Papers by Author: Jiu Bin Tan

Abstract: This paper aims to provide an assembly method to improve mechanical assembly quality. In order to improve the variation propagation control in rotationally symmetric cylindrical components assembly, the eccentric and tilt errors of a single rotor stage were taken into account using a connective assembly model and the eccentric deviation in a mechanical assembly was minimized by properly selecting component orientations. Compared to the minimum cumulative error, the maximum cumulative error was reduced by 71 percent, and the average cumulative error was reduced by 57 percent in the assembly of three components. This article provides an assembly method through variation propagation control in rotationally symmetric cylindrical components assembly. The method could be extended to rotationally symmetric cylindrical components assembly, for example in the assembly of aero-engine components.

Abstract: Giant magnetostrictive actuator (GMA) are commonly used in active vibration isolation domain for hight frequency response and large output force. GMA has a nonlinear displacement output when disturbed by vibrations. In order to compensate for the nonlinearity and improve the precision of the system, the critical process is the measurement of external disturbances which can be realized with a bridge circuit based on a traditional equivalent circuit model. However, the sensitivity is restricted because of the integral relationship between the force and the open circuit voltage. In this paper, the conception of the dynamic inductance is proposed to optimize the equivalent circuit model that is based on coupled linear magneto-mechanical constitutive equations. Then the measurement for external forces becomes effective with the improvement in the sensitivity through measuring the dynamic inductance. A dynamic simulation is carried out to test the performance of GMA based on the equivalent circuit model. The external dynamic forces can be accurately detected by calculating the impedances in the self-sensing effect of the Terfenol-D.

Abstract: A self-calibration method of coupling error is presented for 3-DOF displacement measurement of a planar moving stage based on two planar gratings. The self-calibration method using Fourier series is developed to extract the periodic systematic errors from the coupling errors. The extracted periodic systematic errors are compensated. Experiments are conducted to validate the validity of the self-calibration method and experimental results indicate that the coupling errors in x and y directions are reduced by 2 and 1.5 times respectively. It can be therefore concluded that the self-calibration method is suitable for the 3-DOF displacement measurement of a planar moving stage to improve the positioning accuracy.

Abstract: A dynamic calibration method based on elliptical standard was put forward to further improve the calibration repeatability of measurement system of form measuring instruments. In this method, the radius difference of the major axis to the minor axis of elliptic contour acts as the standard value to calibrate the measuring system, and a low pass filter is used to filter the roughness, electrical noise and high frequency vibration signal which mixed into measurement data, the elliptic contour feature can be obtained accurately based on the low order harmonic properties. Compared with the traditional calibration method of flick standard, the proposed method ensure the calibration state is well consistent with the normal measuring state of the measuring system. Experimental results indicate that the calibration repeatability with 10nm can be achieved by measuring an elliptical standard. This method has been used in the calibration of measurement system of self-made ultra-precision cylindricity measuring instrument.

Abstract: In order to measure the parallelism of two thin parallel beams in multi-axis interferometers and differential interferometers, the autocollimation principle was used by locating a CCD at the focal plane of collimation lens, the two beams converge on CCD image plane at different points when they are not parallel, and the distance between the two converging points is used to calculate the parallelism of the two beams. To achieve high accuracy and low system error, the CCD defocus and tilt should be strictly controlled according to the accuracy requirement. A centroid algorithm with grey threshold was used to reduce the influence of image noise. A beam-selected structure was designed to let the two beams converge to the CCD image plane in sequence to avoid superposition of beam spots. An experimental setup is built to verify the validity of the method. Experimental results show that the system has a centroid position resolution of 0.05 arcsec and a centroid position stability of 0.4 arcsec. It is therefore concluded that the method can be used to measure parallelism that is more than few arcsecs for two thin beams. Moreover, the measuring accuracy of this method can be improved when higher centroid position stability is achieved.

Abstract: The heterodyne laser interferometer is widely applied in ultra-precision displacement measurement, but its accuracy is seriously restricted by the optical nonlinearity which arises from the optical mixing in the reference and measurement arms. In an ideal heterodyne laser interferometer, the beam from the laser source consists of two orthogonally linear-polarized components with slightly different optical frequencies and the two components can be completely separated by the polarizing optics, one traverses in the reference arm, the other traverses in the measurement arm, both of them are in the form of a pure optical frequency. However, in a real heterodyne laser interferometer, due to the imperfect laser polarization, the optics defect and the misalignment, the two components of the laser beam cant be perfectly separated, therefore both of the reference arm and the measurement arm contain a portion of the two laser components, which leads to an optical mixing in the two arms of the heterodyne interferometer and causes the cyclic nonlinearity of several to tens of nanometers.

Abstract: To improve the measurement accuracy of two-dimensional (2D) precision working stages in the semiconductor manufacturing industry, an error separation and dynamic compensation method based on a planar grating is proposed for a 2D coplanar displacement measurement system. In the system, a planar grating of HEIDENHAIN PP281R is fixed in the center of precision working stage to build coplanar structure and reduce Abbe errors. And the system errors including grating period carved error, temperature effect, vibration effect and mount effect are modeled, calculated and separated. Then the separated errors are dynamically compensated from the corresponding displacement measurement results through data-processing software. Analysis results show that the proposed error separation and dynamic compensation method based on planar grating can improve the measurement accuracy of the coplanar displacement measurement system effectively.

Abstract: A mathematical model of a single degree of freedom air spring vibration isolation system is established. The model analyzes the influence of structural damping in the air spring vibration isolation system based on the traditional model. This paper establishes the relationship between the working pressure p, the volume ratio of n and system vibration transmissibility T under forced vibration. The experimental results are verified on different working pressure. The results showed that working pressure p has little effect on the resonant frequency of the system and the system vibration transmissibility. The smaller the ratio n, the lower the resonant frequency of the system and the system vibration transmissibility. The environmental excitation frequency range must be taken into account in designing.

Abstract: In order to improve the frequency stabilization and the anti-interference ability of two-mode power-balance lasers, the asymmetric thermal structure made up of several thermal transfer layers with different heat transfer coefficient is proposed. Through the heat isolation effect of the middle layer in the structure, the laser has asymmetric thermal responses to electric heater control and air interference. So the anti-interference ability of the system is improved by keeping a low speed in air disturbance while keeping a high speed in thermal stabilization. Several experiments were made with two-mode laser to prove the effectiveness of the proposed method. The experimental results indicate that, frequency stability of the two-mode power-balance laser based on asymmetric thermal structure can be locked in 4.1×10-10 in ordinary lab condition, while it becomes 1.9×10-9 where the air velocity is 1m/s.

Abstract: The possibility of constructing terahertz Fabry-Perot interferometer using metallic meshes with micrometer period and high ratio of linewidth/period is investigated, and the effectivity of traditional equivalent circuit method is verified by FDTD method. Simulation shows that the reflectance and transmittance of this kind of meshes calculated by equivalent circuit method have considerable deviation from those obtained by vector analysis of FDTD, so equivalent circuit method can be used to roughly evaluate the properties of this kind of metallic meshes. By using a metallic mesh with the period of 5 micrometers and the ratio of linewidth/period of 0.8, a finesse larger than 1100 can be achieved while the peak transmittance is still larger than 0.2 for a Fabry-Perot interferometer. It is therefore concluded that a high-quality terahertz Fabry-Perot interferometer can be constructed by using metallic meshes with micrometer period and high ratio of linewidth/period.