Pade-augmented artificial potential field-based cooperative control for multi-Mobile robot transportation systems...

This paper addresses cooperative transportation of multi-mobile robots (MMRs) under input delays, frictional forces, external disturbances and parameter perturbations by proposing a distributed leader-follower cooperative control strategy based on a Pade-augmented artificial potential field (P-APF) to enhance stability and robustness. Firstly, a dynamic model of the MMRs system (consisting of the MMRs formations and the workpieces) is established, which is further transformed into an approximate delay-free form via the first-order Pade approximation to handle input delays. Subsequently, a fixed-time nonlinear disturbance observer (NDO) is designed to accurately estimate and compensate for the lumped disturbances composed of frictional forces, external disturbances and parameter perturbations, thereby significantly improving the system's resistance to uncertainties. Then, the equivalent delay state variables are established and incorporated into the artificial potential field (APF) function to develop a cooperative controller based on the P-APF method, which ensures accurate formation convergence and maintains inter-robot connectivity. The asymptotic convergence of the nominal error system (residual-free) is proved by LaSalle's invariance theorem and Barbalat's lemma. For the actual closed-loop system, the formation and velocity errors are uniformly ultimately bounded under the bounded residual term. Finally, simulation results demonstrate the effectiveness of the proposed approach in achieving stable cooperative transportation of the MMRs system.