Study On Peg-hole Assembly And Measurement Technology Of Multiple Ring Parts

Most peg-hole assembly of multiple ring parts with small size and high assembly precision requirement, are assembled manually by experienced and skilled workers, with high intensity and many factitious factors, thus the quality and efficiency of assembly is influenced greatly. With the characteristic of flexible assembly, automatic and precise system shows the advantage in improving assembly precision and coincidence, and increasing production efficiency. A precise assembly and measurement system is developed according to the characteristics of peg-hole assembly and measurement of multiple ring parts, and the key technology of peg-hole assembly and measurement for multiple ring parts is deeply studied.Based on the analysis of the system function and technological requirements, the assembly and measurement principle is determined, and the precise assembly and measurement system is established. The main function modules of this system, which including assembly and remove module, measurement module, operation platform module and computer control module, are introduced, then the architecture of control system and software are described briefly.After analyzing the assembly model and related problems of ring parts assembly, the study on key technologies of assembly including compliant gripping, axial runout compensation and unqualified parts removing is done. Based on the above study, a compliant gripping mechanism, an axial runout measurement mechanism and a removing mechanism are integrated into the assembly and remove module. The assembly of multiple ring parts is achieved based on the compliant gripping mechanism and automatic assembly control method. A new assembly force and stiffness synthesis compensation method is proposed to improve the assembly precision under a large system deformation caused by large assembly force. The system stiffness cvan be calculated out according to the assembly force and deformation measured during the assembly procedure, and then real-time prediction of system deformation can be achieved, thus the assembly destination position could be modified to ensure the assembly precision. The assembly error caused by the intermediate link, such as indexing rotation, can be decreased through reasonable assembly process plan, therefore the assembly precision can be improved. Vision-based measurement method is adopted to measure multiple ring parts assembled in the narrow assembly hole, and a rigid borescope is taken as the image transmission device to achieve image transmission in narrow space without illumination. To eliminate the influence on measurement caused by the borescope image distortion, a precise measurement method based on rigid borescope is proposed. In this method, the position and attitude information of the ring part to be measured can be obtained by combing the measuring position information and image information of the borescope. The image processing in the measurement operation, comprising enhancement, filtering, sharpening, picking measurement area, edge detection, extraction and fitting, is achieved by using IMAQ Vision toolkit built in Lab VIEW, and the center of the ring part can be measured precisely at last.The experimental results show the developed system can successfully achieve precise assembly and measurement for multiple ring parts in the assembly mold, and both of the assembly and measurement precision can be controlled below 9μm.