Design of Decentralized Two Loop Cascade Control Strategy for 3-Axis Platform Stabilization

This paper proposes a two loop decentralized cascaded control strategy with aim of achieving guaranteed tracking performance of a 3-DOF Inertial Stabilized Platform in presence of disturbance. A 3-DOF platform is generally used in airborne systems for providing a stable line of sight (LOS) for tracking purposes. The present work focuses on stabilizing the 3-DOF platform by a decoupling action that suppresses the torque disturbances acting between the gimbals. With an objective to stabilize the central platform at any desired reference position, the proposed approach uses a two-loop methodology where the inner loop rejects the disturbances while the outer loop effects the LOS tracking. The PID controller is used in both inner and outer loops, the gains of the which are tuned by minimizing a performance index with the Genetic Algorithm. The effectiveness of the proposed strategy is established from the simulation responses that highlight its disturbance rejection capability in all the axes while tracking step and sinusoidal reference signal.