Random vibration control is aimed at reproducing the power spectral density(PSD)at specified control points.The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple frequenc...Random vibration control is aimed at reproducing the power spectral density(PSD)at specified control points.The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple frequency response functions(FRFs),which lengthens the control loop time in the equalization process.Likewise,the feedback control algorithm has a very slow convergence rate due to the small value of the feedback gain parameter to ensure stability of the system.To overcome these limitations,an adaptive inverse control of random vibrations based on the filtered-X least mean-square(LMS)algorithm is proposed.Furthermore,according to the description and iteration characteristics of random vibration tests in the frequency domain,the frequency domain LMS algorithm is adopted to refine the inverse characteristics of the FRF instead of the traditional time domain LMS algorithm.This inverse characteristic,which is called the impedance function of the system under control,is used to update the drive PSD directly.The test results indicated that in addition to successfully avoiding the instability problem that occurs during the iteration process,the adaptive control strategy minimizes the amount of time needed to obtain a short control loop and achieve equalization.展开更多
红外探测器所成图像存在固有非均匀性缺陷,现有的基于场景的最小均方差(least mean square,LMS)校正算法在对图像进行非均匀性校正时极易引入鬼影,严重限制了校正效果。针对这一瓶颈,本研究以时域门控鬼影抑制技术为基础,创新性地将韦...红外探测器所成图像存在固有非均匀性缺陷,现有的基于场景的最小均方差(least mean square,LMS)校正算法在对图像进行非均匀性校正时极易引入鬼影,严重限制了校正效果。针对这一瓶颈,本研究以时域门控鬼影抑制技术为基础,创新性地将韦伯定律引入红外图像非均匀性校正体系,提出双门控LMS非均匀性校正方法。该方法摒弃了“绝对无鬼影”的理想化数学优化目标,转而以鬼影处于人眼视觉感知阈值之下为核心准则进行校正;构建了全新的“运动终止”目标检测模型以获取可校正像素增量;并通过预判增量校正目标的运动趋势来确定其校正幅度,从而达到各类复杂场景下图像质量和鬼影抑制性能的协同优化。实验结果证明,双门控法可与现有各类基线校正算法灵活叠加部署,具备优异的算法普适性;肉眼观测和各类图像量化指标均显示,相较于传统的时域门控算法,该方法可在不降低鬼影抑制效果的前提下,将校正效率提高最高达60%。展开更多
外辐射源雷达利用直达天线接收的参考信号作为样本滤除目标回波中的杂波,但由于雨、云、树木或其他运动物体等的影响,回波内可能会包含非零频杂波,导致处理后杂波残余较大,影响目标检测。针对上述问题,提出了一种基于杂波识别的扩展最...外辐射源雷达利用直达天线接收的参考信号作为样本滤除目标回波中的杂波,但由于雨、云、树木或其他运动物体等的影响,回波内可能会包含非零频杂波,导致处理后杂波残余较大,影响目标检测。针对上述问题,提出了一种基于杂波识别的扩展最小均方(Least Mean Square,LMS)对消算法。首先利用模糊函数估计杂波的频率和时延分布,构建含频率信息的多个参考信号。再把多个参考信号插入LMS算法中推导了扩展LMS算法,利用扩展LMS算法可以同时对消静、动杂波。扩展LMS算法能降低对消剩余,提高目标的信噪比,仿真分析和实测数据处理验证了算法的有效性。展开更多
A more relaxed sufficient condition for the convergence of filtered-X LMS (FXLMS) algorithm is presented. It is pointed out that if some positive real condition for secondary path transfer function and its estimates i...A more relaxed sufficient condition for the convergence of filtered-X LMS (FXLMS) algorithm is presented. It is pointed out that if some positive real condition for secondary path transfer function and its estimates is satisfied within all the frequency bands, FXLMS algorithm converges whatever the reference signal is like. But if the above positive real condition is satisfied only within some frequency bands, the convergence of FXLMS algorithm is dependent on the distribution of power spectral density of the reference signal, and the convergence step size is determined by the distribution of some specific correlation matrix eigenvalues.Applying the conclusion above to the Delayed LMS (DLMS) algorithm, it is shown that DLMS algorithm with some error of time delay estimation converges in certain discrete frequency bands, and the width of which are determined only by the 'time-delay estimation error frequency' which is equal to one fourth of the inverse of estimated error of the time delay.展开更多
随着先进工艺和技术的不断进步,要想保证数据在高速传输中的正确性,均衡器需要有更高的补偿和更低的功耗,才能实现高效通信。基于12 nm互补金属氧化物半导体工艺,设计了一种高增益、低功耗的自适应连续时间线性均衡器(continuous time l...随着先进工艺和技术的不断进步,要想保证数据在高速传输中的正确性,均衡器需要有更高的补偿和更低的功耗,才能实现高效通信。基于12 nm互补金属氧化物半导体工艺,设计了一种高增益、低功耗的自适应连续时间线性均衡器(continuous time linear equalizer,CTLE),该均衡器采用2级级联结构来补偿信道衰减,并提高接收信号的质量。此外,自适应模块通过采用符号-符号最小均方误差(sign-sign least mean square,SS-LMS)算法,使抽头系数加快了收敛速度。仿真结果表明,当传输速率为16 Gbit/s时,均衡器可以补偿-15.53 dB的半波特率通道衰减,均衡器系数在16×10^(4)个单元间隔数据内收敛,并且收敛之后接收误码率低于10^(-12)。展开更多
随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性...随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性能的制约,导致系统存在谐波检测精度与响应速度之间的矛盾,滤波效果往往受到限制。因此,采用一种基于LMS自适应滤波器的HAPF控制策略,解决了动静态性能无法兼顾的问题。最后设计了一个在输入电压为220 V、额定频率50 Hz、谐波源为三相整流器带可变负载的系统,并利用Matlab/Simulink验证该方案的正确性,研究结果表明,基于LMS自适应滤波器的HAPF控制器滤波效果良好,准确性和实时性较强,能够显著提高系统的控制性能和抗干扰能力,具有广阔的应用前景。展开更多
基金Program for New Century Excellent Talents in Universities Under Grant No.NCET-04-0325
文摘Random vibration control is aimed at reproducing the power spectral density(PSD)at specified control points.The classical frequency-spectrum equalization algorithm needs to compute the average of the multiple frequency response functions(FRFs),which lengthens the control loop time in the equalization process.Likewise,the feedback control algorithm has a very slow convergence rate due to the small value of the feedback gain parameter to ensure stability of the system.To overcome these limitations,an adaptive inverse control of random vibrations based on the filtered-X least mean-square(LMS)algorithm is proposed.Furthermore,according to the description and iteration characteristics of random vibration tests in the frequency domain,the frequency domain LMS algorithm is adopted to refine the inverse characteristics of the FRF instead of the traditional time domain LMS algorithm.This inverse characteristic,which is called the impedance function of the system under control,is used to update the drive PSD directly.The test results indicated that in addition to successfully avoiding the instability problem that occurs during the iteration process,the adaptive control strategy minimizes the amount of time needed to obtain a short control loop and achieve equalization.
文摘红外探测器所成图像存在固有非均匀性缺陷,现有的基于场景的最小均方差(least mean square,LMS)校正算法在对图像进行非均匀性校正时极易引入鬼影,严重限制了校正效果。针对这一瓶颈,本研究以时域门控鬼影抑制技术为基础,创新性地将韦伯定律引入红外图像非均匀性校正体系,提出双门控LMS非均匀性校正方法。该方法摒弃了“绝对无鬼影”的理想化数学优化目标,转而以鬼影处于人眼视觉感知阈值之下为核心准则进行校正;构建了全新的“运动终止”目标检测模型以获取可校正像素增量;并通过预判增量校正目标的运动趋势来确定其校正幅度,从而达到各类复杂场景下图像质量和鬼影抑制性能的协同优化。实验结果证明,双门控法可与现有各类基线校正算法灵活叠加部署,具备优异的算法普适性;肉眼观测和各类图像量化指标均显示,相较于传统的时域门控算法,该方法可在不降低鬼影抑制效果的前提下,将校正效率提高最高达60%。
文摘外辐射源雷达利用直达天线接收的参考信号作为样本滤除目标回波中的杂波,但由于雨、云、树木或其他运动物体等的影响,回波内可能会包含非零频杂波,导致处理后杂波残余较大,影响目标检测。针对上述问题,提出了一种基于杂波识别的扩展最小均方(Least Mean Square,LMS)对消算法。首先利用模糊函数估计杂波的频率和时延分布,构建含频率信息的多个参考信号。再把多个参考信号插入LMS算法中推导了扩展LMS算法,利用扩展LMS算法可以同时对消静、动杂波。扩展LMS算法能降低对消剩余,提高目标的信噪比,仿真分析和实测数据处理验证了算法的有效性。
文摘A more relaxed sufficient condition for the convergence of filtered-X LMS (FXLMS) algorithm is presented. It is pointed out that if some positive real condition for secondary path transfer function and its estimates is satisfied within all the frequency bands, FXLMS algorithm converges whatever the reference signal is like. But if the above positive real condition is satisfied only within some frequency bands, the convergence of FXLMS algorithm is dependent on the distribution of power spectral density of the reference signal, and the convergence step size is determined by the distribution of some specific correlation matrix eigenvalues.Applying the conclusion above to the Delayed LMS (DLMS) algorithm, it is shown that DLMS algorithm with some error of time delay estimation converges in certain discrete frequency bands, and the width of which are determined only by the 'time-delay estimation error frequency' which is equal to one fourth of the inverse of estimated error of the time delay.
文摘随着先进工艺和技术的不断进步,要想保证数据在高速传输中的正确性,均衡器需要有更高的补偿和更低的功耗,才能实现高效通信。基于12 nm互补金属氧化物半导体工艺,设计了一种高增益、低功耗的自适应连续时间线性均衡器(continuous time linear equalizer,CTLE),该均衡器采用2级级联结构来补偿信道衰减,并提高接收信号的质量。此外,自适应模块通过采用符号-符号最小均方误差(sign-sign least mean square,SS-LMS)算法,使抽头系数加快了收敛速度。仿真结果表明,当传输速率为16 Gbit/s时,均衡器可以补偿-15.53 dB的半波特率通道衰减,均衡器系数在16×10^(4)个单元间隔数据内收敛,并且收敛之后接收误码率低于10^(-12)。
文摘随着电力电子设备广泛应用于工业生产的各个领域,电网受到谐波污染的问题日益严重,混合有源滤波器(Hybrid Active Power Filter,HAPF)作为一种有效的谐波抑制手段,受到了广泛关注。然而传统谐波电流检测算法需要受到低通滤波器(LPF)性能的制约,导致系统存在谐波检测精度与响应速度之间的矛盾,滤波效果往往受到限制。因此,采用一种基于LMS自适应滤波器的HAPF控制策略,解决了动静态性能无法兼顾的问题。最后设计了一个在输入电压为220 V、额定频率50 Hz、谐波源为三相整流器带可变负载的系统,并利用Matlab/Simulink验证该方案的正确性,研究结果表明,基于LMS自适应滤波器的HAPF控制器滤波效果良好,准确性和实时性较强,能够显著提高系统的控制性能和抗干扰能力,具有广阔的应用前景。
