SREE VIDYANIKETHAN ENGINEERING COLLEGENATIONAL LEVEL PAPER PRESENTATION

ONROBOTICS

“MILLIBOTS”Small Distributed Robots for Surveillance and Mapping

Presented

By

B.V.K MOHAN K.B SUNIL04121A1054, 04121A1005,III B.Tech, E.I.E. III B.Tech, E.I.E.bvkmohan_bala@yahoo.co.in su143s@yahoo.com

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ABSTRACT

“If knowledge can create problems, it is not through ignorance that we can solve them. “

- ISAAC ASIMOV

In recent years there has been an increasing interestin distributed robotic systems. In such a system, a task is not completed by a single robot but instead by a team of collaborating robots. Team members may exchange sensor information, may help each other to scale obstacles, or may collaborate to manipulate heavy objects.

This paper describes the design of a team of centimeter scale robots that collaborate to map and explore unknown environments. The robots, called "CMU Millibots", are configured from modular components that include sonar and IR sensors, camera, communication, computation, and mobility modules. Although these small robots have limited capabilities as individuals, as a collaborative team they can be used for Mapping and surveillance applications.

In this context we are going to present the Technology involved in this project of “Millibots”.

K.B SUNIL B.V.K MOHAN04121A1005, 04121A1054,III B.Tech, E.I.E. III B.Tech, E.I.E.Su143s@yahoo.com bvkmohan_bala @yahoo.co.in

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THREE LAWS OF ROBOTS

First Law –

A robot may not injure a human being.

Second Law –

A robot must obey the orders given to it by human beings. Except where such orders would conflict with the first law.

Third Law –

A robot must protect its own existence as long as such protection does not conflict with the first or second law.

- ISAAC ASIMOV

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1. INTRODUCTION

A team of robots has distinct advantages over single rbots with respect to actuation as well as sensing. When manipulating or carrying large objects, the load can be distributed over several robots so that each robot can be built much smaller, lighter, and less expensive. As for sensing, a team of robots can perceive its environment from multiple disparate viewpoints. Even though a single robot may be equipped with different sensing modes, it can only observe the environment from a single viewpoint. For tasks such as mapping and exploration, this increased utility equates to increased coverage and speed. Exploration and mapping can occur at multiple fronts simultaneously precluding the necessity for a single robot to travel to multiple waypoints. By coordinating as a team, a group of physically distinct entities can act as a single logical entity.

Small robots have a distinct advantage over their larger counterparts in the exploration and surveillance arenas. In addition to being highly suitable for covert operations they have the unique ability to access areas unreachable to larger robots

Figure 1: The CMU Millibots

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2. SYSTEM DESIGN

To explore the utility of distributed sensor collaboration, we have developed a team of small robots, called Millibots (Figure 1) [3]. These robots are constructed at the 5-10 cm scale allowing them increased accessibility to tight or cluttered spaces.

Distributed robotic systems require a new design philosophy. Traditional robots are designed with a broad array of capabilities (sensing, actuation, communication and computation), but redundant subsystems must be added toavoid single point failure. This results in a robot that is larger, more complex and more expensive.

Millibots are able to distribute processing and sensing over a collection of robots by exploiting the nature of modularity and specialization. By equipping a Millibot with only those sensors needed for the particular set of sub-tasks, the robot is able to optimize on resources such as size, computational complexity and power. This optimization results in less expensive robots that are easier to maintain and debug.

Reducing the cost of individual units allows more robots to be built with the same resources. Adding multiple robots with the same abilities increases the effectiveness of the group while adding a degree of redundancy and consequently increasing fault tolerance. If a single robot fails, only limited capabilities are lost and the team can still continue the task with remaining robots.

Figure 2: Modular Design

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Figure 2 is an example of some of the modules currently available for the construction of a Millibot. A mobility module is selected according to the task. One mobility module may be well suited for operation on coarse terrain while another is more effective on a flat, smooth surface. A processing module is then selected based on the computation necessary for operation (center). Powerful processors consume significantly more power than smaller processors and may be more than the robot requires for a given task. By selecting the minimum processing necessary for operation, the robot can support a greater sensor load or extend the operating time of the robot. On the other hand, a different robot may be built with greater processing capability but at the expense of sensing. A team design is able to exploit the features of both.

Finally a sensing module(s) is selected based on the particular mission. For example, some robots may use sonar sensors allowing them to build sensor maps, while others are support object identification with a camera. By supporting modularity, any sensor module that conforms to the proper interface can be integrated into a given Millibot. These platforms may include a variety of sensors including sound recorders, ranging sensors, proximity detectors, chemical sniffers, magnetic field detectors, or radiation monitors.

3. MODULES USED IN MILLIBOTS

3.1 The Beacon Transceiver

3.2 Short Range Sonar

3.3 Long Range Sonar

3.4 Infrared Ranging

3.5 Scanning Pyro

3.6 Camera Module

3.7 Main Processor

3.8 The Motor Boat

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3.1 The Beacon Transceiver

The Beacon Transceiver is a key element to the Millibots for establishing and maintaining position. Every robot has some form of transceiver that allows it to get a range to other robots in the group. Here is the reflector that allows the center detector to receive signals from all the way around the robot.

Figure 3: Beacon Transceiver

3.2 Short Range Sonar

This Short Range Sonar module provide sonar range information in a ring about the robot up to a range of about 50 cm. The data from this array is used to identify obstacles and build maps.

Figure 4: Short Range Sonar

3.3 Long Range Sonar

This Long Range Sonar module provide sonar range information in a ring about the robot up to a range of about 1.2m. However, it has a minimum range of about 4 inches meaning it is more effective in open areas.

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Figure 5: Long Range Module

3.4 Infrared Ranging

This Infrared Ranging module has two narrow field infrared ranging modules mounted on either side and 3 short range sonars mounted in front. These ir modules fire much quicker than the sonar and can be operated as the robot is moving. It is idea for rapid wall following.

Figure 6: Infrared Ranging

3.5 Scanning Pyro

This is a scanning pyro detector. It detects changes in the heat profile across the scan. It is sensitive enough to pick up thermal energy from a non-moving person. It is also equipped with a temperature sensor.

Figure 5: Scanning Pyro

3.6 Camera Module

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This Camera Module provides a video camera and transmitter to the team. The camera is switched on for short periods of time when needed to identify objects or clearings around the robot.

Firure 6: Camera Module

3.7 Main Processor

This Main Processor Module provides the processing for the robot. It collects and processes information from the sensors and communicates data and commands via RF to the team leader.

Figure 7: Main Processor

3.8 The Motor Boat

This Motor Boat module provides the modility and power for the robot. Multiple modules are available. This one uses thick tires to allow it to run well on carpeted surfaces.

Figure 8: Motor Boat

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4. CLASSIFICATION OF MILLIBOTS

Millibots are classified according to the task to be performed. Mainly they are classified into seven types as follows.

4.1 The Long Range Sonar Robot

4.2 The Short Range Sonar Robot

4.3 The Dirrs Robot

4.4 The Pyro Robot

4.5 The BW Camera Robot

4.6 The Color Camera Robot

4.7 The Laser Robot

4.1 The long Range Sonar Robot

This robot houses a custom 8-element sonar array just like the short range module except it has some major improvements. This robot can detect obstacles as far away as 1 m with an improvement of speed of about 8x. Like most of the team, this robot has the ability to also perform robot to robot ranging allowing it to localize.

Figure 9: Long Range Sonar Robot

4.2 The Short Range Sonar Robot

This robot houses a custom 8-element sonar array that is used to detect obstacles and produce maps. It can detect obstacles as far away as 50cm and as close as 0. This robot is also able to coordinate with other

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robots to perform robot to robot ranging. This feature is key in allowing the team to maintian knowledge of robot positions as the team moves.

Figure 10: Short Range Sonar Robot

4.3 The Dirrs Robot

The Dirrs robot (Digital Infrared Ranging Sensor). This robot houses 2 Dirrs modules on either side and is used primarily to allow the robot to quickly follow walls and search for openings. The use of the infrared allows it to move much quicker than some of the other robots. In addition, this robot has 3 sonar elements in the front to help it avoid obstacles.

Figure 11: Dirrs Robot

4.4 The Pyro Robot

The Pyro robot houses a sweeping pyro detector on the front that allows the robot to sweep the area for heat sources. The sensor is sensitive enough to detect stationary warm bodies

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Figure 12: Pyro Robot

4.5 The BW Camera Robot

The BW Camera robot. This robot houses a small B/W camera used primarilty to classify postential interesting object found by other robots. The robot also carries a video transmitter which allows the video to be piped off-board for real time viewing. The robot can turn the camera on and off allowing the team to utilize several cameras during the same mission using the same channel.

Figure 13: BW Camera Robot

4.6 The Colour Camera Robot

The Color Camera robot. This robot houses a small Color camera Sometimes color can convey more information than black and white. Ironically, this camera needs significantly less power than the BW.

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Figure 14: Colour Camera Robot

4.7 The Laser Robot

The Laser Robot We added a laser pointer and spinning mirror to the front of this robot that allows us to do some video range finding.

Figure 15: Laser Robot

5. ARCHITECTURE

The architecture of this environment is set up to support multiple-team, multiple-robot operations. The teams may or may not be aware of each other. Each team shares the same environment. Its architectureMainly consists of TEAM MANAGER, TEAM LEADER, ROBOT.

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Figure 16: Architecture of Millibots

Team Manager - The primary purpose of this class is to hold references to the entities that have interaction with the environment.This includes a reference to each of the team leaders, all of the robots and all of the global objects. There are two purposes for holding independent references to all the entities. The first is to allow the team manager a handle to draw all the appropriate images on the world map. The second is to privide the simulator with references to all the potential objects that could produce a collision or reflection. The team leader and robot classes do not have access to this class.

Team Leader - This is a virtual class that represents an individual team of robots. Each team leader contains references to the robots of its group. Each team is threaded and can be treated as an independent process.

Robot - Like the team leader, each robot class is threaded as well and acts as an independent process. The robot can run independently or tasked via messages from the team leader.

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