Extended state observer/PID compound control for inertially stabilized platform

In order to improve the stability of inertial stabilized platform (ISP) control system for airborne remote sensing, a composite control algorithm combining the extended state observer (ESO) and PID is proposed. By using the ESO, all the internal and external disturbances are taken as the summed disturbances and measured out, and then the error feedback control is implemented by PID controller to improve the disturbance rejection ability and the stability accuracy of the control system. Simulations and experiments are conducted to verify the proposed method. In simulations, the LuGre friction model is introduced to represent the main disturbance; and in experiments, a self-developed three-axis ISP is applied. Experimental results show that the ESO/PD composite controller has excellent disturbances rejection ability and can significantly improve the stabilization accuracy of ISP. The RMS errors of the roll and pitch system by the ESO/PD method are decreased by 33.23% and 55.01% respectively compared to those by conventional PID controller.