Abstract
Considering the sailing characteristics and difficult maneuverability of hovercraft, the three degree-of-freedom (DOF) mathematical model cannot describe effectively the motion of hovercraft. Therefore, a mathematical model of four-DOF motion of hovercraft is established. This paper addresses the trajectory tracking problem of the hovercraft with finite-time convergence to equilibrium point, model uncertainty, external disturbance and drift angle constraint based on the four-DOF model. A novel robust tracking controller is proposed by combining finite-time observer with adaptive sliding mode control to solve the problem of the finite-time convergence and handle approximation error. In order to ensure the safe navigation of the hovercraft, a safety constraint auxiliary system is designed to restrain the drift angle in real time. Furthermore, a finite-time observer is designed to estimate and compensate model uncertainties and external disturbances. We show that under the proposed control scheme, all tracking errors can converge to zero in finite time, the drift angle can be constrained in real time and all closed-loop signals are guaranteed to be bounded. Finally, the numerical simulation results show the effectiveness of the proposed method.
Highlights
There is flexible skirt around the bottom of underactuated hovercraft for sealing the cushion air
The problems solved in this paper can be formulated as follows: Considering the hovercraft models (7) and (8) in existence of the model uncertainties and external disturbances, a finitetime adaptive PI sliding mode trajectory tracking controller is designed to generated surge force τu, desired yaw angular velocity αr and yaw moment τr in order to guarantee velocity tracking errors ue, ve and yaw angular velocity tracking error re converge to zero in finite time
The reasonable design of the desired surge and sway velocities and yaw angular velocity are calculated by (17) and (37), the finite-time PI sliding mode controllers are obtained by (31) and (46), the model uncertainties and external disturbances are estimated by the finite-time observer (25), and the safety constraint auxiliary system of hovercraft drift angle β is designed as (41), all tracking errors can be ensured to converge to zero in finite time, the drift angle β can be restrained in real time and all closed-loop signals in the system are bounded
Summary
There is flexible skirt around the bottom of underactuated hovercraft for sealing the cushion air. Motivated by the above-mentioned observations, a novel finite-time adaptive PI sliding mode trajectory tracking control strategy for underactuated hovercraft with drift Angle constraint is proposed. The problems solved in this paper can be formulated as follows: Considering the hovercraft models (7) and (8) in existence of the model uncertainties and external disturbances, a finitetime adaptive PI sliding mode trajectory tracking controller is designed to generated surge force τu, desired yaw angular velocity αr and yaw moment τr in order to guarantee velocity tracking errors ue, ve and yaw angular velocity tracking error re converge to zero in finite time. Where η1 ≥ εu max is a very small design constant which can offset the estimation error of the finite-time observer. εu max > |eu2|, η2 > 0 and ks1 > 0 are constants
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