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.     

电控气动式AMT系统分析建模

为了实现自动机械变速器(AMT)快速、光滑地气动换挡,分析了AMT系统动力传动情况,结合影响换挡品质的主要因素,确定了AMT气动伺服控制的关键阶段。建立AMT气动系统非线性模型,包括气缸输出刚度动态模型。引入改进的LuGre摩擦模型,并通过试验辨识其相关的动、静态参数。提出了一种离合器负载特性估计的新方法,从而构建电控气动式AMT系统完整的数学模型。     

气动执行器与电动执行器的生命周期评价研究

基于生命周期理论,对气动执行器与电动执行器的整个生命周期内总的成本费用、总的能耗和总的污染物排放量进行了研究,提出了衡量产品全生命周期成本的一种新的模型;同时给出了基于动态的两个执行器在整个生命周期中总的能耗、总的污染物排放量的计算方法。     

气动位置伺服系统建模发展综述

由于气体的压缩性、气缸摩擦力等存在因素，气动位置伺服系统是一个非线性系统。本文按照机理分析、系统辨识、机理分析和系统辨识结合三种方法简要介绍了气动位置伺服系统建模的发展情况。文章分析得出气动位置伺服系统的模型由线性到非线性．建模目的从理论研究到实际应用的方向发展。最后提出了气动位置伺服系统建模待解决的问题。     

气动放大器质量流量的机理建模

气动放大器既是常用的独立电气附件又是阀门定位器的关键部件之一。建立了一种典型气动放大器质量流量机理模型,并提出参数辨识的方法。首先,根据气动放大器的工作原理和结构特点,运用热力学和流体力学原理,建立了气动放大器的质量流量模型;其次,通过实验研究对等效节流面积这一重要参数建立了新的子模型,并进行参数辨识;最后借助控制阀实验平台,对所建模型进行验证。结果表明,与实际典型气动放大器相比,所建立的模型准确度高达90%。     

机械压力机节能型气压式制动方式设计理论

在分析现有机械压力机制动方式存在耗能耗材的不足基础上,提出机械压力机节能型气压式制动系统,并论述其工作原理。通过对机械压力机采用节能型气压式制动方式工作过程的分析,建立由气体的能量方程、流量连续方程、状态方程和制动气缸制动过程的动力学方程组成的数学模型。通过对节能型气压式制动气缸内气体热力学特性的分析,建立制动过程中制动力及制动功的计算公式。针对JH23-63型630 kN机械压力机,研制节能型气压式制动装置,并试验验证了该数学模型的正确性、实用性和可靠性。     

基于Weibull分布的小型气缸可靠性分析

在气动系统应用中,气缸作为最多的一种执行机构,其可靠性是实现整个系统安全、可靠的前提。以某小型高速气缸的常规寿命试验为基础,通过对气缸的失效机理分析,确定其失效模型。根据可靠性统计方法确定气缸寿命的具体分布形式。利用中位秩法对失效数据进行预处理,提出利用计算机实现可靠性特征参数的最小二乘估计的方法,并在此基础上建立了气缸可靠性分析模型。应用此模型可以得到气缸的可靠度分布,为气缸的可靠性定量分析提供了一种可行的方法。     

Measurement of friction force in pneumatic cylinders

Although the performance and reliability of pneumatic cylinders depend to a great extent on the friction generated at the seals, the friction characteristics have not been widely studied. Both the literature and manufacturers' catalogues rarely discuss the friction characteristics of pneumatic cylinders, and the lack of friction models limits the design, optimisation, and analysis of pneumatic cylinder systems. In seeking to improve the characteristics of pneumatic cylinders and to clarify the friction phenomenon, this paper describes friction force measurement tests carried out in pneumatic cylinders of six different diameters, from 32 to 100 mm. An experimental apparatus was designed to assess the effect of a broad range of operating conditions, where the velocity and pressure of the cylinder chambers are controlled independently. Measurements of friction force are shown for velocities of up to 0.5 m/s and pressures of up to 0.8 MPa. The data obtained will be useful for developing a suitable friction model, and the experimental apparatus will allow study of the effects on the friction force of different types of seal, lubricant, and cylinder barrel.     

气动人工肌肉系统动态特性研究

提出将气动人工肌肉视为带有弹性负载的变截面气缸的观点，方便地建立了气动人工肌肉系统动态数学模型。将气动人工肌肉的工作过程划分为等客充气、充气收缩、排气伸长和等容排气四个部分，通过仿真和实验研究对气动人工肌肉进行了特性分析。实验结果表明了所建立的动态数学模型的正确性，为气动人工肌肉应用研究奠定了基础。     

Review of techniques for the mass flow rate measurement of pneumatically conveyed solids

An accurate, reliable, on-line, continuous and non-invasive measurement of solids’ mass flow rate in pneumatic conveying pipelines has been a technically challenging area, which becomes increasingly significant to achieve efficient utilization of energy and raw materials and to reduce waste. Energy and environmental regulation and legislation, and efficiency and waste reduction are two most powerful drivers in the academic research and industrial applications for solids’ mass flow meters. In this paper, a review is presented on the recent measurement techniques of solids’ mass flow rate measurement in pneumatic conveying systems. On basic principle and configuration of each technique, performances and limitations of these techniques in industrial applications are analyzed and compared from different views to demonstrate the recent developments in the field and the possible approaches which may provide solutions to the solids’ mass flow measurement problem.     

基于神经网络的气缸压力识别研究

对传统的内燃机气缸压力识别方法存在的问题 ,提出了应用人工神经网络方法进行气缸压力识别的新方法。以 BP网络构造气缸压力识别模型。通过对网络的训练 ,用实测的缸盖振动信号识别气缸压力。结果表明 ,利用神经网络进行内燃机气缸压力识别 ,识别结果的重复性好 ,精度较高     

基于自编码器和支持向量机的气压传动系统气缸泄漏故障诊断

气压传动系统在制造领域应用广泛,对智能化故障诊断与节能有较大需求。泄漏是气动系统最常见的故障类型及能量浪费的最主要因素之一。以最具代表性的执行元件气缸为研究对象,通过对其上游压力与流量信号进行处理分析,实现对下游气缸常见的内外泄漏故障的有效诊断。信号特征提取通过栈式自编码器完成,提取的特征进行聚类处理评估后送入支持向量机(Support Vector Machine, SVM)分类器进行分类,从而对气缸泄漏故障进行分类和定位。结果表明：通过分析上游信号来确定下游元器件故障状态是可行的;且对于泄漏故障实验,在同等条件下,基于流量信号的平均分类准确率可达到96%,基于压力信号的平均分类准确率为87%。     

Adaptive Robust Tracking Control of Pressure Trajectory Based on Kalman Filter

When adaptive robust control(ARC) strategy based on backstepping design is applied in pneumatic servo control, accurate pressure tracking in motion is especially necessary for both force and position trajectories tracking of rodless pneumatic cylinders, and therefore an adaptive robust pressure controller is developed in this paper to improve the tracking accuracy of pressure trajectory in the chamber when the pneumatic cylinder is moving. In the proposed adaptive robust pressure controller, off-line fitting of the orifice area and on-line parameter estimation of the flow coefficient are utilized to have improved model compensation, and meanwhile robust feedback and Kalman filter are used to have strong robustness against uncertain nonlinearities, parameter fluctuations and noise. Research results demonstrate that the adaptive robust pressure controller could not only track various pressure trajectories accurately even when the pneumatic cylinder is moving, but also obtain very smooth control input, which indicates the effectiveness of adaptive model compensation. Especially when a step pressure trajectory is tracked under the condition of the movement of a rodless pneumatic cylinder, maximum tracking error of ARC is 4.46 kPa and average tracking error is 0.99 kPa, and steady-state error of ARC could achieve 0.84 kPa, which is very close to the measurement accuracy of pressure transducer.     

高压气动系统负载容腔压力伺服控制仿真研究

为满足某气体发生系统安装空间小、重量轻、动态响应快、控制精度高等要求,设计了高压气动压力伺服控制系统,并采用高压电-气伺服阀实现了负载压力的高响应高精度控制。建立了系统数学模型,包括高压气瓶热力学方程、高压电-气伺服阀传递函数与流量方程、负载容腔压力变化与排气流量方程等子模型,并设计了反馈线性化PID控制器。基于MATLAB/Simulink平台建立了高压气动系统仿真模型,仿真研究了高压气瓶容积与初始气源压力、负载容腔排气孔通径等参数对系统负载压力控制性能的影响规律。研究结果为该系统的优化设计与实验研究提供重要理论依据。     

气压位置控制系统研究现状及展望

回顾了气压位置控制系统的研究历史,总结了在基本特性研究、控制阀开发和控制策略研究方面的工作。研究工作表明：气体通过阀口和管道的流动复杂、缸内热力过程为指数变化的多变过程、摩擦力与系统运动速度、驱动压力和背压有关。在开发了相关控制阀后,进行了针对系统的各种特性的控制策略的研究,如针对非线性的非线性补偿措施、针对摩擦力的振颤补偿、针对模型误差的鲁棒设计和针对开关阀系统的同向PWM设计等,效果明显。研究工作使得气压位置控制系统已具有良好的性能,能满足工业生产的需要。     

基于Stribeck模型的摩擦颤振补偿

针对摩擦力给气动比例系统带来的稳态误差和低速爬行问题,从实用角度来探索解决非线性摩擦力补偿的方法。基于粘弹性理论及Stribeck模型建立气动比例系统的摩擦数学模型。将该摩擦模型引入阀控缸系统的动态模型中,建立完整的系统运动模型。将高频低幅颤振信号叠加于系统中,对系统的摩擦机理变化以及稳定性的影响进行分析。理论分析表明,叠加合适的颤振信号后,系统的部分静摩擦力转化为动摩擦力,最大静摩擦力减小,响应速度提高,从而将系统的粘滑运动转换为一种平稳运动。试验发现,当颤振信号频率为系统固有频率的3.3倍,系统的定位精度由原来的0.516mm提高到0.284mm,滞后时间由原来的0.17s缩短为0.02s。证明对气动比例系统提出的摩擦颤振补偿理论是正确的。     

带卸压槽的微摩擦气缸Fluent仿真分析

针对超低频模态测试悬挂系统中微摩擦气缸抗侧向能力不足的问题,提出一种在活塞尾部增加环形卸压槽的新结构。建立了活塞外表面与气缸内表面之间气膜流场特征参数的仿真模型,并进行Fluent仿真计算,结果表明,增加环形卸压槽改善了气膜的气压分布,在两排节流孔之间形成了具有一定宽度且稳定的承载区,使活塞的轴线与气缸的轴线基本保持平行,提高了抗侧向能力及气膜刚度,从而使气缸工作更为稳定。试验结果进一步验证了仿真结果,证明带环形卸压槽的微摩擦气缸的性能得到了提高。     

基于AIC准则的气动位置控制系统辨识

为了解决气动位置控制系统的精确定位,提出了一种基于AIC准则的气动位置控制系统辨识。通过对气动位置控制系统分析,建立了系统数学模型,并进行了线性化处理。基于AIC准则建立了白噪声和有色噪声两种模型,找到了满足两种模型最小的阶次,采用增广最小二乘法实现对有色噪声参数的无偏估计;通过自相关系数检验了系统残差序列的白色性,验证了气动位置控制系统辨识模型的可靠性。实验结果表明:当幅值分别为1000 A和1200 A时,两种系统的传递函数基本等价,说明在相同阶次的逆M序列且幅值在一定范围内,不同系统对模型参数的辨识影响较小。     

Practical and intuitive controller design method for precision positioning of a pneumatic cylinder actuator stage

The present paper describes a practical and intuitive controller design method for precision positioning of pneumatic cylinder actuator stages. Pneumatic actuators are easy to use and have numerous advantages, which has led to these actuators having a wide variety of applications. However, pneumatic actuators have notable nonlinear characteristics, which make precision positioning difficult to achieve. The purpose of the present study is to clarify a practical and intuitive controller design procedure for precision positioning of a pneumatic cylinder actuator. In addition to positioning performance, the present study focuses on the realization of easy controller design without the need for the exact model parameters or knowledge in control theory for general-industrial-use pneumatic cylinder actuators with friction characteristics. These considerations are important in order to fully exploit the advantages of pneumatic cylinder actuators in a wide variety of applications. As such, three elements are added to the conventional continuous-motion nominal characteristic trajectory following (CM NCTF) controller. A new design procedure of the improved CM NCTF controller for pneumatic cylinder actuator stages is introduced, and the positioning performance of the designed control system is examined experimentally under several conditions. The positioning results generally indicate a positioning error of 50 nm, which is equal to the sensor resolution.     

气压式连杆机械的动力性能和动态仿真研究

以机构动力学和气压传动动力学为理论基础，建立了描述气压式连杆机械系统的数学模型，求得在气压驱动下连杆机构的动力学参数随时间的变化规律，对气压式连杆机构的运动学动力学参数进行了实时动态仿真。分析了差动阀行程、通道直径和工作腔流量系数对机构动特性的影响。