Micro-deformation Measurement System Based On Position-sensitive Detectors

Modern bridges,ships,airplanes,etc.are prone to micro deformation due to external forces such as temperature,wind wave,air pressure and so on,which has certain security risks.Therefore,in order to ensure the reliability and safety of large structures or equipment,it is necessary to measure the micro deformation.However,with the rapid development of optical technology,sensor technology and computer technology,deformation measurement is facing increasing requirements.It not only needs to have high-precision performance,but also needs to further achieve the characteristics of rapid and intelligent.At the same time,it is necessary to ensure the repeatability and stability of the measurement system.This makes traditional measurement methods such as resistance strain gage method and dial indicator method have certain limitations.At present,fast and intelligent photoelectric detection technology has been widely concerned,but the existing photoelectric measurement often chooses the charge coupled device as the detection sensor.The resolution of the device is limited by the size of its own pixel,which is difficult to improve,and its response speed is also low.This paper proposes a micro deformation measurement system based on Position Sensitive Detector(PSD).The PSD is a semiconductor device based on the lateral photoelectric effect.It has the advantages of high position detection accuracy,fast response speed,no measurement dead zone,and low requirements for the optical system.It is expected to overcome the shortcomings of the existing measurement technology and achieve high-precision micro deformation measurement.The main research work of this paper is as follows:1.For the shortcomings of the existing micro deformation measurement methods,this paper proposes a measurement scheme based on PSD sensor imaging method.On the basis of mastering the basic principle and performance index of PSD,the specific structural parameters of micro deformation detector head are selected,the indicator light source is determined,and the frequency division multiplexing technology is used to realize the synchronous detection of multiple beams by single PSD.By establishing the combined coordinate system of light source,PSD and lens,a multi-light source measurement model is proposed to calculate the six degree of freedom deformation.2.Aiming at the noise problem of PSD signal processing system,this paper designs a weak signal processing circuit.Firstly,the noise model of PSD detection circuit is analyzed,and the theoretical derivation is made.Based on this,a low-noise preamplifier circuit is designed,and the performance of the circuit is verified by simulation software.Then,a lock-in amplifier circuit is designed to extract the target signal of specific frequency,filter out the stray noise and improve the signal-to-noise ratio of the system.Based on the Altium Designer software,the hardware PCB is designed and manufactured,and the area of PCB is reduced by optimizing the wiring and layout of devices.In addition,the anti-interference measures of the circuit board design are proposed to optimize the signal integrity of the entire circuit system.3.In view of the low efficiency of the traditional measurement system,the latest generation ARM processor STM32F407ZGT6 is selected as the control core,and data is collected and processed through the serial peripheral interface protocol.The software design is based on the Keil MDK development environment,which mainly completes functions such as sampling of external high-precision analog-to-digital converters,initialization of system modules,communication between circuit modules,and liquid crystal display.Through a series of experiments,this paper verifies the reliability of the design of the micro deformation measurement system based on PSD.The system has the advantages of high accuracy,good stability and repeatability,low cost compared with the related research abroad,wide practical range and very important application value.