Continuous second-order sliding mode control based on disturbance observer for LOS stabilized system

This paper develops a continuous second-order sliding mode control based on finite-time disturbance observer for light of sight (LOS) stabilized loop of inertial stabilized platform. The main purpose of an inertial stabilized platform is to eliminate the various disturbances to make the LOS keep steady in an inertial space. To accomplish the controller design, the equations of motion for a 2-DOF gimbal system driven by permanent synchronous motors are established and the cross coupling torque, mass unbalance torque, uncertain load torque are treated as the lumped disturbances. And to improve the tracking accuracy, a new continuous sliding mode control approach is employed to control the rate loop of the system. The proposed method confirms that the tracking error of LOS rate converges to zero in finite time even in the presence of the disturbances. By using the Lyapunov function technique, a rigorous finite-time convergence proof is given. The comparison simulation results show that the proposed method for LOS stabilized system exhibits a promising control performance in practical engineering.