Optimization-Based Variable Impedance Control of Robotic Manipulator for Medical Contact Tasks

This work presents an optimization-based variable impedance control strategy for controlling a robotic manipulator in medical contact tasks. Specifically, the optimal robot stiffness for performing the medical contact task is obtained using online Quadratic programming (QP). In the meantime, an energy tank approach is incorporated into the control loop to regulate the system’s passivity. To verify the performance of the proposed strategy, experiments are conducted on both “static” and “scanning” medical contact tasks, utilizing materials with different properties, different magnitudes of contact forces, as well as uneven conditions with a human torso phantom model and slope surface. The maximum Root Mean Square Error (RMSE) of force tracking with the proposed method in the “static” and “scanning” tasks, across all setups, is 0.88 and 0.5 N, respectively. The experiment results demonstrate the superiority of the proposed control strategy compared with traditional manual contact and constant stiffness (CS) impedance control-based ones. The proposed control framework is promising to be integrated into robot-assisted medical contact tasks, for example, the palpation and Ultrasound (US) imaging scenarios.