Type Synthesis of Six Degrees of Freedom Parallel Mechanism with Decoupled Translation and Rotation

Abstract

AbstractA type synthesis method of six degrees of freedom (DOFs) parallel mechanism (PM) with decoupled translation and rotation (DTR) is proposed by analyzing the input and output characteristics of partially decoupled parallel mechanism (PDPM). Firstly, based on the requirements of Jacobian matrix of PDPM, the direct Jacobian matrix and inverse Jacobian matrix are constructed by the screw theory, so as to determine the actuation wrench screw (AWS) that represents the force or couple acting on the moving platform by the actuated twist screw (ATS) of the limb. According to the AWS and the connectivity, the ATS representing the driving pair and the non-actuated twist screw (NATS) representing the non-driving pair on the corresponding limb are obtained, and then the configuration of the limb structure screw system is completed. Finally, according to the limb combination principle of PDPM, six limbs are selected in turn to connect the moving platform and the fixed platform, and then a variety of six DOFs PMs with DTR are obtained. The six DOFs PM with DTR can be used as the main structure of the joint rehabilitation robot, which provides an idea to solve the problem that the rotation center of the robot joint is inconsistent with the actual physiological center of human joint. This kind of mechanism has the characteristics of compact structure and simple control that shows wide application prospects.KeywordsType synthesisParallel mechanismPartially decoupledActuation wrench screw