Research On Temperature Compensation Technology Of Machine Vision Strain Sensor

Strain is an important indicator for evaluating the safety status of engineering structures and an important aspect of monitoring the health of civil engineering structures.When the structure is damaged due to factors such as load,environment,force majeure,etc.,strain,as a monitoring method,can timely evaluate the safety state of the structure and give an early warning,so as to take remedial measures for the structure.There are many methods for strain monitoring at this stage.Microscopic image strain sensing technology based on machine vision is a newly proposed strain monitoring method,which can achieve the rapid acquisition of structural strain parameters,and has the characteristics of low cost,high precision,simplicity and portability.In the process of strain measurement by a strain sensor,the measurement results will be affected by various factors such as temperature,humidity,and environmental noise.Among them,temperature is one of the factors that cannot be ignored.The commonly used strain stage methods at this stage,such as Resistance Strain Gauges,Fiber Bragg Grating strain sensing technology and Vibrating Wire Strain sensing technology,all have solutions to temperature effects.This paper focuses on the lack of effective compensation method for temperature in the Micro Image Strain Sensing(MISS)method of machine vision.Firstly,two temperature compensation methods are proposed.Secondly,the construction of MISS sensor is improved by using the temperature compensation method.Finally,the feasibility and accuracy of the two temperature compensation methods are proved through experimental verification.After research,the application scope of this method is broadened,and the purpose of integration and improvement of measurement accuracy is achieved.The main work is as follows:(1)In this paper,through the literature review of the existing strain measurement technology,with the help of the thermal expansion properties of the material,two temperature compensation methods for the microscopic image strain sensing technology based on machine vision are proposed,and they are improved according to the designed sensor structure.The two temperature compensation methods can be applied to different scenarios.Research the use of image processing technology to achieve automatic calibration of pixel displacement.(2)Temperature compensation method Ⅰ uses materials with large thermal expansion coefficients to design sensors,which can realize dual-parameter measurement of strain and temperature changes.Firstly,this method performs static experiments on the sensor to prove the stability of the method.Secondly,the influence of temperature on the automatic calibration of pixel displacement is explored,and the display temperature does not affect the calibration of pixel equivalent.Then,the temperature measurement effect of this method is tested,and it is shown that this method can achieve accurate measurement of temperature changes.At the same time it has a high sensitivity to temperature.Finally,an empirical formula for temperature compensation is proposed.Compared with the Fiber Bragg Grating strain sensor,the compensation effect is good and the accuracy is high.(3)The Temperature compensation method Ⅱ uses the same thermal expansion performance as the measured structure to design the sensor,which can realize the measurement of the real strain under the influence of the load and other factors of the structure.Through the temperature experiment of the steel plate,the measurement error after temperature compensation is small,which can meet the needs of practical engineering.The influence of the sensor package structure on the strain measurement is also studied.The temperature compensation method can directly reflect the safe state of the structure under load,and the method is simple and efficient.