Grating-based precision measurement system for five-dimensional measurement

Qiang, 吕 强 Lv; Wei, 王玮 Wang; Zhao-wu, 刘兆武 Liu; Ying, 宋莹 Song; Shan, 姜珊 Jiang; Lin, 刘 林 Liu; Bayanheshig, 巴音贺希格; Wenhao, 李文昊 Li

doi:10.3788/co.20201301.0189

Cited by 3 publications

(1 citation statement)

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“…Lv et al [ 30 ] proposed a grating interferometer which based its design concept on the Littrow optical configuration, 2-DOF in-plane and out-of-plane displacements can be achieved with the resolution and repeatability of 0.27 nm and 2 nm, respectively. By adopting a similar design concept with two position sensitive detectors, the method proposed by Qiang et al [ 31 ] is able to provide the information of 2-DOF in-plane and out-of-plane displacements and 3-DOF rotations with the resolutions of 4 nm and 0.2”, respectively. However, none of the grating interferometers mentioned above are able to provide simultaneous 2-DOF in-plane displacement information unless a 2D grating or a pair of orthogonal 1D gratings are used in the system.…”

Section: Performance Tests and Discussionmentioning

confidence: 99%

Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Hsieh

Sun

2021

Sensors

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In this study, a compound speckle interferometer for measuring three-degree-of-freedom (3-DOF) displacement is proposed. The system, which combines heterodyne interferometry, speckle interferometry and beam splitting techniques, can perform precision 3-DOF displacement measurements, while still having the advantages of high resolution and a relatively simple configuration. The incorporation of speckle interferometry allows for non-contact displacement measurements by detecting the phase of the speckle interference pattern formed from the convergence of laser beams on the measured rough surface. Experiments were conducted to verify the measurement capabilities of the system, and the results show that the proposed system has excellent measurement capabilities suitable for future real-world applications.

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Section: Performance Tests and Discussionmentioning

confidence: 99%

Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Hsieh

Sun

2021

Sensors

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Space-to-plane decoupling method for six-degree-of-freedom motion measurements

Zhang¹,

Cai²,

Liu³

et al. 2021

Meas. Sci. Technol.

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The advantages of the Stewart platform in bearing capacity, dynamic response, structural rigidity, and stability make it widely used in many fields, such as motion simulators, parallel machine tools, assembly docking. In order to ensure that the spatial positioning accuracy of the Stewart platform to meet the application requirements in various fields, it is necessary to measure its pose in real time. However, the six degrees of freedom are highly coupled, it is difficult to obtain reliable six-degree-of-freedom information through mathematical decoupling. In this study, a machine vision measurement method based on physical decoupling is proposed. The spatial motion measurement of the Stewart platform is mapped to the plane motion measurement by three feature points through the laser pointer and the rear-projection screen. It realizes the dimension reduction equivalently, and simplifies the mathematical model. A lot of experimental analyses show that the proposed method can reliably achieve high-precision real-time measurement of six-degree-of-freedom, which has the accuracy of 0.21 mm (displacement) and 0.045° (rotation) at frequency between 0.1 and 1 Hz. In addition, the space-to-plane decoupling method provides a new way to implement the traceability of the six-degree-of-freedom spatial motion measurement.

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An FPGA Platform for Next-Generation Grating Encoders

Han

et al. 2020

Sensors

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Among various nanometer-level displacement measurement methods, grating interferometry-based linear encoders are widely used due to their high robustness, relatively low cost, and compactness. One trend of grating encoders is multi-axis measurement capability for simultaneous precision positioning and small order error motion measurement. However, due to both lack of suitable hardware data processing platform and of a real-time displacement calculation system, meeting the requirements of real-time data processing while maintaining the nanometer order resolutions on all these axes is a challenge. To solve above-mentioned problem, in this paper we introduce a design and experimental validation of a field programmable gate array (FPGA)-cored real-time data processing platform for grating encoders. This platform includes the following functions. First, a front-end photodetector and I/V conversion analog circuit are used to realize basic analog signal filtering, while an eight-channel parallel, 16-bit precision, 200 kSPS maximum acquisition rate Analog-to-digital (ADC) is used to obtain digital signals that are easy to process. Then, an FPGA-based digital signal processing platform is implemented, which can calculate the displacement values corresponding to the phase subdivision signals in parallel and in real time at high speed. Finally, the displacement result is transferred by USB2.0 to the PC in real time through an Universal Asynchronous Receiver/Transmitter (UART) serial port to form a complete real-time displacement calculation system. The experimental results show that the system achieves real-time data processing and displacement result display while meeting the high accuracy of traditional offline data solution methods, which demonstrates the industrial potential and practicality of our absolute two-dimensional grating scale displacement measurement system.

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Grating-based precision measurement system for five-dimensional measurement

Cited by 3 publications

References 0 publications

Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Development of a Compound Speckle Interferometer for Precision Three-Degree-of-Freedom Displacement Measurement

Space-to-plane decoupling method for six-degree-of-freedom motion measurements

An FPGA Platform for Next-Generation Grating Encoders

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