Switching Frequency Improvement of a High Speed on/off Valve Based on Pre-excitation Control Algorithm

The high-speed on/off valve(HSV)serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems.As the switching frequency of the HSV increases,the properties of the generated discrete fluid approach those of continuous fluids.Therefore,a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems.However,the current research mainly focuses on its dynamic performance,but neglect its FRC.This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time.The maximum switching frequency(MSF)is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio(SDR),whereas the closing dynamic performance limits the MSF when HSV operates with high SDR.Building upon these findings,the pre-excitation control algorithm(PECA)is proposed to reduce the switching time of the HSV,and consequently enhance its FRC.Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms,the closing delay time by 2.54 ms,and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms.As a result,a larger MSF of 417 Hz and a wider controllable SDR range from 20%to 70%were achieved at a switching frequency of 250 Hz.Thus,the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

A Study on the Static Characteristics of Typical Composite High Speed On-Off Valves

Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.

Structure optimization and flow field simulation of plate type high speed on-off valve

There is a relatively complex flow state inside the high speed on-off valve,which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool,causing cavitation and vortex and other phenomena.These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve.Aiming at the problems of small flow rate and instability of internal flow field,a new spool structure was designed.The flow field models of two-hole and three-hole plate spools with different openings were established,and software ANSYS Workbench was chosen to mesh the model.The standard k−εturbulence model was selected for numerical simulation using FLUENT software.The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained.The structure and parameters of the optimization model were also obtained.The stability analysis of flow field under different pressure was carried out.The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool,but it does not create a low pressure zone,and the three-hole spool can work stably at 2 MPa or less.This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool.The stability of flow field and the flow rate of high speed switch valve are improved.Finally,the products designed in this paper are compared with existing hydraulic valve products.The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree,and realizes the increase of flow rate.

TEST METHOD OF HIGH-SPEED ON-OFF VALVE DYNAMIC CHARACTERISTICS

According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.

Application of High-speed Solenoid Valve to the Semi-active Control of Landing Gear

To select or develop an appropriate actuator is one of the key and difficult issues in the study of semi-active controlled landing gear. Performance of the actuator may directly affect the effectiveness of semi-active control. In this article, parallel high-speed solenoid valves are chosen to be the actuators for the semi-active controlled landing gear and being studied. A nonlinear high-speed solenoid valve model is developed with the consideration of magnetic saturation characteristics and verified by test. According to the design rule of keeping the peak load as small as possible while absorbing the specified shock energy, a fuzzy PD control rule is designed. By the rule controller parameters can be self-regulated. The simulation results indicate that the semi-active control based on high-speed solenoid valve can effectively improve the control performance and reduce impact load during landing.

Dynamic Performance of High Speed Solenoid Valve with Parallel Coils

The methods of improving the dynamic performance of high speed on/off solenoid valve include increasing the magnetic force of armature and the slew rate of coil current, decreasing the mass and stroke of moving parts. The increase of magnetic force usually leads to the decrease of current slew rate, which could increase the delay time of the dynamic response of solenoid valve. Using a high voltage to drive coil can solve this contradiction, but a high driving voltage can also lead to more cost and a decrease of safety and reliability. In this paper, a new scheme of parallel coils is investigated, in which the single coil of solenoid is replaced by parallel coils with same ampere turns. Based on the mathematic model of high speed solenoid valve, the theoretical formula for the delay time of solenoid valve is deduced. Both the theoretical analysis and the dynamic simulation show that the effect of dividing a single coil into N parallel sub-coils is close to that of driving the single coil with N times of the original driving voltage as far as the delay time of solenoid valve is concerned. A specific test bench is designed to measure the dynamic performance of high speed on/off solenoid valve. The experimental results also prove that both the delay time and switching time of the solenoid valves can be decreased greatly by adopting the parallel coil scheme. This research presents a simple and practical method to improve the dynamic performance of high speed on/off solenoid valve.

High Speed On/Off Valve Control Hydraulic Propeller

The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propeller can improve the effeciency of ROV propulsion system significantly,and provides another attractive ROV propulsion system choice for engineers.

OPTIMAL CONTROL OF AN ACTIVE SUSPENSION SYSTEMEMPLOYING HIGH SPEED ON/OFF SOLENOID VALVE

Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this study, by using Linear-quadratic optimization technique and Kalman filter method, an optimal regulator controller with a state observer was designed for the proposed system. Simulation and experimental research was conducted on a quarter car model. The simulation analysis of the system frequency characteristic suggested that the peak value of magnitude response curve in the case of system with an optimal controller would be lowered significantly, and the experiment results also showed that an improvement in the vibration isolation effect was obtained in using the designed optimal controller over the sky hook damper controller.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Optimal Control of Hydraulic Position System Employing High Speed On/Off Solenoid Valve

A hydraulic position system was designed employing two high speed On/Off solenoid valves with PWM(Pulse width modulation) technique and using LQ(Linear Quadratic) optimization principle. Based on the system, the parts of system can be formulated with equations. According to equations, the mathematical model of the system was established. By simulation, the corresponding LQ optimal controller was designed and the PWM signals were generated. The comparison of the simulation and experiment results show that LQ optimal control method with PWM technique employing high speed On/Off solenoid valve can provide better system performance and a high position precision is obtained.

Multi-objective optimization of a high speed on/off valve for dynamic performance improvement and volume minimization

Hydraulic circuits with high speed on/off valve(HSV)for servo control have become commonplace in aerospace.However,the individual valve that is not volume-optimized results in a large total size of hydraulic control system,diminishing the practicality.To address this issue,the high-precision equivalent reluctance model of the HSV is established by employing an equivalent magnetic circuit,on which the dynamic characteristic of the HSV,as well as the effects of structural parameters on switching behaviour,are investigated.Based on this model,multi-objective optimization is adopted to design an HSV with faster dynamic performance and smaller volume,NSGA-II genetic algorithm is applied to obtain the Pareto front of the desired objectives.To assess the impact before and after optimization,an HSV based on the optimized structure is manufactured and tested.The experimental results show that the optimized HSV reduces 47.1%of its solenoid volume while improving opening and closing dynamic performance by 14.8%and 43.0%respectively,increasing maximum switching frequency by 6.2%,and expanding flow linear control area by 6.7%.These results validate the optimized structure and indicate that the optimization method provided in the paper is beneficial for developing superior HSV.

Investigation into the Independent Metering Control Performance of a Twin Spools Valve with Switching Technology-controlled Pilot Stage

In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonable method to optimize system dynamic performance.Integrating these two technologies into one component can combine their advantages together.However,few works focused on it.In this paper,a twin spools valve with switching technologycontrolled pilot stage(TSVSP)is presented,which applied DHT into its pilot stage while appending IMC into its main stage.Based on this prototype valve,a series of numerical and experiment analysis of its IMC performance with both simulated load and excavator boom cylinder are carried out.Results showed fast and robust performance of pressure and flow compound control with acceptable fluctuation phenomenon caused by switching technology.Rising time of flow response in excavator cylinder can be controlled within 200 ms,meanwhile,the recovery time of rod chamber pressure under suddenly changed condition is optimized within 250 ms.IMC system based on TSVSP can improve both dynamic performance and robust characteristics of the target actuator so it is practical in valve-cylinder system and can be applied in mobile machineries.

Dynamic performance and temperature rising characteristic of a high-speed on/off valve based on pre-excitation control algorithm

High speed on/off valve(HSV)is an essential component in aerospace digital hydraulic systems(ADHS).Dynamic performance and temperature rising characteristic are two important features,which determine the performance of HSV,and affect the response speed and reliability of ADHS.Increasing the driving voltage is an effective method for improving the dynamic performance of HSV.However,continuous high voltage excitation will lead to more wasted energy,higher temperature rising and lower reliability.To solve this problem,a pre-excitation control algorithm(PECA)is proposed in this paper based on the theoretical model of the influence of electrical parameters on dynamic performance and temperature rising characteristics.In PECA,an appropriate initial coil current is generated by pre-excitation instead of increasing driving voltage,which significantly shortens the switching delay time.Then,based on real-time current online calculation and feedback mechanism,the adaptive switching of five equivalent voltages is realized.Consequently,the coil current can be rapidly kept at the expected state without consuming more energy and generating more heat.Results indicate that compared with conventional PWM control algorithm,the PECA can improve dynamic performance of HSV,shorten the total switching time by 71.5%,and increase the maximum operation frequency.Therefore,the linear area of flow characteristic is expended by 80.0%,the adjusting time of HSV-controlled system is reduced by 23%,while shortening steady error by 46.7%.Moreover,the temperature rising characteristics of HSV are better,the maximum operation temperature is reduced by 68.6%,and the time to reach the steady state temperature is shortened by 20%.From the results,it can be concluded that the PECA is not only an effective and practical control algorithm for improving the performance of HSVs and HSV-controlled systems while reducing the heat generation and decreasing the temperature rising of HSV,but also can be a potential solution in ADHS.

MAGNETIC FIELD ANALYSIS OF ELECTROMAGNETIC VALVE TAKING HYSTERESIS INTO ACCOUNT

Predicting and optimizing of the high-speed solenoid on/off valve behaviorrequires an accurate model of the hysteresis loop of the magnetic material used A ferromagnetichysteresis model and a novel algorithm based on fixed-point technique to optimize theelectromagnetic model are introduced By utilizing a modified vector Preisach model of magnetichysteresis and the global genetic optimization algorithm based on partial mapping cross method, theB-H relation loops are identified accurately.

正负脉冲电压驱动的电磁螺纹插装阀动态特性分析

提出了一种基于PWM技术的正负脉冲电压控制策略,用于提高锥阀式电磁螺纹插装阀启闭动态响应速度,使其满足数字液压技术的要求。在分析电磁螺纹插装阀结构和工作原理基础上,建立了电磁螺纹插装阀的数学模型,并在AMESim软件中搭建电磁螺纹插装阀及其测试系统的多物理场耦合建模,研究不同正负脉冲电压持续时间条件下电磁螺纹插装阀线圈电流、阀芯位移、电磁力的变化规律,确定了电磁螺纹插装阀响应速度最快时正负脉冲电压控制策略的最优控制参数。利用半实物仿真系统搭建SCV硬件在环测试实验台,对所提正负脉冲控制策略进行验证。实验表明,与常规电压控制策略相比,当正负脉冲电压控制策略中正负脉冲电压持续时间都为10 ms时,电磁螺纹插装阀的开启时间由30 ms缩短到13.5 ms,其关闭时间由139 ms缩短到14 ms。研究结果为电磁螺纹插装阀的高响应化和数字液压技术的发展提供参考。

基于径向基函数神经网络算法的高频转阀阀芯稳定性

针对伺服电机驱动高频转阀时受液动力矩变化影响造成高频输出精度下降的问题,以液压马达作为动力源,提出一种基于径向基函数神经网络算法的转阀阀芯转速控制策略。首先,搭建高频转阀阀芯转速控制系统的数学模型;其次根据数学模型在MATLAB/Simulink平台搭建仿真模型,对不同算法作用下阀芯转速控制特性进行仿真分析;最后建立高频转阀转速控制系统实验台,对不同算法作用下阀芯转速控制特性进行实验研究和理论验证。结果表明:与常规PID控制方法相比,基于径向基函数神经网络的高频转阀转速控制策略转速控制系统阶跃响应所需调整时间最少为0.16 s,超调量小;三角波与正弦波转速跟踪误差均值下降最大值分别为46.51%、53.69%;6 MPa、10 MPa下,转速稳态误差均值分别下降34.92%、38.26%。径向基函数神经网络算法有效提高了高频转阀阀芯转速控制精度。

两种直动式高速电磁阀数值模拟与动态响应对比分析

针对直动式高速电磁阀动铁芯与阀芯加工、装配工艺要求高,一致性较差的问题,提出了一种动铁芯与阀芯可分离的结构,基于AMESim平台建立此款电磁阀电–磁–机–气多物理场耦合模型,考虑了动铁芯与阀芯撞击与分离的情况,并在试验台上进行了验证。然后与另一种动铁芯与阀芯“绑定”的结构形式进行比较分析。结果表明:两种电磁阀在动态响应与影响动态响应的关键参数存在差别。在同等条件下,第一种结构形式的电磁阀动态响应整体略差,但是其对动铁芯–阀芯加工、装配工艺的要求较低。

一种比例换向阀先导级用高速开关阀运动特性分析

为研究一种用于比例换向阀先导级的高速开关阀运动特性,通过编写UDF程序控制流体力、弹簧力和电磁力共同作用下的阀芯运动;通过动网格技术实现阀的流固耦合仿真,并获取阀芯精确的运动情况以及瞬态流场的变化。结果表明:编写的UDF程序能够精确地模拟实际工作时的阀芯运动状态,获得阀的开启时间为1.8 ms。该研究方法能够获得高速开关阀精确的运动特性,为高速开关阀产品的优化提供指导。

被动式压力控制技术的高速列车车内压力计算方法研究

现有采用被动式技术的高速列车车内压力计算方法,未考虑压力保护阀实际工作状态及鸭嘴孔的影响,不利于准确预测通过隧道时的车内压力。基于被动式压力保护阀开闭控制技术路线和空调鸭嘴孔开闭对车体气密性的影响特征,建立列车通过隧道时的车内压力计算方法。在采用一维可压缩非定常不等熵流动模型黎曼变量特征线法获得车外压力后,分析单列车通过短、中长、长、特长隧道情况下压力保护阀开闭特征,并对比分析单列车通过隧道情景下现有计算方法与本文方法预测车内压力变化的差异;结合压力舒适性标准限值分析车内压力舒适性指标值。研究表明:本文计算方法合理可行,不仅能更精确预测被动式技术的高速列车车内压力变化规律,而且为压力保护阀开闭控制技术制定提供切实可行的空气动力学优化依据。

高速开关阀先导驱动高水基大流量比例调速阀的设计与仿真

在智能综采工作面生产工程中,液压支架在移架和推溜的过程中经常会遭遇不稳定负载,传统开关式的电液控制元件无法对推溜油缸进行速度调控,导致推溜油缸位置控制困难,影响了刮板机的调直度,从而制约了智能综采装备的应用效率。针对这一问题,考虑到煤矿乳化液介质低黏度、润滑性差等特征,设计了一种高速开关阀作为先导阀的高水基高压大流量比例调速阀,建立了阀的数学模型,根据调速阀的内部结构及工作原理建立其AMESim仿真模型,对影响节流阀阀芯位置闭环控制特性、调速阀压差-流量特性进行仿真分析。仿真表明,A型先导液桥对主阀芯的响应具有更好的性能,主阀下控制腔容积、复位弹簧刚度对阀芯的响应速度、稳定性有一定影响。总体而言,调速阀具有较好的流量调节刚度,功能和性能达到了预期设计要求。