the project. As we wrote our claims it became apparent that we were trying to write a conceptual patent instead of a design patent. Our design patent can be found in Appendix 1.

CONCEPTUAL PATENT

A conceptual patent covers a wide range of designs for a solution to a problem. That is exactly why we decided to switch to writing a conceptual patent instead of a design patent. The problem that we are trying to solve is one of environmental rehabilitation in disaster areas. Our solution is a controllable, robotic body that performs tasks towards this goal. We wanted this patent to cover more than just one specific type of robot design. However, due to time constraints and issues with our design being too similar to existing patents, we decided that it would be in our best interests to focus on the design and fabrication of our project. The patent was put to the side, and we were unable to find the time to return to it.

PHASE 2: REFINING THE DESIGN

REFINEMENT GOALS

During the second phase of the design process, our entire team worked to improve on the original phase 1 design. In phase 1, multiple solutions to each problem were proposed, and we

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decided as a team which solution would work best. Those solutions were then further developed using SolidWorks and by building prototypes. The Phase 2 design is where a design team reiterates their original design through the design process to make improvements on the design of the previous phase. Having multiple design phases is important for the successful development of any engineering product or solution.

During this phase our team focused on redesigning with three main goals as guidelines. These goals were improving ease of manufacturing, cost effectiveness, and weight reduction. Overall, we reduced the amount of DC motors required for locomotion, reduced the amount of time needed to weld the mobile track together, decreased total weight, and improved the effectiveness of the proposed planting mechanism. The specific changes that we made to improve upon our design for each system are explained in more detail below.

MOBILITY

In order to reduce the time required to build the Phase 1 tracks, we decided to design tracks that did not require as many welds. One of the key features our group needed to bring into the redesign of the tracks was the use of two chains to drive the track. Instead of welding each chain to a steel plate to connect the two chains, we decided to bolt them together using a small diameter pipe to keep the chains separate. This would involve disassembling each piece of chain to replace the pins with bolts. A thin steel plate would also be bolted between the chains in order to help keep dirt and debris from getting caught up in the chain, as illustrated in Figure 24. To help cut down on the time spent welding we would use sprockets as supports for the middle of the track instead of casters. The mounting of the sprockets is shown in Figure 25.

FIGURE 24: SOLIDWORKS CLOSE UP OF TRACK

DESIGN

FIGURE 25: SOLIDWORKS MODEL FULL TRACK

DESIGN

POWER SYSTEMS

Several changes were made to the power system design in Phase 2 to improve on the initial design. These changes included selecting new motors for the powertrain and changing the battery type.

MOTOR RE-SELECTION

Since three motors were now required to power the proposed mobility design, the amount of DC motors incorporated into the design dropped from four to three. This change allowed for a cost reduction, weight reduction, and increased the amount of free space inside the robot chassis. Our team also realized that with the new design, smaller motors could be used in the back for

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forward motion of the tracks, while one motor could be used in the front for the integrated rotation of both arms. This was proven by prototyping with the Lego MINDSTORMS kit and allowed for another cost reduction. DC motors with built in planetary gearboxes were also selected for this design phase. The motors that were selected were two 11YPG motors and one 23YPG motor. Images and SolidWorks schematics drawings for the 11YPG motor can be seen in Figure 26 and Figure 27 below.

FIGURE 26: 11YPG DC MOTOR AND PLANETARY GEARBOX

FIGURE 27: 11YPG DC MOTOR AND PLANETARY GEARBOX

Images and SolidWorks schematics drawings for the 23YPG motor can be seen in Figures 28 and 29 below.

FIGURE 28: 23YPG DC MOTOR AND PLANETARY GEARBOX

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FIGURE 29: 23YPG DC MOTOR AND PLANETARY GEARBOX

In Phase 2, drivers and encoders were also chosen for each of the motors. The drivers were required for controlled driving of the motors. The encoders were to be mounted on the shaft where they could relay a signal back to the controller. The only criteria for choosing the drivers was to make sure that they were compatible with our motor selection and that they were inexpensive. It was decided to use MBC15081 drivers. The current range for this driver is 0.3 to 1.5 A and the voltage range is 12 to 24 V and they allow for up to 1600 steps per revolution. This driver is very inexpensive and is recommended for our motor type. The criteria for choosing the encoders was that they needed to be rotary type, fit on the shafts, and allow for a wide enough rpm range. ENC-A2N, single-ended rotary encoders were selected for this purpose. These allow for up to 1024 cycles per revolution and could be made to fit a bore size range from 0.079 to 0.394 inches.

BATTERY RE-SELECTION

The only change that was made to the battery selection in Phase 2 was a swap from normal batteries to deep-cycle batteries. Deep cycle batteries were required for integration with the solar regeneration system. Deep cycle batteries are designed to be deeply discharged using most of the batteries capacity regularly. This would be required to maximize the time that the robot could be out in the field doing its job while the solar panels regenerated the charge capacity in the battery. A performance chart for this battery can be seen in Figure 30.

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FIGURE 30: 12V/20AH DEEP CYCLE LITHIUM ION BATTERY PERFORMANCE CHART

SENSORS

After more research into the capabilities of the sensor, as well as a cost reduction analysis, we as a group decided the Stevens Hydra Probe sensor was no longer viable. At several thousand dollars for one sensor, the sensitivity of the sensor to how it was plunged into the earth became too inconvenient. We began to have some trouble finding viable sensor options, so we spoke to Professor Ivan Fernandez to gain some insight. After a long discussion about the viability of portable soil sensing in general, we decided our best option would be some sort of penetrometer. A penetrometer measures soil compaction, which is a very important indication of soil fertility. If the soil is too compact (which would be very possible at the site of a natural disaster) the roots would not be able to spread adequately. The compaction of the soil can also provide information about the organic matter content and moisture content of the soil. Further research showed that very few penetrometers exist which provide a digital output. We discussed several design options, such as pointing a camera at a display and snapping a photo to document measurements, but we decided to go with a digital penetrometer called the Spectrum Field Scout. This sensor is a little pricy, but the cost reduction efforts of the rest of the project and the ability to analyze digital data on-the-go appeared to be the most probable solution. A new mechanism was designed to insert this sensor into the ground. The new mechanism is very similar to the Phase 1 mechanism with a few modifications due to the larger size of the new sensor. A SolidWorks model of the sensor is shown in Figure 31.

FIGURE 31: SOLIDWORKS MODEL OF PHASE 2 SENSORS

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PLANTING

Phase 2 planting took many ideas and concepts from the first phase of planting and improved the planting mechanism to where it would end up for the final design phase. The Phase 1 planting mechanism was a good design, with benefits such as simplicity in machining and making the components necessary to produce the final design, but with further time and investigation two other designs produced two systems that did everything that Phase 1 planting did and more.

The first of the two new Phase 2 designs was initially trying to respond to the issue that the planting mechanism from Phase 1 had to press into the ground, thus wasting valuable battery life and also possibly compromising the planting mechanism itself. The challenge of completing all the steps required to plant a seed while also maintaining simplicity seemed to increase in difficulty when dealing with rotating parts such as screws, but as a team we felt that it was a risk worth taking. The initial concept for the Phase 2 design concept took the idea of a screw and incorporated an inner hollow sleeve that could deposit the desired seed through, thus increasing accuracy of seed placement, which can be seen in Figure 32 and Figure 33.

FIGURE 32: SOLIDWORKS MODEL OF HOLLOW

SLEEVE VIEW

FIGURE 33: SOLIDWORKS MODEL OF SCREW

PLANTING MECHANISM

After further investigation, the bladed tube design from above appeared to have some flaws that could possibly compromise the planting mechanism. The largest of these issues was the fact that having a hollow tube that is plunging into the ground would create a soil sample inside the tube, thus compromising the ability for the seed to drop through the hollow tube into the ground. There were many different ideas in which our team had to solve this issue. Some of these ideas incorporated a gate like mechanism that could open and close using some sort of electromagnetic locking and unlocking mechanism, while others tried to incorporate an outside tube in which the seed would actually fall through, which we found would decrease the accuracy of the system.

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FIGURE 34: SOLIDWORKS MODEL OF FINAL

PHASE 2 DESIGN WITH DRILL SLEEVE RAISED

FIGURE 35: SOLIDWORKS MODEL OF FINAL

PHASE 2 DESIGN WITH DRILL SLEEVE LOWERED

The second concept that was created incorporated many of the same ideas of the previous designs, while also allowing more versatility for the operator. Shown in Figure 34 and 35, the new design allowed for full control over drill speed, the number of seeds being planted into a hole, the depth of the hole, and the possibility for a large range of seed sizes to be used using the same relative method. One assumption that was made in this design was the concept of a nutrient encapsulated seed or pellet that would appear to be of similar size to a pellet used in a pellet gun. This assumption of a nutrient encapsulated seed allowed for greater ease in the general transportation of these seeds, since it would allow non-circular seeds to roll down a circular tube for easier deposition. The ability to select the seed count for a specific hole is dependent on the amount of partial rotations that the hopper mechanism is able to make. This hopper mechanism is similar to a mechanism that one would find in a gum dispenser unit and can be found in Figure 36. This mechanism is attached to the hopper structure shown in Figure 37, allowing the supervisor to have complete control over the quantity of seeds being deposited.

FIGURE 36: SOLIDWORKS MODEL OF HOPPER

MECHANISM, SEED DISPENSER

FIGURE 37: SOLIDWORKS MODEL OF HOPPER

OUTER SHELL

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ROBOT CHASSIS DESIGN AND FEA ANALYSIS

FIGURE 38: SOLIDWORKS EXAMPLE FEA ANALYSIS

In the process of Phase 2 design, the need for a frame to support the weight of all the components was realized. A tube frame was chosen as the method that was the most cost effective and easiest to manufacture. Outer dimensions were chosen based on an initial size of 2x4x1.5 feet. Multiple 3D sketches were done in SolidWorks outlining different first-pass frame designs that made intuitive sense. The 3D sketch was then converted into a tube frame using the “Structural Members” feature. Two different tube sizes were used: 1” schedule 40 tubing and 1/2” schedule 40 tubing. Three different materials that were chosen to be used were plain carbon steel, 4130-crhomoly alloy, and 6061-T6 aluminum alloy. Images of the two different frame designs, Figures 39 and 40, are shown below:

FIGURE 39: SOLIDWORKS MODEL INITIAL FRAME

DESIGN

FIGURE 40: SOLIDWORKS MODEL OF SECOND AND

FINAL FRAME DESIGN

The FEA analysis was completed by idealizing the loading situation of the frame. The four lower corner nodes were fixed, and a load of 150 pounds was evenly distributed across all bottom members to simulate the estimated load of the components inside the chassis. The weights of the chassis were also calculated using the mass properties feature. This made a weight versus deflection analysis possible in order to find the strongest chassis that weighed the least. The data in the following table shows the results from the numerous analyses done. From the data below, it is obvious that the second frame design was better than the first one since the second one weighs and deforms less under the same load. The best material would seem to be 1” 6061-T6 tubing, but 4130 steel was chosen as the final material due to the difficulty of manufacture for aluminum alloys.

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TABLE 2: DESIGN FEA COMPARISON

Frame:

Frame 1 (.5"

Tube)

Frame 2 (.5"

Tube)

Frame 2 (1"

Tube)

Plain Carbon Steel

Max Stress (kPa) 202893 107419 32960

Yield Strength (kPa) 220594 220594 220594

Max Stress/Yield

Strength 0.920 0.487 0.149

Max Disp. (mm) 4.929 1.754 0.3408

Weight (lbs) 45.05 44.77 87.1

4130 Alloy

Max Stress (kPa) 202621 107339 32933

Yield Strength (kPa) 460000 460000 460000

Max Stress/Yield

Strength 0.440 0.233 0.072

Max Disp. (mm) 5.04 1.794 0.3485

Weight (lbs) 45.34 45.06 87.65

6061-T5 Aluminum

Max Stress (kPa) 202881 107415 32959

Yield Strength (kPa) 275000 275000 275000

Max Stress/Yield

Strength 0.738 0.391 0.120

Max Disp. (mm) 15 5.337 1.037

Weight (lbs) 15.59 15.5 30.15

PROOF OF CONCEPT

Many of the ideas and designs the group developed required further scrutiny about the feasibility and practicality of the concepts. At this point in the year, most of the engineering experiences the individual team members had been exposed to were focused on classroom learning and the studying of books. We, as a group, were less exposed to the hands-on building and implementing of designs. This situation often leads to inexperience with regards to building practices and construction techniques. The idea of actually building proof of concepts became an integral part of the design spiral. We would learn if particular designs were functional, if they served the intended purpose, and if they were possible to build. The proof of concepts we chose to pursue were not only an inexpensive way to bolster our confidence in our designs, but they created models which acted as a springboard for further design ideas, as well as functioned as 3-D physical items that could be used as props when the team met to plan and design later steps of the project.

The first proof of concept built was the track assembly, which fell under the Phase 2 mobility. We were exploring the idea of using a set of motorcycle chains traveling around sprockets to propel our robot. These chains would have metal pieces either welded or bolted to the individual tracks to provide traction and grip in order to climb over or circumvent obstacles. Since money was a concern, and this was not a major aspect of the project, “junk” material was collected and used to

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build this proof of concept. A motorcycle chain and sprocket were acquired from a local metal junkyard. The chain links’ connecter rivets were ground off with a grinding wheel and bolts were used to replace the rivets. This functioned as a means of making the chain whatever our desired length needed to be, as well as providing a means of attachment for the metal traction plates.

We were also able to procure a standard PVC kitchen cutting board, which was cut with a Dremel tool into the appropriate shapes of the sprockets. Since we had a sprocket from the junkyard, we used it as a template for cutting the remaining sprockets. The sprockets were attached to each other by means of standard threaded rod. Refer to Figure 41 for a photograph of the finished track proof of concept. The things missing from the model include a housing unit the threaded bolts would attach to and a tensioner mechanism, which functions to keep the chain taught. These add-ons were going to be the next steps, but due to the direction the project took, a track system and subsequent further development of a track system, became unnecessary.

FIGURE 41: PHASE 2 CHAIN TRACK PROOF OF CONCEPT

The next proof of concept we developed was a mechanical seed dispensing system. We designed an apparatus, which utilized a ratchet wheel system, which, as it clicked to the next position, carried a seed along with it to dispense one seed at a given time. The seed would be gravity fed down a tube until it met this ratchet. The ratchet had a notched wheel, the notch being the size of one seed. The wheel would move forward one notch at a time, allowing a single seed to move beyond the wheel. Once the seed was beyond the wheel, it would be gravity fed into the next step of the planting mechanism. We were unsure of how the ratchet would work, so a proof of concept was built. We cannibalized a length of PVC pipe, scrap 1 x 4’s, and a socket driver for materials. A hollow box was built with the PVC pipe glued into it. We attached a carved wooden wheel onto the end of a ratchet, which is secured to the side of the box. As the box moves up and down, the ratchet is engaged, turning the wheel, dispensing one seed at a time. Refer to Figure 42 for a photograph of this proof of concept.

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FIGURE 42: PROOF OF CONCEPT OF THE MECHANICAL SEED DISPENSING SYSTEM

The third proof of concept we built consisted of a metal cutting instrument designed to dig a hole for seed deployment. This project served two functions. Not only did we cut and weld the cutting blades, several team members learned to weld during this build. Welding is a skill necessary for mechanical engineers; many of us have not previously had the opportunity to learn welding. So, we learned a new skill and built an effective dirt-cutting implement. We cut three wood spade bits in half length-wise and welded them onto the end of a hollow metal pipe. The purpose of the pipe being hollow was to create a path for the seed to travel from the ratchet mechanism into the newly dug hole. See Figure 43 for a photograph of this digging apparatus.

FIGURE 43: PROOF OF CONCEPT OF THE HOLLOW SHAFT SHARPENED HOLE DIGGING APPARATUS

The three “proof of concepts” not only validated our design ideas, but also created an avenue for several group members to gain experience in Crosby Lab. Group members gained experience with welding, as was mentioned previously. We also learned proper techniques regarding the safe use of basic tools, including: drills, wood and metal chop saws, drill presses, rotary wood cutting tools, and miscellaneous carpentry tools. All of this was proven to be very beneficial in the following semester when we started constructing our robot systems.

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PHASE 2.5 DESIGN

MOBILE ROBOT

Halfway through the semester, we changed the direction of our project goals in order to save time and focus on other problems. We decided that we were going to purchase a mobile robot and add each system as a subsystem on top of the robot’s chassis. It was important to make sure that all considered mobile robots would be able to complete all of the necessary tasks for planting, sensing, mobility, and control. Eventually, the selection was narrowed down to three different robots. The LT2-F Surveillance Robot, the H2D-S Surveillance Robot, and the H2D-S with a 5-Axis Arm all met our needs. After deciding that the robot with the arm was too expensive, the other two were compared by using the data in Table 3 below.

TABLE 3: SPECIFICATIONS OF BOTH MOBILE ROBOTS

Robot Length(in.) Height(in.) Width(in.) Carrying

Capacity(lbs.)

Life(hrs.) Price($)

LT2-F 27 7 18.625 Not Specified 2.5-8 9,283

H2D-S 38 9.5 20 50 1.5-8 12,349

After looking at the specifications of the robots, we decided that the H2D-S would give us

the size and carrying capacity that was required to build and attach our subsystems. A picture of this mobile robot and its controller can be seen below in Figure 44.

FIGURE 44: HD2-S MOBILE ROBOT

This robot came equipped with a completely controllable pan and tilt 27X zoom camera. This high-resolution camera allows for 360-degrees of pan and 110-degrees of tilt. There is a pre-built roll cage on the robot that increases rigidity, prevents rollover, and allows ample space for mounting our planting system. The remote pictured on the left controls the motion of the robot for forward, reverse, and turning. This remote also controls the pan and tilt of the camera. This robot is

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made out of welded aluminum, so it is lightweight, durable, and sealed water-tight. Custom treads and chains make it suitable for our mobility purposes.

POST PHASE 2.5 DESIGN

SHIFTING FOCUS TO THE SUBSYSTEMS

With incorporation of a mobile robot appearing to be out of the picture, we decided to place all of our primary focus on the subsystems that could be used, as well as the conceptual patent work that could be done. We initially produced five different subsystems, which could each be used as separate apparatuses on the robot. These apparatuses incorporated both agricultural and disaster response systems, therefore increasing the productivity of the robot and supervisor.

The two subsystems that were conserved from the previous phases are Planting and Data Acquisition. These were the subsystems that had the most work put into them in the previous design phases, so we felt it was necessary to stick with our original ideas and concepts regarding both designs. The positive aspect of this is that our Phase 2 designs that would have been incorporated into the mobile robot platform can also be used for the subsystems, with the addition of certain scaling and positioning modifications.

PLANTING SUBSYSTEM

The large benefit with the planting subsystem was that our team had already designed what we believed was an effective seed dispensing and planting unit. There were many small changes in the design. These changes were needed since the new design incorporated changes in the surface dimensions on which the unit was to be mounted and the depth in which the drill had to penetrate, due to the added height of the mobile robot. More time was spent analyzing the design and figuring out ways to incorporate Arduino controllers, as well as waterproofing the hopper, controllers, and motors.

DATA ACQUISITION SUBSYSTEM

Fortunately, several of our ideas remained fairly unchanged despite large changes in the overall project. The sensors portion of the project was changed to be the data acquisition subsystem. The mechanism with the penetrometer remained very similar to the Phase 2 sensor design. Due to changes in the robotic platform, a camera once again became necessary. Research revealed a camera called the X10 XX34A Airsight Wireless IP Camera, shown in Figure 45. This would suit most of our needs with a single camera. The addition of several different cameras with less ranges of motion was discussed, but the single camera seemed to be a better option. The camera we decided on has a 270 degree horizontal rotation, which when paired with a 60 degree viewing lens provides an almost completely comprehensive view. In addition, the camera can tilt 120 degrees vertically. The camera transmits video through a WiFi network and can be accessed from any computer through the internet, making the robot very easy to control. This camera, combined with the previous sensing mechanism, form the Phase 2.5 data acquisition subsystem.

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FIGURE 45: XX34A AIRSIGHT WIRELESS IP CAMERA

AIR PURIFICATION SUBSYSTEM

Since the redesign of the Phase 1 design, an air cleaning and purification subsystem was selected as one of the possible subsystems. An enclosure was designed in SolidWorks and is pictured below. This enclosure was designed around a cheap and easily obtainable HEPA filter that would be effective for everything the system might need to do. It has an activated charcoal filter portion that can be attached for removing chemical smells as well. This HEPA filter was modeled in Solidworks and is included in Figure 46 of the assemblies below. The flow rates that can be achieved with these designs would more than likely have to be determined experimentally, as computational fluid dynamics calculations may not be able to deal with filters.

FIGURE 46: SOLIDWORKS MODEL OF SECOND ENCLOSURE DESIGN

A significant problem at this stage was finding a way to power a pump that is powerful enough to pump large amounts of air through the system. An initial thought was to disassemble a shop vacuum for its pump, but those pumps run on AC power and draw a massive amount of amperage, making battery power difficult. The most viable option at that point was to use one or more computer cooling fans. There are many advantages to using these fans. They run on 12 VDC, which is perfect for being run off of a large array of batteries, they draw a fairly low amount of current, which helps to ensure the system can run for extended periods of time, they can be found in the correct size for this application, and they are very inexpensive. One design of the 120 mm computer fan was selected and modeled in SolidWorks. The Sunon PSD4812PMB1 120 mm fan was the best candidate at this point, as it had an output of 200 cubic feet per minute of air, could spin up to 4000 rpm, and cost less than $10 online.

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OIL SUBSYSTEM

Another one of the subsystems to be designed was an oil or harsh chemical clean up system. Currently, when a harsh chemical is spilled on land, an absorber is poured onto the spill, and once the absorber has neutralized the chemical it is removed from the spill site. Our design goal was to create a system to complete this task without the need to expose humans to toxic chemicals. The subsystem would distribute an absorber, allow the chemical to be absorbed and then vacuum the site to finish cleaning the chemical. This subsystem was put on hold indefinitely to focus on the other four subsystems.

HERBICIDE SPRAYER SUBSYSTEM

One of the five subsystems that were created in the conceptual phase of the design process was an herbicide spraying subsystem. This system could be used on the robotic base to spray herbicide on weeds, dense mosses, and ferns that are preventing desired vegetation types from thriving. With an interchangeable pressurized tank incorporated into the system, it could also be used to spray nutrients promoting growth of the desired vegetation. This is an important part of restoring local flora that is often overlooked.

The subsystem design contains three main components. These components are methods for storage, transport, and disbursement of a desired fluid. Storage of the fluid is achieved by a removable pressurized tank. This pressure gradient facilitates transport of the fluid through a hose that connects into a receptacle on top of the pressurized tank. Disbursement of the fluid is achieved by using a nozzle that connects to the other end of the hose. This nozzle includes a trigger, which opens a valve to allow flow of the fluid through it and effectively sprays the fluid at the target location. The principle on which the nozzle operates can be calculated using the conservation of mass equation outlined in Fluid Mechanics theory.

EQUATION 2 m = Mass Flow Rate (lbm/s)

ρ = Fluid Density (lbm/ft^3)

A = Cross-Sectional Area (ft^2)

V = Fluid Velocity (ft/s)

The mass flow rate at the inlet equals the mass flow rate at the exit.

EQUATION 3

Combining equations 2 and 3 results in equation 4.

EQUATION 4

It can be seen that exit velocity will be greater than inlet velocity for a nozzle where the outlet area is smaller than the inlet area.

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A SolidWorks model of the pressure vessel can be seen below in Figure 47.

FIGURE 47: SOLIDWORKS MODEL OF PRESSURE VESSEL

Although the pressure vessel is designed to have a capacity of one gallon, this was not meant to be a limitation. The subsystem is designed to incorporate different pressure vessel sizes. This was highlighted by the incorporation of a custom bracket mounting system. This system can be seen in Figure 48 below.

FIGURE 48: CUSTOM BRACKET MOUNTING SYSTEM

The bracket used two large pipe clamps. The tightness of the clamps is adjustable by using the tightening bolt on the far side of the clamp. The bracket could also be easily bolted on to an addition on the chassis of the mobile robotic body. This mounting system could be adjusted to mount any size pressure vessel that would fit in the space encompassed by the bracket wall. It was important to leave this freedom in the design for possible future expansion.

The subsystem needs only one input from the operator. This would be achieved by using a linear actuator. The operator can decide when the fluid needs to be sprayed by looking at the image displayed on the screen by the camera. By flipping a switch, the operator can turn on the linear actuator, which will move a robotic finger in a linear fashion, effectively pulling the trigger on the nozzle. Overall, the subsystem is very inexpensive, coming in at under $300. This subsystem provided a necessary piece of the puzzle for environmental re-establishment.

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PHASE 3 DESIGN

Phase 3 designs focused primarily on the optimization of each subsystem incorporated such that one could build such a subsystem with the right tools and materials. Out of these subsystems, two were built and fabricated with these two being the planting and air purification subsystems. During this phase of design, the primary team focus was on making the ease of manufacturing as simple and efficient as possible.

PLANTING SUBSYSTEM

Previously, a design was created that allowed for fine-tuning of certain aspects of the planting process. These methods led to a similar end product. However, the final Phase 3 design has many small tweaks that, in the end, made a significant impact to the final product.

Ultimately, the largest contributor to the differences in design of Phases 2 and 3 was the decision to build a large majority of the planting subsystem out of wood. This decision, while allowing for an easier and more cost-effective build, had its drawbacks. The largest drawback was the amount of re-designing that had to be done to accommodate making a subsystem out of wood compared to metal. Practically every object had to be made with 200-500 percent thicker walls and objects had to be made to be rectangular in form instead of cylindrical and circular.

FIGURE 49: SOLIDWORKS MODEL OF INITIAL PHASE

3 DESIGN

FIGURE 50: SOLIDWORKS CUTOUT MODEL OF THE

FINAL PHASE 3 DESIGN

In the end, the model shown in Figure 50 allowed for a lower total mass of the system, a larger carrying capacity, and in-all a much more cost-effective solution to the problem that was initially presented. With such a design, one could order and build their own planting mechanism which in-effect could create an open source planting solution for farmers and consumers alike. The design of the hopper was taken from Figure 49. The design the hopper was optimized such that the angle that the seed rolled down in the lower tube shown in Figure 50 was increased, which decreased the chances of clogging of seeds in the lower tube. Creating the hopper out of wood also allowed for simple mounting of motors, bolts, washers and screws that produced a much easier assembly that most any person could perform.

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FIGURE 51: SOLIDWORKS CUTOUT MODEL OF THE

FINAL PHASE 3 DESIGN

FIGURE 52: (LEFT) SOLIDWORKS MODEL OF THE

DRILL INTERIOR

Another substantial design change occurred in the drilling mechanism and the support that holds the drilling mechanism. As shown in Figure 52, the design of the drill is very similar to the design shown in Phase 2, but the change in material dramatically changed the total size of the drill. This increase in size of the sleeve was largely due to the size of the motor that was used in drill, since proper ventilation was required for the drill motor to not overheat. An interior view of the drill component that was created is shown above in Figure 52, which shows the basic concept of the drill. Such a large motor was needed because of the high amount of torque needed, which required a high amount of electric current. Most motors that were capable of producing our required torques for this project were large and awkward, so supports were inserted into this interior and will serve as the mounting points for the motor. This will be capable of keeping the motor upright and fixed while active.

DATA ACQUISITION SUBSYSTEM

Unlike the planting subsystem, the transition from metal to wood for phase 3 of the data acquisition subsystem was fairly simple. The more complex change in phase 3 of the data acquisition subsystem was the addition of the mechanism to move the sensor to a horizontal position after collecting data. The height of the sensor would have caused an unstable situation as the robot moved across uneven terrain, so it was necessary to be able to store the sensor in a horizontal position while the robot was in motion. A decision was made after phase 2 that the data acquisition subsystem would not be built due to the high cost of the sensor. With this added flexibility in the budget, it was decided that a linear actuator would be the most effective way to move the entire soil sensor mechanism from a vertical to a horizontal position, allowing the robot to move freely. The platform on which the sensor is mounted is pinned so it can rotate freely, giving the linear actuator the ability to rotate the entire assembly 90 degrees. This can be seen in Figure 53 below. The linear actuator is mounted to the robot underneath the platform as shown in Figure 53.

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FIGURE 53: SOLIDWORKS ASSEMBLY OF DAQ SUBSYSTEM

AIR PURIFICATION SUBSYSTEM

The main focus of work within the air purification group has been to design, order and customize parts for our air filtration experiment. The first step in the design process was to design the ductwork around a predetermined filter. The filter is 8 in. by 8 in. and 5.5 in. wide and the filter processes air at a range of 35 to 55 CFM. The ductwork design can be seen below in Figure 54. There are expansion and contraction sections. The first is to expand the cross sectional area in order to accommodate the filter. The contraction section prevents the back flow of air from reaching the filter. There are two straight sections of ductwork. The first section is to allow the flow to become ordinary before passing through the filter. The second straight section is needed to take velocity measurements after the filter. Each of these sections has been drilled as shown to allow an anemometer to be placed in the ductwork. The blower is a DC powered fan capable of delivering 105 CFM.

Pin for rotation of assembly

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FIGURE 54: AIR PURIFICATION DIAGRAM

Figure 54 shows the actual ductwork assembled with the filter. As stated, the DC blower delivers a flow

rate of 105 CFM at 12 VDC while we need a flow rate between 35 and 55 CFM. In order to regulate the fan speed and reduce the flow rate down into the desired range, a circuit that utilizes a potentiometer was designed. Using the airflow vs. amperes curve from the manufacturer as seen in Figure 56 we determined we needed 0.8 Ohms to 1.4 Ohms of resistance to achieve our desired flow rate. Using a 5 Ohm potentiometer, we were able to easily control the speed of the fan. The circuit design can be seen in Figure 55 below.

FIGURE 55: CURRENT REGULATION CIRCUIT SCHEMATIC

FIGURE 56: (LEFT) AIR FLOW RATE

VS. CURRENT INTO THE FAN.

SUGGESTIONS FOR IMPROVEMENT

For anyone interested in continuing the project, there are a few suggestions that our group can make. Our primary focus has been on the planting, data acquisition, and air purification subsystems; so while improvements for the design of those subsystems can be made, other systems should be focused on to give the project more versatility when it comes to being able to clean up environmental disasters. Possibilities for this include the other subsystems that we began but were unable to finish due to time constraints, such as oil cleanup or herbicide sprayers. A basic design

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and idea for each is available in the design sections of the report, but they would need to be improved upon before they can be put into use.

While the data acquisition system has been extensively researched and designed, actual construction was decided against due to time constraints. Construction of that subsystem would be something that anyone interested in the project should make a priority of finishing if they are interested in completing the project, as a data acquisition system is necessary for obtaining the information needed to know when to run the subsystems. It is likely that data needed to analyze a great enough range for all of the subsystems would require further research and sensing devices, so more work would need to be done on the system to make it viable for all ranges of use. Another possible issue with the data acquisition system is the lack of a camera whose sole focus is on the ground where the robot will be utilizing the planting mechanism. For more precise control of that mechanism, it might be a good idea to consider multiple cameras that would focus on more specific aspects of the robot’s utilities.

One of the most important parts of continuing or completing this project is the incorporation of the subsystems into a mobile frame. While we did some initial work on the various parts of the mobile robot, that was abandoned fairly early into the project due to time and cost constraints. There is research in the phase 1 design section that will make the construction, purchase, or combination of both an easier task, but it is not complete and would require more work in order to be completed.

CONCLUSIONS

Throughout the process of this semesters senior design capstone, our whole team has learned the value of the design cycle and how important the proper integration of this cycle is with engineering design projects. There have been many times throughout this semester when designs needed to be rapidly changed or altered, which required a high amount of patience and resolve. These situations are not unlike those that many engineers encounter during the design process in their real jobs. This class has helped to prepare us all for the challenges that we will face as engineers trying to solve the problems that the world faces today, and has helped us all gain communication skills that are necessary for such projects to come to life.

The ideas and concepts that we, as a team, have created throughout this year have shown us the power that all of our ideas have, and the possibilities that await us after graduation. If we study only in one aspect of a project, we will never understand the limitations and considerations of the other facets of the project. We have experienced this throughout the entire capstone process. We would design a component of the subsystem, only to realize that we would not be able to actually build it. Whether the reason is the newly designed component would not integrate with the rest of the project, or the stress analysis proved the new design too weak, or even having to scrap a design due to monetary reasons. All of these experiences influence the direction the project takes, as well as provides us with a better understanding of how things would actually happen in a professional work environment. With a recent increase in the use of sensors, control systems, and robotics, a design like the EnviRobot is inevitable. In this age, Robots are capable of entering harsh environments, recording and directing data back to a supervisor, and rejuvenating an environment.

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This technology could be applied to civilian, industrial, and government jobs that require such data and work to be performed.