ABSTRACT
Controlling system behavior is an important necessity for practical systems. No matter how well a system is designed, its response (or system output) is not always exactly what was desired or expected. Also, external disturbances can affect the system; and its behavior, as a result, may change from what was desired. Hence, it is necessary to have a control system that will adjust system behavior by altering the input so that the desired output is achieved. There are some simple control techniques, such as a “bang-bang” (on/off) control, which are of limited use. The most well-known and useful technique is feedback control, where the response of the system is monitored and compared with the expected response, and the error in the response is used to alter the input dynamically to achieve the desired result. The block diagram in Figure 11.1 shows a schematic of the feedback control system. The system’s (or plant’s) response is subtracted from the set point to obtain the error. The error signal is used in a control algorithm to determine the system input that is fed into the system, and the response is adjusted, as a result, to achieve the desired output.
