1. Field of the Invention
This invention relates to vehicle and, in particular, to a vehicle having an articulated suspension and a method of using the vehicle.
2. Description of the Related Art
Technological advances continually permit engineers and scientists to expand the arenas into which automated or robotic techniques can be applied. Speed, efficiency, cost, and safety frequently drive the adoption and/or application of these techniques. However, several factors retard the application of robotic technologies to vehicles, and especially to land vehicles. For instance, vehicles are designed to travel. This functionality raises a host of challenging issues such as obstacle avoidance, both in recognizing and overcoming the obstacles. Even relatively mundane types of vehicles face these challenges, but many subclasses of vehicles face challenges over and above obstacle avoidance. Consider, for instance, robotic vehicles for military application. Such robotic vehicles ideally should be easy in deployment, versatile in deployment, relatively self-sufficient for long periods of time, and be able to survive in hostile conditions.
As mentioned above, land vehicles often encounter obstacles in their path. For example, a car, traveling down a road, may encounter debris extending across the road. The car may have little trouble traveling across the debris if it is small, such as a small tree limb. However, if the debris is large, such as a tree trunk, the car may have difficulty traveling across the debris.
As shown in FIG. 1, a vehicle having a wheel 102 of radius R rolling along a surface 104 may generally traverse an obstacle 106 having a height X no greater than about the radius R of the wheel 102. Obstacles having heights X greater than the radius R of the wheel 102 will typically block progress of the vehicle beyond the obstacle. While this limitation may present few problems on paved roads, many vehicles are used in off-road environments, both here on Earth and on other planets, where the terrain may present many larger obstacles.
One approach to overcome this problem has been to use a “rocker-bogie” suspension in vehicles that may encounter large obstacles. Generally, rocker-bogie suspensions are passive mechanisms that include two rocker arms connected to the vehicle chassis. Each rocker has a rear wheel connected to one end and a secondary rocker, called a bogie, connected to the other. At each end of the bogie is a drive wheel and the bogie is connected to the rocker with a free pivoting joint. The rockers are connected to the vehicle chassis with a differential so that the pitch angle of the chassis is the average of the pitch angles of the rockers. Typically, vehicles utilizing rocker-bogie suspensions may traverse obstacles having heights of less than about two times the wheel radius (i.e., the wheel radius R of FIG. 1). Thus, obstacles may be encountered that such vehicles still cannot traverse.
Land vehicles and, in particular, military land vehicles, also face other challenges, such as turning in tight quarters, quickly braking to a stop, evading identification by hostile forces, and avoiding rollover while traversing rugged and/or steep terrain.
The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.