Apparent inertia reduction via force sensorless impedance control

In interactive robot tasks, virtual compliance at the interaction port is often achieved using impedance control. The impedance controller can be extended with force feedback to adjust the inertia at the interaction port, classically done using a force sensor. In cases where forces cannot be measured accurately, a disturbance observer (DOB) can be employed. In this work, we propose to extend the classical inertia shaping controller with a DOB and investigate the limits of mass rendering. We analyse passivity using mechanical equivalents and stability using Hurwitz analysis. We also compare the DOB-based impedance controller with optimal results from H2 and μ[jls-end-space/]-synthesis on a dedicated 2-Degrees-of-Freedom (DoF) experimental setup with an internal parasitic mode. The results highlight a clear trade-off between inertia reduction, robust stability and performance. Although the DOB-based controller provides an intuitive design, H2 allows to increase the bandwidth, while μ[jls-end-space/]-synthesis improves robustness.