气缸摩擦力测试系统开发

为准确测量气缸的实际摩擦力,本文建立了一个基于伺服电机速度控制的气缸摩擦力测试台,实现了测试过程中被测气缸运行速度和两腔压力的独立控制.系统采用多线程的流水线并行处理方式,在保证了采样数据完整性和操作实时性的同时,大大提高了系统的效率;同时系统实现了批处理测试的功能,从而简化测试操作,减少失误.实验表明,该测试平台测试方法合理,测试范围较广,测试精度和效率较高,操作和维护方便.     

A method of accurate position control with a pneumatic cylinder driving apparatus

In this paper, a method of accurate position control using a pneumatic cylinder driving apparatus is presented. To overcome the effect of friction force and transmission line, low friction type cylinder applied externally pressurized air bearing structure is used and two control valves attached both side of the cylinder directly. To compensate nonlinear characteristics of control valves, linearized control input derived from the relation between control input and effective area of control valve, and dither signal are applied to the valve. The controller applied to the pneumatic cylinder driving apparatus is composed of a state feedback controller and a disturbance observer. Experimental results show that the effectiveness of the proposed method and position control error of 5 μm accuracy could be obtained easily.     

Experimental and numerical study of friction in an elastomeric seal for pneumatic cylinders

The behaviour of an elastomeric seal for a pneumatic cylinder piston is analysed in this work. The aim of the paper is to validate experimentally a numerical approach to evaluate seal performance, in actual working conditions.The friction force between seal and the cylinder bore is evaluated through experimental tests and numerical simulations, using a finite element model. Working conditions are simulated for different piston rod velocity and cylinder supply pressure, both in dry conditions, boundary and fluid lubrication conditions. Simulation is obtained by an iterative process that uses the friction coefficient, experimentally measured, as a function of speed and lubrication conditions. Results obtained from experimental tests and numerical simulation are compared to determine the friction force between seal and cylinder bore.     

超声减摩技术及其在气动系统中的应用研究与展望

超声振动带来的减摩效应具有减摩效果好、控制方便、高效节能且无污染等优点,得到了国内外学者较为广泛和深入的研究,并已成功应用于提高加工质量、减小机械摩擦及改善仪器测量精度等领域。近几年这项技术也逐渐引起了气动领域相关学者的兴趣,研究表明超声振动对气缸摩擦力的改善有明显效果,同时为流体传动与控制领域研究学者提供了一种全新的摩擦与运动控制手段。该研究将从超声减摩的起源与发展入手,对气动领域中超声减摩的核心问题及未来研究的前景予以阐述。     

Application of response surface methodology on finding influencing parameters in servo pneumatic system

Servo pneumatic positioning system is a mechatronics approach that enables to use pneumatic cylinders as multi-position actuators. In the present study, an endeavor has been made to simulate the response of pneumatic cylinder parameters. Response surface methodology based analysis have been conducted to evaluate the influences of system parameters such as external load, supply pressure and cross sectional area of cylinder on the response characteristics such as settling time, maximum overshoot, integral time absolute error and maximum force generated using fuzzy rule base models. From the experimental results, it has been inferred that supply pressure has mostly influent nature on determining maximum overshoot and integral of time absolute error (ITAE). It has been observed that cross sectional area and external load has significantly affected the maximum generated force and settling time respectively.     

竖直运动平台气动配重的研究

提出了一种利用气缸推力对竖直方向运动的超精密运动平台进行配重的新方法,使电机趋动力减小,提高运动精度。建立了重物配重及气动配重的力学模型,指出重物配重时,电机的推力至少要能够克服摩擦力,而用气动配重方法,当平台运动方向发生变化时,改变气缸压力,使平台在垂直运动时所需的电机推力小,甚至达到零负载,使其运动精度得以提高。并给出了一种控制气缸推力的解决方案。     

金属间隙密封气缸寿命及失效模式试验研究

金属间隙密封气缸和一般橡胶密封气缸相比,具有低摩擦、高速和高频等特点。针对金属间隙密封气缸研制了一套寿命试验装置,详细介绍了试验装置的基本试验系统气动回路、测量系统气动回路和具体实现方法。最后,通过长期试验收集分析试验数据,对气缸失效临界值水平进行初步探讨。     

Simultaneous trajectory tracking control of position and force with pneumatic cylinder driving apparatus

In this study, a position and force simultaneous trajectory tracking control algorithm is proposed for a driving apparatus that consists of two pneumatic cylinders connected in series. The controller applied to the driving apparatus is composed of a non-interaction controller to compensate for interaction between cylinders and a disturbance observer aimed to reduce the effect of model discrepancy that cannot be compensated by the non-interaction controller. The effectiveness of the proposed control algorithm is proved by experimental results.     

液压缸非线性约束下的轧机辊系振动行为

以四辊板带轧机为例,分析液压压下缸及弯辊缸在轧机辊系振动时表现出的分段弹性力和摩擦力两种非线性约束,建立液压缸非线性约束作用下的轧机辊系振动模型,并采用平均法求得振动系统的幅频响应。通过比较两种非线性作用下辊系振动速度和振动幅值的仿真曲线,研究辊系受分段弹性力和摩擦力影响时的行为特性。取不同分段弹性力和摩擦力,仿真分析两种非线性因素分别对轧机辊系幅频特性的影响规律。结果表明,轧机辊系振动速度受分段弹性力大小影响,系统不稳定频率区域随分段弹性力增大而变宽;摩擦力较小时,对辊系振动行为影响表现为阻尼特性,较大时,摩擦力的非线性成为影响辊系振动行为的主要特性。该结论为轧机辊系振动控制提供了理论参考。     

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。     

Festo CLR气缸工作性能实验分析

本文对CLR气缸工作性能的实验研究,目的是为了满足数控机床气动随行夹具中气缸的旋转夹紧要求。利用PLC控制器、气阀、气缸、传感器等元器件搭建实验平台。对主要实验步骤进行详细分析,通过实验论证Festo CLR直线摆动夹紧气缸完全满足气动随行夹具工作要求。     

Adaptive robust motion trajectory tracking control of pneumatic cylinders with LuGre model-based friction compensation

Friction compensation is particularly important for motion trajectory tracking control of pneumatic cylinders at low speed movement. However, most of the existing model-based friction compensation schemes use simple classical models, which are not enough to address applications with high-accuracy position requirements. Furthermore, the friction force in the cylinder is time-varying, and there exist rather severe unmodelled dynamics and unknown disturbances in the pneumatic system. To deal with these problems effectively, an adaptive robust controller with LuGre model-based dynamic friction compensation is constructed. The proposed controller employs on-line recursive least squares estimation（RLSE） to reduce the extent of parametric uncertainties, and utilizes the sliding mode control method to attenuate the effects of parameter estimation errors, unmodelled dynamics and disturbances. In addition, in order to realize LuGre model-based friction compensation, the modified dual-observer structure for estimating immeasurable friction internal state is developed. Therefore, a prescribed motion tracking transient performance and final tracking accuracy can be guaranteed. Since the system model uncertainties are unmatched, the recursive backstepping design technology is applied. In order to solve the conflicts between the sliding mode control design and the adaptive control design, the projection mapping is used to condition the RLSE algorithm so that the parameter estimates are kept within a known bounded convex set. Finally, the proposed controller is tested for tracking sinusoidal trajectories and smooth square trajectory under different loads and sudden disturbance. The testing results demonstrate that the achievable performance of the proposed controller is excellent and is much better than most other studies in literature. Especially when a 0.5 Hz sinusoidal trajectory is tracked, the maximum tracking error is 0.96 mm and the average tracking error is 0.45 mm. This paper constructs an adaptive robust controller     

Analysis,Design, and Comparison of Different Types of Pistons for Sealless Pneumatic Cylinders and Valves

This article presents a theoretical and experimental analysis of sealless pistons featuring a special geometry capable of eliminating friction in pneumatic cylinders and valves. Three different piston geometries were investigated: tapered, stepped, and slot-pocket. Performance was evaluated for each geometry in terms of pressure distribution, leakage flow rate, and the self-centering force on the piston. The piston configuration that provides the best tradeoff between self-centering thrust and leakage flow rate in the air gap was also determined. The theoretical and experimental results obtained with the different piston designs were then compared.     

气缸冲击动力学建模与仿真分析

将气缸在行程末端的冲击问题看成一个由细长活塞杆、质量负载、活塞以及端盖组成的振动系统。首先应用弹性体的一维波动方程建立细长活塞杆纵向振动变形的数学模型,用模态叠加方法解析了冲击力、接触位移以及接触时间。然后利用非线性有限元软件LS-DYNA对气缸冲击过程进行数值仿真计算分析,详细研究了当驱动负载质量以及活塞初始冲击速度不同时,活塞冲击接触面接触合力和接触作用时间的变化情况。对比分析了理论解析解与LS-DYNA数值解,验证了解析解的准确性,得出了冲击力分别随速度和负载的变化规律;进一步对冲击振动响应进行了频率分析,并研究了气缸冲击力的变化原因。研究结果为气缸的设计和使用提供了理论和实际参考。     

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。     

活塞导向长度对油气悬架减振性能的影响

烛式油气悬架兼有主销的作用,所以通常具有2°～5°的安装内倾角,内倾角会造成油气缸承受横向力的作用,从而增大缸筒和活塞之间的摩擦力.摩擦力增大会影响油气缸的减振性和车辆乘坐舒适性,严重时会造成油气缸"摩擦锁死"现象,使油气缸失去减振能力.以某矿用自卸车的烛式油气悬架为研究对象,通过理论分析了缸筒和活塞之间摩擦力的影响因...     

Misalignment effects on the load capacity of a hydraulic cylinder

Analytical and experimental investigations of typical hydraulic cylinders have indicated that their load capacities are significantly different from those obtained from simple buckling analysis of idealized systems. In any case, an increase in the friction coefficient at the restrained ends changes the actuator's limit load, while an increase in the initial maximum deflection (initial misalignment) decreases the limit load. A common practice of most cylinder manufacturers is to use a safety factor (between 2.5 and 4) to determine the service load after the critical load (buckling) is obtained by simple analytical procedures treating the cylinder as a perfect stepped column. The intricate aspects of friction effects have been deliberately left aside in this present work. Nevertheless, friction and interaction between mechanism and actuator in the buckling characteristics will be presented in the ongoing paper, which will follow this work. Authors know that, in a real system, the cylinder tube-rod interface is not rigid. Due to the flexibility of guide rings and clearances between components, misalignment (an angular deflection which increases with increasing axial load) exits at the interface. When initial imperfection angle exists, there is no sudden buckling. Then, stresses and deflections increase with increasing load. After repetitive use, the tolerance between the parts will become larger, consequently increasing the initial deflection, which has been proved to considerably decrease the load capacities of the power cylinders. From this analysis, a theoretical and experimental work has been carried out in order to show the advantages and disadvantages of the current design methods, characterizing the critical factors that cause the collapse and proposing useful design criterions. The present work aims to describe the behaviour of actuators under load capacity with experimental validation.     

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。     

Development of synchronized control system through a pneumatic parallel mechanism and its 3D CG model

This study developed a rehabilitation system that can improve the patient care services provided by physical therapists. Wristparalyzed patients were given arbitrary force through a six-Degree of freedom (6DoF) parallel mechanism composed of six pneumatic cylinders, and recovery training was performed. Each pneumatic cylinder was used to apply force control using a pulse width modulation control, and the force of the 6DoF direction was directed to the wrist of the patient. The thrust force of each cylinder and the force of the 6DoF direction of the parallel mechanism were analyzed. The analysis results conformed well to the experimental results. The developed rehabilitation system was designed to help a physical therapist remotely treat multiple patients at the same time. To monitor the operation of the parallel mechanism of each patient’s side, a 3D computer graphic model was created through OpenGL. The movement of this model was investigated to further examine the movement of the 6DoF direction of the parallel mechanism. Results confirmed that both movements can be controlled synchronously.     

重型多轴车辆互连油气悬架特性分析

以重型多轴车辆互连悬架系统为研究对象,建立了四轴互连油气悬架液压系统数学模型。模型中考虑了管路沿程压力损失、局部压力损失和油缸活塞杆运动摩擦力的影响,并进行仿真分析,通过台架试验验证了模型的正确性。基于互连油气悬架液压系统数学模型,对比分析了垂向和侧倾工况下互连悬架和独立悬架的刚度和阻尼特性,以及对互连悬架阻尼特性进行参数化分析。结果表明：在垂向工况下,互连悬架蓄能器内气体体积变化量相当于各活塞杆进出油缸的体积,与独立悬架蓄能器内气体体积变化量相等,因此互连悬架与独立悬架刚度特性相同,但其阻尼力大于独立悬架;侧倾工况下,互连悬架在增加侧倾刚度的同时也明显增大了阻尼力。两种工况下,独立悬架阻尼特性不变,互连悬架阻尼力随单向阀直径增大、阻尼阀直径增大、油管直径增大、油缸内径减小和活塞杆直径增大而减小。