Reading material 1 Mechatronics

Introduction to mechatronics

Mechanical engineering, as a widespread professional practice, experienced a surge of growth during the early 19th century because it provided a necessary foundation for the rapid and successful development of the industrial revolution. At that time, mines needed large pumps never before seen to keep their shafts dry; iron and steel mills required pressures and temperatures beyond levels used commercially until then; transportation systems needed more than real horse power to move goods; structures began to stretch across ever wider abysses and to climb to dizzying heights; manufacturing moved from the shop bench to large factories; and to support these technical feats, people began to specialize and build bodies of knowledge that formed the beginnings of the engineering disciplines.

Now, more than a century later, we are witnessing a new scientific and social revolution known as the information revolution, where engineering specialization ironically seems to be simultaneously focusing and diversifying. This contemporary revolution was spawned by the engineering development of miniature semiconductor electronics, which have driven an information and communications explosion that has transformed human life. To practice engineering today, we must understand new ways to process information and be able to utilize semiconductor electronics within our products, no matter what label we put on ourselves as practitioners. The primary engineering disciplines of the 20th century-mechanical, electrical, civil, and chemical-retained their individual bodies of knowledge, textbooks, and professional journals because the disciplines were viewed as having mutually exclusive intellectual and professional territory. Entering students could assess their individual intellectual talents and choose one of the fields as a profession. That is all changing now as the impact of solid state electronics permeates the traditional fields of engineering both in the way engineers communicate and in what they design. Mechatronics is one of the new and exciting fields on the engineering landscape, subsuming parts of traditional engineering fields and requiring a broader approach to the design of systems that we can formally call mechatronic systems.

Then what precisely is mechatronics? The term mechatronics is used to denote a rapidly developing, interdisciplinary field of engineering that deals with the design of products whose function relies on the synergistic integration of mechanical, electrical, and electronic components connected by a control architecture.The word mechatronics was coined in Japan in the late sixties, spread through Europe, and is growing in use in the United States. The primary disciplines involved in the design of mechatronic systems include mechanics, electronics, controls, and computer science. A mechatronic system designer must assemble analog and digital circuits, microprocessors and computers, mechanical devices, sensors and actuators, and controls so that the final design achieves a desired goal. The subsequent chapters provide an introduction to these components and subsystems and describe aspects of their analysis and design.

More commonly you hear mechatronic systems referred to as smart devices. While the term smart is elusive in precise definition, in the engineering sense we mean the inclusion of elements such as logic, feedback, and computation which in a complex design may appear to simulate human thinking processes. It is not easy to compartmentalize mechatronic system design within a traditional field of engineering because such design draws from knowledge across many fields. The mechatronic system designer must be a generalist, willing to seek and apply knowledge from a broad range of sources. This may intimidate the student at first, but it offers great benefits for individuality and continued learning during one's career.

Today, there are very few mechanical devices that do not include electrical components and some type of computer monitoring or control.Therefore,the term mechatronic system encompasses a myriad of devices and systems. Increasingly, digital circuits and microprocessors are embedded in electromechanical devices, creating much more flexibility and control possibilities in system design. Examples of mechatronic systems include: an aircraft flight control and navigation system, automobile electronic fuel injection and antilock brake systems, automated manufacturing equipment such as robots and numerically controlled (NC) machine tools, smart kitchen and home appliances such as bread machines and clothes washing machines, and even toys.

An office copy machine is a good example of a contemporary mechatronic system. It includes analog and digital circuits, sensors, actuators, and micro-processors. The copying process works as follows: The user places an original in a loading bin and pushes a button to start the process; the original is transported to the platen glass; a high intensity light source scans the original and transfers the corresponding image as a charge distribution to a metal drum. Next, a blank piece of paper is retrieved from a loading cartridge, and the image is transferred onto the paper with an electrostatic deposition of ink toner powder that is heated to bond to the paper. A sorting mechanism then optionally delivers the copy to an appropriate bin.

Analog circuits control the lamp, heater, and other power circuits in the machine. Digital circuits control the digital displays, indicator lights, buttons, and switches comprising the user interface. Other digital circuits include logic circuits and microprocessors that coordinate all of the functions in the machine. Optical sensors and microswitches detect the presence or absence of paper, its proper positioning, and whether or not doors and latches are in their correct positions. Other sensors include encoders used to track motor rotation. Actuators include servo and stepper motors that load and transport the paper, turn the drum, and index the sorter.

Measurement systems

A fundamental part of many mechatronic systems is a measurement system that is composed of the three basic parts illustrated in Figure 1.1.The transducer is a sensing device that converts a physical input into an output, usually a voltage. The signal processor 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. Finally, the recorder is an instrument, a computer, a hardcopy device, or simply a display that maintains the sensor data for online monitoring or subsequent processing.

Figure 1.1 Elements of a measurement system

These three building blocks of measurement systems come in many types with wide variations in cost and performance. It is important for designers and users of measurement systems to develop confidence in their use, to know their important characteristics and limitations, and to be able to select the best elements for the measurement task at hand. In addition to being an integral part of most mechatronic systems, a measurement system is often used as a stand-alone device to acquire data in a laboratory or field environment.

Shown below (Figure 1.2) is an example of a measurement system. The thermocouple is a transducer that converts temperature to a small voltage; the amplifier increases the magnitude of the voltage; the A/D (analog to digital) converter is a device that converts the analog voltage to a digital signal; and the LEDs (light emitting diodes) display the value of the temperature.

Figure 1.2 Temperature measurement system