Thesis (MTech( Electrical Engineering)) -- Cape Peninsula University of Technology, 2012 / Due to the complex design of existing electric mobility vehicles in South Africa and their imported parts, make them unaffordable to the majority of disabled people in South Africa. The traditional electric units are also not practical for use in rural areas due to the heavy, bulky design. The scope of this study was to investigate various designs using existing wheelchair frame designs, low cost three phase hub motors and various electronic techniques to achieve the desired functionality. An attempt was be made to remove inefficient and expensive DC brush motors and the gear boxes associated with the traditional design of wheelchairs, while still allowing the unit to fold like the traditional manual chair design. One of the aims for this electric wheelchair was to utilise existing large radius wheels, typical of manual wheelchairs and a modified traditional frame design, providing the clearance often necessary to overcome rough terrain whilst enabling the chair to be used as a manual wheelchair should the battery fail. One of the primary aims of the project was to develop a method for an electric assist feature built into the modified electric wheelchair, whereby the force applied to the manual pushrims on the wheels would be measured and the electric component would proportionally assist the user. This option suits the users who are weak but not physically disabled. One of the many focal points here would be on HIV/AIDS patients, which is prevalent in South Africa, who may require a wheelchair when debilitated with this disease. The electric assist portion of the design would act similarly to a wireless self-powered torque sensor, allowing for an array of applications besides the electric assist portion of this project. A recent survey by National Government indicated that over 85% of wheelchair users only generated an income of between R0 – R500 per month. Low state disability grants and wage figures for disabled and HIV/AIDS patients mean that electric mobility vehicles have become a luxury rather than an essential commodity in South Africa. The need for cheap electric wheelchairs that could cope with the rural terrain and could be fitted onto existing manual wheelchairs offering the full manual operation should the batteries go flat, was clearly apparent. The cost of an electric wheelchair ranges from R18 000 with more advanced models escalating in price to well over R150 000. These prices were typically the result of the complexity of the unit and local wheelchair manufacturers having to import 80% of their parts from abroad. The largest local manufacturer is CE Mobility which is the dominant mobility vehicle supplier in Southern Africa and has the only SABS approved units for sale. Our complete redesigned wheelchair including the manual frame supplied by an existing supplier would only cost R9 000. A prototype demonstrated that is was possible to build a wheelchair that meets all these criteria. A cost effective unit could provide a solution to assist and enable economically challenged and disabled people in rural areas of Southern Africa.

Fault-tolerant vehicle design is an emerging inter-disciplinary research domain, which is of increasedimportance due to the electrification of automotive systems. The goal of fault-tolerant systems is to handleoccuring faults under operational condition and enable the driver to get to a safe stop. This paperpresents results from an extended survey on fault-tolerant vehicle design. It aims to provide a holisticview on the fault-tolerant aspects of a vehicular system. An overview of fault-tolerant systems in generaland their design premises is given as well as the specific aspects related to automotive applications. Thepaper highlights recent and prospective development of vehicle motion control with integrated chassiscontrol and passive and active fault-tolerant control. Also, fault detection and diagnosis methods arebriefly described. The shift on control level of vehicles will be accompanied by basic structural changeswithin the network architecture. Control architecture as well as communication protocols and topologiesare adapted to comply with the electrified automotive systems. Finally, the role of regulations andinternational standardization to enable fault-tolerant vehicle design is taken into consideration. / <p>Qc 20120730</p>

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The aim of electrification of chassis and driveline systems in road vehicles is to reduce the global emissions and their impact on the environment. The electrification of such systems in vehicles is enabling a whole new set of functionalities improving safety, handling and comfort for the user. This trend is leading to an increased number of elements in road vehicles such as additional sensors, actuators and software codes. As a result, the complexity of vehicle components and subsystems is rising and has to be handled during operation. Hence, the probability of potential faults that can lead to component or subsystem failures deteriorating the dynamic behaviour of road vehicles is becoming higher. Mechanical, electric, electronic or software faults can cause these failures independently or by mutually influencing each other, thereby leading to potentially critical traffic situations or even accidents. There is a need to analyse faults regarding their influence on the dynamic behaviour of road vehicles and to investigate their effect on the driver-vehicle interaction and to find new control strategies for fault handling. A structured method for the classification of faults regarding their influence on the longitudinal, lateral and yaw motion of a road vehicle is proposed. To evaluate this method, a broad failure mode and effect analysis was performed to identify and model relevant faults that have an effect on the vehicle dynamic behaviour. This fault classification method identifies the level of controllability, i.e. how easy or difficult it is for the driver and the vehicle control system to correct the disturbance on the vehicle behaviour caused by the fault. Fault-tolerant control strategies are suggested which can handle faults with a critical controllability level in order to maintain the directional stability of the vehicle. Based on the principle of control allocation, three fault-tolerant control strategies are proposed and have been evaluated in an electric vehicle with typical faults. It is shown that the control allocation strategies give a less critical trajectory deviation compared to an uncontrolled vehicle and a regular electronic stability control algorithm. An experimental validation confirmed the potential of this type of fault handling using one of the proposed control allocation strategies. Driver-vehicle interaction has been experimentally analysed during various failure conditions with typical faults of an electric driveline both at urban and motorway speeds. The driver reactions to the failure conditions were analysed and the extent to which the drivers could handle a fault were investigated. The drivers as such proved to be capable controllers by compensating for the occurring failures in time when they were prepared for the eventuality of a failure. Based on the experimental data, a failure-sensitive driver model has been developed and evaluated for different failure conditions. The suggested fault classification method was further verified with the conducted experimental studies. The interaction between drivers and a fault-tolerant control system with the occurrence of a fault that affects the vehicle dynamic stability was investigated further. The control allocation strategy has a positive influence on maintaining the intended path and the vehicle stability, and supports the driver by reducing the necessary corrective steering effort. This fault-tolerant control strategy has shown promising results and its potential for improving traffic safety. / <p>QC 20150520</p>

The aim of this thesis is to create a flexible multi-purpose modular all terrain robot platform, which has the potential to be used in commercial applications as well as in education and research. In developing this robot platform, it is aimed to use readily available commercial products as much as possible in order to keep the cost of the product low, increase maintainability, and benefit from the improvements made to these components in time. The modularity is attained by designing a two wheeled base module which is autonomous on its own. This base module is composed of two wheels where, the motors located inside these wheels. It is shown that the proposed base module facilitates the configuration of various robots to suit the needs of diverse applications. Detailed design and manufacturing of one of various possible configurations is presented. Performance tests are conducted on this robot configuration and effectiveness of the proposed modular approach is justified.

The main aim of this thesis is to design electric scooter, which is ideally adapted for urban mobility and which will be a practical, attractive and environmental friendly alternative to the car with a combustion engine. Emphasis is given to proposal of ergonomic, aesthetic and functional solution of the system, which makes that scooter can be folded into a mobile compact shape. Folded scooter can be carried at public transportation vehicles and park right at home or in the office. The unique design and practical features of a scooter should be attractive not only in terms of personal mobility, but also as a utility vehicle for private companies and public institutions.

In this thesis, the feasibility to integrate an brake disc and electric machine is investigated. In wheel motors (IWMs) have several advantages, such as saving space in the vehicle, individual and direct control at the wheels and the absence of a mechanical transmission. However, today’s IWMs are heavy and, thus, negatively affect the driving performance of the vehicle due to the increase of the unsprung mass. By integrating an already existing part in the wheel, this increase of the unsprung mass can be minimized. The brake disc manages high temperatures, a significant wear in rough environ-ment, which puts high demands on the rotor. The second part of the machine, the stator, will be significantly affected by the high temperatures of the rotor. The temperatures of the stator are transferred by convection, conduction and radiation from the rotor or brake disc. Liquid cooling of the stator back is analyzed as a potential solution for handling the high temperatures. In order to analyze the feasibility of the concept, thermal, electric and mechanical modelling has been used. The evaluation whether it is possible or not to integrate the brake disc has been with regard to the results of weight, cost, thermal tolerance and electric performance. / I detta arbete undersöks möjligheten att integrera en bromsskiva med elmaskin. Hjul-motorer har flera fördelar, bland annat sparas utrymme i själva bilen, individuell kontroll samt drivning av hjulen utan mekaniska transmissioner. Men hjulmotorer som kan användas idag väger oftast så pass mycket att den odämpade massan ökar kritiskt och köregenskaper av fordonet då blir lidande. Genom att integrera en befintlig del i hjulet kan ¨okningen av odämpade massan minskas. Att använda bromsskivan som rotor, kräver att denna tål temperaturer ¨over 500◦C samt påfrestningar och slitage som en vanlig mekanisk friktionsbroms måste uthärda. Den andra delen av maskinen, statorn kommer även denna att påverkas av de höga temperaturerna av bromsskivan som kommer ledas via konvektion, konduktion och strålning. Möjligheten att kyla statorn med vätska och om detta är tillräckligt undersöks. För att analyserna genomförbarheten av projektet har termiska, elektriska och mekaniska modeller använts. Resultaten har analyserats där maskinens vikt, kostnad, termisk tålighet och elektrisk prestanda har legat till grund för bedömningen om lösningen; att integrera en broms-skiva med elmaskin är rimlig eller ej.