Instrumented bearing for force and moment measurements

A new low cost integration of force and moment measurements into a wheel bearing is proposed. Those data will enhance performances of existing driving assistance systems and enable emergence of new ones. The measurement principle stems from the dependancy between the contact forces transmitted by the balls and the force components to be measured. The deformations caused by the contact forces come from strain gauges installed on the outer ring of the bearing. We claim that the clear mechanical interpretation of the measurement principle makes it reliable and robust. Another aspect of the measurement principle stems from the periodicity of the deformations with respect to the angular positions of the balls; they can be represented as sums of harmonics. The study shows that the Fourier coefficients of gauge signals are functions of the force components to be measured. It is shown that the model obtained by keeping only a few harmonics is relevant to experimental data. Local inversibility of the system is discussed from sensibility and condition number considerations.