It is proposed a digital signal processing （DSP） controller used in the control system of six degree-of-freedom （DOF） giant magnetostrictive smart structure （GMSS）. Also are presented the controller design and i...It is proposed a digital signal processing （DSP） controller used in the control system of six degree-of-freedom （DOF） giant magnetostrictive smart structure （GMSS）. Also are presented the controller design and its implementation, the embedded adaptive least mean-square （LMS） control algorithm and the real-time experiments of GMSS. Three programs are embedded in this controller. Of them are the adaptive LMS control algorithm and the other two which are used to search for the optimal values for the initial weight vectors. Moreover, the work flow and the control approach of the GMSS with the DSP controller are introduced. The experimental results indicate that the DSP controller has better control precision and real-time property, and the damping effect is up to 20 dB-30 dB.展开更多
Today’s challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field（IMF） conditions. Correlative studies between ge...Today’s challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field（IMF） conditions. Correlative studies between geomagnetic storms（GMSs）and the various interplanetary（IP） field/plasma parameters have been performed to search for the causes of geomagnetic activity and develop models for predicting the occurrence of GMSs, which are important for space weather predictions. We find a possible relation between GMSs and solar wind and IMF parameters in three different situations and also derived the linear relation for all parameters in three situations.On the basis of the present statistical study, we develop an empirical model. With the help of this model, we can predict all categories of GMSs. This model is based on the following fact： the total IMF Btotalcan be used to trigger an alarm for GMSs, when sudden changes in total magnetic field Btotaloccur. This is the first alarm condition for a storm’s arrival. It is observed in the present study that the southward Bzcomponent of the IMF is an important factor for describing GMSs. A result of the paper is that the magnitude of Bzis maximum neither during the initial phase（at the instant of the IP shock） nor during the main phase（at the instant of Disturbance storm time（Dst） minimum）. It is seen in this study that there is a time delay between the maximum value of southward Bzand the Dst minimum, and this time delay can be used in the prediction of the intensity of a magnetic storm two-three hours before the main phase of a GMS. A linear relation has been derived between the maximum value of the southward component of Bzand the Dst, which is Dst =（-0.06） ＋（7.65）Bz＋ t.Some auxiliary conditions should be fulfilled with this, for example the speed of the solar wind should, on average, be 350 km s-1 to 750 km s-1, plasma β should be low and, most importantly, plasma temperature should be low for intense storms. If the plasma temperature is less than 0.5 × 106 K then the Dst value will be greater than the predicted value of Dst or if temperature is greater than 0.5 × 106 K then the Dst value will be less（some nT）.展开更多
基金National Natural Science Foundation of China for Key Project (60534020)Key Subject Foundation of Beijing (XK100060526)National 973 Research Program (G2002cb312205-02)
文摘It is proposed a digital signal processing （DSP） controller used in the control system of six degree-of-freedom （DOF） giant magnetostrictive smart structure （GMSS）. Also are presented the controller design and its implementation, the embedded adaptive least mean-square （LMS） control algorithm and the real-time experiments of GMSS. Three programs are embedded in this controller. Of them are the adaptive LMS control algorithm and the other two which are used to search for the optimal values for the initial weight vectors. Moreover, the work flow and the control approach of the GMSS with the DSP controller are introduced. The experimental results indicate that the DSP controller has better control precision and real-time property, and the damping effect is up to 20 dB-30 dB.
文摘Today’s challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field（IMF） conditions. Correlative studies between geomagnetic storms（GMSs）and the various interplanetary（IP） field/plasma parameters have been performed to search for the causes of geomagnetic activity and develop models for predicting the occurrence of GMSs, which are important for space weather predictions. We find a possible relation between GMSs and solar wind and IMF parameters in three different situations and also derived the linear relation for all parameters in three situations.On the basis of the present statistical study, we develop an empirical model. With the help of this model, we can predict all categories of GMSs. This model is based on the following fact： the total IMF Btotalcan be used to trigger an alarm for GMSs, when sudden changes in total magnetic field Btotaloccur. This is the first alarm condition for a storm’s arrival. It is observed in the present study that the southward Bzcomponent of the IMF is an important factor for describing GMSs. A result of the paper is that the magnitude of Bzis maximum neither during the initial phase（at the instant of the IP shock） nor during the main phase（at the instant of Disturbance storm time（Dst） minimum）. It is seen in this study that there is a time delay between the maximum value of southward Bzand the Dst minimum, and this time delay can be used in the prediction of the intensity of a magnetic storm two-three hours before the main phase of a GMS. A linear relation has been derived between the maximum value of the southward component of Bzand the Dst, which is Dst =（-0.06） ＋（7.65）Bz＋ t.Some auxiliary conditions should be fulfilled with this, for example the speed of the solar wind should, on average, be 350 km s-1 to 750 km s-1, plasma β should be low and, most importantly, plasma temperature should be low for intense storms. If the plasma temperature is less than 0.5 × 106 K then the Dst value will be greater than the predicted value of Dst or if temperature is greater than 0.5 × 106 K then the Dst value will be less（some nT）.
