New type of controller: the proportional integral minus delay controller

In the design of a control system, the derivative controller is often required to obtain a quick response. However, when the control system is subject to noise inputs, the functioning of the derivative controller may be jeopardized owing to its sensitivity to high-frequency noise. In order to overcome this problem, a new type of controller, called the proportional-integral-minus-delay (PIMD) controller is proposed in this paper. It is shown that in addition to exhibiting almost the same characteristics as the conventional proportional-plus-integral-plus-derivative (PID) controller, the PIMD controller is less sensitive to high-frequency noise. It seems that an appropriate PIMD controller would be a good replacement for a PID controller. The output time responses of the closed-loop system with a PIMD controller and the frequency-response characteristics of a PIMD controller are obtained by computer simulation.