Hệ thống điều khiển tự động là một hệ thống kiểm soát closedloop cài sẵn mà không yêu cầu phải hành động điều hành. Này giả định quá trình này vẫn còn ở mức bình thường cho các hệ thống điều khiển. | Automatic Control System An automatic control system is a preset closed-loop control system that requires no operator action. This assumes the process remains in the normal range for the control system. An automatic control system has two process variables associated with it: a controlled variable and a manipulated variable. A controlled variable is the process variable that is maintained at a specified value or within a specified range. In the previous example, the storage tank level is the controlled variable. A manipulated variable is the process variable that is acted on by the control system to maintain the controlled variable at the specified value or within the specified range. In the previous example, the flow rate of the water supplied to the tank is the manipulated variable. Functions of Automatic Control In any automatic control system, the four basic functions that occur are: Measurement Comparison Computation Correction In the water tank level control system in the example above, the level transmitter measures the level within the tank. The level transmitter sends a signal representing the tank level to the level control device, where it is compared to a desired tank level. The level control device then computes how far to open the supply valve to correct any difference between actual and desired tank levels. Elements of Automatic Control The three functional elements needed to perform the functions of an automatic control system are: A measurement element An error detection element A final control element
