An improved constraint control framework for unmanned surface vehicles using command-filtered backstepping technique

This work proposes an adaptive tracking controller for unmanned surface vessels (USVs) with full-state time-varying constraints using the command-filtered backstepping technique. Different from previous constraint control schemes, the constraints of this nature in the work, which arise sometime after the initiation of USVs operations rather than from the outset, are commonly encountered in practice, yet they have not received sufficient attention in existing schemes. By introducing the shifting function, the initial value setting range of USVs can be greatly expanded, even if these initial values are unknown. The core idea of the work is to reduce the conservatism of the USVs constraint control scheme, whose initial value needs to be set in the constraint domain, while realizing the state constraints after a preset time. To avoid the complex differentiation process of the virtual controller, the command-filtered is introduced in the backstepping framework. Ultimately, the feasibility of the scheme was confirmed by setting two different trajectory signals.