What does the PID on heat treatment equipment mean? Factory Suppliers Manufacturers Quotes

What does the PID on heat treatment equipment mean?

PID controller is based on the system error, using the ratio, integral, differential calculation control.


Proportional (P) control: proportional control is the simplest form of control. The output of the controller is proportional to the input error signal. Steady-state error exists in system output when only proportional control is available.


Integral (I) control: in integral control, the output of the controller is proportional to the integral of the input error signal. For an automatic control System, if there is a Steady state Error after entering Steady state, the System with steady-state Error is called. In order to eliminate the steady state error, the "integral term" must be introduced in the controller. The integral over the error depends on the time integral, and as time goes on, the integral increases. In this way, even if the error is small, the product term will increase with the increase of time, which will push the output of the controller to increase and further reduce the steady state error until it is close to zero. Therefore, the proportional + integral (PI) controller can make the system almost stable after entering steady state.


Differential (D) control: in differential control, the output of the controller is proportional to the differential of the input error signal (i.e., the rate of error change). The automatic control system may oscillate or even become unstable in the process of overcoming the error. The reason is that there is a large inertial component (link) or delay component, which has the function of suppressing error, and its change always lags behind the change of error. The solution is to "lead" the change in the effect of the suppression error, that is, when the error is close to zero, the effect of the suppression error should be zero. That is to say, in the controller only to introduce "ratio" is often not enough, the role of proportional is only amplified amplitude error, and the need to increase the "differential", it can predict error change trend, so has the proportion + differential controller, can early enough that the control action of inhibiting error is equal to zero, even negative, so as to avoid the serious overshoot of the amount of the accused. Therefore, for controlled objects with large inertia or hysteresis, the proportional + differential (PD) controller can improve the dynamic characteristics of the system in the process of adjustment.

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