ABSTRACT
This chapter introduces the principles of feedback control systems and illustrates their characteristics and advantages. Feedback is the process of measuring the controlled variable and using that information to influence the controlled variable. An open-loop control system utilizes a controller and actuator to obtain the desired response without monitoring the actual system response controlled variable. In contrast to an open-loop control system, a closed-loop control system utilizes an additional measure of the actual output to compare the actual output with the desired output response. The model of the cruise control system for a car can be established in a relatively simple fashion. The car's cruise control system considered so far has been open-loop. There is no use of a sensor and hence there is no feedback of sensor information to correct errors in the car speed. A closed-loop car's cruise control system engages a speed measuring sensor, the speedometer, to measure the actual car speed.
