A review on recent research trends in servo pneumatic positioning systems

Servo pneumatic systems are widely utilized for obtaining accurate position control in many industrial drives. Such technology has the potential to replace electro mechanical and hydraulic drives in many applications. The main drawback of this technology is the high nonlinear nature of pneumatic drives which affects the system dynamics. It is very necessary to enhance the pneumatic drives by reducing its stochastic nature. The major causes for the non-linearity in pneumatic drives are owing to the pressure dynamics inside the pneumatic cylinder chambers, the frictional force variations and the compressed air flow rates through the valves. In the present study, an endeavor has been made to perform a detailed survey on various aspects in the efficient position control of the pneumatic cylinder. The history, applications, performance tests, component selection, modelling and accurate control of the servo pneumatic systems have also been discussed with the aim to improve the efficiency and the positioning accuracy of the linear pneumatic drive. It has been inferred that a lot of research attentions has to be given for enhancing the performance measures in servo pneumatic positioning systems by reducing the nonlinear nature of the pneumatic systems.     

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.     

气动手爪伺服系统设计

机械手爪是机械手执行机构中的重要部件,其性能的优劣将直接影响到整个系统的作用和效率。为了分析机械手爪抓取易碎物体时的运行机理．以SMC公司MHZ系列气动手爪为例,阐述了气动手爪的结构及工作原理,分析了气动手爪的运动方程,推算了系统的传递函数,建立了系统的AMESim仿真模型,并对系统进行了仿真分析及校正,结果表明设计是正确合理的。     

气动伺服定位技术及其应用

１前言随着工业自动化技术的发展,传统气动系统只能在两个机械设定位置可靠定位并且其运动速度只能靠单向节流阀单一设定的状况,经常无法满足许多设备的自动控制要求。因而电－气比例和伺服控制系统,特别是定位系统得到了越来越广泛的应用。因为采用电－气伺服定位系统...     

气动伺服机械手控制系统的设计

针对气动伺服机械手控制系统开发应用过程中出现的精度控制难等问题,设计了一种以模糊PID控制策略结合专家判断为控制手段的控制方案,阐述了该方案的控制系统组成、软件设计以及实现方法。实际运行表明本系统响应速度快,控制精度高。     

柔顺气动手爪伺服系统设计

阐述了气动手爪伺服系统的结构及工作原理,对部分重要器件进行了选型,分析了控制回路的结构及原理,在AMESim中建立了系统的数学模型并进行了仿真,仿真结果表明设计是合理、科学的.     

An approach to improve the GPS positioning performance under urban environment conditions

Satellite deficiency degrades the performance of GPS single point positioning (SPP) in city urban areas. If the number of observed satellites is smaller than that of the unknown independent parameters in the data processing, extended Kalman filter (EKF) methods will usually be employed to transit the variable values epoch by epoch. In this case, the prediction model in EKF is very important for the positioning results. This paper focuses on the receiver clock offset models in the prediction equation. The investigation shows that, the clock offset model with clock shift is able to improve the accuracy of the clock offset prediction for internal crystal clocks within a short time span, compared with the clock offset model without clock shift. Besides, in order to further improve the performance of positioning in the case of satellite deficiency, an adaptive EKF is developed to enhance the clock prediction. The experiments show that this approach can improve the positioning accuracy in the scenarios that only fewer satellites are available.     

Single line CCD camera to improve positioning

This article describes an opto-electronic device that allows on-line visualization of the optical intensity function along a strip. The use of a linear optical charge-coupled device (CCD) array eliminates all moving parts. This makes adaptation to a standard microscope possible without modifications. The setup described here is essential where precise positioning of a reference graticule on diffuse lines must be performed.     

角度伺服阀芯阻力矩的测试与研究

就新型液压伺服关节中内置伺服阀芯阻力矩问题进行了探讨.在理论分析的基础上,建立了伺服阀芯阻力矩测试的实验系统,应用支反力法测得了实验数据,并对测试结果进行了比较分析,得出了摩擦阻力矩与系统压力的关系曲线,为选择合适的步进电机,进而进行结构设计打下了基础.     

气动手爪位置伺服系统的建模与仿真

通过对气动手爪位置伺服系统进行分析,建立了气动手爪的位置伺服系统数学模型。采用Matlab/Simulink仿真软件对所建立的系统数学模型进行仿真得出,此位置伺服系统结合模糊自适应PID控制方法,可以使气动手爪以较短的调整时间来抓取易碎、易变形的物体。     

气动伺服系统自适应控制方法研究

气动伺服系统是一个具有较强非线性的系统,传统控制理论对气动系统的精确控制具有较大的难度。本文分别采用极点配置自适应控制法和组合自校正控制器控制法对气动伺服系统进行了研究。结果表明,相对于极点配置自适应控制法而言,组合自校正控制器自适应控制法能有效地抑制摩擦力等扰动因素对气动系统的影响,从而能提高气动系统的抗干扰鲁棒性和定位精度。     

三自由度液压伺服关节样机的试验系统研究

初步探讨新型三自由度液压伺服关节试验系统的构建与试验.在研制试验样机的基础上,对关节试验系统所涉及的一些基本问题、方法及分析进行阐述,通过试验验证关节的基本性能.     

液体静压浮动导轨

介绍一种具有浮动支承的液体闭式静压导轨的工作原理与设计计算。     

单片机控制脉宽调制在气动调压阀中的应用

介绍了使用C8051F310单片机的捕捉比较模块中的脉宽调制方式,通过软件编程控制两个高速开关阀,以及由压力传感器组成的闭环系统,以实现对气动调压阀的比例控制。     

基于极点配置自校正的气动位置系统控制策略研究

为了提高比例流量阀控摆动气缸旋转位置系统性能,提出了基于极点配置自校正的控制算法。建立了被控系统数学模型,该系统存在严重的非线性,系统参数随工作点的变化而变化。通过带固定遗忘因子的最小二乘辨识算法在线辨识系统参数,使用极点配置自校正的控制算法将被控系统的极点配置到希望的位置,实现实时的自适应控制。实验研究表明,基于该控制策略的气动旋转位置系统具有较好的动态性能和跟踪能力。     

Adaptive backstepping slide mode control of pneumatic position servo system

With the price decreasing of the pneumatic proportional valve and the high performance micro controller, the simple structure and high tracking performance pneumatic servo system demonstrates more application potential in many fields. However, most existing control methods with high tracking performance need to know the model information and to use pressure sensor. This limits the application of the pneumatic servo system. An adaptive backstepping slide mode control method is proposed for pneumatic position servo system. The proposed method designs adaptive slide mode controller using backstepping design technique. The controller parameter adaptive law is derived from Lyapunov analysis to guarantee the stability of the system. A theorem is testified to show that the state of closed-loop system is uniformly bounded, and the closed-loop system is stable. The advantages of the proposed method include that system dynamic model parameters are not required for the controller design, uncertain parameters bounds are not need, and the bulk and expensive pressure sensor is not needed as well. Experimental results show that the designed controller can achieve better tracking performance, as compared with some existing methods.     

一种解决脉宽调制气动位置控制系统低频振荡的新方法

对ＰＷＭ气动位置控制系统在目标值附近的低频振荡现象做了解释,提出了设定位置控制死区,在控制死区内将对气缸活塞位置的控制转为对气缸两腔压差的控制,从而消除了这种现象。实验结果表明效果是十分明显的。     

An energy-saving nonlinear position control strategy for electro-hydraulic servo systems

The electro-hydraulic servo system (EHSS) demonstrates numerous advantages in size and performance compared to other actuation methods. Oftentimes, its utilization in industrial and machinery settings is limited by its inferior efficiency. In this paper, a nonlinear backstepping control algorithm with an energy-saving approach is proposed for position control in the EHSS. To achieve improved efficiency, two control valves including a proportional directional valve (PDV) and a proportional relief valve (PRV) are used to achieve the control objectives. To design the control algorithm, the state space model equations of the system are transformed to their normal form and the control law through the PDV is designed using a backstepping approach for position tracking. Then, another nonlinear set of laws is derived to achieve energy-saving through the PRV input. This control design method, based on the normal form representation, imposes internal dynamics on the closed-loop system. The stability of the internal dynamics is analyzed in special cases of operation. Experimental results verify that both tracking and energy-saving objectives are satisfied for the closed-loop system.     

气缸磨损原因与提高气缸使用寿命的措施

工程车辆大修是根据发动机气缸的磨损程度确定的，标准规定每100mm缸径磨损量超过0.40mm就应进行大修。因此，探明气缸的磨损规律和原因，从而采取有效措施延长发动机的使用寿命十分必要。