Actuator Fault Tolerant Control Proposal for PI Controlled SISO Systems

Abstract

In this work, we develop a control structure which can be added to an existing closed loop in order to mitigate the effect of actuator faults. We analyze the initial performance of the closed loop in terms of robustness and time response under references, faults and measurement noises. In the design of the proposed active fault tolerant control structure, we keep the initial robustness and time response to references. At the same time, we try to improve some performance indices under faults at the cost of a higher control action activity caused by the measurement noises that affect the system. The design of the controller depends on a unique parameter so it can be easily understood. We show that although the response under step faults becomes oscillatory, the active fault tolerant structure reduces the integral of the absolute value of the tracking error under step faults and it attenuates the effect of ramp faults in steady state. Several examples show the goodness and drawbacks of the approach and show some aspects to be considered in the design.