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条带型接收换能器是随钻声波测井仪的关键器件,其声学性能直接影响测量信号的质量。利用有限元法对条带型接收换能器进行设计分析。结果表明,接收换能器中的压电片采用并联接线方式接收灵敏度较高,在钻铤波隔声阻带内接收灵敏度起伏小于20 dB。在此基础上分析了压电片个数及几何尺寸对换能器接收灵敏度的影响。条带型接收换能器的压电片个数越多,压电片厚度越大,钻铤波隔声阻带范围内接收灵敏度越高,有利于提高地层波信号测量;压电片高度越大,压电片宽度越小,钻铤波通带范围内灵敏度越低,有利于降低钻铤波信号能量。数值模拟结果对随钻声波测井仪条带型接收换能器的设计及制作有良好的指导作用。 相似文献
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本文在深入研究了时域有限差分算法(Finite-Difference Time-Domain,简称FDTD)和局域导
波端口加载的基础上,对舰载波导缝隙阵进行了全波仿真分析,并利用远场外推的方法计算获得了该阵
列天线的辐射增益(Radiant Gain,简称RG).计算结果表明本方法具有很好的计算精度,在不同工作频
率的仿真条件下均与商业软件的计算结果吻合很好,验证了该方法的通用性和有效性,为进一步进行含
有舰体的并行全波仿真提供了可能. 相似文献
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本文主要是介绍应用计算机来分析、计算各种信号进入电路后的响应。信号选用:脉冲串、三角波、锯齿波、梯形波、阶跃波、单个梯形波、单个三角波、矩形脉冲串、幅值调制波、阶梯波、半波整流、全波整流、衰减的正弦波、过冲衰减波、 相似文献
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当电磁波频率增大到太赫兹频段时,太赫兹波的波长与粗糙表面微结构可比拟。粗糙表面将对太赫兹波的传播机理产生重要影响,散射在传播中将发挥关键作用。当下针对太赫兹频段散射特性的研究主要依靠大规模测量,较难实现。因此,使用建模的方法生成符合实际物理分布的粗糙表面,借助全波仿真的方法研究太赫兹波和表面粗糙度的作用机理是研究太赫兹波散射特性的新途径。提出使用轮廓仪捕获典型材料的物理分布特性,并从中提取粗糙面的关键统计参数。基于蒙特卡罗方法,依据统计参数重建该表面的物理分布。将测量表面和重建表面导入Feko进行全波仿真,比较并验证该研究方案的可行性。 相似文献
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在无线通信系统中,空间功率的灵活分配有助于实现不同辐射方向信号覆盖强弱的按需调节,提升不同方向通信质量与用户体验。本文提出了一种动态可调的太赫兹空间功分器,可以用于太赫兹波信号在不同空间信道上的强度分配与动态调控,也可应用在双空间信道上进行高效信号调制。全波仿真实验证明,所提出的超表面功分器基于极化转换与波前控制的方式,能够很好地实现设计预期的功能。该功分器既能通过对入射载波信号功率进行二次动态分配的策略,为不同空间信道上通信质量的保障提供帮助;也可单独作为信号调制器使用,通过双空间通道半周期延迟同时完成两路信号的高效率调制。所提出的超表面器件将可能在无线通信、信号控制等领域具有潜在应用价值。 相似文献
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当调频连续波合成孔径雷达(FMCW-SAR)工作在滑动聚束模式下,在时域和频域中都不存在一个合适的方位向窗函数,能够同时符合场景中所有点目标的回波形式。因此场景回波模拟只能采用时域算法,导致模拟回波时运算量巨大。针对这一问题,该文提出一种新的距离多普勒域快速回波模拟算法。该算法在一定近似条件下,通过引入方位向线性调频信号,解决了场景回波信号方位向窗函数的构造问题,并在距离多普勒域生成回波信号的相位信息,在保持较高回波模拟精度的同时,极大地提高了运算速度,并且场景目标点数越多时运算速度提高的倍数越大。仿真结果验证了理论分析的正确性。 相似文献
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滑模控制开关变换器的分析与实现 总被引:4,自引:0,他引:4
分析了滑模控制DC/DC变换器的滑模存在条件、到达条件及稳定性,通过选择适当的状态变量,建立系统状态方程模型。提出了一种实用性较强的双环控制方案,并以Buck电路为例,设计出滑模控制电路。实验结果表明,此控制方案是可行的,它可以有效地改善变换器的动态性能,提高其鲁棒性。 相似文献
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《Mechatronics》2015
The Hardware-In-the-Loop (HIL) simulation is a powerful mean to reduce costs in the design and manufacturing process of an engineering system. HIL techniques allow to use real components inside a simulation of a mathematical model. In this work such techniques are used on the ISWEC wave energy system. ISWEC (Inertial Sea Wave Energy Converter) converts sea waves energy to electric energy by means of the gyroscopic effects produced by a spinning flywheel. The peculiarity of the system lays in the fact that all the moving parts needed to produce energy are sealed inside a hull and therefore protected from the aggressive ocean climate. During the research process on the ISWEC, the gyroscope and the electric generator have been manufactured and mounted on a test rig able to simulate the wave actions on the hull of ISWEC. Those real parts of the system have been replaced inside the full mathematical model of ISWEC. Such HIL system is validated against real wave tank tests carried out at the INSEAN in Rome. The HIL simulations proved to reproduce the real behavior in water waves of ISWEC with errors as small as the 10%. 相似文献
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本文综述了非均匀介质中场与波理论近年来的研究进展及其应用成果,着重介绍了非均匀介质中的电磁场正演分析和反演计算中的各种高效数值方法,以及它们在电法测井数值模拟和成象研究中的成功应用。 相似文献
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Upper limb amputees have expressed the desire for their prosthetic hands to better adapt to the parameters of different grasped objects. In response to this need, an adaptive sliding mode controller (ASMC) is developed that has a variable-slope manifold which is dependent upon the stiffness of the grasped object. The ASMC is experimentally compared to a sliding mode controller (SMC) which has a constant manifold slope over a wide range of grasped object stiffness, ranging from an empty hand to a steel bar. Experimental results indicate that both controllers have satisfactory percent overshoot characteristics; however, the ASMC has significantly less absolute error for all experiments performed with eight different levels of grasped object stiffness. 相似文献
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《Mechatronics》2014,24(4):385-393
In high-precision motion systems, tracking often comes with the problem of overshoot or poor settling behavior. To deal with this problem, a sliding mode controller with saturated integrator is studied. For large servo signals, sufficiently removed from the sliding surface, the controller will operate in PD mode. This limits the integrator buffer, and thus the overshoot. At the sliding surface (for small servo signals) the controller operates in PID mode with the aim to avoid steady-state error. Tuning of the controller parameters: the switching gain and the saturation length, strongly affects the tracking performance. For this reason, a self-tuning method is proposed. In the method, the required gradients are partly computed using models of the system and the controller. For the remaining part, sampled data is used to deal with disturbances and model uncertainties. With a Levenberg–Marquardt algorithm numerical problems associated with the gradient computations are avoided. The sliding mode controller with optimized parameters is implemented on an industrial wafer scanner to improve throughput during the wafer stage (chuck) exchange. 相似文献