一种带滤波功能的圆极化可控阵列天线

提出了一种带滤波功能的2′2圆极化可控阵列天线,采用探针对每个辐射贴片进行馈电,通过控制辐射贴片的激励相位和极化,实现整个阵列天线的圆极化特性。嵌入在阵列天线馈电网络中的耦合谐振器对保证了馈电网络在幅度响应上呈现滤波特性的同时,在相位上控制每个辐射贴片激励端口处的信号相位在-90°和90°之间变化,同时结合90°移相网络,可实现对整个阵列天线左旋圆极化(LHCP)和右旋圆极化(RHCP)的控制。实测结果表明:该阵列天线能控制辐射的圆极化特性,并获得优异的LHCP和RHCP特性;在两种极化状态下,阵列天线工作频带内均具有较为平坦的增益特性,平均增益为10.4 dBic,带外增益特性呈现较好的滤波特性,在远离通带上、下边带100 MHz 处增益抑制均达到8.6 dB以上。     

α－β滤波器的基本问题分析与仿真研究

针对α-β滤波器滤波增益随采样时刻的增加而减小的问题,提出了一种根据位置滤波平均误差、速率滤波平均误差以及速度滤波效果确定滤波增益下降截止时刻的方法,并分析了可能影响滤波增益下降截止时刻的因素。仿真结果表明：通过该方法确定的滤波增益下降截止时刻可以使α-β滤波器的滤波效果达到最佳;滤波增益下降截止时刻与目标采样间隔的相关性最强,与过程噪声的相关性次之,与量测噪声的相关性最弱。     

FPGA实现滑动平均滤波算法和LZW压缩算法

针对数据采集系统高速长时间的采样和后端数据传榆及存储能力有限的问题,提出基于FPGA的数据压缩解决方案.同时为平滑采集数据中的量化噪声,在进行数据压缩前采用滤波的预处理技术.介绍LZW算法和滑动滤波算法的基本理论,详细阐述用单片FPGA实现两种算法的方法.最终测试结果表明,该设计方案能够有效滤除数据中的高频噪声,同时也可获得较好的压缩比和压缩速度,具有一定实用价值.     

一种基于折合式平面反射阵天线的毫米波高增益滤波天线

提出了一种基于折合式平面反射阵天线的毫米波高增益滤波天线设计方法,将极化敏感的频率选择表面替代传统的极化栅,用作折合式平面反射阵天线的副反射面。基于基片集成波导技术设计了极化敏感的频率选择表面,该频率选择表面对于线性极化入射波情况下具有较低的插入损耗,同时可几乎全反射对应正交极化的入射波。得益于频率选择表面的频率选择特性,折合式平面反射阵天线可获得良好的滤波性能。为了验证该滤波天线的设计方法,设计并制作了一款Ka频段的毫米波高增益滤波天线,在35~37 GHz的工作频带,天线具有良好的辐射特性和滤波特性。     

程控滤波器

为了适应工程应用中幅度和频率变化范围很宽的信号,设计了一种增益、频响特性和截止频率可程控的程控滤波器。系统以单片机和FPGA为控制核心,由可控增益放大、程控滤波、椭圆滤波、频率特性测试4部分组成。其中,可控增益放大部分以AD603为核心,级联三路固定增益放大;程控滤波部分巧妙地将两个二阶状态变量滤波级联,并将DAC等效为数控电阻,使得截止频率可调。实验结果表明,整个系统工作稳定,可以很好的实现程控滤波的功能。     

程控滤波器

为了适应工程应用中幅度和频率变化范围很宽的信号,设计了一种增益、频响特性和截止频率可程控的程控滤波器。系统以单片机和FPGA为控制核心,由可控增益放大、程控滤波、椭圆滤波、频率特性测试4部分组成。其中,可控增益放大部分以AD603为核心,级联三路固定增益放大;程控滤波部分巧妙地将两个二阶状态变量滤波级联,并将DAC等效为数控电阻,使得截止频率可调。实验结果表明,整个系统工作稳定,可以很好的实现程控滤波的功能。     

基于FPGA的小波图像实时处理方法

基于小波变换的滤波方法应用于红外图像处理中可以在降低噪声的同时提升图像细节,有效改善图像画质.介绍了一种采用FPGA的小波图像处理方法及其硬件处理架构.通过合理有效地进行算法硬件设计,在单片FPGA芯片上实现了图像的实时处理,有利于红外机芯的小型化.     

机动雷达大惯量天线定位控制策略

由于机动雷达大惯量天线的加速度受限,所以在加速度无法提高的前提下,如何减少大惯量天线的转动中定位时间尤为重要.文中提出了一种特殊的机动雷达大惯量天线转动中定位控制策略-分区域定位控制策略,比较了这种控制策略与常规控制方法的优劣,且基于以驱动器为速度内环的控制系统,给出了采用单片机控制的位置环控制电路,并简述了控制软件的实现方法.以实际控制模型为依托、以改善的定位时间为支撑、以简化的定位控制策略为主线,详细介绍了这种新型控制策略的工程运用.     

常增益滤波法在机载雷达伺服系统中的应用

介绍了应用在机载雷达伺服系统中的常增益滤波法的原理，以及实现模型和算法参数的选择方法。论述了在滤除角度噪声，替代角速度传感器构成速度环路完善系统校正，提供角度插值条件等方面的作用。     

基于Stratix Ⅱ EP2S60的改进中值滤波器的设计及实现

在红外搜索跟踪系统中,为了有效可靠地对目标进行探测、跟踪,必须对红外图像进行滤波预处理,从而提高图像信号的信噪比.为满足实时红外图像预处理时对速度的高要求,采用了一种利于硬件实现的中值滤波改进算法,以Altera公司的Stratix Ⅱ系列EP2S60型FPGA为平台,成功实现了对256×320×16 bit图像的中值滤波,整个电路去噪效果明显,速度满足要求.     

新型光纤传感用角度调谐Fabry-Perot滤波器

提出一种光纤传感用可调谐滤波器方案,使用伺服电机驱动滤波片匀速旋转,利用改变入射光角度的方式实现连续调谐波长输出。结合光纤传感的解调原理,设计了基于DSP芯片的伺服电机控制电路。通过选择PID控制算法及PID参数稳定伺服电机转速,在1 530～1 570nm的波长调谐范围内,该滤波器实现了比较高的重复性和稳定性,由电机转速抖动误差造成的解调波长的误差控制在±10pm内,成本低,控制方便,可用于光纤传感系统。     

基于目标运动状态估计的视觉伺服控制

基于位置的视觉伺服控制中,为了降低噪声及图象采集和处理延时带来的影响,采取了一种基于Kalman滤波的视觉伺服方法,并给出了二自由度机器人跟踪圆周运动的仿真结果,较好的解决了采样时间的延时,并减小了位姿估计时噪声的影响。     

Performance-Improved Design of N-PID Controlled Motion Systems With Applications to Wafer Stages

A nonlinear filter design is proposed to improve nanopositioning servo performances in high-speed (and generally linear) motion systems. The design offers a means to adapt fundamental control design tradeoffs-like disturbance suppression versus noise sensitivity-which are otherwise fixed. Typically performance-limiting oscillations in the feedback system that benefit from extra control are temporarily upscaled and subjected to nonlinear weighting. For sufficiently large amplitudes, this nonlinear filter operation induces extra controller gain. Oscillations that do not benefit from this extra control (typically because they represent noise contributions that should not be amplified) remain unscaled and, as such, do not induce extra controller gain. The combined usage of linear weighting filters with their exact inverses renders this part of the nonlinear filter design strictly performance based. The effective means to improve servo performance is demonstrated on a short-stroke wafer stage of an industrial wafer scanner. Since the nonlinear filter design is largely based on Lyapunov arguments, stability is guaranteed along the different design steps.     

Discrete-time LQG/LTR design and modeling of a disk drive actuatortracking servo system

This paper presents the discrete-time LQG/LTR design of a disk drive track following servo system. The servo compensator designed through linear-quadratic Gaussian control combined with loop transfer recovery (LQG/LTR) consists of a Kalman filter for state estimation and state feedback for control. The desired tracking servo performance is first formulated through a frequency shaped return ratio of the Kalman filter and subsequently recovered at the output of the plant/compensator loop through the automatic design of a discrete-time linear quadratic (LQ) regulator. Particular attention has been given to modeling the calculation time delay and bias force estimation. The excellent robustness and performance characteristics of a continuous time LQG/LTR design are theoretically unachievable due to the extremely low sampling rate and nonminimum phase plant characteristics. However, both time and frequency domain simulations show that reasonable stability margins and performance can still be recovered. This technique nearly eliminates all the trial and error typical of a conventional pole placement design of a similar system. The direct discrete-time design can handle extremely low sampling rates associated with embedded servo systems. The technique can also be used for designing multi-rate and multi-input servo systems     

基于改进的PID稳定平台伺服控制系统

传统PID控制在伺服系统高精度位置跟踪和改善系统品质方面已露出诸多不足,且系统中存在的控制干扰和测量噪声会在很大程度上影响伺服系统的跟踪精度。针对工作实际中的被控对象控制问题,对传统的PID控制算法进行改进。提出一种带有卡尔曼滤波器的重复控制补偿PID和前馈补偿相结合的控制方法。通过仿真证明,该控制方法能以较高的精度跟踪周期性输入信号,且有较好的抑制随机扰动和鲁棒性。     

Sliding-mode control of a nonlinear-input system: application to amagnetically levitated fast-tool servo

Magnetic servo levitation (MSL) is currently being investigated as an alternative to drive fast-tool servo systems that could overcome the range limitations inherent to piezoelectric driven devices while operating over a wide bandwidth. To control such systems, a feedback-linearized controller coupled with a Kalman filter has been previously described. Performance limitations that degrade tracking accuracy suggest the use of a more robust controller design approach, such as sliding-mode control. Current literature on sliding mode deals almost exclusively with systems that are affine on the input, while the magnetic fast-tool servo is nonlinear on it when the control action is current command. This paper discusses a sliding mode-based controller that overcomes the aforementioned problem by defining a modified sliding condition to calculate control action. Experimental results demonstrate the feasibility of achieving long-range fast tracking with magnetically levitated devices by using sliding-mode control     

Track-Following Control Using Resonant Filter in Hard Disk Drives

A design method to suppress the disturbances by using a resonant filter for track-following control has been developed. The resonant filter can realize a stable resonant mode by a filter to obtain a circular vector locus that recedes from the critical point on the Nyquist diagram. With this method, the control engineers can easily design and implement a controller to suppress the disturbances in head-positioning systems at a specific frequency by adding digital filters. Our experimental results show that the proposed method can greatly suppress the nonrepeatable runout and repeatable runout above the servo bandwidth.     

压电微执行器在硬盘伺服系统的应用研究

介绍一个硬盘双伺服控制系统的设计和实现。双伺服系统是在硬盘固有的音圈电机上附加了一个压电微执行器,用来执行更快捷、精确的磁头定位。对音圈电机的控制设计采用了一种线性反馈控制技术,结合扰动估计和补偿实现快速、平稳和无静差的设定点跟踪。基于开环逆控制的思想,微执行器环路的控制采用定值比例及滤波器,使得合并的位移输出能更快地跟踪设定点(磁道)。仿真和实验结果证明双伺服控制系统可以实现更快速、精确的磁头定位。     

干扰条件下反舰导弹导引头伺服系统研究

反舰导弹导引头伺服系统对于目标搜索、目标跟踪和目标参数测量起着重要作用,它的精度直接影响反舰导弹制导精度.首先根据导引头伺服系统结构,在干扰条件下对导引头角稳定回路、角跟踪回路和角预定回路进行分析,建立导引头伺服系统数学模型;为提高导引头抗干扰能力,在角跟踪回路中引入Kalman滤波器,通过滤波可以为系统提供精确的目标数据;然后结合工程实际,构建导引头伺服系统的Simulink控制模型,并进行动态仿真;最后得到系统的动态响应结果.仿真结果表明,该方法可以有效提高导引头的响应速度和跟踪精度,为反舰导弹雷达导引头的工程设计提供了科学依据.     

Head-positioning control using resonant modes in hard disk drives

The best way to enhance the input/output (I/O) performance of a hard disk drive is by increasing the spindle speed. Therefore, the effect of windage vibrations caused by the airflow increases as the spindle speed increases. The servo bandwidth is limited by the primary resonant frequency of the mechanical system. However, the frequencies of the windage vibrations are higher than the primary resonant frequency. Accordingly, these frequencies are also above the servo bandwidth and are too high to be controlled by a conventional control system. In response to this problem, we have developed two methods for designing a servo control system that can suppress the windage vibrations. One method uses a stable mechanical resonant mode, and the other uses a stable resonant mode created by a digital filter. By using these methods, the head-positioning system can control the vibrations above the frequency of the primary resonant mode and the servo bandwidth. Application of these methods to actual hard disk drives showed that they can greatly decrease the windage vibrations, in which the peak frequency is about six times the open-loop gain 0-dB crossover frequency.