3D Surface Topography Measuring Device Development And Its Measuring Path Investigation Under The Guidance Of Machine Vision

Surface topography has a great influence on the mechanical and physical properties of parts,and it is one of the important parameters to evaluate the quality of parts.It is very important to obtain the topography information of parts accurately for guiding production and improving manufacturing technology.Existing parts surface topography measurement devices have the disadvantages of discrete data points,high manual labor intensity and high requirements for measurement environment,which have a great space for optimization.Based on the Capital Construction Funds within Budget for Industrial Technology Research and Development of China Jilin Province“Development of ultrasonic precision machining device for internal circular slicer of hard and brittle materials and cutting shape detector”,machine vision technology is applied to automatically select the appropriate measurement position and guide the measurement process to research on surface topography measurement method and to address the shortcomings of existing measuring devices.And fractal curve is used to design the measurement path to achieve better measurement effect.A surface topography measurement method with high stability,easy operation and low cost is proposed.The main contents of this paper are as follows:（1）According to the functional requirements of the experimental device,we develop the development scheme of measuring device,and build the part surface topography measuring device with visual guidance function.The three-dimensional（3D）topography measurement device consists of attitude adjustment device,topography acquisition device and electronic device support device,which can realize the movement of measured parts,displacement sensor feed,monitoring the measured area and other functions.For the morphology acquisition device of the core part of the test device,the contact displacement sensor and non-contact displacement sensor are respectively studied.GUI interface based on MATLAB is developed and designed to match the software of the experimental device to realize the control of the measurement function of the experimental device and the display of the measurement results.（2）Machine vision technology is introduced to guide the measurement process in order to solve the defect of over-reliance on manual operation in the traditional topography measurement process.CCD camera is used to develop vision system to monitor the measurement area.Corner detection and perspective transformation were used to correct the image,extract the contour information of the measured part and identify the shape of the measured part,which provided the basis for the selection of subsequent measurement path.The corresponding relationship between pixel coordinates and actual length in calibration image can realize the accurate calculation of the position and size information of measured parts.According to the shape,size and measurement path of measured part,the starting point of measurement is automatically selected to guide measured part to an appropriate position to carry out the surface scanning.（3）The Hilbert curve and Gosper curve in fractal curve were introduced as the measurement path to improve the coverage effect of parts with different shapes and realize uniform data collection on the measured surface.At the same time,different paths were projected to the X axis and Y axis directions respectively,and the ratio of components in each direction was calculated as the method to evaluate the quality of curves,so as to explore the uniformity of obtaining the measured surface topography parameters by using each curve.Two kinds of fractal curves were used to measure the local 3D roughness parameters.The results were compared with optical profilometer and the advantages and disadvantages of the two paths were analyzed.The influence of different scanning densities on the error of results was verified.Hilbert curve was used as the path to measure the overall shape tolerance of square parts,Gosper curve was used as the path to measure the overall shape tolerance of circular parts,and the measurement results were compared and analyzed with those of mapping projector,which improved the adaptability of the developed measuring device to the shape of parts.The measurement of 3D roughness parameters and shape tolerance of parts surface can be freely selected according to measurement requirements,which improves the comprehensiveness of parts surface topography acquired by measuring device.In this paper,the measurement of three-dimensional topography information of parts is studied,and the precise control of the measurement process is realized by using visual guidance.A new way of measuring the surface topography of parts is proposed by using fractal curve as the measurement path,which has important application value in parts detection,machining guidance,and improving technology.