Synthesis and Application of a Single Degree-of-Freedom Six-Bar Linkage With Mixed Exact and Approximate Pose Constraints

Existing research on synthesis methods for single degree-of-freedom (DOF) six-bar linkages mainly include four or five exact poses. However, an ideal trajectory cannot be synthesized using only five exact poses, thus, it is necessary to introduce additional poses to constrain the trajectory. If more exact poses are introduced, then the linkage may have no solution. Therefore, the constraints of the approximate pose are considered to make the trajectory conform to the desired trajectory. This paper successfully introduces mixed poses into a six-bar linkage, based on Z (Z < 5) exact poses and K approximate poses of a given error range, and a new synthesis method for single DOF six-bar linkages is proposed. The solution domain of the linkages synthesized by this method is wide and can be adjusted by controlling the error of the approximate poses, which reduces the difficulty of selecting the solution, ensures theoretical feasibility, and enables the trajectory of the final linkage to more closely match the ideal trajectory. Finally, for the coordinated training of multiple joints in human limbs, a rehabilitation device is designed based on the above six-bar linkage, and a prototype is developed and tested. The test results reveal the accuracy of the proposed method and the effectiveness of rehabilitation training.