Vehicle dynamic tire force measurement using a bolt-on wheel force transducer

A portable device for measuring tire-pavement forces, the Wheel Force Transducer (WFT), has been tested and evaluated. Results from the WFT are compared with those from two standard, established methods of force measurement, namely, the wheel scale and strain gaged axle. It is shown that the WFT is a very promising device for measuring dynamic vertical and horizontal forces at the tire-road interface. However, performing a detailed study of the WFT is found necessary. This is on account of some discrepancies noticed on comparing the results obtained from the WFT and the axle strain gage in the case of dual tire assemblies subjected to uneven loading.; A model of the WFT is developed, based on simple beam theory. The model is general enough to accommodate all possible configurations of strain gage alignments on the WFT, and it can be used to predict force measurement errors resulting from any misalignments. It is shown that strain gage misalignments can potentially have a significant effect on force measurements. Experimental results are presented from static and dynamic tests performed on the WFT and axle strain gage. Causes of observed discrepancies between results are postulated and discussed. It is established that bending moments and axial forces play a significant role in WFT and axle strain gage outputs. Strain gages for sensing bending moments are therefore mounted on the WFT to provide a complementary source of data that can be used to obtain a better estimate of tire-pavement forces. A comprehensive multivariate calibration model of the WFT is developed to include the effects of bending moments and extraneous forces. This model is subsequently used for calibration and force computation purposes.; A frequency domain method is presented for identifying and correcting interbridge phase error. Identification of transducer parameters is also done through an offline, recursive estimation technique in the time domain. Two new error compensation strategies are presented for application to computed vertical forces, making use of WFT and axle strain gage data. It is seen that a systematic combination of data from two sensors gives better results compared to those obtained from using just one sensor. Further, two new methods are presented for computing vertical and horizontal wheel forces and also the location of vertical force. These methods would be useful in cases where dual tire assemblies are subjected to uneven loading. It is recommended that bending moment gages be incorporated into the current WFT design, as this would lead to a more accurate device for measuring tire-pavement forces.