Self-calibration method based on circular grating angle measurement error of portable articulated coordinate measuring machine
A technology of coordinate measuring machines and circular gratings, which is applied in the direction of measuring devices and instruments, can solve the problems of measurement environment changes, influences, and time-consuming inter-calibration methods, so as to improve angle measurement accuracy, product reliability, and online measurement The effect of precision
Active Publication Date: 2020-12-04
HEFEI UNIV OF TECH
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However, cross-calibration methods can be very time-consuming as the amount of data increases and are susceptible to changes in the measurement environment
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[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.
[0047] The embodiment is based on the self-calibration method of the circular grating angle measurement error of the portable articulated coordinate measuring machine, that is, the establishment of the circular grating angle measurement error compensation model of the multi-reading head, including the following steps: 1) establishing the reading head H j Angular function model;
[0048] According to the EDA model, there are evenly distributed M reading heads on the surface of the circular grating, and the reading heads H j Relative to reference readhead H 1 The positioning angle value of α j , build the reading head H j Goniometric function model:
[0049] h j (θ)=θ+ε(θ+α j ),
[0050] h j (θ) is affected by the encoder angle measurement error value ε(θ), and the encoder error usually produces a phase...
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The invention discloses a self-calibration method based on circular grating angle measurement error of a portable joint coordinate measuring machine. The method comprise a step of establishing a reading angle Hj angle measuring function model, a step of setting an angular interval of three reading heads of a circular grating angle measuring device and obtaining circular grating angle measurement values of the three reading heads, a step of performing curve fitting on a difference function of two reading heads of the three read heads H1, H2 and H3 and establishing function relations between angle measurement difference values H2-H1, H3-H1 and H3-H2 of two reading heads and an angle position, a step of performing equal angular interval sampling on fitted difference value curves, performing discrete Fourier transform on sampled points and bringing the sample points into a relational expression with a transfer function to obtain a coefficient function F(n) of Fourier series, a step of performing discrete Fourier inverse transformation to obtain a compensation function model epsilon(theta) of the circular grating angle measurement error, and a step of verifying the compensation effect of a circular grating angle measurement error self-calibration model by using a calibration method with the combination of a multi-faceted prism and a self-collimator. Multi-order harmonic error compensation is accomplished with fewer reading heads, and the product reliability is improved.
Description
technical field [0001] The invention belongs to the field of articulated coordinate measuring machines, in particular to a self-calibration method based on the angle measurement error of a circular grating of a portable articulated coordinate measuring machine. Background technique [0002] Portable articulated coordinate measuring machine is a portable non-orthogonal measuring device made by simulating the human arm. It is widely used in mold manufacturing, machining and manufacturing. It has small size, light weight, easy to carry, flexible measurement, and large measurement space. , Strong environmental adaptability and so on. Portable articulated coordinate measuring machines are usually composed of a base, a rotary joint, a measuring arm and a measuring head in series. This structure has the effect of error amplification. Therefore, it is very important to perform precision calibration of angle encoders installed at rotary joints. [0003] The circular grating angle e...
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IPC IPC(8): G01B21/04
CPCG01B21/042
Inventor 于连栋张润刘士达赵会宁贾华坤
Owner HEFEI UNIV OF TECH