Predefined-time Disturbance Observer-based Nonlinear Model Predictive Control for Free-flying Space Robots Under External Disturbances

With advancing space exploration missions, space robots have emerged as critical unmanned platforms for on-orbit operations and servicing. However, external disturbances caused by variable space environments and model parameter inaccuracies pose significant challenges to achieving high-precision control. This paper develops a model predictive control framework incorporating a predefined-time disturbance observer, specifically designed for free-floating space robots operating under such perturbations. The observer enables disturbance estimation errors to converge within predefined constant bounds. By compensating the model predictive controller with estimated disturbance values, this approach substantially enhances trajectory tracking accuracy under perturbed conditions. Numerical simulations validate the effectiveness of the proposed methodology.