An accurate technique for measuring the frequency response of semiconductor laser diode chips is proposed and experimentally demonstrated.The effects of test jig parasites can be completely removed in the measurement ...An accurate technique for measuring the frequency response of semiconductor laser diode chips is proposed and experimentally demonstrated.The effects of test jig parasites can be completely removed in the measurement by a new calibration method.In theory,the measuring range of the measurement system is only determined by the measuring range of the instruments network analyzer and photo detector.Diodes' bandwidth of 7 5GHz and 10GHz is measured.The results reveal that the method is feasible and comparing with other method,it is more precise and easier to use.展开更多
In this paper,a bandwidth-adjustable extended state observer(ABESO)is proposed for the systems with measurement noise.It is known that increasing the bandwidth of the observer improves the tracking speed but tolerates...In this paper,a bandwidth-adjustable extended state observer(ABESO)is proposed for the systems with measurement noise.It is known that increasing the bandwidth of the observer improves the tracking speed but tolerates noise,which conflicts with observation accuracy.Therefore,we introduce a bandwidth scaling factor such that ABESO is formulated to a 2-degree-of-freedom system.The observer gain is determined and the bandwidth scaling factor adjusts the bandwidth according to the tracking error.When the tracking error decreases,the bandwidth decreases to suppress the noise,otherwise the bandwidth does not change.It is proven that the error dynamics are bounded and converge in finite time.The relationship between the upper bound of the estimation error and the scaling factor is given.When the scaling factor is less than 1,the ABESO has higher estimation accuracy than the linear extended state observer(LESO).Simulations of an uncertain nonlinear system with compound disturbances show that the proposed ABESO can successfully estimate the total disturbance in noisy environments.The mean error of total disturbance of ABESO is 15.28% lower than that of LESO.展开更多
Influences of the clock resolution of bandwidth estimator on the accuracy and stability of the packet pair algorithm was analyzed.A mathematic model has been established to reveal the relationship between the result d...Influences of the clock resolution of bandwidth estimator on the accuracy and stability of the packet pair algorithm was analyzed.A mathematic model has been established to reveal the relationship between the result deviation coefficient and the packet size,clock resolution and real bandwidth(value)of the measured route.A bandwidth self-adapting packet pair algorithm was presented based on the mathematic model to reduce the estimation error resulting from the clock resolution and to improve the accuracy and stability of measurement by adjusting the deviation coefficient.Experimental results have verified the validity and stability of the algorithm.展开更多
A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving th...A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving the ambiguity problem, a more reliable result is achieved by using weighted average of measurement results from three different wavelengths, where the weight is dependent upon spacing. Fringe-bunching correction algorithm （FBC） and spot-tilling technique are adopted to suppress calibration and random errors. Moreover, incident bandwidth correction （IBC） method is introduced to compensate the error caused by low monochromaticity of incident light. Based on dynamic flying height tester （DFHT Ⅱ）, with the redesigned of photo-electric conversion and signal acquirement module, an instrument has been developed. And comparing the experimental data from the instrument with those from a KLA-FHT D6, the discrepancy is less than 5%. It indicates that the instrument is suitable to perform ultra-low flying height measurement and satisfies the reauirement of magnetic heads manufacturing.展开更多
Nowadays, PD （partial discharge） measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the u...Nowadays, PD （partial discharge） measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the user are interested in the results of PD measurements. However, PDs hardly represent the cause of the failure, more likely they are claimed as the outcome of a failure. This paper deals with the insulation of a 6 kV electrical machine, whereas PD measurements were carried out at a single stator from wound coils. During manufacturing, these coils were equipped with different materials for the OCP （outer corona protection）. Using different PD measurement systems and different bandwidths, investigations of the PD behavior of the coils were carried out. Additionally, the surface resistivity of the corona protection was determined. As a result, conclusions for the correlations between the resistance of the OCP as well as the PD behavior are stated. Furthermore, the influence of using different measurement systems, different measuring circuits, and different bandwidths is shown.展开更多
文摘An accurate technique for measuring the frequency response of semiconductor laser diode chips is proposed and experimentally demonstrated.The effects of test jig parasites can be completely removed in the measurement by a new calibration method.In theory,the measuring range of the measurement system is only determined by the measuring range of the instruments network analyzer and photo detector.Diodes' bandwidth of 7 5GHz and 10GHz is measured.The results reveal that the method is feasible and comparing with other method,it is more precise and easier to use.
基金supported by the National Natural Science Foundation of China(61873126)。
文摘In this paper,a bandwidth-adjustable extended state observer(ABESO)is proposed for the systems with measurement noise.It is known that increasing the bandwidth of the observer improves the tracking speed but tolerates noise,which conflicts with observation accuracy.Therefore,we introduce a bandwidth scaling factor such that ABESO is formulated to a 2-degree-of-freedom system.The observer gain is determined and the bandwidth scaling factor adjusts the bandwidth according to the tracking error.When the tracking error decreases,the bandwidth decreases to suppress the noise,otherwise the bandwidth does not change.It is proven that the error dynamics are bounded and converge in finite time.The relationship between the upper bound of the estimation error and the scaling factor is given.When the scaling factor is less than 1,the ABESO has higher estimation accuracy than the linear extended state observer(LESO).Simulations of an uncertain nonlinear system with compound disturbances show that the proposed ABESO can successfully estimate the total disturbance in noisy environments.The mean error of total disturbance of ABESO is 15.28% lower than that of LESO.
基金This workis supported by973Project(National Keystone Foundation Research Project,No.G199903271)the National Natural Science Foundation of China(No.90104022)the National High Technology Development Program of China(No.2001AA112120,No.2002AA104550).
文摘Influences of the clock resolution of bandwidth estimator on the accuracy and stability of the packet pair algorithm was analyzed.A mathematic model has been established to reveal the relationship between the result deviation coefficient and the packet size,clock resolution and real bandwidth(value)of the measured route.A bandwidth self-adapting packet pair algorithm was presented based on the mathematic model to reduce the estimation error resulting from the clock resolution and to improve the accuracy and stability of measurement by adjusting the deviation coefficient.Experimental results have verified the validity and stability of the algorithm.
基金National Basic Research Program of China(973 Program,No. 2003CB716207)National Natural Science Foundation of China(No.50775091)
文摘A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving the ambiguity problem, a more reliable result is achieved by using weighted average of measurement results from three different wavelengths, where the weight is dependent upon spacing. Fringe-bunching correction algorithm （FBC） and spot-tilling technique are adopted to suppress calibration and random errors. Moreover, incident bandwidth correction （IBC） method is introduced to compensate the error caused by low monochromaticity of incident light. Based on dynamic flying height tester （DFHT Ⅱ）, with the redesigned of photo-electric conversion and signal acquirement module, an instrument has been developed. And comparing the experimental data from the instrument with those from a KLA-FHT D6, the discrepancy is less than 5%. It indicates that the instrument is suitable to perform ultra-low flying height measurement and satisfies the reauirement of magnetic heads manufacturing.
文摘Nowadays, PD （partial discharge） measurements are a crucial part of the preventive maintenance of electrical equipment within high voltage engineering. Especially for electrical machines, both the supplier and the user are interested in the results of PD measurements. However, PDs hardly represent the cause of the failure, more likely they are claimed as the outcome of a failure. This paper deals with the insulation of a 6 kV electrical machine, whereas PD measurements were carried out at a single stator from wound coils. During manufacturing, these coils were equipped with different materials for the OCP （outer corona protection）. Using different PD measurement systems and different bandwidths, investigations of the PD behavior of the coils were carried out. Additionally, the surface resistivity of the corona protection was determined. As a result, conclusions for the correlations between the resistance of the OCP as well as the PD behavior are stated. Furthermore, the influence of using different measurement systems, different measuring circuits, and different bandwidths is shown.
