The PRECRASH SENSING system introduces the technology of surround sensing into the passenger protection systems field. The PRECRASH system comprises three functionalities: PRESET, PREFIRE and PREACT. The functionality PRESET activates the irreversible restraint systems on the basis of the acceleration signals and the information from the radar sensor system about the oncoming crash object. PREFIRE activates reversible restraint systems before the impact of the crash object. PREACT interacts with active systems of the car like the steering or braking system. Each of the three functionalities require their own range of view and specific situation analysis performance. For meeting the growing demands of passenger protection systems and for enabling the application of new restraint actuators, Bosch started the development of PRECRASH SENSING. The focus of this paper is on the PRESET and PREFIRE functionality for frontal PRECRASH SENSING. This paper presents results of this development. By means of the presented short range radar system (SRR) it is possible to determine closing velocity (cv), time to impact (tti), and offset which is the distance between the crash point and longitudinal axis of the car. The parameters cv and tti are used by an improved algorithm for PRESET, enabling the computation of more precise deployment times of restraint systems. All three parameters are used by the new algorithm for PREFIRE. The PRECRASH system enables the measurement and evaluation of crash relevant data in the time period before the impact. With this information it is possible to optimise the actions of reversible and irreversible restraint systems. For the covering abstract see ITRD E126782.
Abstract