Research On Stiffness Detection Technology Of Spring Tube And Feedback Stem Based On Charge-coupled Device

Electro-hydraulic servo valves are widely used as control device in the field ofaviation, aerospace and navigation, it can transform a weak current (a fewmilliamperes) control signal into dozens of horsepower or more hydraulic power tooutput, and drive a variety of load to control position, speed or force and so on. Thestiffness parameters of precision elastic components (spring tube and feedback stem)have a significant impact on electro hydraulic servo valve static performance anddynamic performance, therefore, need to be strictly controlled during production.The stiffness detection of precision elastic components (spring tube and feedbackstem) is not intended to give the information of qualified in the traditional sense, butto guide cone section of feedback stem and thin-walled of spring tube for furtherfinishing according to the test results.Firstly, this dissertation summarizes the development of stiffness-measuringtechnique for precision elastic components at home and abroad. According to therequirements of this issue, and analysis the working principles and tress conditionsof spring tube and feedback stem in electro-hydraulic servo valve, determining thestiffness measurement principles. This subject research that the stepping motordriven by the computer to automatically load on the force sensor, taking precisionelastic components’ image which under different loading force buy CCD imagesensors, processing image, outputting test results, and drawing the stiffness curveand so on.Secondly, driving CCD image sensor for image acquisition and evaluatingimage quality buy image entropy. Then need to gray-scale transformation, mediumfiltering, binarization, boundary extraction, image thinning, anti-color images forimages. For each image preprocessing step gives different algorithm and comparisonto determine the best operator. And also analyzing the extraction algorithm of imagecoordinates, eventually adopt the method of average coordinates.Finally, according to stiffness measurement requirements, in the Windows XPenvironment, with vc++6.0MFC platform for software design, establishing a set ofstiffness measurement software systems. Developed software interface have ninemodules which includes basic information area, the image capture area, imageprocessing area, the stiffness measurement area, curve drawing area, CCDcalibration area, the stepper motor control area, camera control area and fileprocessing area. Then, debugging mechanical parts, control circuit and software ofstiffness measuring instrument, and analyzing experimental error for the test results.