(1997-2000) Currently, there is a great demand for the development of a platform for rough terrain vehicles that can ascend and descend artificial obstacles such as the stairs in a home, and travel over rough terrain at high speed with good efficiency. In the future, this platform will be applied to a powered wheelchair for the disabled and the elderly, a carrier vehicle to assist workers in carrying heavy loads, and a hazard maintenance robot. Here to fore, many kinds of off-road vehicles and machines for these requirements have been developed all over the world. However, these vehicles had some serious problems, as follows: (1) The vehicle speed is extremely slow on not only rough terrain, but also on flat ground. (2) The mobile mechanism is complex. (3) High output torque is needed to negotiate obstacles. In order to overcome these serious problems, we have been developing the "HELIOS-V", 6 wheeled off-road vehicle.

HELIOS-V is shown in Fig.1. And the specifications are shown in Table 1. It has the following features: (1) It is equipped with 4 low-pressure tires, of which the surface rubber has some cuts, on the outside and 2 high-pressure tires on the inside. We call these low-pressure tires “Slitted Tire”. The Slitted Tire shown in Photo.1 exerts higher grip forces on the edges of obstacles than does a normal low-pressure tire in the same size. And these tires are connected by active links with prismatic screw mechanism. It can change the positions of the 6 tires to adjust to the terrain condition as shown in Fig.2. It can realize efficient locomotion on flat and/or irregular ground. By lifting the outer tires and supporting most of the weight with the middle tires, the turning resistance is reduced on flat ground. (2) It is equipped with a single main motor and two continuously variable transmissions. These transmissions have a capability to control the reduction ratio actively in order to control the rotation speed of right and left tires independently. And this power is transmitted from the middle tire to the front and rear tires through rims with gears. And the 3 tires in one side were driven by the gear train at the same speed. By using this mechanism, the driving system can easily change the velocity and the steering direction in narrow spaces.

Therefore, the drive train mechanism is compact, simple and lightweight. HELIOS-V has demonstrated the ability to ascend and descend stairs as shown in Photo.2, and to climb a high step as shown in Photo.3.