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ESP sensor packs digital SPI

Posted: 17 Sep 2009 ?? ?Print Version ?Bookmark and Share

Keywords:sensor? automotive? SPI?

Bosch Automotive Electronics has unveiled what it claims to be the first micromechanical inertial measurement unit for vehicle dynamics control in low-cost SOIC16w housing. The SMI540 opens up new development possibilities for the electronic stability program (ESP).

The 3D sensor simultaneously monitors three of a vehicle's movement axestwo acceleration or inclination axes (ax, ay), and one axis of rotation (Oz). Until now, at least two separate sensors were required for this. The SMI540 has a digital SPI with two standard protocols. Thanks to a constant internal self-test of the yaw-rate sensor element, Bosch said the interface meets the highest operating safety standards.

Two of SMI540's three sensor signals provide information that is relevant for the ESP system: the yaw rate and lateral acceleration. The remaining third sensor signal is not generally used by ESP. It measures a vehicle's acceleration or inclination in the direction of travel. Developers can use the information this sensor delivers for other applications, such as the hill hold function or for fuel-saving functions in cars with automatic transmissions (N control). The car automatically shifts into the fuel-saving "N" gear, provided thatand this is where the inclination sensor comes into playthe car is on level ground and cannot begin to move by itself.

The SMI540 serves conventional ESP concepts as with a separate sensor device in the vehicle interior as well as new, more cost-effective approaches. As an example, the Bosch ABplus airbag concept no longer contains the sensor device for ESP control. In this case, the inertial sensor is now integrated directly into the airbag control unit. These are ideal conditions for the SMI540, with its small SOIC16w housing (10.3mm x 10.3mm x 2.65mm) and multiaxial sensors.

The sensor is also suited to the alternative concept of a central domain control unit. This unit integrates several of a vehicle's sensor functions and forwards measurements for safety and comfort and well as driver information to the relevant on-board electronics.

Samples of the new sensor are available. The sensor is set to go into large-scale series production from Q2 10. Bosch also plans to launch the SMG540, a version of the sensor that contains only the yaw sensor element.

- Christoph Hammerschmidt
Automotive Design Europe

For application notes on sensors click here.

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