Hierarchical constraint-based formation control strategy for multi-robot cooperative transportation system in warehousing scenarios

Abstract

This study proposes a hierarchical constraint-based formation control strategy for the multi-robot cooperative transportation system (MRCTS) in warehousing scenarios, simultaneously achieving trajectory tracking and formation maintenance, and ensuring the safety and stability of the transported cargo. The strategy decomposes the cooperative transportation into two hierarchical sub-problems: an upper-layer cargo trajectory tracking problem and a lower-layer formation control problem. In the upper layer, while establishing cargo trajectory tracking constraints, a cargo safety mechanism is developed via cargo dynamics analysis to avoid sliding and tipping risks by constraining motion characteristics like acceleration; in the lower layer, a MRCTS model is built based on the leader-follower strategy, and motion constraints are established for each follower robot to guarantee the scheme’s engineering feasibility. Subsequently, a cargo trajectory tracking controller and a distributed formation controller are, respectively, designed based on model predictive control (MPC), with the cost function improved to ensure the cargo is transported safely and smoothly along the predetermined route. Simulations demonstrate that the proposed method can effectively control the MRCTS to complete cooperative transportation of oversized cargo, and compared with typical control algorithms, it exhibits better control accuracy and robustness.