Design and Experiment of Electronic-hydraulic Loading Test-bed Based on Tractor's Hydraulic Steering By-wire

An Electro-hydraulic loading system is designed based on a test-bed of tractor's hydraulic steering by-wire. To simulate the steering resistance driving tractor in many kinds of soils and roads,the loading force is controlled to make proportional and continuous variable by an electro-hydraulic proportional relief valve. A steering resistance loading test-bed is built to test three kinds of steering resistance including constant,step and sine style. Tire lateral resistance is also tested under different steering conditions. The result shows that the electro-hydraulic loading system has high stability and following performance. Besides,the system's steady state error is lower than 3. 1%,and it meets the test requirement of tractor's hydraulic steering by-wire.

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.

Multi-Channel Force Control System for Static Loading

An eight-channel force loading system is presented, which adopts position control system and force control system switching model, small flow servo valve controlled capacious cylinder system scheme, intelligent PID algorithm and distributed load approach. Through the analyses of the equivalent model of valve controlled cylinder force subsystem, a controller based on intelligent PID algorithm is designed, which is not sensitive to the variation of parameters such as environmental stiffness. According to the coupling of multiple load channels, a distributed load approach is employed in the superior monitor computer. Experimental results show that the system designed has high precision and robustness.

Study on Friction Torque Loading with an Electro-hydraulic Load Simulator

This article, in order to precisely impose friction on aircraft and weapon actuation systems, presents a new friction loading method characteristic of ＂torque-zero velocity＂ switching control with an electro-hydraulic load simulator. As the general Stribeck friction model has little related to static friction, it proposes a ＂torque-zero velocity＂ switcher, in which a zero-velocity controller is developed to load the static friction and a torque controller the kinetic friction. With the help of mathematical modeling, this article designs a ＂torque-zero velocity＂ switching controller and, correspondingly, provides a ＂dual-threshold judgment＂ algorithm. Simulation results indicate that the proposed method can be successfully used to carry out the static and kinetic friction simulation with an electro-hydraulic load simulator.

Robust Control for Static Loading of Electro-hydraulic Load Simulator with Friction Compensation

Load simulator is a key test equipment for aircraft actuation systems in hardware-in-the-loop-simulation. Static loading is an essential function of the load simulator and widely used in the static/dynamic stiffness test of aircraft actuation systems. The tracking performance of the static loading is studied in this paper. Firstly, the nonlinear mathematical models of the hydraulic load simulator are derived, and the feedback linearization method is employed to construct a feed-forward controller to improve the force tracking performance. Considering the effect of the friction, a LuGre model based friction compensation is synthesized, in which the unmeasurable state is estimated by a dual state observer via a controlled learning mechanism to guarantee that the estimation is bounded. The modeling errors are attenuated by a well-designed robust controller with a control accuracy measured by a design parameter. Employing the dual state observer is to capture the different effects of the unmeasured state and hence can improve the friction compensation accuracy. The tracking performance is summarized by a derived theorem. Experimental results are also obtained to verify the high performance nature of the proposed control strategy.

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。

Adaptive Nonlinear Optimal Compensation Control for Electro-hydraulic Load Simulator

Directing to the strong position coupling problem of electro-hydraulic load simulator (EHLS), this article presents an adaptive nonlinear optimal compensation control strategy based on two estimated nonlinear parameters, viz. the flow gain coefficient of servo valve and total factors of flow-pressure coefficient. Taking trace error of torque control system to zero as control object, this article designs the adaptive nonlinear optimal compensation control strategy, which regards torque control output of closed-loop controller converging to zero as the control target, to optimize torque tracking performance. Electro-hydraulic load simulator is a typical case of the torque system which is strongly coupled with a hydraulic positioning system. This article firstly builds and analyzes the mathematical models of hydraulic torque and positioning system, then designs an adaptive nonlinear optimal compensation controller, proves the validity of parameters estimation, and shows the comparison data among three control structures with various typical operating conditions, including proportion-integral-derivative (PID) controller only, the velocity synchronizing controller plus P1D controller and the proposed adaptive nonlinear optimal compensation controller plus PID controller. Experimental results show that systems' nonlinear parameters are estimated exactly using the proposed method, and the trace accuracy of the torque system is greatly enhanced by adaptive nonlinear optimal compensation control, and the torque servo system capability against sudden disturbance can be greatly improved.

A practical nonlinear robust control approach of electro-hydraulic load simulator

This paper studies a nonlinear robust control algorithm of the electro-hydraulic load simulator （EHLS）. The tracking performance of the EHLS is mainly limited by the actuator＇s motion disturbance, flow nonlinearity, and friction, etc. The developed controller is developed based on the nonlinear motion loading model. The problems of the actuator＇s disturbance and flow nonlinearity are considered. To address the friction problem, the friction model of the loading motor is identified experimentally. The friction disturbance is compensated using the obtained friction model. Therefore, this paper considers the main three factors comprehensively. The developed algorithm is easy to apply since the controller can be obtained just with one step back-stepping design. The stability of the developed algorithm is proven via Lyapunov analysis. Both co-simulation and experiments are performed to verify the effectiveness of this method.

An experimental study of the dual-loop control of electro-hydraulic load simulator (EHLS)

This paper investigates motion coupling disturbance（the so called surplus torque）in the hardware-in-the-loop（HIL）experiments.The＇＇velocity synchronization scheme＇＇was proposed by Jiao for an electro-hydraulic load simulator（EHLS）in 2004.In some situations,however,the scheme is limited in the implementation for certain reasons,as is the case when the actuator＇s valve signal is not available or it is seriously polluted by noise.To solve these problems,a＇＇dual-loop scheme＇＇is developed for EHLS.The dual-loop scheme is a combination of a torque loop and a position synchronization loop.The role of the position synchronization loop is to decouple the motion disturbance caused by the actuator system.To verify the feasibility and effectiveness of the proposed scheme,extensive simulations are performed using AMESim.Then,the performance of the developed method is validated by experiments.

一种新的电液比例变量泵P-Q特性曲线测试方法

对开环加载测试方法进行数值仿真和试验验证的结果发现,电液比例变量泵P-Q特性曲线在恒流和恒压段分别存在较大的滞环和振动,因此提出了系统压力闭环控制的测试方法.该方法根据泵不同工作模式下测试系统不同的加载要求,在恒流模式下通过PI调节实现压力控制,在恒压模式下通过PD调节削弱压力振动,并设计了可根据泵的工作状态自动调整控制策略及控制信号的自适应控制器.对闭环加载测试方法进行数值仿真和试验验证,结果表明,所提出的方法可有效消除测试过程中存在的流量测量误差和压力振动,对电液比例变量泵P-Q特性曲线测试工作的改进具有实际意义.

基于NIPCI-6221高精度液压调平试验系统的实现

为了提高火炮发射平台、车载雷达以及激光武器等要求高精水平度平台的调平效率和精度,采用负载敏感及电液位置伺服控制技术,并应用PCI-6221数据采集卡和伪微分控制算法设计了高精度液压调平试验系统。试验结果表明:该试验系统具有无超调、响应快的特点。

液驱并联机构多维力加载系统CMAC-模糊PID控制

针对液驱并联机构多维力加载系统非线性、时变和强耦合的系统特性,提出一种改进PID控制策略以提高系统输出精度。通过构建多维力加载系统动力学模型与液压动力元件模型,分析研究耦合力产生机理。将多维力加载时受系统自身结构影响的各通道间耦合力与系统参数摄动等非线性因素视为干扰,采用模糊控制对PID参数进行实时调整,抑制系统非线性干扰以提高跟踪精度;考虑到传统经验法或专家知识库的模糊推理对PID控制参数调整不够精细,提出一种模糊PID与小脑模型神经网络(cerebellar model articulation controller,CMAC)并行的控制策略,利用其自适应能力与快速学习非线性函数能力对模糊PID控制过程进行学习和插补。研究结果表明:与PID控制器相比,CMAC-模糊PID控制器能够有效地解决液驱并联机构多维力加载系统复杂的跟踪问题。

P-Q伺服阀抑制电液负载模拟器多余力的研究

建立了采用P-Q伺服阀控制加载的电液负载模拟器系统键图模型,并通过仿真验证了该模型的正确性。通过对P-Q伺服阀和普通的流量伺服阀加载试验曲线的对比分析表明,采用P-Q伺服阀控制可以有效地抑制多余力。

P-Q伺服阀在减摇鳍电液负载仿真台中的应用

由于P-Q伺服阀内部的压力反馈作用,使得采用P-Q伺服阀控制的被动式加载系统能取得较好的抑制多余力效果。通过对P-Q伺服阀工作原理的分析,分别建立了P-Q伺服阀和采用P-Q伺服阀控制加载的减摇鳍负载仿真台的传递函数模型。通过对P-Q伺服阀加载试验曲线的分析表明,采用P-Q伺服阀控制可以有效地抑制减摇鳍仿真台的多余力,特别是减摇鳍系统启动和换向时的多余力。

压力-流量复合控制电液系统动力源的建模与仿真

针对电液伺服系统高能耗问题,设计一种压力-流量负载敏感复合控制动力源,利用Matlab仿真软件建立系统模型,依据实际工业设备工作时对负载压力和负载流量的控制要求,对系统动力源输出压力和流量进行仿真,验证压力-流量负载敏感复合控制动力源节能的可行性。这种动力源已应用在负载压力和负载流量变化大的钢管折弯压力机上。

WES-1000D电液式万能试验机的研制

WES-1000D电液式万能试验机是济南试金集团有限公司自主研发制造的数显式液压万能试验机。整机主要由主机、油源、控制柜和数显表四大部分构成,具有功能全、用途广、精度高、寿命长、价格低、操作简单等优点。整机各项技术指标均满足国家相关标准的要求。

新华DEH-ⅢA系统甩负荷带小网控制方案的探讨

对上海新华控制工程有限公司的DEHⅢ-A汽轮机数字式电液控制系统在旺隆热电有限公司机组运行时,由于外线故障引起1号机组甩负荷带厂用电运行的实际控制过程进行分析,该系统对于有可能甩负荷后机组成孤岛运行的控制方案在实际运用中有明显的不足。文中初步探讨了甩负荷后DEH的控制方案,供同类机组参考。

Deign of a Synchro-compensation Control System for Elimination of Disturbance

To counter the strong disturbance caused by the rotation of steering axle, a synchro-compensation methodis proposed to absorb the generated disturbance now by driving the loading motor stator to make it synchronously rotatewith its axle. Through analyzing and discussing different kinds of synchro-compensation schemes, the determinedpassive position and speed synchro-compensation systems are designed and simulated by computer. The results prove thatthisa method is effective to eliminate the strong disturbance of the steering axle.

重型拖拉机负载敏感电液提升系统研究现状

主要介绍了负载敏感电液提升系统在农业领域中对于重型拖拉机的重要作用。首先,详细阐述了负载敏感电液比例阀和电液提升系统的原理和功能,然后从电液比例技术、插装阀技术和控制技术等方面对国内外研究现状进行了分析。接着,概述了该领域的主要进展和最新研究成果,并指出了存在的问题。最后,提出了未来重型拖拉机负载敏感系统研究的重点和发展方向,这将有助于学者更好地了解该领域并推动行业技术进步。

高精度的动态加载系统建模与控制算法试验研究

为设计全程静态精度小于0.05%FS、动态精度小于1%FS的动态力加载装置,文中在缺乏匹配的压力型电液伺服阀的情况下,采用流量型电液伺服阀设计了动态加载装置的液压系统,并对高精度动态加载的控制算法进行了试验研究。试验结果表明:采用传统PID控制加载力,其静态精度可达0.041%FS,动态精度可达2.5%FS,均超过动态加载装置的控制要求;采用自适应PID控制加载力,其静态精度可达0.039%FS,施力中间阶段的加载力动态精度可达1%FS,但在施力初始阶段和施力结束阶段,加载力动态精度高达8%FS,考虑加载力在施力过程中呈现阶段性特点,提出采用分段自适应PID控制算法,经动态加载力试验论证,分段自适应PID算法能够有效解决加载力动态精度超差问题,加载力的静态精度可以控制在0.018%FS,动态控制精度可以控制在1%FS,完全满足高精度动态加载装置的控制要求。