Kinematics of a 3-DOF parallel manipulator with an R-P-S joint structure

A new solution of the inverse kinematics task for a 3-DOF parallel manipulator with a R-P-S joint structure is obtained for a given position of end-effector in the form of simple position equations. Based on this the number of the inverse kinematics task solutions was investigated, in general, equal to four. We identify the size of the manipulator feasible area and simple relationships are found between the position and orientation of the platform. We prove a new theorem stating that, while the end-effector traces a circular horizontal path with its centre at the vertical z-axis, the norm of the joint coordinates vector remains constant.