Wheel type mobile robot which can travel over a step

We are developing a mobile robot platform which works in the actual indoor and outdoor environment. For this purpose, a six wheel vehicle which can travel over 18 cm single step, was developed and tested. The vehicle has six wheels and all wheels are driven using friction wheels. The back and forth wheels in both left and right sides are steered in the opposite phase. Since they can swing up and down by DC motors, the vehicle can travel over a 18 cm step. As one of main feature of this mechanism, bobbin-shaped friction wheels which transfer driving force from main driving wheels to steering wheels located front and rear of the body. This vehicle may be applied to wheel chair or base of mobile manipulator which has to work autonomously in the real indoor and outdoor environment.