2025-08-08
Proportional term P, differential term D and integral term I--- their respective characteristics.
Increase proportional gain (
), the control signal can be increased or decreased in proportion to the error signal (e(t)). If only proportional control is used and it is fixed
The only way to increase the control signal is to increase the error.
With differential control, if the error inclines upward (that is, the error slope is large), the control signal will become very large even if the amplitude of the error is still small. This prediction function is like increasing the damping of the system, so it can reduce overshoot. The addition of differential term has no effect on steady-state error.
Adding an integral term to the controller (
), which helps to reduce the steady-state error. If there is a constant steady-state error, the integral will continue to act, thus increasing the control signal and reducing the error. Disadvantages of integral term: it will make the system slow (and oscillate), because it takes some time to counteract the effect when the error changes sign.
Each paramete of that controller (
) The general function of closed-loop system is listed in the figure below. The following functions are established in many cases, but they are not absolute. If you really want to know the effect of adjusting each gain, you have to do more analysis or test the actual system.
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