Research On The Control System For A Direct Detection Doppler Wind Lidar

The Doppler Wind Lidar (DWL) is an effective tool that can provide accuratewind profile measurement. A DWL emits laser into the atmosphere, and the Dopplerfrequency deviation of aerosol particle and molecule of that can provide theinformation of wind. In order to measure three dimensional wind fields, thedifferent part of DWL should be precision synergy and cooperation. For thispurpose, a control system of DWL based on LabVIEW platform has been developedin this paper.We design software control system for each device that can be independentutility in different section of DWL，and we divide the control system into differentparts according to different tasks. These tasks include coaxial adjustment oftransmitting and receiving, scanning of two dimensional turntables, scanning ofinitial working location, working location locking and detection and processing ofweak signal. In the end, make different tasks of DWL into an order according to thework procedure, so that the DWL can be operated fast and precisely.This paper emphasizes the research on working location locking and detectionand processing of weak signal. The drift of working location will bring into hugeerror; just because of this a PI type controller has been developed in this paper.After that the optimal parameters have been found for the PI controller. We performan experiment on working location locking with this PI controller, and the accuracyof locking can reach to0.5MHz less than1MHz of the target of DWL.Detection and processing of echo signal is related to the precision of themeasurement of wind profiles, d it also effects the working time of DWL. In orderto solve the problem that the echo signal attenuates fast with the growth ofdetection range, we divide the echo signals into two segments. The echo signal ofone segment is processed in analog mode, the other is in photon counting mode.The echo signal of one radial direction is measured repeatedly in order to eliminatenoise effects. The accumulation of photon numbers in remote can accurately reflectthe intensity of echo signals. A system of Detection and processing of echo signalhas been developed. It can realize measurement and processing of echo signal perlaser pulse, so that lots of unnecessary dates cannot be saved, the work efficiency ofDWL has been improved. At last, we measured the echo signal in9Km and got abetter result.