TRW Automotive Holdings Corp. has developed two new integrated systems, one that combines its electrically powered steering (EPS) and electronic stability control (ESC) systems and another that links TRW’s adaptive cruise control (ACC) with its active control retractor (ACR) seatbelt technology to help prepare occupants before a crash occurs.
The firm said the integrated braking and steering system can deliver better driver support and comfort, as well as better braking performance on split mu surfaces (e.g., two wheels on ice and two on pavement).
Alois Seewald, global engineering director of TRW Automotive's systems integration team, said stteering torque control (STC) can help correct situations such as oversteering in hard cornering or rapid lane change maneuvers. The function is enabled without the need for additional sensors by the integration of TRW's EPS and ESC systems plus integration algorithms for applying steering torque in oversteer and split mu braking conditions.
In an oversteer situation the EPS system generates a steering torque that “coaches” the driver toward the required steering angle correction. During a split mu braking situation the braking and steering systems work together to maximize the vehicle stability and driver confidence while the vehicle stops. The EPS system generates steering torque to encourage the driver to countersteer and respond to vehicle yaw in a controlled fashion. Higher braking pressures can be initiated on the high mu side, potentially reducing stopping distance.
Seewald said the system achieves an improvement of around 8% in split mu braking performance at 80 km/hour, or the equivalent of the average length of a vehicle. Other STC benefits include side wind compensation, trailer stability control, and pull drift compensation to offset road camber. The function can be achieved through EPS software enhancements or with an additional module for hydraulic steering systems.
TRW is also combining its ACR seatbelt system with its second-generation AC20 radar system, which can identify target vehicles at up to 200 meters and gauge how rapidly the acquiring vehicle is approaching them. If the gap between the vehicles is closing too quickly, the AC20 will signal the ACR system to remove any seatbelt slack, which helps to better position the occupant for a potential crash and helps to warn the driver of a potential impending event. If the crash is avoided, the system will reverse itself and automatically loosen the seat belt slack.The pre-crash system uses a situation management algorithm that continuously processes signals from relevant dynamic systems such as ABS, ESC or ACC radar. The algorithm evaluates events such as braking, sliding, vehicle angle and object detection and determines if a critical situation has been reached that warrants the activation of the ACR system.