Study On Optimization Of Dynamics Characteristics Of An Ultra-precision Positioning Stage With Gas-lubricated Bearings

An ultra-precision positioning stage is a new type of precision motion mechanism, which is based on gas-lubricated bearing and linear motor driving. The stage can overcome the shortages result from the traditional positioning stage, such as more transmissions, bigger lag of response and existed nonlinear friction between moving parts and static ones. The stage can achieve the nanometer positioning accuracy and rapid moving, and has been widely used in semiconductor lithography, precision measurement and biomedical field. When the positioning accuracy approaches the tradition manufacturing limits, to meet with the more stability and faster response of the sateg have some difficulty. The factors, for example the stiffnesses of the gas-lubricated bearings, the location of the bearings and the configuration of stage, can influence the dynamics characteristic of the stage, obviously. The factors how to affect the dynamics characteristic of the stage is studied in the dissertation and carried out into optimization correspondingly. The performance has been applied in the development of 100 nm lithography successfully.The structural dynamics and the finite element method are used to study the stiffness how to affect the dynamics characteristic of the stage. The stiffnesses are modified in the digital model. Natural frequencies and generalized stiffnesses of the stage are obtained by the calculation. The relationship between the supporting stiffness and the natural frequencies of the stage is obtained by least square method. The optimization methods of the stiffness accounting for the gas-lubricated bearing are obtained through the sensitivity analysis.The partial grid mobile technology is put forward in the study firstly, and successed in applying the gas-lubricated bearing position optimization. When the air-bearings are installed in different positions, the maximal ratio between the optimal and worst position in the first 5 order natural frequencies is 6.0961, 5.4736, 1.9246, 1.6210, 1.0917 and 1.2972. And the response amplitude is changed manifestly, for example the maximal ratio is about 10 times in typical positions.The drive arm is the key component of the ultra-precision positioning stage. The topology optimization technology is used to solve the design of the drive arm. The perfect design is proposed through the optimization. The drive arm design problem is solved.Based on the results from the above research of the ultra-precision positioning stage with gas-lubricated bearings, the experimental modal analysis is conducted on the stage. When the bearing is on the given position and the stiffnesses of the bearings are equal to 70 N/μm, the maximal relative error is 3.24% compared with the results from the experiment and the finite element analysis. Regulated the supply pressure of the gas-lubricated bearings, the dynamics characteristic of the stage is changed. Compared with the results from the experimental model analysis and the finite element analysis under the different supply pressure or the stiffness, the results are in agreement with the experimental model analysis and the finite element analysis..