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L1 (25 July 2014)

Background of Mechatronics

L1.1. What precisely is Mechatronics? A Venn diagram illustrating the synergy of several engineering disciplines that constitute the field mechatronics (see figure below).

Figure 1. Venn diagram illustration of mechatronics.

In several technical areas the integration of products or processes and electronics can be observed. This is especially true for mechanical systems which developed since about 1980. These systems changed from electro-mechanical systems with discrete electrical and mechanical parts to integrated electronic-mechanical systems with sensors, actuators, and digital microelectronics. These integrated systems, as seen in figure below, are called mechatronics systems, with the connection of MECHAnics and elecTRONICS.

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Figure 2. Historical development of mechanical, electrical, and electronic systems (Bishop,

2002), p.25.

Mechatronics is the field of study concerned with the design, selection, analysis, and control of systems that combine mechanical elements with electronic components, including computers and/or microcontrollers. In other words, it is an interdisciplinary field, in which the following disciplines act together:

· Mechanical systems (mechanical elements, machines, precision mechanics); · Electronic systems (microelectronics, power electronics, sensor and actuator technology);

and · Information technology (systems theory, automation, software engineering, artificial

intelligence). The preliminary definition is: "Mechatronics is the synergetic integration of mechanical engineering with electronics and intelligent computer control in the design and manufacturing of industrial products and processes" (Harashima, Tomizuka, & Fukuda, 1996). This definition was coined by Yasakawa Electric Company (Harashima et al., 1996) to refer to the use of electronics in mechanical control (i.e., ‘mecha’ from mechanical engineering and ‘tronics’ from electrical or electronic engineering). Later, in (Auslander, Ridgely, & Ringgenberg, 2002), the authors have defined mechatronics as the application of complex decision-making to the operation of physical

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systems. This definition removes the specific technology to be used to perform the operation from the definition. 1. Identify a Mechatronics System and Its primary Elements. A block diagram of a typical mechatronic system is shown in Figure 3 ((Alciatore & Histand, 2012)-P.3).

Figure 3. Mechatronics system components.

The actuators produce motion or cause some action; the sensors detect the state of the system parameters, inputs, and outputs (both sensors and actuators are key to implementing feedback control of motion-control system); digital devices control the system; conditioning and interfacing circuits provide connections between the control circuits and the input/output devices; and graphical displays provide visual feedback to users. In fact, a mechatronic system has at its core a mechanical system which needs to be commanded or controlled. Such a system could be a vehicle braking system, a positioning table, an oven, or an assembly machine. The controller needs information about the state of the system. This information is obtained from variety of sensors, such as those that give proximity, velocity, temperature, or displacement information. In many cases, the signals produced by the sensors are not in a form ready to be read by the controller and need some signal conditioning operations performed on them. The conditioned, sensed signals are then converted to a digital form (if not already in that form) and presented to the controller. The controller is the ‘mind’ of the mechatronic system, which processes user commands and sensed signals to generate command signals to be sent to the actuators in the system. The user commands are obtained from a variety of devices, including command buttons, graphical user interfaces (GUIs), touch screens, or pads. In some cases, the command signals are sent to the actuators without utilizing any feedback information from the sensors. This is called open-loop operation, and for it to work, this requires a good calibration between the input and output of the system with minimal disturbances. The more common mode of operation is the closed-loop mode in which the command signals sent to the actuators utilize the feedback information from the sensors. This mode of operation does not require calibration information, and it is much better suited for handling disturbances and noise.

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In many cases, the command signals to the actuators are first converted from a digital to an analog form. Amplifiers implemented in the form of drive circuits also can be used to amplify the command signals sent to the actuators. The choice of the controller for the mechatronic system depends on many factors, including cost, size, ease of development, and transportability. Many mechatronic systems use personal computers (PCs) with data acquisition capabilities for implementation. Examples include control of manufacturing processes such as welding, cutting, and assembly. A significant number of controllers for a mechatronic system are implemented using a microcontroller unit (MCU), which is a single-chip device that includes a processor, memory, and input-output devices on the same chip. Microcontrollers often are used for control of many consumer devices, including toys, hand-held electronic devices, and vehicle safety systems. Control systems that use MCUs often are referred to as embedded control systems. Circuits also can be used to amplify the command signals sent to the actuators.

Mechatronic systems are widely used in everyday life. For illustrating mechatronics systems, we will discuss four available systems:

· Industrial Robots

Figure 4. Industrial robot (Jouaneh, 2013), p.3.

Robots, whether of the fixed type (such as industrial robots) or of the mobile type, are good examples of mechatronic systems. Figure above shows an industrial robot arm. A robot is a mechanical device that can be programmed to perform a wide variety of applications. The main components of a robot system are the controller and the mechanical arm. The controller handles several operations, including the user interface, programming, and control of the arm. The mechanical arm consists of several mechanical links that are connected at joints. An actuator is used to drive each link, and each actuator has a feedback sensor to indicate the location of the link. A multi-link robot is a complicated device that requires coordination of the motion of the links. This job is done by the control software, which processes information from the desired motion of the arm, and the feedback sensors, which send commands to the actuators or the servomotors to perform the desired task. To enable a robot to handle variation in the environment in which it operates, additional sensors are normally used (such as vision and proximity).

· Mobile Robots

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Figure 5. Roomba® vacuum-cleaning robot.

Mobile robots are currently being used in a wide diversity of applications. Whether vacuum cleaning, assisting soldiers in combat operations, or delivering food and medicine in hospitals, their use is increasing. Similar to their fixed counterparts, a mobile robot consists of a number of modules that are commanded by a controller. Due to their operation in unstructured environments, mobile robots rely heavily on sensors to guide them in navigation and to avoid obstacles. Examples of sensors used by mobile robots include ultrasonic proximity sensors, vision sensors, and global positioning system sensors. An example of a mobile robot is the Roomba® vacuum-cleaning robot (see figure above) made by iRobot Corporation. The Roomba has a cylindrical shape, two wheel modules, and a sensor to detect obstacles. The Roomba has all of the main components of a mechatronic system: actuators (wheel modules), sensors (target and dirt), and a controller.

· Scanner

Figure 6. A flatbed scanner.

A scanner (see figure above) is a device that captures an image of a document and converts it into a format suitable for electronic storage. The main components of a scanner include the scanning head, the transport device, the controller, and the control software. The controller commands the transport device which carries the scanner head. The transport device uses a stepper motor and a system of gears and belts to move the scanning head in precise steps. After each step, the transport device stops, and a scan is sampled. The scanning head involves some form of a line camera that measures the reflectivity of a scanned line. The scanned line is brought to the scan sensor through a system of mirrors and lenses. The output of the scanning head is processed by the control software to create a map of the scanned document. This map is further analyzed to reveal all of the features in the document and to filter any noise signals from the captured data. The control software sequences the operation of the scanner and communicates with the PC. When the scanning job is completed, the scanned image is then transferred to a PC using a USB or a parallel-port connection. This

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mechatronics system involves all of the elements of a typical control system: sensor, actuator, and controller. It is also an example of a discrete-event system.

· Parking Gate

Figure 7. Parking gate.

A parking garage gate (see figure above) is another example of a mechatronics system that involves a number of elements. The system has an electric motor to raise and lower the gate arm. It also has a proximity sensor to prevent the gate from striking people and vehicles. In addition, it has a microcontroller in which software is used to run the gate in different operating modes. Typically, a parking-garage gate operates as follows: The user presses a button to get a ticket or swipes a card in a card scanner. Once the ticket is picked up by the user or the card is validated, the gate arm rotates upward. The gate arm remains in a raised position until the vehicle has completely cleared the gate, at which point the gate drops down. The operation of each stage of this system is dependent on sensor feedback and timing information. The controller for this system cycles between the different operating stages each time a vehicle needs to enter the parking garage.

· Printer Demo · Dance Demo · Walk Demo · Agile Eye Demo

2. Define the Elements of a general Measurement System. A fundamental part of many mechatronic systems is a measurement system composed of the four basic parts illustrated in figure below.

Figure 8. Elements of a measurement system (Jouaneh, 2013), p.210.

· The physical quantity changes a property of the transducer (such as its resistance, inductance, or magnetic coupling).

· The transducer is a sensing device that converts a physical input into an output, usually a voltage.

· The signal conditioning device performs filtering, amplification, or other signal conditioning on the transducer output.

· The term sensor is often used to refer to the transducer or to the combination of transducer and signal processor.

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· Finally, the display or recording device is an instrument, a computer, a hard-copy device, or simply a display that maintains the sensor data for online monitoring or subsequent processing.

REFERENCES Alciatore, D. G., & Histand, M. B. (2012). Introduction to mechatronics and measurement systems

(4th ed.). New York, NY, USA: McGraw-Hill, ISBN 978-007-108604-2. Auslander, D., Ridgely, J., & Ringgenberg, J. (2002). Control software for mechanical systems:

object-oriented design in a real-time world. Upper Saddle River, NJ: Prentice Hall PTR. Bishop, R. H. (Ed.). (2002). The mechatronics handbook. Boca Raton, Florida, USA: CRC Press

LLC, ISBN 0-8493-0066-5. Harashima, F., Tomizuka, M., & Fukuda, T. (1996). Mechatronics—what is it, why and how.

IEEE/ASME Transactions on Mechatronics, 1(1), 1-4. Jouaneh, M. (2013). Fundamentals of mechatronics. Stamford, CT, USA: Cengage Learning, ISBN

978-1-111-56901-3.