Feedforward and Feedback Methods for Active Control

A consistent framework is presented for the calculation of the optimal performance of feedforward and feedback control systems. in both cases the optimisation problem is transformed into a quadratic form using an internal model of one part of the physical system under control.This approach to feedforward control is fairly well known, but the controller architecture required for active control using feedback has only been recently recognised. it is known as lntemal Model Control (lMC) in the control literature and is widely used in H... control.The optimum performance of a feedback control system can thus be readily calculated using techniques already developed for feedforward control.The robustness of such a feedback controller can then be separately assessed using a generalisation of the complementary sensitivity function found in H... control theory.The robustness of a feedback controller can be improved by using various forms of effort weighting, which are already used for adaptive feedfomard controllers.By way of example, the performance is calculated of both feedforward and feedback controllers in actively attenuating road noise in cars.