Hybrid electric vehicles are becoming increasingly common within the automotive market. Whilst there have been a large number of studies investigating hybrid electric vehicle drive-train control, for efficiency and active safety purposes, there is little work reflecting the effects of such technologies on pure vehicle dynamics. This thesis investigates the effects of hybrid drive-trains on vehicle ride and handling. A specific case study based on the hybridisation of a conventionally powered vehicle into a series hybrid electric vehicle is utilised as a means of doing so. In order to investigate the effects of the hybrid drive-train components on the vehicle’s ride and handling responses, detailed multibody models of both the Standard Vehicle (SV) and the hybrid General Technology Vehicle (GTV) were produced. As work was conducted in parallel with the Low Carbon Vehicle Technology Project (LCVTP), these models were created in a modular and physical fashion, as to allow for their easy parameterisation and adaption into other hybrid vehicle architectures. Prior to detailed investigation the standard vehicle model was successfully validated against real world test data collected as part of this work. Model responses for both the standard and hybrid vehicle models were investigated and analysed in the ride and handling domain. Ride analysis focused on statistical investigation of contact patch load and occupant comfort levels inside the vehicle. It was shown that there was a higher comfort region within both vehicles around the Cog and spring centre, as these two vehicle parameters moved with changes that were made to the GTV, the occupants within were subjected to different comfort levels. As the weight shifted rearwards in the GTV, occupants seated at the front were subjected to higher levels of discomfort, however those in the rear actually saw a slight increase in comfort levels. Levels of vertical acceleration within the GTV were found to generally be slightly larger, resulting from increased pitch and bounce motions due to an increase in coupling between these modes. Furthermore levels of low speed damping on the GTV were shown to be incorrect for its new mass parameters, which led to a further deterioration in ride quality. The handling analysis took on a novel form of investigating trends in specific handling metrics over the entire vehicle operating range. Said trends were then investigated further through more detailed model outputs. The GTV was shown to have a lower understeer gradient than the SV, due to the rearward shift in mass distribution and stiffer rear suspension. Transient handling responses were shown to be quite speed and manoeuvre specific, but all differences between the two vehicles could be explained by the differences in their dynamic indices and understeer gradients. Lateral acceleration response times were governed by the dynamic index and were always slower for the GTV, the magnitude of these responses were speed dependant, below the GTV’s tangent speed they were smaller than the SV’s, however above this speed they were larger. Yaw rate responses were more mixed, but were also seen to be governed by the dynamics index, at lower speeds or during simple unidirectional manoeuvres the GTV could obtain large faster yaw rates than the SV, during a transient to transient manoeuvre the GTV’s yaw rate responses were generally smaller, this was seen to be due to the way in which a higher dynamic index effects rear tyre slip angle generation having a larger effect at low speeds but a smaller effect when large slip angles are already present at the rear tyres. The results obtained have given a clear picture of how the inclusion of hybrid drive-trains can affect vehicle ride and handling. Something that was re-enforced by the results being generalised and applied to a few types of hybrid vehicle architecture in order to make recommendations on layout/packaging of these vehicles and highlight areas of importance for future hybrid vehicle design in terms of ride and handling.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:644925 |
| Date | January 2014 |
| Creators | Bastin, Matthew |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/67141/ |
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