Research On Positioning Uncertainty Of Micro-part In Precision Assembly

Assembly is an important step in the production of micro parts,and the positioning accuracy has a direct impact on the final performance of the part.Micro devices have higher requirements for positioning accuracy,while multiple errors will be brought during the process of transfer and release parts,and can not effectively compensate for all errors.It is necessary to study the influence of various errors on part positioning.This paper studies the positioning uncertainty of parts during the assembly process for precision assembly systems.Firstly,the error sources in the assembly process are analyzed,including the angle error between the axes of the slides,the installation error of each module,the motion error of the slide,and the error caused by the adhesion between the operator and the parts.Then,an error compensation model is established for the systematic error,and the model parameters are calibrated,the uncertainty of the calibration result is analyzed.Finally,the influence of the above-mentioned errors on the uncertainty of the part positioning was studied through experiments.A measurement experiment was designed for the influence of errors in the assembly process on the positioning uncertainty.The basic ideas are as follows: control slides to move parts to the same position each time,and capture the characteristics of the parts by an industrial CCD camera.After the image processed,the positional deviation of the center of the circle of the adjacent two images is calculated,and uses the deviation as the positioning error of the positioning.Multiple sets of experiments were performed to calculate the error ellipse of the part positioning error based on the obtained positioning error and related formulae.The area of the error ellipse was used as the evaluation criterion of the positioning uncertainty.The long axis indicates the maximum value of part positioning error in a single direction.Considering that the motion error of the slide table cannot be controlled,the experiment is mainly conducted from the perspective of changing the adhesive force.According to the influence factors of the adhesive force,the contact state of the operator and the parts,the speed of the slide,and the environmental humidity on the positioning uncertainty are mainly studied.Although some of the errors have been compensated,there is still uncertainty in the compensation.The measured positioning error is considered to be the result of the combined effects of each error.The experimental results show that the contact time between the part and the operator,the speed of the sliding,and the ambient humidity all affect the positioning uncertainty of the part by affecting the adhesion force.The change of the contact force has little effect on the positioning uncertainty and setting the above parameters reasonable can improve the positioning uncertainty of parts and improve the assembly accuracy.