Several closed-loop control methods have dealt with clock steering problems, but parameters for these methods are not easy to choose. In this paper, we propose a new clock steering method, which uses a second-order type-2 digital phase-locked loop (DPLL) equivalent to a two-state Kalman filter with a delay. We derive the approximate expressions of the steady-state Kalman gains, which are equivalent to the DPLL gains. Then, we derive the transfer functions of the approximate DPLL. A brief and effective approach to choosing a parameter is also proposed. Simulation results show that the performance of the time steering error and the frequency stability is quite desirable, and can meet the requirements of generating a local representation of coordinated universal time or a global navigation satellite system time.
IndexTerms-Clock steering, digital phase-locked loop (DPLL), frequency stability, Kalman filter, steering error.
Architecture modeling, simulation, and test verification are performed to meet the requirements of multi-domain modeling and simulation of tractor power shift transmission (PST). The principles of architecture modeling and high level architecture (HLA) are analyzed, and the PST architecture modeling connotation and simulation system structure are studied. Then the dynamic principles of PST mechanical, hydraulic and control subsystems are analyzed in the preparation phase, sliding friction phase and holding phase of clutch engagement. To build the PST system simulation model, the simulation models and components of the three subsystems are established, and the object and interaction classes of the simulation object model (SOM) for each component are defined. After that, the parameter mapping relationship between the components is analyzed, the interfaces between the simulation components and HLA are encapsulated, and the simulation component running sequence is analyzed. Finally, the PST clutch engagement law under tractor shift conditions is simulated and tested. The relative error and correlation coefficient between the simulated and test data of shift solenoid valve drive current are used as indexes to evaluate the PST system simulation model. The results show that the simulated drive current curves are consistent with the test ones. The maximum error between the simulated and test shift time appears at the third gear downshift point, with a value of 7.89%, and the minimum correlation coefficient value between the simulated and the test drive current at all shift points is 0.92, which indicate that the PST system simulation model is effective and accurate.
INDEX TERMSArchitecture modeling, high level architecture (HLA), power shift transmission (PST), test verification, tractor
Gray level co-occurrence matrix (GLCM) is an important method to extract the image texture features of synthetic aperture radar (SAR). However, GLCM can only extract the textures under single scale and single direction. A kind of texture feature extraction method combining nonsubsampled contour transformation (NSCT) and GLCM is proposed, so as to achieve the extraction of texture features under multi-scale and multi-direction. We firstly conducted multi-scale and multi-direction decomposition on the SAR images with NSCT, secondly extracted the symbiosis amount with GLCM from the obtained sub-band images, then conducted the correlation analysis for the extracted symbiosis amount to remove the redundant characteristic quantity; and combined it with the gray features to constitute the multi-feature vector. Finally, we made full use of the advantages of the support vector machine in the aspects of small sample database and generalization ability, and completed the division of multifeature vector space by SVM so as to achieve the SAR image segmentation. The results of the experiment showed that the segmentation accuracy rate could be improved and good edge retention effect could be obtained through using the GLCM texture extraction method based on NSCT domain and multi-feature fusion in the SAR image segmentation.
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