The design of reliable adaptive controllers for time-varying delayed systems based on improved H∞ performance indexes

The method of designing a reliable adaptive H∞ controller for a time delayed linear system is addressed in this paper. In the case of the existence of actuator faults in the system, improved performance indexes are proposed to describe the influence of the disturbances and time delays on the system. On the basis of the online estimates of actuator faults, the designed adaptive controller parameters are updated automatically to compensate the actuator faults influence on system while making sure optimum of the adaptive H∞ performance indexes with time delay in both fault-free and fault cases for the closed-loop system. The sufficient conditions of asymptotic stability are obtained. In spite of their simple structure, they are proved to be less conservative than those of fixed gains controller. Finally, one numerical example is given to prove that the proposed designed method in this paper is less conservative than previous methods, one numerical example is given to illustrate the effectiveness of the method for not only time-delayed systems but also systems without time delay, and a rocket fairing structural-acoustic system is considered to verify the effectiveness of this method.