Study on fast calibration of a ULA's gain and phase error

Array calibration is important in engineering practice. In this paper, fast calibration methods for a ULA's gain and phase errors both in far and near fields are proposed. In the far field, using a single sound source without exact orientation, this method horizontally rotates the array exactly once, performs eigen value decomposition for the covariance matrix of received data, then computes the gain and phase error according to the formulas. In the near field, using the same single sound source, it is necessary to rotate the array horizontally at most three times, build equations according to geometric relations, then solve them. Using the formula proposed in this paper, spherical waves are modified into plane waves. Then eigen values decomposition is performed. These two calibration methods were shown to be valid by simulation and are fast, accurate and easy to use. Finally, an analysis of factors influencing estimation precision is given.     

相位误差对信干比估计性能的影响

通过使用概率密度函数估计的方法,得出CDMA系统解扩后基带信号近似服从高斯分布。因此,CDMA系统信干比估计可以采用高斯白噪声条件下BPSK调制基带信号的信噪比估计方法。在此基础上,通过理论分析和计算机仿真,比较存在相位误差情况下三种信干比估计方法的性能。仿真结果表明,基于二阶矩和四阶矩的估计方法M2M4不受相位误差的影响,适合工程应用。     

强制沥青搅拌设备干燥滚筒振动原因分析及预防措施

通过对大吨位间歇式沥青搅拌设备干燥滚筒驱动原理介绍，分析了滚圈和托轮在机加工过程、装配过程中出现误差对干燥滚筒产生振动的影响。有针对性地实施预防，明确了干燥滚筒筒体与滚圈在装配时应采用的工艺基准，同时提出了干燥滚筒与托轮组装时以托轮为基准的优势。     

减少数控机床伺服轴定位误差的方法

通过对数控系统补偿功能有关数据的计算和设置,实现了对机床伺服轴定位误差进行补偿,使该项误差限制在机床允许误差范围内,提高了机床的加工精度。     

磁罗经自差半自动测校装置

提出一种磁罗经自差半自动测校方法，并从旋回法测定自差原理计算自差系数，安放磁棒位置和软铁数量，所用磁场传感器基本原理，罗经涡动误差的影响，半自动测校装置组成等方面，论证了研制磁罗经自差半自动测校装置的可能性。     

Identification of linear handling models for road vehicles

This study reports the identification of linear handling models for road vehicles starting from structural identifiability analysis, continuing with the experiments to acquire data on a vehicle equipped with a sensor set and data acquisition system, and ending with the estimation of parameters using the collected data. The model structure originates from the well-known linear bicycle model that is frequently used in handling analysis of road vehicles. Physical parameters of the bicycle model structure are selected as the unknown parameter set that is to be identified. Global identifiability of the model structure is analysed, in detail, and concluded according to various available sensor sets. Physical parameters of the bicycle model structure are estimated using prediction error estimation method. Genetic algorithms are used in the optimisation phase of the identification algorithm to overcome the difficulty in the selection of initial values for parameter estimates. Validation analysis of the identified model is also presented. The identified model is shown to track the system response successfully.     

差分GPS的对流层伪距残差的计算机模拟

简单回顾了对流层中GPS信号传播延迟的原理。介绍了2种常见的校正模型,Hopfield模型和Black模型。定义了差分GPS(DGPS)的对流层伪距残差的概念,并建立了数学模型。用计算机对DGPS的对流层伪距残差进行仿真。仿真结果表明用户和基准台之间距离增大和低卫星仰角都将使伪距残差增大,气象因素和高程对伪距残差也有影响。     

基于通信的列车控制系统移动数据通信关键问题的探讨

首先分析了基于通信的列车控制(Communication Based Train Control,CBTC)系统移动数据通信的现状、特点、要求;然后分析了无线数据平台使用的技术:直接序列扩频、全双工、时分复用多址、码分复用多址、差错控制、移动性管理、数据通信协议;最后分析了CBTC信息内容和数据安全传输方法。     

助飞式水声对抗器材落点测量方法及误差分析

助飞式水声对抗器材落点精度海上试验因海况、测量手段等因素限制一直是试验的重难点问题。本文从分析助飞式水声对抗器材基本工作原理和其落点精度影响因素入手,即光学定位法、水声定位法、人工定位法和遥测定位法四种落点精度海上试验的测量方法。对四种测量方法的优势、劣势进行了对比分析,提出了一种基于Matlab软件的数据处理方法,并对测量结果的误差进行了对比分析,综合提出了根据海上试验环境条件和测量保障条件进行海上试验的优选原则。     

基于PLC的工程运输车辆协同作业的定位与控制

对工程实践中运输车辆搭载的定位控制以及相关系统的设计问题进行简单的讨论，并利用PLC自动化控制系统以及相关的模糊控制算法对翻斗汽车以及运输车进行控制以实现定位。通过函数系统中的误差分析法对定位中所产生的误差进行较为详细的分析，最终结论是该定位与控制方法能够完全满足相关误差要求。