Flow Control for a Two-Stage Proportional Valve with Hydraulic Position Feedback

The current research mainly focuses on the flow control for the two-stage proportional valve with hydraulic position feedback which is named as Valvistor valve.Essentially,the Valvistor valve is a proportional throttle valve and the flow fluctuates with the change of load pressure.The flow fluctuation severely restricts the application of the Valvistor valve.In this paper,a novel flow control method the Valvistor valve is provided to suppress the flow fluctuation and develop a high performance proportional flow valve.The mathematical model of this valve is established and linearized.Fuzzy proportional-integral-derivative(PID)controller is adopted in the closed-loop flow control system.The feedback is obtained by the flow inference with back-propagation neural network(BPNN)based on the spool displacement in the pilot stage and the pressure differential across the main orifice.The results show that inference with BPNN can obtain the flow data fast and accurately.With the flow control method,the flow can keep at the set point when the pressure differential across the main orifice changes.The flow control method is effective and the Valvistor valve changes from proportional throttle valve to proportional flow valve.For the developed proportional flow valve,the settling time of the flow is very short when the load pressure changes abruptly.The performances of hysteresis,linearity and bandwidth are in a high range.The linear mathematical model can be verified and the assumptions in the system modeling is reasonable.

Tri-state Modulation Power Driving of Electro-hydraulic Proportional Amplifier

Switch electro-hydraulic proportional amplifier（PA） widely employs single switch modulation power driving（SSMPD） or reverse discharging power driving（RDPD） at present. SSMPD has slow dynamic response, and can＇t adjust independently the dither signal＇s amplitude and frequency; RDPD accelerates the current decay; consequently, it increases current ripple and power loss. For the purpose of solving the above mentioned problem, the tri-state modulation power driving（TSMPD） scheme was proposed for improving the performance of power driving. Detailedly, the hardware circuit for the tri-state modulation power driving is designed; the tri-state modulation algorithm is realized by digital signal processor（DSP）. The tri-state modulation power driving is investigated by experiments, comparetive experiments among the single switch modulation power driving（SSMPD）, reverse discharging power driving（RDPD）, and the TSMPD are implemented, and the experimental results demonstrate that the linearity error of TSMDP meets the requirement of PA; the current response of TSMSP is the best; the amplitude of ripple current of the TSMPD can be reduced without increasing frequency of PWM, in addition, dither signal amplitude and frequency can be adjusted independently for each other. It is very meaningful to guide the development of high performance proportional amplifier for high frequency response proportional solenoid.

Investigation of Semi-Active Hydro-Pneumatic Suspension for a Heavy Vehicle Based on Electro-Hydraulic Proportional Valve

Hydro-pneumatic suspension is widely used in heavy vehicles due to its nonlinear characteristics of stiffness and damping. However, the conventional passive hydro-pneumatic suspension can’t adjust parameters according to the complicated road environment of heavy vehicles to fulfill the requirements of the vehicle ride comfort. In this paper, a semi-active hydro-pneumatic suspension system based on the electro-hydraulic proportional valve control is proposed, and fuzzy control is used as the control strategy to adjust the?damping force of the semi-active hydro-pneumatic suspension. A 1/4?semi-active hydro-pneumatic suspension model is established, which is co-simulated with AMESim and MATLAB/Simulink. The co-simulation results show that the semi-active hydro-pneumatic suspension system can significantly reduce vibration of the vehicle body, and improve the suspension performance comparing with passive hydro-pneumatic suspension.

Angular Position Controller and Its Design Model Verification for the Electro-Hydraulic Servo Control System

The angular position controller is system （EHSAS） to control the output of the rotary applied to electro-hydraulic servo actuator actuator. It works as a compensator based on the frequency response of the EHSAS. Its design model is verified on the state-space model of EHSAS by using simulation program SIMULINK. Real data used to test the system. Simulation results give a good agreement for the controller and also for the state-space model.

RESEARCH ON THE PERFORMANCE OF NEW TYPE OF PROPORTIONAL PESSURE AND FLOW CONTROL VALVE

A new closed loop flow controlling principle through correcting the valve'sopening area while load pressure is changing is carried out. Further more a principle using only oneproportional valve to compound control pressure and flow is suggested. By using very simpleproportional throttle valve in structure, the functions that five kinds of proportional valves orany two of them combined possess can be complimented. After analyzing, comparing, and testing thedynamic and static characteristics of valve with different controlling principles and main valvestructure styles, the optimized structure styles and control methods are achieved.

DYNAMIC CHARACTERISTICS OF LARGE FLOW RATING ELECTROHYDRAULIC PROPORTIONAL CARTRIDGE VALVE

A kind of cartridge servo proportional valve is discussed, which can be used for controlling large flow rate with high performance. By analyzing the structure principle of the valve, the transfer fimction of the valve is derived. With the transfer function, some structure elements that may affect its performance are investigated. Through the numerical simulation and test study, some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The test results conform to the results of the theoretical analysis and simulation, which proves the correctness of the study and simulation works. The paper provides theoretical basis for engineering applications and series expanding design works

ROBUST CONTROL OF AN ELECTROHYDRAULIC PROPORTIONAL SPEED CONTROL SYSTEM WITH A SINGLEROD HYDRAULIC ACTUATOR

A robust control algorithm is proposed to focus on the non-linearity and parameters＇ uncertainties of an electro-hydraulic proportional speed control system （EHPSCS） with a single-rod hydraulic actuator. The robust controller proposed does not need to design stable compensator in advance, is simple in design and has large scope of uncertainty applications. The feedback gains of the robust controller proposed are small, so it is easily implemented in engineering applications. Experimental research on the speed control under the different conditions is carried out for an EHPSCS. Experimental results show that the robust controller proposed has better robustness subject to parametric uncertainties, and adaptability of parameters＇ variation of control system itself and plant parameter variation.

高压阀口液动力补偿控制策略仿真分析

直动式比例伺服阀是一种新型的单级伺服阀,采用比例电磁铁或线性力马达直接驱动滑阀运动,具有成本低、频响高、抗污染能力强等优点,广泛应用于注塑机进给控制、轧机板厚控制系统等高速高精度液压控制系统中。传统的直动式比例伺服阀采用PID控制策略实现阀芯的精确位置控制,在高压大流量工况下(供油压力达到20 MPa、流量大于100 L/min),阀芯受到液动力扰动变得更加剧烈,易出现响应速度慢、阀芯抖动的现象,影响了比例伺服阀的控制精度。为了解决大液动力扰动的问题,提出了一种基于指数收敛干扰观测器的滑模控制器。通过建立阀芯动力学模型来设计滑模控制器,保证阀芯位置的高动态跟踪性能;使用基于指数收敛的干扰观测器,估计阀芯动力学模型中液动力的不确定性扰动,解决高压大流量工况下的阀芯液动力扰动补偿问题。搭建了比例伺服阀系统的联合仿真模型进行仿真验证,结果表明,提出的控制器可以解决高压大流量工况下阀芯液动力扰动对阀芯位置控制的干扰问题。

基于时间差法的位置灵敏3He正比计数管位置分辨性能研究

中子定位技术可用于乏燃料后处理流程监测,以避免发生核临界安全事故。利用蒙特卡罗(Monte Carlo,MC)算法模拟了不同中子发射方式、^(3)He气压、管径、慢化体厚度等对位置灵敏^(3)He正比计数管位置分辨能力和探测效率的影响。对于管径为2.54 cm、灵敏区长80 cm、^(3)He气压为405300 Pa的位置灵敏^(3)He正比计数管,MC模拟结果表明:轴向各处位置分辨能力相同,对热中子点源的位置分辨极限为0.17 cm;慢化体厚5 cm且^(244)Cm源紧贴慢化体外壁时中子探测效率为3.0%,位置分辨为9.25 cm。用时间差法测试了^(244)Cm源在灵敏区不同位置、源管距、慢化体厚度等情况下此位置灵敏^(3)He正比计数管对^(244)Cm源的位置分辨能力与探测效率,测试结果表明:实验装置的理论位置分辨极限可达2.64 cm,当慢化体厚5 cm且^(244)Cm源紧贴慢化体外壁时位置分辨为18.50 cm,为理论值的一半。

三自由度液压机械臂自动整平系统设计与研究

针对水下抛石基床整平需求,设计一套基于挖掘机三自由度液压机械臂的自动整平系统。对臂架机械结构进行适应性改造,通过试验计算其作业负载,结合有限元法验证改造结构的可靠性。基于D-H法和几何法搭建臂架正、逆运动学模型,将铲尖轨迹运动转换为臂架各构件的协同控制。设计基于PID控制的臂架电液比例位置控制系统,通过AMESim验证了臂架驱动控制系统方案的可行性。结合北斗定位技术,搭建臂架自动整平系统架构,提出适用于工程应用场景的定位、整平作业流程。最后,通过工程试验和应用对自动整平系统进行了验证。试验和应用结果表明:采用三自由度液压机械臂的基床整平效率更高、成本更低,整平精度也满足施工要求。

基于Cornell的自适应电离层闪烁强度的模型研究

针对Cornell模型在同一闪烁条件下,数据更新周期越长,估计和模型输入的幅度闪烁指数S4的偏差越大,并随着电离层闪烁的增强而增强的问题,提出基于Cornell模型的自适应S4的电离层闪烁模型即AS4-Cornell模型。模型以S4的偏差作为BP(back propagation)神经网络比例积分微分(proportional integral derivative,PID)算法的反馈,自动调整输入的复高斯白噪声的区段权值,使最终产生的闪烁信号满足模型输入的闪烁指数S4的指标。结果表明:仿真时,AS4-Cornell模型的幅度和相位闪烁序列概率分布均符合电离层闪烁理论,估算得到的电离层幅度指数S4与模型输入S4指数的最大偏差为0.001;全球定位系统(global positioning system,GPS)电离层闪烁模拟器测试时,AS4-Cornell模型估算得到的电离层幅度指数S4与模型输入S4指数的最大偏差为0.09;相比Cornell模型,AS4-Cornell模型产生的电离层闪烁信号更能够很好地反映模型输入的电离层闪烁指数S4的强度。

基于RBF神经网络整定PID的电液比例系统位置控制研究

针对凿岩机械臂的电液比例系统位置控制精度问题,提出了一种基于径向基函数(RBF)神经网络整定PID的电液比例系统位置控制方法。首先,在AMESim中搭建了阀控非对称液压缸的电液比例系统简化模型,设置了各个模块的参数;然后,利用MATLAB/Simulink搭建了系统闭环控制模型,通过不断更新RBF网络模型并修正PID参数,实现了基于RBF神经网络整定PID的电液比例系统位置控制目的;结合AMESim搭建的电液比例系统模型和Simulink下搭建的控制器进行了联合仿真;最后,基于凿岩台车机械臂实验平台,进行了电液比例系统位置控制实验。仿真结果表明:在受到外部干扰的情况下,RBF神经网络整定PID控制系统能够在0.3 s内控制活塞杆重新运行至目标位置,平均响应时间为1.5 s,位置精度误差不超过5 mm。实验结果表明:与常规PID控制方法相比,RBF神经网络整定PID控制活塞杆位置精度误差降低了75%,位置精度误差在工程实际要求的10 mm范围以内,因此,RBF神经网络整定PID算法可以有效提高电液比例系统的位置控制精度,满足凿岩机械臂实际工作中对电液比例系统位置精度的控制要求。

基于面积差异等效建模的电液比例位置系统FMAPID控制

公路边坡护坡骨架施工车是聚焦于公路边坡土壤开槽和水泥混凝土滑模的工程机械装备。针对公路边坡护坡骨架施工车旋转臂在边坡环境的运动控制问题,设计一种基于模糊多参数自适应比例积分微分(proportional integral derivative,PID)的位置反馈控制策略。考虑到非对称液压缸两腔的差异,采用面积差异等效建模法建立阀控非对称液压缸的线性数学模型。通过定义模糊子集、选取隶属函数、建立模糊规则,使用模糊多参数自适应PID控制算法,实现旋转臂非对称液压缸位置控制。仿真和试验结果表明,基于面积差异等效数学模型的模糊多参数自适应PID能够有效地提高液压缸位置跟踪控制精度,验证了所提控制算法的有效性。

Position Control of Electro-hydraulic Actuator System Using Fuzzy Logic Controller Optimized by Particle Swarm Optimization

The position control system of an electro-hydraulic actuator system （EHAS） is investigated in this paper. The EHAS is developed by taking into consideration the nonlinearities of the system： the friction and the internal leakage. A variable load that simulates a realistic load in robotic excavator is taken as the trajectory reference. A method of control strategy that is implemented by employing a fuzzy logic controller （FLC） whose parameters are optimized using particle swarm optimization （PSO） is proposed. The scaling factors of the fuzzy inference system are tuned to obtain the optimal values which yield the best system performance. The simulation results show that the FLC is able to track the trajectory reference accurately for a range of values of orifice opening. Beyond that range, the orifice opening may introduce chattering, which the FLC alone is not sufficient to overcome. The PSO optimized FLC can reduce the chattering significantly. This result justifies the implementation of the proposed method in position control of EHAS.

Quantitative feedback controller design and test for an electro-hydraulic position control system in a large-scale reflecting telescope

For the primary mirror of a large-scale telescope, an electro-hydraulic position control system(EHPCS) is used in the primary mirror support system. The EHPCS helps the telescope improve imaging quality and requires a micron-level position control capability with a high convergence rate, high tracking accuracy, and stability over a wide mirror cell rotation region. In addition, the EHPCS parameters vary across different working conditions, thus rendering the system nonlinear. In this paper, we propose a robust closed-loop design for the position control system in a primary hydraulic support system. The control system is synthesized based on quantitative feedback theory. The parameter bounds are defined by system modeling and identified using the frequency response method. The proposed controller design achieves robust stability and a reference tracking performance by loop shaping in the frequency domain. Experiment results are included from the test rig for the primary mirror support system, showing the effectiveness of the proposed control design.

Testing for a Zero Proportion

Tests for a proportion that may be zero are described. The setting is an environment in which there can be misclassifications or misdiagnoses, giving the possibility of nonzero counts from false positives even though no real examples may exist. Both frequentist and Bayesian tests and analyses are presented, and examples are given.

基于PID的陆区航路纵向碰撞风险控制

为提高陆区航路运行的安全性,减少间隔冲突隐患,仿真研究陆区航路纵向碰撞风险,首先,基于位置误差理论建立陆区航路的纵向碰撞风险数学模型,综合考虑飞行员干预时间,使用安全目标水平反推,确定航空器运行安全区域的前后边界;然后,使用Matlab软件的System Identification工具箱拟合辨识快速存取记录器(QAR)数据,得到反映发动机推力手柄角度和速度变化对应关系的传递函数,依此设计比例、积分与微分(PID)控制系统,将航空器纵向间隔控制在安全区域内;最后,使用Simulink搭建控制系统进行仿真,以验证控制系统功能。结果表明:在给定航路流量(50架/h)条件下,该控制系统能够实时计算2机纵向安全间隔范围(3326~16674 m),并在产生间隔冲突时于70 s内将前后机间隔调整至标称值。PID控制系统能够将碰撞风险始终维持在安全目标水平之上,提高航空器运行的安全性。

基于强化学习的液动节流阀阀位控制策略

控压钻井是一种复杂的钻井工艺,自动节流管汇上节流阀的控制是实现井底压力精确控制的关键技术。首先,建立控压钻井装置中液动节流阀的动态模型,该节流阀采用比例伺服阀作为液压调节元件,采用控制器控制比例伺服阀的阀芯移动改变液动节流阀液压缸中液压油的流入量,进而实现对液动节流阀阀位的控制。其次,提出一种基于深度强化学习的液动节流阀阀位控制策略,该策略利用DQN(Deep Q-Network)算法,通过液动节流阀和智能体相互交换过程中学习比例伺服阀对液动节流阀阀位的控制。最后,通过仿真和现场试验验证了阀位控制策略的有效性,为成功实施控压钻井提供了保障。

模糊PID控制下的CSPRs配对进近纵向碰撞风险

为控制近距离平行跑道(CSPRs)配对进近的纵向碰撞风险,提高该程序的运行安全,首先,基于快速存取记录器(QAR)数据分析航空器在进近过程中的速度变化特征,拟合其在进近阶段的定位误差分布;其次,考虑前机的尾流影响,建立基于位置误差的配对进近纵向碰撞风险模型,计算得到前后机的最优纵向间隔;然后,使用Matlab的System Identification工具箱,拟合辨识发动机推力手柄角度和飞机速度变化的相关数据,得到其对应关系的传递函数,根据该函数设计模糊比例、积分、微分(PID)控制系统,通过控制前后机间的纵向间隔使碰撞风险维持在最低值;最后,使用Simulink仿真验证该控制系统。结果表明:模糊PID控制系统在响应时间、超调量、稳定性等方面的表现皆优于传统的PID控制系统,该模糊PID系统能在50 s内将前后机的纵向碰撞风险控制在最低值(1.72×10-38次事故/飞行小时),并且在整个配对程序的实施过程中维持该值。

持续正压通气治疗对阻塞性睡眠呼吸暂停合并胃食管反流患者的疗效观察研究

背景胃食管反流病(GERD)、阻塞性睡眠呼吸暂停(OSA)均是临床常见疾病,且患病率逐年上升。持续正压通气(CPAP)能否在改善OSA的同时改善GERD目前仍存在争议。目的探究CPAP对于OSA合并GERD患者的疗效。方法选取2020年9月—2023年1月就诊于北京大学人民医院老年科及呼吸内科的OSA合并GERD患者169例为研究对象。收集患者的一般资料并定期随访,随访终点为GERD缓解或治疗8周,排除无治疗依从性者。按是否服用质子泵抑制剂(PPI)将患者分为无PPI者与有PPI者,再按照是否进行CPAP治疗将无PPI者分为CPAP组(n=43)与无治疗组(n=53),有PPI者分为CPAP+PPI组(n=32)与PPI组(n=41)。采用Kaplan-Meier法绘制CPAP组与无治疗组、CPAP+PPI组与PPI组GERD缓解率的生存曲线,Log-rank检验比较其差异。采用多因素Cox比例风险回归模型分析探究CPAP对OSA合并GERD患者GERD缓解的影响。结果CPAP组中位缓解时间为6周,无治疗组为7.5周,CPAP组累积GERD缓解率高于无治疗组(χ^(2)=4.182,P=0.041);CPAP+PPI组中位缓解时间为3.9周,PPI组为6.1周,CPAP+PPI组累积GERD缓解率高于PPI组(χ^(2)=14.333,P<0.001)。多因素Cox比例风险回归模型分析结果显示,CPAP是未使用PPI的OSA合并GERD患者GERD缓解的影响因素〔HR=2.360,95%CI(1.044,5.338),P<0.05〕;CPAP是使用PPI的OSA合并GERD患者GERD缓解的影响因素〔HR=6.123,95%CI(2.562,14.635),P<0.05〕。结论CPAP治疗可改善OSA合并GERD患者的GERD症状,CPAP+PPI治疗GERD效果优于单纯使用PPI。