电液比例阀控制电路的设计与研究

在分析电液比例阀纯数字化PWM控制的基础上,提出了一种基于数字技术与模拟技术相结合的新方法,解决了电液比例阀阀芯的颤振问题和零位死区的流量补偿问题,并通过在线仿真,证明了该方法的可行性和实用性。     

双电磁铁比例方向阀零位位置控制死区补偿方法研究

针对双电磁铁驱动并带有阀心位置传感器的比例方向阀位置控制在零位存在死区的问题,运用Simulink对阀心位置控制系统进行了建模,对零位死区的形成原因进行了研究。通过仿真,对形成零位死区的各个影响因素对死区时间的影响程度进行了分析;基于不同的影响因素,提出了零位电流阶跃与衰减式位置指令跳跃的补偿策略;比较了该控制策略与其他控制方法对阀心位置的控制性能,最后通过实验进行了验证。研究结果表明:采用该位置控制补偿策略可以有效地消除由于系统非线性和时变性所带来的比例方向阀的零位位置控制死区,改善了阀心位置的响应波形。     

基于死区补偿的电液位置伺服系统自抗扰控制

针对电液位置伺服控制系统的比例阀死区、参数不确定及外部未知扰动等问题,设计了由自抗扰控制器与死区逆补偿构成的串联控制器.首先基于实验辨识构造死区逆模型对死区进行预补偿,然后根据系统特性设计了一阶自抗扰控制器,构造改进的扩张状态观测器对"总扰动"进行实时估计,并通过非线性控制律给予主动补偿.联合仿真与试验结果表明,所提出...     

伺服比例阀之浅见

伺服比例阀是一种在结构、性能、可靠性、价格上界于伺服阀与常规比例阀之间的比较新型的电液控制阀,它高频响、高精度、滞环小、无零位死区。对伺服比例阀与常规比例阀的性能进行了比较,并且对伺服比例阀未来的发展趋势进行了展望。     

液电混合高能效直线驱动系统控制及仿真分析

现有电液控制系统为控制液压缸位置,采用比例阀或伺服阀,造成了非常大的节流损失。为改善能效,提出了一种采用电-机械执行器和液压缸的新型液-电混合驱动系统,电-机械执行器用于控制负载运行速度和位置,主要克服惯性力;液压缸主要克服外负载力。为了抑制二者之间的耦合影响,电-机械执行器采用位置闭环控制,并在转矩环补偿干扰力。控制阀主要起液压缸换向作用,节流损失很小,以设定的电-机械直线执行器输出力阈值为基础,通过调节泵压力(液压缸进油压力)或阀开口(液压缸回油压力)控制液压缸输出力。研究结果表明,所提系统具有与阀控缸系统相同高的控制精度,并可大幅减小节流损失。与阀控缸系统相比,液电混合驱动系统能效提升了43.1%。     

一种双液压缸电液比例位置同步控制方法

双液压缸电液比例位置呈现静态与动态复杂变化，总扰动大，导致同步控制精度低。提出了一种针对双液压缸的电液比例位置同步控制方法。首先，构建双液压缸电液比例控制系统的数学模型；其次，根据系统数学模型推导动力学方程，在此基础上分析双液压缸电液比例控制系统的静态特性和动态特性；提出“同等+主从”控制策略，建立线性自抗扰同步控制器，估计并补偿双液压系统在运行过程中产生的总扰动，同时建立死区补偿器，以减小位置同步控制过程中的稳态误差，实现双液压缸电液比例位置的同步控制。实验结果表明，所提方法在x方向和y方向中，跟踪误差均控制在±1 mm以内，且超调量较小；最低可在0.51 s内达到阶跃期望位置，表现出了良好的效率和精度，具有一定应用价值。     

先导式电液比例阀非线性位置自适应补偿控制

为了提高先导式电液比例阀的位置控制性能,解决大批量先导式电液比例阀生产带来的不一致性问题,首先,建立了比例阀的非线性数学模型,针对比例阀死区不一致且难检测的问题,提出死区在线检测方法,采集主阀开始运动时的先导阀电磁铁电流值来表征死区大小,将当前死区值通过上位机在线读出并进行补偿;然后,针对普通PID固定增益带来的控制效率和精度低下的缺点,设计了基于死区在线检测的模糊PID自适应位置控制器,实时动态调整控制器各项参数;最后,基于MATLAB软件和先导式电液比例阀测试平台,验证所提出的控制方法的有效性。研究结果为先导式电液比例阀的批量化生产奠定了理论基础。     

气动比例阀控缸系统摩擦力补偿研究

针对阀控缸系统的摩擦力对系统控制性能造成的不良影响,提出了一种新的减小摩擦力影响的补偿方法。首先分析发现比例阀的摩擦力是造成其死区的主要原因,利用神经网络控制对比例阀摩擦力进行软件补偿与仿真;同时对气缸的摩擦力进行测试分析,通过在控制信号上叠加颤振信号来补偿气缸摩擦力并进行了仿真;最后结合2种补偿方法对系统进行了综合仿真研究。通过实验验证,结果表明所采用的补偿方法缩短了系统的缓冲时间,提高了系统的稳定性及定位精度。     

死区直接补偿的电液系统BP神经网络控制

为解决电液比例伺服系统无法精确定位的问题,推导了系统的流量动态平衡方程,并设计了一种基于死区直接补偿的BP(DZDC-BP)神经网络控制算法,即在线性化比例阀输入信号与输出流量关系的基础上,利用BP神经网络控制算法逼近非线性系统的特性,弥补系统中的非线性、未知参数、外部干扰和建模误差等问题,使得系统能够时刻跟随期望轨迹。使用MATLAB-AMESim软件对系统进行联合仿真,结果表明:无论系统有无外部干扰,DZDC-BP神经网络控制与有死区比例阀PID控制(PPID)和无死区比例阀PID控制(SPID)相比,系统的稳态误差都有显著的减少。说明DZDC-BP神经网络控制算法在一定程度上解决了系统中的死区和非线性等问题,同时具有良好的抗干扰能力,显著提高了系统的控制性能。     

基于DSP的死区效应补偿方法

分析了死区产生的机理和死区对输出电压、电流的影响,提出一种基于TMS320LF2407型DSP可编程死区控制功能和传感器特性的新型死区补偿方法.该方法软硬件相结合,有效改善了死区时间引起的电流畸变,且实时性高、计算量小,并通过实验验证了该死区补偿方法的有效性.     

电液双缸系统同步控制

由于强非线性和强耦合作用严重影响双缸同步系统的控制精度,同步误差加剧试件变形内力,具有较强的破坏能力,因此研究具有优良性能的同步控制算法具有重要的实践意义.建立考虑系统安装误差、测量误差、负载刚度和伺服阀零偏等因素在内的双液压缸同步控制系统数学模型;分析上述各误差因素对双缸同步控制精度的影响机理;提出了基于内力补偿和位...     

Robust adaptive precision motion control of hydraulic actuators with valve dead-zone compensation

This paper addresses the high performance motion control of hydraulic actuators with parametric uncertainties, unmodeled disturbances and unknown valve dead-zone. By constructing a smooth dead-zone inverse, a robust adaptive controller is proposed via backstepping method, in which adaptive law is synthesized to deal with parametric uncertainties and a continuous nonlinear robust control law to suppress unmodeled disturbances. Since the unknown dead-zone parameters can be estimated by adaptive law and then the effect of dead-zone can be compensated effectively via inverse operation, improved tracking performance can be expected. In addition, the disturbance upper bounds can also be updated online by adaptive laws, which increases the controller operability in practice. The Lyapunov based stability analysis shows that excellent asymptotic output tracking with zero steady-state error can be achieved by the developed controller even in the presence of unmodeled disturbance and unknown valve dead-zone. Finally, the proposed control strategy is experimentally tested on a servovalve controlled hydraulic actuation system subjected to an artificial valve dead-zone. Comparative experimental results are obtained to illustrate the effectiveness of the proposed control scheme.     

高速开关式位置伺服系统的模糊控制器的研究

四个高速开头阀经过恰当的组合,用PWMA方法可以对双作用油缸的位置和方向进行控制。为了克服液压系统建模的复杂性和阀控缸的非线性对传统控制算法的影响,设计了一种模糊控制器,实现了PWM高速开头阀控液压缸位置系统的精确控制。试验证明：模糊控制是对高速开头阀进行控制的有效工具,它为高速开关阀在工程中的应用开辟了广阔的前景。     

海上作业起重机主动升沉补偿系统的设计与分析

为补偿船用起重机在海上作业时的升沉运动,构造了基于二次调节静液传动技术的绞车液压驱动系统。首先,建立了升沉补偿系统的完整数学模型,提出了包含二次单元变量油缸位置环、二次单元马达速度环及二次单元马达位置环的三闭环控制结构。然后,给出了三闭环控制器的设计方法,为了得到起重机货物的位移,利用钢丝绳张力设计了状态观测器。最后,给出了一个设计实例,通过数字仿真从频域角度分析了升沉补偿系统的动态特性,为控制策略的研究打下基础。     

Model-based position tracking control of a hose-connected hydraulic lifting system

High-pressure rubber hose is normally used to connect the control valves and actuators of hydraulic systems and thus lower their natural frequency. PID control is preferred in industrial hydraulic systems as it has many advantages over other controls. However, the low natural frequency of hose-connected systems limits the performance of PID control. In this paper, a hose-connected hydraulic lifting test rig is presented and the mathematical model of the system is proposed. Valve compensation strategy and hose compensation strategy are designed based respectively on the flow characteristic of the proportional valve and the mathematical model of the hose. Comparative experiments with typical desired trajectories are carried out in the test rig. Results show that both the compensation strategies are effective in improving the tracking accuracy.     

New method to improve dynamic stiffness of electro-hydraulic servo systems

Most current researches working on improving stiffness focus on the application of control theories.But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated,so the control action is lagged.Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms.In this paper,the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed.On this basis,the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward.And a scheme using double servo valves to realize flow feedforward compensation is presented,in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time.The two valves are arranged in parallel to control the cylinder jointly.Furthermore,the model of flow compensation is derived,by which the product of the amplitude and width of the valve’s pulse command signal can be calculated.And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations.Using the proposed scheme,simulations and experiments at different positions with different force changes are conducted.The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time.That is,system dynamic load stiffness is evidently raised.This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.     

双阀并联电液位置控制系统研究

讨论了一类电液位置控制系统,它由一个可连续调节流量的小流量阀和一个开关型的大流量阀并联组成。对其稳定性条件、位置控制性能等进行了分析,并以比例阀和开关阀并联系统为例,说明此类系统成本低廉,避免运用昂贵的大流量电液伺服阀,特别适用于那些需要快速定位,定位精度高,并且工作时仅在小范围内需要调整的电液位置控制系统。     

负载口独立控制双联阀建模与特性分析

 为解除液压执行元件进出口之间的联动,提出了一种负载口独立控制双联阀,基于2个单元体阀芯错位组合,能实现负载口的独立控制。根据其工作原理,建立了阀控缸数学模型,进一步利用MATLAB/Simulink搭建了数值求解模型,对该阀在3种不同工况下的工作特性进行了分析。分析结果表明,通过对阀芯角位移和线性位移在工作行程零位及行程末端附近的联合控制,分别可实现微小流量稳定控制和大流量快速响应控制;阀芯角位移单独控制时,负载流量与之成正比,具有良好的线性流量增益效果;阀芯线性位移单独控制时,相同供油压力下能获得最大的负载流量和活塞位移。该阀具有较高的流量控制精度和灵活性,可为复杂工况下流量和压力的匹配补偿控制提供新思路。     

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.