Dynamic Modeling and Model-Based Force Control of a 3-DOF Translational Parallel Robot

Abstract

A 3-axis parallel loading mechanism, which works as a multi-axis load simulator, is proposed for reliability test of multi-axis CNC machine tools by exerting specific load spectrums on the spindle. To achieve efficient loading force control, dynamic model of the 3-DOF translational parallel robot is derived via the virtual work principle and is embedded into the control strategy to build a model-based control scheme. A mass distribution factor is introduced and the rotating inertia of the limbs is neglected to simplify the dynamics equations for better real-time control performance. This simplification method is verified by comparison with the complete dynamics model. Then the simplified dynamic model is integrated with a PI (proportional–integral) controller with feedforward to control the moving platform’s output force in the task space and this control strategy is verified through co-simulations with MATLAB/Simulink and ADAMS. Simulation results show that the proposed model-based PI controller is effective to control the three-dimensional output force of the 3-DOF translational parallel robot.