An Untethered Tripodal Miniature Piezoelectric Robot with Strong Load Capacity Inspired by Land Motion of Seals

Wireless motion and large capacity are two important characteristics for practical applications of the miniature robots, and become more challenging as the decrease of the robot size. Here, we proposed a tripodal miniature piezoelectric robot (TMPR) with size of 31 × 44 × 20 mm³ and weight of 9.8 g. The prominent features were the square section piezo-leg arranged at a 45° angle and the supporting structure with a passive wheel. The former made the robot achieve bidirectional motions by only one signal; and the latter, inspired by land motion of seals, helped the robot increase the load capacity. Then, a small onboard power supply was developed, and the TMPR achieved wireless motions with maximum velocities of 146.0 mm/s (forward) and 93.1 mm/s (backward). In the wireless motion, the tested maximum load was 331.6 g, the load-to-weight ratio exceeded 33.8, and the cost of transport in the bidirectional motions were only 1.33 and 1.56, respectively; besides, the endurance time was more than 120 min powered by a 400 mAh battery. Moreover, the robot could operate in sloping or shaking pipelines, and collect information by equipping carrying a small camera, which exhibited much potential in application of small pipeline detection.