The maglev vibration isolation system exhibits excellent micro-vibration isolation performance (0.01 Hz to 100 Hz band) in the space environment. However, a collision between the base and the floating platform may occur in an ultra-low frequency range (≤0.01 Hz). To avoid collision, the relative position and attitude between the base and the floating platform needs to be accurately tracked and controlled. In this study, a novel measurement method with four groups of two-dimensional position-sensitive detectors equipped with four laser light sources was proposed. A high-precision relative position and attitude measurement model was established based on the geometric relationship of space coordinates. A proportional-differential (PD) fixed-point control algorithm was adopted to realize tracking control. The control performance of the system was evaluated through simulation. Experiments were also carried out to verify the stability of the system and the precision of the control algorithm. A maglev vibration isolation system prototype was constructed and a test system was established. The proposed relative position and attitude measurement model was verified and the six degrees of freedom relative position and attitude response of the system was tested. Based on the measurement model, the tracking control of the system was proven to have high precision.

Tracking Control of a Maglev Vibration Isolation System Based on a High-Precision Relative Position and Attitude Model

In the long-term forecast for the investment demand of power grid, the error of independent variable will result in a large error between forecast result and actual result. In this paper, the correction parameters of factors which have an influence on investment demand of power grid is introduced and the correction model of long-term forecast is built. Firstly, through the correlation analysis and the principle comment analysis (PCA), the variables which the model needs are selected. Secondly, the long-term forecast model based on linear regression is built and the variable coefficient is calculated through least square method. Thirdly, after analyzing historical data of forecast value and actual value, correction model of long-term forecast is built through introducing correction parameters of each variables. Finally, compared with the calculation results which get from correction model and the long-term forecast model, it is proved that the error of correction model is smaller.

https://www.dpi-proceedings.com/index.php/dteees/article/download/34020/32607

A Long-Term Forecast Method for the Investment Demand of Power Grid Based on Linear Regression and Error Correction of Variable

The New Robotic Telescope (NRT) is a robotic and fully autonomous four-metre-class telescope and the first in its size class to utilise a clamshell enclosure. It will be located at the Roque de los Muchachos Observatory (ORM) on La Palma, Canary Islands, Spain. Fast slew time, robotic functionality, and reduced dome seeing are the main reasons for the clamshell design, however cost is also an important factor. The greatest opportunity for cost reduction is the movable roof structure of the enclosure, but is the most complex to design and the heaviest part in the initial concept considerations. To solve a complex optimisation problem considering all limitations, conditions and assemblies, a combination of generative design approach and machine learning is used. This enables us to overcome two major obstacles: First, we are able to combine multiple models into one optimisation problem that could analyse multiple states simultaneously, such as the closed and semi-open states. Second, the machine learning-based predictive models are able to run much faster, which allows us to explore many more possible design solutions. Structural optimisation results show more than one optimal solution, which is consistent with multi-objective optimisation, since there are certain trade-offs between mass, capacity utilisation, and hydraulic forces. The goal of the structural optimisation was to explore the possible design alternatives before engaging a construction design partner. This allows for more efficient project development, as the design partner could immediately focus on the construction design work without needing to understand the implications for the telescope.

New Robotic Telescope enclosure concept selection and optimisation

Scanning mirrors appear to be key components in optoelectronic systems for line-of-sight (LOS) stabilization. For improving the angular accuracy of a scanning mirror based on the eddy current displacement sensor measurement, an angular error-correction method is proposed and demonstrated. A mathematic angular error model with physical parameters was developed, and the cross-validation method was employed to determine the reasonable order of the Maclaurin series used in the error model, which increased the exactitude and robustness of the correction method. The error parameters were identified by accurately fitting the calibrated angular errors with the error model, which showed excellent error prediction performance. Based on the angular calculation model corrected by the error model, the closed-loop control system was established to obtain accurate deflection angles. Experimental results show that within the deflection angle of ±1.5 deg, the angular accuracy was improved from 0.28 deg to less than 1.1 arcsec, and the standard deviation for six measurements was less than 1.2 arcsec, which indicates that the angle correction method was effective in improving the linearity of the eddy current sensors and reducing the influence of manufacturing and installation errors.

https://www.mdpi.com/1424-8220/19/2/367/pdf

Improving Angular Accuracy of a Scanning Mirror Based on Error Modeling and Correction.

Dome seeing degrades the image quality of ground-based telescopes. To achieve dome seeing of the Four Meter Telescope (FMT) less than 0.5 arcsec, structural optimizations based on computational fluid dynamics (CFD) simulation were proposed. The results of the simulation showed that dome seeing of FMT was 0.42 arcsec, which was mainly caused by the slope angle of the dome when the slope angle was 15° and the wind speed was 10 m/s. Furthermore, the lower the air speed was, the less dome seeing would be. Wind tunnel tests (WT) with a 1:120 scaled model of the retractable dome and FMT indicated that the calculated deviations of the CFD simulation used in this paper were less than 20% and the same variations of the refractive index derived from the WT would be a convincing argument for the validity of the simulations. Thus, the optimization of the retractable dome was reliable and the method expressed in this paper provided a reference for the design of next generation of ground-based telescope dome.

https://iopscience.iop.org/article/10.1088/1538-3873/aa56b8/pdf

Yue Fan

Papers

Improving Angular Accuracy of a Scanning Mirror Based on Error Modeling and Correction.

Structural Optimization of the Retractable Dome for Four Meter Telescope (FMT)

A fast radar target recognition based on single Gaussian background model