Command filtered path tracking control of saturated ASVs based on time‐varying disturbance observer

Abstract

This paper investigates the path-tracking control problem for an autonomous surface vessel (ASV) with unknown time-varying disturbances and input saturation. A robust nonlinear control law is proposed based on a disturbance observer and an auxiliary system in the context of command filtered control.The disturbance observer is constructed to estimate the unknown time-varying disturbances, the auxiliary dynamic system is employed to handle input saturation, and the compensator based command filtered control technique makes the designed path-tracking control law simple and easy to implement in practice. It is proved that the nonlinear control law can track the desired vessel's position and heading, while guaranteeing the uniform ultimate boundedness of all signals in the path-tracking control system. Simulation results further demonstrate the effectiveness of the method.

Fixed-time Leader-Following Formation Control of AUVs Without Velocity Measurements

“…Theorem 1 For a group of autonomous underwater vehicles with kinematics and dynamics in (8) under dynamic control law (25) with update law (26), and kinematic control law (17) with command filter (5) and error compensator (18), the following results hold: 1). The formation tracking control can be achieved in a fixed time, denoted as T s .…”

“…From the above analysis, it can be concluded that the formation tracking system with velocity observerbased control law (46) does not escape in any finite time interval. Following the analysis at the beginning of the proof, one has that the closed-loop system under (17), (18), (42) and (46) is practically fixed-time stable. This completes the proof.…”

“…For practical AUVs subject to actuator saturations, the method is still useful but some amendments are needed and the settling time might be larger. Specifically, one can modify the system model using the auxiliary system technique in [18] or the adaptive approximation method in [22] to address the saturation issue.…”

Finite-Time Trajectory Tracking for Marine Vessel by Nonsingular Backstepping Controller With Unknown External Disturbance

“…In recent years, the nonlinear backstepping control technique is proved with its effectiveness and designing simplicity to use for controlling the marine vessels. In [14] and [15], a disturbance observer is used to estimate unknown external disturbance, then combining backstepping method to accomplish trajectory tracking. Reference [16] combines adaptive feedback approximation technique and backstepping to design an adaptive neutral network control.…”

“…(2) The traditional backstepping approaches [14], [15] can only achieve the uniformly ultimately bounded convergence, i.e., the tracking error only converges to a region. However, the proposed finite-time backstepping controller can accomplish zero error tracking in finite time, which adopts a finite-time command filter based on the first-order Levant differentiator to obtain virtual control's derivative.…”