A Piezoelectric In-Pipe Robot Driven by Macrofiber Composite Films: Design, Modeling, and Experimental Verification

A piezoelectric in-pipe robot based on piezoelectric macrofiber composite (MFC) films is proposed, which solves the problems of large size, small load, and weak turning and climbing ability of centimeter-scale in-pipe robots. The proposed robot can realize a reciprocating motion along a curved pipe with a diameter of 14.6–20.5 mm based on the stick–slip principle. The working principle and gait characteristics of the proposed robot are analyzed. According to the structural characteristics of the proposed robot, its dynamics model is established, and its motion characteristics are simulated. Using a single MFC and two MFCs as driving elements, six sizes and specifications of in-pipe robots with a minimum weight of 3.89 g, a length of 50 mm, and basic diameters of 15, 18, and 20 mm were manufactured, respectively. By using a self-constructed experimental platform, the motion and load characteristics of the proposed in-pipe robot in horizontal, sloped, and bent pipes were tested. The results indicate that the maximum speed of the proposed in-pipe robot is 13.54 mm/s under a driving voltage of 1000 V, frequency of 210 Hz, and duty cycle of zero. The maximum working slope of the proposed robot is 90°, and the robot can realize turning at approximately 90° with a curvature radius of 25 mm. Moreover, the robot exhibits a load-carrying capacity of nine times (42 g) its self-weight. The proposed robot has the potential to be applied to exploring narrow areas of small pipes.