TAILIEUCHUNG - ebookModern Control Technology--Components & Systems (2nd Ed.)p1

| MLMAA Modern Control Technology Components and Systems 2nd edition Kilian CHAPTER 1 Introduction to Control Systems OBJECTIVES After studying this chapter you should be able to Distinguish between open-loop and closed-loop control systems. Understand control system block diagrams. Explain transfer functions. Differentiate between analog and digital control systems. Know how process control systems work. Know how servomechanisms work. INTRODUCTION A control system is a collection of components working together under the direction of some machine intelligence. In most cases electronic circuits provide the intelligence and electromechanical components such as sensors and motors provide the interface to the physical world. A good example is the modern automobile. Various sensors supply the on-board computer with information about the engine s condition. The computer then calculates the precise amount of fuel to be injected into the engine and adjusts the ignition timing. The mechanical parts of the system include the engine transmission wheels and so on. To design diagnose or repair these sophisticated systems you must understand the electronics the mechanics and control system principles. In days past so-called automatic machines or processes were controlled either by analog electronic circuits or circuits using switches relays and timers. Since the advent of the inexpensive microprocessor more and more devices and systems are being redesigned to incorporate a microprocessor controller. Examples include copying machines soft-drink machines robots and industrial process controllers. Many of these machines are taking advantage of the increased processing power that comes with the microprocessor and as a consequence are becoming more sophisticated and are including new features. Taking again the modern automobile as an example the original motivation for the on-board computer was to replace the mechanical and vacuum-driven 1 2 CHAPTER 1 subsystems used in the distributor

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