Dynamic Model and Line of Sight Control of a 3-DOF Inertial Stabilization Platform via Feedback Linearization

Abstract

The majority of works with inertially stabilized platforms (ISP) apply linear controllers to achieve a satisfactory stabilization performance of the line of sight (LOS). Typically, a double integrator with an inertia gain is used to describe the relationship between torque and position of the ISP joints, which are considered decoupled. Then, a control topology with an inner PI velocity loop and an outer P position loop (P-PI control), is employed to reject the disturbances originated from the base motion and other unmodeled dynamics. Although this approach suffices for many practical applications, better performance could be achieved if more sophisticated models and control strategies were used. This paper addresses the problem of modeling and controlling the LOS of a camera in a 3-DOF ISP installed on a vessel using the Newton-Euler (NE) formulation for vehicle-manipulator systems (VMS). The obtained model takes into account non-trivial dynamic effects of multibody systems, such as the motion of the ISP base. Using this model, feedback linearization via computed torque (CT) plus PID (CTPID) strategies are proposed to control the LOS. Simulations analyze the robustness of the control with respect to parametric errors and its effectiveness when compared to the common P-PI control strategy used in LOS stabilization.