Browsing by Author "Vaughan, Nicholas D."

Now showing 1 - 5 of 5
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    Cavitation induced starvation for piston-ring/liner tribological conjunction.
    (Elsevier, 2011-04) Chong, William Woei Fong; Teodorescu, M.; Vaughan, Nicholas D.
    The study investigates the mechanism of ring-liner lubrication in the vicinity of the top and bottom dead centres of an internal combustion engine. Predicting lubricant transient behaviour is critical when the inlet reversal leads to thin films and inherent metal-to-metal interaction. It was found that the cavitation, which is located at the trailing edge of the contact before reversal, briefly survives after reversal as a confined bubble at the leading edge. This depletes the film promoting starvation. Several algorithms were compared. It is concluded that the lubricant film is thinner than initially thought.
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    A classical control approach to the power management of an all-electric hybrid vehicle.
    (2009-01-01T00:00:00Z) Marco, James; Vaughan, Nicholas D.
    Modern hybrid electric vehicles (HEVs) often employ all-electric powertrains that utilise hybrid sources of power and energy; such as batteries, fuel cells and ultracapacitors. This paper describes the design, simulation and experimental verification of a power management control system that manages a high voltage battery, a DC-DC boost converter and an ultracapacitor within a front-wheel drive HEV in which the motive power for the vehicle comes from two electrical machines. As part of this study, consideration is given to the complete control system design life-cycle including plant model development, algorithm design and software implementation on the target electronic control unit (ECU). Off-line simulation and initial experimental results are presented showing the vehicle operating on a powertrain dynamometer as one means of demonstrating the ability of the ultracapacitor to limit the transient demands placed on the battery during periods of vehicle acceleration and regenerative braking.
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    Design of a reference control architecture for the energy management of electric vehicles
    (Inderscience, 2012-12-31T00:00:00Z) Marco, James; Vaughan, Nicholas D.
    The High-Voltage (HV) network within an Electric Vehicle (EV) will typically comprise different energy sources such as fuel cells, batteries and ultracapacitors integrated together through the use of both unidirectional and bidirectional DC-DC converters. Given the multitude of feasible HV network designs, there are obvious advantages in having a unifying control architecture that facilitates the Energy Management (EM) control task. Within this paper, a control Reference Architecture (RA) is proposed that can be employed as a template for the design of the EM control function. Example EM control systems are presented each derived from the same RA, but relating to a different physical configuration of HV network. Simulation results are presented to verify the functional performance of the control systems. In each case, the design trade-offs associated with the functional performance of the EM strategy and the non-functional requirements of modularity and reusability are discussed.
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    Feasibility of High-Frequency Alternating Current Power for Motor Auxiliary Loads in Vehicles
    (IEEE Institute of Electrical and Electronics, 2011-02-02T00:00:00Z) Antaloae, C. C.; Marco, James; Vaughan, Nicholas D.
    This paper presents a feasibility study into the application of a 100-V, 50-kHz high-frequency ac (HFAC) network for powering automotive electrical auxiliaries. The study is focused on motor-actuated loads and is divided into two sections. First, the investigation indicates the benefits of replacing low-torque dc motors with lighter and more efficient 400-Hz ac machines for applications such as electric fans, fuel pumps, or blower motors. A comparative examination of commercially available machines indicates space and weight reduction of more than 60%, and efficiency savings between 25% and 100% are possible. Second, the inquiry evaluates the viability of replacing existing dc/ac inverters with HFAC/ ac converters for high-torque ac machines as employed, for example, in electric- power-assisted steering (EPAS) or heating, ventilation, and air conditioning systems. Based on experimental and simulation results for a column-assist EPAS application employing a three-phase permanent-magnet synchronous motor, this paper shows that an HFAC drive is expected to reduce the voltage harmonic content below 50 kHz by at least 10% compared with the dc/ac inverter. However, the disadvantages of the former drive make it less attractive than the existing dc/ac circuit. Specifically, the EPAS motor torque ripple is expected to be approximately 2% higher compared with the dc counterpart drive. Further drawbacks of the HFAC/ac drive include high metal-oxide-semiconductor field- effect transistor (MOSFET) conduction losses, higher voltage harmonics above 50 kHz, and complex control requirements of the inverter. Conclusively, significant HFAC advantages for motor loads can only be attributed to machines with a nominal torque capability that is limited to 2 N ·m. However, given the number of such devices within a typical vehicle, this translates into a possible vehicle mass saving of 30 kg and a potential reduction in fuel consumption by 0.8 L/100 km
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    Optimal time and handling methods for motorsport differentials.
    (Cranfield University, 2014-12) Tremlett, Anthony; Assadian, Francis; Vaughan, Nicholas D.
    In the motorsport environment, where traction at one wheel is often compromised due to high cornering accelerations, Limited Slip Differentials (LSD) offer significant improvements in traction and vehicle stability. LSDs achieve these performance benefits through the transfer of torque from the faster to slower rotating driving wheel. In the majority of racing formulae, modern devices have evolved to become highly adjustable, allowing this torque bias to alter both ultimate vehicle performance and handling balance through specific corner entry, apex and corner exit phases. This work investigates methods to optimise LSD setup parameters, both for minimum lap time and desirable handling characteristics. The first stage of addressing this objective involved the creation of a range of contemporary motorsport LSD models. These included a plate or Salisbury type, a Viscous Coupling (VC) and a Viscous Combined Plate (VCP). A differential test rig was developed to validate these models. The parameter optimisation is addressed in two main parts. Firstly, a Quasi Steady State (QSS) time optimal method is used to maximise the vehicle's GG acceleration envelope using a direct, nonlinear program (NLP). A limitation of this approach however, is that system transients are neglected. This is addressed through the development of an alternative indirect, nonlinear optimal control (NOC) method. Both methods were able to find LSD setup parameters which minimised lap time, providing significant improvements over traditional open and locked devices. The NOC method however, was able to give greater insight into how a locked device ultimately limits the vehicle yaw response during quick direction changes. The time optimal analysis was extended to investigate aspects of vehicle stability and agility. These factors are known to have a major influence on driveability and thus, how much of the theoretical performance limit the driver can extract. A more unified GG diagram framework was implemented, to characterise both the vehicle's acceleration limits, and how its stability and agility changes leading up to this limit. The work has generated a number of novel contributions in this research field. Firstly, the creation and validation of a range of state-of-the-art motorsport LSD models. Secondly, the methodologies used to optimise LSD setup parameters, the results from which, have themselves provided the basis of a novel, vehicle speed dependent LSD device. Finally, a more practical and intuitive way to evaluate vehicle stability and agility at different cornering phases. This has laid the foundations of a procedure which not only maximises the vehicle's acceleration limits, but also allows its response to be tailored to suit individual driver preferences.