A High‐Order Finite‐Time Observer for External Force Estimation of Collaborative Robots

Abstract

ABSTRACT The ability to rapidly and accurately estimate external forces applied to collaborative robots is crucial for ensuring safe physical human‐robot interaction and minimizing injury risk from potential collisions. In this research, a novel finite‐time observation method for sensorless collaborative robots to estimate time‐varying external forces is put forward. First, a generalized finite‐time observer is constructed by integrating generalized momentum dynamics and adding fractional power terms into the classical higher‐order finite‐time method to achieve the estimation of time‐varying external forces using joint control torque. A performance analysis approach is introduced to assess this higher‐order finite‐time observer with mixed fractional power terms, demonstrating optimization of dynamic response speed and steady‐state robustness. Furthermore, a Lyapunov‐based recursive verification is provided to confirm the finite‐time convergence and convergence bounds of this generalized observer. Finally, experiments are conducted on the AUBO I5 robot in two practical scenarios. The results demonstrate that the proposed observer significantly improves the detection speed of collision force by more than 5%, while simultaneously reducing the estimation error by over 4% in comparison to those of the existing finite‐time observers. Moreover, the estimation error of time‐varying interaction force is reduced by over 23% in comparison to existing ones. Furthermore, the collision detection and safe response experiments of a real collaborative robot body and end‐effector have been successfully accomplished.