Analysis of ABS/ESP Control Logics Using a HIL Test Bench

Electronic Stability Program (ESP) and Antilock Braking System (ABS) are nowadays a standard equipment for passenger cars. ESP increases vehicle safety by applying differential braking torque to the wheels while cornering, thus it extends the area of intervention of ABS which prevents the wheels from being locked up in emergency braking, especially on low friction road surfaces, allowing the driver to maintain steering control of the vehicle, to avoid obstacles and to reduce vehicle stopping distance on most road surfaces. This paper describes a flexible mechatronic test bench for ESP/ABS Electronic Control Unit (ECU) based on Hardware-In-the-Loop (HIL) simulation technique. It consists of a passenger car hydraulic braking system (from master cylinder to brake calipers), with the ESP/ABS ECU integrated and a flexible real-time platform, which simulates vehicle dynamics. A fourteen degrees of freedom optimized vehicle model has been developed in order to reproduce with sufficient accuracy the vehicle dynamics. Wheels angular velocity, steer angle, lateral/longitudinal acceleration, yaw rate are provided to ABS/ESP ECU using both direct and CAN connection. At this stage of the research, the developed HIL test bench has been used to evaluate the control algorithms of a commercial ESP/ABS system in different emergency maneuvers. Although widely documented in the literature, the algorithms implemented on commercial ECUs are in fact only qualitatively described (due to industrial privacy reasons) and some critical points are only partially addressed (friction coefficient estimation, activation/deactivation algorithms, etc.). Several maneuvers (panic braking, step-steer, etc.) on different adherence surfaces have thus been simulated to gain a better understanding of the control strategies and to estimate the controller parameters