Synthesis of Multi-position 3-PRS Manipulator Based on Spherical Constraints by Eliminating the Parasitic Motion

This paper presents synthesizing procedure for eliminating the parasitic motions of a three-prismatic-revolute-spherical manipulator. The parasitic motions can occur due to constrained mobility of the manipulator. The three constrained variables of manipulators are rotational freedom along z-axis and two degrees of translational freedom about x- and y-axis of the fixed frame. The parasitic motions are usually nonzero and are determined by the geometrical parameters of the manipulator. These parasitic motions cause crucial problems in some cases. In general, the amplitude of parasitic motions is very small but shows more impact on precision of motion, quality and accuracy of the mirror images of 3-PRS manipulator. To prevent these undesirable parasitic motions, the synthesized architectural parameters of 3-PRS manipulator are identified by eliminating the parasitic motions. The prospective application of this manipulator is in mirror image telescopic process. The synthesis of this manipulator involves the determination of the dimensions of the manipulator such that a point on the mobile platform passes through a prescribed set of positions in space. In this paper, the physical restrictions on range of motion of spherical joints are considered by introducing the limits on rotational motion of cone angle of spherical joints to determine the dimensions of the fixed frame of a three-prismatic-revolute-spherical manipulator. This research aim is to eliminate all parasitic motions, and the procedure committed for multi-positions of a three-prismatic-revolute-spherical manipulator. The synthesis of the manipulator is carried out by approximate-method using least-square technique. © 2022, The Institution of Engineers (India).