Sliding mode control in a two-axis gimbal system

This paper considers the performance of a two-axis gimbal system, which is typical of surface-to-air, air-to-air, and air-to-surface tactical missiles, when Sliding Mode Control is utilized. A representative gimbal system consisting of a flat planar antenna, pitch/yaw gimbals, connecting push rods, and separate armature controlled DC drive motors for the pitch and yaw gimbals is utilized to develop the theory and to serve as a testbed for digital simulation. The equations describing the gimbal system under consideration are highly nonlinear and include terms which are not accurately known or can not be accurately measured during the missile's flight. It is shown that the use of variable structure control or sliding mode control can be used to provide robust seeker performance in the face of nonlinearities and uncertainties.