Stopper Angle Design for a Multi-link Articulated Wheeled In-pipe Robot with Underactuated Twisting Joints

摘要

In this paper, we present a multi-link articulated wheeled in-pipe robot that can drive the wheel and roll joint by using only a single actuator installed in each link. The proposed mechanism enables the robot to move forward or backward and helically in pipes owing to rotation of the drive wheel and twisting of the body. These two movements are generated by a miter-geared differential mechanism installed in each joint, and the magnitudes of these movements depend on the load applied to the wheels and roll joints. However, controlling of two outputs independently and aligning the rotation of the roll joints as desired are extremely challenging. Therefore, in this study, we switch those two movements by driving the rear wheels and the front wheels of the robot alternately. In addition, a stopper is used to constrain the roll joint movement. By calculating the angle of elevation of the robot's helical movement in the pipe by using a kinematic model, we can design a stopper to precisely adjust the roll angle. We verified that the robot can twist using the differential mechanism, and we validated experimentally the effectiveness of the stopper.