Online Learning and Suppression of Vibration in Collaborative Robots with Power Tools

Vibration suppression is an important skill for future robots that will collaborate with humans in industrial settings. The vibration through physical interaction is a com- mon problem in such settings, especially in operations involving hand-held vibrating tools. The existing human-robot collabora- tion (HRC) works addressing this problem mostly focus on the oscillations caused by the human operator, and suppress them by adapting the admittance parameters. This, however, usually results in stiffer robot behavior and contributes to reducing the overall performance of the task, in particular when impedance planning is a requirement. In this work, we focus on the vibration coming from external sources such as power tools and suppress it actively. We learn the vibration using the bandlimited multiple Fourier linear combiner (BMFLC) algorithm and apply it as a feedforward Cartesian force to cancel the vibration. We combine the feedforward force control with variable impedance learning and show that it improves the vibration suppression performance in simulation and real- world experiments. The feedforward approach can suppress the vibration better while keeping a more compliant set of impedance parameters, which is crucial in HRC.