Optimal design of dynamic and control performance for planar manipulator

Abstract

k]A design and optimization approach of dynamic and control performance for a two-DOF planar manipulator was proposed. After the kinematic and dynamic analysis, several advantages of the mechanism were illustrated, which made it possible to obtain good dynamic and control performances just through mechanism optimization. Based on the idea of design for control (DFC), a novel kind of multi-objective optimization model was proposed. There were three optimization objectives: the index of inertia, the index describing the dynamic coupling effects and the global condition number. Other indexes to characterize the designing requirements such as the velocity of end-effector, the workspace size, and the first mode natural frequency were regarded as the constraints. The cross-section area and length of the linkages were chosen as the design variables. NSGA-II algorithm was introduced to solve this complex multi-objective optimization problem. Additional criteria from engineering experience were incorporated into the selecting of final parameters among the obtained Pareto solution sets. Finally, experiments were performed to validate the linear dynamic structure and control performances of the optimized mechanisms. A new expression for measuring the dynamic coupling degree with clear physical meaning was proposed. The results show that the optimized mechanism has an approximate decoupled dynamics structure, and each active joint can be regarded as a linear SISO system. The control performances of the linear and nonlinear controllers were also compared. It can be concluded that the optimized mechanism can achieve good control performance only using a linear controller.