Evaluation of the wheel slip control quality during braking with the ABS system acting

The paper presents the method of assessing the degree of the wheel slip utilization during braking in relation to the slip adopted as optimal in the analyzed braking process. In an ideal ABS system, the wheel slip should be equal to the slip assumed to be optimal under the given braking conditions. In a real, pulsed system ABS, wheel slip changes in a wide range of values. The quantitative assessment of the correct operation of the real ABS/ESP system can be made on the basis of indicators showing the degree of approximation of the actual slip of the wheel s to the value assumed to be optimal due to the wheel's adhesion to the roadway s(opt). In the paper has been analyzed the wheel slip utilization Delta L, as the difference of the actual circumferential speed of the wheel v(kopt), and the speed of the wheel v at which the slip is optimal in the given braking conditions, referenced to a specific braking time Delta t = t(2)-t(1). The calculation of this indicator requires the measurement of the car's speed v(s) and wheel speed v(k) and the determination of the optimal slip value s(opt) on a given surface. The paper analyzes the impact of the optimal slip value on the assessment of ABS performance with various control algorithms (Independent Regulation IR, Select Low SL). The article presents the results of tests of the slip utilization index in various braking conditions and for brakes with damaged mechanical components.