Optimisation of the weighting functions of an H_∞ controller using genetic algorithms and structured genetic algorithms

In this paper the optimisation of the weighting functions for an H<sub>∞</sub> controller using genetic algorithms and structured genetic algorithms is considered. The choice of the weighting functions is one of the key steps in the design of an H<sub>∞</sub> controller. The performance of the controller depends on these weighting functions since poorly chosen weighting functions will provide a poor controller. One approach that can solve this problem is the use of evolutionary techniques to tune the weighting parameters. The paper presents the improved performance of structured genetic algorithms over conventional genetic algorithms and how this technique can assist with the identification of appropriate weighting functions' orders

Genetic programming for the automatic design of controllers for a surface ship

In this paper, the implementation of genetic programming (GP) to design a contoller structure is assessed. GP is used to evolve control strategies that, given the current and desired state of the propulsion and heading dynamics of a supply ship as inputs, generate the command forces required to maneuver the ship. The controllers created using GP are evaluated through computer simulations and real maneuverability tests in a laboratory water basin facility. The robustness of each controller is analyzed through the simulation of environmental disturbances. In addition, GP runs in the presence of disturbances are carried out so that the different controllers obtained can be compared. The particular vessel used in this paper is a scale model of a supply ship called CyberShip II. The results obtained illustrate the benefits of using GP for the automatic design of propulsion and navigation controllers for surface ships

A LEGO-based control experiment

A nice feature of the LEGO system is that, although the mechanical, electrical, and structural construction is good enough for successful results, there are enough discrepancies between theory and practice to introduce the student to real-world problems of controller. This article concentrates on implementing the feedback controller within the RCX, with the host computer used for compiling, downloading, and data display. However, an interesting research project is to implement part of the controller on the host computer and communicate by means of the IR channel. The bandwidth restriction that this approach imposes can provide the basis for a research project on control through a restricted bandwidth channel

Using LEGO in control education

Experiences at Glasgow University in using LEGO Mindstorms for Control Education are described and implementation details given

Comment on "Nonlinear optimal tracking control with application to super-tankers for autopilot design" by T. Cimen and S.P. Banks

A recent paper by Cimen and banks [2004. Nonlinear optimal tracking control with application to super-tankers for autopilot design. Automatica, 40(11), 1845-1863] on optimal control system design for oil tanker propulsion and heading highlighted the importance of accurately representing the dynamics of such a vessel. Results presented in that paper are based on a simulation model that provides unrealistic results for an oil tanker of the size considered. Therefore the results obtained from the simulated ship control problem are not representative of the physical system being considered. In this communication an alternative, more realistic model is presented and discussed with reference to the original publications that define the ship model dynamics

A case study involving continuous system methods of inverse simulation for an unmanned aerial vehicle application

Inverse simulation allows input time histories to be found that generate specified outputs for non-linear dynamic models in cases where analytical methods of inversion present difficulties. The two approaches considered involve continuous system simulation principles. One is an approximate differentiation method while the second involves feedback principles. These approaches are compared for a non-linear six-degrees-of-freedom flight-mechanics model of a fixed-wing unmanned aerial vehicle incorporating actuator sub-models with saturation and rate limits. Additional insight is provided through analysis of a linearised version of the vehicle model. It is concluded that both the continuous system simulation methods for finding inverse solutions, for the type of application described in this paper, provide a useful alternative to more conventional iterative methods of inverse simulation based on discrete models. In many cases, including those involving hard non-linearities in control surface actuator sub-systems, they allow issues of vehicle handling and manoeuvrability to be addressed in a more direct fashion than is possible using conventional simulation methods alone

Using LEGO in control education

Experiences at Glasgow University in using LEGO Mindstorms for Control Education are described and implementation details given