Development of Off-road Vehicle with 4 Rotating Crawlers Driven Independently

1. 我们设计并开发了一种液压动力原型车，以克服崎岖的地形或障碍。车辆有四组小型履带作为运行装置，履带移动的同时，履带外壳自行旋转运行，每个外壳轴连接两组前后差动齿轮。该原型车具有以下优点：1)四组履带无论地形高低不平，都能始终与地形保持接触；2)两组差速齿轮只要左右地势相同，就能在没有车辆滚动运动的情况下正常工作(如：(3)可以简化保持车辆底盘水平的控制系统。然而，由于左右履带之间的地面接触载荷不同，车辆在一定的地形上容易产生滚动运动。为了避免滚动，四个轴承座轴中至少有一个应按照地形的形状进行控制。讨论并设计了一些特殊的履带形状，以避免车辆的滚动运动。与传统形状的履带相比，使用这些履带可以将左右履带的地面接触力差减小到2/3-1/2左右。我们设计并研制了一种装有四套带轮胎的行驶装置的模型车，其壳体轴由两个线性轴承构成，使左右壳体轴所受的力矩保持一致。该装置的两个壳体轴与一组差速齿轮相连，轮胎的地面接触力相等，因为壳体轴处的力矩相同。各种地形形状的台架试验显示了理想的性能，尽管至少一个外壳应如上所述控制。

1. We designed and developed a hydrawlic powered prototype vehicle to overcome rough terrains or obstacles. The vehicle has four sets of small type crawler as running device, whose housing rotates by itself at the same time the crawler moves for running, and each housing shafts are connected to two sets of front and rear differential gear. The prototype showed many benefits such as : 1)the whole four sets of crawler can always stay in touch with terrain regardless of its bumpy figure, 2) the two sets of differential gear can work normally without having rolling motion of the vehicle as long as the level of the terrain is the same between right and left side (eg. overriding on the ditch or hedge), 3) the control system to keep maintaining the vehicle chassis horizontal can be simplified. However, the vehicle tend to induce its rolling motion on certain figure of the terrain because the ground contact loads between the right and left crawlers, in general, are different. To avoid rolling, at least one housing shaft out of four should be controlled in accordance with figure of the terrain.2. Some particular crawler's shapes were discussed and designed to avoid the rolling motion of vehicle. By using these crawlers, the difference of the ground contact forces between the right and left crawlers can be decreased to about 2/3-1/2 compared with the traditional shape of crawler.3. We designed and developed a model vehicle equipped with four sets of running device with a tire, whose housing shaft was constituted with two linear bearings so that the moment exerted to the right and left housing shafts stayd the same. Two housing shafts of the device were connected to a set of differential gears, and the ground contact forces of the tires became equal, being the fact that the moments at the housing shafts were the same. A bench test with various terrain shape showed desired performance, although at least one of the housing should be controlled as above.