Renxiang Bu

Robust adaptive backstepping design for course-keeping control of ship with parameter uncertainty and input saturation

In this paper, a novel robust adaptive control algorithm is proposed for a class of ship course autopilot with parameter uncertainty and input saturation. With the help of Lyapunov stability theory and adaptive backstepping technique, one controller is constructed by considering parameter uncertainty and actuator saturation constraints, and the stability analysis subject to the effect of input saturation constrains is conducted by employing an auxiliary design system. It is also proved that the proposed algorithm could guarantee the closed-loop system to be uniformly ultimately bounded and the output converges to a small neighborhood of zero. Simulation results are given to illustrate the effectiveness and the performance of the proposed scheme.

Active Disturbance Rejection with Sliding Mode Control Based Course and Path Following for Underactuated Ships

The compound control of active-disturbance-rejection control (ADRC) with sliding mode is proposed to improve the performance of the closed-loop system and deal with the constraint condition problem of a surface ship. The advantages of ADRC with sliding mode were verified by ship course control simulations. Meanwhile, to solve the path-following problem of underactuated surface ships with uncertainties of internal dynamic and external disturbances, the ADRC controller with sliding mode is introduced to steer the ship to follow the desired path. In order to overcome the cross-track error caused by wind and current, drift angle is compensated in the controller by designing a coordinate transformation equation. Simulations were performed on a nonlinear kinematics model of a training ship to validate the stability and excellent robustness of the proposed path-following controller.

Direct adaptive NN control of ship course autopilot with input saturation

In this paper, a novel direct adaptive NN control algorithm is proposed for a class of ship course autopilot with input saturation. Neural networks (NNs) are used to tackle unknown nonlinear function, and then an adaptive NN controller is constructed by combining Lyapunov function and the backstepping technique. By utilizing a special property of the affine term, the developed scheme avoids the controller singularity problem completely, and the stability analysis subject to the effect of input saturation constrains is conducted by employing an auxiliary design system. It is also proved that the proposed algorithm could guarantee the closed-loop system to be uniformly ultimately bounded and the output of the system is proven to converge to a small neighborhood of the desired trajectory. Finally, simulation studies are given to illustrate the effectiveness and the performance of the proposed scheme.

A Mutation-Classified, Parameter-Dynamic Immunological Algorithm for Global Optimization

Based on the artificial immune system, a new clonal selection algorithm is proposed to perform global optimization. The concept of classified mutation is defined and the dynamic adjustment methods of some evolution parameters are introduced. The proposed algorithm is applied to several benchmark problems, and its performance is compared with other approaches in the literature. The results indicate that the new algorithm is a significant advance in clonal selection and a viable alternative.

Nonlinear Sliding Mode Berthing Control of Underactuated Surface Ships

A novel output feedback strategy is presented for the berthing control of underactuated surface ships with nonintegrable acceleration constraint. Saturations on actuators, systemic uncertainties and drift caused by current or wind are considered. The problems of trajectory planning and tracking are circumvented by means of iterative nonlinear sliding mode control (INSMC) method. The sliding modes are decentralized and recursively designed on phase planes in the augmented states space. Increment feedback control law is developed based on the INSMC to (locally) stabilize the ships motion without estimation of uncertainties and disturbances. Numerical simulation results on a full nonlinear hydrodynamic model of a training ship are presented to validate the invariability and excellent performance of the proposed algorithm.

Adaptive control for ship steering based on clonal selection model identification

Using clonal selection model identification, an adaptive PD control algorithm with disturbance compensation is proposed for uncertain and nonlinear system in ship steering. Actual ship with disturbance and model uncertainty, regarded as a black box, is dynamically identified as second-order linear model with disturbance terms; then, certainty equivalence principle is applied to tune the PD control parameters while the disturbance is compensated. The combination of previous elitist reservation and stochastic initialization for the initial population in clonal selection algorithm improves the optimization efficiency for dynamic problem. Simulations on the third-order nonlinear cargo vessel verify that the proposed adaptive control algorithm possesses strong robustness and improves the capability of PD controller in inhibiting stable error.

Path following and stabilization of underactuated surface ships

To solve the path following and stabilization problems for underactuated surface ships with nonintegrable acceleration constraint, a nonlinear feedback algorithm is presented using decoupling control method and iterative nonlinear sliding mode designing approach. The saturations on actuators and unknown environmental disturbances are also explicitly considered. Integrating with simple increment feedback control laws, a dynamic control strategy is developed to fulfill the underactuated following and stabilization objectives with only surge force and yaw movement available. Numerical simulation results on a full nonlinear hydrodynamic model of a training ship are presented to validate the effectiveness and robustness of the proposed controller.

Path following of underactuated surface ships

The path following problem is concerned for conventional surface ships with second order nonholonomic constraints. A nonlinear feedback algorithm is presented using decoupling control method. The cross track error and heading error are stabilized by means of the rudder alone and the thruster is left to adjust the forward speed. The underactuated following control objective is achieved without a reference orientation generated by a ship model. The estimation of systemic uncertainties and disturbances and the yaw velocity PE (persistent excitation) conditions are not required. Computer simulation results on a full nonlinear hydrodynamic ship model of M.V. YULONG are provided to validate the effectiveness and robustness of the proposed controller.

FNN-based Robust Adaptive Tracking Control for a Class of Uncertain Nonlinear Systems

An FNN (fuzzy neural network)-based robust adaptive controller is presented for a class of perturbed uncertain nonlinear system with unknown virtual control gain functions (UVCGF). The FNN is used to approximate unstructured uncertain functions. The proposed algorithm, which combined Nussbaum gain with the decoupled backstepping techniques, does not require a priori knowledge of the signs of the UVCGF, and circumvents the controller-singularity problem gracefully. It proved that the tracking error can be driven to a small residual set while keeping all signals in the closed loop semi-globally uniformly ultimately bounded (SGUUB). Numerical simulation results are presented to validate the effectiveness

ADRC-Based Ship-Track Control and Its Application to Traffic Safety Evaluation in Harbor Fairway

This paper investigates the control design of a novel ship-track controller, i.e., an active-disturbance-rejection-control (ADRC)-based ship-track autopilot, and its application to the traffic safety evaluation in harbor fairway. Firstly, a robust adaptive autopilot for ship track control is developed based on ADRC, which is a model-free controller and performs with minor control energy, strong robustness and easy implementation. Then, a new ship traffic safety evaluation methodology is proposed, where an impersonal and advising strategy of ship safe maneuvering action in the investigated fairway can be further achieved. The comparing simulation results demonstrate the effectiveness of the proposed method.