Showing papers by "Jinchun Hu published in 2018"

A Hall Sensor-Based Position Measurement With On-Line Model Parameters Computation for Permanent Magnet Synchronous Linear Motor

Abstract: With the advantage of low cost and small size, a hall sensor has been exploited to detect motor position, and this strategy has attracted much attention. A challenge is that measurement model parameters vary with position and vary from motor to motor because of the machining errors of permanent magnets. While, most existing methods use other auxiliary displacement sensors to calibrate model parameters off-line, which require a lot of preliminary work and lose adaptation when they are applied in industry. In this paper, an on-line simultaneous computation of model parameters and position method is proposed to measure position for a permanent magnet synchronous linear motor. The measurement model with Fourier series is employed to approximate the mapping relationship between magnetic field strength and mover position. Based on the continuous variation characteristics of model parameters and position, a simultaneous computational algorithm is proposed to real-timely compute model parameters and position without other sensors. In the experiments of one-way and reciprocating motion, magnetic field information is detected by a self-designed hall sensor array. Experimental results indicate that the standard deviation of measurement error is less than $10~\mu \text{m}$ with the comparison of a reference optical encoder.

Translational displacement computational algorithm of the grating interferometer without geometric error for the wafer stage in a photolithography scanner

Abstract: The translational displacement computational algorithm base on a novel phase-shift model is proposed eliminating the geometric error of the grating interferometer for precision positioning of a multi-degree-of-freedom motion stage. Firstly, the mechanism of the geometric error of the grating interferometer is analyzed, and the novel phase-shift model of the grating interferometer is constructed based on rigid body kinematics and affine geometry transformation. High accuracy of the model is demonstrated by ZEMAX simulation. Then, according to Taylor series expansion, the phase-shift model is simplified by polynomial regression to solve the problems of a large amount of computational effort and inability to derive the translational displacement computational algorithm. The availability and accuracy of the translational displacement computational algorithm are verified by ZEMAX simulation and experiment.

Five-degree of freedom heterodyne grating interferometry system

Abstract: The invention provides a five-degree of freedom heterodyne grating interferometry system, which comprises a single-frequency laser, an interferometer mirror group, a measurement grating and multiple optical fiber beams, wherein the single-frequency laser is used for emitting single-frequency laser, and the single-frequency laser can be divided to a beam of reference light and a beam of measurementlight; the interferometer mirror group and the measurement grating are used for forming reference interference signals and measurement interference signals from the reference light and the measurement light; and the multiple optical fiber beams receive measurement interference signals and reference interference signals respectively, and multiple multimode optical fibers exist in each optical fiber beam for receiving interference signals of different positions on the same plane. The measurement system of the invention has the advantages of being insensitive to the environment, small in size, light in weight, convenient to arrange and the like; multiple five-degree of freedom interferometry systems are adopted for arrangement, the redundant information is used to realize six-degree of freedom ultra precision measurement, and six-degree of freedom position and attitude measurement requirements of a lithography machine workpiece stage and the like are met.

Installation deviation calibration method for interferometer in multi-axis laser displacement measurement system

Abstract: An installation deviation calibration method for an interferometer in a multi-axis laser displacement measurement system, comprising: adding one or more redundant interferometers (4) in a laser interferometer displacement measurement system; then establishing displacement calculating equations containing installation deviation of the laser interferometer and obtaining redundant measurement information by continuously measuring displacement information of multiple position points, wherein the number of the combined displacement calculating equations is equal to an unknown quantity; and further solving the equation set to obtain the installation deviation of the interferometer. By adopting a redundant arrangement of the laser interferometer, self-calibration of the installation deviation thereof can be realized. The problem of difficult calibration of the installation deviation of the multi-axis interferometer in industrial application can be solved without assistance of other displacement sensors with higher precision.

A Starting Value Computation Method for Displacement Measurement Based on Magnetic Field

Abstract: Displacement measurement based on magnetic field has been exploited in motors and robots, however its measurement error is seriously affected by the measurement model accuracy. We have proposed a simultaneous computation of model parameters and displacement approach to improve measurement accuracy. While, in this approach, a starting value is needed at the initial measurement moment because of its iterative computation form. Traditional computation methods for starting value have a small convergence range or singularity problems, which limit their application. In this paper, a computational method, multi-parameter numerical continuous with wide convergence range, is presented for calculating starting value. This method combines the characteristics of traditional homotopy continuous and displacement measurement. Multiple parameters are introduced to form new homotopy equations. And then, the homotopy equations are solved according to the character of displacement solution. The simulation results verify that it has better convergence performance than tradition homotopy continuous method. Experimental results illustrate that the proposed method can compute a reasonable starting value for displacement solution to realize precision measurement based on magnetic field.