Development of a Steep Slope Mobile Robot with Propulsion Adhesion

A mobile robot that can achieve a stable attitude and locomotion on steep slopes is needed to overcome the problems of slipping and falling for automation of works on steep slopes. The conventional approaches to achieve a stable attitude and locomotion have been researched by adopting tracked wheels and multi-legged mechanisms instead of wheel mechanisms. However, these robots have limitations in term of application angles. A systematic theory for stable attitude and locomotion on steep slopes has not been established. Therefore, research on control strategies for wheeled mobile robots on steep slopes is essential. In this paper, a method to realize a stable attitude and locomotion on a steep slope for the wheeled mobile robot by using propellers for propulsion adhesion is proposed. The proposed robot can generate a large frictional force by pushing its body against the slope with a thrust force. This force prevents the robot from slipping while maneuvering on the slope. The magnitude and the direction of the thrust force is optimized using an appropriate control mechanism influencing the moment of force acting on it to avoid falling and side slipping during locomotion on steep slopes. A simulation experiment was conducted from the perspective of mechanics and dynamics to arrive at an optimal design of the mobile robot. The developed robot has four propellers to generate thrust forces and a rotation axis to control the direction of the generated thrust forces. Evaluation experiments were performed to validate the stability of the robot at a resting position and during lateral locomotion and its ability to climb over a slope. The experimental results confirmed that the proposed robot with propellers realized a steady attitude and locomotion on a slope of up to 90° by controlling the magnitude and the direction of the thrust force.