In this paper, the authors described a method of increasing traction force by a small number of pneumatic actuators of a wave propagation type pipe inspection robot with a series antagonistic mechanism. The pipes used for fluid transportation in the factory have a long distance. They have the small inner diameter and multiple bends to be installed small space. Therefore, it is difficult to evaluate the overall cleanliness in long-distance, complex and small inner diameter pipes with the endoscopy due to friction between the side surface of the endoscope and the inner wall of the pipe. In this study, we proposed a method for inspecting the pipes in a factory by a wave propagation type pipe inspection robot (PI-Ro) with a linear antagonistic mechanism that actively outputs pushing force and traction force. However, the simple application of PI-Ro is expected to reduce the inspection speed in complex and thin pipes with long-distance in factories. In this paper, we proposed a mechanism to increase the traction force by synthesis of the linear antagonistic mechanisms while minimizing the increase in the number of drive units. This mechanism increased the theoretical traction force by 1.88 times and realized the inspecting of the factory piping mockup.
