Kinematics analysis and design of 4PC-2R parallel mechanism

With the rapid development of new energy vehicle industry, the energy supply efficiency of a heavy electric truck becomes a key factor that restricts its wide application. This paper proposes a new 3T1R parallel mechanism with movement as its motion input, which can be used in the fast power exchange of the heavy electric truck. The 2-PCR parallel mechanism is modeled with the SolidWorks software. Its degrees of freedom are examined with the helix theory and validated with the modified G-K formula. The kinematics is solved primarily with the closed-loop vector method. The Matlab is employed to graphically determine the mechanism′s working space. The results indicate the mechanism possesses 4 degrees of freedom, 3 translations across the X, Y and Z axes and 1 rotational degree of freedom around the Z axis. The movement in the Y and Z directions is independent, and the freedom of rotation around the Z axis interferes with the movement in the X direction. The output point can not only move in the X direction but also drive its rotational angle when it moves in the X direction. Based on this mechanism, the 4PC-2R parallel mechanism is proposed for further optimization. The comparison of the two mechanisms shows that the 4PC-2R parallel mechanism is smoother. Finally, the mechanism′s parameters are refined with the genetic algorithm so as to expand the working space of the 4PC-2R mechanism. The practical application of the 4PC-2R parallel mechanism demonstrates that it has a streamlined structure, an expansive operational range and fluid motion characteristics, thus being safer and more effective for a heavy electric truck′s power exchange.