New Regressors for the Direct Identification of Tire-Deformation in Road Vehicles via “in-Tire” Accelerometers

The interaction between the tire and the road is crucial for determining the dynamic behavior of a road vehicle, and the road–tire contact forces are key variables in the design of traction, braking, and stability control systems. Traditionally, road–tire contact forces are indirectly estimated from vehicle-dynamics measurements (chassis accelerations, yaw-roll rates, suspension deflections, etc.). The emerging of the “smart-tire” concept (tire with embedded sensors and digital-computing capability) has made possible, in principle, a more direct estimation of contact forces. In this field—still in its infancy—the main open problems are the choice of the sensor(s) and the choice of the regressor(s) to be used for force estimation. The objective of this work is to present a new sensor–regressor choice, and to provide some preliminary experimental results, which confirm the validity of this choice. The idea is to use a wheel encoder and an accelerometer mounted directly in the tire. The measurement of the in-tire acceleration is transmitted through a wireless channel. The key innovative concept is to use the phase shift between the wheel encoder and the pulse-like signals provided by the accelerometer as the main regressor for force estimation.