Thesis defense of Mikel Izquierdo

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Thesis defense of Mikel Izquierdo

Thesis

Thesis defense of Mikel Izquierdo

Title of the thesis: Wheel track variation mechanism comprising inertial dampers to enhance the dynamic performance of an electric three-wheeler. Obtained the SOBRESALIENTE CUM LAUDE rating.

2018·03·16

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  • Títle of the thesis: Wheel track variation mechanism comprising inertial dampers to enhance the dynamic performance of an electric three-wheeler.
  • PhD programme: DOCTORATE PROGRAMME IN MECHANICAL ENGINEERING AND ELECTRICAL ENERGY
  • Thesis directors: Ibai Ulacia Garmendia, Ivan Gallego Navas
  • Court:

Abstract

Traffic congestion, pollution and the lack of parking spaces are some of the main concerns that overpopulated cities are confronting. In addition, the continuous growth of world population and the migration from rural to urban areas will magnify these issues in the near future. In consequence, a trend to develop compact personal mobility three wheelers is identified. These vehicles, due to their reduced footprint, have the potential to reduce traffic congestion and improve park ability, while minimum safety, comfort and rollover values need to be maintained. In this vein, different approaches such as tilting or semi-active and active damper [suspension mechanisms are found in the literature.

The present thesis studies a track variation mechanism that increases a three wheeler track for dynamic driving situations, while a narrow track is set up for parking and low speed driving conditions. The mechanism also comprises a passive inertial damper technology to enhance the dynamic rollover performance of the vehicle. Therefore, a modular track variation mechanism which varies the track width from 1400 mm (open) to 1000 mm (closed) and enables its integration in an L5 category three wheeler electric vehicle has been developed. Moreover, custom made independent suspension and steering components development are also presented.

With the aim of quantifying the improvement in rollover introduced by the developed mechanism, different analytical rollover formulations have been found in bibliography. However, they only studied lumped parameters of vehicle models, considering limited vehicle parameters that affect rollover behaviour. In order to take into account more vehicle parameters and combine its longitudinal and lateral dynamic behaviour, a three wheeler multi-body model has been created. It is also demonstrated that results from the stationary analytical models found in literature differ from presented multi-body model results.

Likewise, only 2DoF studies are found in literature to study inertial dampers' performance. Nevertheless, these studies have demonstrated that despite damper parameters were adjusted by trial and error methods, this technology reduces vertical sprung mass acceleration in comparison to passive conventional dampers, while handling values are maintained. Therefore, in the present thesis the inertial dampers are modelled using both 2DoF and full vehicle multi-body models, identifying inertial damper parameters by a global surface response optimization method. Using these models, it has been virtually demonstrated that four wheeler and three wheeler vehicles' vertical and lateral dynamic metrics are improved.

Finally, kinematic and dynamic suspension tests, damper characterisation tests and wheel track variation mechanism tests have been performed. For these trials, a quarter car suspension bench and a track variation test structure have been developed. They have shown a correct correlation between theoretical an experimental results, both kinematic and damper characterisation. In addition, developed suspension's vertical dynamic behaviour results are shown and track variation mechanism loads for different working conditions are also determined.