Abstract
This paper proposes a finite-time output feedback methodology for the path-following task of marine surface vessels. First, a horizontal path-following model is established with unknown sideslip angle, unmeasured system state and system uncertainties. A hierarchical control structure is adopted to deal with the cascade property. For kinematics system design, a finite-time sideslip angle observer is first proposed, and thus the sideslip angle estimation is compensated in a nonlinear line-of-sight (LOS) guidance strategy to acquire finite-time convergence. For the heading control design, an extended state observer is introduced for the unmeasured state and equivalent disturbance estimation, based on which an output feedback backstepping approach is proposed for the desired tracking of command course angle. The global stability of the cascade system is analyzed. Simulation results validate the effectiveness of the proposed methodology.
Highlights
With the rapid growth of marine sciences and the improvement of advanced motion control technique in recent years, investigations of unmanned marine surface vessels have received increasing interest in both military and civil applications
An extended state observer (ESO) is adopted for both unknown system state and total disturbance estimation, based on which an output feedback backstepping controller is proposed without angular velocity measurement
Considering the system model of the marine surface vessel described in Equations (8) and (13), with the proposed finite-time generalized observer (FGO) and nonlinear guidance law in Equations (15) and (16), and the ESO-based output feedback backstepping controller in Equations (50) and (54), the system states of the close-loop system are semi-globally uniformly ultimately bounded (UUB)
Summary
With the rapid growth of marine sciences and the improvement of advanced motion control technique in recent years, investigations of unmanned marine surface vessels have received increasing interest in both military and civil applications. According to the descriptions above, robust output feedback path-following methodology is proposed in this paper for the vessels based on a finite-time LOS guidance algorithm. By considering the unknown time-varying sideslip angle, unmeasured system state and uncertainties, system model of path-following problem is presented, based on which hierarchical technique is adopted for control system implementation. A finite-time generalized observer (FGO) is proposed to estimate and compensate the sideslip angle together with a nonlinear LOS guidance law to acquire finite-time convergence. The path-following problem is formulated with unknown time-varying sideslip angle, unmeasured system state and system uncertainties, the observation technique is adopted to estimate all these unknown terms. 3. An ESO is adopted for both unknown system state and total disturbance estimation, based on which an output feedback backstepping controller is proposed without angular velocity measurement.
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