A Model Reference Friction Observer for Friction Compensation and Shaping in Interaction Control

Friction phenomena may significantly deteriorate the performance and reliability of force-controlled systems. Despite existing solutions, achieving accurate and robust friction compensation is challenging due to model inaccuracies and parameter identification issues. This letter proposes a force control architecture with accurate friction compensation and friction shaping capabilities, based on a novel model reference approach. Since passivity is a fundamental requirement for interaction control, this work investigates under which conditions the proposed approach preserves passivity at the environment, control, and friction ports. This implies that the proposed architecture can passively compensate for any type of friction and can be combined with any passive force controller while guaranteeing a stable interaction with any passive environment. The approach is validated using simulation and experimental trials.