| As the key part of high-precision alignment technology,high-precision planar parallel alignment platform is one of the hotspots in the field of high precision.It integrates Precision mechanics,electronics,servo driving,motion control and image processing techniques.It is the intersection and fusion of multi-disciplines,and is widely used in micro-machine,ultra-precision machining,nanotechnology,semiconductor and LCD Monitor,with high theoretical research meaning and practical application value.The traditional high-precision alignment platform cannot meet the requirements of high-precision alignment technology nowadays.In this thesis,a planar parallel alignment platform with a new type of transmission chain is taken as the research object.Through the analysis of the configuration of the parallel mechanism and the visual aided system,a matching platform with high precision alignment performance was designed.The high-precision alignment platform was analyzed from the kinematics,control system to systematic error.The main research contents of the thesis are as follows:(1)Firstly,combined with the research status of high-precision alignment technology at home and abroad,the overall scheme design of the alignment system of high-precision alignment platform was determined.A new 3-PPR planar parallel alignment platform for motion chain layout was proposed,and the three-dimensional model,motion form,theoretical analysis and scheme design of the platform and its kinematics were given.The imaging model and transformation matrix of the camera were established.The camera was calibrated by Opencv library function and Zhang's calibration method to find the homography matrix of the system.(2)It established the kinematics model of the parallel mechanism,and analyzed the kinematics model of the positive and negative of the alignment platform by analytical method and closed-loop vector method.The relationship between the positional deviation of the MARK point on the aligning object and the posture deviation of the moving platform was obtained by the instantaneous center method and the stepby-step aligning method.The singular configuration of the platform was analyzed,the workspace of the platform was calculated and simulated using MATLAB.(3)The hardware and software design of the control system was completed.The hardware included motor and driver,controller,electrical connection and control system initialization configuration.The detailed calculation process was introduced for the required moment of inertia and input torque of the platform.The software included software development platform,alignment control program and interaction interface.These programs of kinematics positive and negative solutions,homing procedures,visual communication,alignment mode and motion state monitoring were introduced with emphasis.(4)The differential method was used to establish the error model of the platform by analyzing the error sources of the platform.The related errors were analyzed and integrated,and two error compensation methods were proposed: hardware error compensation and software error compensation,they were applied to high-precision planar parallel alignment systems.(5)It tested the platform control system to ensure the operation performance of the control system and the input accuracy of the platform.The overall motion control accuracy of the 3-PPR planar parallel alignment platform was measured,and the alignment accuracy of the high-precision alignment system was adopted under the condition of error compensation.The experimental results show that the alignment platform studied in this thesis can achieve a relocation accuracy and a driving accuracy of 1?m.It can complete the automatic alignment of the positional error and the angling error within ±5?m,0.0038° within 5s,and the position error and angling error within ± 10 m,0.0023°,which proves that the alignment platform has satisfactory alignment performance. |
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