SCPR: A Slider–Crank-Inspired 2R1T Parallel Robot Enables High Orientation Capability Without Parasitic Motion

Abstract

For parallel robots with two rotations and one translation, a great design challenge is to achieve high orientation capability while eliminating undesired parasitic motion. To cope with it, this study proposes and develops a slider–crank-inspired parallel robot. This novel mechanism follows a seven-stage evolutionary process originally from planar slider–crank mechanisms, sticking to three major design principles (symmetrical design, actuation redundancy, and articulated moving platform). Several slider–crank mechanisms with a centric layout are adopted to obtain zero crank angle and are arranged symmetrically and redundantly, which brings a large orientation workspace without singularity and high-quality transmission performance. By using an articulated platform, the adopted centric slider–crank mechanisms share one common rotation center to eliminate parasitic motion. Furthermore, all the kinematic pairs are single-degree-of-freedom joints—except for four active prismatic joints, the remains are revolute joints—that can reduce interference. Theoretical and experimental results lead to several major conclusions: 1) the built robot exhibits an outstanding orientation capability, capable of tilting up to 70° in all directions; 2) the articulated moving platform can rotate exclusively about one point, demonstrating zero parasitic motion; and 3) the robot possesses simple forward and decoupled kinematics, partially attributed to the simplicity of slider–crank mechanisms.