Nonlinear Formation Control of Virtually Coupled Train Set With Uncertainties: A Distributed Robust MPC Approach Using Tube Techniques

The emerging virtual coupling technology aims to connect multiple train units as a virtually coupled train set (VCTS) with outstanding operation efficiency and flexibility. This paper studies the nonlinear formation control of VCTS, particularly considering the uncertainties from external disturbances and the practical modeling of formations. To solve this problem, we propose a distributed robust nonlinear model predictive control approach using tube techniques. Based on the analysis of contractiveness, nonlinear tubes are constructed to confine the uncertain trajectory influenced by uncertainties from the formation model, disturbances and distributed prediction. Specifically, to facilitate tube construction, compatibility constraints are deployed to restrict uncertainties from distributed prediction. Furthermore, the robust constraint satisfaction, recursive feasibility and stability of VCTS operations are established. Finally, based on the practical data in field tests, comparative experiments are conducted to demonstrate the advantages of our approach in control performance and computational efficiency.