IEE Proceedings - Control Theory and Applications

Prerequisites to the successful application of the H∞ control design technique to the marine dynamic positioning (DP) control problem are a realistic nominal model, relative bounds on modelling uncertainty, a set of frequency-dependent weighting functions to translate the control design specification into a control solution and a performance index to quantify the robustness. The ... View full abstract»

Design ideas and experiences gained during the development of an adaptive high precision track controller for ships are summarised. The controller is installed on a number of different ships, using a variety of position measurement systems. The design follows the spirit of the LQG paradigm combined with a model following feedforward strategy. The ship is kept to a manoeuvring trajectory through a ... View full abstract»

The two main problems with variable-structure control are control input chattering and the assumption of known parameter uncertainty bounds, the second of which is studied. The robustness of a recently proposed variable-structure control approach with estimated bounds in the paper is first examined. Analysis of the proposed variable-structure adaptive control schemes is established in the Lyapunov... View full abstract»

Concerns the finding of a collision-free path for an unmanned underwater vehicle (UUV) and manipulator, from an initial to a goal configuration, around subsea structures. The paper concentrates on efficient searching and object representation, while removing local minima. An approach to path planning using a nonlinear programming approach is presented. The free space of the workspace is represente... View full abstract»

An additional inner-feedback loop is used to reduce the channel interaction of a multivariable control system such that the design of the outer-feedback loop can be treated as a single-variable problem for ease in achieving the required main-channel performance. The relative error between the exact input-output relation tii(jω) of channel i and its approximation tˆii View full abstract»

The consequences of roll motions in ship operations can seriously degrade the performance of mechanical and personnel effectiveness. To alleviate roll motions many ships are equipped with fin stabilisers. Rudders can also generate roll motions which can be harnessed to function in congress with the fins to accrue enhanced levels of stabilisation. An integrated rudder and fin stabilisation control ... View full abstract»

A control system is proposed that improves the performance of a CO ₂ laser. It allows control of the output power of the laser within 0.1% of the desired value. Various experiments are achieved to show the efficiency of the proposed approach View full abstract»

The paper presents an extension of an earlier paper by the authors (1995), concerned with the development of a single-input single-output (SISO) neural controller for the ship track-keeping problem. Here the single-input parameter remains as the rudder, but now a multiple output strategy based on the tracking error and heading error (SIMO) is developed and then applied to the same problems investi... View full abstract»

An identification algorithm for time-varying nonlinear systems using a sequential learning scheme with a minimal radial basis function neural network (RBFNN) is presented. The learning algorithm combines the growth criterion of the resource allocating network of Platt with a pruning strategy based on the relative contribution of each hidden unit of the RBFNN to the overall network output. The perf... View full abstract»

Owing to the large number of free control parameters for modern nonlinear robust controllers, it is almost impossible to heuristically tune these parameters. The multiobjective fuzzy genetic algorithm optimisation is shown to provide an effective, efficient and intuitive framework for selecting these parameters. The control structure and specifications are assumed to be given. Using the concept of... View full abstract»

The design of robust state feedback controllers for a class of uncertain linear time-delay systems with norm-bounded uncertainty is presented. The state feedback results extend previous results on quadratic guaranteed cost control to the case of uncertain time-delay systems. This is done by the authors' definition of quadratic stability for uncertain time-delay systems with norm bounded uncertaint... View full abstract»

The authors present a novel reduced-order observer for large-scale continuous-time systems. The dynamics of the reduced-order observer are derived only from the set of unstable and/or poorly damped eigenvalues of the system. This makes the proposed observer very attractive for applications to systems with high dimensionality. A simple and systematic design method is presented and a numerical examp... View full abstract»