Simultaneous Minimum-time Transition and Oscillation Supression of Robot Contact Force Control: a Trajectory Planning Approach

Robot contact force control plays a crucial role in achieving precise and stable interactions between robots and environments. Existing contact force control methods, such as impedance and admittance control, often face challenges in balancing motion efficiency and stability during the transition from the free motion phase to the contact phase. Generally, existing variable admittance controllers with small admittance parameters suffer from significant oscillations of the contact force and motion, while the motion efficiency decreases dramatically with large admittance parameters of an admittance controller. To address this issue, we propose a time-optimal trajectory planning-based contact force control algorithm, which integrates an online trajectory planning module within the framework of variable admittance control. Finally, we conducted constant force tracking experiments on a 7-DoF collaborative robotic manipulator to validate the effectiveness of the proposed approach. Experimental results demonstrate that our approach ensures time-optimal performance in the free motion phase, while significantly suppressing oscillations of the contact force and motion trajectory during the contact phase.