Application of Simple Adaptive Control to Water Hydraulic Servo Cylinder System

Although conventional model reference adaptive control （MRAC） achieves good tracking performance for cylinder control, the controller structure is much more complicated and has less robustness to disturbance in real applications. This paper discusses the use of simple adaptive control （SAC） for positioning a water hydraulic servo cylinder system. Compared with MRAC, SAC has a simpler and lower order structure, i.e., higher feasibility. The control performance of SAC is examined and evaluated on a water hydraulic servo cylinder system. With the recent increased concerns over global environmental problems, the water hydraulic technique using pure tap water as a pressure medium has become a new drive source comparable to electric, oil hydraulic, and pneumatic drive systems. This technique is also preferred because of its high power density, high safety against fire hazards in production plants, and easy availability. However, the main problems for precise control in a water hydraulic system are steady state errors and overshoot due to its large friction torque and considerable leakage flow. MRAC has been already applied to compensate for these effects, and better control performances have been obtained. However, there have been no reports on the application of SAC for water hydraulics. To make clear the merits of SAC, the tracking control performance and robustness are discussed based on experimental results. SAC is confirmed to give better tracking performance compared with PI control, and a control precision comparable to MRAC （within 10 μm of the reference position） and higher robustness to parameter change, despite the simple controller. The research results ensure a wider application of simple adaptive control in real mechanical systems.

Hydraulic Self Servo Swing Cylinder Structure Optimization and Dynamic Characteristics Analysis Based on Genetic Algorithm

The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that,a method of the hydraulic self servo swing cylinder structure optimization based on genetic algorithm was proposed in this paper. By analyzing the four parameters that affect the dynamic characteristics, we had to optimize the structure to obtain as larger the Dm( displacement) as possible under the condition with the purpose of improving the dynamic characteristics of hydraulic self servo swing cylinder. So three state equations were established in this paper. The paper analyzed the effect of the four parameters in hydraulic self servo swing cylinder natural frequency equation and used the genetic algorithm to obtain the optimal solution of structure parameters. The model was simulated by substituting the parameters and initial value to the simulink model. Simulation results show that: using self servo hydraulic swing cylinder natural frequency equation to study its dynamic response characteristics is very effective.Compared with no optimization,the overall system dynamic response speed is significantly improved.

Structural Design and Dynamic Characteristics of Overloaded Horizontal Servo Cylinder for Resisting Dynamic Partial Load

When an output curve force is applied to a horizontal servo cylinder with a heavy load, the piston rod bears a dynamic partial load based on the installation and load characteristics, which significantly a ects the frequency response and control accuracy of the servo cylinder. Based on this partial load, increased friction can lead to cylinder bore scu ng, leakage, lack of output power, or even system failure. In this paper, a novel asymmetric static-pressure support structure is proposed based on the principle of hydrostatic support. The radial component force of a dynamic partial load is balanced by cooperation between the support oil cushion of the variable hydraulic pressure support structure, oil cushion of the supportive force, and the damper. Adaptive control of the servo cylinder piston rod, guide sleeve, and piston, as well as the cylinder oil film friction between lubricated surfaces is achieved. In this paper, theoretical design and analysis of the traditional hydrostatic bearing structure and novel structure are presented. A hydraulic dynamic shear scissor is used as a research target to derive a structural dynamic model. Comparative simulations are performed using Matlab Simulink. Additionally, flow field analysis of the novel structure is performed, which verifies the rationality and feasibility of the proposed structure and system.

Modeling and fuzzy adaptive proportion-integration-differentiation control of X-Y position servo system actuated by oscillating pneumatic cylinder

The servo system actuated by oscillating pneumatic cylinder for X-Y plate is a multi-variable nonlinear control system. Its mathematical model is established, and nonlinear factors are analyzed. Due to the existence of deadlock zone and the small damp of the pneumatic oscillating cylinder, it is likely to result in overshoot, and there is also certain steady-state error, so online modifying of proportion-integration-differentiation （PID） parameters is needed so as to achieve better control performance. Meanwhile considering the stability demand for long-term run, a fuzzy adaptive PID controller is designed. The result of hardware-inloop （HIL） test and real-time control experiment shows that the adaptive PID controller has desirable serfadaptability and robustness to external disturbance and to change of system parameters, and its control per- fonnance is better than that of traditional PID controllers.

Analysis on Static Pressure Bearing Seal Characteristics of Guide Sleeve of Electro-hydraulic Servo Cylinder

As a typical bionic walking robot, hydraulic quadruped robot has attracted much attention because of its high mobility, strong load capacity and steady motion. The electro-hydraulic servo cylinder, as its power actuator, requires low friction, good lateral load resistance and high speed motion. The electro-hydraulic servo cylinder hydrostatic bearing seal guide sleeve is taken as the research object in this paper. By using Fluent software to analyze and contrast the film characteristics of rectangular and I-shaped oil chamber of hydrostatic bearing seal guide sleeve, the relationship between piston rod moving speed, eccentricity, oil film carrying capacity, friction force and leakage volume, as well as the relationship between oil feed flow and oil film bearing capacity, friction force, inlet pressure and leakage volume were analyzed. This study provides a theoretical basis for optimizing the static pressure bearing seal parameters.

Study on Oil Cavity Number of Hydrostatic Guide Sleeve of Electro-hydraulic Servo Cylinder

The electro-hydraulic servo drive hydraulic cylinder has many unique advantages, such as fast response, high load stiffness, high control power, strong anti-eccentric load ability and so on, so it has been widely used in industrial control. Based on the guide sleeve of hydrostatic seal of hydraulic cylinder, the reasonable number of oil chamber of guide sleeve is studied in this paper. ICEM CFD software and FLUENT simulation software are used to calculate and analyze the number of different oil chambers of guide sleeve of hydrostatic seal. The temperature field of piston rod with different moving speed, different initial pressure of oil chamber and oil film under different number of oil chambers is analyzed. The relationship between the pressure field and temperature field provides a better basis for optimizing the design of hydrostatic guide sleeve and helps to improve the servo drive cylinder.

Co-Simulation Research of the Mechanical-Hydraulic-Control Coupling System of ITER Tractor

The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision characteristics, and the data transfer between the different models was accomplished by the integration interface between different software. Consequently the virtual experimental platform for the multi-disciplinary co-simulation was established. A co-simulation study of the mechanical-hydraulic-control coupling system of the ITER tractor was carried out. The synchronization servo control of parallel hydraulic cylinders was implemented, and the tracking control of the preconcerted trajectory of the hydraulic cylinders was realized on the established experimental platform. This paper presents the optimization design and technology rebuilding for the complicated coupling system with its theoretic foundation and co-simulation virtual experimental platform.

ADAPTIVE CONTROLLER AND ITS APPLICATION IN FORCE SYSTEM OF ASYMMETRIC CYLINDER CONTROLLED BY SYMMETRIC VALVE

Partial pressure, system vibration and asymmetric system dynamic performance exit in asymmetric cylinder controller by symmetric valve hydraulic system. To solve this problem in the force control system, model reference adaptive controller is designed using equilibrium point stability theory and output error equation polynomial. The reference model is selected in such a way that it meets the system dynamic performance. Hardware configuration of asymmetric cylinder controlled by asymmetric valve hydraulic system is replaced by intelligent control algorithm, thus the cost is lowered and easy to application. Simulation results demonstrate that the proposed adaptive control sheme has good adaptive ability and well solves asymmetric dynamic performance problem. The designed adaptive controller is fairly robust to load disturbance and system parameter variation.

Work characteristic analysis of single-rod symmetric cylinders

Hydraulic cylinders are divided into single-rod asymmetric cylinders and double-rod symmetric cylinders. The single-rod asymmetric cylinder has the advantages of small size and simple structure,but its speed characteristic is not symmetric. The double rod symmetric cylinder has the characteristic of symmetric speed,but it cannot be used in some special occasions. In this paper,one special hydraulic cylinder,a single-rod symmetric cylinder,is developed. Firstly,characters of this type of cylinder are introduced. Then,the system model is constructed by using one software which is Simulation X. Moreover,one single rod asymmetric cylinder is designed and the test rig using the symmetric valve to control single-rod symmetric or asymmetric cylinder is constructed. Both of the simulation and experimental results show that the symmetric valve control single-rod symmetric cylinder servo system is of symmetric speed characteristic,which can be used in practical occasion.

Nonlinear Modeling of a High Precision Servo Injection Molding Machine Including Novel Molding Approach

A nonlinear mathematical model of the injection molding process for electrohydraulic servo injection molding machine (IMM) is developed.It was found necessary to consider the characteristics of asymmetric cylinder for electrohydraulic servo IMM.The model is based on the dynamics of the machine including servo valve,asymmetric cylinder and screw,and the non-Newtonian flow behavior of polymer melt in injection molding is also considered.The performance of the model was evaluated based on novel approach of molding - injection and compress molding,and the results of simulation and experimental data demonstrate the effectiveness of the model.

Pneumatic force servo system based on disturbance observer

In order to design a low-cost pneumatic force servo system with large output forces,a scheme of a booster cylinder controlled by high speed solenoid valves is proposed.A nonlinear model of the system is established,in which the hysteresis of high speed solenoid valve is considered.In order to deal with parameter uncertainty and disturbances of noise and friction,a feed-forward control method based on a disturbance observer is proposed.A practical pneumatic force servo system is used to testify the feasibility of the proposed controller.The experimental results show that pneumatic force servo system based on the proposed controller has high force tracking accuracy and quick response.

基于反步法的下肢外骨骼机器人控制研究

针对下肢外骨骼预定轨迹的控制问题,在构建了二自由度机械腿的运动学和动力学模型的基础上,提出了一种非对称液压缸负载力、伸缩量与外骨骼转动扭矩、运动角度的转化关系,采用反步法控制下肢外骨骼系统的运动轨迹。首先,采用D-H法建立了二自由度下肢外骨骼系统的运动学模型,研究了外骨骼末端执行器关节速度的变化关系,并利用拉格朗日动力学方程推导了外骨骼动力学的数学模型;然后,使用了液压缸负载力控制为机械腿运动提供了相应的扭矩,进而控制了下肢外骨骼的运动姿态;其次,针对下肢外骨骼运动时的高精度要求,利用反步法控制理论,建立了阀控非对称缸系统,结合下肢外骨骼动力学系统整体的状态空间方程,利用下肢外骨骼液压伺服系统控制了下肢外骨骼进行预定轨迹运动;最后,对AMESim软件与Visual Studio软件进行了联合仿真,对比分析了PID控制与反步法控制的精度问题。研究结果表明:针对下肢外骨骼预定轨迹控制,反步法控制误差最大值为2°,对比传统PID控制,误差降低了67%;设计的反步法控制器对于下肢外骨骼具有良好的控制精度。

机械反馈式伺服阀流量测试动态缸参数选用分析

相比电反馈伺服阀动态特性可直接通过阀芯位移响应测试获得,机械反馈式流量伺服阀的动态特性,通常需利用动态缸作为流量传感器间接测量获得。测试结果受动态缸泄漏、阻尼、质量惯性等固有非理想化因素的影响,通常无法准确表达伺服阀本身的性能指标。基于一套实际阀控缸系统,建立Matlab-Simulink仿真模型,解析获得的频带宽结果相比实测结果误差小于0.5%,由此建立了可准确表达阀与缸性能特性的仿真模型。在此基础上,理论给出了伺服阀本身的频率特性指标,即无泄漏无阻尼及无限刚度动态缸条件下的系统频率特性。以此为依据,分析了实际动态缸活塞质量、活塞粘性阻尼以及泄漏变化情况下,阀控缸系统频率特性偏离理想条件的变化规律。

钢支撑轴向力伺服油缸优化设计

针对钢支撑轴力伺服油缸在大腔压力波动时无法定性监测围护变形量的问题,采用内置压力传感器和MT磁致式位移传感器优化钢支撑伺服油缸结构,同时采集油缸大腔压力和位移信号,当大腔压力变化量ΔP、油缸活塞杆位移ΔS均超过预设量时,系统发出预警信号,实践证明,此方案能极大地降低原系统误预警的频率,并能保证施工围护的变形量,验证了设计模型的可行性,可为钢支承轴向力伺服油缸的结构设计提供参考。

基于伺服液压缸X形密封圈的数值模拟

针对伺服液压系统中的执行元件伺服液压缸活塞中的X形密封圈,采用有限元分析软件ANSYS建立其二维轴对称有限元模型,研究X形密封圈在沟槽圆弧半径、流体压力、初始压缩率不同参数的条件下,对Von Mises应力、主接触面最大接触压力大小的影响。结果表明:内行程时沟槽圆弧半径为2.6 mm时密封性能最佳,外行程时沟槽圆弧半径为2.2 mm时密封性能最佳;X形密封圈在流体压力为10~20 MPa的范围内密封性能逐渐变差;初始压缩率为5%~15%时密封性能逐渐变好。

冶金高频响高精度伺服液压缸性能测试系统软件开发

采用LabVIEW与MATLAB函数结合的方法,开发了冶金高频响高精度伺服液压缸性能测试系统。根据生产冶金高频响高精度伺服液压缸对其动静态性能指标要求,该测试系统功能模块包含最低起动压力测试模块、带载动摩擦力测试模块、阶跃响应测试模块、频率响应测试模块、偏摆测试模块,各项测试结果通过研华数据采集卡PCI-1742U、PCI-1723与SSI-RS485电流变送器转换采集MST位移传感器信号与AB相脉冲传感器信号;该测试系统能够对测试的数据进行实时跟踪显示、存储或查询;此外,该系统还具有数据导出、打印实验报告等辅助功能。实验证明,该测试系统具有较高的实时性与可操作性,填补了其他系统所空缺的针对于大直径冶金高频响高精度伺服液压缸的偏摆测试模块,同时该测试系统具有更高的稳定性,解决了技术人员对原有测试系统操作复杂的难题,实现“傻瓜式”操作,更加智能化、可视化、及时化。

基于H_(∞)控制器的阀控非对称缸位置伺服系统控制

以阀控非对称缸位置伺服系统为研究对象,建立其数学模型;针对负载突变及油液弹性模量变化提出了H∞鲁棒控制方法,从频域上分析了控制器对系统动态性能和稳态性能的影响。采用AMESim和MATLAB/Simulink搭建了阀控非对称缸位置伺服系统的联合仿真模型,对不同工况下控制器的跟踪精度及抗扰能力进行仿真研究。最后,通过油缸加载实验测试平台对仿真结果进行进一步验证。结果表明:所设计的H∞控制器提高了系统的快速性和鲁棒性,相比于PID控制下系统正弦响应结果,H∞控制器的最大跟踪误差在无负载工况下降低了48.8%,在负载突变工况下降低了56.25%;同时阶跃响应时间缩短了7.5%。

非对称液压缸位移伺服系统的复合控制策略与试验研究

非对称液压缸的位移伺服系统存在两腔作用面积不等、系统模型不确定等特点,给液压缸高精度位移跟踪控制造成了巨大的困难。对此,提出以速度前馈为主与位移反馈为辅的复合控制策略。设计一种新的以控制电流和阀口压差为自变量的伺服阀流量计算模型,并根据该模型设计液压测试回路,通过测试结果辨识模型中的参数。根据伺服阀流量模型与目标位移轨迹计算速度前馈控制量。基于PI控制求出位移误差反馈控制量。最后,将速度前馈和位移反馈控制量相叠加作为伺服阀的驱动电压。通过试验得出在复合控制策略下液压缸位移跟踪的最大误差与目标位移幅值之比为2.1%,相对PID控制跟踪误差明显减小。提出的控制策略为生产实际中非对称液压缸的位移跟踪控制提供了一种简单、有效的方法。

基于双层CESO的电液伺服系统线性自抗扰控制

针对含高频噪声的阀控非对称缸不确定扰动抑制问题,采用扰动频率分层技术,利用线性扩张状态观测器低通滤波特性以及扰动估计速度和精度与带宽取值正相关性的特点,提出一种基于双层级联扩张状态观测器的阀控非对称缸电液伺服系统线性自抗扰方法。在分析双层级联线性扩张状态观测器稳定性基础上,与传统线性自抗扰控制方法进行了仿真对比研究。仿真结果表明:该控制方法继承了传统自抗扰控制优点,提高了不确定扰动估计速度和精度,有效抑制了含高频测量噪声不确定扰动带来的不利影响,可实现阀控非对称缸电液伺服系统的高性能控制。