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FLUID SYSTEMS Gases and liquids are collectively referred to as fluids. Fluid systems are used in many in- dustrial as well as commercial applications. For example, liquid level control is a well-known application of liquid systems. Similarly, gas systems are used in robotics and in industrial movement control applications. In this section, we shall look […]
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ELECTROMECHANICAL SYSTEMS Electromechanical systems such as electric motors and electric pumps are used in most indus- trial and commercial applications. Figure 2.19 shows a simple d.c. motor circuit. The torque produced by the motor is proportional to the applied current and is given by where T is the torque produced, kt is the torque constant […]
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ELECTRICAL SYSTEMS The basic building blocks of electrical systems are the resistor, inductor and capacitor (Fig- ure 2.13). The input to an electrical system may be the voltage, V , and current, i . The relationship between the voltage across a resistor and the current through it is given by The potential difference across a […]
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The task of mathematical modelling is an important step in the analysis and design of control systems. In this chapter, we will develop mathematical models for the mechanical, electrical, hydraulic and thermal systems which are used commonly in everyday life. The mathematical models of systems are obtained by applying the fundamental physical laws governing the […]
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SENSORS USED IN COMPUTER CONTROL Sensors are an important part of closed-loop systems. A sensor is a device that outputs a signal which is related to the measurement of (i.e. is a function of) a physical quantity such as temperature, speed, force, pressure, displacement, acceleration, torque, flow, light or sound. Sensors are used in closed-loop […]
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SOFTWARE REQUIREMENTS FOR COMPUTER CONTROL Computer hardware is nowadays very fast, and control computers are generally programmed using a high-level language. The use of the assembly language is reserved for very special and time-critical applications, such as fast, real-time device drivers. C is a popular language used in most computer control applications. It is a […]
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HARDWARE REQUIREMENTS FOR COMPUTER CONTROL General Purpose Computers In general, although almost any digital computer can be used for digital control there are some requirements that should be satisfied before a computer is used for such an application. Today, the majority of small and medium scale DDC-type applications are based on microcontrollers which are used […]
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CENTRALIZED AND DISTRIBUTED CONTROL SYSTEMS Until the beginning of 1980s, computer control was strictly centralized. Usually a single large computer or minicomputer (e.g. the DEC PDP11 series) was used to control the plant. The computer, associated power supplies, input–output, keyboard and display unit were all situated in a central location. The advantages of centralized control […]
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SCADA SYSTEMS The term SCADA is an abbreviation for supervisory control and data acquisition. SCADA systems integrate the data acquisition and system monitoring and control activities using graph- ical software packages. A SCADA system is nothing but a customized graphical applications program with all the necessary hardware components. It can be developed using the popular […]
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COMPUTER IN THE LOOP Most control engineering applications nowadays are computer based, where a digital computer or a microcontroller is used as the controller. Figure 1.3 shows a typical computer controlled system. Here, it is assumed that the error signal is analog and an A/D converter is used to convert the signal into digital form […]
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