Disturbance Observer-Based Robust Force Control for Tendon-Sheath Mechanisms

摘要

This paper proposes a disturbance observer (DOB)-based robust force control framework for tendon-sheath mechanisms (TSMs) that transmit tension forces from the proximal to the distal end. A detailed physical model of the TSM system, where a motor actuates the tendon and the output corresponds to the contact force at the robot end-effector, is developed. However, the resulting nominal model adopts a simplified representation of friction and involves significant parametric uncertainties due to the inherently complex dynamics of the tendon-sheath structure. By rigorously verifying the well-established robust stability conditions associated with DOB-based control frameworks, it is confirmed that the tendon-sheath transmission system satisfies all required assumptions and stability criteria. Furthermore, the necessary additional conditions can be readily met by appropriately designing the Q-filter, which is comparatively straightforward in practice. This validation supports the theoretical soundness and practical suitability of employing a DOB to effectively estimate and compensate for the system’s inherent parametric uncertainties and external disturbances. Numerical simulations incorporating a discrete-segment tendon model with an advanced friction dynamics formulation demonstrate significant improvements in force tracking accuracy at the tendon’s distal end compared to conventional control schemes without DOB compensation. The results highlight the robustness and effectiveness of the proposed control scheme for tendon-driven robotic systems.