AC2012-4520: DEVELOPMENTOFADESIGNTHEORYANDMETHOD- … · the concept Computer-Aided Engineering (CAE). For instance, solidThinking is a tool that helps us in the conceptual design

AC 2012-4520: DEVELOPMENT OF A DESIGN THEORY AND METHOD-OLOGY MODEL FOR MECHATRONICS

Dr. Noe Vargas Hernandez, University of Texas, El Paso

Noe Vargas Hernandez researches creativity and innovation in engineering design. He studies ideationmethods, journaling, smartpens, and other methods and technology to aid designers improve their creativ-ity levels. He also applies his research to the design of rehabilitation devices (in which he has variouspatents under process) and design for sustainability.

Jose Gabriel Davila, University of Texas, El PasoProf. Jorge Garza-Ulloa, University of Texas, El Paso

Jorge Garza-Ulloa is a Ph.D. candidate in biomedical engineering and electrical engineering at Univer-sity of Texas, El Paso, El Paso, Texas. He has master’s degrees from the University of Massachusettsat Amherst, Mass., and Temple University (applied mathematics), and a B.S. in electronics engineeringand communications from the Institute Technological of Monterrey at Monterrey Nuevo Leon, Mexico.He has work experience in the Electrical Engineering Department as a Teaching Assistant, University ofTexas at El Paso, El Paso, Texas; Computec and Computech of El Paso; Chairman of company/Consultantfor external companies to develop new custom applications to improve productions: Delphi, RCA, John-son & Johnson, etc.; design of test equipment for manufacturing process; CAD/CAM mechanical Design,workflow, digital prototyping; developer of ECE special equipment for productivity improvement; andteaching special training for manufacturing companies in the USA and Mexico. He has specialized train-ing in databases connected to new ECE applications for manufacturing; developer of ECE special equip-ment for productivity improvement; CAD/CAM mechanical design, workflow, and digital prototyping;simulation of manufacturing process; project management; and professor and research at Insituto Tecno-logico de Juarez, Chih. and Graduate Center. Awards include: Schellenger Research Scholarship awardedby the Electrical Engineering Department, the University of Texas, El Paso, Fall 2011; TA ScholarshipAwarded by the Electrical Engineering Department, the University of Texas, El Paso; CONACYT GrantsAdviser for Universities and Technological at Mexico Honor; Autodesk User group at Juarez, Chih. Mex-ico, Honor; ITCJ Instituto Tecnolgico de Cd. Juarez. Chih. Mexico, Best Professor Award ITCJ GraduateCenter.; and best research award on Technology & Automated Computer.

Mr. Pablo Rangel, University of Texas, El PasoMr. Julio Adrian Torres

c©American Society for Engineering Education, 2012

Development of a Design Theory & Methodology Model

for Mechatronics

ABSTRACT

When surveying Mechatronics textbooks, it is surprising to find that the contents on design of

mechatronic devices are limited. Some textbooks make the generic recommendation of designing

“concurrently”; others assert that an open communication channel must be always maintained.

Other textbooks go as far as presenting a design process model that conceptually shows the

interaction between disciplines at a high level of abstraction. Nevertheless, mechatronic devices

are being designed every day; this is important to acknowledge since we could borrow from

practical experiences to create a descriptive model while complementing it with design

engineering theories and methodologies for a prescriptive model, obtaining at the end a hybrid

design theory and methodology model for mechatronics. This paper presents the process of

developing a Design Theory and Methodology (DTM) model for mechatronics/biomechatronics,

general enough to be applied to various projects in a senior design course, for example, but

specific enough that provides each mechatronics project with strategy (design process) and tools

(design theories and methodologies) to complete the task. The proposed model is derived from

mechatronics examples, engineering design theory, and our own experience designing a

biomechatronic prototype to measure the dynamics (balance and posture) of the human body for

locomotion rehabilitation purposes. One of the key features of the model is its emphasis on

training and communication among disciplines and subsystems. Another key feature is the

“pulsating” representation where at each “pulse” the different disciplines or subsystems “open”

to work independently and then “close” to integrate their findings. The model will be made

available for use in senior design courses as well as for prototyping in the author’s research area

of biomechatronics.

1 Introduction

The objective of this paper is to present an initial model for the multidisciplinary interaction of

disciplines in mechatronics design. The objective of the model is to allow engineers to create a

strategy for the interactions among disciplines.

“Mechatronics” refers to a new engineering field, which started in Japan in the early 70’s and has

continued its development since then. Mechatronics has been defined as the application of

complex decision making to the operation of physical systems 1. This is achieved through a

multidisciplinary engineering system design. In other words, mechatronics can also be defined as

the synergistic integration of mechanical engineering, electrical and electronic engineering,

computer science and control engineering.

The importance of mechatronics relies mainly in its applications. This modern engineering field

produces many new products and gives us important techniques to increase the efficiency of

products that already exist and that we use in our daily life. Mechatronic systems are almost

everywhere we look. All around us, we can find mechatronic products. Mechatronics includes a

wide range of application areas from power systems to transportation to telecommunications and

biomedical devices. There is not doubt about the significance that mechatronics has in society,

since it has the potential to improve the quality of life of many people, for example when applied

to rehabilitation devices.

It is worth mentioning that, in the mechatronic process, human resources such as engineers,

technicians, and designers from various disciplines are very important. Mechatronics engineers

not only must have extensive knowledge in their specialized fields, it is also essential they know

how to work together and concurrently 2. Mechatronics is not only the integration of

functionality and the combination of different components, but also it is the design plan,

integration and production process. The added value of the disciplines produces a synergetic

effect that allows innovative functionality and the control of complex systems. Mechatronics

emphasize the importance of improving the quality in the communication between different

disciplines even before the project starts. However, one of the most important issues in the

mechatronic processes the implement of this concurrency. The authors believe that there is a

need in mechatronics for a systems design strategy.

2 Background

2.1 Mechatronics

As mentioned before, mechatronics is the multidisciplinary field that synergistically integrates

mechanical engineering, electrical and electronic engineering, computer science and control

engineering 3 Figure 1. These fields are the mechatronics key elements and each of them

contributes with a very specific function within the system.

Figure 1 Mechatronics Key Elements 3

Mechanical

Engineering

Electrical

Engineering

Computer

Science

Control

Engineering

Mechatronics

Mechanical engineering is a discipline that adds the physical structure and movable parts of the

complete mechatronic system. That is done by the application of physical principles and it

requires analysis at different levels such as materials selection, design and manufacturing. In this

field, the engineers deal with several subfields, within we can find: statics, dynamics, kinematics,

thermodynamics, fluid mechanics, energy transfer, material technology. Engineers also need to

work with different types of analysis: static analysis, dynamic analysis, finite element analysis

(FEA), etc. Currently, there is a wide range of tools and techniques that helps mechanical

engineers to perform the different analysis through the design process. In the tools, we can find

the concept Computer-Aided Engineering (CAE). For instance, solidThinking is a tool that helps

us in the conceptual design. It allows visualizing, exploring and evaluating different concepts.

Inside CAE there is Computer-Aided Design (CAD), which is very used to model mechanical

parts or systems. Although, now CAE has more flexibility to model elements not only of a single

domain. NX from Siemens and SolidWorks are two of the most representative CAD software.

This software also allows us to perform the analysis mentioned before. ANSYS and NASTRAN

are used to do the FEA. A very helpful technique in the design is Product Life-Cycle

Management (PLM) that manages the entire lifecycle of a product from its concept, to its design,

manufacture, service and disposal.

As the mechanical engineering contributes with the “body” (structure) to the mechatronic

system, electrical engineering, contributes with the power source of the system by means of the

application of electricity, electronics and electromagnetism. There are different subareas that the

electrical engineer needs to understand: power, electronics, signal processing,

telecommunications and control systems. Even control systems could be found in the

background of an electrical engineer, in mechatronics, it takes a very important role and there are

specific tools to work with it. This are also have a wide range of tools. Multisim from National

Intstruments, that helps to analyze electric circuits behavior. It is very used because of its

intuitive environment and easy-to-use software platform. Multism also has printed circuit board

(PCB) layout software.

Computer science performs the processing of data and functions of the mechatronic system,

using algorithms that create, describe, transform information and generate an efficient data flow

between the system elements. Computer science, as the mentioned engineering fields, has many

subareas. Basically, what mechatronics takes from it are the algorithms of the main programming

of the system. To do that, there are several programming languages to solve specific

computational problems, and also human-computer interaction, doing Human-Machine

Interfaces (HMI) that are increasingly more accessible to humans. LABVIEW from National

Instruments is a graphical programming environment used in mechatronic systems development.

Some of its functions are: measurement, test, and control systems.

Control engineering or control theory is another discipline inside mechatronics. It applies control

theory to design intelligent systems. However, it is necessary to have strong basis on the other

fields (i. e., mechanical and electrical engineering), since control theory deals with the

identification and modeling of dynamic systems. We also can find that control theory has several

subfields and they depend of the level of intelligence or robustness that the system requires. The

principal subfields of control are: classic control, modern control, digital control, logic control,

adaptive control, intelligent control, optimal control, robust control and stochastic control. The

common fact is that they are based on the control theory principle: they use of sensors to

measure the output performance of a specific variable that is being controlled and those

measurements can be used as feedback, this feedback is taken by the controller, the controller

makes a decision and then it makes a manipulations through the actuators that make regulations

toward the desired system performance. Control theory is based on mathematical modeling of

systems of a diverse range. The most used tool is MATLAB / SIMULINK from MathWorks that

is a numerical computing environment and fourth-generation programming language. It allows

solving matrices, plotting of functions, data processing and manipulation, implementation of

algorithms, creation of user interfaces.

After understanding the key elements of mechatronics, we also need to be aware that there is not

only one definition of mechatronics in the literature and these key elements may vary from one

author to another. However almost all those definitions are around the combination of

mechanical engineering, electronic engineering, computer science and control engineering.

Figure 2 shows a different definition representation of the key elements in mechatronics 3. In this

case, the key element control engineering is encapsulated together with simulation and modeling,

and optimization; in information systems. As in the case of the different definitions, there are

different attempts to capture the mechatronic design process 4 Figure 3. Regrettably, there are not

strategies or tool that helps to do the phase of concurrent engineering in mechatronics.

Figure 2 Alternative representation of Mechatronics Key Elements 3

Actuators

+ =

Control

Theory

Simulation

and Modeling

Optimization

Mechanical

Systems

Mechatronics Electrical

Systems

Computer

Science

Electromechanical Real-Time Interfacing

Sensors A/D

D/A

Information Systems

Figure 3 Design procedure for mechatronic systems (Isermann, 2003)

2.2 Design

Authors like Clive Dym and Patrick Little 5 state that engineering design is: “a systematic,

intelligent process in which designers generate, evaluate and specify designs for devices, systems

or process whose form(s) and function(s) achieve clients objectives and user’s needs while

satisfying a specified set of constraints.” “Designers are thus expected to describe the shape and

configuration of a device (its organization), how that device does what it was intended to do (its

function) and how the device (its inner environment) works (interfaces) within its operating

(outer) environment.”

The user’s need could be defined as the circumstances that have the next components and

characteristics according to G. Pahl and W. Beitz 6:

System definition

Requirements

definition

Mechanical and

electrical engineering

Electronic engineering Information and

control engineering

Operating engineering

Integration of components

(hardware)

Integration by information

(software)

Generation of

synergetic effects

Reliability and

safety

Manufacturing

engineering

Human machine

interface design

Information

processing and

software design

Electronic hardware

design

Process design

Traditional

engineering

Integrated (concurrent)

engineering

Mechatronic

system

Components:

• An undesirable initial state, i.e. the existence of an unsatisfactory situation.

• A desirable goal state, i.e. the realization of a satisfactory situation.

• Obstacles that prevent a transformation from the undesirable initial state to the desirable

goal state at a particular point in time.

Characteristics:

• Complexity: many components are involved and these components, through links of

different strength, influence each other.

• Uncertainty: not all requirements are known; not all criteria are established; the effect of

a partial solution on the overall solution or on other partial solutions is not fully

understood, or only emerges gradually. The difficulties become more pronounced if the

characteristics of the problem area change with time.

It is also important to state that according to Dym and Little 5:

• Design problems are ill structured because their solutions cannot normally be found by

applying mathematical formulas or algorithms in a routine or structured way.

• Design problems are open-ended because they typically have several acceptable

solutions.

Although there are various design process models, they all agree on a systematic strategy that

varies in the number of steps but could be condensed in to four major phases:

Planning: the process of clarifying the task based on the next tools:

• Design Specifications: is the key document with the information obtained by the

customer.

• Design Requirements: is the list of technical details that reflect the Design Specifications.

Conceptual Design: “Is the part of the design process where the basic solution is laid down

through the elaboration of a solution principle.” And its main steps are:

• Identifying Functions: “Actions that the designed device or system is supposed to take or

meant to do” (Dym and Little).

• Generating Design Alternatives: Ideation Methods

• Combining Design Alternatives: Using Morphological Charts.

• Evaluating and Selecting Alternatives: Involving Decision Making.

Embodiment Design: to identify the preliminary layouts and form designs.

Detail Design: to optimize and communicate the final design.

Since there are dozens of design tools we will just mention some of their classifications that were

collected from literature survey from several authors:

Engineering Design Tools Classifications:

• Systemic (Pahl & Beitz 6, Otto

7)

• Integrative (Cross 8; Ullman

9)

• Prescriptive (Pahl & Beitz 6)

• Descriptive (Pahl & Beitz 6)

• Driven by Problem/Solution (Cross 8)

• Driven by Information/Knowledge (Cross 8)

• Rational (Altshuller and Shulak 10

)

• Creative (Lumsdaine et al. 11

)

• Adaptive/Innovative (Lopez-Mesa 12

)

• Convergent/Divergent (Lopez-Mesa 12

)

2.3 Mechatronics as a Systems Engineering Model

Systems Engineering (SE) consists of the application of science to design a system and it starts

from the system-level design, to subsystem design, and down to the component level. This

approach is cost and time effective, and robust to uncertain environments. Systems engineering

approaches are defined by the definition of the system requirements, detail technological

components, top-down holistic attributes, product/system life-cycle understanding and the

importance of interdisciplinary teaming. Some of its key features are that it define system

requirements and relate these requirements to specific design criteria and the follow-on analysis

effort. It also focuses on the interdisciplinary or team approaches to ensure all design objectives

are addressed.

Adding SE concepts into the Mechatronics model implies the creation of a design model that can

be seen in a holistic view as a single system by its different disciplines. It also implies the

creation of top level requirements that will divide tasks after their proper definition. Then, a

functional analysis and allocation of the requirements will allow having a system come back

together to synthesize the design. All of these processes are analyzed and controlled in parallel.

In the end, the SE Process Figure 4 is a well organized way of keeping track of the design

process and it can encounter any issues within the system in an organized and efficient manner.

The SE full process can be observed in the diagram below:

Figure 4 The Systems Engineering Process

Within the Mechatronics industry a highly used model to come upon the conception of a system/

product is the V Process Model Figure

multidisciplinary interaction that oscillates between specialization and multidisc

collaboration depending on the client changes to the systems requirements, time and the money

been spend. However, its “Integration” area requires constant multidisciplinary collaboration.

This produces a generalized collaboration model that doesn

collaboration guidelines.

Figure

The SE Product Lifecycle Process

System/Product can be realize in a well organized manner. In consists on

Definition of Need, Conceptual Design, Preliminary Design, Detail Design and Development,

Production/Acquisition, Utilization and Support and Phase

Figure

If the design must be seen as system,

Figure 7. In this strategy four concurrently lifecycles are specified. It adds the needed

NN

EE

EE

DD

ACQUISITION PHASE

Conceptual-Preliminary

Design Development

Mechatronics industry a highly used model to come upon the conception of a system/

ess Model Figure 5. This model on its “Decomposition” area creates a

multidisciplinary interaction that oscillates between specialization and multidisciplinary



This produces a generalized collaboration model that doesn’t completely follows a proper set of

Figure 5 The V Process Model

e SE Product Lifecycle Process Figure 6 is another strategy in which the Mechatronic

System/Product can be realize in a well organized manner. In consists on several stages:


Production/Acquisition, Utilization and Support and Phase-out and Disposal.

Figure 6 Product Lifecycle Process

If the design must be seen as system, the Product Lifecycle evolves into the System Lifecycle

In this strategy four concurrently lifecycles are specified. It adds the needed

ACQUISITION PHASE UTILIZATION PHASE

DetailDesign and

Development

Productionand/or

Construction

Product Use, Phaseout, and

Disposal

Mechatronics industry a highly used model to come upon the conception of a system/

This model on its “Decomposition” area creates a

iplinary



’t completely follows a proper set of

is another strategy in which the Mechatronic

several stages:


lves into the System Lifecycle

In this strategy four concurrently lifecycles are specified. It adds the needed

UTILIZATION PHASE

technologies to support time-based competition. It becomes a concurrent engineering attempt to

accomplish work in parallel rather that series.

Figure

3 Proposing a Model for Mechatronics Design

Mechatronic design is limited on strategy. Multiple text books and resources focus on the tools

that bring to the completion of a mechatronic pr

(strategy) make a mechatronics tool become too specific and the system completion can be

jeopardized by the lack of guidelines of how to deal with its multidisciplinary interaction. Within

that scope, it is necessary to approach a better mechatronics multidisciplinary interaction model.

The multidisciplinary mechatronics

and exploration of multiple ideas to reach a successful completion of a mechatronics

system/product. Systems Engineering and Engineering Design contain

strategies that can be applied to create a

Mechatronics provides the specific

define the guidelines of how to address the complexity of a system and its subsystem. Finally,

Design engineering defines the sequence of steps (strategy) and tools (theories, methodologies)

to complete a design (of a subsystem, for a

3.1 State of the Art

The authors haven’t encountered in the literature a model that addressed the issue of strategy in

mechatronics design. Engineering Design offers strategies, but these are single

nature and disregard the interactions in multidisciplinary projects. Systems engineering provides

strategies on how to keep track of a system and its subsystems and components.

based competition. It becomes a concurrent engineering attempt to

k in parallel rather that series.

Figure 7 System Lifecycle Process

Proposing a Model for Mechatronics Design


that bring to the completion of a mechatronic product/system. However, the lack of a plan



ry to approach a better mechatronics multidisciplinary interaction model.

multidisciplinary mechatronics communication process implies convergence, divergence

multiple ideas to reach a successful completion of a mechatronics

roduct. Systems Engineering and Engineering Design contain useful guidelines

that can be applied to create a mechatronics model of interaction.

provides the specific tools for multidisciplinary design. Systems engineering

address the complexity of a system and its subsystem. Finally,


to complete a design (of a subsystem, for a given discipline).


mechatronics design. Engineering Design offers strategies, but these are single-discipline in

teractions in multidisciplinary projects. Systems engineering provides


based competition. It becomes a concurrent engineering attempt to


oduct/system. However, the lack of a plan



ry to approach a better mechatronics multidisciplinary interaction model.

communication process implies convergence, divergence

multiple ideas to reach a successful completion of a mechatronics

guidelines and

. Systems engineering

address the complexity of a system and its subsystem. Finally,



discipline in

teractions in multidisciplinary projects. Systems engineering provides


While identifying multiple design theory and methodology models no one has been more

successful into realizing working mechatronics systems than NASA. The NASA

Program/Project Life Cycle Process Flow Figure 8 is used to develop Complex Aeronautic

systems to simple tools that have dramatically change the route in which humanity relates to

technology. This design model is a detail view of the activities realized during most NASA

project life cycles. This model is divided in ten stages (process flow blocks). These stages

change as the system progresses depending on the different work that must be preformed. The

stages have both a logical and temporal relation. The deeper the stage, the more refine and

mature the system becomes. As the flow of the model progresses the products from the previous

stages become inputs. Then, when moving to a new stage in the process the nature of the

technical activities become more shifted. The proper progress from one stage into another is

control by gates.

A synthesized version can be seen on the NASA ESMD Capstone Design by The Ben Shima 13

.

The process is the same and is highly used for senior design projects. The propose model that is

been seek is something efficient and reliable as the NASA model but more practical and focus on

the area of Mechatronics engineering.

Figure 8 Segment of The NASA Program/Project Life Cycle Process Flow (NASA) 14

3.2 Requirements for the Model

The proposed model of multidisciplinary interaction for Mechatronics depends on a series of

pulses as shown in Figure 9 that define the moments when each one of the Mechatronics

discipline must interact. The ways these interactions are defined are the exploration, convergence

and divergence moments within the multidisciplinary collaboration. These pulses become

multidimensional by adding Mechatronics tools, Design engineering and Systems engineering

strategies and tools.

Figure 9 The Mechatronics Multidisciplinary C

The proposed model takes into consideration the strategies and tools from systems engineering,

engineering design and mechatronics as shown in Figure 10. An example design process for the

design of a Stewart platform for Biomechatronics application is used to obtain observat

improve the model.

Figure

4 Case Study: Stewart Platform Design

A Stewart Platform is a mechanical device that consists of a bottom and top base, with three

pairs of actuators or jacks that enable an object to move in a 3D fashion. These types of

Platforms have different applications such as machine tool technology, crane technology, and

aircraft simulations, among others. These applications require the integration of three different

domains to be able to control the Platform: mechanical, electronic

together define a mechatronical device

Mechatronics Multidisciplinary Collaboration Pulse Model

takes into consideration the strategies and tools from systems engineering,


design of a Stewart platform for Biomechatronics application is used to obtain observat

Figure 10 Mechatronics Model influences

Case Study: Stewart Platform Design



applications such as machine tool technology, crane technology, and


domains to be able to control the Platform: mechanical, electronics and programming, which

device.

ollaboration Pulse Model

takes into consideration the strategies and tools from systems engineering,


design of a Stewart platform for Biomechatronics application is used to obtain observation and



applications such as machine tool technology, crane technology, and


and programming, which

The first step of the project was to gather a team of professors and students of each domain area.

At the “launch” meeting the main objectives and requirements of the project were presented to

all the members. Later, each domain team, continued working independently on their own

domain (mechanical, electronics and programming). After some time, each of the teams

approached the project manager with different questions and requirements that were not clarified

or defined in the “launch” meeting, generating the need for a second “all domains” meeting were

those questions and requirements were exchanged among the different “domain teams”,

clarifying their inquiries and generating tasks for each of the teams. Time after those tasks were

completed more questions from each team arose again, creating a need for a third “all domains”

meeting. By this time, the manager and the teams realized the need for recurrent and scheduled

meetings with all the domain teams present, as a tool to develop the project more efficiently by

focusing on the inquires generated by each team before the meeting and the tasks to be

accomplished by each team before the next meeting, and so on until successful construction of

the final assembly. This particular section will resume the details of its components and how they

play a specific role in the overall design function.

The electronic device consists of 6 Linear Actuator Controllers (LAC’s). The LAC is a stand-

alone closed-loop control board specifically designed for linear actuators. The LAC controls the

position of a single actuator, what simplifies the design. This device allows different ways of

control, giving great flexibility in the programming.

The programming control consists of basically two parts. The first one is an Arduino MEGA

2560 electronic prototyping board (microcontroller), which controls the 6 LAC’s, giving the

input signals to them. The second part of programming is the user interface, which is

programmed in C# and makes the communication with the microcontroller.

The mechanical device, as shown in Figure 11, consists of two bases (upper and lower) held

between 6 actuators connected through mechanical joints that allow a 6 Degrees of Freedom

(DOF) movement which permit the upper base to tilt or pivot up to a range of 20 degrees with

respect to its lower base. While some of the components were already on the market, some others

had to be manufactured in order to meet design criteria.

A very important parameter in the design of the two platforms was the position of the supports

for the actuators. The position of these supports changes the orientation angle of the actuator and

thus changes the forces involved. This position also has major effects of the acceleration,

velocity and stroke needed from the actuator.

Other very important parameter is the material used for the two platforms, since their weight and

strength depend on the material they are made out of. It was decided that Aluminum 2024-T3

would be used since it is very strong and light.

The upper supports that are attached to the top of the platform had to be manufactured since they

play a very important role in the assembly. The lateral faces of the couple are set so that the ball

joint is centred when the platform is at a zero position (completely level to the floor and with the

actuators at mid-stroke). All other parameters for the support are made to comply with this

requirement. The material for this couple was chosen to be steel, since weight is not a major

concern due to its small size and since the couple will include several threaded holes.

Since, the client requirements for the platform was 20° of rotation in every direction, a ball joint

attached at the upper platforms was required, such that could provide at least +- 10° of rotation.

The upper actuator couple, which serves as a connection means between the ball joint and the

upper portion of the actuator, was created in order to reduce the length required for the actuator,

ball joint and other components that needed to be integrated into the platform in order to give it

movement. It incorporates the ball joint screw holes and it can be screwed directly into the

actuator piston shaft. Since this specific couple is not on the market, it was designed considering

important parameters in order to ensure the integrity and stability of the device. Some of the

previously mentioned parameters include shear and bending force calculations during tension,

and a compression toughness test, both incorporating the use of Finite Element Analysis (FEA)

and hand calculations. Material selection was also an important parameter in the calculations and

design process, with the material selected being steel, for the same reasons considered for the

uppermost couple.

One of the most important parts of the platform is the linear actuator. Due to its precision and

strength characteristics a “Ball Screw” actuator was selected. This mechanism works similarly to

a worm gear, when the actuator nut rotates, the screw shaft translates linearly. This type of

mechanism was selected because if the electrical power goes down for any reason, the actuator

will stay in position.

The lower joint, which unites the actuator to the bottom base, must provide two degrees of

freedom. This component had to be designed due to lack of market availability of the joint as a

whole by assembling two components, a hinge joint with a shaft mounted on a flanged bearing.

The hinged joint was made possible by a shaft with a slip yoke end and the bearing by a standard

duty ball bearing with a flanged plate fixed by screws to the bottom platform. It is important to

note that a ball joint was not used for the lower joint because it would allow the actuator to rotate

on its own axis indefinitely, which is not desired due to wiring and placement of the motor

housing.

Figure 11 Constructed Stewart Platform for the Case Study

5 Model Development

5.1 Conceptual Model

From an abstract point of view, Systems, Design and Mechatronics each provide a different

perspective of the design of a mechatronics system. As pictured in Figure 12, Design provides

the sequence of steps to realize a sub-system, Systems provides the strategy for analysis and

integration of components and subsystems, and Mechatronics provides the tools used to combine

disciplines (i.e. mechanical, electrical, and controls).

Figure 12 The Mechatronics Design Cube

5.2 Integrated Model

Systems engineering can provide the perspective on how to divide and then integrate a complex

system into subsystems. Once a subsystem is identified, it can be designed by following a

DESIGN

(sequence)

SYSTEMS

(integration)

MECHATRONICS

(tools)

systematic design process such as the one defined by Pahl and Beitz (2005). If multiple

disciplines are involved, the systematic design process can be followed by each discipline, as

shown in Figure 13 for the case of a mechatronics subsystem. The field of mechatronics provides

a series of tools and techniques to aid in the integration of different disciplines. Systems

Engineering and Design Engineering provide Strategies and Tools, as shown in Table 1. The

authors have noticed that Mechatronics provides mostly tools, and not necessarily a strategy for

the planning the process. This is evident when reviewing the literature, traditional textbooks in

mechatronics make a brief mention of design before addressing the tools and techniques of

mechatronics tasks.

Acknowledging that Systems Engineering and Design Engineering provide a variety of strategies

and tools, and that Mechatronics provides mostly tools, the proposed model in this paper focuses

on the strategies in Mechatronics. It is the goal that this model to take advantage of existing

strategies and tools in Systems Engineering and Design Engineering, for this reason, the

proposed model doesn’t modify these, it only adds a suggested mecahtronics strategy

complementary to Systems, Design and Mechatronics.

Table 1. Strategies and Tools for Systems, Design and Mechatronics.

Strategy Tools

Systems V-Model Serial diagram, logical

diagram, decomposition

diagram, trade off analysis,

risk cube, ICOM diagram,

functional allocation,

requirement allocation

Design Systematic

Approach

Design Theory and

Methodology

Mechatronics Pulses Bong Graphs, Multi-

physics

Figure 13 The complete Systems, Design and Mechatronics process

The proposed model, as shown in Figure 14, consists of “pulses”. A typical pulse starts with all

disciplines working together to agree on individual objectives and interfacing constraints. Then,

each discipline works independently based on these agreements. While working independently,

intercommunication is not only possible, but encouraged. The independent work from each

discipline must be integrated, and although agreements and interfacing constraints were in place,

integration is not trivial since various technical issues arise in this process. The pulse also

considers iterations for one or more of the disciplines to refine their work. Once the pulse is

completed, a new pulse is planned to continue with the design process.

Figure 14 The Mechatronics Pulse Model

6 Conclusions

The proposed model appends to existing models for Systems Engineering and Design

Engineering to provide a strategy for mechatronics multidisciplinary interaction. The basic unit

of this model is the “pulse”, which allows the establishment of an agreement between disciplines

prior to independent disciplinary work, and also the convergence and integration afterwards. An

important observation is that the “pulse” model implies the need for skills related to

communication; this is not trivial since the type of communication is both at the personal level

and at the technical level. For this reason, one of the conclusions of this model is that participants

in a mechatronics project should be first introduced to a “multidisciplinary communication”

training process before starting the project/

7 Future Work

The authors consider this the first part of a model for mechatronics. Future work will include the

detailing of the different stages of the process to provide more specific strategies and tools

relevant to mechatronic design. The ultimate objective is to have a model that students can

follow for mechatronics projects.

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Documents

AC2012-4520: DEVELOPMENTOFADESIGNTHEORYANDMETHOD- … · the concept Computer-Aided Engineering (CAE). For instance, solidThinking is a tool that helps us in the conceptual design