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Measuring braking distances

Genesys Elektronik (Germany) has introduced the GPS speed sensor ADMA-Speed with integrated inertial sensor-based technology. The unit is optimized for brake tests and supplies braking distance data in real-time via a CAN interface.

The speed and braking distance sensor with integrated inertial sensor-based technology is optimized for brake tests (Photo: Genesys)

ALL VEHICLE MOVEMENT DATA IS CALCULATED USING the ADMA technology (Automotive Dynamic Motion Analyzer). There are various ways to measure the braking distance: radar sensors, optical systems, electrical wheel impulses and GPS. However, further development of vehicle and brake technology places additional demands on the measurement accuracy, quality and repeatability of the results, plus the need for enhanced technologies.

At the heart of the introduced braking distance sensor is a GPS antenna with integrated inertial sensor-based technology. The standard GPS measuring method has the disadvantage of requiring a clear view of the sky to ensure accurate measuring results. In real life situations, the GPS signals and the achievable measurement accuracy are affected by buildings, trees, fences, and vehicles. These effects are further influenced by satellite constellations. Quite often repeatable measurement results are not possible. The inertial measuring unit suppresses signal interference during poor GPS reception or temporary GPS failure. The product compensates GPS data latency and corrects acceleration-dependent GPS signal distortion.

The speed and braking distance sensor with integrated inertial sensor-based technology is optimized for brake tests (Photo: Genesys)

The sensor takes pitching movements, which inevitably occur during the brake stop, into account. Signal inputs for a brake trigger or light barrier are integrated in the unit. In other words, a covered braking distance can be triggered via adjustable speed thresholds and via external signals using a physical switch on the brake pedal or a light barrier. Moreover, it allows determination of deviations from a straight calibration line when the brakes are applied. Yawing can therefore also be calculated. The simplest way to attach the speed sensor is with strong magnets to the vehicle roof directly above the center of gravity. The movement data of the vehicle at its center of gravity is calculated in the evaluation unit with so-called ADMA Kalman filter technology. The acceleration, speed, and braking distance data are output – in real-time – via the CAN interface.

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