Water-Assisted Injection Molding System Based on Water Hydraulic Proportional Control Technique

Water-assisted injection molding（WAIM）, an innovative process to mold plastic parts with hollow sections, is characterized with intermittent, periodic process and large pressure and flow rate variation. Energy savings and injection pressure control can not be .attained based on conventional valve control system. Moreover, the injection water can not be supplied directly by water hydraulic proportional control system. Poor efficiency and control performance are presented by current trial systems, which pressurize injection water by compressed air. In this paper, a novel water hydraulic system is developed applying an accumulator for energy saving. And a new differential pressure control method is proposed by using pressure cylinder and water hydraulic proportional pressure relief valve for back pressure control. Aiming at design of linear controller for injection water pressure regulation, a linear load model is approximately built through computational fluid dynamics（CFD） simulation on two-phase flow cavity filling process with variable temperature and viscosity, and a linear model of pressure control system is built with the load model and linearization of water hydraulic components. According to the simulation, model based feedback is brought forward to compensate the pressure decrease during accumulator discharge and eliminate the derivative element of the system. Meanwhile, the steady-state error can be reduced and the capacity of resisting disturbance can be enhanced, by closed-loop control of load pressure with integral compensation. Through the developed experimental system in the State Key Lab of Fluid Power Transmission and Control, Zhejiang University, China, the static characteristic of the water hydraulic proportional relief valve was tested and output pressure control of the system in Acrylonitrile Butadiene Styrene（ABS） parts molding experiments was also studied. The experiment results show that the dead band and hysteresis of the water hydraulic proportional pressure relief valve are large, but the control precision and linearity can be improved with feed-forward compensation. With the experimental results of injection water pressure control, the applicability of this WAIM system and the effect of its linear controller are verified. The novel proposed process of WAIM pressure control and study on characteristics of control system contribute to the application of water hydraulic proportional control and WAIM technology.

Research on Electro Hydraulic Proportional Control for Heavy Vehicle Blend Braking System

A blend braking system of heavy vehicle was proposed.The main control part of the system is the electro hydraulic proportional servo valve.A nonlinear model of brake cylinder controlled by the valve was deduced through the analysis of its control property and system feature.The transfer function of the system was also proposed,and the hydraulic inherent frequency and the PID closed-loop system feature were calculated.The simulated result is consistent with those tested in the bench and on the site with 50 t heavy vehicle.The experimental result shows that the control method has quick response and high precision.

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.

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.

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.

STUDY ON PARISON CAD OF PLASTIC CONTAINER AND DESIGN FOR ITS CONTROL SYSTEM

Based on mechanics to design hollow plastic parison shape,this paper adopted computer and programmable logic controllers(PLCs) to build a three level system,finish the CAD of parison,and control the blow molding sequentially.Parison thickness was controlled by an electro hydraulic proportional control system,which controls the gap between the parison and the nozzle during the extrusion process by regulating the position of the core bar.Both constant pressure and speed control systems were adopted to control the process of plastic storing and extrusion,and PLC,such as C200H and CQM1,fuzzy modules were adopted.The results show that the part quality of blow molding can be improved greatly.

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。

农业机械电液控制技术发展现状及展望

电液控制技术作为农业机械关键技术之一,对于增强机械性能、提升操作便捷性和提高生产效率具有显著影响。综述了农业机械电液控制技术发展现状,通过具体案例,展示先进电液控制元件及系统在提升农业机械整体性能,特别是在模块化订制、智能化控制、电驱高效节能等方面的作用和潜力。未来以人工智能和物联网为代表的先进技术将与电液控制系统相结合,进一步推动农业机械向智能化和无人化方向发展。

面向喷浆机械臂电液比例控制系统的降噪处理研究

考虑到系统辨识数据的预处理能够提高喷浆机械臂电液比例控制系统的建模精度,采用小波变换滤波算法对采集的传感器数据进行滤波降噪处理。应用表明,在以sym5为小波基函数时,信噪比数值最大且均方根误差最小,降噪效果最好。滤波降噪结果能够为电液比例控制系统数学模型的精确辨识奠定基础。

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。

地下连续墙液压抓斗在粘壤土地层施工中偏斜角度分析

在液压抓斗进行地下连续墙施工过程中,斗体需要保持一定的垂直度以保证侧壁成槽精度。抓斗掘削部与土体相互作用时,作用于斗体上的载荷具有瞬态多向性且不均匀,由此导致钢丝绳下放的斗体发生偏斜,成槽壁面垂直度受到破坏。本文建立了液压抓斗多体动力学模型和粘壤土地层模型,通过多体动力学和离散元相结合的方法分析了液压抓斗在粘壤土地层施工过程中斗体倾斜情况,设计了电液比例调速回路以控制液压抓斗主液压缸运动,通过联合仿真重点讨论了主液压缸控制信号对斗体偏斜过程的影响,为进一步研究液压抓斗纠偏系统及控制策略提供依据。

基于Simulink电液比例位置控制系统的性能分析和优化

为改善某钢铁公司电液比例位置控制系统相关系统性能,文章使用数值计算分析方法,建立电液比例位置控制系统的数学模型,通过Simulink软件构建模型,并分析可知,系统的幅值裕度为25 dB,相位裕度为89.6°,结合伯德图的曲线特征,发现该系统的准确性与稳定性已满足基本要求,但通过系统的阶跃响应曲线,发现其上升时间为4.26 s、调整时间为5.83 s,系统响应的快速性没有达到要求。为进一步改进系统性能,选取结构简单、适用范围广的PID控制器,通过添加PID控制和不断修改PID控制器参数,优化系统性能,优化后的系统幅值裕度为5.18 dB,相位裕度90°,上升时间为0.236 s,调整时间为0.435 s,系统在保持良好的准确性和稳定性的基础上,快速性也得到了改善,已完全满足工业生产的要求。最后讨论了液压缸有效面积对PID控制性能的影响:A_(h)=0.15~0.20 m^(2)时系统性能仍有较好的适用性;小于0.15 m^(2)时会发生剧烈震动;大于0.20 m^(2)会大大增加响应时间。

变转速变排量双动力源泵阀协同电液系统特性分析

针对起重机阀控系统响应快但能耗大,泵控系统效率高但控制精度低的问题,提出了一种变转速变排量双动力源泵阀协同的多执行元件电液系统。首先,提出了一种多模式控制策略,即在单动作微动模式下,其中一个动力源卸荷,由于系统小流量时动态响应较慢,因此小流量时采用双变量模式控制系统,通过阀芯位置自适应调节和动力源的压力闭环控制,实现了流量精准匹配的目的;其次,在单动作快速运动模式下,双动力源合流驱动单执行元件,通过控制电液动力源相关参数,补偿了因负载变化引起的泵泄漏量,以实时控制执行元件速度;在复合快速运动模式下,双动力源分流单独驱动多执行元件,通过调节单个动力源的相关参数来实时控制各执行元件速度,以及实现系统流量比例分流的目的;然后,建立了系统AMESim-Simulink的联合仿真模型与试验平台;最后,对该系统在同一设定压差下的不同设定流量的控制特性进行了仿真和试验分析。研究结果表明:该系统能实现负载变化时对流量的补偿目的,并且该系统与定转速变排量泵阀协同液压系统相比,在单动作微动模式下的流量控制精度优化了约14.76%,动态响应时间减少了约0.12 s;在单动作快速运动模式下,流量变化减小了约6.21%,系统能耗降低约了13.94 kJ;在复合快速运动模式下,系统能耗降低了约50.31 kJ;同时,该系统比传统抗流量饱和负载敏感系统具有更好的流量稳定性。

基于电液比例技术的采煤机调高控制的优化设计及模拟

针对采煤机滚筒调高采用定量泵-换向阀,存在调节精确度、性能低等,优化设计采用电液比例采煤机调高液压系统,首先仿真分析开闭环PID调高控制,其能够实现滚筒轨迹的精确跟踪,且闭环PID控制特性明显优于开环控制;并在上述闭环PID调高控制基础上,仿真分析扰负载、过负载影响,结果表明:该调高系统可实现对干扰负载的忽略、过负载滚筒高度的自动调节。

绞车液压系统的设计及模拟

针对绞车控制系统依赖人工操作,存在稳定性差、协调性低的问题,设计了由滚筒加载系统、电液比例制动、驱动系统构成的绞车控制系统。当无辅助制动系统时,启动阶段的速度波动时间为4 s,且波动幅度大;当有辅助制动系统时,速度调整时间缩短为3 s,波动幅度小,速度跟踪性能好,且驱动与制动系统的协调配合性较好,整个运行阶段无突变且稳定,提高了绞车作业的可靠性。

谷物联合收获机底盘自动升降液压系统设计与试验

针对小型谷物联合收获机在丘陵区作业倾斜角度大、通过性差等问题,开展谷物联合收获机底盘自动升降液压系统设计与试验。本研究设计了底盘自动升降液压系统总体结构,对内置位移传感器液压缸、比例换向阀等关键部件进行设计和选型,提出了基于横向倾斜角度伸缩液压缸进行调平和升降的方法,采用自动调平控制和手动调平两种调平模式对底盘进行调平。应用AMEsim开展液压系统的仿真分析,发现换向时液压缸压力与流量稳定,位移速度平稳。设计了以PLC控制器和PID控制方法为核心的调平控制策略,通过调节液压缸长度实现对底盘的姿态调节,并开展静态调平试验。结果表明:比例换向阀开度范围为20%~45%时,能有效控制液压缸伸缩速度;调节时间随倾斜角度增加而增加,在倾斜角度7.7°范围内的总体调节误差低于0.5°,可满足谷物联合收获机对底盘横向调平的需求。该研究提出了依据横向偏角实现调平的液压系统和控制方法,为小型谷物联合收获机底盘调平液压系统设计提供参考。

一种电比例控制位移-流量反馈式控制阀

以流量控制阀为研究对象,针对流量控制阀负载控制稳定性差、流量变化大、易泄露的问题,基于Valvistor节流阀的原理,设计了一种电比例控制位移-流量反馈式控制阀,主要阐述了该流量控制阀的阀体结构和液压桥路原理。通过AMESim建立该流量控制阀的阀体和比例电磁铁模型,对其进行分析研究,分析结果表明,该流量控制阀在恒定电信号输入下,出口流量几乎不随负载变化,具有良好的稳定性和可控性,使系统对负载变化不敏感。

电液提升控制阀技术特点分析

系统分析了当前主流电液提升控制阀的技术特点及控制原理,阐述了电比例控制阀与数字阀的技术区别,为后期控制阀的设计开发提供了建设性意见。从工况需求层面分析了电液提升控制阀技术路线的内在发展规律,作为电液提升系统的核心元件,电液提升阀的发展路线即为电液提升系统的发展趋势,为液压系统的设计选型及整机发展路径提供参考。