| Jet pipe servo valve,the key component in the electro-hydraulic control system,can realize the function of power amplification and the conversion of hydraulic and electrical signals.The jet pipe servo valve was widely used in the aerospace field because of its high control accuracy,strong anti-pollution ability and reliable working.The jet pipe servo valve controls the output pressure and flow of the servo value by jet.The nozzle’s jet shape directly affects the static and dynamic performance of the servo valve.Therefore,it is very important to grasp the change law of jet shape for the performance of jet pipe servo valve.The result of simulation illustrates that the jet shape of nozzles,formed by different machining quality,was different.Based on micro-vision technology,micro-jet observation system of jet pipe servo valve was developed,and the experiments of nozzle quality detection and jet characteristics research were carried out.1、Hardware platform of jet pipe servo valve micro-jet observation system was designed,which mainly contains the servo valve clamping unit,jet acquisition unit,oil mist purification unit and the oil recovery unit.The servo value installation and oil connection were realized.The jet acquisition was carried out under closed condition,and the jet beam of diameter 0.2mm could be identified.The acquisition position could be adjusted along the jet direction,and the observation range up to 50 mm.Solving the problems of oil atomization and droplet spatter disturbing image continuous acquisition and jet oil recovery.2、Micro-jet observation control system was developed.The overall circuit control scheme adopted that week current controls strong current.The whole control circuit was designed around the data acquisition part and the motion control part.The control flow of jet acquisition was designed.Jet start,image acquisition and save,oil mist processing were controlled by trigger synchronously.The liquid location of tank was measured in real time during the jet acquisition process.An interactive interface for jet acquisition control was designed,which could display the dynamics process of jet acquisition in real time and adjust the position of jet acquisition by keyboard input.3、Algorithm for jet contour extraction and feature measurement was written.First,image cropping obtains preliminary ideal processing regions,and setting ROI obtains characteristic contour processing area.Gaussian filter was used to eliminate noise disturbance,Otsu Thresholding was used for threshold segmentation and binaryzation,open operation and closed operation were used to eliminate the isolated contour and fine contour,and canny detection method was used for contour recognition and detection.The final jet contour was selected by combining contour perimeter,area and characteristic moment.An algorithm was designed to extract the multiple jet contours.The width of the contours and jet actual distance were measured by visual calibration method.The man-machine interface of image processing was designed for easy operation.4、Nozzle quality testing experiment and jet contours experiment were carried out.The result of simulation illustrates that the jet shape of nozzles,formed by different machining quality,was different.The nozzles with different machining qualities were distinguished efficiently,and the nozzle qualified machining standards were proposed.The jet morphology observation experiment and jet broadening research experiment were carried out,which found that the jet pressure and the jet distance have a positive effect on the jet broadening.Within the range of 0.5-7.5MPa pressure and 0-50 mm distance,the larger the jet pressure is,the larger the jet distance is,and the larger the jet broadening value is. |
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