Abstract:

Focused on a 4-DOF parallel mechanism with the spatial motion called SCARA (three dimensional translation and one-dimensional rotation), the establishment of its simplified dynamic model of rigid body is systematically researched to improve the accuracy to solve torque. Based on the kinematics analysis, the complete dynamic model of rigid body is established with the virtual work principle, and its accuracy is examined by ADAMS. To reduce the computational complexity, taking the structure and state of motion in every moving part of the mechanism into consideration, the simplified dynamic model of rigid body with single parameter is established. For the expected simplification, when the mechanism is moving along the standard trajectory, the average of maximum absolute torque difference between values solved from the complete dynamic model and the simplified dynamic model as optimization function are taken and the relation between the function and scale parameters is analyzed. Under the authentication of the analysis results, based on a set of given parameters, the optimal value is obtained by using the single objective optimization method. The validity of the method is verified through a set of image contrast compared with existed theories.

Key words: complete dynamic model, simplified dynamic model, single objective optimization, SCARA motion