5-Aminolevulinic acid against strawberry Fusarium wilt:Bidirectional regulation of biocontrol agents and pathogens

Strawberry Fusarium wilt (SFW) is a systematic soil-borne disease caused by Fusarium oxysporum f.sp.fragaria (Fof),which infects the vascular bundles,blocking water and nutrient transport from roots to the aboveground.It is a severe pathogen which spreads rapidly and destroys strawberry production.Finding a way to control this disease is of great scientific value and practical importance.In this study,three fungi were isolated from the vascular tissues of sick strawberries in the field.After DNA sequencing,they were identified as Fof,Aspergillus fumigatus and Trichoderma harzianum,respectively,among which the first two are pathogens and the third is a probiotic.All fungi were controlled by thiophanate-methyl (TM),a commercial fungicide.On PDA medium,20 mg·L^(-1)5-aminolevulinic acid (ALA),a natural non-protein amino acid,promoted T.harzianum proliferation,but inhibited Fof and A.fumigatus.In confrontation test,the growth of Fof or A.fumigatus was inhibited by T.harzianum and exogenous ALA promoted T.harzianum growth but significantly inhibited the pathogen growth.When three species of fungi were separately or combinedly inoculated on healthy strawberry plants,T.harzianum promoted plant growth and development while Fof or A.fumigatus caused growth retardation,where Fof directly caused leaf yellowing and plant wilting.When the plants inoculated with different fungus were treated with ALA,the results turned out that ALA alleviated SFW symptoms by bidirectionally promoting T.harzianum proliferation and inhibiting Fof and A.fumigatus.Thus,ALA might be used in comprehensively controlling SFW in strawberry industry.

Start-up phase plasma discharge design of a tokamak via control parameterization method

The tokamak start-up is a very important phase during the process to obtain a suitable equalizing plasma, and its governing model can be described as a set of nonlinear ordinary differential equations（ODEs）. In this paper, we first estimate the parameters in the original model and set up an accurate model to express how the variables change during the start-up phase, especially how the plasma current changes with respect to time and the loop voltage. Then, we apply the control parameterization method to obtain an approximate optimal parameters selection problem for the loop voltage design to achieve a desired plasma current target. Computational optimal control techniques such as the variational method and the costate method are employed to solve the problem, respectively. Finally, numerical simulations are performed and the results obtained via different methods are compared. Our numerical parameterization method and optimization procedure turn out to be effective.

船舶永磁同步推进电机的优化I/f起动控制方法

为解决高转矩与高转动惯量的船舶推进电机在开环I/f控制中转速和转矩波动大、电机易失步、效率低的问题,提出一种I/f控制改进方法。通过建立转矩角观测器,调节给定电流矢量的幅值,使其跟随负载转矩变化,提高系统鲁棒性。同时,将电机运行状态推进至接近最大转矩电流比状态,提高电机的运行效率;通过瞬时有功功率调节电流矢量的角速度,降低电磁转矩波动,加快电机的转速收敛过程。最后,在Matlab/Simulink中进行仿真实验,实验结果表明该方法可以显著提高推进电机运行效率和稳定性。

Transient Air-Fuel Ratio Control in a CNG Engine Using Fuzzy Neural Networks

The fuzzy neural networks has been used as means of precisely controlling the air-fuel ratio of a lean-burn compressed natural gas (CNG) engine. A control algorithm, without based on engine model, has been (utilized) to construct a feedforward/feedback control scheme to regulate the air-fuel ratio. Using fuzzy neural networks, a fuzzy neural hybrid controller is obtained based on PI controller. The new controller, which can adjust parameters online, has been tested in transient air-fuel ratio control of a CNG engine.

Poloidal Field Control for the HT-7U Super-conducting Tokamak

Controlling the poloidal field (PF) in the HT-7U superconducting tokamak is critical to the realization of the mission of advanced tokamak research. Plasma start-up, plasma position, shape, current control and plasma shape reconstruction have been performed as a part of its design process. The PF coils have been designed to produce a wide range of plasmas. Plasma start-up can be achieved for multiple conditions. Fast controlling coils for plasma position inside the vacuum vessel are used for controlling the plasma vertical position on a short timescale. The PF coils control the plasma current and shape on a slower timescale. VXI (VME bus extensions for Instrumentation) Bus system and DSP (Digital Signal Processor is a basic unit of the feedback control system), the response time of which is about (2-4) ms. The basic unit of this system, the shape-controlling algorithms of a few critical points on plasma boundary and real-time equilibrium fitting (RTEFIT) will be described in this paper.

Interval Type-2 Fuzzy Hierarchical Adaptive Cruise Following-Control for Intelligent Vehicles

Intelligent vehicles can effectively improve traffic congestion and road traffic safety.Adaptive cruise followingcontrol(ACFC)is a vital part of intelligent vehicles.In this paper,a new hierarchical vehicle-following control strategy is presented by synthesizing the variable time headway model,type-2 fuzzy control,feedforward+fuzzy proportion integration(PI)feedback(F+FPIF)control,and inverse longitudinal dynamics model of vehicles.Firstly,a traditional variable time headway model is improved considering the acceleration of the lead car.Secondly,an interval type-2 fuzzy logic controller(IT2 FLC)is designed for the upper structure of the ACFC system to simulate the driver's operating habits.To reduce the nonlinear influence and improve the tracking accuracy for the desired acceleration,the control strategy of F+FPIF is given for the lower control structure.Thirdly,the lower control method proposed in this paper is compared with the fuzzy PI control and the traditional method(no lower controller for tracking desired acceleration)separately.Meanwhile,the proportion integration differentiation(PID),linear quadratic regulator(LQR),subsection function control(SFC)and type-1 fuzzy logic control(T1 FLC)are respectively compared with the IT2 FLC in control performance under different scenes.Finally,the simulation results show the effectiveness of IT2 FLC for the upper structure and F+FPIF control for the lower structure.

The Main Diseases and Control Measures of Panax notoginseng(Burk) F. H. Chen in Wuzhou City

The main symptoms of root rot,anthracnose,blight and damping-off of Panax notoginseng( Burk) F. H. Chen are introduced in the paper,and the corresponding control measures are elaborated from the aspects of agricultural management measures,seed disinfection,seedbed treatment and chemical control.

Identification of Biocontrol Strain HJX1 and Determination of Its Antifungal Spectrum

A biocontrol strain HJX1,which had good inhibitory effect against Fusarium oxysporum f. sp. cubense,was identified as Bacillus subtilis based on traditional morphology,16 S rRNA gene sequence and fatty acid profiles. The sequence of 16 S rRNA gene had 99% homology to B. subtilis according to the DNA fragment of 1 521 bp amplified with a pair of universal primers,P0 and P6,of bacteria. Confront culture with pathogenic fungi showed that this strain had good inhibitory effect against 10 pathogenic fungi.

Novel approach to harmonic control for Class F power amplifier with high power added efficiency

This paper presents a new topology to implement Class F power amplifier for eliminating the on-resistance (R_(ON))effect.The time-domain and frequency-domain voltage and current waveforms for Class F amplifier are ana- lyzed using Fourier series analysis method.Considering the on-resistance effect,the formulas of the efficiency,output power,dc power dissipation,and fundamental load impedance are given from ideal current and voltage waveforms.For experimental verification,we designed and implemented a Class F power amplifier,which operates at 850 MHz using MGaAs/GaAs Heterostructure FET(HFET)device,and analyzed the measurement results.Test results show that the maximum PAE of 67% can be achieved at 28 dBm output power level.

Adaptive Neuro-fuzzy Controller Design for Non-affine Nonlinear Systems

An adaptive neuro-fuzzy control is investigated for a class of non-affine nonlinear systems.To do so,rigorous description and quantification of the approximation error of the neuro-fuzzy controller are firstly discussed.Applying this result and Lyapunov stability theory,a novel updating algorithm to adapt the weights,centers,and widths of the neuro-fuzzy controller is presented.Consequently,the proposed design method is able to guarantee the stability of the closed-loop system and the convergence of the tracking error.Simulation results illustrate the effectiveness of the proposed adaptive neuro-fuzzy control scheme.

Screening of Bacillus subtilis HAAS01 and Its Biocontrol Effect on Fusarium wilt in Sweet Potato

Fusarium wilt,a disease caused by Fusarium oxysporum f.sp batatas(Fob)is an important disease in sweet potato production.Using endophytic bacteria for biological control of sweet potato diseases is one of the important ways.A Bacillus subtilis with antagonistic effect on Fusarium wilt of sweet potato was isolated from soil by confrontation culture.According to the biological characteristics,16S rDNA sequence analysis,and physiological and biochemical analysis,the Bacillus subtilis HAAS01 was named.A pot experiment was conducted for the biological control experiment of strain HAAS01,and the endogenous hormone content,antioxidant enzyme activity,soluble protein content,and related gene expressions of sweet potato plants were detected.The results showed that the HAAS01 strain could promote the production of endogenous hormones and resist the infection of plant diseases together with defensive enzymes and upregulation of related gene expressions.In summary,Bacillus subtilis HAAS01 was effective in controlling Fusarium wilt of sweet potato and has potential for application and development.

双U/f下垂控制下双极MMC-HVDC系统交流阻抗建模及稳定性分析

基于模块化多电平换流器的高压柔性直流输电系统(modular multilevel converter-based high voltage direct current,MMC-HVDC)常采用双极接线方式以提高系统功率输送能力和可靠性。然而目前对于风电场经柔直外送系统的稳定性研究集中于单极接线方式,孤岛直驱风电场与采用不同双极协调控制的双极MMC-HVDC互联系统小信号稳定性问题还有待进一步探究。该文首先考虑频率耦合特性、参考系初相位和直流侧耦合特性的影响,分别建立了采用双U/f下垂控制和定U/f-P/Q控制的双极MMC-HVDC系统交流侧等效SISO阻抗模型,并详细分析了金属回线阻抗和双极间功率均分度对交流阻抗特性的影响。接着对比研究了两种协调控制中共有控制环路和特有控制环路对交流侧负电阻特性及互联系统稳定性的影响规律。最后,孤岛直驱风电场经两种双极协调控制下双极MMC-HVDC外送系统Matlab/Simulink时域仿真结果和硬件在环半实物实时仿真实验结果验证了所提出的小信号阻抗模型的精确性和稳定性分析结论的有效性。

基于模糊解耦策略的小型注塑机料筒温度F-PI复合控制器

在塑料产品的生产过程中,注塑机料筒温度的响应速度和稳定性对最终塑料产品的质量具有重要影响。为了提高小型注塑机料筒温度的控制精度,针对料筒具有的惯性大、非线性、大滞后、强耦合等温度特性,在模糊控制不能满足控制要求的背景下,提出了基于相邻加热段之间温差的模糊解耦策略,通过利用相邻加热段之间的温差信息,建立模糊解耦控制器,对各段料筒之间的温度耦合进行解耦控制。实验结果表明,该控制方法效果良好,达到目标温度所用时间为1092 s,最大超调量只有3%,但稳态性能较差。为解决稳态性能较差的问题,在模糊解耦的基础上建立F-PI复合控制器,通过引入积分环节消除系统在稳态下的偏差。在Matlab/Simulink环境下进行仿真并在注塑机上进行验证,结果表明,F-PI复合控制方法不仅具有良好的动态响应,还具有更高的稳态精度,稳态偏差仅为±1℃。因此基于模糊解耦策略的F-PI复合控制方法不仅能对料筒的温度耦合进行解耦控制,还有效提高了系统的稳定性和控制精度,具有良好的鲁棒性。

The Application of Microcontroller and PID Technology on the Control of Motor Drive

This paper describes the incremental PID control algorithm and the basic principles of motor soft start, and introduced STM32F103RB8 basic performance microcontroller, combined with incremental PID control advantages, and gives MCU in motor soft start process control application. Practice shows that the incremental PID applications, simplifying the control ideas to improve the performance of the current loop control, limiting the starting current, smooth start-up speed, and achieved good results motor start.

基于I/F启动的PMSM无感复合控制方法

针对永磁同步电机全速域无位置传感器控制,电机起动时观测器位置估算困难的问题。提出一种电流频率比结合龙伯格观测器的无位置传感器控制策略。首先,在低速域中,采用I/F控制启动;在中高速域,引入龙伯格观测器和锁相环进行位置估计。其次,针对两种控制方法之间直接过渡导致的振荡问题,本文提出了新型平滑过渡策略;对于PI调节器存在协调性与抗干扰能力差的问题,引入自抗扰控制并与新型平滑过渡策略相结合,进一步形成一种复合过渡法;最后经过Simulink和电机实验平台的验证,仿真和实验结果显示,复合控制方法过渡过程平稳并且转速超调和误差明显减小。

基于双MPC与变斜率I/f的SPMSM快速启动控制策略研究

为了表贴式永磁同步电机(SPMSM)快速启动应用,针对现有恒流频比控制(I/f)启动采用固定参考斜率导致启动慢以及后续投切为双PI闭环磁场定向控制(FOC)策略动态响应能力不足的问题,提出一种内、外环均采用模型预测控制(MPC)策略的SPMSM变斜率I/f(DI/f)启动控制策略。首先通过模型预测推算出下一时刻的转子位置、转速。其中转速用于估算负载转矩,转子位置等效为变斜率I/f启动中的动态参考频率,构成变DI/f启动。当电机转速达到设定转速后,系统自动投切为双闭环MPC控制。模型预测转速外环通过当前转速与估算负载计算下一时刻q轴电流的额定值,实现启动到稳态的平稳快速切换。仿真与实验结果验证该算法的可行性与有效性,并使永磁同步电机的启动上升时间缩短了41.9%,调节时间缩短了41.1%。

UHF波段功率放大器设计

为某UHF波段的发射机设计一款己类功率放大器,工作于频段430~455 MHz,介绍了谐波控制和匹配网络的设计。在放大器输出匹配网络前添加谐波控制电路,通过对晶体管漏极的谐波控制生成己类放大器的工作波形。同时,在输入、输出阻抗是复阻抗的情况下,使用简化实频技术对电路进行匹配,提高了匹配网络的效率。测试结果显示,该放大器输出功率达60 dBm,对应的增益为20 dB,PAE为79%,达到设计要求。

Siemens DP／PA Link模块在ABB Control Builder F平台中的组态

在现场总线控制系统中，现场仪表可通过Profibus—DP／PALink模块挂接到Profibus总线上。本文详细介绍在ABB的Freelance 800 F DCS系统及其Control Builder F软件平台中，如阿通过西门子的Siemens DP／PA Link模块来组态PA仪表的步骤。

一种改善VVVF变频调速系统稳定性方法

针对异步电机运行在V／f控制方式下空载或者轻载时容易出现电流畸变振荡甚至系统不稳定现象,在功率控制原理基础上,提出了一种改善V／f控制交流传动系统稳定性的控制方法。通过深入分析系统不稳定时电机输入功率和电流之间的变换关系,在定子电压矢量定向坐标系中采用了一个频率补偿器的方法来动态调整频率,以达到抑制电流振荡的目的,保持系统的稳定性。该方法在通用的变频调速装置上仅仅由软件实现,不需要额外的硬件成本。仿真和试验结果表明,该控制方法能有效抑制电流和速度振荡,明显改善系统的稳定性。

基于遗传算法的P-F-PI控制器在机器人手臂定位控制中的应用

提出用遗传算法来优化控制参数的P F PI(比例 模糊 比例积分 )控制器 ,控制机器人手臂定位系统 .P F PI控制器是在大偏差时用比例控制 ,在中偏差时用F控制 ,接近稳态时用PI控制 ,而这三个控制器的切换参数以及F控制器中的修正系数用遗传算法来优化 .实验证明 ,该控制方法能满足机器人手臂定位控制动态和静态要求 .