Experimental and computational assessment of stability in braking force measurements on a test bench with horizontally rotating support discs

Abstract

Introduction.  The stability of vehicle braking force measurements is investigated on a power-type test bench equipped with a horizontally rotating disk under each test wheel, which ensures a tire-to-surface contact patch shape close to real road conditions. The factors controlled in the experiment include the wheel positioning radius on the support disk and the force applied to the brake pedal, while the response function is the braking force measured by the test bench. Materials and Methods.  A mathematical experimental design was used for a full-scale testing of a passenger car braking system on a custom-built test bench. This aimed to obtain static (regression) models linking the realized braking force to braking process parameters, such as brake pedal force and braking leverage. Correlation and regression analysis tools in Microsoft Excel were used to process the experimental data. Results.  The type, structure, and order of the static (regression) model linking the realized braking force to the braking process parameters (brake pedal force and braking leverage) have been determined. А model was obtained in the form of a nonlinear regression equation linking the factors to the response function. It was found that the maximum peak instability in braking force measurements (the maximum discrepancy between experimental and calculated values) for the test bench with horizontally rotating support discs does not exceed 5%. This is quite acceptable for practical application, in particular, for vehicle brake testing during operation. Discussion and Conclusion.  The obtained static model in the form of a nonlinear regression equation can be integrated into the test bench algorithm to control the accuracy of braking force measurements for in-service passenger cars during routine maintenance, periodic technical inspections, etc. The obtained statistical characteristics of the regression equation can be used to justify the metrological characteristics of the test bench for its type approval.