Open loop control system
An open loop control system is a system that outputs only a feedback loop that is controlled only by system inputs. In the open loop control system, information about the value of the controlled amount is not used to constitute a control action in the control process. The characteristic is that the control device commands the actuator to change the working state of the controlled object, and the controlled amount changes accordingly, and the change does not constitute the cause of the action of the control device again, that is, the control signal and the controlled amount There is no feedback loop between them. In order to choose a control force, it is important to use information about the effect of the disturbance on the controlled quantity, rather than the information about the disturbance itself. Therefore, it is possible to organize a control without directly measuring the disturbance. It is only necessary to monitor the deviation caused by the disturbance to the controlled system. Thus, the control signal can also be generated from information that is controlled to deviate from its predetermined value. All manual control, most program control and CNC machine tools, and time program control are open loop controls. As shown in the figure, the input of such a system directly controls its output. Its simple device and low cost can eliminate the stability problems existing in many closed-loop control systems. Before the disturbance has a certain degree of influence on the value of the controlled system, the control force changes directly according to the change of the disturbance. However, its anti-interference ability is poor, so its control effect is greatly limited, and the accuracy is lower than that of the closed-loop control system.