On-Line Meter Calculating System Of Cable Based On Laser Doppler Technology

Current cable length on-line measurement accuracy is low.In order to achieve the on-line high-precision of length measurement in cable production process,on-line meter calculating system of cable based on laser Doppler velocity is designed in this paper,Which detects the velocity information of the moving cable by detecting the Doppler shift of the scattered light on the surface of it,and realizes the on-line measurement of the length by the integration of the velocity to the time.The main contents of this paper:According to the principle of measurement,the overall scheme of the system is proposed.The double-beam double-scattering optical path with reasonable structure and reasonable layout is completed according to the scheme.The devices such as lasers,photo detectors and optical lenses are reasonable selection,while the design of the host computer software algorithm is achieved.Combined with the characteristics of solid Doppler signal,a set of laser Doppler signal processing scheme is designed.A filter band adaptive selection algorithm based on finite unit impulse response filter is proposed,which effectively filters out the base signal and partial noise,improves the signal to noise ratio.FFT combined with energy center of gravity correction technology to achieve the accurate extraction of Doppler signal frequency.The hardware circuit of the system with FPGA as the core is analyzed and designed.The amplification and filtering circuit for pre-processing of Doppler signal and peripheral circuit of FPGA are designed.The interface circuit of the Gigabit Ethernet is designed to achieve the communication with the host computer.The PCB board of the whole hardware circuit is completed.Calibration experiments,comparative measurement experiments are carried out in the laboratory.Through these experiments,the adaptive selection algorithm based on FIR filter band and the measurement accuracy and stability of laser Doppler on-line meter system are evaluated comprehensively.The experimental results show that the system can perform on-line measurement in real time and accurately.The error is less than 0.1%.