A novel 3-DOF parallel mechanism for efficient wool harvesting: design, modeling analysis and experimental implementation

In this paper, a wool harvesting machine platform is designed, among which the core part is a novel spatial parallel mechanism (PM), and the topology, kinematics and prototype development of the novel PM are investigated systematically. Firstly, the screw theory is employed to analyze the topology of the novel PM in detail, and reveals that the PM has three translational degrees of freedom (DOFs). Secondly, closed-loop vector method is utilized to analyze the inverse solution of position, elimination method is adopted to solve the nonlinear equations to get analytical forward position solution, and the velocity and acceleration mapping models are uniformly obtained by derivation method. The reachable workspace is further analyzed by limited boundary approach and various singular configurations within workspace are anatomized correspondingly. Subsequently, the performance of the PM is evaluated comprehensively in terms of motion/force transmissibility, pressure angle and stiffness indices. Furthermore, the inverse kinematics and the analytical forward position solution are verified exactly by Adams and Matlab, and the Simulink&Adams co-simulation test using task-space proportional-derivative feedback control is further carried out. Based on theoretical analysis, the prototype model and control system are established, and the correctness of theoretical analysis is experimentally verified, and the existing issues are also analyzed, which lays sound foundation for the development of the second-generation prototype and practical application in future.