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Mechatronics

Purpose of Course  showclose

Most mechanical engineering systems today involve significant amounts of electrical and electronic control systems. Effectively, most modern mechanical engineering systems are mechatronic systems. Mechatronics is the discipline that results from the synergetic application of electrical, electronic, computer, and control engineering in mechanical engineering systems. Thus, it is essential for the mechanical engineer to have a strong understanding of the composition and design of mechatronic systems, which is the goal of this course. Mechatronic systems are around us everywhere. A car contains many mechatronic systems, such as anti-lock braking systems, traction control, the engine control unit and cruise control, to name a few. A satellite dish position control unit is another example of a mechatronic system. Modern industrial automated processes would not be possible without the discipline of mechatronics, covering areas such as vehicle manufacturing, pharmaceutical industries, and food processing plants. Robotic systems are interesting and complex examples of mechatronic systems that contain many sensors and actuators and that require very fast and sophisticated controllers. For you, as a mechanical engineering student, this course will represent a gateway into the world of electrical, electronic, and control engineering. It is one of the few courses in the mechanical engineering major that heavily relies on electrical, electronic, and computer engineering. Being a multidisciplinary/interdisciplinary course, your study of mechatronics integrates and builds on a number of different courses that you have already studied, such as mechanics, electromagnetism, measurements, and introduction to mechanical engineering (the design project).

Course Information  showclose

Welcome to ME302. General information about this course and its requirements can be found below.

Course Designer: Lutfi Al-Sharif

Primary Resources: This course comprises a range of different free, online materials. However, the course makes primary use of the following materials: Requirements for Completion: In order to complete this course, you will need to work through each unit and all of its assigned materials. Pay special attention to Unit 1 as this serves as an introduction to lay the groundwork for understanding the more advanced, exploratory material presented in the latter units. You will also need to complete:
  • Subunit 1.2 Activity
  • The Final Exam
Note that you will only receive an official grade on your final exam. However, in order to adequately prepare for this exam, you will need to work through all of the resources in each unit as well as the activity listed above.
 
In order to pass this course, you will need to earn a 70% or higher on the final exam. Your score on the exam will be tabulated as soon as you complete it. If you do not pass the exam, you may take it again.
 
Time Commitment: This course should take you a total of 109.5 hours to complete. Each unit includes a time advisory that lists the amount of time you are expected to spend on each subunit. These should help you plan your time accordingly. It may be useful to take a look at these time advisories and to determine how much time you have over the next few weeks to complete each unit, and then to set goals for yourself. For example, Unit 1 should take you 10.5 hours. Perhaps you can sit down with your calendar and decide to complete subunit 1.1 (a total of 6 hours) on Monday and Tuesday nights; subunits 1.2 through 1.4 (a total of 4.5 hours) on Tuesday night; etc.
 
Tips/Suggestions: Take comprehensive notes as you work through each resource, writing down any examples of concepts, definitions, etc. These notes will serve as a useful review as you study and prepare for the final exam.
 
Other Notes: The prerequisites for this courses included the following: ME005/PHYS101 was a basic course that laid down the principles of mechanics that you will need in studying many of the mechanical engineering courses. In ME006/PHYS102, you studied some of the prerequisite electrical and electronic content that you are going to need in this course. It is advisable that you review some of the electromagnetism basics, especially the right-hand rule and the left-hand rule. You should also review the electrical components and electrical circuit basics (resistors, capacitors, and inductors) that you studied in ME301: Measurement and Experimentation Laboratory. It is also important that you are familiar with the mechanics basics that you studied in ME102: Mechanics I and ME202: Mechanics II, especially the application of Newton’s second law to translational and rotational systems. The concept of a design project was introduced in ME101: Introduction to Mechanical Engineering, and this will be very helpful when you are working on Unit 8 of this course. This course will also provide you with excellent preparation for the advanced course ME401: Dynamic Systems and Controls; it is essential that you study ME302 prior to studying ME401. A graphical overview of this course can be seen here.

Khan Academy  
This course features a number of Khan Academy™ videos. Khan Academy™ has a library of over 3,000 videos covering a range of topics (math, physics, chemistry, finance, history and more), plus over 300 practice exercises. All Khan Academy™ materials are available for free at www.khanacademy.org.

Learning Outcomes  showclose

Upon successful completion of this course, the student will be able to:
  • Define the discipline of mechatronics.
  • Identify examples of mechatronic systems that are encountered in real life.
  • Identify the components of a typical mechatronic system.
  • Analyze and solve problems in simple electrical and electronic circuits.
  • Discuss the importance of feedback in controlling physical systems with the use of examples.
  • Identify and describe the different types of actuators used in mechatronic systems.
  • Identify and describe the different types of speed- and position-feedback devices.
  • Explain the principle of operation of the four types of motors: ac induction motor, the dc motor, the servomotor, and the stepper motor.
  • Size the motor for an application.
  • Select the suitable type of motor for an application.
  • Identify the signal processing that has to be applied to signals in mechatronic systems.
  • Identify and describe the types of controllers used in mechatronic systems.
  • Select the suitable type of controller for an application.
  • Explain the steps in designing a mechatronic system, and design a mechatronic system by following these steps.

Course Requirements  showclose

In order to take this course, you must:

√    have access to a computer;

√    have continuous broadband Internet access;

√    have the ability/permission to install plug-ins or software (e.g., Adobe Reader or Flash);

√    have the ability to download and save files and documents to a computer;

√    have the ability to open Microsoft files and documents (.doc, .ppt, .xls, etc.);

√    have competency in the English language;

√    have read the Saylor Student Handbook; and

√    have completed the following courses as prerequisites: ME005/PHYS101, ME006/PHYS102, ME101, ME102, ME202, and ME301.

Unit Outline show close


Expand All Resources Collapse All Resources
  • Unit 1: Introduction to Mechatronics  

    This unit will introduce you to the discipline of mechatronics. This is necessary in order to allow you to understand the overall composition of a mechatronic system and its generic components prior to delving into the details. Upon completion of this unit, you will appreciate how widely present mechatronic systems are in everyday life and how important they are. You will also be able to identify the typical basic components of a mechatronic system: the physical system being controlled, the actuator that affects the physical system, sensors that feedback information about the physical system, and a control system that controls the actuator based on the feedback signal from the feedback device.

    Unit 1 Time Advisory   show close
    Unit 1 Learning Outcomes   show close
  • 1.1 Definition of Mechatronics  
    • Reading: Rensselear Polytechnic Institute and Marquette University: Kevin Craig’s Multidisciplinary Mechatronic Innovations: “Introduction to Mechatronics – Magnetic Levitation System”

      Link: Rensselear Polytechnic Institute and Marquette University: Kevin Craig’s Multidisciplinary Mechatronic Innovations: “Introduction to Mechatronics – Magnetic Levitation System” (PDF)

      Instructions: Please click on the link above, scroll down to the title “Introduction to Mechatronics – Magnetic Levitation System,” and click on the title to download the PDF. You only need to read pages 1 to 48. Pay particular attention to the following pages: 1 to 13, which provide an introduction to the discipline of mechatronics, and pages 22 to 48, which provide an introduction to how mechatronics is applied to problem solving in automotive engineering.

      You will notice that the target system (physical system) to be controlled does not always need to be a pure mechanical system. The system to be controlled is sometimes referred to as the plant. It can be any of the following types of systems: mechanical (translational or rotational), fluidic (hydraulic or pneumatic), thermal, chemical, electrical, or any combination of the above.

      Various authors use different definitions of mechatronics. In this course, the following definition shall be adopted.

      Mechatronics is the discipline that results from the synergetic application of electrical, electronic, computer, and control engineering in mechanical engineering systems.

      You will notice that the term synergetic has been used in the definition. Synergy is the phenomenon whereby additional results or benefits are achieved from the use of multiple disciplines or tools that are not achievable by the separate use of each of these disciplines or tools.

      Reading this chapter should take approximately 6 hours.

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

      See a broken link? Please let us know!

  • 1.2 Examples of Mechatronic Systems  

    In the last subunit, you saw an example of the use of mechatronics in automotive engineering. The following three videos introduce you to further examples of mechatronic systems: a mobile robot, a quad-rotor, and a printer.

  • 1.3 Components of a Mechatronic System  

    There are basically four main components of any mechatronic system. Some mechatronic systems might contain some other components, but these four are essential for the successful operation of a mechatronic system:

    1. physical system being controlled: the physical system being controlled may be mechanical, fluidic, chemical, thermal, or electrical;
    2. actuator: the actuator provides the force or torque (or other relevant physical input) to the physical system being controlled. In mechanical systems, the actuator could be either translational (usually referred to as linear) or rotational;
    3. sensors: sensors are the eyes and ears of the controller. Sensors are also referred to as transducers, although strictly speaking there are subtle differences between sensors and transducers; and
    4. controller: the controller is the brain of the mechatronic system. It reads the input signals representing the state of the system, compares them to the required states, and outputs signals to the actuators to control the physical system.

  • 1.4 The Multi-Disciplinary Design Process  

    By definition, a mechatronic system is a multi-disciplinary system. For this reason, it requires a modern approach to the design process as opposed to the classical single disciplinary design process.

    • Reading: Engineering and Technology Magazine: Sarah Brady’s “Multidisciplinary Machine Building”

      Link: Engineering and Technology Magazine: Sarah Brady’s “Multidisciplinary Machine Building” (HTML)

      Instructions: Please click on the link above and read this article. Sarah Brady emphasizes the importance of applying the multi-disciplinary design process in designing mechatronic systems. In some cases, the design process of mechatronic systems is referred to as systems engineering.

      From the article, you will note the following information.

      1. Modern engineering systems have become very complex. This complexity is necessary in order to deliver the performance that we have come to expect of modern systems. This complexity presents difficulties to the designers as they have to integrate the various disciplines while using a parallel design process.
      2. You have already come across the concept of synergy. Synergy is the phenomenon whereby a result is obtained by combining different components, which is greater than or unachievable by using these components on their own.
      3. Reliability and quality can be achieved by applying the multi-disciplinary design process. Reliability and quality are very critical to the success of all modern engineering systems such as manufacturing systems, home appliances, vehicles, and aircraft.
      4. You may have noticed the use of the term embedded when discussing controllers. This term is used to refer to a controller (usually a microprocessor or a microcontroller integrated circuit) that is located and integrated within the system to be controlled.

      Reading this article should take approximately 30 minutes.

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

      See a broken link? Please let us know!

  • Unit 2: Electrical and Electronic Principles  

    This unit will review some of the electrical and electronic principles that you have already studied and will introduce you to some new ones. In PHYS102 (Introduction to Electromagnetism), you studied the three main electrical components: the resistor, the capacitor, and the inductor. You also studied the analysis of circuits containing these components, such as RLC circuits. In this unit, we will revisit the operation of these components and show how they are analogous to some of the mechanical components that you are already familiar with (such as dampers, springs, and masses). You will then be introduced to some simple circuits to analyze. This will be followed by the study of electronic components such as diodes and transistors. The last part of this unit will introduce you to digital logic and associated electronic devices that are used to implement digital logic. The electrical and electronic principle that you will study in this unit are critical to building control-systems for the mechatronic system and interfacing the controllers to the physical system.

    Unit 2 Time Advisory   show close
    Unit 2 Learning Outcomes   show close
  • 2.1 Basic Electrical Components  

    There are three basic electrical components of all electrical circuits: resistors, capacitors, and inductors. These components are referred to as passive components, as they do not contain a power supply. This is in contrast with active components, such as amplifiers that require a power supply to operate.

  • 2.1.1 Resistors  
  • 2.1.2 Capacitors  

    A capacitor acts as a storage medium for an electric charge. A capacitor is formed as soon as two conducting plates are placed in parallel positions. As the charge accumulates on the plates of the capacitor, an electric field results. The material between the two plates is important as it has an effect on the final value of the capacitance. The capacitor stores energy in an electrical format. In order to revise the basic concepts of capacitors, read the material accessed via the resources linked below.

  • 2.1.3 Inductors  

    Inductance results when a conductor is wound a number of turns around a former. An inductor resists the sudden change of the value of the current flowing through it. Energy is stored in a magnetic form within the inductor. The inductance of a coil is sometimes referred to as self-inductance.

  • 2.2 Analysis and Solving of Simple Electrical Circuits  

    Having been introduced to the individual electrical components, in this subunit we will move on to look at the analysis of circuits that comprise these components.

  • 2.3 Basic Electronic Components: Diode, Bipolar Junction Transistors, and Field Effect Transistors  

    In this subunit, we will examine various electronic components that comprise most electronic circuits. This subunit introduces two important electronic components: diodes and transistors. Diodes are semiconductor devices that allow currents to flow only in one direction. A diode is constructed using a PN junction. Transistors are semiconductor devices that can be used as electronic switches, whereby they can switch electrical devices on and off.

  • 2.4 Basics of Boolean Logic  

    This subunit will introduce you to the basics of digital logic, referred to as Boolean logic in reference to the English born mathematician George Boole.

  • 2.5 Logic Gates  

    By using electronic components such as transistors, diodes, resistors, and capacitors – designed within integrated circuits – logic gates can be built. Logic gates can be successfully used to build control systems.

  • 2.6 Designing Basic Logic Circuits  

    Karnaugh mapping is a tool that can be used to design logic circuits to achieve the required logic function.

  • Unit 3: Actuators  

    Motion is the basic activity within a mechatronic system, whereby a mechanical system is being controlled by the use of actuators under a supervising control system. Position, speed, or both, are usually the controlled variables in a mechatronic system. The following are examples of mechatronic systems in which speed, position, or both, are monitored and controlled: the speed of a conveyor belt has to be closely controlled in order to ensure that items spend exactly the correct time in a process; the position of a robotic arm manipulator has to be very accurately controlled in order to successfully achieve a delicate task (e.g., surgery); and in an elevator system, both speed and position have to be accurately controlled.

    In order to achieve motion, actuators are needed. An actuator is a device that can produce force in order to achieve linear acceleration in translational systems, or that can produce torque in order to achieve rotational acceleration in rotational systems.

    Thus, it is important to be aware of the different types of actuators that can be used in mechatronic systems to bring about motion. This unit will introduce you to the different types of actuators and will provide you with guidance on the advantages and disadvantages of each actuator to enable you to select the correct one for a given application.

    Unit 3 Time Advisory   show close
    Unit 3 Learning Outcomes   show close
  • 3.1 Introduction to Actuators  

    Actuators are important in mechatronic systems as they bring about motion. They can be translational or rotational. Electrical motors are the most widely used type of actuator in mechatronic systems. Electric motors are electromagnetic actuators that convert electrical energy into mechanical energy. All electric motors provide mechanical energy in a rotational form (torque and rotational speed). An actuator can be thought of as a device that converts electrical energy into mechanical energy.

    A lead screw is a device that converts rotational motion into translational motion. Pulleys, sheaves, or sprockets are devices that can convert rotational motion into translational motion and vice versa. A gear box can change the speed and torque of rotational motion and is thus a device that matches the motor to the load. More information about gearboxes will be given in the last subunit of this unit.

  • 3.2 Analogy between Electrical Circuits and Magnetic Circuits  

    The videos that you watched in the previous subunit have introduced you to different types of actuators (hydraulic, pneumatic, and electromagnetic). Some were rotational and others were translational (linear). We now will move on to have a detailed look at the different types of actuators. Before introducing the four types of motors, some basic electromagnetic principles are reviewed below. You will need to revise the following basic principles in preparation for the rest of this unit.

  • 3.3 Motor and Generator Principles  

    This subunit introduces some basic concepts necessary for understanding DC motor operation.

  • 3.4 Types of Actuators  

    This subunit will concentrate on the electromagnetic actuators used in mechatronic systems.

  • 3.4.1 General Introduction to Motors  
  • 3.4.2 Brushed DC Motors  

    DC motors have traditionally been used as they offer high starting torque and good speed control. DC motors are usually of the brushed type; they have brushes that allow connecting the supply to the rotating armature. Recently, brushless DC motors have become available, whereby the switching function is achieved using solid state electronics. Brushes and commutators require continuous maintenance and can be a source of unreliability for DC motors.

  • 3.4.3 Brushless DC Motors  

    This sub-subunit examines the brushless type of DC motor. One of the main disadvantages of brushed DC motors is the maintenance requirements that are necessary for the brushes and commutators. A brushless DC motor uses Hall Effect sensors to switch the current within the armature without the need for mechanical brushes and commutators. This improves the reliability of motor and reduces the maintenance requirements.

  • 3.4.4 AC Induction Motor  

    The squirrel cage induction motor (referred to as SCIM for short) is the workhorse of the modern industry. It is used in 90% of industrial applications. The reason it is widely used is because of its robustness and reliability. It is effectively maintenance free. The main problem with the AC induction motors is that it has been difficult to vary their speed until power electronics has been applied in the design of variable speed drives that can vary the speed of the AC induction motors.

    • Reading: University of Jordan: Dr. Lutfi Al-Sharif’s “Introduction to AC Induction Motors”

      Link: University of Jordan: Dr. Lutfi Al-Sharif’s “Introduction to AC Induction Motors” (PDF)

      Instructions: Please click on the link above to access the PDF, and read this article (16 pages). When reading the following document, pay special attention to the following items: the principle of a rotating constant magnitude magnetic field; how the intersection of the rotating magnetic field with the squirrel cage rotor; how to calculate the speed of rotation of the motor; and the concept of synchronous speed, asynchronous speed, and slip.

      From this article, you will notice that a constant magnitude rotating magnetic field is produced by shifting three vectors of magnetic fields by 120 degrees in space (arrangement of the coils in a motor) and 120 degrees in time (three phase power supply).

      Reading this article should take approximately 3 hours.

      Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 license. It is attributed to Dr. Lutfi Al-Sharif and the original can be found here.

      See a broken link? Please let us know!

    • Web Media: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles”

      Link: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles” (Windows Media Player)

      Instructions: Please click on the link above, scroll down to the “Actuators” section, and select the link titled “AC Induction Motor (Single Phase)” to download the video. View the brief demonstration, which shows the construction of a single phase squirrel cage induction motor. Notice how the bars in the rotor are skewed in order to reduce vibration or pulsation in the torque.

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

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

      See a broken link? Please let us know!

    • Web Media: YouTube: Gotchacam’s “Assembly of AC Induction Motors”

      Link: YouTube: Gotchacam’s “Assembly of AC Induction Motors” (YouTube)

      Instructions: Please click on the link above and watch this video. This video shows the construction of a three phase AC squirrel cage induction motor. Note the different stages of building the motor, starting with the stator and then the rotor. Also, note how special attention is paid to the balancing of the rotor to avoid vibration at full speed.

      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.

      See a broken link? Please let us know!

    • Web Media: YouTube: Gotchacam’s “Assembly of AC Induction Motors”

      Link: YouTube: Gotchacam’s “Assembly of AC Induction Motors” (YouTube)

      Instructions: Please click on the link above and watch this video. This video shows the construction of a three phase AC squirrel cage induction motor. Note the different stages of building the motor, starting with the stator and then the rotor. Also, note how special attention is paid to the balancing of the rotor to avoid vibration at full speed.

      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.

      See a broken link? Please let us know!

  • 3.4.5 Stepper Motors  

    As opposed to the DC motors and the AC induction motors, stepper motors move in specified steps. They are effectively digital motors. For these reasons, they are ideal for accurate positioning applications. However, they are generally limited to low power applications.

  • 3.4.6 Servo-Motors  

    A servo-motor is a DC motor that has been fitted with position feedback and a close loop control system. This makes a servo-motor ideal for use in accurate positioning application such as robotic arms. Similar to the stepper motor, it is limited to small power applications.

    • Web Media: YouTube: Bartek Sliwinski’s “How Do Servos Work?”

      Link: YouTube: Bartek Sliwinski’s “How Do Servos Work?” (YouTube)

      Instructions: Please click on the link above and watch the video, which shows the construction of a servo-motor. From watching the video, you will notice the following: a servo motor is basically a DC motor with a closed loop control system; the angular position of the rotor is monitored using a potentiometer; a control circuit is used to compare the required angular position with the actual angular position of the rotor; the control circuit then moves the motor in order to eliminate the difference between the actual angular position and the required angular position; and the required position is communicated to the motor via a pulse that has a time duration corresponding to the required angle.

      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.

      See a broken link? Please let us know!

    • Web Media: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles”

      Link: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles” (Windows Media Player)

      Instructions: Please click on the link above, scroll down to the “Actuators” section, and select the link titled “Radio Control (RC) Servo Motor with Pulse-Width-Modulation Control” to download the video. View the brief demonstration, which clearly illustrates the aforementioned point about how the required angle is achieved.

      Watching this video and pausing to take notes should take less than 5 minutes.

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

      See a broken link? Please let us know!

    • Web Media: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles”

      Link: Colorado State University’s “Video Demonstrations of Mechatronic Devices and Principles” (Windows Media Player)

      Instructions: Please click on the link above, scroll to the “Actuators” section, and select the link titled “Servo Motor System” to download the video. Watch the brief demonstration, which shows the use of two servo motors fitted with feedback devices and controllers.

      Watching this video and pausing to take notes should take less than 5 minutes.

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

      See a broken link? Please let us know!

  • 3.5 Criteria for Actuator Selection  

    A critical part of the mechatronics system design process is the selection of a suitable actuator. There are a number of important factors that must be taken into consideration when selecting a suitable actuator.

  • 3.6 Sizing of Actuators  

    When sizing a motor, the most important parameter that needs to be calculated is the torque. This is usually referred to as the rated torque. Once the rated torque has been calculated based on the application, the necessary motor can be selected from the datasheet. The following two problems illustrate the data needed to calculate the required torque. The first problem is that of selecting an AC induction motor for an elevator.

  • 3.7 Use of Gearboxes to Match Speed and Torque  

    Gearboxes are extremely important in mechanical and mechatronic systems. A gearbox is a device that can change both speed and torque. It can be used to match the actuator output with the mechanical system under control.

    In many cases, the actuator speed (e.g., motor) is too high for the application, and the torque it produces is too low. Using a gearbox reduces the rotational speed and increases the rotational torque. Under ideal conditions, the input power is equal to the output power. Under such ideal conditions, the product of the input rotational speed and the input torque is equal to the product of the output rotational speed and the output torque. In reality, the output power will be less than the input power, and the ratio of the output power to the input power is the efficiency of the gearbox.

    In most applications, gearboxes are used as step down devices, as they reduce the speed and increase the torque.

  • Unit 4: Feedback Devices  

    In the last unit, you studied the types of actuators used in mechatronic systems. The feedback devices are equally important to the actuators. Feedback devices are effectively the eyes and ears of the control system that enable it to accurately control the mechatronic system. As mentioned in the last unit, it is generally necessary to control position, speed, or both. Thus, it is important to have available feedback devices for position and speed. This unit will introduce you to the different types of feedback devices that are used in mechatronic systems. Feedback devices in mechatronic systems are mainly used to measure the position, speed, or orientation of the system that is being controlled.

    In the following three subunits, you will be introduced to three groups of feedback devices that are used in mechatronic systems. In order for a controller to properly control a mechatronic system, it needs to possess accurate and up-to-date information about the velocity and position of the system. This allows the controller to compare the desired velocity (or position) with the actual velocity (or position) and to adjust the actuator outputs accordingly. Providing such information is the role of feedback devices.

    Unit 4 Time Advisory   show close
    Unit 4 Learning Outcomes   show close
  • 4.1 Shaft Encoders: Incremental and Absolute Shaft Encoders  

    A shaft encoder is a device that is mechanically connected to a rotating shaft, such that it rotates at exactly the same speed of the shaft and attains exactly the same position, and it provides an electrical output that represents the position, speed or both of the mechanical shaft to which it is connected.

    Shaft encoders are digital in nature. They provide an output in a digital format in the form of pulses. Shaft encoders are of two types: incremental and absolute. Incremental shaft encoders provide a stream of pulses that are proportional to the rotational speed of the shaft. In effect, incremental shaft encoders are ideally used for speed feedback.

    Absolute shaft encoders, on the other hand, provide a digital output that represents the actual rotational position of the shaft. Absolute shaft encoders provide an output in the form of a number of bits (e.g., 12 bit; 14 bit; 18 bit). The angular resolution of the shaft encoder increases as the number of bits increases.

  • 4.2 Linear Variable Differential Transformer: Principle of Operation  

    The shaft encoders discussed in the last subunit are rotary in nature. The linear variable differential transformer is the main feedback device used for linear position feedback. It is very widely used in industrial applications.

  • 4.3 Accelerometers: Principle of Operation  

    The feedback devices discussed in the last two subunits measure velocity or displacement. It is also possible to measure acceleration directly by the use of accelerometers. It is common in some applications to measure acceleration and derive velocity by the use of integration. One of the most widely used types of accelerometers is the so-called seismic accelerometer.

  • Unit 5: Signal Processing  

    In any mechatronic system, signals flow into and out of the system. These signals are essential for controlling the system and feeding back information about the system. These are effectively the nerve signals in the system. The signals that are received from the physical world and sent to the controller are not in a suitable format. They need to be converted to a suitable format in order to allow the controller to make use of them. This is the aim of signal processing or signal conditioning. Signal processing or signal conditioning in the mechatronics context is the conversion of feedback signals such that they are suitable for use by the controller.

    However, these signals require different types of processing. For example, the signal could be mixed with noise; thus, it could be in need of filtering. It could be weak and small in value; thus, it could be in need of amplification. It could be in an analogue format; thus, it could be in need of conversion to a digital format. These are examples of some of the signal processing operations that are required.

    This unit will introduce you to the principles of signal processing and the electronic circuits that can achieve such processing.

    Unit 5 Time Advisory   show close
    Unit 5 Learning Outcomes   show close
  • 5.1 Operational Amplifier Circuits  

    An operational amplifier is an electronic circuit building block that can be used to build signal conditioning circuits. It saves the user from the need to re-invent the wheel, such that he or she does not need to build an amplifier circuit but merely needs to connect the operational amplifier such that the function of the circuit is achieved. The operational amplifier is often referred to as op-amp for brevity.

  • 5.2 Filtering Circuits  

    In certain conditions, the signal is contaminated with noise. If the noise has a frequency that is different to the frequency of the signal, then it is possible to remove the noise from the signal by a process known as filtering. Filtering removes components of a signal based on frequency. Filters are one of four types: low pass filtering, high pass filtering, band pass filtering, and bandstop filtering.

  • 5.3 Analogue and Digital Signal Conversion  

    Signals in the physical world exist in an analogue format, whereby the signal magnitude is analogous or proportional to the physical variable magnitude. In order to process a signal within a digital controller or a laptop, it has to be converted to a digital format in which a signal is represented in bits. It is important to convert analogue signals to digital signals and vice versa. These two processes are denoted as analogue to digital conversion (A to D conversion or ADC) and digital to analogue conversion (D to A conversion or DAC).

    ADC is necessary to acquire signals from the real world and use them within the controller. DAC is necessary to allow the controller to output a signal to the physical world to control a system.

  • Unit 6: System Dynamics  

    Any mechanical, electrical, fluidic, or thermal system has certain unique characteristics in how it responds to external excitation. Prior to attempting to control a physical system, it is important to understand its dynamic response to an external excitation. This unit will introduce you to the concept of system dynamics and its importance to mechatronic system design. Critical to the understanding and modeling the dynamics of a system is the differential equation that relates the input of the system to the output of the system. Differential equations are the ideal tool for capturing the dynamics of a system and its response to external inputs.

    It is critical that prior to starting this unit, you review what you have studied on differential equations, especially those used to describe mechanical systems (mainly contained in ME202: Mechanics II). If necessary, review ME202 before beginning this unit.

    Unit 6 Time Advisory   show close
    Unit 6 Learning Outcomes   show close
  • 6.1 System Dynamics  

    Understanding the dynamics of a system is very important in achieving successful control. You will see from the video below how failure to understand system dynamics can lead to disastrous outcomes, as can be seen in the collapse of the Tacoma Narrows bridge.

  • 6.1.1 The Concept of a System  

    The mechatronic system that we are trying to control is usually referred to as the plant (e.g., mechanical system, electrical system, etc.). The plant that we are attempting to control is a system. In the case of the video below, the plant is mass vertically suspended on a spring. A system is a set of interconnected components that interacts with its environment. We are interested in the inputs and outputs to and from the system. Below, you will watch a video on system modeling by Kevin Craig.

  • 6.1.2 The Use of Ordinary Differential Equations to Describe the Dynamic Behavior of a System  

    In any mechatronic system, we are interested in a specific output variable that we are attempting to control. We will usually control the output variable by setting the input variable to the desired value. Hence, the dynamic relationship between the input variable and the output variable is very important. Most systems have multiple inputs and multiple outputs, and their analysis become more involved. In the material discussed in this unit, we will restrict the analysis to single input single output (SISO) systems. The ideal tool to capture the dynamic relationship between the input variable and the output variable is the differential equation.

  • 6.2 First-Order Systems  

    The simplest form of a dynamic model for a system is the first order system. A first order system is typically represented by a time constant. When we try to charge a capacitor in a resistor-capacitor circuit, the response follows a first order system response. A tank full of water that has a small hole at its lower end will also follow a first order system response. The following video will discuss the response of a first order system.

  • 6.3 Second-Order Systems  

    Few of the dynamic systems found in practice are not first order systems. They are usually second order system or higher. Second order systems are obviously more complicated, and their analysis is more involved. The following video discusses the response of second order systems to a step input. You will notice that the response of second order system to a step input could either be over-damped, critically damped, or under-damped.

  • Unit 7: Controllers  

    A controller is at the brain of any mechatronic system. The controller reads feedback signals from the feedback devices, compares these signals to the desired values, and then sends out signals to the actuators that control the mechatronic system.

    We must distinguish between the physical implementation of the controller and the control algorithm embedded within it. The physical implementation of the controller is the device that is used as the controller. On the other hand, the control algorithm that is embedded within the physical controller is the set of instructions that are used to make the control decisions. You will study these algorithms in a later course (ME401: Dynamic Systems & Controls).

    In this unit, you will learn about the different types of physical controllers that are used to control mechatronic systems. You will also learn to distinguish between the physical controller that is used to control a mechatronic system (which is the subject of this unit) and the control algorithm that is coded within it (which is what you will learn in ME401: Dynamics Systems & Controls). You will learn the advantages and disadvantages of each type of physical controller and its typical areas of application. You will also be able to select a suitable type of controller for an application.

    Unit 7 Time Advisory   show close
    Unit 7 Learning Outcomes   show close
  • 7.1 Types of Controllers  
  • 7.2 Selection Criteria for Controllers  
  • 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   show close
    Unit 8 Learning Outcomes   show close
  • 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.

  • 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.

  • 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.

  • Final Exam  
    • Final Exam: The Saylor Foundation’s “ME302 Final Exam”

      Link: The Saylor Foundation’s “ME302 Final Exam”

      Instructions: You must be logged into your Saylor Foundation School account in order to access this exam.  If you do not yet have an account, you will be able to create one, free of charge, after clicking the link.

      The Saylor Foundation does not yet have materials for this portion of the course. If you are interested in contributing your content to fill this gap or aware of a resource that could be used here, please submit it here.

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