The technology of hydrodynamic modeling and marine craft motion control systems has progressed greatly in recent years. This timely survey includes the latest tools for analysis and design of advanced guidance, navigation and control systems and presents new material on underwater vehicles and surface vessels. Each section presents numerous case studies and applications, providing a practical understanding of how model-based motion control systems are designed.

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Handbook of Marine Craft Hydrodynamics and Motion Control: Fossen/Handbook of Marine Craft Hydrodynamics and Motion Control

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Control allocation—A survey

Survey Constructive nonlinear control: a historical perspective

The performanceand computational requirements ofoptimization methodsfor control allocation areevaluated Two control allocation problems are formulated: a direct allocation method that preserves the directionality of the moment and a mixed optimization method that minimizes the error between the desired and the achieved momentsaswellasthecontroleffortTheconstrainedoptimizationproblemsaretransformedinto linearprograms so that they can be solved using well-tried linear programming techniques such as the simplex algorithm A variety of techniques that can be applied for the solution of the control allocation problem in order to accelerate computations are discussed Performance and computational requirements are evaluated using aircraft models with different numbers of actuators and with different properties In addition to the two optimization methods, three algorithms with low computational requirements are also implemented for comparison: a redistributed pseudoinverse technique, a quadratic programming algorithm, and a e xed-point method The major conclusion is that constrained optimization can be performed with computational requirements that fall within an order of magnitude of those of simpler methods The performance gains of optimization methods, measured in terms of the error between the desired and achieved moments, are found to be small on the average but sometimes signie cantAvariety ofissuesthataffecttheimplementation ofthevariousalgorithmsin ae ight-controlsystem are discussed

Evaluation of optimization methods for control allocation

Brief Global tracking control of underactuated ships by Lyapunov's direct method

Control allocation problems can be formulated as optimization problems, where the objective is typically to minimize the use of control effort (or power) subject to actuator rate and position constraints, and other operational constraints. Here we consider the additional objective of singularity avoidance, which is essential to avoid loss of controllability in some applications, leading to a nonconvex nonlinear program. We suggest a sequential quadratic programming approach, solving at each sample a convex quadratic program approximating the nonlinear program. The method is illustrated by simulated maneuvers for a marine vessel equipped with azimuth thrusters. The example indicates reduced power consumption and increased maneuverability as a consequence of the singularity-avoidance.

Constrained nonlinear control allocation with singularity avoidance using sequential quadratic programming

In this paper two non-linear control laws for ships are derived by using a non-linear ship model which includes the hydrodynamic effects due to time-varying speed and wave frequency. The non-linear ship model does not have the structural properties of symmetric inertia and positive damping at high speed, which are common assumptions, when designing non-linear ship tracking control systems. Backstepping control designs are used to circumvent the problem of a non-symmetrical inertia matrix. The first case is ship tracking with full actuation in surge, sway and yaw while the second case discusses an emergency situation where a ship is supposed to track a time-varying trajectory by using the bow thruster and one of the main propellers as actuation devices only. The application of speed- and wave-dependent models for ship control is a first step towards the design of a new generation of non-linear ship control systems that can operate under time-varying speed and wave frequency conditions. Previous work has often relied on the assumption of constant speed, and practical solutions have been based on switching between different control schemes at different speeds. Slowly varying environmental disturbances, such as ocean current, second-order wave-induced disturbances and wind forces, are compensated for by using adaptive backstepping. Global uniform asymptotic stability (GUAS) is proven for the fully actuated case by using a recent theorem for GUAS when backstepping with integral action, whereas asymptotic tracking of position and velocity are shown for the degraded control case. Computer simulations illustrate the performance and the robustness of the control laws for an offshore supply vessel. © 1998 John Wiley & Sons, Ltd.

Non-linear and adaptive backstepping designs for tracking control of ships

A nonlinear vectorial backstepping control law for commercial ships is derived by using the concept of vectorial backstepping. Vectorial backstepping is done in 3 steps corresponding to the state vectors of the ship dynamics, kinematics and actuator dynamics. Emphasis is placed on compensation of the actuator dynamics since the bandwidth of the propellers, thrusters and rudders often is close to the bandwidth of the ship dynamics. Global exponential tracking is proven by applying Lyapunov stability analysis. The case study is simultaneously global exponential tracking of the surge and sway positions (x,y) and the yaw angle /spl psi/ of a surface ship. This can only be done by applying nonlinear control theory due to the nonlinear structure of the kinematic equations, Coriolis and centripetal forces, and hydrodynamic damping forces.

S. P. Berge

Papers

Constrained nonlinear control allocation with singularity avoidance using sequential quadratic programming

Non-linear and adaptive backstepping designs for tracking control of ships

Nonlinear vectorial backstepping design for global exponential tracking of marine vessels in the presence of actuator dynamics

Robust Control Allocation of Overactuated Ships; Experiments with a Model Ship

Nonlinear Control of Underactuated Ships with Forward Speed Compensation