Variable Stiffness Control with Strict Frequency Domain Constraints for Physical Human-Robot Interaction
This work addresses safety and adaptability in human-robot interaction, but it is incremental as it builds on existing variable impedance control methods with specific frequency constraints.
The paper tackled the problem of variable stiffness control for physical human-robot interaction by proposing a gain-scheduled approach with strict frequency-domain constraints, resulting in improved performance validated through simulations and experiments compared to a baseline method.
Variable impedance control is advantageous for physical human-robot interaction to improve safety, adaptability and many other aspects. This paper presents a gain-scheduled variable stiffness control approach under strict frequency-domain constraints. Firstly, to reduce conservativeness, we characterize and constrain the impedance rendering, actuator saturation, disturbance/noise rejection and passivity requirements into their specific frequency bands. This relaxation makes sense because of the restricted frequency properties of the interactive robots. Secondly, a gain-scheduled method is taken to regulate the controller gains with respect to the desired stiffness. Thirdly, the scheduling function is parameterized via a nonsmooth optimization method. Finally, the proposed approach is validated by simulations, experiments and comparisons with a gain-fixed passivity-based PID method.