Jerk analysis and trajectory planning of a 3-(RRPRP)RS spaceborne stable platform

Parallel mechanism with sub-closed-loops is advantaged on compensating the nonlinear motions of carrier satellite due to their hybrid driving units. However, since the space Earth observation camera operates in a microgravity environment, higher requirements are placed on jerk characteristics and trajectory planning of spaceborne stable platform. In this paper, a kind of spaceborne stable platform with sub-closed-loops and a method for studying its jerk and trajectory planning are proposed. First, a 3-(RRPRP) RS mechanism is obtained based on the displacement manifold synthesis method, and its mechanism characteristics are analyzed. Besides, by applying the generalized jerk screws of sub-closed-loop unit, a general method for jerk analysis of such kind mechanism in non-inertial frame is proposed. Furthermore, the trajectory planning of stable platform is carried out with the goal of minimizing the jerk weighted square sum of drive joints and moving platform by using 7-order quasi-uniform B-spline curves and L-SHADE algorithm. Finally, taking 3-(RRPRP) RS mechanism and 6-UPS PM as numerical example, the proposed method is verified by comparing the results of theoretical calculation, simulation and experiment.