Cars that can drive on roads with rough roads or in areas without roads such as wilderness, mountainous areas, slopes, swamps, deserts, and snow (Figure 1). ATVs are used in military transportation, military operations, surveying, mining, engineering construction, and forestry transportation.
There are two types of off-road vehicles: one is a series of ordinary freight cars, the structure is similar to that of ordinary freight cars, with 2 to 4 drive axles, and has some off-road ability; the other is a specially designed vehicle. The specially designed models are divided into two categories: one is a bicycle type and the other is an articulated type.
There are two- and multi-axle bikes, and some are equipped with unconventional wheels, such as flex wheels, compound wheels, and bladder tires. The articulated type has two-section, two-axis, two-section, multi-axis, and multi-section, multi-axis forms (Figure 2). Specially designed models have strong off-road capability and can be adapted for special purposes.
The United States and the Federal Republic of Germany designed a separate series of off-road vehicles for military use to emphasize their military requirements. Some off-road vehicles have an off-road load of up to 15 tons and can drive on the ground with pressure as low as about 10,000 Pa. The wheels of off-road vehicles are all-wheel drive.
PerformanceAmong the various automobile performances, the most important for off-road vehicles are trafficability, maneuverability and economy.
Walkability: Generally refers to the ability to traverse complex terrain (steep slopes, ditches, bushes, and other obstacles) and soft terrain at a certain average speed under rated load. The ability to traverse complex terrain is called geometric traversability.
The ways to improve this passability are: use a higher power engine; strengthen the structure to withstand the additional load caused by bumps or impacts; change the shape of the vehicle, such as using more than three axles The wheel type of multi-axle, articulated and star, etc., makes it easier for vehicles to pass obstacles; use large diameter tires to increase ground clearance; use independent suspension at all wheels to improve the grip of the wheels to the ground.
The ability to traverse soft ground (the tires are easy to sink) is called ground passability. The primary method of improving roadability is to use large diameter tires, wide section tires, or bladder tires to increase tire contact area and reduce ground contact Pressure and lower tire pressure to reduce buckling.
Some vehicles use a central tire inflation system, so that the tire pressure can be reduced from 500 to 600 kPa to less than 100 kPa at any time when the vehicle is driving, so that you can take performance into account of driving on hard terrain and soft ground.
Mobility: Civilian off-road vehicles must primarily have a certain degree of passability, while military off-road vehicles must have a broader meaning of mobility, that is, strategic mobility of tactical mobility.
The meaning of tactical mobility is close to traversability. Strategic mobility refers to the convenience of automotive logistics supplies (fuel, grease, parts, maintenance equipment and technology, etc.), ease of maintenance, and convenience of off-road vehicle transportation. vehicles. For example, cars must be able to fit into different aircraft cabins or cabins, be fastened securely and quickly, and be convenient for airdrops.
Economic efficiency: The higher and higher requirements for the passage and mobility of off-road vehicles have made the types and structures of off-road vehicles more and more diversified and complicated, and the cost has also increased and is not conducive for standardization. , an economical off-road vehicle has been proposed. The use of systems engineering and value engineering methods to assess the performance of ATVs and the cost of obtaining that performance to obtain the optimal design is a topic of research for ATVs.