Everyone who makes or uses automobiles puts a high premium on active safety measures that can economically be deployed to intervene and so minimize or prevent injuries in a crash. Up until now, safety measures have been passive, or begin to be activated and come into play once a crash event is under way, that is at time T = zero plus some increment of time until deployment.
TRW’s innovation, designed and commercialized by TRW Automotive in Alfdorf, Germany, is to have come up with an innovative active safety measure that begins to work at T minus an increment, that is, to start to take effect before the actual crash event actually begins. This points the way to entirely new ways of thinking about active safety measures.
TRW’s Active Control Reactor (ACR) is a seat belt pretensioner that really is a pre-tensioner, that is, it begins working before the crash has begun. Reading data from a vehicle’s braking and stability control sensors, it reacts by snugging up the driver and passenger seatbelts, so the occupants are positioned correctly between seat-back bolsters in advance of an impending crash. In approximately two thirds of crashes, the actual event is preceded by hard braking, sliding, and skidding. Car occupants – even wearing seatbelts – are out of position a very large percentage of the time, and this can contribute materially to injuries directly, or indirectly, by rendering other restraints and safety measures less effective. The only events for which this device cannot make a contribution are ones from the rear or side, if they are totally unanticipated by the driver. For that reason, the ACR may be supplemented by more usual pyrotechnic “pretensioners, “which activate in a way that is similar to airbags, once the crash is initiated. The ACR has electrical activation, by contrast, which in turn activates electronic motors located at the bottom of the B pillars, reeling in three point belts. And unlike pyrotechnic activation devices, the ACR may be activated and automatically reset and activated again any number of times.
TRW’s ACR makes its first appearance as standard equipment in the European Mercedes-Benz S-Class for 2003. TRW has other signed contracts for ACR units, and competition is beginning to react to this innovation.