Tracking Performance of Electric Power Steering System Based on the Mixed H_2/H_∞ Strategy

The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide satisfied road feeling for the drivers.

Hydrothermal Synthesis of H_3PW_(12)O_(40)/TiO_2 Nanometer Photocatalyst and Its Catalytic Performance for Methyl Orange

H3PW12O40/TiO2 nanometer photocatalyst was prepared by one step hydrothermal synthesis from H3PW12O40·nH20 and Ti（OBu）4, simultaneously realizing the load and modification of H3PW12O40. The catalyst was characterized by Fourier transform infrared spectroscopy（FTIR）, powder X-ray diffraction（XRD）, nitrogen adsorp- tion-desorption analysis and scanning electron microscopy（SEM）. The results show that the catalyst is Keggin struc- ture and crystallized in anatase structure, the diameter and specific area of the prepared catalyst are 3.8 nm and 177.9 m^2/g, respectively, and its dispersity is better. The photocatalytic properties were compared for TiO2H3PW12O40/TiO2 prepared by impregnation and H3PW12O40/TiO2 prepared by hydrothermal method with methyl orange as a probe. The effects of H3PW12O40 loadings, crystallization method, initial pH and concentration of dye solution on the degradation of methyl orange were investigated.

Effect of H_2S Flow Rate and Concentration on Performance of H_2S/Air Solid Oxide Fuel Cell

A solid state H2S/air electrochemical cell having the configuration of H2S, (MoS2+NiS+Ag)/YSZ/Pt, air has been examined with different H2S flow rates and concentrations at atmospheric pressure and 750-850 ℃. Performance of the fuel cell was dependent on anode compartment H2S flow rate and concentration. The cell open-circuit voltage increased with increasing H2S flow rate. It was found that increasing both H2S flow rate and H2S concentration improved current-voltage and power density performance. This is resulted from improved gas diffusion in anode and increased concentration of anodic electroactive species. Operation at elevated H2S concentration improved the cell performance at a given gas flow rate. However, as low as 5% H2S in gas mixture can also be utilized as fuel feed to cells. Highest current and power densities, 17500mA·cm-2 and 200mW·cm-2, are obtained with pure H2S flow rate of 50ml·min-1 and air flow rate of 100ml·min-1 at 850℃.

Enhanced LMI Representations for H2 Performance of Polytopic Uncertain Systems: Continuous-time Case

Based on two recent results, several new criteria of H2 performance for continuous-time linear systems are established by introducing two slack matrices. When used in robust analysis of systems with polytopic uncertainties, they can reduce conservatism inherent in the earlier quadratic method and the established parameter-dependent Lyapunov function approach. Two numerical examples are included to illustrate the feasibility and advantage of the proposed representations.

Effects of ZnCl2/H2O/C2H5OH Treatment on the Filter Paper Performance

Bleached softwood kraft pulp (BSKP) fibers were pretreated in a 5 mol/L NaOH aqueous solution at 35℃ for 90 min. The ZnCl2/H2O/ C2H5OH was used to treat the pretreated BSKP fibers, filter papers were then prepared. In the course of processing, the effects of various molar ratios of ZnCl2/H2O/C2H5OH on the filter paper performance were evaluated. SEMEDX was conducted to analyze the physical configuration of the filter papers. Moreover, FT-IR and XPS were performed to further characterize the BSKP, the pretreated BSKP and the filter paper fibers. The results indicated that the fibers treated by ZnCl2/H2O/C2H5OH were swollen and exhibited slight fibrillation, leading to a looser fiber structure and therefore, enhanced filter paper performance. Air permeability increased from 161.7 L/(m2·s) to 1450.4 L/(m2·s) for the filter papers when the molar ratio of ZnCl2/H2O/C2H5OH was 1:14:1. The optimum molar ratio of ZnCl2/H2O/C2H5OH was found to be 1:14:1, and no significant effect of ZnCl2/H2O/C2H5OH on fibers’ functional groups was detected. These results showed that filtration performance of filter papers was improved when treated with the ZnCl2/H2O/C2H5OH solution.

H_2和H_∞主动悬架统一的理论框架与比较

以 2自由度 1/ 4车模型为例在鲁棒控制理论的统一框架下讨论H2 和H∞ 主动悬架的设计 ,并采用结构奇异值法和加权最坏RMS增益法对其鲁棒性能进行分析和比较。

H_2/H_∞混合优化问题综述

H2 /H∞ 混合优化设计方法由于其可以使系统同时获得较好的鲁棒稳定性和鲁棒性能 ,一经提出 ,立即受到研究者的广泛关注 .本文综述了 H2 /H∞ 混合优化方法的产生、发展及其特点 ,概要介绍了 H2 /H∞ 优化理论研究的最新进展及实践应用的主要结果 ,分析了 H2 /H∞ 混合优化理论在理论和实际应用中的发展方向 .

巡航导弹成像器稳定装置H_2/H_∞混合最优PID控制器设计

本文针对某巡航导弹成像器稳定装置同时在鲁棒稳定性和系统性能有着很高要求的特点 ,采用H2 /H∞ 混合优化的设计方法设计了H2 /H∞ 混合最优PID控制器。仿真和实验结果表明采用该设计方法设计的巡航导弹成像器稳定装置满足性能要求 ,而且比采用H∞

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl₂Hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat. CaCl2 was used in the system of CHP. We evaluated the heat storage and heat releasing of CHP, and confirmed the practicality from the experimental results. The reactor module employed was an aluminum plate-tube heat exchanger with corrugated fins, and the CaCl2 powder was in the form of a packed bed. Heat storage operation and heat dissipation operation are performed at the same time and supplied to the heat demand destination. At this time, an environmental heat source can be used during the heat radiation operation, and the heat output can release more heat than the heat input during heat storage. The heat discharging and charging characteristics of the reactor module were evaluated experimentally. The coefficient of performance (COP) was calculated for the heat upgrading cycle, and the heat output in the system was determined. A COP of 1.42 and output of 650 W/L, based on the heat exchanger volume, were obtained using a 600 s change time for the heat pump.

蒸汽发生器水位的H_2/H_∞模型预测控制

将蒸汽发生器的线性参数变化模型作为预测模型,设计H2/H∞多目标模型预测控制器.根据鲁棒模型预测控制算法,在线求解多目标优化问题获得控制器.求解时指定一个性能指标优化另一个性能指标,所设计的控制器为变增益控制器.仿真结果验证了此方法的可行性,与串级PID控制相比,具有更好的控制性能.

2-Level R-tree Index Based on Spatial Grids and Hilbert R-tree

Multi-level spatial index techniques are always used in large spatial databases. After a general survey of R-tree relevant techniques, this paper presents a novel 2-level index structure, which is based on the schemas of spatial grids, Hilbert R-tree and common R-tree. This structure is named H2R-tree, and it is specifically suitable for the indexing highly skewed, distributed, and large spatial database. Algorithms and a sample are given subsequently.

Direct Z-scheme CdS-CdS Nanorod Arrays Photoanode: Synthesis,Characterization and Photoelectrochemical Performance

Direct Z-scheme CdO-CdS 1-dimensional nanorod arrays were constructed through a facile and simple hydrothermal process. The structure, morphology, photoelectrochemical properties and H2 evolution activity of this catalyst were investigated systematically. The morphology of the obtained nanorod is a regular hexagonal prism with 100-200 nm in diameter. The calcination temperature and time were optimized carefully to achieve the highest photoelectrochemical performance. The as-fabricated hybrid system achieved a photocurrent density up to 6.5 mA/cm2 and H2 evolution rate of 240 μmol·cm-2·h-1 at 0 V vs. Ag/AgCl, which is about 2-fold higher than that of the bare CdS nanorod arrays. The PEC performance exceeds those previously reported similar systems. A direct Z-scheme photocatalytic mechanism was proposed based on the structure and photoelectrochemical performance characterization results, which can well explain the high separation efficiency of photoinduced carriers and the excellent redox ability.

差分进化改进微电网负荷频率混合H2/H∞鲁棒控制

针对外部扰动及系统参数摄动引起微电网负荷频率波动问题,设计了混合H2/H∞鲁棒控制器对系统负荷频率进行控制。建立了包含电池的柴油发电机组二次频率控制模型,引入低通滤波器,使电池对系统高频扰动信号具有较好的抑制能力。以误差平方的积分最小作为系统的目标函数,在综合H_2范数表征的系统性能和H∞范数表征的鲁棒性能下,设计具有多目标约束条件的混合H2/H∞鲁棒控制器。采用差分进化算法对控制器加权函数参数进行寻优,使控制器在满足约束条件下达到最优。仿真实验结果表明所提出方法在满足系统鲁棒性能的基础上,同时具备较好的控制输出,保证微电网频率在外部功率扰动和系统参数摄动情况下具有较好的动态性能。

H_2O_2浸种处理提高K_(326)烤烟种子活力的研究

通过对七份不同活力水平的 K3 2 6烤烟种子进行 H2 O2 浸种处理 ,并应用生理及生化指标对不同的处理结果进行了测定和分析。结果表明 :H2 O2 处理浓度为 0 .2 % ,浸种处理 K3 2 6烤烟种子 1天后 ,可提高中、低等活力水平 K3 2 6烤烟种子的活力 ,而对高活力的 K3 2 6烤烟种子活力则有轻微的抑制作用。这对快速鉴定烤烟种子质量及提高中。

时滞对离散H_∞滤波系统抗干扰性能的影响

研究了时滞离散系统的H∞滤波问题。通过引入增广向量,将时滞系统方程转化为不显含时滞的标准离散方程,并基于计算结构力学与最优控制之间的模拟理论,引入区段混合能的概念,采用扩展的Wittrick-Williams算法求解H∞滤波系统的抗干扰性能指标,进而得到时滞对滤波系统抗干扰性能指标的影响,并同时方便地完成了时滞滤波器的设计和滤波方程的求解。时滞H∞滤波器直接从时滞方程中得到,可保证系统的稳定性,是依赖于时滞的设计。

2-[2-(7H-二苯并[a，g]咔唑)-乙氧基]-乙基氯甲酸酯对脂肪胺类化合物的荧光标记及质谱鉴定

利用新型荧光标记试剂2-[2-(7H-二苯并[a,g]咔唑-乙氧基)-乙基氯甲酸酯作为柱前衍生化试剂,在Eclipse XDB-C8反相色谱柱上,采用梯度洗脱,实现了12种脂肪胺类化合物完全基线分离。检测最佳激发和发射波长分别为300和400 nm。通过荧光检测及离子阱大气压化学电离源(APCI Source)正离子模式实现了在线的柱后质谱鉴定。对土壤中脂肪胺类化合物的测定快速、准确,具有良好的重现性。荧光定量检测的回归系数大于0.9991;检出限为10.1～0.3 fmol。

2-D系统H∞输出反馈迭代学习控制器设计

针对2-D线性离散系统设计迭代学习控制器。首先,给出描述参考轨迹、初始状态、外界干扰等迭代变化参数的高阶内模。然后,聚合这些高阶内模得到增广的高阶内模并构造一种新的迭代学习控制器。针对非零边界条件和干扰的2-D Roesser模型,利用2-D分析方法提出其渐近稳定性。建立了适用于零边界条件和非零边界条件的迭代学习控制律设计准则以实现完美跟踪和2-D H∞性能,并提出了基于高阶内模的H∞输出反馈迭代学习控制器。针对控制器的求解问题,提出了两种不同的解法。最后,对一个初始温度、外界干扰迭代变化的化学反应过程的数值计算,表明了所提出的2-D控制器设计方法的有效性。

基于TCP动态网络系统模型的鲁棒H_∞控制

为了降低已有系统模型对回路时间的依赖,得出TCP网络系统的延时上界,通过引入变延时,利用线性矩阵不等式(LMI)设计了鲁棒H∞状态反馈控制器.采用Lyapunov函数方法验证了网络系统的稳定性,系统能够满足指定的H∞性能指标,并且减少延时和干扰对网络系统性能的影响;利用矩阵变换方法,将研究结果转化为具有线性矩阵不等式约束的凸优化形式,以便控制器的求解.通过算例仿真表明了所设计方法的有效性和可行性.

3H－1，2－二氢－2－（4－甲基苯胺基）甲基－1－吡咯里嗪酮在家兔体内主要代谢产物的研究

用高效液相色谱法对家兔单剂量ｉｇ７５０ｍｇ新抗炎镇痛剂３Ｈ－１，２二氢－２－（４－甲基苯胺基）－甲基－１－吡咯里嗪酮（Ｚ－４７）后尿中的代谢物进行了分离、检测。根据代谢物的色谱行为及与Ｚ－４７结构有关的其它药物的代谢途径，推测Ｚ－４７羧基衍生物［４－（３Ｈ－１，２－二氢－１－吡咯里嗪酮－２－甲基胺基）苯甲酸］是一可能的代谢产物，遂用化学方法合成了该衍生物。利用色谱保留值、紫外双波长吸收比值等对代谢物和标准品进行比较，并对尿样的酶水解产物进行色谱分析，证实Ｚ－４７羧基衍生物及其酯型β－Ｄ－葡糖苷酸结合物是Ｚ－４７在家兔体内的主要代谢产物。

具有随机丢包的非线性网控系统的鲁棒H_∞故障检测

针对具有模型不确定性和状态时滞的非线性网控系统,对它具有随机丢包的鲁棒H∞故障检测问题进行研究。采用动态故障检测滤波器构造残差产生器,将鲁棒H∞故障检测问题转化成H∞滤波器设计问题。所设计的鲁棒故障检测滤波器保证了故障检测系统均方渐近稳定且具有特定的H∞性能指标γ。数值仿真结果表明:利用该方法能够迅速准确地检测出系统的故障信号。