| Toyota has developed a cable-actuated
active headrest to mitigate whiplash injuries.
The OEM will use an intelligent radar-based system in Lexus vehicles.
Anti-whiplash systems reduce the stress on the neck during low-speed rear
impacts. Actuation of the system is a key issue as engineers must balance
cost with response time.
Toyota’s system comprises two units built into the seat. The lower
unit recognises when the occupant’s lower back presses against the
seatback in a rear-end crash.
This is linked by cable to the upper unit, which activates the head restraint.
The headrest then moves 30mm upward and 25mm forward to cushion the back
of the head.
“The results will differ according to the physique, position and
posture of the occupant,” said Toyota. “The system will be
introduced on a forthcoming model.”
In-house testing suggests the system reduces the severity of whiplash
injuries by 10 to 20 per cent. Toyota used its own neck injury evaluation
index, comparing the system with a traditional anti-whiplash seat.
The latest Lexus model, the LS 600h, has a more costly rear pre-crash
system. A 76GHz millimetre-wave radar in the rear bumper scans the area
around the back of the vehicle. If a collision looks unavoidable, the
system activates the front-seat headrests. These move forward by up to
60mm and upward a maximum of 25mm to cushion the occupant’s head.
The headrest contains an electrostatic capacity sensor to determine the
distance between itself and the occupant’s head, automatically stopping
before substantial contact with the head is made.
Tier-one supplier Grammer uses an electromagnetic actuator to release
pre-stressed springs that simultaneously pivot the headrest while pushing
it forward. Autoliv uses
gas-generator cartridges for deployment.
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