Abstract
The performance of the active safety systems of the vehicle could be significantly increased if more detailed information in real time of the forces applied to the tyre/road contact could be obtained by using economically feasible transducers. However, commercial dynamometric wheels are characterized by a very high cost and may have different inertial properties than the vehicle’s original wheels. The purpose of this paper is to present a novel method for producing dynamometric wheels with a much lower cost than the commercial ones by mounting strain gauges on the wheels of the vehicle in such a way that they are grouped in at least three concentric circumferences and in equidistant radial lines. The strain signals of the same circumference are linearly combined to obtain at least two new signals that only depend on the contact forces and moments. The influence of the angle rotated by the wheel, the temperature or the centrifugal forces is eliminated in these new signals by using a technique based on the elimination Fourier harmonics. The contact forces and moments are obtained from these new signals by solving two systems of linear equations with three unknowns each. The cost of the necessary components to convert a car wheel into a dynamometric wheel is almost two orders of magnitude lower than the price of a commercial dynamometric wheel. A large set of tests has been carried out with a prototype of dynamometric wheel in order to validate this method experimentally. Errors below 2% have been obtained for all the measurements and in most cases they were below 1.5%.
KEYWORDS – Dynamometric wheel, measuring wheel, forces measurement, contact patch, tyre/road contact