LEVO: Mobile Robotic Platform Using Wheel-Mode Switching Primitives

This paper proposes a mobile robotic platform, LEVO, which uses a normal wheel and a curved-spoke tri-wheel (CSTW). The normal wheel is used for driving on flat terrain, and the CSTW is used for stair climbing. In order to use the two mechanisms independently, a switching mechanism that consists of ball screw, linear motion guide, and actuator is added. Therefore, the proposed robot can be driven in both wheel mode and CSTW mode. The CSTW mode is implemented by lowering the CSTW to the ground and raising the rear wheels (caster), while the wheel mode is implemented by lowering caster to the ground and raising the CSTW. In order to design the switching mechanism and CSTW mechanism, static and kinematic analyses are performed. Further, a prototype is assembled to verify the mode-switching, stair climbing, and wheel-driving functions. The experiment was repeated on stairs with different sizes and materials. The results show that robots can drive on both flat terrain and stairs. Therefore, the proposed robot is expected to be useful as a mobile robot platform suitable for indoor environments.