| The four-circuit protection valve is an indispensable part of the dual circuit brake test system,which can guarantee the normal work of the other circuits,when a certain brake circuit failure happens.The qualification of the opening pressure of the four-circuit protection valve is an important part of the production of the four-circuit protection valve.As for the problem of low flexibility and imprecise positioning for the opening pressure regulation of four-circuit protective valve,a system based on visual localization for adjustment of opening pressure of four-circuit protective valve is designed.The article’s main research contents include:Firstly,Based on the mechanical structure and working process of the four-circuit protection valve,the opening pressure regulation principle of the four-circuit protection valve is analyzed.（First,the paper analyzes the regulating principle of the four-circuit protection valve’s opening pressure.）According to the requirements of the system test,the overall program of the system is developed,including system hardware design,image processing algorithms and software design.Secondly,The system hardware mainly includes automatic clamping control module,gas path on-off control module,data acquisition control module,machine visual localization module,servo motion control module,etc.The machine vision positioning module is the core part of the system,including camera,lens,light source and so on.Considering the repeated positioning system 0.5mm and precision vent size 40mm long 40mm parameters,so the system chooses MV-EM200C,the camera pixel resolution of 1600 long 1200,the size of 1/1.8 CCD.According to the selected camera and object distance requirements,system selection focal length range is 8mm50mm,image size for 1/2 lens AFT-0850ZMP.Meanwhile,according to the shape of the exhaust port,the system selects AFT-RL5928-65W ring light source;Servo motion control module mainly includes x axis motor,y axis motor,z rotating shaft motor,which separately control the movement of tightening mechanism in horizontal direction,vertical direction and vertical direction.Data acquisition module collects opening pressure data from different pressure sensors which can set on different stations’exhaust ports.Thirdly,According to the characteristics of the four-circuit protection valve exhaust port image collected by the camera,it is proposed to use the wavelet half-soft threshold to denoise,and combine the NI template matching,image interception,binarization and Hough circle detection algorithm to achieve the positioning of the center coordinates of the exhaust port screwFourthly,On the basis of analyzing the hardware design and image processing algorithm of the system,the realization of the function module of the system detection software and the design of the detection process are completed.The PID algorithm is used to realize the precision adjustment of the opening pressure of the four-loop protection valve.Fifth,Performancing evaluation of the test bench,the Opening pressure of21exhaust port,22 exhaust port,23 exhaust port and 24 exhaust port can meet requirements of the measurement capability index Cg≥2,Cgk≥2.Testing the opening pressures of four-circuit protection valve exhaust ports on a single station and analyzing the results of the test,the results show that:the stretching uncertainties of the opening pressures of 21 exhaust port,22 exhaust port,23 exhaust port and 24exhaust port are（649.20±2.72）kPa,（650±1.92）kPa,（650.10±1.14）kPa,（650.20±2.72）kPa respectively,which can meet the requirement of standard opening pressure（650±5）kPa for 3135N-001 four-circuit protection valve. |
