In most developed cities, pipeline maintenance poses one of the major critical issues faced by humans. The identification of the aging pipes, their replacement, it’s cost and time-consuming implications when constructed underground or placed in high buildings, contribute significantly to the challenges in pipeline maintenance. Although industrial cameras have been applied in such inaccessible narrow areas, there are still limitations in the use of these cameras in pipelines located at corners of buildings. Hence, there is a need for robotic in-pipe inspection that addresses these challenges in manual task collection.
Our developed robot is composed of only a single active compliant middle joint, two passive compliant joints, three drive wheels, and two roll wheels. The passage of the bend pipe is achieved only by the joint torque control, while the T-branch travel is achieved by controlling both joint angle and torque. Instead of using a torque sensor, a polyurethane-based series elastic actuator (SEA) is installed in the middle joint. Our developed robot can pass through 15 bend pipes or more and 10 types of T-branch with different gravity directions, and can generated the traction force of 25 kgf (approx. 250 N) and more. Experiments revealed that it can pass through a pipeline with an inner diameter of 4 in for approx. 30 m and more. Pipeline routes can be also drawn by attaching an additional sensing unit with a rotary encoder and IMU (Inertial Measurement Unit), which is towed by the self-propelled lead robot.