(1) Select the controller according to the characteristics of the controlled object
When using the analog controller, because the characteristics of the application of the industry is not the same, such as the object is very sensitive, or accused of traffic is often pulsating state, it should not be used to differentiate the function, otherwise it will make the pulse signal changes Intensified. And then there is intermittent or intermittent production control process has its particularity. So the controller selection is a more complex problem, usually requires the characteristics of the controlled object to select the controller. For experienced instrument workers are mostly in accordance with their own practical experience to determine the choice of the controller. And the PID controller is the most used, because it can solve most of the control problems.
(2) select the positive and negative effects of the controller
The positive and negative effects of the analog controller are determined by its positive / negative switching position. The digital controller is determined by either the forward / reverse switch position, or by software. The positive and negative effects of the controller are relative to the controlled variable, and the positive and negative effects of the controller are judged in the pure proportional state. If the input variable of the controller is increased and the output of the controller is increased, we say that the controller is in the positive state. If the controller's control variable is increased and the output of the controller is reduced, status. Positive / negative switch is set to correct? Judgment is based on whether the entire control system is a negative feedback system. Any closed-loop control system is composed of the transmitter, the controller, the regulating valve and the controlled object. Therefore, it is judged that the positive and negative reaction of the controller should be judged by the negative product of the enlargement coefficient of the four links The
(3) Do not ignore manual switching of manual switching
When the control system is started, care should be taken to place the control system in the manual position, and the controller has a larger output by hand so that the measured value of the controlled parameter can be close to the given value. Before the measured value approaches and reaches the given value, the manual signal should be slowly adjusted to prevent the overshoot from occurring, and when the measured value is equal to the given value, the manual position can be switched from the manual position to the automatic position. So that the output of the controller will not be mutated, but also to enter the PID control state smoothly.
(4) carefully do the controller tuning parameters
The control system can be stable in the automatic operation state, and the controller PID parameter tuning has an important relationship.
