Design Of The Displacement Measurement System Based On PSD Position Sensor

Non-contact optical measurement method is an important development direction in the field of precision measurement.This paper is based on the one-dimensional position sensor PSD,using laser triangulation method to build a set of photoelectric displacement measurement system.The main completed work includes:(1)Research the modulation and demodulation principle involved in the system.For the spectrum error during FFT demodulation,the simulation and analysis of actual sampling process with MATLAB are performed,and the accurate amplitude and frequency information can be obtained after FFT transformation if complete period sampling on signal is conducted.(2)Complete the hardware circuit design of the system.The drive circuit is designed for producing sinusoidal current to drive the laser diode.The PSD signal processing circuit is built to convert the PSD output current into a suitable voltage signal for acquisition.A motor control system is adopted so that the system can perform rotation measurement.In order to operate and control the measurement system,the single-chip microcomputer system is designed.(3)Complete the software program design of the system.The signal generation program is designed to generate the sinusoidal modulation voltage signal inputting to the laser diode drive circuit.The ADC acquisition program is written to acquire the output signal of the PSD processing circuit at a specific frequency.The FFT demodulation is used to extract the amplitude information of the modulation frequency,and the PSD spot position is calculate by the amplitude information.The motor pulse signal is designed to drive and control the stepping motor.The Bluetooth communication program is written to realize wireless transmission of the data between the measurement system and the mobile phone.Finally,the coordinated operation of the system’s software and hardware is orderly controlled and realized by the main program of the single-chip microcomputer.(4)The automatic calibration experiment is designed to obtain the relationship between the measured value and the actual displacement value.In order to set the calibration parameters and obtain the calibration results,the upper computer program and the display interface of the calibration system are written and designed.And finally,the actual measurement is carried out based on the calibration results.