Development of inverted pendulum robot capable of climbing stairs using planetary wheel mechanism

Improved robot mobility is necessary in order to realize the expected uses of robots in the human life environment, which includes obstacles such as stairs and narrow passages. Because objects which humans require are often located on desks or tables, which are at some height above ground level, a long vertical dimension is also necessary in the robot design. To meet these requirements, this study focused on a type of mobile robot using an inverted pendulum, which enables a robot with a long vertical dimension to negotiate narrow passages. Since it is difficult for inverted pendulum robots to climb steps, this study proposes a planetary wheel mechanism which makes it possible for an inverted pendulum robot to ascend differences in level. This mechanism has an extremely simple structure, comprising a belt, pulley, and arm, and has the advantage of not requiring addition of a new actuator. This paper describes the composition of the proposed mechanism and its principle of operation, and also describes the control method. A prototype of the robot was produced, and it was shown experimentally that the robot was capable of climbing stairs with a height of 120 mm-130 mm at a rate of approximately 2.4 s per one step.