The Control System

This chapter presents the control system and its functions, types, examples, and representation of the process control systems. A control system is a system that regulates, directs, commands, and manages the performance of other sub-systems using a control loop. Basically, there are two major types of control systems, viz; the open and closed loop control systems. For the open loop control system, control action is independent of the desired output. This control system is referred to as a non-feedback control because of the absence of a feedback path. Although they are simple in design and relatively inexpensive but are less accurate compared to the closed-loop control system. On the other hand, for the closed-loop control system, control action is a function of the desired output. This control system is referred to as feedback control because of the presence of the feedback path. Although it is complex in design and expensive but more accurate compared to the open loop control system. To enhance the performance of basic controls, many modern systems incorporate advanced controls such as advanced regulatory controls, advanced process controls, multivariable predictive control, non-linear multivariable predictive control, fuzzy logic control, inferential measurements, etc. Advanced controls are a set of technologies employed to address a specific control deficiency in a system. While the basic controls facilitate the control of a system’s basic operations, advanced controls are incorporated to enhance the performance of the basic controls.