Snake-like active wheel robot ACM-R4.1 with joint torque sensor and limiter

In order to inspect inside narrow and unstructured environments, the snake-like robots should have ruggedness of the structure and at the same time function to detect the contact of the body to the environments. This paper proposes a snake-like active wheel robot named ??ACM-R4.1?? with torque sensor and torque limiter on each of the joints. Introduced torque sensor is composed of 2 thin ring plates holding steel balls in the oval cavities in between and a rubber ring producing compressing force of the thin ring plates in the narrow gap of a joint. Applied torque of the joint produces small sliding motion of the ball inside oval cavities and thus measurement of the small displacement of these plates enable to detect the applied torque. Overload-protection to the joint actuator is made by the sliding motion of the rubber which acts after the ball motion in the cavities and they hit the end of cavities. We made theoretical consideration of design of the torque sensor and did torque measurement experiments by using constructed snake-like active wheel robot ACM-R4.1. We also demonstrated the terrain adaptive motion of ACM-R4.1 by using the torque sensors.