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ME302: Mechatronics

Unit 8: Mechatronics System Design   This final unit is the capstone unit of this course. Unit 8 attempts to bring together everything that you have learned so far. You will become familiar with a systematic procedure for designing a mechatronic system by following a clear set of steps. It is important that you understand the role of the client, or the user, of the future system in stating his/her requirements and specifications for the future system. These requirements will be stated in nontechnical terms. As an engineer, you should be able to convert these nontechnical user requirements into technical system specifications.

Unit 8 Time Advisory
This unit should take approximately 6.25 hours to complete.

☐    Subunit 8.1: 0.75 hours

☐    Subunit 8.2: 3 hours

☐    Subunit 8.3: 2.5 hours

Unit8 Learning Outcomes
Upon successful completion of this unit, the student will be able to: - Identify the user-requirement specifications for a mechatronic system. - Identify and describe a clear set of steps to be followed in designing mechatronic systems.

8.1 User Requirements Specification (URS)   Take approximately 15 minutes to study the following information. The design of any mechatronic system must not commence until a clear set of user requirements has been specified. These are referred to as the User Requirements Specification (URS). The user requirements specification can encompass a number of different spheres. They can cover resolution, accuracy, weight, speed, and acceleration requirements. For systems that require a fast and accurate response, it can also cover dynamic response and steady state requirements as expressed below.

1.    Rise time: This is the time that the system requires in order to move to the new state (e.g., move from one position to the next position, increase the speed from one speed to another speed, etc.). The rise time is defined in different ways: it can be defined as the time required for the output of the system to increase from 10% of its final value to 90% of its final value. It can also simply be defined as the time required to reach final value. The rise time is very important as it is critical for systems that rely on a fast movement between positions, such as robots and automation systems in manufacturing.

2.    Overshoot: When the plant is being moved to its final position, it might overshoot that position and then return. This overshoot is undesirable, and the user might decide to limit this value. The overshoot is usually expressed as a percentage overshoot (MP%).

3.    Settling time: If the system does overshoot its final position, it will oscillate around its final position before it settles down. This time is denoted as settling time. This parameter is also important for the user as it will cause further delay to the operation of the system.

4.    Steady state error: Once the system has settled to its final value/position, you will notice that there may still be an error between the actual value and the desired value. This difference is referred to as the steady state error.

The following video will help you further understand these concepts.

When you study ME401: Dynamic Systems and Controls, you will go into more detail regarding the design of control system in order to achieve the dynamic system response requirements and the steady state error.

  • Web Media: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” Link: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” (Windows Media Player)

    Instructions: Please click on the link above, scroll down to video number 11.4, click on the link titled “PID Control of the Step Response of a Mechanical System,” and watch this video demonstration. You will note how the response of the system undergoes overshooting and steady state error. Also, note how the designer alters the type of controller used in order to reduce the overshoot, settling time and steady state error.

    Watching this video and pausing to take notes should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Web Media: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” Link: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” (Windows Media Player)

    Instructions: Please click on the link above, scroll down to video number 10.6, select the link titled “Computer Hard-Drive Track Seeking Demonstration,” and watch the video demonstration. Please note that speed and accuracy that is required in the movement of the reading head.

    Watching this video and pausing to take notes should take approximately 15 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

8.2 Steps in Mechatronics System Design (MSD)   The design of any mechatronic system must follow a series of clear steps. This ensures that the final design meets the user requirements specification as well as being functional and economical. These steps are clearly set out in the following document.

  • Reading: University of Jordan: Dr. Ashraf Saleem’s “Mechatronics Design Procedure” Link: University of Jordan: Dr. Ashraf Saleem’s “Mechatronics Design Procedure” (PDF)

    Instructions: Please click on the link above and then select the link titled “23a Mechatronics Design Procedure Amended by LAS” to download the PDF. Read all six pages of the document carefully and note the six steps that must be followed in designing a mechatronic system.

    Reading this document should take approximately 3 hours.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

8.3 Case Studies   In this subunit, we will look at two case studies. The first examines the design of a robot, based on a design developed in Clarence W. de Silva’s Mechatronics: An Integrated Approach.

The second case study is shown in a video that shows the use of a robotic arm to move an object based on a signal from a human’s bicep muscle.

In subunit 5.2, you watched the video titled “Robot Controlled by EMG Biosignal” in the context of transducers and signal processing, where you were asked to note how the signal was processed (e.g., signal rectification, filtering, and amplification). It is timely now to watch this video again and examine the system from a component selection and overall design point of view.

  • Reading: University of Jordan: Dr. Ashraf Saleem’s “Robot Design and Development” Link: University of Jordan: Dr. Ashraf Saleem’s “Robot Design and Development” (PDF)

    Instructions: Please click on the link above and then select the link titled “23c Robot Design” to download the PDF. Read all 22 pages of the document carefully and notice how the design steps have been followed in the design of the robotic system.

    Reading this document should take approximately 2 hours.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Web Media: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” Link: Colorado State University: Alciatore and Histand’s “Video Demonstrations from Introduction to Mechatronics and Measurement Systems” (Windows Media Player)

    Instructions: Please click on the link above, scroll down to video number 11.6, select the link titled “Robot Controlled by EMG Biosignal,” and watch the video demonstration. Please note the type of actuator used in this case (the robotic arm), the type of control algorithm used (simple multi-position), and the type of physical controller used (desktop PC in this case). Also, note how the designer carried out a process of calibration of the system.

    Watching this video and pausing to take notes should take approximately 30 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.