Robust Augmented Computed Torque Control for Enhanced Tracking of 6-DoF Manipulators Under External Disturbances

This paper presents an augmented computed—torque control (A-CTC) scheme for 6-DoF industrial manipulators operating under model uncertainty and external disturbances. The proposed controller combines a nominal computed torque law with an additional torque-domain residual damping term to compensate for modeling errors and unmodeled friction while preserving the baseline tracking structure. A Lyapunov-based analysis is developed for the resulting closed-loop system, and bounded output constraints are imposed on the residual term to support input-to-state stability and bounded tracking errors. The method is evaluated in simulation against PD feedforward (PD-ff) and sliding mode control (SMC) over multiple trajectories and disturbance scenarios. Across 30 randomized trials, A-CTC reduces joint-space RMSE by approximately 12.8%, end-effector RMSE by 13.0%, and disturbance-settling time by 32.4% compared with PD-ff, while increasing RMS torque by only 4.5%. Compared with SMC, A-CTC achieves lower joint-space and end-effector RMSE by 7.4% and 4.1%, respectively, while reducing RMS torque by 40.0% and saturation time by 54.5%. Additional simulation studies, including gain-sensitivity analysis, Jacobian conditioning assessment, and impulse response tests, further support a favorable accuracy–effort trade-off and improved disturbance rejection. The present results are based on simulation and will be validated experimentally in future work.