Finite-Time Torque Control for Bolt-Tightening Robot via a Disturbance Observer

Transmission towers serve as critical infrastructures in high-voltage power systems, where the reliability of bolt connections directly affects structural integrity and operational safety. To address the challenges posed by the large number of bolts, stringent torque accuracy requirements, and inconsistency in traditional manual operations, a time-varying bolt-tightening system model is established by considering parameter uncertainties and external disturbances. Furthermore, a finite-time disturbance observer (FDO) is designed to handle unknown disturbances in the system. By introducing adding a power integrator technique with state-dependent gain, a finite-time control algorithm (FTC) based on the disturbance observer is devised to enhance torque control accuracy and disturbance rejection performance. A rigorous theoretical analysis is provided to ensure the finite-time stability of the closed-loop system. Simulation and experimental results validate the effectiveness of the proposed approach, which demonstrates improvements in control accuracy and disturbance rejection compared to conventional methods.