Design of a 6-DOF Heavy-Duty and High-Precision 3–3 Orthogonal Parallel Robot With Flexible Hinges

Abstract

Parallel robot is important in high-precision application. The current studies focus on the high-precision robot with light payload capability. It is insufficient for the support of a space optical telescope. When designing a robot with a large payload, performance redundancy of the robot needs to be reduced because the high payload and precision will cause high cost. In this paper, a six degrees-of-freedom heavy-duty and high-precision 3–3 orthogonal parallel robot with flexible hinges is presented. A performance redundance minimization-based type selection method is proposed by the isotropy comparison. The performance of between Stewart and orthogonal mechanisms is compared based on local transmission index, force and torque payload isotropy, displacement, and rotation accuracy isotropy. A performance mean maximization and standard deviation minimum dimensional optimization method is proposed. Two new indexes named payload distribution index and accuracy distribution index are proposed to evaluate the performance redundancy of the mechanism. The mechanism parameters are designed based on performance atlas using workspace volume index, global transmission index, global payload index, global accuracy index, payload distribution index, and accuracy distribution index. A new modeling method considering the nun-functional motion of spherical joints with stiffness compensation is proposed. Modeling and control experiments on the robot demonstrate the effectiveness of the proposed method.