Development and Field Testing of AIRo-7.1: An Articulated Wheeled Robot for Inspecting 3-4 Inch Force Mains in Sewer Pipes

Core Concepts

This research paper presents the development and field testing of AIRo-7.1, a novel articulated wheeled robot designed for inspecting force main sewer pipes with inner diameters of 3-4 inches.

Abstract

Bibliographic Information:

Murata, K., & Kakogawa, A. (2024). Development of a Practical Articulated Wheeled In-pipe Robot for Both 3-4 in Force Main Inspection of Sewer Pipes. arXiv preprint arXiv:2411.03660.

Research Objective:

This research aims to develop a practical and adaptable in-pipe inspection robot capable of navigating the challenging environments of 3-4 inch force main sewer pipes, addressing the limitations of existing inspection methods.

Methodology:

The researchers designed and built AIRo-7.1, a three-joint, four-link robot with omni-wheels for locomotion and spherical wheels for rolling rotation. The robot utilizes a simple open-loop joint torque adjustment system (PWM control) and a position feedback control system for joint angle control. The team conducted preliminary experiments to establish the relationship between PWM duty ratio and actual joint torque. They then tested AIRo-7.1's maneuverability in various pipe configurations, including vertical sections, bends, and diameter changes, culminating in a field test within an actual force main sewer pipe.

Key Findings:

• AIRo-7.1 successfully traversed 3-inch and 4-inch pipes, including vertical sections, 90-degree bends, and a 45-degree elbow pipe.
• The robot effectively navigated an increaser pipe with a diameter change from 3 inches to 4 inches, demonstrating its adaptability to varying pipe sizes.
• During the field test, AIRo-7.1 successfully navigated a 3-meter section of a force main sewer pipe with sewage present, highlighting its real-world applicability.
• Increasing the joint torque enhanced the robot's ability to overcome slippage in the sewage-filled environment.

Main Conclusions:

The study concludes that AIRo-7.1, with its articulated design, open-loop joint torque control, and adaptability to varying pipe diameters, offers a promising solution for inspecting force main sewer pipes. The field test validated the robot's practical functionality in challenging, real-world conditions.

Significance:

This research contributes to the field of in-pipe inspection robotics by presenting a practical and effective solution for inspecting small-diameter force main sewer pipes, which are particularly challenging to access using traditional methods. The successful field test of AIRo-7.1 demonstrates its potential for real-world application, addressing the growing need for efficient and reliable sewer infrastructure inspection.

Limitations and Future Research:

• The field test covered a limited distance (3 meters) and a single force main environment. Further testing in diverse field conditions is necessary to comprehensively evaluate AIRo-7.1's performance and robustness.
• The robot experienced heat generation issues during the field test, leading to damage to a circuit board. Addressing heat dissipation and improving waterproofing are crucial for long-term operation in harsh sewer environments.
• Future research could focus on enhancing AIRo-7.1's capabilities by integrating advanced sensors for pipe condition assessment, such as corrosion detection or leak identification.

Stats

As of 2021, 480,000 km of sewage pipes have already been laid in Japan, and 13,000 km of them are more than 50 years old.
The total length of the force main in Japan is approximately 10,000 km.
The inner diameters of the general force main are designed to be small; 2 in, 3 in, and 4 in (approximately 50 mm, 75 mm, and 100 mm, respectively).
AIRo-7.1 can adapt to a change in the inside diameter of approximately 1 in (approximately 25% of 4 in).

Quotes

"In recent years, the aging of water supply facilities has become more serious, and burst and leakage accidents have begun to occur. In particular, a sewer pipe break leads to gradually erode the soil and may eventually cause a subsidence accident. The risk is even more serious because sewage contains hydrogen sulfide which increases the health hazards."
"It made mandatory to inspect sewer pipes at least once every five years. Some inspection robots have been already commercialized such as scope cameras and self-propelled inspection equipments [1] [2]. However, these products are not available for all sewer facilities."
"Therefore, it has been impossible to inspect them using a conventional products due to the size limitation and maneuverability limitation to three-dimensionally winding pathway."

Key Insights Distilled From

Development of a Practical Articulated Wheeled In-pipe Robot for Both 3-4 in Force Main Inspection of Sewer Pipes

by Kenya Murata... at arxiv.org 11-07-2024

https://arxiv.org/pdf/2411.03660.pdf