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2 results about "Systematic error" patented technology
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Systematic errors are biases in measurement which lead to the situation where the mean of many separate measurements differs significantly from the actual value of the measured attribute. All measurements are prone to systematic errors, often of several different types. Sources of systematic error may be imperfect calibration of measurement instruments, changes in the environment which interfere with the measurement process and sometimes imperfect methods of observation can be either zero error or percentage error. For example, consider an experimenter taking a reading of the time period of a pendulum swinging past a fiducial mark: If their stop-watch or timer starts with 1 second on the clock then all of their results will be off by 1 second. If the experimenter repeats this experiment twenty times, then there will be a percentage error in the calculated average of their results; the final result will be slightly larger than the true period. Distance measured by radar will be systematically overestimated if the slight slowing down of the waves in air is not accounted for.
Method and device for calibrating aspheric system error
PendingCN122083855ASimplify the calibration processReduced measurement timeUsing optical meansWavefrontOptical axis
The invention provides an aspheric system error calibration method and device, and relates to the technical field of aspheric system error calibration, and the method comprises the steps: obtaining an alignment error; acquiring a rotational symmetry part of the measured aspheric surface at the first wavefront of the original measurement position and a rotational symmetry part of the measured aspheric surface at the second wavefront after the measured aspheric surface is translated by the preset distance along the optical axis; calculating an error surface according to the rotational symmetry part of the first wavefront, the rotational symmetry part of the second wavefront and the alignment error; fitting the error surface with a pre-constructed rotational symmetry error base, and solving a coefficient of each rotational symmetry error term; according to the coefficient and the rotational symmetry error substrate, reconstructing a rotational symmetry surface shape component of the measured aspheric surface; obtaining a rotational symmetry part of a system error according to the difference between the rotational symmetry part of the first wavefront and the reconstructed rotational symmetry surface shape component; according to the invention, the calibration process is obviously simplified, the measurement time is shortened, and the calibration efficiency is improved.
Owner:SHANGHAI JIANHUI TECHNOLOGY CO LTD
Near field rcs measurement calibration method based on compensation of scattering center topology mismatch
This invention discloses a near-field RCS measurement calibration method based on scattering center topological mismatch compensation. Addressing the systematic error problem introduced by the mismatch between the distributed scattering characteristics of the complex target and the ideal point source calibration body when using traditional metal sphere calibration, a physical model of calibration error incorporating near-field spherical wave effects is established. The method preprocesses data by extracting scattering centers and removing outliers, generates a global initial search point set using feature analysis of the error function sensitivity tensor, and performs local precise optimization using an improved parallel LM algorithm. Finally, it obtains the optimal spatial position parameters of the target that minimize measurement error. This method effectively compensates for RCS amplitude oscillations and phase distortion caused by phase center mismatch, reducing the root mean square error (RMSE) of RCS measurements for complex targets such as ship hulls from approximately 15% to below 5% in the Ka-band, significantly improving the accuracy and reliability of electromagnetic scattering characteristic measurements in the field and anechoic chamber.
Owner:XIDIAN UNIV