Research On Confocal Micro Assembly System And Its Precision Control Method

With the wide application of precision micro system such as inertial devices and micro sensors in aerospace,weapons,and medical industries,the structure and function of micro system are becoming more and more complex,and the requirement for the precision of micro system is more and more high.Therefore,the high precision alignment assembly for the micro parts is a hot and difficult point in the research at home and abroad.Micro assembly process involves micro clamping technology,precision alignment detection technology,micro force feedback technology,computer graphics and automatic control technology and other theories,the research is difficult and the process is complex.In the field of micro assembly,research at home and abroad have made great achievements,but still lack of mature technology and high precision instrument.And it can not meet the growing demand for high precision micro assembly system products.Based on the proposed coaxial alignment detection principle,this paper designed a confocal alignment detection method.We used the confocal laser scanning microscope and the trapezoid prism to form a confocal alignment detection subsystem.The image detection resolution of the system reaches the nanometer level,and the assembly alignment precision reaches the sub micron level,which provides a new idea for the research of the micro assembly system.The high precision micro assembly system is integrated with the coaxial alignment detection technology and the confocal alignment detection technology,which can improve the precision and efficiency of assembly.The main research contents and conclusions of this paper are presented as follows:(1)This paper briefly introduces the background and significance of the research of micro assembly,introduces the current situation and trend of the research at home and abroad,analyzes the research status of the micro device alignment detection method,and summarizes several calibration methods of the micro assembly system.Summarize the limitations of the existing alignment technology.(2)In order to overcome the defects of the micro assembly system and improve the assembly precision,the overall design scheme of the high precision micro assembly alignment detection system is proposed.In this paper,a detailed introduction is made to the camera alignment detection subsystem and the confocal detection subsystem,and the working process of the micro assembly system is described.Design and introduce the principle of confocal alignment detection,which can effectively solve the contradiction between the field of view and the resolution.The control scheme of micro assembly system is described in this paper.The motion control system adopts the open system of "PC + independent controller + multi motion axis control card".(3)The error propagation model of six degree of freedom prism pose adjustment mechanism is established,and the effect of the error of the mechanism on the prism pose is analyzed.By using this mechanism,the pose of the prism can be adjusted accurately,and the error caused by the prism in the confocal alignment system is reduced.The effect of the deviation of the prism pose on the imaging of the microscope is studied,and then the verification experiment is carried out with a special reticle calibration board.(5)In order to guarantee the precision of the high precision micro assembly alignment detection system,the system is calibrated and compensated.First,calculate the angular deviation of each direction of the prism using the square groove on the surface of the prism.Then,the “inverse fitting method” is used to calibrate the confocal alignment detection system,and the system error is obtained.(4)As the uncertainty is an important evaluation criterion of the assembly system,the uncertainty evaluation of the high precision micro assembly system is carried out.It is concluded that the expanded uncertainty of the system is 3.664?m.In order to achieve the micro assembly alignment accuracy of sub micron level,the micro assembly system should be calibrated before assembly and the error of the key components should be compensated.Finally,assembly experiment of optical fiber and glass tube is carried out,and the maximum assembling error is 1?m.The calibration of the system should be carried out before the assembly,and the system deviation should be taken into account during the alignment process of the parts.The assembly verification experiment shows that the assembly accuracy of the high precision micro assembly system can reach sub micron level.