Papers by Author: Yu Zhu

Abstract: This paper discusses the air spring of the lithography mechanic gravity compensation device and the working principle of pneumatic control structure, and introduces the related technical parameter design. Focus on the structure of vibration damping device design and classical control theory.

Abstract: Based on permanent magnet (PM), lots of redundant position information can be achieved only by using few sensors. The redundant information is used for not only decoupling multi-dimensional displacement, but also reducing the measurement uncertainty. However, it is difficult to decouple the magnetic intensity and multi-dimensional displacement. On this point, this paper builds the measurement system consisting of hall sensors and a cylindrical PM. Secondly, the mathematical model of magnetic intensity and displacement is established with the help of finite element simulation. Thirdly, three-dimensional measurement algorithm is proposed based on the method of symmetry and linearization. The experiment results demonstrate the measurement system has satisfactory performance. In addition, without complex calculation, the system has the advantage of fast measurement.

Abstract: This paper proposed a new configuration of magnetic bearings used in magnetic levitation stages. The equivalent current sheet model is introduced to calculate the levitation force of the proposed magnetic bearing, and the experiment result validates the correctness of the calculation method. The relationships of structural parameters to the levitation force and axial stiffness are studied, which prove that the new magnetic bearing has larger levitation force with lower axial stiffness over the working stroke and could be applied in ultra-precision magnetic levitation stages.

Abstract: High dynamic property is a major object in fine stage design, as well as high stability. To raise structural damping is a feasible and effective method. In this paper, an approach is advanced by choosing parameters of structural damping for fine stage, via analysis of the loss factor of the structure. Through the experimental verification, this method could double the damping ratios, and be applicable to the same structures without changing the original interface.

Abstract: Laser confocal probe, on an active focus adjusting principle, was introduced in this paper. This kind of non-contact laser probe has the abilities to do the detection on strong reflection of the surface of high precision metal parts and optical devices. So, a problem of shape inspection detection was resolved. The micro-sphere is the key element in the ICF (short for inertial confinement fusion) system. The success or failure of "Ignition" is directly related to the accuracy of the assembly location of micro-sphere in the micro-target. Because of the particularity of the micro-sphere, laser confocal probe is used to do the detection of the center error of micro-sphere. The required measurement precision is less than 3µm. The mathematical formula between the height defference or the displacement value of measured surface and the displacement valued of the tuning fork can be gotten by the time different principle. Good stability of frequency and the swing of tuning fork, which approved through the experiments, have little influence to the time different Δt and the final measurement results.

Abstract: In order to improve the radial superresolution of the two-photon microfabrication, the superresolution diffraction theory was introduced in detail. The theoretical analysis of the photosensitive resist based on the exciting power and concentration of free radical was given.. And the superresolution diffractive optical element was applied in the two-photon microfabrication system. Simulation results indicated that the radial superresolution of the two-photon microfabrication can be improved with the superresolution diffractive optical element.