Feedforward-feedback control logic for robust target-tracking

Feedforward compensation has for some time been recognized as a means for improving the ability of a control system to track the motions of a target. However, implementation requires target motion sensors, which may be costly. In addition, the control system is more complex and may be more sensitive to variations or uncertainties in the dynamic parameters of both plant and target. The question is thus raised as to whether a feedback-only control scheme can be designed that provides nearly as good performance with lower cost, less complexity, and reduced sensitivity. The circumstances are determined under which inclusion of feedforward compensation can be expected to offer enough performance gain to justify the cost of implementation. To this end, tracking error and control responses are analyzed and linear simulations are conducted to study the zero-placement mechanism by which feedforward and feedback compensation elements influence these responses in the presence of plant and target uncertainties.