Power Electronics

SiRF navigation software taps vehicle data bus for dead reckoning measurements

SiRFDRive2 GPS/dead reckoning software from SiRF Technology Holdings Inc. is said to reduce system costs by tapping the vehicle data bus as a source of distributed sensor information, thereby eliminating the cost of a dedicated automotive gyro.

The software requires only a single connection to the vehicle bus to supply the dead reckoning speed and heading measurements that telematics and navigation systems need to validate and correct GPS fixes during signal blockage and multipath interference, such as when traveling through tunnels or urban canyons.

SiRFDRive2 complements GPS satellite measurements with independent vehicle speed and anti-lock brake sensor inputs. The measurements are typically in the form of speed tick rates, angular wheel velocity or linear wheel velocity from the existing active or passive ABS sensors on at least two parallel wheels on the same axle.

The software is compatible with all SiRFstarII-based GPS receiver chip sets including the recently introduced SiRFstarIIA GPS system-on-chip. The software will continuously calibrate all the sensors using GPS data when the GPS position is available. When GPS signals are not available, the system will navigate in dead reckoning mode until the sensor calibration data no longer is valid, and if any of the sensors break or become unreliable, the system will notify the application and resort to GPS-only navigation.

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