Combating the effect of chassis squat in vehicle performance calculations by accelerometer measurements

The performance of a vehicle is measured as the time to complete an assigned task while accelerating. Non-intrusive performance measurements are often based on inertial navigation, i.e. measurements from an accelerometer are integrated once to obtain an estimate of the speed of the vehicle. A second integration results in a measure of the traveled distance. However, the suspension system of the vehicle introduces error in the measurements, owing to the tendency of the chassis to rise in the front and drop in the back during acceleration. An approach is derived based on the method of weighted least-squares for estimating the misalignment angle as a function of the horizontal acceleration. The proposed method includes a parametric model describing the effect of the tilt of the vehicle on the accelerometer measurements. Further, the method employs an external reference. It is shown that for a particular parametric model, the problem at hand has a closed-form solution. Certain practical applications are studied in some detail. A relative error of 0.5% in the elapsed time and 5% in the final speed is illustrated on 201-m straight track races.