DETROIT – While airbag systems have become highly sophisticated in recent years, experts agree there still is a weakness when it comes to side impacts.
Accelerometers do a good job sensing the severity of a front or rear collision – relaying information back to a satellite receiver, which in turn tells a microcontroller whether to fire the airbags – but for side collisions, “(they) typically don’t have the reaction time necessary for there to be a safe airbag deployment,” says Infineon Technologies’ field-applications engineer Roger Smith.
To remedy this, Infineon now is using a pressure sensor, usually placed in a vehicle’s door cavity, which has an ambient pressure while measuring constant pressure.
“It will do a calculation where it measures the current pressure divided by what the ambient pressure is and, based on that calculation, will either fire the airbags, or it won’t fire the airbags,” Smith says at the Convergence Transportation Electronics Conference here.
Infineon’s KP106 and KP200 sensors currently are in production for European applications, withAG as the Tier 1 supplying -brand vehicles. Also, Inc. is supplying the sensor for an unnamed U.S. vehicle program.
In lieu of a pressure sensor, Smith says some of Infineon’s customers are exploring placing an accelerometer on a vehicle’s A-pillar to better detect side impacts. “They’re trying to do some software work in order to get the cost out a little bit. But for right now, they’re pretty much using the door pressure sensor.”
Meanwhile, a feature that aims to cut costs from the airbag system is nearly ready to debut in a production model. Infineon is integrating power-supply functionality into a single Application Specific Integrated Circuit (ASIC), Smith says, which incorporates three different chips for each power supply.
“Inside one ASIC there will be our 30V voltage, our 9V voltage, plus the satellites for the different accelerometers around the outside of the vehicle,” he says. “They need a regulated voltage, as well.”
This type of integration is more suited for vehicles that have multiple side-curtain airbags, Smith notes, declining to reveal which auto maker will use the first application except to say it will be in a “high-end” model debuting in January.
Infineon also is developing its airbag system on a chip for that same customer, he says. “It will have the power supplies. It will have the satellite receivers. It will have the squib drivers (the device that fires the airbag), all on the same piece of silicon. The idea is to get smaller, cheaper, reduce weight (and) reduce package size.”
The customer now is trying to decide whether it wants to integrate the microcontroller into the same ASIC or chip, Smith says. “Right now it’s going to be a 2-stage process, where initially the micro will not necessarily be separate. And then, we’ll integrate the micro into the same ASIC or the same chip.”
From a cost-savings perspective with this type of integration, Smith says a customer would save $2 per unit “from the discreet solution to the integrated solution.”
The cost-savings is important because airbags have become commodities, he says, and “OEMs just say 'give this to us.’”