Fault Detection and Diagnosis of Pneumatic Control Valve Based on a Hybrid Deep Learning Model

As the growing requirements for the stability and safety of process industries,the fault detection and diagnosis of pneumatic control valves have crucial practical significance.Many of the approaches were presented in the literature to diagnose faults through the comparison of residual sequences with thresholds.In this study,a novel hybrid neural network model has been developed to address the issue of pneumatic control valve fault diagnosis.First,the feature extractor automatically extracts in-depth features of the signals through multi-scale convolutional neural networks with different kernel sizes,which not only adequately explores the local distinguishable features,but also takes into account the global features.The extracted features are then fused by the feature fusion layer to reduce redundant features.Finally,the long short-term memory for fault identification and the dense layer for fault classification.Experimental results demonstrate that the average test accuracy is above 94%and 16 out of the 19 conditions can be successfully detected in the simulated actual industrial environment.The effectiveness and practicability of the proposed method have been verified through a comparative analysis with existing intelligent fault diagnosis methods,and the results suggest that the developed model has better robustness.

PILOT LEAKAGE'S INFLUENCES ON THE PERFORMANCES OF EXTRA HIGH PRESSURE PROPORTIONAL PNEUMATIC VALVE

A mathematic model is built up to analyze the influences of a pilot valve'sleakage on the performances of pneumatic pressure proportional valve, and the performances aresimulated by using MATLAB. The results indicate that using slide pilot valve in the valve system isfeasible, but the leakage's influences can not be neglected, especially it may induce instability ina low output pressure situation. A pilot valve using too large throttle window will cause the valveoscillate. To improve the working condition of pilot valve, a method adopting different widths oftwo throttle window is proposed. According to our simulation, this method balances the pressure dropbetween the two stage throttle ports, and reduces the influences of pilot valve's leakage.

Pneumatic resistance network analysis and dimension optimization of high pressure electronic pneumatic pressure reducing valve

The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.

Development of an ε-type actuator for enhancing high-speed electro-pneumatic ejector valve performance

A novel ε-type solenoid actuator is proposed to improve the dynamic response of electro-pneumatic ejector valves by reducing moving mass weight. A finite element analysis (FEA) model has been developed to describe the static and dynamic operations of the valves. Compared with a conventional E-type actuator, the proposed ε-type actuator reduced the moving mass weight by almost 65% without significant loss of solenoid force, and reduced the response time (RT) typically by 20%. Prototype valves were designed and fabricated based on the proposed ε-type actuator model. An experimental setup was also established to investigate the dynamic characteristics of valves. The experimental results of the dynamics of valves agreed well with simulations, indicating the validity of the FEA model.

Investigation of Semi-Active Hydro-Pneumatic Suspension for a Heavy Vehicle Based on Electro-Hydraulic Proportional Valve

Hydro-pneumatic suspension is widely used in heavy vehicles due to its nonlinear characteristics of stiffness and damping. However, the conventional passive hydro-pneumatic suspension can’t adjust parameters according to the complicated road environment of heavy vehicles to fulfill the requirements of the vehicle ride comfort. In this paper, a semi-active hydro-pneumatic suspension system based on the electro-hydraulic proportional valve control is proposed, and fuzzy control is used as the control strategy to adjust the?damping force of the semi-active hydro-pneumatic suspension. A 1/4?semi-active hydro-pneumatic suspension model is established, which is co-simulated with AMESim and MATLAB/Simulink. The co-simulation results show that the semi-active hydro-pneumatic suspension system can significantly reduce vibration of the vehicle body, and improve the suspension performance comparing with passive hydro-pneumatic suspension.

Lumped Parameter Mass Flow Rate and Pressure Control Characteristics Model for High-Speed Pneumatic PWM on/off Valve

Aiming at solving the problem of strong coupling characteristic of the key parameters of high-speed pneumatic pulse width modulation( PWM) on / off valve, a general lumped parameter mathematical model based on the valves time periods was well developed. With this model,the mass flow rate and dynamic pressure characteristics of constant volumes controlled by high-speed pneumatic PWM on /off valves was well described. A variable flow rate coefficient model was proposed to substitute for the constant one used in most of the prior works to investigate PWM on /off valves' dynamical pressure response, and a formula for disclosing the inherent relationship among the PWM command signal,static mass flow rate,and sonic conductance of the valve was newly derived.Finally,an extensive set of analytical experimental comparisons were implemented to verify the validity of the proposed mathematica model. With the proposed model, PWM on /off valves' characteristics,such as mass flow rate,step pressure response of the valve control system,mean pressure and ripple amplitude,not only in the linear range,but also in the nonlinear range can be wel predicted; Good agreement between measured and calculated results was obtained,which proved that the model is helpful for designing a control strategy in a closed loop control system.

Study on Outboard Inductive Damping Valve in Hydro-pneumatic Suspension

A new outboard inductive damping valve without any electronic control system is developed. Its working principle,structure and external characteristic are studied. Its mathematical model is presented and its damping characteristic is investigated on the basis of fluid continuity equation,differential equations of motion and Bernoulli equation. The influence of the valve parameters on the damping characteristic is studied numerically. The effects of outboard inductive damping valve and common damping valve on ride and tire load are compared also. The external characteristic of the valve is verified in bench test. The results show that the valve’s mathematical model is quite accurate and the developed valve can be adjust in two stages,which can also meet the requirements of the dynamic characteristic of the vehicle suspension system.

Design and Dynamic Model of a Frog-inspired Swimming Robot Powered by Pneumatic Muscles

Pneumatic muscles with similar characteristics to biological muscles have been widely used in robots, and thus are promising drivers for frog inspired robots. How- ever, the application and nonlinearity of the pneumatic system limit the advance. On the basis of the swimming mechanism of the frog, a frog-inspired robot based on pneumatic muscles is developed. To realize the indepen- dent tasks by the robot, a pneumatic system with internal chambers, micro air pump, and valves is implemented. The micro pump is used to maintain the pressure difference between the source and exhaust chambers. The pneumatic muscles are controlled by high-speed switch valves which can reduce the robot cost, volume, and mass. A dynamic model of the pneumatic system is established for the sim- ulation to estimate the system, including the chamber, muscle, and pneumatic circuit models. The robot design is verified by the robot swimming experiments and the dynamic model is verified through the experiments and simulations of the pneumatic system. The simulation results are compared to analyze the functions of the source pressure, internal volume of the muscle, and circuit flow rate which is proved the main factor that limits the response of muscle pressure. The proposed research provides the application of the pneumatic muscles in the frog inspired robot and the pneumatic model to study muscle controller.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Novel miniature pneumatic pressure regulator for hopping robots

A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles, wails and dit- ches. The regulator helps the hopping robot to decrease size and weight, and to sustain high pres- sure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pres- sure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.

A rotary pneumatic actuator for the actuation of the exoskeleton knee joint

Rotary pneumatic actuators that are made out of linear one are always best suited for exoskeleton joint actuation due to its inherent power to weight ratio. This work is a modified version of knee actuation system that has already been developed and major modifications are made in order to make it more suitable for human wearing and also to reduce its bulkiness and complexity. The considered actuator system is a rotary actuator where a pulley converts the linear motion of the standard pneumatic piston into the rotary motion. To prove the capability of the actuator, its performance characteristics such as torque and power produced are compared to the required torque and power at the knee joint of the exoskeleton in swing phase and are found to be excellent. The two-way analysis of variance（ANOVA）is performed to find the effect of the throat area valve on knee angle. The ANOVA shows the significant effect of the throat area variation on the knee angle flexion made by the proposed actuator. A relationship between the throat area of flow control valve, that is connected to the exit port of the direction control valve, and angular displacement of the knee joint has been formulated. This relationship can be used to design a control system to regulate the mass flow rate of air at the exit and hence the angular velocity of the knee joint can be controlled.

Error Analysis on the Positioning Accuracy of a Pneumatic Vibration Isolator

A method of error analysis on the positioning accuracy of a pneumatic vibration isolator was proposed.First,the necessity of positioning accuracy was studied,in addition to the key factors associated with positioning accuracy.These analyses indicated that the positioning accuracy of the pneumatic vibration isolator was mainly attributed to the position error of the push button and the gap between the spindle and valve stem.Second,the error model of the positioning accuracy of the pneumatic vibration isolator was established through geometric simplification and geometric calculation.There are different methods used to calculate the position error of the push button for the different valves.Finally,an example analysis evaluating the impact of a specific two-position three-way valve on the positioning accuracy was given by means of error distribution.Experimental results validated the accuracy of the error model and the example analysis.This error model can be used to guide the structural parameter optimization design according to the requirements for positioning accuracy.

Concentric Annular Clearance-Controllable Pressure Characteristics Research of a High Pressure Pneumatic Pressure Assembly

High pressure is an important development orientation in pneumatic field,since it can not only improve dynamic characteristics of pneumatic system but also decrease the size of components and mounting space.Due to the advantages of high energy density and high instant expansibility,high pressure gas has been widely used in many applications.However,systematic researches are lacked especially in pressure characteristics which are very important in pneumatic system at present.In a high pressure pneumatic system,the pressure of a fixed cavity with annular clearance needs to be controlled within a wide range,so a single stage proportional slide valve is proposed to satisfy the requirements of high pressure and low flow rate.First,working principle and structure of the pressure assembly and the slide valve are introduced.Then mathematical model of the high pressure pneumatic system is built up;controllable pressure range is simulated,and influence of uncertain factors,such as fit clearance of the pressure valve and the cavity on controllable pressure,is discussed.Finally,a test bench of the pressure assembly is built up,and the controllable pressure and step response experiments are carried out.Both simulation and experimental results show that the designed slide valve can satisfy the requirements well.The proposed clearance presumption method based on simulation and experimental results is valuable for indirect measurement of processing tolerance.

全自动气控座椅加载试验机的设计

根据目前中小企业对座椅载荷进行疲劳试验与检测的实际需求以及目前试验机的发展情况,发现了市面常见的座椅载荷试验机存在前期投资大、机构复杂及维护保养需求高等问题,在中小型座椅生产企业中推广和使用受限。基于此,从中小企业实际需求出发,本着结构简单、投资经济、便于使用的原则,提出一种全自动气控座椅载荷疲劳试验机,设计控制机构完全采用压缩空气作为驱动源,其来源方便、环保节能。在对当前座椅加载试验机特点及需求研读与分析的基础上,提出了全自动气控加载试验机的总体设计思路;根据对座椅加载控制的要求与结构模式,形成气动控制系统的总体架构及控制原理与控制方法设计;对座椅加载疲劳试验机进行了实验室模拟实验测试。结果表明,此控制系统设计方案能够实现座椅载荷负载大小变化模拟,可以实现座椅加载模拟工作节拍控制以及座椅加载时长控制调节,且完全脱离供电需求,经济环保,为生产企业后期使用维护提供了极大的方便。

高压气动装置弹射性能分析及优化

根据高压气动弹射装置的工作原理和特点,结合实际应用给出了无缓冲腔、采用缓冲腔、采用多组高速开关阀等3种弹射装置方案,基于气体动力学理论,采用分段建模的方式,构建了内弹道方程组,计算分析了弹射装置主要参数对弹射体出筒速度、弹射过程最大瞬时过载等的影响。仿真结果表明,采用缓冲腔、采用多组高速开关阀2种方案的弹射装置均可有效降低弹射体的最大瞬时过载、提高出筒速度,且采用多组高速开关阀的效果最好。研究结果可为高压气动弹射装置的优化设计、制造与试验,提供借签。

智能气动阀门定位系统动态特性研究

针对智能气动阀门定位系统数字孪生体的实现,提出一种可精确模拟气动继动器和执行器气室动作机理及气体动态特性的数学模型。在无需气体质量流量计的情况下,通过理论推导及实验在气动继动器动力学模型和等效质量流量模型中可变直径的节流孔板直径之间建立函数关系,对执行器气室多变过程建模,实现定位系统数字孪生体。数字孪生体实际运行测试以及模型仿真和实验对比验证了系统的可靠性。

CCPP加压站系统优化

分析了CCPP加压站存在的问题,制定了CCPP加压系统的优化方案。阐述了优化措施实施过程,并对于优化后试运行中出现的问题加以解决。实现了提升CCPP发电机组的发电效率,保障了CCPP加压站的稳定运行。

气动快关球阀的故障分析与处理

气动快关球阀是流体输送系统中安全可靠运行的关键装置,但是在气动阀门的使用过程中,在各种因素的影响下会发生故障,一旦气动阀门出现故障,将影响整个液体输送的稳定性及压力和流量调节的实时性等,相比传统手动阀门控制,气动快关球阀具有控制简单、可靠性高、响应迅速等优点。本文针对航天液体火箭发动机试验台液体长输管线上的实际案例,基于气动快关球阀的结构及特点分析,对实际应用中的球阀阀座PTFE阀座圈被异常切断,进入输送管道中的过滤器中的问题进行确定和分析,提出具体的解决措施,经过验证和改进后的气动快关球阀满足试验使用要求。

线控制动液压电磁阀气压检测动态性能分析

针对线控制动液压电磁阀测试中使用制动液会产生难以清洁、腐蚀性强等问题,采用压缩空气作为检测介质进行气检可有效地解决这一问题。此时,电磁阀液检和气检动态响应时间合格限之间的关系成为研究重点。因此,根据电磁阀的结构参数,利用ANSYS软件对电磁阀流场进行分析,计算获得流体力参数。然后,利用MATLAB/Simulink软件构建电磁阀仿真模型,从而获得电磁阀液检响应时间与气检响应时间之间关系式。最后,设计电磁阀液压测试系统和气压测试系统,对液检和气检动态响应时间合格限进行测试。结果显示:当电磁阀液检合格限为3.50 ms时,测试得到气检合格限实际值为3.33 ms,计算得到其理论值为3.125 ms,相对误差6.16%,验证了模型的准确性,对电磁阀气代液检测研究具有指导意义。

气动夹具系统改进设计

某机加工企业因业务发展需要新接收一批零件,但该企业现有气动机床夹具设备不能胜任其定位及加工精度要求,在不增加过多成本的基础上,对现有气动夹具系统改进设计做详细论述,并给出各设计环节的气动系统图、设计说明及设计完成后的气动夹具总图。将设计完成后的夹具系统在Automation Studio 7.0 Professional软件中建模并仿真,分析各缸线性位置-时间关系;各缸起步伸出时在0~50 mm范围内3个缸同步,有效提高了设备的生产效率。在51~250 mm长度范围内夹紧缸运动速度开始降低,实现定位缸先定位。退出时由于夹紧缸垂直布置原因,在250~233.69 mm范围内出现微小波动,其波动范围在16.3 mm;由于此段为各缸退出段,对零件加工精度无影响。正常工作后各缸运行平稳,波动现象消失,满足加工要求。最后将改进后的气动系统和原系统作对比分析,结果表明:改进设计后的气动系统不仅能够完全胜任新零件的加工精度要求,且有效避免了原设备故障率高、维护保养困难、设备成本高、噪声大的诸多不足。