Bistable Inflatable Fabric Actuators to Amplify Force and Energy Output for In-Pipe Soft Robots

Pipe inspection robots present a novel and efficient approach for detecting leaks or cracks, especially in environments that are harmful or inaccessible to humans. Compared to conventional rigid designs, pneumatic soft robots have emerged as promising alternatives thanks to their low cost, lightweight, mechanical compliance, and ease of waterproofing. However, they usually suffer from low power output limited by the materials and fabrication methods. In this article, we propose a new class of bistable inflatable fabric actuators (BIFA), which leverage bistable structures to modulate the available pneumatic power for short-term high-power motions. A simplified yet accurate model was developed to understand the trade-offs between the speed and power output and guide the design of BIFAs and the in-pipe inspection robot. By incorporating strong bistability, the actuator achieves almost three times the impact force and five times the energy output compared to a weakly bistable variant with the same dimension and weight. Experiments demonstrate that the in-pipe robot built can traverse with an inchworm locomotion pattern in 4-in and 6-in pipes. The robot weighs only 284 g and has a top speed of 21 mm/s. We also demonstrate the benefits of high-power motions in breaking and pushing away obstacles in pipes.