Inertial stability control method for the task space of inertially stabilized platform for spherical mechanism

The spherical mechanism inertially stabilized platform (ISP) offers significant advantages, including enhanced motion flexibility and superior space utilization efficiency. The joint space control (JSC) of such systems involves computationally intensive processes and fails to fully mitigate multisource disturbances. In order to further improve the performance, this paper proposes a double-loop disturbance observer (DLDOB) method in the task space. There are three main parts of this control method. The first portion is designed as a gravity compensation controller in order to solve the problem of unbalanced gravity distribution caused by the asymmetric structure of the spherical mechanism. The second portion is the main controller of the system, which is the DLDOB. It includes the disturbance observer (DOB) in the joint space and the adaptive sliding mode disturbance observer (ASMDO) in the task space. This method simplifies the computationally intensive joint-to-task space transformation process. It estimates and compensates for system disturbances in both joint and task spaces, thereby improving system robustness. The third portion is a velocity feedback controller, which ensures the inertial stabilization control of the ISP. To verify the effectiveness of the proposed method, the stability of the control system was proven in the paper using the Lyapunov method. Besides, simulations and experiments were carried out. It was verified that the proposed method has stronger disturbance rejection and stabilization performance compared with the conventional method.