Sponsored by China Instrument and Control Society
ISSN 0254-3087 CN 11-2179/TH
12 issues per year
Discipline(s): Engineering Technology
Current Issue: Issue 10, 2018
Chinese Journal of Scientific Instrument is 2nd in Mechanical Engineering, Top10. Supervised by China Association for Science and Technology. Sponsored by China Instrument and Control Society. Chinese Journal of Scientific Instrument publishes papers with the highest academic level in the field of Chinese instrument and automation, aims to report scientific frontier, research hotspot and research direction, and also supports the creative scientific thought, values the verification of science experiment. Collected by Ei, CA, SA, JST and CSCD.Impact factor is 2.67.
Wang Weiqi, Xu Yunzhong, Wang Xue
Vol 39,No. 10
The high-precision position & navigation & timing service has been offered by Galileo navigation satellite system for more than one year. It is necessary to evaluate the performance of on-board clock during this period. The related evaluation method can be used as the reference for the BDS-3 on-board hydrogen maser. The performance of the on-board hydrogen maser is analyzed since the official service starts. It shows that Hadamard variance is the optimal statistics. Moreover, resampling the clock difference to low-frequency clock difference has no influence on the stability. More days of missing data result in the greater impact on the stability of the on-board clock. It is also verified that the noise type of on-board clock is closely related to the stability of on-board clock.
Vol 39,No. 10
The temperature change may result in the failure of the joint friction compensation and the reduction of tracking precision of the six-axis industrial robot. To solve this problem, a temperature dependent Stribeck friction model is proposed in this paper. The system parameter identification model is achieved by the nonlinear least square method. The Levenberg-Marquardt (L-M) method is utilized to solve the model iteratively. The nonlinear Stribeck friction model under the influence of temperature is obtained. To verify the effectiveness of the model, the trajectory tracking experiment of six-axis industrial robot is designed, and the friction feedforward compensation is introduced. Experimental results show that the improved Stribeck friction model can accurately describe the change law of friction at different temperatures. The friction feedforward compensation based on the model can effectively improve the tracking accuracy of six-axis robot joints.
Vol 39,No. 10
The static characteristics of the target flowmeter, such as linearity, sensitivity and repeatability, are influenced seriously by the vortex signal in the measurement process. To solve this problem, the defects of the traditional target flowmeter model are firstly analyzed. Secondly, the factors affecting the vortex signal of the target flowmeter are studied by computational fluid dynamics (CFD) simulation analysis. Two design parameters of the total pressure of vortex center and the dynamic pressure conversion rate are put forward. The circular target, square target and semi-square structures are compared. To evaluate the proposed method, the calibration experiment of repeated metering performance is designed. Experimental results show that reducing the total pressure of vortex center can improve the linearity and repeatability of the target flowmeter, and the sensitivity of the target flowmeter can be increased by increasing the dynamic pressure conversion rate.
Research on multi-point error calibration and correction of digital moiré phase-shifting interferometer
Vol 39,No. 10
Interferometry has a high measurement accuracy and a wide range of applications in the existing surface inspection methods of optical components. Fabrication and alignment errors in the interferometer reduce the accuracy of surface inspection. A multi-point calibration method of an actual interferometer system using a Shaker-Hartmann wavefront sensor is proposed. The correction of the virtual interferometer system is implemented in the optical design software ZEMAX using wavefront calibration data. Combined with digital moiré phase-shifting algorithm, the influence of the fabrication and alignment errors in the actual interferometer are eliminated. A planar mirror and a deformable mirror are selected as the test mirrors for surface shape measurement experiments. The results show that the measurement accuracy of the digital moiré phase-shifting interferometer system after calibration and correction is improved. Compared with the measurement results of the Zygo interferometer, the surface shapes are consistent and the peak-to-valley (PV) error difference is within 0.07 λ ( λ = 532 nm).
Vol 39,No. 10
To improve the sensitivity of microwave method to detect low carbon content of fly ash, this paper proposes a new method for testing the low carbon content of fly ash under static conditions. The testing frequency range is between 9.84 GHz–15 GHz. The basic principle and test method of the test are described in detail. By using the technology of time domain gates and combining the test results of different ash samples from five power plants in the range of 0%–20% of carbon content, the regular pattern of fly ash’s low carbon content and amplitude attenuation and linear amplitude are obtained respectively. By linear fitting, between the 9.84 GHz–11 GHz frequency band, the fitting degree of the other four factories is more than 0.97 except for the particularity of a factory’s ash sample. In addition, different methods are used to obtain complete test results of high carbon content. Compared with free-space transmission method, test results show that the reflection method can solve the problem of low sensitivity of testing low carbon content.
Morphological feature extraction based on the polar transformation of the slice of ambiguity function main ridge
Vol 39,No. 10
Extracting the intra-pulse feature parameters which can represent the signal intrinsic information is an effective way to sort complex system radar emitter signal. Because ambiguity function can reflect the internal information of signal meticulously, this work presents a morphological feature extraction method based on polar transformation of the slice of ambiguity function main ridge. This method converts the slice of ambiguity function main ridge into a closed geometric image by polar transformation. Then, the average area, density and roundness of the image are extracted as the feature vector of signal sorting. The fuzzy C-means clustering experiment shows that the success rate of sorting for the six typical radar signals is 95.33% in the fixed SNR environment of 0 dB and the success rate is 88.5% even in −2 dB. Besides, the success rate is 99.7% in the dynamic SNR environment of 0–20 dB. The validity of the proposed method is proven. In addition, the time consumption of feature extraction indicates that the proposed method only needs 1.34 s to extract a single signal feature, which has satisfactory timeliness.