Research on variable posture driven inner pipeline robot and its pipeline passability

Abstract

To address the limitations of existing inner pipeline robots, such as limited pipe diameter adaptability and insufficient flexibility, this study presents a novel inner pipeline robot with self-adaptive diameter adjustment and variable-posture drive capability. The diameter-adjustment mechanism combines compression springs and a bidirectional ball screw pair to achieve active-passive composite diameter adjustment, while the variable-posture drive mechanism achieves switching between multiple motion modes through coordinated control of the main drive motor and digital servo, thereby accomplishing obstacle crossing. A geometric model of the robot was established, yielding an adaptable pipe diameter range of approximately 373–450 mm. The robot can traverse internal pipeline obstacles with a maximum height of 157.8 mm and a maximum width of 300.2 mm. A force analysis of the robot during climbing motion inside the pipe was conducted, determining the maximum required minimum wall-pressing force for the robot to climb in pipes inclined from 0° to 90° to be 88.04 N. Further force analysis on the diameter-adjustment mechanism was conducted, determining a minimum spring preload of approximately 25 N for stable robot operation. Based on this, the robot’s pipeline passability was simulated in ADAMS and subsequently validated via experiments on a physical prototype. The results demonstrate that the robot achieved a maximum velocity of 7.84 m/min in straight pipes, with a deviation of approximately 2.0% from the theoretical value, meeting the design and practical requirements. The robot successfully climbed pipes inclined at 0° to 90°, operated stably in straight pipes with diameters ranging from 380 to 450 mm, and successfully negotiated obstacles of various sizes and positions. These experimental results confirm the robot’s excellent pipe diameter adaptability and pipeline passability.