半导体热电制冷片在汽车保温箱控制系统中的应用

半导体制冷片又叫热电制冷片,可应用在一些空间非常小的环境,没有化学制冷剂,对环境无污染.该文提出了利用51单片机控制半导体热电制冷片,实现车载保温箱进行加热制冷的硬件电路和软件设计原理.硬件电路主要由输入输出、温度采集和反馈、控制电路组成,控制算法主要采用了滞环控制策略.整个系统结构简单,运行可靠.     

并联复合隔震体系非线性性能的试验研究

对一并联复合隔震结构模型进行了振动台试验研究,通过逐渐增加摩擦滑板的数量来调整隔震层摩擦承压比的大小。分析了复合隔震体系不同摩擦承压比对隔震层滞回特性、基底剪力系数以及复合隔震体系非线性性能的影响。试验结果表明:复合隔震结构的非线性特性与摩擦承压比的大小及地震烈度大小有关,在合理的摩擦承压比取值范围内复合隔震结构具有良好的隔震性能。     

聚合物材料转矩流变仪转矩测量系统的研究

通过虚拟样机仿真对新型用于转矩流变仪的转矩测量系统进行了精度及可靠性分析。仿真表明,随着回差的增大,系统的误差也显著增大,因此在设计转矩流变仪时,对减速器的选择提出了一定的精度的要求。在仿真基础上研制了转矩测量系统部件。试验表明这种测量系统消除了机械系统所造成的回滞误差,使研制的转矩测量系统具有优于0．1％的测量精度。     

基于预测电流控制的有源功率滤波器的研究

通过分析APF的数学模型和预测电流理论,推导出了预测电流控制在有源滤波器中的应用.利用预测电流控制的数学推导过程,对反馈调节和最优化处理做了分析,并对控制参数与系统性能之间的关系进行了讨论.     

5kW光伏并网发电系统及其仿真研究

随着新能源发电的迅速发展,越来越多的可再生能源被转化为电能并通过并网逆变器输送到电网。利用MATLAB仿真工具箱建立了由光伏阵列输出、Boost升压电路、逆变器、控制器、电网等组成的5 kW光伏并网发电系统的仿真模型,研究了光伏并网系统的特性。采用变结构模糊PID控制器实现5 kW光伏发电系统的MPPT;采样电网电压作为逆变器电流的参考信号,利用滞环比较法控制逆变器,实现系统输出电流与电网电压同频同相,功率因素近似为1。仿真结果表明,系统较好地实现了光伏发电系统的MPPT及安全并网,对实际光伏并网系统的设计有参考意义。     

A New Prototype Two‐Phase (TiNi)–(β‐W) SMA System with Tailorable Thermal Hysteresis

The Ti–Ni–W two‐phase shape memory alloy (SMA) thin film system is presented as a prototype for new SMAs with tailorable thermal transformation hysteresis (ΔT). The concept is to combine the SMA TiNi with almost insoluble W to create the two‐phase system (TiNi)–(β‐W). This system behaves like a pseudobinary TiNi system. Phase transformation behavior for compositions above the solubility limit of W in TiNi exhibit a B2–R phase transformation with characteristically small ΔT. Moreover, ΔT is dependent on the amount of W and it can be tailored to zero and even negative. This phenomenon is rationalized as being due to the mechanical interaction between the phases B2‐TiNi and β‐W. The presented results are very promising for the development of high‐speed Ti–Ni‐based SMA actuators.     

Fatigue,Magnetic and Mechanical Hysteresis

Abstract: The objective of this research is to explore correlations between piezomagnetic signals of initially unmagnetised ferromagnetic steel samples of AISI 1018 steel with progressive changes that take place during the fatigue process. A series of strain‐controlled fatigue tests were carried out to quantitatively study the piezomagnetic fields surrounding steel specimens by measuring magnetic field variations in the milligauss range resulting from the cyclic application of stress. It was observed that the piezomagnetic hysteresis traces change systematically with the progression of fatigue. The piezomagnetic hysteresis loop areas, when plotted as a function of the number of loading cycles, demonstrate the three principal stages of fatigue: initial accommodation, accretion of damage and terminal failure. The results derived from the piezomagnetic hysteresis traces are consistent with those obtained from mechanical hysteresis studies. However, when approaching failure, the piezomagnetic traces show more conspicuous changes than the corresponding mechanical stress–strain curves. It was also observed that the piezomagnetic field surrounding a specimen subjected to cyclic loading behaves approximately like that of a bar magnet. This study has demonstrated that the piezomagnetic effects can be exploited to evaluate the progress of fatigue in ferromagnetic steels.     

脉冲功率电容器用PbLa(ZrTi)O_3陶瓷性能研究

采用固相反应法制备了Pb0.96La0.06(Zr1-xTix)O3陶瓷,研究了Ti含量对所制陶瓷的电性能和储能特性的影响。结果表明,PbLa(ZrTi)O3陶瓷介电常数与电场强度呈非线性变化关系。当Ti含量x为0.08时,所测电滞回线细长狭窄,并呈下凹趋势,此时极化强度为22.18×10–6 C/cm2,储能密度为1.06 J/cm3。通过流延法制备的脉冲功率电容器击穿电压可大幅度提升,储能密度达1.95 J/cm3,具有高能量转换效率。     

基于PI迟滞模型的压电陶瓷复合控制算法研究

为减小压电陶瓷的迟滞非线性对系统跟踪精度的影响,该文采用经典的存在逆解析的PI迟滞模型对压电陶瓷的迟滞特性进行建模,将PI模型的逆模型用于压电陶瓷的前馈控制算法中,然后设计了神经元比例、积分、微分(PID)反馈控制算法,将前馈控制算法与神经元PID反馈控制算法结合得到了压电陶瓷的复合控制算法。将仅含前馈的控制算法和复合控制算法在压电陶瓷的控制器上执行,实验结果表明,仅含前馈的控制算法的跟踪误差为1.256μm,而复合控制算法的跟踪误差仅为0.092μm,该复合控制算法使跟踪精度提高了1.164μm。     

钢-混凝土组合箱梁弯矩-曲率恢复力模型研究

截面弯矩-曲率滞回规则是钢-混凝土组合梁最重要的力学特性之一,该滞回模型的建立为组合箱梁结构的弹塑性分析提供了可行性。利用幂函数插值方法,考虑剪力连接度对组合箱梁截面弯曲刚度的影响,提出了考虑界面滑移的钢-混凝土组合箱梁正向、负向截面弹性刚度及截面屈服弯矩计算方法,建立了组合箱梁截面弯矩-曲率三折线骨架曲线模型;在试验数据与理论分析的基础上,获得了组合箱梁正向及负向刚度退化规律表达式,并进一步提出了钢-混凝土组合箱梁截面弯矩-曲率最大点指向型滞回模型,将该模型的分析结果同试验结果进行了比较。结果表明:提出的组合箱梁截面弹性刚度、屈服弯矩、弯矩-曲率骨架曲线模型及滞回模型均与试验结果吻合良好,且模型计算方法简单明了,便于手算。