[Defense Column] Why the Humvee Can Run in Mountainous Areas

[Image source=Yonhap News]

[Asia Economy Yang Nak-gyu, Military Specialist Reporter]Unlike most civilian vehicles that drive on paved roads, military mobility equipment operates relatively more on unpaved roads or rough terrain. The durability of mobility equipment used in harsh environments such as battlefields is crucial, and the road surface is one of the factors affecting durability. To ensure the objectivity of durability testing, one important aspect is to verify and analyze the road surface roughness (severity) levels of the test ground’s durability test track and the military operational area’s mobility routes, and based on this, maintain consistent road surface roughness on the test track. At this time, the technology required to quantify road surface roughness on unpaved surfaces is the measurement and analysis of road surface roughness (profile).

▲ What is road surface profile data generation technology? First, to analyze the severity of the road surface, a device capable of effectively measuring and acquiring road surface roughness is needed. However, vehicle-type road surface roughness measuring equipment used in civilian sectors to check road damage is only applicable in a limited way on paved roads with low roughness. This is because when driving on roads with severe roughness, rapid changes in vehicle posture due to road surface roughness cause significant measurement errors. Therefore, it is difficult to apply measuring equipment on unpaved roads and rough terrain in forward areas where military mobility equipment operates. The Agency for Defense Development (ADD) has developed road surface roughness measuring equipment and an onboard road surface profile data generation program to effectively measure and analyze road surface roughness not only on paved roads but also on unpaved roads and rough terrain.

▲ How is the road surface profile data generation program operated? When the road surface roughness measuring equipment is driven on the road to be measured, the laser scanner and GPS-INS sensors mounted on the equipment measure the vertical distance between the vehicle and the road surface, as well as changes in the vehicle’s pitch (front-to-back tilt), roll (side-to-side tilt) caused by road surface roughness, and altitude. Then, using the road surface profile data generation program, the equipment generates a road surface profile, which is the vertical distance compensated for vehicle posture changes caused by road surface roughness. Since the measured vertical distance includes considerable measurement errors due to posture changes of the equipment caused by road surface roughness, it is essential to subtract these errors to obtain accurate vertical distance measurements.

Front view of a vehicle equipped with a road surface profile data generation device (Source: Agency for Defense Development)

▲ Trends and significance of road surface roughness measurement research and development Numerous road surface roughness measuring equipment and patents applicable to paved roads exist domestically and internationally, but off-road road surface roughness measuring equipment is known to be possessed by the U.S. YTC (Yuma Test Center), ATC (Aberdeen Test Center), and also by the ADD. By independently securing road surface roughness measuring equipment and analysis technology applicable to various types of road surfaces, the ADD has been able to obtain road surface data necessary for developing mobility weapons with driving durability suitable for Korea’s terrain and roads. Furthermore, this technology is expected to be applicable to MMS (Mobile Mapping System) vehicles used for precision map production in the civilian sector.

▲ The future of vehicle-type road surface roughness measuring equipment Vehicle-type road surface roughness measuring equipment has the drawback that when driving off-road, changes in vehicle posture caused by road surface roughness inevitably lead to measurement errors in vertical distance to the road surface. To reduce errors, the equipment must be driven at low speeds according to road roughness, and additional algorithms are required to compensate for vehicle posture changes caused by road roughness. Also, there are operational limitations due to the inherent limits when improving performance through compensation algorithms from data containing measurement errors. However, by combining widely used drones and photogrammetry, it is expected that measurement errors caused by road surface roughness can be fundamentally resolved. In particular, drones can fly with a stable posture unaffected by road surface roughness. Although there are drawbacks such as susceptibility to weather conditions, if devices and software capable of extracting road surface roughness (profile) information from continuously overlapping road surface photos taken by cameras mounted on drones are developed, it could complement the shortcomings of vehicle-type road surface roughness measuring equipment. The ADD is also making efforts to develop this technology.

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