Abstract
Research question: Tilting vehicles like motorbikes and scooters are much more dangerous and often less comfortable to operate compared to cars. Semi-active and active suspensions are often used in luxury cars to improve the dynamic behaviour and to be able to adjust it to different driver preferences and needs. The research question is how electro-rheological dampers can improve the dynamics of a tilting vehicle with three wheels.
Methodology: The benefits of the electro-rheological dampers are investigated through simulations. The tilting three wheeled vehicle was described with a planar single track model. This model consists of three bodies for the torso and two wheels. The damper’s electro-rheological fluid (ERF) is regarded as compressible and has a mass inertia inside the damper’s annulus. A front- and rear wheel chassis dampers were investigated.
Based on the damper characteristics of the presently implemented shocks that were characterized in bench tests, comparable ER-dampers have been designed and the expected damping fields calculated. This procedure was carried out for both front and rear dampers, which have very similar damping characteristics. The Bingham model was used to calculate the volume flow through the ER dampers. Finally the damping performance for the different deigns is simulated for different for driving over an obstacle.
Results: Heave and pitch together with relevant frequencies were calculated for driving over an uneven road surface. The helix free damper performed very well, both heave and pitch dampened in very short times. Heave velocity and pitch were compensated to zero immediately after the event compared to around 5 seconds for heave and around 4 seconds for pitch without activation of the ER damper. Maximum damping forces were below 330N with a maximum voltage below 4000 Volts for both, the front and rear dampers compared to below 200N without activation.
Limitations: The study included only one road surface unevenness and one vehicle mass. In the future further more complex driving manoeuvres should be performed that also should include different driver masses. Due to budget constraints physical bench tests were only conducted for the conventional dampers. Also the development of a relevant control strategy was outside the scope of this paper.
Novelty: The design and simulation of electro-rheological damper for a tilting three wheeled vehicle is new, both with and without the application of voltage to control the dampers.
Conclusions: Two types of electro-rheological dampers for a tilting three wheeled vehicle have been designed and analysed. Simulations have been completed that show that both damper types perform exceptionally well to dampen heave and pitch when driving over uneven ground. The low cost helix free dampers are the preferred design as they perform adequately even without the need to use the limitations of the available force ranges.
KEYWORDS – Tilting vehicles, dampers, electro-rheological fluids, three wheelers