Control of Linear Systems by Output Proportional Plus Derivative Feedback

This paper presents a design procedure for linear time invariant systems using output proportional plus derivative feedback. The derivative feedback is shown to improve the controller performance in the presence of parameter variations and disturbance inputs, at the cost of increased noise response. A quadratic performance index, with the addition of terms to penalize disturbance and noise response and eigenvalue and response sensitivity, is used as the basis for a design method. The proposed method is a generalization of one presented previously for the case of perfect state and state derivative feedback. The method is illlustrated on a simple first order example and on the design of a controller for the lateral dynamnics of an L1011 aircraft. The results indicate that improved performance is obtained through the addition of perfect output derivative feedback, however, much of that improvement is lost when approximate differentiation is used.