If only drivers were as attentive as sensor automation: the ever-moving intersection of needs and technologies has greatly increased the number of sensors in today's cars. Here are some of the latest sensor systems in cars today and in development for the future

Automotive Design & Production, June, 2005 by Lawrence S. Gould

Several sensor technologies can solve the relatively simple problem of determining the size of the occupant: measure weight (just like a bathroom scale), recognize a pattern (the occupant's posterior on a seat cushion), or measure pressure (ditto). Tracking the occupant's position, a more difficult problem, seems to cry out for video sensing. Also, video sensing leads to other applications. For example, a camera could detect driver drowsiness, says Marc Bolitho, chief engineer, sensor engineering, for TRW Automotive's braking and steering systems. A camera could also detect a child abandoned in the back seat. When necessary, such a child detection system could roll back a sunroof or roll down a window, saving the child from asphyxiation or heat stroke. The system could also call a cell phone.

AIRBAC DEPLOYMENT

Much attention has been given to airbag deployment. TRW Automotive promotes using two acceleration sensors for both longitudinal and lateral direction sensing. These detect crashes as well as discriminate between any rough-road and misuse conditions, explains Suh. On the horizon are pressure sensors mounted in vehicle door cavities, thereby improving side impact detection, such as when a vehicle slides into a pole. Acceleration-based sensors mounted in the door pillar could work, but a pole might not squarely hit the door pillar.

Another approach to the same problem uses capacitive film sensors, such as that from Sensor Products LLC (East Hanover, NJ; www.sensorprod.com). These sensors are a sandwich consisting of two polyolefin layers and air in between. Changes in the 70-micron thickness of the sensor from an outside force generates a corresponding voltage. The solid-state, low-mass sensor is well-suited to sensitive and low-pressure applications, explains Carlos Ruiz, Tactilus product manager for Sensor Products. "If you stand on the sensor, it'll detect your heart beat."

VEHICLE STABILITY AND SEAT BELT CONTROL

Recently, General Motors announced that all of its cars and trucks will have vehicle stability control (VSC) by the end of the decade. VSC systems help prevent over- and under-steering. The sensors for this application divide into two categories, explains Bolitho: One measures driver intent; the other, vehicle dynamics.

[ILLUSTRATION OMITTED]

The VSC output has several spin-off applications. For example, TRW Automotive is applying the VSC signal to what it calls the active control retractor (ACR). "It's a fancy name for motorized seat belt," comments David Williamson, director of TRW's Electronic Control Systems Engineering. ACR takes the slack out of a seat belt, thereby putting the passenger in the ideal position for airbag deployment if the car's VSC and "brake assist" systems detect a potential crash or a loss in vehicle control. Today, such seat belt systems would use pyrotechnics. The problem with this is, after the pyrotechnics, after the seat belt is tightened, only the dealer can replace the seat belt system. The motorized system obviates that problem.