Why GNSS?

Why GNSS?

Conventional AEB testing systems tend to use a scheme that positions several pairs of light barriers across the path of a test vehicle. As the vehicle moves forward, its distance from the end target, the dummy’s path, can be tracked. Once the vehicle is at the right distance, the dummy can be made to move out into the vehicle’s path, allowing observers to record and assess how the vehicle’s AEB system reacts.

“With light barriers, we can even adjust the speed of the dummy based on variations in the speed of the vehicle,” says Fritz, “by recording the delay as the vehicle crosses the barriers. Of course, the accuracy of our corrections depends on the number of barriers and the distance between them.”

Increasing the number of light barriers provides greater accuracy for such systems, but more barriers also mean greater expense, in terms of materiel and set-up time. “What’s more,” says Fritz, “with a light barrier system, adjusting the path of the dummy in relation to possible sideways displacement of the nearing vehicle is impossible.”Safety 1

So, the main benefit of using GNSS instead of the light barriers is that the team can determine the precise distance and the sideways displacement of the approaching vehicle, continuously, in real time.

“We have the ability to trigger the dummy movement in exact relation to vehicle speed, vehicle distance, and vehicle side displacement,” Fritz says. With continuous GNSS data from the vehicle, we can control the dummy movement for an optimal and precise crash point with only a few centimetres deviation.”

The company’s mobile test rig 4activeSB is small in size and easily transported by a passenger vehicle, Fritz says. Two people can set it up in just about half an hour with no need to fix it to the ground. The system is battery powered, with a minimum operating time of 10 hours at low temperatures.

The GNSS arrangement consists of a moving base station mounted on the vehicle roof and a stationary rover at the system drive unit. Each has a NovAtel Smart6–L antenna, generating ready-to-use, precise, Real Time Kinematic (RTK) differential data that includes distance and angle between the two antennas, which communicate through a wireless serial data link.

“Our system gives us high positioning accuracy,” Fritz says. “It is fast and easy to use, it does not interfere in any way with on-vehicle AEB sensors, and it is waterproof and wind-stable.”