The internal model control design of three-axis inertially stabilized platform for airborne remote sensing

Inertially stabilized platforms (ISPs) are used to stabilize and maintain the line-of-sight (LOS) of a real-time motion imaging payload in high resolution airborne earth observation system in inertial space. The most critical performance for an ISP is the capability to reject disturbances such as friction and mass imbalance. These disturbances usually can not be suppressed precisely in a typical control system depending on the closed-loop bandwidth which is directly affected by the structural resonance, noise coupling from the gyro and so on. In this paper the stabilization loop disturbance rejection strategy based on an internal model control (IMC) method is proposed and some conventional control methods are briefly reviewed. Firstly, the mathematical modeling of a single-axis gimbal system is carried out and the characteristic of main torque disturbances acting on ISPs' gimbals are introduced accordingly. The exosystem is used to describe the common antistable parts of both reference input and disturbances. And then the procedures of designing an IMC controller are illustrated in detail and the performance of the stabilization closed-loop is analyzed such as the capability of disturbance rejection and robustness against model uncertainties. Finally, the experimental results demonstrate the effectiveness and superiority of the proposed strategy in comparison to the traditional control method.