Research On Cable Force Identification Method

This paper discusses a non-destructive measurement techniques--Magnetic flux sensor monitoring, and explains how it works, analysis of its influencing factors and handling approaches in detail, derived the basic relationship about magnetic permeability and cable tension. Using electromagnetic sensor placed in the cable body, cable force is measured by the change in magnetic flux test. This new type of magnetic sensor can be used to monitor civil construction’s cables and the steel’s tension, can also monitor long-term the stability of the large cable bridge. Magnetic flux method has been used in foreign countries stress test on various structures, getting good results. Also achieving initial success in our country.The sensor have good dynamic response, The error is about±0.2%in measurement repeatability, meeting the requirements of on-line measurement to cable force.During Yueqing Stadium’s installation and construction of cable, some key position of Magnetic flux sensor is installed to ensure the safe operation of construction quality and cable, composed the online monitoring system with union switch boxes, magnetic bombs instrument, GPRS wireless sensors, acting the real-time monitoring of Stadium construction and operations.This paper briefly discusses several measurement methods to cable force, for example hydraulic jack tables, frequency vibration method, Magnetic flux method. By describing working principle, scope and the respective cable force measurement accuracy of the various methods, Magnetic flux sensor solves the limitations of other methods.This paper proposes two methods to solve the cable force, the first method use the relative permeability incremental fitting relationship with the cable tension to solve cable force, and conduct the temperature compensation, calculating relative magnetic permeability results; the second method not to consider the impact of the direct use of the output voltage of the temperature integral value fitting relationship with the cable tension cable force to solve.Magnetic flux in the use of cable force measurement system consists of two steps:Calibration phase and measurements phase. This paper elaborated on calibration phase, by setting different charge-discharge voltage, different cable lengths, different devices and magnetic flux sensors are placed at different positions from the cable ends and other parameters, comparing integral voltage changes when loading the same level.Selecting the zero value have a great impact on the solutions to solve cable force results. Here are three kinds of methods to select a value of zero, a two-point interpolation, a three-point interpolation, a five-point interpolation,Temperature changes always play an important role in process of solving the cable force, and can not be ignored. Temperature compensation during solving the cable force is always a question. How better to eliminate the problem of the influence of temperature, which is a serious problem in the future.