Abstract
M.Ing.
Vehicles used in military, agricultural, forestry, or construction applications often encounter different road surfaces during a single journey. In order to optimise the mobility of these vehicles, different tyre pressures are required for different types of terrain (sand, mud, cross country, tar road, etc.). An in-motion tyre pressure control system will enable the vehicle's operator to change the tyre pressures without leaving the vehicle. Such a system will not only allow optimum surface contact between the tyres and the terrain - thus improving vehicletraction, but it can also increase the lifespan of the tyres and reduce fuel consumption. The key design criteria for such a system are: quick reaction times, an effective operator interface, and
reliability. In case of system failure, the operator must be able to override the control, and the tyres should be inflated to a pre-set default pressure. When the fault had been corrected, the system can be restarted from within the cabin, to inflate or deflate the tyres as required. The focus of this thesis is on the design criteria of a tyre pressure control system, receiving inputs from the driver and from onboard vehicle sensors; and then adjusting individual tyre pressures if necessary, while the vehicle is on the move. Based on the inputs to the control system, the optimum setting for the tyre pressure is determined from a look-up table stored in memory of an onboard computer. This table contains the pressure-speed and pressure-axle
load relationship. A unique relation is programmed into the microprocessor for each different vehicle. To install a tyre pressure control system on a vehicle, a computer program is used to control the following hardware which are necessary to inflate or deflate tyres: An air compressor and storage tank. Pneumatic valve. Rotating seal. Pressure and speed sensing elements. Electronic control unit. An experimental set-up was built, from various components or sub-systems, which were integrated systematically until the system was working as a unit. The functionality of the system was tested, and although the results obtained do not yet justify the commercial manufacturing of such systems, it is trusted that this research has contributed towards the increased emphasis that is placed upon vehicle safety and comfort systems.