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 H 2 and μ -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, H 2 allows to increase the bandwidth, while μ -synthesis improves robustness. • Apparent inertia reduction by extending impedance control with a disturbance observer. • Apparent inertia reduction limits governed by bandwidth and internal mode. • Improved stability robustness for apparent inertia reduction by H2 and μ -synthesis • Experimental validation and comparison on custom single-axis setup with internal mode.
Gerlagh et al. (Mon,) studied this question.