Estimation of brake pressure and tyre-road friction during ABS activation

Anti-lock Braking System (ABS) control algorithm and diagnostic function rely heavily on information of road friction coefficients and brake cylinder pressure. To provide a more efficient and reliable means of friction and pressure estimation, an algorithm based on wheel speed signals and control commands for hydraulic valve operation is proposed. Estimated results are achieved by comparing the sums of squared speed errors between the measured wheel speeds and those based on a brake pressure model and wheel dynamics. Performance of the algorithm is evaluated using ABS test data under various braking conditions.