Motion Principle of New Parallel Mechanisms With Fewer Active Inputs Than the DOFs and Its Pose Adjustment Optimization

The proposed parallel mechanisms (PMs) differ from conventional PMs in that they can achieve the same mobility with fewer active joints. The general motion principle of the proposed new mechanism has been proposed. Based on the Newton iterative method and neural network approaches, a method is put forward to obtain the continuous forward solution for the new PMs. Since the posture adjustment of the moving platform is realized through the active branch adjusting the passive branches one by one in sequence, the adjustment sequence of passive branches and step size of the passive branch in each adjustment for any end posture of the new PM is optimized, with the workspace as the constraint and minimizing the number of adjustment times as the goal. The structure of the 7SPS is designed and prototype experiments are conducted. Experiment results have shown that the proposed PM can achieve the original mobility while significantly reducing the number of actuators.