Simultaneous planning and executing trajectory tracking control for underactuated unmanned surface vehicles from theory to practice

In this work, a trajectory tracking method for underactuated unmanned surface vehicles (USVs) is proposed to address control challenges related to state constraints and system uncertainties. The method involves the development of a model transformation that allows for the derivation of radius-track, yaw-track, and sway-track control models in a newly defined path-moving polar coordinate system (PMPCS). In the PMPCS, the sway-track motion is controlled through an incremental angle that adjusts the orientation of the PMPCS in real-time. Additionally, a simultaneous planning and executing (SPAE) controller is proposed to accurately achieve three state-constrained control objectives within the PMPCS. The proposed controller combines a state-constrained planning polynomial that generates a planned acceleration, an estimation of unknown uncertainties, and a discrete algebraic control law that implements this planned acceleration. When the feedback acceleration is executed as the planned acceleration, the states of the tracking motion will accurately reach the desired states from the trajectory after a specified time period due to the integration of the planned acceleration. A control gain is introduced to estimate the nonlinear uncertainty term, and no fine-tuning of this control gain is necessary. To demonstrate its effectiveness and superiority compared to other methods, simulations and experiments have been conducted.