Satellite attitude control that utilizing momentum bias and magnetic control is a class of complicated linear quasi-periodic system. According to asymptotical stability theorem of linear time-varying system, a new app...
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ISBN:
(纸本)0780382730
Satellite attitude control that utilizing momentum bias and magnetic control is a class of complicated linear quasi-periodic system. According to asymptotical stability theorem of linear time-varying system, a new approach to magnetic controller design is presented in this paper. Simulation result is given. It is shown that high pointing accuracy of roll/yaw is achieved.
The spectrogram of Doppler ultrasound signal has been widely used in the clinical diagnosis. The additional frequency component arising from noise will produce an adverse effect on the subjective analysis of the spect...
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ISBN:
(纸本)078038248X
The spectrogram of Doppler ultrasound signal has been widely used in the clinical diagnosis. The additional frequency component arising from noise will produce an adverse effect on the subjective analysis of the spectrogram and its quantitative analysis. The methods combining cycle-spinning with thresholding methods using orthogonal wavelet transform and cosine packet decomposition are proposed to remove noise from Doppler ultrasound signal. At first, a specified transform method is performed on the signal of interest. Then the soft or hard thresholding method is used to shrink the coefficients, from which the denoised signal is reconstructed. In the simulation study, the improvements of the mean frequency waveform and the SNR before and after denoising are studied. Simulation results have shown that the methods incorporating with cycle-spinning are superior to those traditional denoising methods. In view of computational complexity and performance improvements, the orthogonal wavelet transform combined with cycle-spinning is a practical approach for denoising Doppler ultrasound signal.
The dry friction in an unstable non-minimum-phase system can cause a self-sustained oscillation. The state feedback design can do nothing with such oscillations. If the non-minimum-phase is stabilized by output feedba...
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ISBN:
(纸本)0780382730
The dry friction in an unstable non-minimum-phase system can cause a self-sustained oscillation. The state feedback design can do nothing with such oscillations. If the non-minimum-phase is stabilized by output feedback, as is well known, an inner fast loop is generally needed to guarantee the robustness. It is pointed out that the friction can be attenuated by the fast loop with additional compensation design. A novel H/sub /spl infin// design methodology is proposed for this two-loop system, in which the dynamics of the inner loop is treated as unmodeled dynamics, while the order of the controller can also be reduced. Such a design is a typical example of applying H/sub /spl infin// controltheory to multi-loop systems.
An approach of designing reduced-order robust controller for active vibration control of a flexible plate structure is presented in this paper. FU-based robust output feedback control law is designed by using specific...
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ISBN:
(纸本)0780387309
An approach of designing reduced-order robust controller for active vibration control of a flexible plate structure is presented in this paper. FU-based robust output feedback control law is designed by using specific transformations of Lyapunov variable with appropriate linearizing transformations of the control variables, which gives rise to a tractable and practical LMI formulation of the vibration control problem. In terms of LMI technique, an H/sub /spl infin// output feedback controller is designed to suppress the low-frequency vibrations caused by external disturbances and to guarantee the stability and performance of the closed-loop system under uncertainties. The order of the controller is further reduced through an iterative two-step LMI-based algorithm for the frequency weighted model reduction problem. The efficiency of the approach is validated by numerical simulation studies of active vibration suppression for the flexible plate.
This paper presents a new approach to fuse the fundamental ultrasonic image and second harmonic ultrasonic image using the wavelet transform. When images are merged in a wavelet space, we can process frequency ranges ...
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ISBN:
(纸本)078038248X
This paper presents a new approach to fuse the fundamental ultrasonic image and second harmonic ultrasonic image using the wavelet transform. When images are merged in a wavelet space, we can process frequency ranges differently. For example, high frequency information from one image can be combine with lower frequency information from another to perform edge enhancement. Wavelet efficiently separates an image into different subspaces that preserve the features of the original images after fusion. Feature classification information can be directly applied to the coarse approximation of the wavelet decomposed image without segmenting the original image. The proposed method reduces artefacts and enables physicians to make better diagnoses, which is robust in processing noisy images.
Edge detection is a fundamental step for ultrasound image analysis. However, it remains to be a difficult problem due to the intrinsic noisy nature of ultrasound images. In this paper, an edge detecting algorithm is p...
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ISBN:
(纸本)078038248X
Edge detection is a fundamental step for ultrasound image analysis. However, it remains to be a difficult problem due to the intrinsic noisy nature of ultrasound images. In this paper, an edge detecting algorithm is proposed, which combines an improved directional median filter and early vision model together. And this improved directional medial filtering method is put forward to reduce the blurring caused by the median filter and to depress the influence of noise caused by the directional median filter. The early vision model has been proved in many literatures to be highly effective for edge detecting, even in a very noisy image. In our way, the simpleness and the speediness of the median filter band the antinoise and texture-sensitive characters of the early vision model together efficiently and the experimental results show that out approach is promising.
Based on the characteristics of superheated steam temperature of a boiler, a new cascade control system is designed. The main regulator adopts multi-model observer control, and the secondary controller adopts weighted...
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ISBN:
(纸本)0780384032
Based on the characteristics of superheated steam temperature of a boiler, a new cascade control system is designed. The main regulator adopts multi-model observer control, and the secondary controller adopts weighted synthesizing proportional control. The system integrates the characteristics of the multi-model control with those of the state variable control with observer, and the state observer has dual functions, providing internal information of the process and acting as the identification model. The result of simulation shows that the control system has powerful robustness with the load changing in large range state variable.
We have developed a neural-network based on fault diagnostic system for diesel engine combustion system. Grounded on the presented evolutionary algorithm, neural networks automatically adjust the network parameters (c...
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ISBN:
(纸本)0780384032
We have developed a neural-network based on fault diagnostic system for diesel engine combustion system. Grounded on the presented evolutionary algorithm, neural networks automatically adjust the network parameters (connection weights and bias terms). Computer simulation experimental results confirm that the proposed method has high diagnostically accuracy.
The spectral analysis of the Doppler ultrasound signal based on the spectrogram has been widely used in medicine for the assessment of blood flow in vessels. The additional frequency components arising from noise prod...
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ISBN:
(纸本)0780384032
The spectral analysis of the Doppler ultrasound signal based on the spectrogram has been widely used in medicine for the assessment of blood flow in vessels. The additional frequency components arising from noise produces an adverse effect on the subjective study of the spectrogram and its quantitative analysis. A novel approach using the adapted local cosine transform, combined with the non-negative garrote thresholding method, is proposed to remove noise from the quadrature Doppler ultrasound signal. At first, the directional information is extracted from the quadrature signal. Then the denoising method based on the adapted local cosine transform is performed on the forward and reverse flow signals, respectively. At last, the estimated signal is reconstructed from the denoised signals using Hilbert transform. In the simulation study, the estimation precision of the mean frequency waveform and the spectral width waveform are studied for the signal after denoising. The simulation results for the simulated Doppler ultrasound signals have shown that this approach is superior to the one based on the wavelet transform, especially under low SNR conditions.
Usually, effects of a system under PID control with considerable time delay are not satisfied. However, model-based predictive control is an advanced control strategy that uses a move optimization method for achieving...
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ISBN:
(纸本)0780386531
Usually, effects of a system under PID control with considerable time delay are not satisfied. However, model-based predictive control is an advanced control strategy that uses a move optimization method for achieving satisfactory closed-loop dynamic responses of complex systems. This paper describes a real time scheme that utilizes DMC algorithm to deal with a large pure time delay in process and adopts nuclear radiation to measure thickness of battery separator. The system has been designed and implemented in one of the battery separator plants of China. And the method of measure and control has wide applicability for similar continuous thin material process.
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