A Spheroid Parallel Wrist Mechanism and Its Kinematic Analysis

Based on the 2-DOF (degree of freedom) spherical parallel Omni-Wrist V, a 3-DOF 2R1T (2 rotational and 1 translational) spheroid parallel mechanism is proposed by the configuration evolution method, and its kinematic analysis is systematically carried out. The DOF of the proposed mechanism is first analyzed with an atlas method based on constraint theory. An equivalent kinematic model is then established, the forward and inverse kinematic equations are derived in an analytical form, and its singularity is discussed. Finally, the workspace is generated by Monte Carlo method, and a 3D cutting method is proposed to analyze its characteristics. In the workspace analysis, the slice area and shape generated by level cutting are used to measure the rotational manipulability, and the radial displacement of sector piece generated by cutting slice with a fixed tilt angle is defined to evaluate the translational manipulability. The presented parallel mechanism can be used as a wrist at the end of Delta or SCARA (selective compliance assembly robot arm) robots, to form hybrid robots for electronic and light industries where large change of the object configuration (orientation and position) is to be performed.