Research On High Accuracy Alignment And Detection System And Key Technology For Micro Assembly

Preciseness and miniaturization of weaponry and civil products has become an important trend in the development of advanced equipment.As the precise micro system,micro gyroscope,micro accelerometer,micro force sensor and biochip are widely used in aerospace,weapons,and medical equipment,and other industries,the accuracy and complexity of micro system are getting higher and higher,which leads to the more and more urgent requirements for advanced manufacturing technology.A micro system is made up of parts that have different materials and structures,and it is very important to assemble these components into a system that has a specific function.Micro assembly process involves micro operation technology,precise alignment and detection technology,micro force feedback technology,virtual technology,computer graphics,automatic control technology and other knowledge,and its research and application is difficult.There have been some achievements on micro assembly in domestic and foreign research.However,there have no mature and effective technology and equipment in micro assembly,which cannot satisfy the growing demand of high precise micro system.In this paper,a precision alignment and detection instrument is developed,which will be applied to the assembly of micro system.It will be the first time that coaxial image technology and laser confocal alignment method is integrated and applied in the field of micro assembly,which helps achieve the submicron detection and alignment precision.The main research contents and conclusions of this paper are presented as follows:(1)According to the characteristics of micro parts and assembly requirements,the functional requirements of the micro assembly system are analyzed.Based on the study of the micro assembly system and key technology,the overall scheme of high precision micro assembly system was developed.The system adopts double light path detection and positioning system.One alignment and detection system is composed of CCD camera and cube prism,and another one consists of confocal optical path and triangular prism.Its open control system is very complex,which is made up of IPC,independent controllers and multi-axis motion control card.The system is designed for high precision assembly of miniature parts.(2)On the basis of a detailed analysis on the high precision micro assembly system,the static and dynamic characteristics analysis,thermodynamic analysis and structural optimization of the key parts of the system are carried out.The modal frequencies,modal damping and modal shapes of the system are obtained through the analysis and comparison of the experimental and calculated modal results.Based on the above analysis results and the requirements of the high precision micro assembly,the structure optimization is carried out,and the weight of the system is reduced by about 30%,which results in that its first order natural frequency is three times more than that of the ambient vibration frequency.It greatly improves the system’s motion characteristics.(3)Based on the analysis of the geometric errors of the optical path and the motion of the system,the error source of the confocal detection system is identified,and the integrated error model of the system is established through the multi-body theory and the homogeneous coordinate transformation theory.In order to further improve the precision of the system,the error sensitivity analysis is carried out by the Sobol’s algorithm of the variance.It is concluded that the angle error which is perpendicular to the assembly surface in the micro assembly process has a great influence on the assembly precision,which provides a theoretical reference for the following calibration and optimization design.(4)In the contact assembly stage,it is difficult to detect the relative position and posture of parts.In order to realize the high precision assembly,the relationship between the assembly force and the position of the parts is studied,and a high precision alignment assembly method is proposed based on the micro force / position mapping relationship.In view of the genetic algorithm(GA)and the forward feedback(BP)neural network,the mapping model of the micro force / position of the parts is established,and the corresponding assembly strategy is formulated.Through the experiment of axis-hole assembly of 5μm and 2μm unilateral tolerance,the feasibility and validity of this method is verified,which provides a effective direction for the assembly of micro assembly.(5)On the basis of detailed analysis of the whole micro assembly process,the high precision calibration and adjustment of each movement and detection in the assembly alignment process is carried out.In this paper,we mainly focus on the calibration of the assembly reference platform,the calibration of the optical prism position and pose,and error calibration of alignment detection module in confocal system.