Missile autopilot design using discrete-time variable structure controller with sliding sector

In this paper a discrete variable structure controller with sliding sector is designed for tracking the lateral acceleration command for a dual-input air-to-air missile. A new algorithm is developed for the variable-width sliding-sector design by considering the dissipativeness property of the system. The width of the sliding sector is based on the norm of the linear uncertain system state and the reference input. The switching surface design is based on the reduced-order dynamics. The control law is designed such that the state trajectory from any initial point is driven into the sliding sector around the equilibrium point in the vicinity. of the the switching surface sigma(k) and thereafter remains inside it. The discrete sliding condition considered is parallel tosigma(k+1)parallel to < parallel tosigma(k)parallel to. inside the sliding sector, the closed-loop system is dissipative with a linear control law. The uncertain missile plant with matched and mismatched uncertainty is considered, and the conditions on the norm-bound of the uncertainty are given for robust stability in the sense of Lyapunov. Simulation results of the missile autopilot are also included to show the efficacy of-the proposed controller.