Design and Reactive Navigation of Propeller-Driven Miniature Swimming Robot for Pipeline Inspection

In-pipe swimming robots (ISRs) are essential for inspecting and maintaining urban water supply networks. However, existing ISRs often face limitations in maneuverability and environmental sensing due to size constraints, which reduces their efficiency and reliability when navigating complex or narrow pipelines. In this article, we develop a compact ISR with a diameter of 7.8 cm, a length of 12.9 cm, and a density similar to water for autonomous navigation through narrow pipelines. The ISR incorporates four propellers for maintaining attitude and depth, and two tail propellers for horizontal movement. It is equipped with a pressure sensor, an inertial measurement unit, and a camera to perceive depth, attitude, acceleration, and the pipeline environment. An onboard embedded computer manages estimation, mapping, and planning tasks. For stable yaw and depth control, a double-loop proportional–integral–derivative (PID) controller is implemented. To enable autonomous inspections despite limited perception, we propose a reactive navigation method that leverages visual landmarks (forks, T-turning, T-direct, L-turning, and Up/Down-turning) together with a preloaded topological map and path. The robot utilizes visual algorithms to determine its relative position within the pipeline and complete autonomous inspections in a custom-built pipeline. Experimental results demonstrate the effectiveness of the proposed algorithms and approaches.