分数阶Fourier域多分量LFM信号间的分辨研究

在分数阶Fourier域内,当多分量线性调频(LFM)信号的初始频率和调频率相近时,信号的尖峰会出现无法分辨的现象,导致目标信号漏检.文中分析了LFM信号在分数阶Fourier域的频谱分布特征,以及离散分数阶Fourier变换计算条件下LFM信号的频谱分布特征.推导了两个LFM信号在分数阶Fourier域的临界分辨距离,以及两个LFM信号尖峰之间的距离与量纲归一化因子的变化关系,发现选择合理的量纲归一化因子可以增大两个信号尖峰之间的距离.文中提出一种量纲归一化因子优化选择的方法,该方法可以提高分数阶Fourier变换对多分量LFM信号的分辨能力.最后,仿真结果验证了该方法的有效性.     

人体步行规律与仿人机器人步态规划

从仿生学角度分析了人体的步行运动规律,提出了一种基于人体运动规律的仿人机器人步态参数设定方法.首先对人体步行运动数据进行捕捉并分析,得出人体各步态参数间的函数关系,以人体步行相似性作为评价指标,提出仿人机器人步态参数的设定方法.其次,通过分析人体在步行过程中的补偿支撑脚偏航力矩的基本原理,提出了基于双臂及腰关节协调运动的仿人机器人偏航力矩补偿算法,以提高仿人机器人行走的稳定性.最后通过仿真及实验验证了所提出的步态规划方法的正确性及有效性.     

Research on resolution between multi-component LFM signals in the fractional Fourier domain

When the initial frequencies and chirp rates of multi-component linear frequency modulation (LFM or chirp) signals are close,the signals may not be distinguished in the fractional Fourier domain (FRFD).Consequently,some signals cannot be detected.In this paper,first,the spectral distribution characteristics of a continuous LFM signal in the FRFD are analyzed,and then the spectral distribution characteristics of a LFM signal in the discrete FRFD are analyzed.Second,the critical resolution distance between the peaks of two LFM signals in the FRFD is deduced,and the relationship between the dimensional normalization parameter and the distance between two LFM signals in the FRFD is also deduced.It is discovered that selecting a proper dimensional normalization parameter can increase the distance.Finally,a method to select the parameter is proposed,which can improve the resolution ability of the fractional Fourier transform (FRFT).Its effectiveness is verified by simulation results.     

An iterative linear quadratic regulator based trajectory tracking controller for wheeled mobile robot

We present an iterative linear quadratic regulator(ILQR) method for trajectory tracking control of a wheeled mobile robot system.The proposed scheme involves a kinematic model linearization technique,a global trajectory generation algorithm,and trajectory tracking controller design.A lattice planner,which searches over a 3D(x,y,θ) configuration space,is adopted to generate the global trajectory.The ILQR method is used to design a local trajectory tracking controller.The effectiveness of the proposed method is demonstrated in simulation and experiment with a significantly asymmetric differential drive robot.The performance of the local controller is analyzed and compared with that of the existing linear quadratic regulator(LQR) method.According to the experiments,the new controller improves the control sequences(v,ω) iteratively and produces slightly better results.Specifically,two trajectories,’S’ and ’8’ courses,are followed with sufficient accuracy using the proposed controller.     

易损/危险品物流监测智能微系统

一种基于数据采集、射频识别的信息采集系统,可以采集存储物流过程中超过阈值的振动、湿度以及温度,并记录对应的时间,然后通过无线通信向外发送记录的数据。本系统由三部分组成,包括基于加速度传感器、温/湿度传感器的数据采集模块、基于RFID的无线通信模块及报警模块。本系统不仅可为易损邮寄物品保驾护航,还可对流通中的危险品状态进行实时监测,能应用于多种恶劣环境,实时将报警消息发送至运输人员手中,及时发现问题,提高运输效率,有效地降低运输货品的破损率和危险品的事故率。     

排气歧管流固耦合仿真与试验

针对发动机排气歧管的断裂问题,对某发动机排气歧管的热负荷进行流固耦合分析,并在台架试验中测量其温度场和应变.考虑热辐射和材料的非线性,建立排气歧管的内流场CFD模型、传热模型和有限元模型,分析得到排气歧管的温度场、应力场和塑性应变云图等.仿真结果与试验结果吻合较好.仿真结果表明排气歧管汇合处的温度最高,塑性应变最大位置与试验测得的断裂危险区域吻合.     

大时延遥操作系统的波变量双边自适应控制

针对通信时延对遥操作系统稳定性和透明性的影响,研究了一种基于双边自适应控制和波变量理论的控制方法。通过设计波控制器保证通信传输模块的无源性,在保证系统稳定的基础上,调节波阻抗系数来提高系统的透明性,并在时延10 s的情况下进行主从端速度、位置和力的跟踪仿真实验,结果表明该方法和已有的双边自适应方法相比既能保证系统稳定且透明性好,达到较好的控制效果。     

Tracking video objects with feature points based particle filtering

For intelligent video surveillance, the adaptive tracking of multiple moving objects is still an open issue. In this paper, a new multi-object tracking method based on video frames is proposed. A type of particle filtering combined with the SIFT (Scale Invariant Feature Transform) is proposed for motion tracking, where SIFT key points are treated as parts of particles to improve the sample distribution. Then, a queue chain method is adopted to record data associations among different objects, which could improve the detection accuracy and reduce the computational complexity. By actual road tests and comparisons, the system tracks multi-objects with better performance, e.g., real time implementation and robust against mutual occlusions, indicating that it is effective for intelligent video surveillance systems.