Research On Related Theory And Key Technologies Of Achieving 1nm Resolution Motion Of Machine Tool Carriage

Motion resolution in nanometer scale is the important characteristic indicator of ultra-precision machine tool. To achieve the target of 1nm motion resolution, two main technical-research objects, which were the mechanical structures of the carriage and the driving of machine tool, were confirmed by combining with developing feature of ultra-precision machine tool, application of the optimizing design method and on the base of analyzing feasibility under multi-condition of implement. In the research of the mechanical structures of the carriage, to avoid vibration exciting of fluid caused by the geometry error of the guideway, the carriage structure of non-hysteresis and autocoupling was designed; to acquire stable state for the carriage which was suitable for nanometer driving, the causing analyzing, the characteristic identification and suppressing methods of micro-vibration in ultra-precision were studied. In the research of the mechanical structures of the driving, high-resolution driving structure and CNC control technical scheme were proposed and analyzed. Finally, the rationality of the design and the research were verified by experiments, and the target of 1nm motion resolution was achieved.This dissertation has obtained the following innovative results:(1) The architecture environment, which affects the measurement and the implement of nanometer resolution motion, was demonstrated. The feasibility was analyzed; the optimizing routes and the main factors among the multiple affecting factors were confirmed.(2) The carriage structure of non-hysteresis and autocoupling was designed. The microcosmic fractal structure, the principle and characteristic of fluid dynamics and the CFD simulation were demonstrated and analyzed. The principle of vibration exciting of fluid caused by the geometry error of guideway and the solution methods were also demonstrated.(3) The conception of micro-vibration in ultra-precision machine tool was proposed. The causes of the micro-vibration were analyzed from two aspects: the inner fluid in the aerostatic bearing and the outer perturbation of the carriage. The pipe mould of porous bearing was built and three primary elements to suppress the micro-vibration were proposed.(4) The characteristic identification of the micro-vibration was researched by using the methods of frequency spectrum, wavelet transform and nonlinear dynamics. The relationship between the micro-vibration and chaos was confirmed under the research of analyzing power spectrum, Lyapunov exponent, fractal dimension and Kolmogorov entropy. Suppressing methods to the micro-vibration based on chaos control were proposed. (5) The mechanical structure of the high-resolution driving structure was designed and CNC control technical scheme was proposed. The driving structure has two main characters: one was radial levitation-style dominant structure and the other was integrating structure of anisotropic rigidity and vibration-isolate connector between the screw-nut and the carriage. The screw-nut structure, of which the preload can be adjusted, was designed based on roller force analysis under the Hertz theory.(6) The rationality of the design and the research were verified by experiments. The experiments include exciting disturbance to the foundation of the machine tool, measurement method of the carriage rigidity by using power spectrum, phase angle checking between the carriage and its bed, the phase loci and the attractor structures of micro-vibration, diamond cutting effect under the condition of suppressed micro-vibration. The final experiments proved: 1nm resolution motion can be achieved by developed technical scheme, and the system has the ability of 0.28nm motion response.