Research On Sub-pixel Level Angle Displacement Subdivision And Error Compensation Method

The photoelectric angular displacement measurement technology is a precision measurement technology that converts angular displacement into a digital quantity,and has been widely used in the fields of national defense and industrial control.With the development of aerospace technology,higher requirements are put forward for photoelectric angular displacement measurement devices,not only reducing the diameter size and weight,but also improving the resolution and accuracy of the device.The image-type angular displacement measurement technology studied in this dissertation,reduces the volume of the angular displacement measurement device through optical imaging technology;uses digital image processing technology to improve the resolution and accuracy of the angular displacement measurement device,which is of great significance to realize high-precision and high-resolution small angular displacement measurement.On the basis of referring to a large number of domestic and foreign reference,the current research status of image-type angular displacement measuring devices is studied.By comparing the working principle with the traditional angular displacement measuring device,the characteristics and principle of the image-type angular displacement measuring device and the main factors affecting its accuracy and resolution are deeply analyzed.A small high-resolution angular displacement measurement method based on lensless near-field imaging is proposed.Without lens,the parallel light source directly illuminates the code disk.High-precision and high-resolution angular displacement measurement can be achieved under a small-volume measuring device.A high precise location method for the centroid of the precise code track is proposed.CAMERALINK is used to transmit code disk images to PC in real time.Optimizing the parameters of the lighting system,and the image detector collects the clearest code disk image.Gaussian sliding average algorithm and uniform interpolation algorithm are used to process the code disk images in real time,and efficient and stable precise code track centroid positioning is realized through the square weighted centroid calculation.It can be seen from the simulation results,the centroid positioning accuracy is effectively improved,laying the foundation for sub-pixel angular displacement subdivision and error compensation.A sub-pixel angular displacement subdivision method based on sine approximation is proposed,using sine approximation and geometric relationship derivation,a sub-pixel angular displacement subdivision model is established,sub-pixel calculation is realized,and hardware transplantation is completed.This subdivision method occupies less system memory and can achieve higher resolution angular displacement measurement;experimental results show that this subdivision method achieves 8192 angular displacement subdivision,which improves the resolution by 5-bit.At the same time,a code value correction method based on spatial position is proposed.The experimental results show that the precise code and the coarse code are connected correctly and there is no error code phenomenon.Error compensation methods based on unilateral image acquisition are proposed.An error compensation method based on triangle wave fitting is proposed,which uses triangle wave to fit the angle measurement error curve to realize error compensation.It is verified by experiments that after error compensation,the accuracy of the measuring device is increased from 37.25 " to 8.75".In order to further realize adaptive error compensation,an error compensation method based on the fitting of the center line of the precise code track is proposed.The center position of the code disk is obtained by fitting the center line of the precise code track by the least square method,the lateral component of the code disk eccentric distance is calculated and realized real-time error compensation.When the eccentric distance of the code disk is0.05 mm,after error compensation,the accuracy of the measuring device is increased from 536.52 " to 228.61",which effectively improves the system accuracy.Using the sub-pixel angular displacement subdivision method and the unilateral image acquisition error compensation method studied in this dissertation,the code disk with the diameter of 38 mm has reached 21-bit resolution.Small-scale,high-precision,high-resolution angular displacement measurement can be achieved.It is of great significance for the development of a small,high-precision and high-resolution image-type angular displacement measurement device.