H^∞ Control with Minor Feedback and its Application to a Pressure Control System

Abstract

The uncertainty model used in the H^∞ control is norm bounded, while the actual modeling error is not so in general, and hence such uncertainty model can be conservative in certain applications. Therefore, the resulting system performance might be conservative if we simply apply the H^∞ control scheme. An H^∞ control scheme with minor feedback is examined to reduce the conservativeness. Since the minor feedback loop changes both the nominal plant and the uncertainty models, we cannot conclude immediately that it improves system performances even if the magnitude of uncertainty model is reduced. A disturbance attenuation problem is discussed to investigate the effect of the minor feedback, and a sufficient condition is derived on which the minor feedback improves system performance. Experimental results for a pneumatic pressure control system confirm the effectiveness of the proposed method.