Research Of Line Structured Light Vision Measurement System Based On FPGA

With the wide application of computer aided design and computer aided manufacturing(CAD/CAM),complex surfaces are generally used in the product structure design.The tendency of automation,flexible and intelligent in manufacturing system puts forward new requirements for product testing.It is of great significance to improve manufacturing efficiency and processing quality by developing a high precision,better real-time measurement system and integrating it into the processing and assembly process.At present,many processing processes are limited by the working conditions and processing speed of measuring equipment.Therefore,the off-line measurement is widely used,which will induce the measuring error due to the repositioning and reinstalling of workpiece.Structured light vision measurement is a kind of highly efficient,flexible,accurate and stable non-contact measurement method,which can be integrated into the manufacturing system readily.A large amount of data is included in the structured light images and some of these data are redundant.When these data are processed traditionally by the software in computer,the two factors of the processing speed and the extraction precision will be conflictive.Based on the research of vision measurement system and parallel FPGA acceleration technology,a structured light measurement system based on FPGA is developed.A high-precision and excellently robust complex algorithm is transplanted into the FPGA,and the measurement accuracy and the real-time capability of the system can be satisfied.The laser triangulation method is researched according to the contrastive analysis,and the measurement method is selected.The mathematical model of structured light visual measurement system is built by uniting the measurement method and the camera imaging model.In addition,some of the important system parameters are discussed and assessed.The software and hardware functions are divided according to the requirements of image processing and the characteristics of FPGA.The high level synthesis tool(HLS)is used in describing the algorithm in C type language to reduce dependence of FPGA hardware and avoid repeated verification of underlying register logic.During the process of transplanting and synthesizing the algorithm,the optimal speed and area optimization strategy is selected by analyzing the data structure and the mapping relationship.At the same time,the median filter and light stripe center extraction algorithm are improved,mainly for making full use of the parallel characteristics of FPGA and reducing power consumption,by which way the convolution template and number of system calculations reduced,and the processing system obtains higher accuracy with less hardware consumption.At last the synthesized algorithm is encapsulated and released,which is convenient for the subsequent development of similar products.The system measurement scheme is developed,during the design of FPGA hardware,under the guidance of measurement principle.The hardware description language(Verilog)is used to design the image acquisition,data interface conversion,cache,display and storage parts,then the above parts are configured by FPGA and ARM co-processing,and realize the integration.The image processing parameters calculation program and system calibration human-computer interaction interface are developed in the MATLAB environment,based on the analysis of calibration and 3D reconstruction.The calibration experiments of the structured light plane and image acquisition system under different lighting conditions are carried out by using the checkerboard calibration board.Different kind of workpieces are used in the measurement to verify the validity of the system,and the error of the system is analyzed according to the measurement results.