Experimental methods to investigate the performance of the braking system using GPS and IMU equipment

Abstract

Establishing procedures and equipment for more accurate evaluation of the brake system performances is a major goal for automakers, but also for researchers, test equipment manufacturers, racing drivers and their staff, or for experts and forensics in their activity of accidents reconstruction. Increasing the performance and complexity of new vehicle stability control systems as well as driver assistance systems require finding new solutions for measuring and determining braking and stopping time and space, as well as a lot of new parameters such as braking system response, driver’s reaction times, actual value of the traction grip, corrections due to the slope of the road, or to the differences between the actual speed and the one displayed on board. Changes in adhesion and normal load on each wheel contact patch that occur under certain driving conditions develop lateral forces and yaw that disrupt longitudinal dynamics and must be determined and considered. The lack of braking marks in the case of partially braked or unlocked wheel by the ABS system is also a major impediment to the correct and accurate reconstitution of the braking and stopping space or speed. This paper describes a series of experimental research carried out by the authors using a professional GPS device, IMU, infrared thermal camera and a series of sensors that allow to determine with high precision the trajectory, radius of road curvature and tilt, the vehicle real speed, longitudinal and lateral accelerations, yaw speed or drift angle. Based on these determinations, several braking and acceleration parameters were estimated in alignment, in curves or in ramp and slope, respectively in coast down mode.