Cable climbing device to monitor and detect damage of suspension bridge cables

Currently, the world has begun to develop self-propelled devices with cameras that can climb cables to transmit image signals to the observation center. However, these devices are mainly visual observation of the cable and are still in the testing process. Meanwhile, the monitoring and evaluation of the cable's tensile attenuation through other characteristics of the cable such as the amplitude of vibration and, the frequency of the cable's oscillation have not been applied. From the above practical requirements, Dr. Nguyen Van Quang and the research team of the Institute of Mechanics conducted the project "Research and development of cable climbing equipment system to monitor and detect damage of suspension bridge cables" (project code VAST01.05/20) -21). The topic was graded fairly by the Acceptance Council at the Vietnam Academy of Science and Technology.

The goal of the research team is to design and develop a cable climbing device to remotely monitor and detect the damage of the cable to ensure the safety of the suspension bridge's operation. The main functions of the device are to observe the cable surface with a camera to detect damage on the surface, measure the dynamic characteristics of the cable such as amplitude of vibration, frequency of vibration along the cable length to detect and evaluate, any any decrease in tensile strength of the cable.

Nowadays new and modern structures such as bridges, high-rise buildings, tall towers, cranes are all installed with structural monitoring systems to monitor various parameters such as inclination, temperature, humidity, vibration, etc. as shown in Figure 1.


Figure 1. Illustrative diagrams of the structural monitoring system

The self-climbing device of the suspension bridge carrying a data collection device for remote cable damage monitoring is called a cable climbing robot. Cable climbing robots are divided into four types based on the method of attachment on the cable, which are magnetic, pneumatic, electric, or spring-loaded adhesion methods.

Figure 2. Self-climbing device for monitoring suspension cables (Infrastructure Preservation Corporation)

In this topic, the team chose to study the MEMS MPU-6050 accelerometer sensor. This is a common sensor, low cost and available in Vietnam market as shown in Figure 3. Parts MPU-6050 is the world's first Motion Tracking sensor designed for low power requirements, low cost and high performance of smartphones, tablets and wearable sensors. The MPU-6050 combines InvenSense's MotionFusion™ program and runtime calibration firmware allowing manufacturers to eliminate the system-level selection, quality, and integration of discrete devices in motion-enabled products, ensuring that the sensor fusion algorithm and calibration process deliver optimal performance for consumers.

Figure 3. Accelerometer MPU-6050

The result of the project is that a cable climbing device system has been built to monitor and detect damage to the suspension bridge cable, including: 3-D oscilloscope sensor, 3 camera observation sensors, transceiver device,. signal via wifi and 4G, transmission control software and signal processing from the sensor to the CABLEHM2020 processing center, image recognition software to detect damage by images from the camera.

Figure 4. Cable climbing robot and PULSE oscilloscope system (viewed from the back of the PULSE machine)

The system was tested at the Laboratory of Engineering Mechanics, Institute of Mechanics, and compared with the PULSE vibration measuring and processing equipment of Brüel & Kjær of Denmark. The system has been tested at Trung Ha suspension bridge, Hoa Binh province, as shown in Figure 5. This is a bridge spanning the lake area between Trung Hoa and Ngoi Hoa communes, Tan Lac district, Hoa Binh province. The results showed that the oscillating signal from Trung Hoa cable was transmitted wirelessly to the computer and processed online. The results of measurement and analysis of the cable's vibration signal show that the sensor system is in good working order, capable of monitoring the damage to the suspension bridge cable.

Figure 5. Set up a transmission line to receive and transmit oscillation signals between the oscilloscope sensor and the computer

The project has built a cable climbing robot model in the laboratory to monitor and detect damage of cable-stayed bridge cables and suspension bridges. However, to be able to commercialize the product, it is necessary to continue researching to make a robot capable of adjusting the balance force on the 3 wheels, so that the wheels move according to the pre-designed trajectory, and at the same time the robot must be able to withstand the impact of the environment such as rain, wind, corrosion, etc. In addition, it is necessary to continue to develop methods of analyzing image signals and vibrations to be able to most accurately assess the current status of cables in practice.


Translated by Quoc Khanh
Link to Vietnamese version

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