Research On Macro-micro Visual Inspection For Micro-assembly

Micro-assembly is the precise integration of multiple microparts of varying scales.The primary method for completing micro-assembly tasks is through microscopic vision-guided localization and manipulation.The accuracy of positioning manipulation is closely related to the resolution of vision measurement.In theory,the higher the resolution of microscopic imaging,the larger the numerical aperture of the objective lens.The corresponding field of view,depth of field,and working distance are also reduced.Some assembly tasks have to be performed at high resolution to ensure accuracy,but their attitude adjustment has to be performed under large field-of-view conditions to avoid interference between actuators,lenses,and workpieces.In such work scenarios,how to account for the large field of view and high resolution of microscopic imaging has emerged as an issue in micro-assembly.To address the difficulty of balancing the large field of view and high resolution of microscopic vision imaging in micro-assembly,we designed the vision unit with macro-micro parallel imaging based on infinity imaging.Finally,a micro-assembly experimental platform was developed which uses macro-micro vision unit guiding.Fiber optic and microfluidic chip alignment assembly experiments validate the capabilities of macro-micro imaging unit-guided realization of micro-assembly tasks.Firstly,the design indexes of the microscopic vision unit are determined based on the micro-assembly task requirements,and a macro-microscopic vision unit is developed with a single objective and dual tube.The optics parameters of the macro-micro vision unit are determined using theoretical calculations.To evaluate the image quality of the macro-micro vision unit,ZEMAX is used to generate the optical path model for simulation.Eventually,the structure of the macro-micro vision unit is established.Second,in order to test the effect of precision motion inspection and micro-assembly operations using the macro-micro vision unit,the micro-assembly experimental platform was developed.It consists of a micro vision feeding module,a part adjustment module,and a macromicro vision unit.The industrial control computer is the control core of the control system of the micro-assembly experiment platform.In the micro-assembly control system,the microassembly strategy and the posture detection method based on the guidance of the macro-micro vision unit are adopted.The micro-assembly employs macro-imaging guidance for attitude alignment and micro-imaging guidance for position alignment.The software framework of the micro-assembly experiment platform is constructed for the assembly task.The micro-assembly operation software is programmed by classes.The optical path error of the macro-micro vision unit is then analyzed to determine the influence of beam splitter and reflector deflection on macro-micro vision unit imaging.The impacts of pitch and yaw angles generated by the X,Y,and Z-axis of the microscopic vision feed module sliding motion on the visual inspection are analyzed.Next,the error compensation model is established to improve visual inspection accuracy.Assembly mistakes are compensated for by experimentally calibrating the macro-micro vision unit,micro vision feed module,and part adjustment module.Finally,experiments were implemented to ensure the measurement error of the macromicro vision unit was less than 0.3 μm and the precision of motion placement was better than2 μm while maintaining the working distance and field of view.Furthermore,the microfluidic chip and optical fiber assembly experiments were conducted using the macro-micro vision unit guided micro-assembly experimental platform in order to achieve a precise connection between the micro-optical fiber and the microflow channel.The tests demonstrate that the macro-micro vision unit can be used for sophisticated micro-assembly vision-guided tasks that demand both high resolution and a large field of view.