Design and Experimental Evaluation of PID Controller for Digital Electro-Pneumatic Cabin Pressure Control System

The performance of the designed digital electro-pneumatic cabin pressure control system for the cabin pressure schedule of transport aircraft is investigated.For the purpose of this study,an experimental setup consisting of a simulated hermetic cabin and altitude simulation chamber is configured for cabin pressure control system operation.A series of experimental tests are executed to evaluate the performance of the cabin pressure control system.The parameters of the PID controller are optimized.In the optimization process,the variation regularity of the rate of cabin pressure change under various conditions is considered.An approach to prioritize the control of the rate of change of cabin pressure based on the flight status model is proposed and verified experimentally.The experimental results indicate that the proposed approach can be adopted for the designed digital electro-pneumatic cabin pressure control system to obtain a better cabin pressure schedule and rate of cabin pressure change.

Sliding Mode Control of Hydraulic Pressure in Electro-Hydraulic Brake System Based on the Linearization of Higher-Order Model

The possibility to enhance the stability and robustness of electrohydraulic brake(EHB)systems is considered a subject of great importance in the automotive field.In such a context,the present study focuses on an actuator with a four-way sliding valve and a hydraulic cylinder.A 4-order nonlinear mathematical model is introduced accordingly.Through the linearization of the feedback law of the high order EHB model,a sliding mode control method is proposed for the hydraulic pressure.The hydraulic pressure tracking controls are simulated and analyzed by MATLAB/Simulink soft considering separately different conditions,i.e.,a sine wave,a square wave and a square wave with superimposed sine disturbance.The results show that the proposed strategy can track the target within 0.25 s,and the mean observed error is less than 1.2 bar.Moreover,with such a strategy,faster response and less overshoot are possible,which should be regarded as significant advantages.

WORKING LIQUID PRESSURE AND ITS CONTROL IN HYDRAULIC DRAWING PROCESSES OF CUPS

A method of setting up a pressure-stroke characteristic of the working liquid in hydraulic drawing is studied. A pressure-stroke characteristic and software for controlling its forming process are also developed. And a set of pressure controlling devices with PLC as a central processor are designed. It can be got from the relevant experiments that the pressure-stroke characteristic is correct and its control for forming process is available.

Research and Development of Electro‑hydraulic Control Valves Oriented to Industry 4.0:A Review

Electro-hydraulic control valves are key hydraulic components for industrial applications and aerospace,which controls electro-hydraulic motion.With the development of automation,digital technology,and communication technology,electro-hydraulic control valves are becoming more digital,integrated,and intelligent in order to meet the requirements of Industry 4.0.This paper reviews the state of the art development for electro-hydraulic control valves and their related technologies.This review paper considers three aspects of state acquisition through sensors or indirect acquisition technologies,control strategies along with digital controllers and novel valves,and online maintenance through data interaction and fault diagnosis.The main features and development trends of electro-hydraulic control valves oriented to Industry 4.0 are discussed.

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.

Pressure control strategy for pump motor energy transfer unit

Multi-level pressure source system is a novel hydraulic system with distinct advantage of energy saving. In order to balance each pressure level of the multi-level pressure source system, a pump motor energy transfer unit is usually equipped. However, the pump motor energy transfer has the characteristics of poor starting and low response, which cause long time of pressure adjustment and large pressure jitter when the transformer is switched to system suddenly and the motor-side pressure has pressure impact when rail of the pump-side is switched. To address these problems, this paper proposes a compound control strategy of feedforward compensation control with Fuzzy-PID to improve the controllability of the multi-level pressure source system. A test rig of the pump motor energy transfer unit is built and the controllability of compound controller and PID controller are compared. The experiment results show that, compared with the traditional PID, the adjustment time and the pressure impact are reduced by 20% and 25% with the proposed compound control strategy. Therefore, the presented compound control strategy can be used to improve starting performance and robustness of the pump motor energy transfer unit control system.

Research on hydraulic slotting technology controlling coal-gas outbursts

Measured to control serious coal-gas outburst in coal seam were analyzed by theory and experimented in test site.A new technique to distress the coal-bed and drain methane,called hydraulic slotting,was described in detail,and the mechanism of hydrau- lic slotting was put forward and analyzed.The characteristic parameter of hydraulic slotting was given in Jiaozuo mining area and the characteristic of validity,adaptability and secu- rity was evaluated.The results show that the stress surrounding the strata and the gas in coal seam is released efficiently and thoroughly while new techniques are taken,as slot- ting at heading face by high pressure large diameter jet.The resistance to coal and gas outbursts is increased dramatically once the area of slotting is increased to a certain size. In the process of driving 2 000 m tunnel by hydraulic slotting excavation,coal and gas outburst never occurre.The technique could be used to prevent and control potential coal-gas outburst in the proceeding of tunnel driving,and the speed tunneling could be as high as more than 2 times.

Simulation and experimental research of digital valve control servo system based on CMAC-PID control method

Digital valve control servo system is studied in this paper. In order to solve the system problems of poor control precision and slow response time,a CMAC-PID( cerebellar model articulation controller-PID) compound control method is proposed. This compound controller consists of two components: one is a traditional PID for the feedback control to guarantee stability of the system; the other is the CMAC control algorithm to form a feed-forward control for achieving high control precision and short response time of the controlled plant. Then the CMAC-PID compound control method is used in the digital valve control servo system to improve its control performance. Through simulation and experiment,the proposed CMAC-PID compound control method is superior to the traditional PID control for enhancing stability and robustness,and thus this compound control can be used as a new control strategy for the digital valve control servo system.

Control performance and energy saving of multi-level pressure switching control system based on independent metering control

Aiming at the problem of large energy consumption in hydraulic control system with large load and variable working conditions,based on the multi-level pressure switching control system(MPSCS),a multi-level pressure switching control system based on independent metering control is proposed combined with the independent metering control technology.The configuration principle of the system is given,the mathematical model of this system is established,and the control strategy of the system under 4 different working quadrants is put forward.Finally,the control performance and energy saving characteristics of the system are tested.The test results show that the switching of high and low pressure power supply has a certain effect on the response of step position and ramp position under impedance working condition.The displacement curves show slow climbing or abrupt change of ramp position,and the position accuracy is less than 1 mm.The multi-level pressure switching control system based on independent metering control can recover and store energy under the transcendence working conditions.The control accuracy is about 1 mm,and the energy recovery rate is about 70%~80%.

基于虚拟控制平台的液压CAT系统研究

本文主要介绍基于虚拟控制平台的液压ＣＡＴ系统构成原理及实现方法,该技术使液压ＣＡＴ系统结构得以简化、可维护性得以提高、稳定性和可靠性得以改善,具有较大的推广价值。

双阀芯增量式高水基数字阀的设计及实验研究

刮板输送机的直线度控制,是实现煤矿智能化的关键技术,但由于井下工作面通断式支架电液阀的不连续性,难以满足综采工作面直线度的自适应控制需求。此外,由于支架液压系统采用乳化液作为介质,用于油介质的比例阀难以直接用于支架液压系统。针对上述问题,提出了一种新型双阀芯增量式高水基数字阀结构,其主要由电机丝杠驱动部、双阀芯组件和阀块组成。首先,对双阀芯增量式数字阀的结构和工作原理进行了分析,其新型的双阀芯结构形式,可实现负载口独立控制,兼具开环与闭环两种工作方式。其次,对阀芯阀座处的关键密封副进行数学建模,综合考虑密封比压与密封接触宽度,发现采用“硬对软”材料配对时,可兼顾密封副的密封性与使用寿命,且在阀座半锥角为0.61 rad时达到最佳效果。再次,对电–机械转换器进行建模并采用滑模控制算法进行仿真分析,正弦响应时,滑模控制算法经过0.08 s能稳定跟踪参考信号,响应性能明显优于PID。最后,搭建xPC Target实时控制平台进行样机实验,测试了密封副的密封性,以及不同电机细分控制下和不同阶跃幅值下的性能。结果表明:在21 MPa压力下密封副能可靠密封;采用1600脉冲/转的细分控制性能最佳;0.2 mm阶跃响应时,其响应时间为0.25 s,稳态误差为3μm,流量为13 L/min,具有较优的控制性能。

基于TwinCAT的数字伺服控制系统设计

为研制高频响、可记录数字伺服控制系统,以倍福的微型工控机和AD,DA模块为主要硬件,以Twin CAT为实时操作系统,以倍福的可编程控制器(PLC)为数字伺服控制编程语言,基于C#开发数字伺服控制系统界面。所设计的双路伺服控制系统具有良好的实时性、稳定性,数据更新周期为50μs,输入输出延迟为150μs,可不丢点记录各通道数据。内含扫频信号源,波形包括方波、三角波、正弦波,也可以用来测试系统频响。基于Twin CAT开发的数字伺服控制系统频响高,工作稳定,可用于各类液压伺服控制系统,也可用于系统特性测试。

高水基数字比例阀控电液位置伺服系统建模与控制

针对我国煤矿液压装备底层执行机构存在控制精度差与数字化程度低的问题,提出了基于高水基数字比例阀和换向阀组合控制液压缸的方案。首先,对高水基数字比例阀控电液位置伺服系统的结构与工作原理进行深入分析,在此基础上构建了伺服系统AMESim仿真模型,并对步进电机子模型、高水基数字比例阀子模型进行验证。其次,提出了液压缸位移/速度双闭环、液压缸位移/主阀位移双闭环两种控制方法,并基于Simulink和AMESim搭建了系统机电液联合仿真模型,仿真结果验证了所提方法的有效性。进一步,搭建了高水基数字比例阀控电液位置伺服系统试验平台,试验表明,液压缸位移/速度双闭环控制方法存在抖动现象,且液压缸位置的最大误差达到了1.5 mm,液压缸位移/主阀位移双闭环控制下的液压缸跟踪误差在0.4 mm内,超调量为0,满足控制精度需求。研究结果对提升我国煤矿液压装备的控制精度和数字化水平具有实际意义。

一种压力控制元件计算机辅助测试系统(CAT)的研究

本文结合新型压力控制元件—数字式压力控制器的测试试验，阐述了压力控制器微机辅助测试系统的原理及软硬件结构。试验结果表明此系统提高了压力控制器的测试精度和测试效率。

柔性测控系统在快组式液压试验台CAT中的应用

常见快速组合式液压试验台测控系统通用性较差,无法配合其高度开放的硬件实现设计性、创新性液压试验。采用虚拟仪器实现液压试验台柔性测控系统改造,使之适用于拼装的任何液压试验回路,改造过程中针对数据采集卡定时/计数器个数有限的问题,提出了基于"软定时/计数器"的方法精简数据采集卡设备。改造后的测控系统对数据采集硬件要求低,具有高度通用性、灵活性和扩展性的特点。

双联液压元件新型应用与性能分析

针对现有传统液压回路在多种不同压力、不同流量工况中需要借助繁多功能控制阀来调节的功能缺陷,以及能耗大、效率低等问题,将双联液压元件应用于几种典型回路中,并对由双联液压元件组成的新型液压系统的节能特性、输出特性进行了研究分析。结果表明:双联液压元件的应用能够节省成本、简化系统、消除压力互相干扰、减少功率损失,实现了功率的匹配,达到了节能目的。

压力控制阀CAT系统研究

压力控制阀主要用来控制液压系统中液流压力。本文分析了压力控制阀的各种静态性能指标和动态性能指标,并根据压力控制阀性能测试要求,设计出了测试液压系统回路和CAT测试系统。该测试系统采用上下位机分级式结构,实现抗干扰和数字滤波功能,系统稳定可靠,具有较强的实用性。

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.

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.

Optimal Valve Closure Operations for Pressure Suppression in Fluid Transport Pipelines

When a valve is suddenly closed in fluid transport pipelines,a pressure surge or shock is created along the pipeline due to the momentum change.This phenomenon,called hydraulic shock,can cause major damage to the pipelines.In this paper,we introduce a hyperbolic partial differential equation(PDE)system to describe the fluid flow in the pipeline and propose an optimal boundary control problem for pressure suppression during the valve closure.The boundary control in this system is related to the valve actuation located at the pipeline terminus through a valve closing model.To solve this optimal boundary control problem,we use the method of lines and orthogonal collocation to obtain a spatial-temporal discretization model based on the original pipeline transmission PDE system.Then,the optimal boundary control problem is reduced to a nonlinear programming(NLP)problem that can be solved using nonlinear optimization techniques such as sequential quadratic programming(SQP).Finally,we conclude the paper with simulation results demonstrating that the full parameterization(FP)method eliminates pressure shock effectively and costs less computation time compared with the control vector parameterization(CVP)method.