The design and intelligent control of an autonomous mobile robot

This thesis presents an investigation into the problems of exploration, map building and collision free navigation for intelligent autonomous mobile robots. The project began with an extensive review of currently available literature in the field of mobile robot research, which included intelligent control techniques and their application. It became clear that there was scope for further development with regard to map building and exploration in new and unstructured environments. Animals have an innate propensity to exhibit such abilities, and so the analogous use of artificial neural networks instead of actual neural systems was examined for use as a method of robot mapping. A simulated behaviour based mobile robot was used in conjunction with a growing cell structure neural network to map out new environments. When using the direct application of this algorithm, topological irregularities were observed to be the direct result of correlations within the input data stream. A modification to this basic system was shown to correct the problem, but further developments would be required to produce a generic solution. The mapping algorithms gained through this approach, although more similar to biological systems, are computationally inefficient in comparison to the methods which were subsequently developed. A novel mapping method was proposed based on the robot creating new location vectors, or nodes, when it exceeded a distance threshold from its mapped area. Network parameters were developed to monitor the state of growth of the network and aid the robot search process. In simulation, the combination of the novel mapping and search process were shown to be able to construct maps which could be subsequently used for collision free navigation. To develop greater insights into the control problem and to validate the simulation work the control structures were ported to a prototype mobile robot. The mobile robot was of circular construction, with a synchro-drive wheel configuration, and was equipped with eight ultrasonic distance sensors and an odometric positioning system. It was self-sufficient, incorporating all its power and computational resources. The experiments observed the effects of odometric drift and demonstrated methods of re-correction which were shown to be effective. Both the novel mapping method, and a new algorithm based on an exhaustive mesh search, were shown to be able to explore different environments and subsequently achieve collision free navigation. This was shown in all cases by monitoring the estimates in the positional error which remained within fixed bounds

Modelling and Control of Switched Reluctance Machines

Today, switched reluctance machines (SRMs) play an increasingly important role in various sectors due to advantages such as robustness, simplicity of construction, low cost, insensitivity to high temperatures, and high fault tolerance. They are frequently used in fields such as aeronautics, electric and hybrid vehicles, and wind power generation. This book is a comprehensive resource on the design, modeling, and control of SRMs with methods that demonstrate their good performance as motors and generators

High-Performance Control of Switched Reluctance Motors

A general high bandwidth, low ripple, instantaneous torque control strategy with a variable field-angle for extended constant-power speed range is presented. The strategy is based on the SR motor's electromagnetic characteristics measured at the motor terminals and is the nearest functional equivalent to AC vector control for this type of machine. Low torque ripple and high bandwidth are achieved over a wide range of speeds and a constant power range of 3:1. The proposed controller, which is applicable to most SR motors, is found to reduce the torque ripple by a factor of 5 in comparison with conventional square-wave current operation, and has been operated over a speed range of 1:6000

Aktiivinen magneettilaakeri vaihtoreluktanssimoottorina

The goal of this work was to research the similarities between active magnetic bearings and switched reluctance motor and particularly research the chances for converting magnetic bearing into switched reluctance motor. In addition, ways to cope with the widely reported problems the motor type has were studied. The test environment consisted of test rig, previously used for testing control methods for magnetic bearing. In addition to this, MATLAB Simulink simulation models were built to help the designing of the test setup. The test setup had two alternative controllers, an original magnetic bearing controller, modified to work as a motor controller and a new CompactRIO-based controller that was used for comparing different speed control and commutation methods. New rotor designs were engineered to work with the prototype motor that used unmodified magnetic bearing stator. This setup was tested for obtaining the output torque and maximum speed of the motor together with the accuracy to follow set values. Test results of simulations and test setup were inside the error margins, showing the use of simulations beneficial in design process of this type of a motor. The tests revealed differences between the control methods, suggesting using the advanced angle controller and adjustable commutation angles.Työn tavoitteena oli tutkia yhteneväisyyksiä aktiivimagneettilaakerien ja vaihtoreluktanssimoottorin välillä. Tutkimus keskittyi erityisesti arvioimaan mahdollisuuksia muuntaa magneettilaakeri vaihtoreluktanssimoottoriksi. Lisäksi tutkittiin keinoja ratkaista ongelmia, joita tämän tyyppisessä sähkömoottorissa on raportoitu olevan. Testiympäristö koostui roottorikoelaitteesta, jota on aikaisemmin käytetty magneettilaakerin säätöjärjestelmän tutkimuksessa. Lisäksi rakennettiin MATLAB Simulink simulointimalli, jota käytettiin moottorin säätöjärjestelmän suunnittelun apuna. Testilaitteessa oli kaksi vaihtoehtoista säätöjärjestelmää; alkuperäinen magneettilaakerin ohjain muokattuna toimimaan moottorin ohjaimena sekä uusi CompactRIO -järjestelmään perustuva säätöjärjestelmä. Jälkimmäistä käytettiin erilaisten nopeus- ja kommutointitapojen vertailuun keskenään. Prototyyppimoottorin staattori oli sama, jota käytettiin magneettilaakerin kanssa. Roottori suunniteltiin sopimaan juuri tähän käyttötarkoitukseen. Tätä koelaitetta testattiin vääntömomentin ja maksiminopeuden selvittämiseksi. Lisäksi suoritettiin testejä, joissa tutkittiin kykyä seurata nopeuden asetusarvoa. Simuloimalla saadut tulokset olivat hyvin lähellä koelaitteella saatuja tuloksia osoittaen simuloinnin käytön olevan hyödyllistä tämän tyyppisen moottorin suunnittelussa. Säätömenetelmät suoriutuivat vaihtelevalla menestyksellä testeistä. Suositeltava säätömenetelmä oli edistyskulman säädin, joka käytti hyväkseen säädettäviä kommutointikulmia