A vehicle dynamics-oriented estimator for soft soil/tyre contact parameters from experimental testing

Modelling the interaction between tyres and unconsolidated soft surfaces has assumed a crucial role in predicting off-road vehicle performance in different machine areas such as planetary exploration and agriculture. The direct measurement of the soft soil/tyre contact parameters is a challenging task, addressed by expensive experimental campaigns and specific tools such as sensor-equipped wheels. In this paper an alternative cost-effective approach is proposed to estimate the contact parameters for semi-empirical formulations. The method relies on the experimental measurement typically available on the CAN bus of passenger vehicles. Specifically, the algorithm is tested with data gathered during acceleration manoeuvres performed on two different soft surfaces, i.e., snow and sand. The experimental signals are used to feed a 5 Degree Of Freedom (DOF) virtual vehicle equipped with a custom semi-empirical soil contact model. An optimisation problem with the target of minimising the differences between experimental and numerical traction performance is designed for the estimation of the sinkage module, cohesion, friction angle, elastic recovery and the multi-pass factor. Finally, the estimated parameters are validated using different experimental signals and data from literature, demonstrating the robustness of the methodology.