Robust Nonlinear Current Sensorless Control of the Boost Converter with Constant Power Load

The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilizing controllers. A PWM-based current-sensorless robust sliding mode controller is developed that requires only the measurement of the output voltage. An extended state observer is developed to estimate a lumped uncertainty signal that comprises the uncertain load power and the input voltage, the converter parasitics, the component uncertainties and the estimation of the derivative of the output voltage needed in the implementation of the controller. A linear sliding surface is used to derive the controller, which is simple in its design and yet exhibits excellent features in terms of robustness to external disturbances, parameter uncertainties, and parasitics despite the absence of the inductor’s current feedback. The robustness of the controller is validated by computer simulations.

Communication Resource-Efficient Vehicle Platooning Control With Various Spacing Policies

Platooning represents one of the key features that connected automated vehicles may possess as it allows multiple automated vehicles to be maneuvered cooperatively with small headways on roads. However, a critical challenge in accomplishing automated vehicle platoons is to deal with the effects of intermittent and sporadic vehicle-to-vehicle data transmissions caused by limited wireless communication resources. This paper addresses the co-design problem of dynamic event-triggered communication scheduling and cooperative adaptive cruise control for a convoy of automated vehicles with diverse spacing policies. The central aim is to achieve automated vehicle platooning under various gap references with desired platoon stability and spacing performance requirements, while simultaneously improving communication efficiency. Toward this aim, a dynamic event-triggered scheduling mechanism is developed such that the intervehicle data transmissions are scheduled dynamically and efficiently over time. Then, a tractable co-design criterion on the existence of both the admissible event-driven cooperative adaptive cruise control law and the desired scheduling mechanism is derived. Finally, comparative simulation results are presented to substantiate the effectiveness and merits of the obtained results.

Research on Anti-Fluctuation Control of Winding Tension System Based on Feedforward Compensation

In the fiber winding process,strong disturbance,uncertainty,strong coupling,and fiber friction complicate the winding constant tension control.In order to effectively reduce the influence of these problems on the tension output,this paper proposed a tension fluctuation rejection strategy based on feedforward compensation.In addition to the bias harmonic curve of the unknown state,the tension fluctuation also contains the influence of bounded noise.A tension fluctuation observer(TFO)is designed to cancel the uncertain periodic signal,in which the frequency generator is used to estimate the critical parameter information.Then,the fluctuation signal is reconstructed by a third-order auxiliary filter.The estimated signal feedforward compensates for the actual tension fluctuation.Furthermore,a time-varying parameters fractional-order PID controller(TPFOPID)is realized to attenuate the bounded noise in the fluctuation.Finally,TPFOPID is enhanced by TFO and applied to control a tension control system considering multi-source disturbances.The stability of the method is analyzed by using the Lyapunov theorem.Finally,numerical simulations verify that the proposed scheme improves the tracking ability and robustness of the system in response to tension fluctuations.

Consensus Control With a Constant Gain for Discrete-time Binary-valued Multi-agent Systems Based on a Projected Empirical Measure Method

This paper studies the consensus control of multiagent systems with binary-valued observations.An algorithm alternating estimation and control is proposed.Each agent estimates the states of its neighbors based on a projected empirical measure method for a holding time.Based on the estimates,each agent designs the consensus control with a constant gain at some skipping time.The states of the system are updated by the designed control,and the estimation and control design will be repeated.For the estimation,the projected empirical measure method is proposed for the binary-valued observations.The algorithm can ensure the uniform boundedness of the estimates and the mean square error of the estimation is proved to be at the order of the reciprocal of the holding time(the same order as that in the case of accurate outputs).For the consensus control,a constant gain is designed instead of the stochastic approximation based gain in the existing literature for binary-valued observations.And,there is no need to make modification for control since the uniform boundedness of the estimates ensures the uniform boundedness of the agents’states.Finally,the systems updated by the designed control are proved to achieve consensus and the consensus speed is faster than that in the existing literature.Simulations are given to demonstrate the theoretical results.

Attribute-Based Access Control for Multi-Authority Systems with Constant Size Ciphertext in Cloud Computing

In most existing CP-ABE schemes, there is only one authority in the system and all the public keys and private keys are issued by this authority, which incurs ciphertext size and computation costs in the encryption and decryption operations that depend at least linearly on the number of attributes involved in the access policy. We propose an efficient multi-authority CP-ABE scheme in which the authorities need not interact to generate public information during the system initialization phase. Our scheme has constant ciphertext length and a constant number of pairing computations. Our scheme can be proven CPA-secure in random oracle model under the decision q-BDHE assumption. When user's attributes revocation occurs, the scheme transfers most re-encryption work to the cloud service provider, reducing the data owner's computational cost on the premise of security. Finally the analysis and simulation result show that the schemes proposed in this thesis ensure the privacy and secure access of sensitive data stored in the cloud server, and be able to cope with the dynamic changes of users' access privileges in large-scale systems. Besides, the multi-authority ABE eliminates the key escrow problem, achieves the length of ciphertext optimization and enhances the effi ciency of the encryption and decryption operations.

Variable Tension Control for Discontinuous Tape Winding of Composites Based on Constant Extension Ratio

Discontinuous tape winding, which has obvious advantages in large extension ratio winding, is widely used in the molding of composites. Therefore, the research on technological parameters becomes the focus of many scholars. However, how to accomplish the variable tension control is usually not fully considered. Accordingly, the constant extension ratio and the smoothness of winding process cannot be ensured. Aiming at the problem of tension control, this paper first gives a comparatively deep research on the control method and the interaction mechanism of tension, extension ratio, automatic lap and automatic rectification. Then, according to the winding process features, the mechanical device and the mathematical model of tension control system are established respectively. With regard to the characteristics of PID controller and fuzzy controller, the fuzzy self-tuning PID controller is designed. As a result, the variable tension control is realized during the winding and lapping process, and the constant extension ratio is guaranteed. Finally, a sample application is presented for demonstration. By presenting the variable tension control techniques for discontinuous tape winding, the constant extension ratio of tapes is achieved, the consecution and the automation degree of winding process is improved as well. Thus, the quality of wound products is guaranteed.

Constant Speed Control of Four-stroke Micro Internal Combustion Swing Engine

The increasing demands on safety, emission and fuel consumption require more accurate control models of micro internal combustion swing engine （MICSE）. The objective of this paper is to investigate the constant speed control models of four-stroke MICSE The operation principle of the four-stroke MICSE is presented based on the description of MICSE prototype. A two-level Petri net based hybrid mode/ is proposed to mode/ the four-stroke MICSE engine cycle. The Petri net subsystem at the upper level controls and synchronizes the four Petri net subsystems at the lower level. The continuous sub-models, including breathing dynamics of intake manifold, thermodynamics of the chamber and dynamics of the torque generation, are investigated and integrated with the discrete model in MATLAB Simulink. Through the comparison of experimental data and simulated DC voltage output, it is demonstrated that the hybrid model is valid for the four-stroke MICSE system. A nonlinear model is obtained from the cycle average data via the regression method, and it is linearized around a given nominal equilibrium point for the controller design. The feedback controller of the spark timing and valve duration timing is designed with a sequential loop closing design approach. The simulation of the sequential loop closure control design applied to the hybrid model is implemented in MATLAB. The simulation results show that the system is able to reach its desired operating point within 0.2 s, and the designed controller shows good MICSE engine performance with a constant speed. This paper presents the constant speed control models of four-stroke MICSE and carries out the simulation tests, the models and the simulation results can be used for further study on the precision control of four-stroke MICSE.

Structure modification and constant remelting speed control of a 120-t three-phase electroslag furnace

The traditional large electroslag remelting furnaces have many shortages,such as high short-network impedance and inductance,long maintenance time for electrode replacement,low stiffness of driveline,and low control accuracy of remelting speed.The present research was aimed to solve these problems through structure modification and constant remelting speed control for a 120-t electroslag remelting(ESR) furnace.Based on the technique of three-phase double electrodes in series,the short-network system and the structure of the 120-t ESR furnace were improved;and a continuous feeding system for the self-consumption electrode was proposed.A selfdesigned fully hydraulic driveline system with three degrees of freedom was successfully applied to the 120-t ESR furnace.An electrode auto-replacement system and the S-style speed-control curve of electrode-feeding system were designed on the basis of the soft measurement/sensing model on the remaining electrode length so as to obtain a high accuracy control system for constant remelting speed.The experiment products showed good surface quality and cross-sectional results,indicating good system control,and verifying the effectiveness of the structure modification of the furnace.

CONSTANT WORK-POINT CONTROL FOR PARALLEL HYBRID SYSTEM WITH CAPACITOR ACCUMULATOR IN HYDRAULIC EXCAVATOR

Limitations of various accumulators in hybrid hydraulic excavator are analyzed. A program using capacitor as the accumulator based on constant work-point control is put forward. A simulating experimental system of hybrid construction machinery is established, and experimental study on constant work-point control for parallel hybrid system with capacitor accumulator is carried out using the pressure and flow rate derived from boom cylinder of hydraulic excavator in actual work as the simulating loads. A program of double work-point control is proposed and proved by further experiments.

Study on geometric models of non-numerically controlled machining revolving cutter with constant pitch

This paper presents a new approach of designing the revolving cutter with constant pitch, and provides geometric models. The corresponding models in the non-numerically controlled manufacturing, such as designing the helical groove, grinding wheel, relative feeding motion, and calculating the helical angle of the cutting edge, are introduced. The examples are given to testify that the design approach is simple and readily realized in machining the revolving cutter with constant pitch. The effective design and manufacture method provides general references for non-NC machining revolving cutter with constant pitch and reducing the equipments input.

A LOCAL CONTROLLER BASED CONSTANT TENSION CONTROL SYSTEM

This paper is mainly about a local controller whose main function is to achieve the constant tension of the thin denier filament in the high speed winding process. A mathematic model of the induction motor while controlling its stator frequency and voltage is given. A new kind of variable parameter, real time constant tension control system is presented. The paper uses the microprocessor -INTEL 8097 as the CPU of the local controller. A standard serial communication interface-RS232 is used to communicate with the main computer. Computer simulation and experiment test show that this system has good control characteristics.

Application of Neural network PID Controller in Constant Temper-ature and Constant Liquid-level System

Guided by the principle of neural network, an intelligent PID controller based on neural network is devised and applied to control of constant temperature and constant liquidlevel system. The experiment results show that this controller has high accuracy and strong robustness and good characters.

Proportion Integration Differentiation(PID)Control Strategy of Belt Sander Based on Fuzzy Algorithm

Aiming at solving the problems of response lag and lack of precision and stability in constant grinding force control of industrial robot belts,a constant force control strategy combining fuzzy control and proportion integration differentiation(PID)was proposed by analyzing the signal transmission process and the dynamic characteristics of the grinding mechanism.The simulation results showed that compared with the classical PID control strategy,the system adjustment time was shortened by 98.7%,the overshoot was reduced by 5.1%,and the control error was 0.2%-0.5%when the system was stabilized.The optimized fuzzy control system had fast adjustment speeds,precise force control and stability.The experimental analysis of the surface morphology of the machined blade was carried out by the industrial robot abrasive grinding mechanism,and the correctness of the theoretical analysis and the effectiveness of the control strategy were verified.

Non-inverting buck-boost DC-DC converter based on constant inductor current control

The hysteresis control combined with PWM control non-inverting buck-boost was proposed to improve the light load efficiency and power density.The constant inductor current control(CICC)was established to mitigate the dependence on the external components and device variation and make smooth transition between hysteresis control loop and pulse width modulation(PWM)control loop.The small signal model was deduced for the buck and boost operation mode.The inductor current slope control(ICSC)was proposed to implement the automatic mode transition between buck and boost mode in one switching cycle.The results show that the converter prototype has good dynamic response capability,achieving 94%efficiency and 95%peak efficiency at full 10 A load current.

Centralized Solar PV Systems for Static Loads Using Constant Voltage Control Method

The alternative energy resources, like solar, are always complementary due to environmental changes. Energy generation with the sources such as solar and wind is gaining importance and of that photovoltaic conversion is the main focus of researches due to its promising potential as the electrical source. This paper presents the constant voltage method of control where the output of the converter is maintained constant irrespective of the variations in the irradiance with the high step-up isolated efficient single switch DC-DC converter for the solar PV systems. Constant voltage method of control uses the array of photovoltaic systems as its energy source. The output of the Solar PV systems is nonlinear and has its dependency on temperature and irradiance by which the panel voltage and current varies with the variation in irradiance. Constant voltage control method always operates in such a way that the converter voltage is tried to be maintained constantly to the reference voltage which is set by the user. The system used here utilizes high step single switch isolated DC-DC converter and monitors the voltage continuously by varying the duty cycle to maintain the converter voltage always constant. As a way of improving the performance, both the open and closed loop analysis is done where the closed loop analysis uses the PI controller for its performance. The model is implemented in MATLAB and it accepts the irradiance as the input and outputs the constant voltage from the converter and the feasibility of the proposed converter topology is confirmed with experimental results of the prototype model.

杭州国家版本馆恒温恒湿空调系统设计

介绍了恒温恒湿库房空调系统的设计,提出了可在库房建成初期、运行稳定期、战时等灵活切换的3种运行模式,分析了其各自的处理过程与节能性;给出了平、战时空调系统选择方案,提出了平时回收空气源热泵机组和冷水机组的冷凝热作为再热热源,战时利用新风预冷实现温湿度独立控制的方法;利用CFD模拟对室内气流组织进行了优化设计;提出了采用含湿量控制代替定露点法进行湿度控制和风机变频等控制策略。通过调试与运行,证明了各项设计措施在项目中应用的有效性。

抽油机井恒功率变频控制系统研究

抽油机作为陆上油田最重要的机械采油装备之一,近年来已发展出一系列的变频节能技术,但其研究主要集中在硬件方面,缺乏相关基础理论,导致现场应用普适性差,应用效果参差不齐。为此,研究有杆泵变频测控机理,优选了主要部件,对测试数据提出了要求,形成了有杆泵抽油变频控制系统。构建BP神经网络系统对正常井和漏失、柱塞碰泵、气体影响等异常井进行识别,分类提出变频计算模型:考虑负扭矩和抽油机冲次界限等建立了正常井恒功率变频计算模型,实例对比分析了变频后抽油机速度、加速度变化规律,产液量一定时,负功功率和有功功率分别下降了65%和44%。建立了上行程漏失的异常井变频计算模型,针对性地提高上行程冲次,形成“上快下慢”运行模式。实例计算表明:该系统缩短上行程时间2.6 s,较好地解决有杆泵上行程漏失和变频节能的问题。研究成果可为抽油机变频技术提供理论支持,对油田节能和提产具有指导意义。

基于外控恒压调速阀的垛式液压支架支柱承载特性分析

针对垛式液压支架降柱过程中立柱失速的问题,基于外控恒压调速阀改进平衡回路,研究立柱在负载作用下的承载特性。利用AMESim搭建液压支架平衡回路的仿真模型模拟立柱工作过程,分析外控恒压调速阀的结构参数对立柱承载特性及外控恒压调速阀阀口流量特性的影响。结果表明:立柱受到冲击时,安全阀开启卸荷;立柱下行时平衡回路作用防止立柱失速。减小外控恒压调速阀的阻尼孔直径与调控活塞面积可提高系统响应速度,平衡回路稳定性能提升,立柱承载特性得到改善。

一种改进的基于电网幅值跌落的SWISS整流器协调优化控制方法

SWISS整流器因其优越的性能被广泛应用于充电桩、分布式直流电源等场合。其首要的控制目标是维持稳定的直流侧输出电压、正弦且对称的交流侧三相电流以及网侧单位功率因数。然而,当电网出现幅值跌落时,基于传统的控制方法很难同时实现上述3个控制目标。因此,该文分别提出适用于电网幅值跌落的输出电压恒定控制(constant output voltage control,COVC)方法和电流正弦对称控制(sinusoidal and symmetrical current control,SSCC)方法。前者可实现直流侧输出电压恒定无波动,但无法实现网侧电流的正弦且对称。后者可实现网侧电流正弦且对称,但无法实现直流侧电压输出恒定无波动。在此基础上,该文结合这2种控制方法的优势进一步提出一种改进的协调优化控制(improved coordination and optimization control,ICOC)方法,可实现网侧处于单位功率因数的同时,在直流侧输出电压恒定无波动和网侧电流正弦且对称之间进行协调优化,实验结果证明ICOC方法相较于COVC和SSCC具有显著的优势,与该文的理论分析一致。

基于自抗扰控制的圆纬机恒张力输纱控制系统设计

针对当前圆纬机积极式送纱方式中存在的纱线张力及输送速度不可任意调节、纱线张力波动大等问题,提出了一种可为圆纬机输送恒定张力纱线的输纱控制系统。构建了以无刷直流电动机速度环为内环、以纱线张力为外环的纱线恒张力双闭环反馈控制系统,通过自抗扰控制技术获取纱线实时动态指标,并对无刷直流电动机目标转速进行调整,最后通过磁场定向控制技术驱动无刷直流电动机。详细阐述了纱线张力的形成机制、纱线恒张力输送控制方案、系统硬件设计及控制算法。输纱测试表明,该控制系统可实现多种类型纱线的恒定张力输送。其中,棉纱张力波动标准差为1.5 cN(300 m/min测试条件),氨纶包芯纱的张力波动标准差为0.33 cN(240 m/min测试条件)。输纱速度的调节范围为0~600 m/min,纱线张力的控制范围为2.0~50.0 cN。