Applied Mechanics and Materials Vols. 347-350

Abstract: Packaging-related failure has been recognized as one of the principal root causes of convertor failures, condition monitoring is a cost-effective means of improving convertor reliability by power electronic system operator. In this paper, an approach is presented to monitor failure by identifying the case temperature. Firstly, the case temperature is measured at real-time, the transient curves are built based on the measured data respectively. Then, extracting the slope of case temperature from the transient curve during its operation. It is because that the external characteristic of convertor is the reflection of internal condition, once the slope value of the transient curve is higher than that of the normal condition at the same working point, taking account of the masking effect of measuring accuracy and errors, a conclusion can be get that the convertor condition is abnormal. Finally, experiment has validated the proposed method.

Abstract: The design of a high-sensitivity LED lamp with low standby consumption, sound and light controlled type based on the micro-power consumption characteristic of MK6A12P is presented in this paper. The standby power consumption is less than 0.07W. And the problem of the light sense unit influenced by the change of the supply voltage is solved by the design of double integration detection circuit, thereby, the detection accuracy of brightness is improved. The service life of LED lamp is greatly prolonged with constant current drive. It is proved by the experiment that the LED lamp has the advantages of simple circuit structure, high operation stability and high cost performance.

Abstract: This paper gives a rough review of the intelligent control strategies used in BLDC (Brushless Direct Current) motor controller. The development history of BLDC motor is introduced firstly. The parameter setting problems in a traditional PID control method are analyzed secondly. Then, an intensive introduction on the intelligent control strategies those are used in the PID control system is presented. Finally, the development trend of the intelligent control strategies in the BLDC motor control is discussed.

Abstract: This paper is focused on a millimeter-wave detector system that works at self-heterodyne mode. The detector antenna and MMW front-end are integrated and a weak heterodyne signal is amplified with a low-noise amplifier. After high-speed sampled with a high-speed A/D, digital signal are processed in a FPGA. Some experiment results are shown finally.

Abstract: In view of the defects of the traditional damage identification method based on vibration,the damage identification method based on vibration transmissibility is put forward. The feasibility of the vibration transmissibility applied to structural damage identification is analyzed by the numerical simulation experiment of a cantilever beam, the analysis results show that, vibration transmissibility contains the structure damage severity, damage location and other useful information, and all the information is favor of the damage identification.

Abstract: According to the critical issue of accurate measurement of small resistance in the field of electronic measurement, the micro-ohm resistance measurement system is designed based on LabVIEW. It consists of two parts: hardware and software. The hardware is composed of AC constant current source, reference signal source, low noise amplifier, data acquisition card, computer etc.; The software consists of man-machine interface program, measure and control program and data processing program. The system based on virtual instrument cross-correlation detection technology achieves the effective measurement of micro-ohm resistance. It is an automatic measuring system with a flexible and convenient programming, simple and accurate measurement, high resolution and stable performance.

Abstract: Vibration signal was a carrier of fault features of the wind turbine transmission system, it can reflect most of the fault information of the wind turbine transmission system. According to the frequency domain features of the roller bearing fault, wavelet packet transform for feature extraction was proposed as the characteristics of wind turbines in the presence of a large number of transient and non-stationary signals. The characteristics of wavelet packet was analyzed, combined with the wind turbines in the rolling bearing fault characteristic vibration extraction methods, the rolling bearing fault diagnosis was realized through the wavelet packet decomposition and reconstruction, the procedure was given. The simulation result shows that this application can reflect relationship of the failure characteristics and frequency domain feature vectors, also the nonlinear mapping ability of neural networks was played and the fault diagnosis capability enhanced.

Abstract: For the nonlinear coupling characteristics between three axes of the three-axis turntable, a method which combines the inverse system method and Neural Network (NN) has been put forward. This method realizes linearization and decoupling of three-axis turntable and solves the defect of difficult to realize precise decoupling with inverse system method when the model of three-axis turntable is inaccurate. Simulation results show the feasibility of the method and also good robustness and resistance.

Abstract: Digital image watermarking algorithm based on contourlet transform and discrete cosine transform (DCT) is proposed in this paper. The original carrier image is decomposed with contourlet transform. The low pass component is divided into sub blocks. The watermark bits are embedded by the quantization of direct current (DC) coefficients of these sub blocks. In order to against rotation attack, the radon transform is used to project the image onto projection space to convert the rotation of the original image to a translation of the projection and then the bi-spectrum analysis approach is applied to estimate the rotate angle of the test image. The detection process is robust to rotation attack by virtue of this rotation correction method.

Abstract: Accelerated life test was an important means to obtain storage reliability index of missile-borne photoelectric system. Because of difficulty to continuously test, the number of failure samples in the test range could be only got. Whether distribution intervals, logarithmic distribution or new failure time estimation method proposed in this paper such as range median distribution and the uniform distribution of the index had their applicable limitations. On the basis of comparison to Monte Carlo numerical simulation method, the characteristics of the applicability of the estimation method based on Weibull distribution were explored.