Jet Pipe Servo Valve Research Articles

Modeling of a Jet Pipe Servovalve Considering Nonlinear Flow Forces Acting on the Spool

The design and analysis of jet pipe servovalves are mostly based on linear models. However, there are some nonlinear factors in this kind of electromechanical–hydraulic structure. The article deduces a linear rotation equation for the armature assembly and a linear flow equation for the control cavity. With the consideration of nonlinear hydraulic reaction forces in the second stage, the nonlinear dynamic equation of the main spool in an ideal jet pipe servovalve is derived. Based on the MATLAB (R2016a) software, the nonlinear model of a certain type of jet pipe servovalve is numerically investigated. The equilibrium points of the nonlinear system are calculated, the phase portraits are plotted, and the Hopf bifurcations caused by the flow-pressure coefficient as the control parameter and the period-doubling bifurcations caused by the variation of the input signal are analyzed. The vibration frequency of the time-domain response of the fifth-order system with a cosine signal as input is 242 Hz, which is similar to the experimental value of 233 Hz. The relative error between the two is 3.9%, verifying the validity of the nonlinear system model.

Experimental and simulation research of performance degradation of jet pipe servo valve under wedge erosion of jet amplifier

Due to the erosion of solid particles in contaminated oil, the material of the wedge of the jet amplifier falls off, and the wedge structure deforms, which inevitably leads to irreversible performance degradation and even failure of the jet pipe servo valve (JPSV). In this study, the experimental analysis of the performance of the JPSV before and after wedge erosion is carried out. According to the physical object of wedge erosion, the three-dimensional model of the jet amplifier after wedge erosion is reconstructed. Based on computational fluid dynamics (CFD) simulation, the comparison results of the flow field of the jet amplifier before and after wedge erosion are analyzed to explain the performance degradation of the JPSV. Furthermore, the relationship between the erosion degree of the wedge and the performance deterioration of the JPSV is investigated. The experimental and simulation results indicate that the dynamic behavior of the JPSV will gradually degrade with the increase of the erosion degree of the wedge, and the degradation process is nonlinear. Additionally, through CFD simulation, it is revealed that the critical factor causing the dynamic performance deterioration of the JPSV is that after wedge erosion, the shunting effect of the wedge is weakened, and the flow field of the jet amplifier changes significantly. This paper provides a new reference and practical method for studying and predicting the performance degradation of the JPSV caused by wedge erosion.

The investigation of a unbalanced barrel pitching system’s characteristics degradation and compensation under gradual erosion behavior

The unbalanced barrel pitching system is a typical electro-hydraulic coupling servo control system, the performance of which determines the response speed and hit probability of vehicle mounted weapon equipment. However, in the actual service process, its core component, the high precision jet pipe servo valve, will produce the gradual erosion of the pilot stage’s receivers and the power stage’s throttling edges, which will induce the performance degradation of the unbalanced barrel pitching system, and finally greatly reduce the performance of barrel weapons. Therefore, a pressure and position double loop state space model of unbalanced barrel pitching system including the core parameters of performance degradation is established. The erosion behavior mechanism model of jet pipe servo valve is constructed, and the performance degradation characteristics of the unbalanced barrel pitching control system under the condition of erosion are further analyzed. Finally, aiming at the double loop structure of internal pressure loop and external position loop, the RBF Network Adaptive Robust Sliding Mode-Proportional Integral Derivative two-stage controller of barrel system is designed, based on which the experimental platform of unbalanced barrel pitching control is built. The experimental results are in good agreement with the theoretical results, so the proposed control method can effectively suppress the degradation of internal structural parameters induced by erosion, that is, it can better compensate the performance degradation of barrel pitching system induced by gradual erosion behavior.

Research on Pressure-Flow Characteristics of Pilot Stage in Jet Pipe Servo-Valve

Jet pipe servo-valves are widely used in high-precision servo control systems. However, the accuracy of pressure-flow characteristic equations relevant to its pilot stage needs to be improved. In contrast to the traditional analytical approach using the orifice equation, the article investigates the pressure and flow characteristics of the pilot stage based on the impact jet principle. Taking the pre-stage of a certain type of jet pipe servo-valve as an example, the flow field is simulated using ANASYS software. By comparing the simulation data with the calculation results, the pressure characteristic model is basically consistent with the simulation data, and the relative error is less than 2.3%. The error between the revised flow characteristic model and the simulation result is small, and the maximum deviation is less than 0.0022 L/min. Finally, to verify the applicability of the model to other specifications, the experimental data in the literature are compared with the theoretical calculation results, the maximum relative error of pressure characteristics is 2.19%, and the relative error of flow characteristics is less than 5.34%.

Mathematical Modelling and Hierarchical Encourage Particle Swarm Optimization Genetic Algorithm for Jet Pipe Servo Valve.

The jet pipe servo (JPS) valve is one key component, whose dynamic performance directly influences the aircraft's maneuverability. In this paper, a more accurate mathematical model and a novel multiobjective hierarchical encourage particle swarm optimization genetic algorithm (HEPGA) are proposed to improve the dynamic performance of the jet pipe servo valve. By optimizing the main structure parameters of the jet pipe servo valve, the adjustment and overshoot in the dynamic performance are reduced by 24.28% and 51.39%, respectively, compared with the prototype before optimization. To obtain a more accurate mathematical model, the computational fluid dynamics (CFD) is introduced to modify the analytical model considering the turbulent submerged free jet. Different from conventional numerical simulation, the dynamic mesh technique is used to analyze the flow field distribution by considering the force interaction of various parts of the jet pipe servo valve under actual working condition. Then, the HEPGA with better convergence is utilized because of the conflict of adjustment and overshoot. This proposed hybrid algorithm introduces the concept of staff welfare system to divide the population into elite individuals and excellent individuals of particle swarm optimization and general individuals of genetic algorithm. Meanwhile, the convergency performance of the HEPGA is evaluated through the Rosenbrock function by comparing with other particle swarm genetic hybrid methods. Subsequently, the experimental platform is constructed and the dynamic performance tests are conducted on the prototype after optimization. The experimental results verify the accuracy of the established mathematical model and the significant improvement of dynamic performance of the jet pipe servo valve.

Analysis and optimization of the pilot stage of jet pipe servo valve

Based on the principle of two-phase hydrodynamics and the mechanism of cavitation generation, this paper uses the finite volume method (FVM) in computational fluid dynamics (CFD) to analyse the features of fluid flow in jet amplifier, i.e., the pilot stage of jet pipe servo valve, and designs a lab bench to experimentally prove the accuracy of this numerical method. On this basis, the author discussed how four structural parameters influence the amplification efficiency of the jet amplifier. The amplification efficiency of the jet pipe servo valve can be maximized by setting the distance between nozzle and receiving holes of 0.1 mm, the diameter of receiving holes of 0.2 mm, the inclination angle of 22.5°, and the spacing between the two receiving holes of 0 mm (if possible). The research methods and results provide a solid basis for the design and performance prediction of the jet pipe servo valve.

Research on Driving System of Hydraulic Robot Based on Ferrofluid

In the driving system of hydraulic robot, the mechanical components are large and complex due to some factors such as material performance and structural design. Based on the magnetorheological properties of ferrofluid, a novel hydraulic driver method is presented based on the principle of jet pipe servo valve. Adding a magnetic field in the air field of the valve body directly controls the deflection and offset of the ferrofluid, and realizes the directly control from the electric/magnetic to fluid. The mathematical model of ferrofluid flows in the air field under magnetic field is established based on the ferrohydrodynamics(FHD).The experimental results show that the millimeter-level deflection has met the actual engineering needs of the hydraulic driving system.

Performance reliability of jet pipe servo valve under random vibration environment

Jet pipe servo valve is a key hydraulic control component in aerospace. Work environment usually brings random vibration to jet pipe servo valve affecting its reliability. In order to explore conditions for high reliability, a dynamic model is developed to describe the performance indexes of jet pipe servo valve under random vibration environment. Null shift is the main performance index to evaluate the performance of jet pipe servo valve under random vibration environment. Because of the implicit expression of null shift, response surface method (RSM) is introduced to develop the null shift in a quadratic polynomial with no cross term type of design parameters. Monte Carlo method is proposed to calculate the reliability considering the mean and standard deviation of parameters. Dimensionless mean and standard-deviation reliability sensitivities are researched and importance ranking shows the most key parameters. Reliability and reliability sensitivity varied with most key parameters are extended and reasonable parameters are recommended on the premise of high reliability and low reliability sensitivity.

High Torque Density Torque Motor With Hybrid Magnetization Pole Arrays for Jet Pipe Servo Valve

Torque motor is one key component that directly influences the dynamic performance of jet pipe servo valve in aircraft. In this paper, a novel torque motor with hybrid-magnetization pole arrays is proposed. By changing the magnetization patterns of permanent magnets, the torque motor can significantly improve the output torque by range of 47–52% compared with traditional designs, while maintaining the system size and mass. The design concept and operating principle of the torque motor is presented. The magnetic field distribution is formulated analytically with equivalent magnetic circuit. Different from conventional study, the flux leakage of the permanent magnets and coils is included to improve the model precision. Subsequently, the output torque is derived mathematically from the airgap flux. Following that, the numerical calculation is conducted to validate the mathematical models of magnetic field and output torque. The design optimization is then carried out. One research prototype that can be mounted with either conventional magnet or the proposed hybrid array has been developed. The test rigs are constructed and experiments are conducted on the prototype. Both numerical computation and experimental results verify the significant improvement of torque generation of the proposed hybrid magnetization torque motor.

Effect of key structures and parameters on dynamic characteristics of three-stage jet-pipe servo valve

The traditional two-stage electro-hydraulic servo valve cannot meet the needs of production equipment with large flow rate and wide frequency bandwidth. The structure and working principle of the three-stage jet-pipe electro-hydraulic servo valve are described. As the structure of the three-stage valve is complex and many factors influence dynamic characteristics, the main objective of this study is to establish a mathematical model and investigate those factors. In order to advance the local phase, a proportional–derivative correction link is added to the closed-loop transfer function of the three-stage valve. By simulations, the step response curve and open-loop Bode curve are obtained for analysis in the frequency domain and the time domain. The influences of main factors such as flow gain, pressure gain, main spool area, and feedback-rod rigidity on the dynamic response of the valve are analyzed in the time domain. A three-dimensional model of the armature–feedback-rod component is established and is simulated using the Workbench finite-element analysis software. The influences of various structural parameters are analyzed, especially those of the rod area, section shape, length, and material on the feedback rod rigidity.

Snapshot POD analysis of transient flow in the pilot stage of a jet pipe servo valve

ABSTRACTThe spatial evolution of a turbulent flow in the pilot stage of a jet pipe servo valve at the inlet pressure and deflection angle of the jet pipe is investigated using a large eddy simulation (LES). The pressure of the same flow field is measured by a high frequency dynamic pressure sensor in the experiments and is compared with the results of the LES, as well as their root-mean-square (RMS) and fast Fourier transform (FFT) results. The results of experiments and LES are in good agreement, indicating that LES is able to predict the flow dynamics. Velocity datasets based on LES are utilised to conduct the snapshot proper orthogonal decomposition (snapshot POD) technique. The snapshot POD analysis results of the first 4 modes show a full ability to directly visualise details of the coherent structures. The influences of the inlet pressure and deflection angle of the jet pipe are also discussed. Under different inlet pressures, the velocity eigenfunctions of the first mode are similar, while the locations and strengths of the vortices in high modes are different. The Lamb-Oseen vortices that affect the trajectory of jet streams are observed in the vicinity of the entrances of receiver channels only in the first mode, and several spindly vortices appear in the region of −5 < y/n < −2 in the higher modes and act in opposite directions between adjacent vortices. The flow becomes more turbulent with increasing inlet pressure, and the turbulent structures of the high modes become ineffective from a deflection angle of 0.4° onward.

Flow measurement for the pre-stage of jet pipe servo valve using 2D -PIV technique

In order to investigate the internal flow field characteristic for the pre-stage of jet pipe servo valve, a large-scale low-speed flow field visualisation experimental platform was developed. The i...

Reliability modeling for dependent competing failure processes with mutually dependent degradation process and shock process

Many systems experience dependent competing failure processes resulting from simultaneous exposure to degradation processes and random shocks. Moreover, the degradation process and shock process may be mutually dependent. On the one hand, shocks can cause sudden degradation increments, which accelerate degradation process. On the other hand, the occurrence intensity of shock process will increase with the accumulation of degradation. Due to the mutual dependence between degradation and random shocks, the arrival shocks can cause abrupt degradation and then facilitate the occurrence of random shocks recursively. Therefore, the intensity is dependent on the number of arrival shocks, and the shock process cannot be described by the Poisson process used in previous studies. In this paper, a Facilitation model, which is a special type of Markov point process, is introduced to model the shock process. Furthermore, based on the Facilitation model, a novel analytical reliability model with the mutual dependence is developed. A case of a jet pipe servo valve is presented to demonstrate the developed model. The result showed that the reliability declines significantly when considering the mutual dependence.

Mathematical modeling and linearized analysis of the jet-pipe hydraulic amplifier applied to a servovalve

The accurate mathematical model of the jet-pipe hydraulic amplifier, which is the pilot control stage of a jet-pipe servovalve, is very necessary to analyze and control the performance of a jet-pipe servovalve. In this paper, based on the hydraulic bridge’s flow balance equations, an improved nonlinear explicit model with the absorption effect is developed. The linearized model and valve coefficients are derived from the nonlinear improve model. To test and verify the improved models, the pressure and flow characteristic model of jet-pipe hydraulic amplifier are verified by the experiment. The results show that the model is approximate to the experimental data. In addition, the influence of structural parameters on performance of jet-pipe hydraulic amplifier is analyzed by simulation.

Comparison of jet pipe servo valve with flapper nozzle servo valve

&#x0D; &#x0D; &#x0D; Electro-hydraulic servo valves (EHSVs) serve as an interface between electrical devices and hydraulic systems. They are capable of converting low power electrical input into movement of a spool to control precisely high power, low speed hydraulic actuators. Nowadays, jet pipe electro-hydraulic servo valve and flapper nozzle electro-hydraulic servo valve are typical two-stage control flow servo valve and are the most popular in use. This paper recommends and compares characteristics, working principle and structure for two kinds of servo valve. Besides, the simulation was carried out in a commercially software of Ansys, hence some features of jet pipe servo valve such as outstanding advantages of working feature or reliability are analysed. &#x0D; &#x0D; &#x0D;

Parameter identification of a jet pipe electro-pneumatic servo actuator

AbstractThis paper presents experimental parameter identification of a jet pipe electro-pneumatic servo actuator model, which represents a class of high performance fast actuation systems. Parameter identification is given including detailed representation of linear dynamics, hysteresis, and the mass flow rate characteristics of the jet pipe servo valve, besides the static friction model of the linear pneumatic cylinder. Model parameters are identified and the model formulation is validated through simulation and experimentation. The main contribution of this work is threefold. Firstly, the mass flow rate characteristics are identified using the pressure dynamic equation in one cylinder chamber without the use of a flow sensor. Secondly, a lag behaviour related to the non-modelled dynamics is found out by performing an experimental identification of the frequency response of the servo valve. Thirdly, a new experimental setup is presented to give the static friction model as a function of not only the rela...

Research on Dynamic Reliability of a Jet Pipe Servo Valve Based on Generalized Stochastic Petri Nets

The jet pipe servo valve is widely used in the military fields of aviation and ship, whose reliability has obvious randomness and dynamic. However, existing methods are either having complicated theory or analyzing static reliability. Based on the generalized stochastic petri nets (GSPN) theory and the collected basic failure modes and failure rate data of jet pipe servo valve, this paper proposes a novel modeling and simulating method for system’s dynamic behavior analysis. In this method, the dynamic reliability model considering failure’s random and repair is established and is simulated using GSPN software. Then, the steady state probability of servo valve is calculated, which is compared with the value calculated by Markov method. Finally, the dynamic reliability parameters of jet pipe servo valve are calculated using collected failure rate data and different repair rate data. Results show the probability that the maximum error between methods of GSPN and Markov is 2.07%, the optimal repair rate set is less than 1.71µi, and also the dynamic reliability parameters become better with increasing simulation time because of failure’s recovery. Therefore, research methods and results based on GSPN are concise and realistic, which can be used for failure’s qualitative forecast and dynamic reliability’s quantitative calculation of similar complicated system.

Modeling and Simulation of Jetpipe Servovalve Torque Motor

The torque motor is a precision mechatronic component used to convert low electric signal into linear mechanical displacement of the Jetpipe. Such torque motors are categorized under multi disciplinary engineering systems, which are complex in nature and also induces challenges to integrate with hydraulic system. This paper applies model-based system design approach of jetpipe servovalve torque motor to study the effect of critical parameters like armature length and air gap, feedback spring stiffness, and flexure tube stiffness on the dynamic performance of the were studied.

Modeling for finding armature assembly moment of inertia in jet pipe servo valve torque motor

Modeling for finding armature assembly moment of inertia in jet pipe servo valve torque motor

Characteristics Analysis of Giant Magnetostrictive Actuator Applied in Jet-Pipe Servovalve

In order to improve the performance of jet-pipe servovalve, a novel pilot stage for jet-pipe servovalve driven by giant magnetostrictive actuator is presented, and its working principle is given. On the basis of Jiles-Atherton’s theory of magnetism, the dynamic nonlinear model of giant magnetostrictive actuator is deduced to analyze the characteristics. The simulation results shows the peak time of GMA is less than 0.5ms at the driving current of 1.5A, and the bandwidth can be reached up to 900Hz, but the static performance is worse than the torque motor applied in conventional jet-pipe servovalve.