Dynamic Modeling and Analysis of a 2PRU-UPR Parallel Robot Based on Screw Theory

Xinxue Chai,Lingmin Xu,Min Wang,Wei Ye

doi:10.1109/access.2020.2989783

Abstract

This paper proposes the systemic dynamic modeling and analysis of a 2PRU-UPR parallel robot with two rotations and one translation based on screw theory, where P, R and U denote prismatic, revolute and universal joints, respectively. Compared with existing parallel robots having two rotations and one translation, the two actuated prismatic joints of the 2PRU-UPR parallel robot are mounted on a fixed base to reduce the movable mass and improve the dynamic response. First, the inverse kinematics are presented. Next, adopting the screw-based method, the velocity and acceleration of joints and limbs of the 2PRU-UPR parallel robot are analyzed in detail. The actuated forces of the three actuators are then obtained according to the principle of virtual work. Additionally, a numerical simulation is conducted using ADAMS software to investigate the dynamic model of the 2PRU-UPR manipulator and to verify the correctness of the theoretical results. Finally, distributions of the dynamic manipulability ellipsoid index are used to evaluate the dynamic translational and rotational performances of the 2PRU-UPR parallel robot. A prototype based on the dynamic analysis has been fabricated. The dynamic modeling and evaluation provide a basis for the efficient and precise control of the 2PRU-UPR parallel robot in actual machining manipulations. The 2PRU-UPR parallel robot has great potential in machining workpieces with curved surfaces.

Highlights

Parallel robots have been intensively studied over past decades and used in many applications, from simple pickand-place operations to advanced electronic manufacturing [1]–[3]
Dynamic modeling plays an important role in the predesign stage of the development of parallel robots and is essential for dynamic performance analysis and parameter optimization
The dynamic analysis of parallel robots is carried out adopting several methods, mainly the Newton–Euler method [12]–[16], Lagrange method [17]–[21] and the adoption of the virtual work principle [22]–[26]

Summary

INTRODUCTION

Parallel robots have been intensively studied over past decades and used in many applications, from simple pickand-place operations to advanced electronic manufacturing [1]–[3]. X. Chai et al.: Dynamic Modeling and Analysis of a 2PRU-UPR Parallel Robot derivation of constrained forces/moments. Chai et al.: Dynamic Modeling and Analysis of a 2PRU-UPR Parallel Robot derivation of constrained forces/moments Such an energy approach for the analysis of a parallel robot can be simplified applying screw theory [31]–[35]. Adopting screw theory and the virtual work principle, this paper presents the systemic dynamic modeling and analysis of the three-degree-of-freedom (3-DOF) 2PRU-UPR parallel robot with two rotations and one translation (2R1T) [39]. In evaluating the dynamic performance of the 2PRU-UPR parallel robot, the present paper employs the dynamic manipulability ellipsoid (DME) [2], [42]–[44] to depict manipulability, namely the ease with which the position and orientation of the manipulator’s moving platform can be changed.

SCREW THEORY BASICS

VIII. CONCLUSION