This paper presents a wheeled V-shaped in-pipe robot in which the two outputs of the wheel shaft and roll joint are driven solely by a single actuator input. This underactuation is generated by a simple miter gear mechanism. Generally, to control two movements easily, one of the outputs of the underactuated mechanism is constrained by the resilience force of springs or by the friction force. However, this complicates the control of each output. In this study, a one-way clutch is installed to completely constrain one of the outputs (wheel movement). By using this clutch, the proposed mechanism enables a hemispherical wheel to switch between pitch and roll rotations by selecting the drive direction of a single motor. The one-way clutch constrains the wheels to rotate in only one direction. To take advantage of this constraint, the robot changes its direction of movement between forward and backward by using the rolling movement of the robot. After describing the configuration of the proposed robot and a roll-angle model of the robot, experiments are conducted in straight pipes, bending pipes, and an out-of-plane double elbow.

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.