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841.
We propose a measurement feedback controller for a class of feedforward nonlinear systems under sensor noise. The sensor noise has unknown magnitude, frequency, and phase. Our proposed controller is coupled with a low‐pass filter in such a way that the sensor noise is attenuated. We show that the controlled system results in bounded states whose ultimate bounds are inversely proportional to the minimum frequency of the sensor noise. Our result is further generalized to work in a case where the sensor noise is only required to have a Fourier transform with finite energy. Moreover, if the sensor noise enters only at partial states, depending on the location of the sensor noise, the ultimate bounds of the particular states can be made arbitrarily small via the gain factor of the controller. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
842.
By etching slots in the low‐impedance section of the conventional stepped‐impedance resonator, a novel slotted stepped‐impedance resonator (SSIR) is proposed. As two examples, a fourth‐order bandpass filter (BPF) operating at 1 GHz with a size of 0.078 λg × 0.062 λg and a miniaturized diplexer operating at 0.9/1.57 GHz with a size of 0.054 λ0 × 0.086 λ0 are designed based on the proposed SSIR. The fabricated BPF exhibits a high selectivity and a wide ?30 dB rejection upper stopband from 1.13 f0 to 6.52 f0, while the fabricated diplexer has up to ?60 dB output isolation. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013. 相似文献
843.
Rotman lenses are used to obtain multiple beams from a single array. Although the beams produced by the feed antennas at focal points have no path length errors, the beams produced by feed antennas at off focal points may have large path length errors. These path length errors cause deterioration in the multiple beams. In this article, two novel methods are introduced to obtain feed curves which reduce the path length errors of off focal feed points significantly, compared with the commonly used circular and elliptical feed curves. The first method obtains feed curve points based on having zero path length error at three chosen points of the radiating array for each beam direction. The second method uses the particle swarm optimization method for obtaining optimum feed points for each beam direction. The results show that there is a very significant drop in the level of the maximum path length errors (in the order of about 1:4). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 634–638, 2013. 相似文献
844.
The position control system of an electro-hydraulic actuator system (EHAS) is investigated in this paper. The EHAS is developed by taking into consideration the nonlinearities of the system: the friction and the internal leakage. A variable load that simulates a realistic load in robotic excavator is taken as the trajectory reference. A method of control strategy that is implemented by employing a fuzzy logic controller (FLC) whose parameters are optimized using particle swarm optimization (PSO) is proposed. The scaling factors of the fuzzy inference system are tuned to obtain the optimal values which yield the best system performance. The simulation results show that the FLC is able to track the trajectory reference accurately for a range of values of orifice opening. Beyond that range, the orifice opening may introduce chattering, which the FLC alone is not sufficient to overcome. The PSO optimized FLC can reduce the chattering significantly. This result justifies the implementation of the proposed method in position control of EHAS. 相似文献
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848.
目标距离是战场进行作战决策和武器使用时考虑的一个重要参数.在传统的二维被动跟踪系统基础上,将目标建模为椭圆刚体.论文借鉴修正极坐标(MPC)的思想,利用刚体目标的尺寸参数,建立目标的状态模型和测量模型.采用无迹卡尔曼滤波(UKF)算法进行解距离,为工程实现提供了可能性,并从不同的初始条件下分析了距离误差.Monte-Carlo仿真表明:在新的状态模型下利用UKF算法进行解距离,可以达到较高的精度.其中传感器与目标的相对速度和刚体目标的尺寸对距离解的精度影响较大. 相似文献
849.
罗智锋 《计算机与数字工程》2013,41(8)
随着网络的应用,不同平台的协同作战成为一种趋势,该趋势促成了异类平台间的数据融合需求.作为典型的协同模式,异平台的雷达和ESM观测的坐标系不同,无法直接融合,且二维ESM数据和三维雷达数据直接融合的精度较低.论文提出将雷达距离及方差转换到ESM坐标系下,转换得到虚假的距离量测结合ESM的角度量测,在三维坐标下进行Kalman滤波,获得ESM的估计及协方差矩阵,再进行协方差交集估计处理,可以较大的提高估计精度. 相似文献
850.
Light detecting and ranging(LiDAR)technology has become an efective way to generate highresolution digital terrain models(DTMs).To generate DTMs,point measurements from non-ground features,such as buildings,vegetation and vehicles,have to be identifed and removed while preserving the terrain points.This paper proposes an efcient mathematical morphology-based multi-level flter to generate DTMs from airborne LiDAR data.Preliminary non-ground points are frst identifed with the characteristics of the multiecho airborne LiDAR data.The localized mathematical morphology opening operations are then immediately applied to the remaining points.By gradually increasing the window size of the flter and using a dynamic critical gradient threshold,the non-ground points are removed,while the ground points are preserved.Eight samples were chosen from eight sites provided with the ISPRS Commission III,Working Group 3,to evaluate the accuracy of our algorithm.Both the qualitative and quantitative experiment analyses show that our morphologybased multi-level flter method achieves promising results,not only in flat urban areas but also in rural areas,especially in preserving complex terrain details,while non-ground spatial objects are removed. 相似文献