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.     

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.     

基于神经网络控制算法的气动伺服系统运动分析研究

提出了一种神经网络控制方法并通过对气动伺服系统的无杆气缸运动控制,探究此控制方法的控制精度。由于受空气可压缩性、摩擦力以及启动系统的扰动等非线性因素的影响,气动伺服系统很难去建立精确的数学模型。根据系统的非线性特点及PID控制不足,基于BP神经网络控制,设计神经网络PID控制器,并进行实验。通过实验,对无杆气缸的运动特性分析,表明这种控制策略可以更好控制气动伺服系统的运动精度。     

Trajectory tracking control of a pneumatic X-Y table using neural network based PID control

This paper deals with the use of Neural Network based PID control scheme in order to assure good tracking performance of a pneumatic X-Y table. Pneumatic servo systems have inherent nonlinearities such as compressibility of air and nonlinear frictions present in cylinder. The conventional PID controller is limited in some applications where the affection of nonlinear factor is dominant. In order to track the reference model output, the primary control function is provided by the PID control and then the auxiliary control function is given by neural network for learning and compensating the inherent nonlinearities, A self-excited oscillation method is applied to derive the dynamic design parameters of a linear model. The experiment using the proposed control scheme has been performed and a significant reduction in tracking error is achieved.     

气动位置控制系统分数阶控制器的设计与仿真

为了实现对气动伺服控制系统的准确位置控制，设计了气动伺服系统，根据系统的组成推导了其数学模型，并在此基础上进行线性化处理，计算出传递函数。继而设计了一种基于稳定裕度法整定参数的分数阶控制器，使用MATLAB的优化工具箱求解控制器参数并在Simulink中搭建分数阶控制器模型进行仿真分析。结果表明，使用稳定裕度法整定参数的分数阶控制器对气动伺服系统具有良好的控制效果，在系统参数发生较大变化时仍能达到理想的控制性能指标，系统仍具有良好的信号跟踪特性、强抗干扰能力和鲁棒性。实验测得采用分数阶控制器的气动伺服系统定位精度达到0.5 mm，系统具有较高的稳态精度。     

Position control of a rodless cylinder in pneumatic servo with actuator saturation

In this paper, positioning control of a rodless cylinder in pneumatic servo systems with actuator saturation is investigated via an active disturbance rejection control. A linear extended state observer is designed to estimate and compensate strong friction force and other nonlinearities in the pneumatic rodless cylinder system. An actuator saturation linear feedback control law is developed to further improve the control performance. Furthermore, a linear matrix inequality-based optimization algorithm is employed to estimate a strictly invariance set for the closed-loop system. Experiment results with response time 0.5 s and accuracy 0.005 mm for a 200 mm step signal demonstrate the effectiveness of the proposed control strategy.     

Development of a piezoelectric high speed on/off valve and its application to pneumatic closed-loop position control system

The use of smart materials-based high speed on/off valve has exhibited the potential to replace traditional servo and proportional valves in fluid power systems. In this paper, a novel pneumatic high speed on/off valve driven by a piezoelectric stack actuator is developed and its dynamics are studied. For an upstream gauge pressure of 0.5 MPa, the valve exhibited a large flow rate of up to 86 L/min. Furthermore, to study the ability of this novel high speed on/off valve to be applied in closed-loop control systems, a real-time position control system is realized using a PID controller. In order to prove its feasibility and effectiveness, a number of closed-loop trajectory tracking experiments are conducted on a pneumatic cylinder. The system is proved feasible and the results demonstrate good tracking performance.

     

Development of a digital control system for high-performance pneumatic servo valve

Pneumatic servo systems are used in many fields, such as pneumatic robot systems or vibration isolation systems. To improve the controllability of the pneumatic servo system, a higher performance servo valve is needed.In the present paper, a pneumatic spool type servo valve having an air bearing and a high-resolution position sensor was developed. We attempted to achieve high-frequency, high-accuracy flow rate control by digitization of the controller. We present herein a control algorithm for digital control of this valve.The characteristics of this valve were measured and the natural frequency of the valve was clarified to be up to 300 Hz. The spool position accuracy and the dynamic characteristics of the developed servo valve are greatly improved compared to existing valves.     

气动位置伺服系统的自适应控制研究

提出采用两个电－气压力比例阀构成新颖的阀控缸气动位置伺服系统,并运用极点配置的自校正自适应控制方法实现了气缸活塞位移的实时控制。研究结果表明,这种气动位置伺服系统比采用电－气流量比例阀的气动位置伺服系统具有较高的刚度和较好的控制性能;运用自适应控制方法的气动位置伺服系统具有较强的跟踪能力和抗参数扰动的鲁棒性。     

双电机消隙技术在串联机械臂中的仿真与应用

典型非线性齿隙广泛存在于机器人伺服系统中，为了减小齿隙对系统性能的影响，对串联机械臂采用双电机主从驱动消隙技术。首先基于双电机消隙系统的基本原理及结构建立了齿隙弹性死区非线性模型；然后根据双电机系统的动力学推导公式，建立了所采用的双电机偏置力矩消隙控制策略的Simulink模型，并给出了系统的算法框架及伺服系统硬件电路原理；最后根据实际工程设计参数数据进行原理仿真，并通过激光跟踪仪对采用双电机消隙技术的串联机械臂系统进行精度测试实验验证。仿真及实验结果表明：建立的数学模型能够反映实际系统的基本特性；工作空间为4.5 m的串联机械臂末端精度达到1.2 mm，满足工程应用性能指标要求。     

基于AMESim和Simulink的气动位置伺服系统PID控制

根据AMESim和MATLAB软件各自的特点,采用了AMESim和MATLAB对气动位置伺服系统PID控制进行仿真,并在仿真中分别对有无PID控制器的气动位置伺服系统进行对比。结果表明,PID控制的气动位置伺服系统稳态精度较高,调节时间短,超调小,可以克服非线性时变特性的影响。     

用气液伺服系统改进气动进给性能

提出了一新型气液缸和用廉价开关阀实现ＰＣＭ控制的气液伺服系统。采用气液连动控制,充分发挥液压与气动各自的优点,大大提高了位置控制精度,改进了气动伺服系统的性能。     

用于气动伺服系统的自适应神经模糊控制器

研究了一种基于压力比例阀的气动伺服系统自适应神经模糊控制器。其中的神经网络辨识器（NNI）通过高线训练可以充分逼近非线性动态系统的模型,并能够在线调整模糊控制器的控制规则。系统的位置控制精度和伺服特性有了很大改善。试验结果表明,所提出的控制器对该气动伺服系统具有很好的控制特性以及很强的自适应能力。     

无模型控制器在气缸压力控制系统中的应用研究

气动伺服系统存在纯时延、非线性、时变等特点,传统的控制策略(如PID控制)在解决非线性系统时效果不理想,因此提出一种无模型控制算法。此方法在被控对象结构复杂、参数时变时控制效果较好。首先对气动伺服系统进行建模,建模过程包括阀口流量、比例流量阀及缸内压力建立一个二阶模型;其次设计无模型自适应控制器(Model-Free Adaptive Controller,MFAC)用于气动伺服系统压力控制;最后利用LabWindows/CVI平台进行试验验证。结果表明,针对气动伺服系统设计的无模型控制器是有效的,相比于传统PID控制有更快的响应速度和更高的控制精度。     

基于单神经元控制器的气动位置伺服系统研究

针对气动位置伺服系统特点,提出采用比例流量阀作为系统电－气转换元件,并采用单神经元控制器（ＳＮＣ）来实现活塞位移的实时控制。仿真和实验研究表明,这种气动伺服系统具有强鲁棒性,快速跟踪性和较好的控制精度,其重复定位精度小于０．２ｍｍ。     

基于模糊自整定PI与重复控制的气动伺服系统研究

针对气动位置伺服控制中的低精度、低刚度等问题,提出了一种重复补偿与模糊自整定PI相结合的复合控制方案。利用模糊控制器提高系统的动态性能和鲁棒性,通过重复控制器周期性地修正输出电压,以改善系统的稳态特性,实现优势互补,使系统获得良好的稳、动态性能。通过仿真试验表明,该控制算法容易实现,且能更好地提高气动伺服定位系统的跟踪精度,具有较强的实用性。     

Precision position control of servo systems using adaptive back-stepping and recurrent fuzzy neural networks

To improve position tracking performance of servo systems, a position tracking control using adaptive back-stepping control(ABSC) scheme and recurrent fuzzy neural networks(RFNN) is proposed. An adaptive rule of the ABSC based on system dynamics and dynamic friction model is also suggested to compensate nonlinear dynamic friction characteristics. However, it is difficult to reduce the position tracking error of servo systems by using only the ABSC scheme because of the system uncertainties which cannot be exactly identified during the modeling of servo systems. Therefore, in order to overcome system uncertainties and then to improve position tracking performance of servo systems, the RFNN technique is additionally applied to the servo system. The feasibility of the proposed control scheme for a servo system is validated through experiments. Experimental results show that the servo system with ABS controller based on the dual friction observer and RFNN including the reconstruction error estimator can achieve desired tracking performance and robustness.     

Multivariate nonnormal process capability analysis

Precise modelling of servo-pneumatic actuation plants continues to remain a major challenge. In this work, the complete mathematical model of a double-acting pneumatic cylinder with cushioning sections at both ends of the piston stroke has been developed. The proposed model considers the entire stroke of the piston, including cushioning sections as these sections affect the positioning accuracy of the piston. A pulse width modulation algorithm has been applied to control the position of the pneumatic cylinder. Computer simulation and experimental tests have been carried out on the developed model. The results of simulation and experimental studies have been shown to yield a better performance compared with existing mathematical models.     

Intelligent switching control of pneumatic cylinders by learning vector quantization neural network

School of Mechanical and Automotive Engineering, University of Ulsan, San 29, Muger2-dong, Nam-gu, Uhan 680-749, Korea The development of a fast, accuiate, and inexpensive position-controlled pneumatic actuator that may be applied to various practical positioning applications with various external loads is described in this paper A novel modified pulse-width modulation (MPWM) valve pulsing algorithm allows on/off solenoid valves to be used in place of costly servo valves A comparison between the system response of the standardPWM technique and that of the modified PWM technique shows that the performance of the proposed technique was significantly increased A state-feedback controller with position, velocity and acceleration feedback was successfully implemented as a continuous controllei A switching algorithm foi control parameters using a learning vector quantization neural network (LVQNN) has newly proposed, which classifies the external load of the pneumatic actuator The effectiveness of this proposed control algorithm with smooth switching control has been demonstrated thiough experiments with various external loads     

新型集成电气伺服坐标气缸的研究及其应用

本文研究的是集驱动机构、位移传感器、控制阀及控制连接为一体的新型伺服气缸,对气缸的综合性能,特别是气缸的摩擦力进行了深入的研究,可为高性能气动伺服系统提供优质的气动集成元件,大大缩短了气动伺服系统的设计周期。