Thesis (Ph. D.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

M.Ing. (Mechanical Engineering) / A hydromechanical traction system for a wheeled vehicle is being examined in order to generate information that will be applicable to the design of the drive system controller. The functional analysis of the drive system leads to the description of the system and component properties. A design methodology is proposed by which the system components could be dimensioned and the system layout constructed by taking into account the specified functional requirements concerning the system performance. An explicit description of power flow and manipulation of power flow in the drive system is given. The mechanisms by which the hydraulic machines are adjusted to manipulate power flow, are examined in detail so that their contribution to the dynamic behaviour of the total drive system can be described. , Experimental measurements are used to obtain a reliable description of the dynamic response of the adjustment mechanisms. An analytical model of the dynamic behaviour of the drive system is presented in block diagram format. The inherent multiple-input-multiple-output characteristic of the drive system with secondary controlled hydraulic motors is discussed. The block diagram is simplified to create linearized transfer functions that will depict the input-output-relationships. The effect of an accumulator on the dynamic response of the system is also given. Digital simulation programmes are constructed from the analytical model. The requirements of a vehicle traction system are interpreted and used as guidelines to conduct a functional design of the control system layout. The delivery of torque and the restriction of wheel spin for each of the wheel drive units, which is realised by secondary controlled hydraulic motors, are described in detail. A hypothetical drive system is considered and quantitive control system design information is generated, using the simulation programmes. Some aspects of the dynamic response of the system are discussed and it is shown that the adjustment mechanism has a big influence on the overall dynamic response of the system.

Thesis (doctor)--Technische Universiteit Delft, 1997. / Vita. Includes bibliographical references (p. [153]-162).

Thesis (doctor)--Technische Universiteit Delft, 1997. / Vita. Includes bibliographical references (p. [153]-162).

The thesis describes an optimal selective harmonic elimination strategy suitable for singlephase AC-DC converter-fed traction drives. The objective is to eliminate low-order supply current harmonics, including those injected into the supply due to load-side current ripple. Other advantages that the switching strategy has to offer over phase-control include improved supply power factor, reduced VA consumption for a given demand speed and load, reduced torque and speed ripple and smaller armature circuit smoothing inductance. The effect of field current boost on the dynamic response of the drive is also described. It is shown that field boost helps to reduce the speed rise-time by increasing the electromagnetic torque available during acceleration periods. Closed-loop control of a 4-quadrant DC drive is described and a comparison made between the performance of PID-control and pseudo-derivative feedback control. It is shown that pseudo-derivative feedback control has several advantages to offer, amongst which are ease of tuning of the controller gains and a superior performance following load torque disturbances. A laboratory size drive system was designed and built, and used to validate simulation predictions for both the switching strategy and pseudo-derivative feedback control. A microcontroller based hardware implementation of both the switching strategy and a digital pseudo-derivative feedback controller was adopted, with the switching strategy being implemented using an off-line approach of precalculating the switching angles and storing these in look-up tables. The armature voltage controller comprises a dual-converter employing IGBTs as switching devices. The use of IGBTs allows higher switching frequencies at significant power levels than would be possible if GTOs were used. It also simplifies the gate drive circuit design and minimises the need to use snubber circuits.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

This thesis presents a detailed comparison of the torque-speed characteristics of three permanent magnet synchronous machine designs based on how the magnets are mounted. The machines investigated are an interior permanent magnet machine, an interior-rotor surface-mounted machine and an exterior-rotor surface-mounted machine. They are designed for traction drives in hybrid electric vehicles. Two sets of comparisons based on the same machine volume and starting torque are performed. Important issues, such as machine mass and cost, cogging torque, and flux-weakening capability are addressed. Computer simulations were performed to estimate their performances and the results are presented. Design guidelines and tradeoffs of their performances are extracted from the simulation results. Relative strengths and limitations of different PM machine types are highlighted.

No description available.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / The work presented in this thesis forms part of the participation of the University of Stellenbosch in an electric vehicle project. The thesis deals with three aspects of the dynamics and energy management of the electric vehicle. The three aspects that are dealt with are the suspension system of an electric vehicle with in-wheel propulsion, the traction control of an electric vehicle and the energy system of such a vehicle. An investigation is presented in the thesis on the effect the mass of the hub motors has on the safety, stability and comfort of the electric vehicle. The investigation is done through a system frequency analysis and a comparative simulation. A comparison is made between a standard vehicle and a vehicle with in-wheel propulsion. A vehicle model is derived for the simulation of the vehicle. Finally, a few of the results of physical measurements performed are also presented. The traction control requirements of an EV are investigated. A discussion is given on the parts that make up an EV’s traction control system. A few examples of possible traction control systems are given through a step by step evolution of a traction control system. A vehicle model is derived for both static and kinetic friction conditions. The model is used in simulations to illustrate the need for traction control in EV’s. The thesis presents two methods for choosing a battery pack size, in terms of energy capacity etc. The difficulties associated with choosing a battery pack, using each of these methods are given. A battery pack choice for the specific electric vehicle, is presented. The measurements of one of the required charge-discharge cycles are presented to illustrate the charge and discharge curves of the battery cells used. The management of energy flow within the energy system of the EV is crucial, especially if regenerative braking is utilized. This is to protect the battery cells as well as to extend the range of the vehicle. The thesis presents the evaluation of an energy management system (EMS) using ultra capacitors as auxiliary storage device. An electronic load system is designed to simulate the operation of the vehicle motors. The transfer functions for the EMS and load system are derived and used to design the respective control algorithms. The control algorithms were implemented in both simulation as well as a laboratory setup to show the operation of the EMS. A new energy system configuration is presented. The aim of the new configuration is to solve certain problems encountered when implementing a conventional EMS. The operation of the new configuration is discussed. A comparative study is made between the conventional and the new configurations.