Abstract
This paper first designs a new 5-DOF parallel mechanism with 5PUS-UPU, and then analyses its DOF by traditional Grubler–Kutzbach and motion spiral theory. It theoretically shows that the mechanism meets the requirement of five dimensions of freedoms including three-dimensional movement and two-dimensional rotation. Based on this, the real mechanism is built, but unfortunately it is found unstable in some positions. Grassmann line geometry method is applied to analyze its unstable problem caused by singular posture, and then an improving method is put forward to solve it. With the improved mechanism, closed loop vector method is employed to establish the inverse position equation of the parallel mechanism, and kinematics analysis is carried out to get the mapping relationships between position, speed, and acceleration of moving and fixed platform. Monte Carlo method is used to analyze the workspace of the mechanism, to explore the influencing factors of workspace, and then to get the better workspace. Finally, an experiment is designed to verify the mechanism working performance.
Highlights
Wang [22] used a 4 × 4 Jacobian matrix to analyze the singularity of a spatial 4-DOF parallel mechanism; J
6-DOF Stewart platform [31] is used as the prototype for 5-DOF parallel mechanism
It can be seen from this that the improved parallel mechanism has no singularity in the workspace, and each position can be uniquely determined by the mechanism
Summary
Parallel mechanism (PM) can be defined as a closed-loop mechanism in which the moving platform and the fixed platform are connected by at least two independent kinematic chains. Xiaoqiang Du [16] proposed a new U-PRU-PUS parallel mechanism solar tracking device with two degrees of freedom, analyzed its singular position, and optimized its motion range. O. Piccin et al [21] put forward a new type of five DOF parallel robot structure, deduced the inverse kinematics model and forward kinematics model of the mechanism, and applied it to medical equipment. J. Wang [22] used a 4 × 4 Jacobian matrix to analyze the singularity of a spatial 4-DOF parallel mechanism;. The fixed-link length driving mode can greatly reduce the structural size of the link, which does not make it easy to produce interference in the process of movement [30] This driving mode is used to build parallel mechanism in this paper. We study the 5PUS-UPU five-degree-of-freedom parallel mechanism from aspects of scheme design, freedom degree verification, test equipment construction, singularity analysis, scheme improvement, mechanism motion analysis, workspace analysis, and experimental verification
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