PDD205A1121 3BHE025335R1121 控制板模块 主控板

PDD205A1121

Different from open loop control system
Compared with open-loop control system, closed-loop control has a series of advantages. In a feedback control system, no matter for what reason (external disturbance or internal change of the system), as long as the controlled quantity deviates from the specified value, the corresponding control effect will be generated to eliminate the deviation. Therefore, it has the ability to suppress interference, is not sensitive to changes in component characteristics, and can improve the response characteristics of the system. However, the introduction of feedback loop increases the complexity of the system, and improper gain selection will cause instability of the system. In order to improve the control accuracy, when the disturbance variable can be measured, the feedforward control is often used as a supplement to the feedback control to form a composite control system.
Generally speaking, open loop control system structure is relatively simple, low cost. The disadvantages of open loop control system are low control precision, poor ability to suppress interference, and more sensitive to the change of system parameters. Generally used without considering the external influence or precision requirements of the occasion, such as washing machine, stepper motor control device and water level regulation system. [4]
In a closed-loop control system, no matter the change of input signal, or the influence of interference, or the change of internal parameters of the system, as long as the controlled quantity deviates from the specified value, the corresponding effect will be generated to eliminate the deviation. Therefore, the closed-loop control has strong ability to suppress interference. Compared with open-loop control, the system is not sensitive to parameter changes, so less precise components can be selected to form a more precise control system to obtain satisfactory dynamic characteristics and control accuracy. However, the use of feedback device needs to add components, which is relatively high cost and also increases the complexity of the system. If the structural parameters of the system are not properly selected, the control process may become very poor, and even appear unstable situations such as oscillation or divergence. Therefore, how to analyze the system, reasonably choose the structure and parameters of the system, so as to obtain satisfactory system performance, is the automatic control theory must study and solve the problem.