Tyres behave similar to a spring and damper systems smoothing out road irregularities as the tyre rolls. Tyre stiffness and damping characteristics are largely influenced by the tyre pressure. As a result, tyre pressure has an influence on tyre enveloping and ride comfort.
To take advantage of the influence of tyre pressure on ride comfort, a pressure controlled tyre was developed to vary the tyre pressure, thus varying the tyre characteristics as the road conditions change to improve ride comfort. Literature exists on TIS (Tyre Inflation Systems) and smart suspension control strategies optimised for ride comfort, which indicate that a pressure controlled tyre can be developed by managing a TIS with a ride comfort controller.
A VDG (Vehicle Dynamics Group) test trailer was used to complete this study. The trailer was modelled on three platforms; MATLAB, Cosin and ADAMS View; with the co-simulation managed through Simulink. Three tests were conducted to parametrise and validate the model, namely; pneumatic system parametrisation tests, APG (Aberdeen Proving Ground) bump tests and Belgian paving tests. The pneumatic system parametrisation tests show that the discharge coefficient is approximately 0.07 for choked flow and tappers off to zero for unchoked flow. Also, tests show that the tyre can be inflated from 1.0 bar to 3.0 bar in 8 s and deflated from 3.0 barto 1.0 bar in 13 s. The APG bump tests and Belgian paving tests were conducted to validate the model over discrete obstacles and rough roads, respectively. These tests indicate that the model correlates with the actual trailer.
The validated model was used to develop the TIPc (Tyre Inflation Pressure controller), which uses a running RMS control strategy to manage the TIS. The objective of the TIPc is to maintain a NOT uncomfortable ride comfort level. The TIPc achieves this by deflating the tyre to a suitable tyre pressure when the ride comfort level is above NOT uncomfortable. The TIPc is robust to evaluate ride comfort on smooth roads and rough roads, as well as, detecting discrete obstacles. The TIPc ignores discrete obstacles when evaluating ride comfort to determine a suitable tyre pressure to improve ride comfort. The TIPc was able to achieve a 4−7% RCI (Ride Comfort Improvement).
Dissertation (MEng)--University of Pretoria, 2020.