A lightweight bridge inspection system using a dual-cable suspension mechanism

Abstract Visual inspection is the primary means of evaluation of the structural conditions of a bridge. Since visual inspection often requires engineers to place themselves in hazardous environments, many researchers have developed inspection vehicles and robot arms in order to increase safety and accessibility during inspections. However, the use of such heavy equipment may only be suitable for large bridges due to restrictions in working space. Therefore, this research aims to develop an innovative bridge inspection system that is portable, simple, affordable, and can be easily applied on smaller yet large number bridges. We developed a systematic approach, which includes a lightweight inspection system using a dual-cable suspension mechanism, as well as strategies to conduct inspections. The inspection system is composed of three components: the controller, the dual-cable suspension, and the inspection platform. By using a dual-cable suspension mechanism, the bridge inspector can manipulate the controller to place the inspection platform beneath the bridge and capture images with digital vision devices. Unlike robot arms or heavy vehicles, the cable-based system has the capacity to sustain much more than its own weight. This means that the total weight is greatly reduced and the cost is much lower than in existing methods. Additionally, the inspection strategies developed in this research can provide complete, efficient and flexible inspection procedures. Vertical and horizontal inspection strategies have been developed to allow sequential inspection for normal structures and multi-view inspection for special structures by manipulation of the inspection system. A prototype of the inspection system has been constructed and two field experiments were conducted to test the feasibility of the proposed method. The experimental results proved that the proposed system was able to work efficiently on a narrow bridge without affecting the traffic. The inspection system can also provide centimeter-level resolution inspection images, allowing general defects such as cracks and spalling concrete to be seen clearly. With further research, the proposed system and concept is expected to enhance overall bridge inspection efficiency.