Flexible Electronic Gearbox Design And Accuracy Control Method Study

Electronic Gearbox (EGB) is a special multi-axis synchronous motion control method. It not only can realize the complex coupling axes control, but also has many outstanding features, such as the wide range transmission ratio, high transmission precision and convenient adjustment. The basic function of Electronic Gearbox is to take the place of traditional mechanical transmission chain, implement two or more movements control with constant or variable speed ratio, and guarantee the strict synchronous relationship between axial movements. In CNC gear cutting machine tools, Electronic Gearbox control module can realize the synchronous multi-axis movements following the given constrained relationships. Using the software control strategy of Electronic Gearbox not only can satisfy the requirements of the cylindrical gear hobbing and gear shaping multi-axis movements, but also can satisfy the variable ratio transmission requirements of non-circular gear machining. Gear generating depends on the coupling movements of hob cutter axis, gear blank axis and the additional movement of feeding axes, which are controlled by the Electronic Gearbox. The gear machining accuracy contains both the contour precision of cutting tool path and the synchronization precision of tool axis and gear blank axis.A flexible Electronic Gearbox for generating process was designed by this dissertation, and it was enforced in the home-made gear machining CNC. Then, its accuracy control methods were studied in depth. The main research content of the dissertation is as follows.1. The mathematical models of gear hobbing, gear shaping and non-circular gear machining were deduced, through analyzing and studying the gear machining principle. A Master-slave flexible Electronic Gearbox structure was built. Gear hobbing Electronic Gearbox, gear shaping Electronic Gearbox (i.e. the Electronic screw guide) and the non-circular gear machining Electronic Gearbox can be obtained respectively, through changing the Electronic Gearbox coefficient and the CNC axes redefinition. Then, the concept of flexible Electronic Gearbox was proposed, and the changeability and reconfigurable flexible characteristics were fully demonstrated.2. The flexible Electronic Gearbox interpolation module was proposed and the overall architecture of CNC software was designed based on the modularized and reconfigurable idea. The internal information flow of CNC software was analyzed in detail, and the flexible Electronic Gearbox was embedded in the gear machining CNC system seamlessly. The flexible Electronic Gearbox control through NC programming was realized in the CNC system which was developed by our institute. Through experimental verification, the control accuracy meets the requirements of gear machining inner-link transmission.3. The common basic control strategy of contouring accuracy and tracking accuracy in CNC system, the control structures and application conditions were studied in detail, then, the basic control model of flexible Electronic Gearbox was established. An appropriate gain matching method was chosen and the gain matching mathematical model was deduced, according to the flexible Electronic Gearbox structure characteristic. The gain matching experiments were conducted on the closed-loop experimental platform, and the validity of the model was verified. Besides, considering that gain matching method can bring poor tracking precision to a certain extent, the cross-coupling compensation model was established combined with the characteristics of tool path in the process of Electronic Gearbox control movement. Then the cross-coupling control was used between the feed axes, the experiments were also conducted on the closed-loop experimental platform, and the validity of this model was verified. Finally, zero phase error tracking control method was studied because the Electronic Gearbox control model of this dissertation has higher request for slave axis tacking precision. It can realize uniaxial high-precision tracking control under the condition of the accurate system model has been established and the leading signal was known.4. The realization principle of the integrated controller which consists of feedforward controller and cross-coupling controller was studied, and then its design procedures and stability were analyzed in detail. It was proved that the integrated controller can improve both contouring accuracy and tracking accuracy. In the case of cylindrical helical gear axial hobbing process, the causes of Electronic Gearbox control error were analyzed, and the relevant error calculation formulas were derived from the point of processing technology and geometric aspects. The flexible Electronic Gearbox cross-coupling controller (ECCC) was designed based on the structure characteristics of the common Master-slave Electronic Gearbox and the design principle of integrated controller. MATLAB simulation proved that the flexible Electronic Gearbox cross-coupling controller has a better control effect. What’s more, the fuzzy control principle and biological immune regulation mechanism were studied, and a fuzzy immune PID controller was obtained which consists of fuzzy control, biological immune controller and PID controller. Then the intelligent control algorithm was used in the flexible Electronic Gearbox cross-coupling controller, the simulation results showed that the proposed control method can further improve the control precision of the Electronic Gearbox.5. The flexible Electronic Gearbox cross-coupling controller and the common Master-slave Electronic Gearbox controller were embedded in the gear machining CNC system respectively. Then the axial hobbing experiments were conducted, the experiments results showed that the flexible Electronic Gearbox cross-coupling controller has better control precision. On this basis, the following experiments were conducted:diagonal hobbing motion control using the flexible hobbing Electronic Gearbox; cylindrical helical gear shaping motion control using electronic screw guide; one order elliptic gear machining motion control using non-circular gear hobbing Electronic Gearbox; and the three order elliptic gear machining motion control using non-circular gear shaping Electronic Gearbox. All the experiments results showed that the flexible Electronic Gearbox proposed by this dissertation has the expected control effect.6. Finally, the flexible Electronic Gearbox control software was applied to the home-made gear machining CNC by the dissertation successfully. Then, the CNC systems were installed on the YS3118CNC5hobbing machine and the YK5132B gear shaping machine, which were produced by Chongqing Machine Tool Works and the Tianjin NO.1Machine Tool Works respectively. The standard testing gears were successfully machined by the two machine tools. Thereinto, the spur gear machined by the hobbing machine can reach precision grade5, the helical gear machined by the hobbing machine can reach precision grade7, and the spur gear machined by the shaping machine can reach precision grade6. The experimental results were fully proved that the proposed flexible Electronic Gearbox was high-precision, reliable and practicable in the actual engineering application.