Optimal design and verification of the 6-DOF Stewart structure used in vehicle-mounted automatic assembly

Abstract

The Stewart structure with six degrees of freedoms (6-DOF), which has the advantages of big bearing capacity, strong stiffness and high accuracy, has been widely used in the indoor automatic assembly of aeronautics and astronautics. In this paper, a novel design method for the Stewart structure with limited installation space is proposed to extend the workspace by parameter optimization using genetic algorithm, and the performance is further verified via co-simulation. Firstly, the target function, which describes the workspace that satisfies both kinematic and dynamic constraints, is built with four parameters: the joints circle diameters and the angles between adjacent joints of both bottom and top platforms. Subsequently, the genetic algorithm is used to optimize the target function with the four parameters whose bounds are limited by vehicle-mounted installation space and structure interference. Finally, the geometry model is built in LMS. Motion and is studied using co-simulation method with the hydraulic system in AMEsim and control system in Simulink. With the cylinders motion accuracy within ±0.5 mm, the final position of top platform is consistent with the theoretical calculations, and the position error could be controlled within ±0.7 mm.