Terrain Profiling

Regularly scheduled course profiling ensures repeatable test results on NATC courses. In this capacity, the DFMV is a cornerstone in NATC's accelerated life cycle testing program for ground-based vehicles.

The vertical elevation changes in the course are calculated at each wheel by determining what the course had to look like under the tire to cause the measured forces and accelerations at each wheel. Whereas the majority of profilometers use motion measurements to calculate the terrain profile, the DFMV uses force-motion measurements made at each wheel end to calculate the profile. From those measurements, the exact course, in terms of elevation versus distance and a wave number spectrum, can be determined. In this way it is possible to identify the deformable nature of the terrain and compare the severity of the terrain when it is wet or dry.

NATC uses the DFMV for measuring and monitoring test courses against established baselines. Given a vehicle mission scenario of paved, secondary and cross-country operation, NATC can scale course roughness and speed to generate an equivalent total life energy input to the vehicle. For example, 10,000 miles of highway operation can be equated to 1,000 miles of rough gravel operation at a set speed. The test vehicle sees an equivalent amount of road inputs in 1,000 miles as it would on 10,000 miles of highway. Other course profile-related uses of the DFMV are:

1. Comparing test course roughness between different durability test courses used around the country
2. Defining roughness tolerances on established courses
3. Specifying mission profiles of vehicles
4. Conducting fatigue RAM analysis
5. Providing terrain inputs for computer models
6. Vehicle dynamic studies