High Speed On-off Valve Research Articles

Multi-objective optimization of high-speed on-off valve based on surrogate model for water hydraulic manipulators

Water hydraulic manipulators are suitable for remote handling maintenance task in reactors. Water hydraulic servo valves are currently used in the manipulators, but water has the characteristics of low viscosity and poor lubricity, there are inevitable leakage and wear failure. High speed on-off valve (HSV) can be used to generate proportional output and could be used to replace servo valves. In this research, a water hydraulic HSV for water hydraulic manipulators is proposed. An optimization method supported surrogate model, non-dominated sorting genetic algorithm II (NSGA-II), and AMESim simulation is built. And the effect of the HSV structure parameters on dynamic characteristic is analyzed using the global sensitivity analysis. The Pareto frontier is investigated using decision-making tools with FUZZY, LINMAP, and TOPSIS methods, the best solutions are selected by using the deviation index. The HSV prototype is fabricated, and the static and dynamic characteristics experiments of the HSV are carried out. The simulation results showed that, after optimization, the opening response time is reduced by 17%, and the closing response time is reduced 9%. The experimental results show that the opening response time and closing response time reach 5.93 ms and 4.84 ms.

Analysis of Dynamic Characteristics and Power Losses of High Speed on/off Valve with Pre-Existing Control Algorithm

A high-speed on/off valve (HSV) is generally the core component of a digital hydraulic transmission system. Therefore, its dynamic characteristics often restrict the overall performance of the digital hydraulic system. Most of the current studies focus on the optimization on the dynamic characteristics or the energy characteristics, few studies have comprehensively considered the two characteristics of the valve together. In this paper, a pre-existing control algorithm (PECA) is proposed to improve the dynamic characteristics of the HSV, and simultaneously optimize the power losses of the HSV to improve its energy conversion efficiency. The results show that, compared with the traditional single-voltage driven strategy, the opening time of the PECA decreases by 29.4%, the closing time decreases by 59.6%, and the energy conversion rate increases by 7.9%.

Hydraulic cylinder position system controlled by piezoelectric high-speed on-off valve

Hydraulic cylinder position system controlled by piezoelectric high-speed on-off valve

Development of a novel two-stage proportional valve with a pilot digital flow distribution

Pilot two-stage proportional valves are widely used in high-power hydraulic systems. For the purpose of improving the dynamic performance, reliability, and digitization of the traditional proportional valve, a novel two-stage proportional valve with a pilot digital flow distribution is proposed from the viewpoint of the dual nozzle-flapper valve’s working principle. In particular, the dual nozzle-flapper is decoupled by two high-speed on/off valves (HSVs). First, the working principle and mathematical model of the proposed valve are determined. Then, the influences of the control parameters (duty cycle and switching frequency) and structural parameters (fixed orifice’s diameter and main valve’s spring) on the main valve’s motion are analyzed on the basis of theory, simulation, and experiment. In addition, in optimizing the value of the fixed orifice’s diameter, a new design criterion that considers the maximum pressure sensitivity, flow controllability, and flow linearization is proposed to improve the balance between the effective displacement and the displacement fluctuation of the main valve. The new scheme is verified by simulations and experiments. Experimental results of the closed-loop displacement tracking have demonstrated that the delay time of the main valve is always within 3.5 ms under different working conditions, and the tracking error can be significantly reduced using the higher switching frequency. The amplitude-frequency experiments indicate that a − 3 dB-frequency of the proposed valve can reach 9.5 Hz in the case of ±50% full scale and 15 Hz in the case of 0%–50% full scale. The values can be further improved by increasing the flow rate of the pilot HSV.

Modeling and Research of Fuzzy PID Control Strategy for Hydraulic Rock Drill Propulsion System

According to the coupling characteristic of propulsion system and impact system of hydraulic rock drill, deduced the calculation formula of optimal axial thrust for the propulsion system of hydraulic rock drill. On the basics of the calculation formula before, the paper constructed compound driven propulsion system of hydraulic rock drill based on electro-hydraulic proportional pressure-reducing valve and high speed on-off valve, and established its dynamics model. Finally, the paper considered optimal axial thrust as the goal, and adopted the fuzzy PID control strategy to realize on-line, intelligent control to axial thrust of the propulsion system of hydraulic rock drill. Through mathematical modelling and simulation study show that fuzzy PID control method has its advantages as the fast response follow by target, high control precision, and small fluctuation, and provided theory reference and technology method for intelligent control of the propulsion system of hydraulic rock drill.

Humanoid Lower Limb: Design, Analysis, Observer-Based Fuzzy Adaptive Control and Experiment

With flexibility similar to human muscles, pneumatic artificial muscles (PAMs) are widely used in bionic robots. They have a high power-mass ratio and are only affected by single-acting pneumatic pressure. Some robots are actuated by a pair of PAMs in the form of antagonistic muscles or joints through a parallel mechanism. The pneumatic pressure and length of PAMs should be measured simultaneously for feedback using a pressure transducer and draw-wire displacement sensor. The PAM designed by the FESTO (10 mm diameter) is too small to install a draw-wire displacement sensor coaxially and cannot measure muscle length change directly. To solve this problem, an angular transducer is adopted to measure joint angles as a whole. Then, the inertia of the lower limb is identified, and observer-based fuzzy adaptive control is introduced to combine with integrated control of the angular transducer. The parameters of the fuzzy control are optimized by the Gaussian basis neural network function, and an observer is developed to estimate the unmeasured angular accelerations. Finally, two experiments are conducted to confirm the effectiveness of the method. It is demonstrated that piriformis and musculi obturator internus act as agonistic muscle and antagonistic muscles alternatively, and iliopsoas is mainly responsible for strengthening because of the constant output force. Piriformis has a greater influence on yaw and roll angles, while musculi obturator internus is the one that influences the pitch angle the most. Due to joint friction, the dead zone of the high-speed on-off valve, lag of compressed air in the trachea, and coupling among angles are very difficult to realize precise trajectory tracking of the pitch, yaw, and roll angles simultaneously.

Analysis and Research on High Speed On-off Valve Electromagnets with Different Electromagnetic Drive Forms

Abstract As a typical hydraulic component of digital hydraulics, high speed on-off valves are widely used in vehicle braking and high-pressure common rail injectors. Different electromagnetic drive forms have different effects on the discontinuous drive control effect of digital hydraulics. In order to compare the effects of the two electromagnetic drive forms of moving-coil type (MCT) and moving-iron type (MIT) more pro-foundly, this paper conducts the two electromagnetic drive forms. Through comparative analysis, the superiority of MCT electromagnetic drive in response time is obtained. First, the principles of the two drive forms are explained separately, and the magnetic circuit analysis of the two electromagnetic drive forms is carried out. Then, assuming that the coil parameters are the same, the electromagnetic simulation software is used to measure the magnetic field and electromagnetic function parameters of the MIT and the MCT. Finally, through the analysis and comparison of electromagnetic force, inductance, current and other parameters, it was found that the response speed of the MCT drive was better than that of the MIT. The magnitude of the two forms of steady-state electromagnetic force depends on the position of the initial working air gap of MIT. This phenomenon is explained in terms of electrical time attempts and inductance. It provides ideas for the design and improvement of electromagnetic drive of high speed on-off valves.

Design and Verification of Linear High-speed On-off Valve

Design and Verification of Linear High-speed On-off Valve

Research on Electromagnetic Force Performance of High Speed on-off Valve

Taking a high speed on-off valve as an example, the effects of air gap, shell thickness, armature length, guide sleeve type and armature radius on the electromagnetic force performance are studied. The results show that the air gap is negatively related to the electromagnetic force, the shell thickness, armature length and armature radius are positively related to the electromagnetic force, and the effect of pure copper guide sleeve and non-guide sleeve on the electromagnetic force is basically the same. The electromagnetic force can be increased by the guide sleeve with magnetic separation ring. The influence order of parameters on electromagnetic force is: air gap > armature radius increment > armature length increment > shell thickness increment.

Study on Flow Characteristics and Linearization of Pneumatic High-Speed On-off Valve

It is hard to model the dynamic flow rate of pneumatic high-speed on-off valve due to its dead zone and nonlinearity. The average opening ratio was proposed to describe the dynamic flow rate after systematically analyzing the spool action characteristics. The mathematical relationship between flow rate, frequency, and duty cycle was established. Experimental results show that the method can accurately reflect the dynamic flow characteristics. Finally, a piecewise linearization method is designed to make the flow rate proportional to the input.

A power-by-wire aircraft brake system based on high-speed on-off valves

The aircraft brake system plays a recognized crucial role as a fundamental subsystem. Conventional aircraft brake actuators are powered by centralized hydraulic source, engine driven pump (EDP). The proper operation of aircraft braking requires many accessories, such as long, complex pipelines and pilot-operated servo valves, which are located near the landing gear and exposed to cold high-speed airflow and possible obstacles, where the environment is harsh to cause many problems such as vibration even leakage. To improve the safety and maintenance of aircraft, a novel concept of power-by-wire aircraft brake system (PWABS) is proposed in this paper. It only consumes electric power from the aircraft to implement the brake function instead of hydraulic fluid. Thus, the long, complex hydraulic pipelines are replaced by electric power cables, cutting the weight of aircraft utility systems; besides, the leaks of the pilot stage of servo valves are also reduced by replacing servo valves with on/off valves to save the power input from aircraft. Above all, that aircraft brake system can work as usual even when the airborne hydraulic source is lost, which benefits the aircraft safety considerably. This paper presents the working principle and the configuration of PWABS, and parameters of which are designed. Dynamics models of PWABS and aircraft taxiing are established. Based on specific models, a nonlinear adaptive backstepping (NAB) control strategy is introduced for the system control, simulations are carried out to verify the practicality, a prototype is developed, and experiments are conducted on an inertia brake test bench to investigate the performance. The present results demonstrate the feasibility of PWABS and provide a better choice for more-electric aircraft braking systems.

A novel architecture of electro-hydrostatic actuator with digital distribution

To address the flow imbalance rapidly of the asymmetric Electro-Hydrostatic Actuator (EHA), this paper presents a novel architecture of asymmetric EHA with the Digital Distribution (EHA-DD). It also improves the flow nonlinearity and control accuracy of the pump, especially in the low-speed condition. The digital distribution with two High-Speed on–off Valves (HSVs) not only balances flow instead of the check valves, but also replaces the pump at the low-speed to control output flow by adjusting the PWM signal. The pump and HSVs are the crucial components to control flow output. Firstly, the flow calculation models of the pump and the duty ratio inversed model of the HSV are obtained through experimental tests and the identification method. To get the control input signal for the required flow, the pump speed and PWM duty ratio for the HSVs are inversed to compensate for flow output. Further, a multimode digital flow distribution control method based on pump speed, mainly including the pump-controlled mode for large flow demand and valve-controlled mode for little flow demand, is proposed to control the accurate flow output actively. The step extension experiments based on the flow calculation models are conducted on the EHA-DD prototype under elastic, opposite varying load. The results demonstrate that the EHA-DD realizes little position error by accurate flow control, and it is also beneficial to improve the service life of the pump.

Structure optimization and flow field simulation of plate type high speed on-off valve

There is a relatively complex flow state inside the high speed on-off valve, which often produces low pressure area and oil reflux in the high-speed opening and closing process of the spool, causing cavitation and vortex and other phenomena. These phenomena will affect the stability of the internal flow field of the plate valve and the flow characteristics of the high speed on-off valve. Aiming at the problems of small flow rate and instability of internal flow field, a new spool structure was designed. The flow field models of two-hole and three-hole plate spools with different openings were established, and software Ansys Workbench was chosen to mesh the model. The standard k-e turbulence model was selected for numerical simulation using Fluent software. The pressure distribution and velocity distribution under the same pressure and different opening degree were obtained. The structure and parameters of the optimization model were also obtained. The stability analysis of flow field under different pressure was carried out. The results demonstrate that the three-hole spool has a similar flow field change with the two-hole spool, but it does not create a low pressure zone, and the three-hole spool can work stably at 2 MPa or less. This method improves the appearance of low pressure area and oil backflow in the process of high speed opening and closing of spool. The stability of flow field and the flow rate of high speed switch valve are improved. Finally, the products designed in this paper are compared with existing hydraulic valve products. The results show that the three-hole plate type high speed on-off valve designed in this paper maintains the stability of the internal flow field under the condition of 200 Hz and large opening degree, and realizes the increase of flow rate.

Investigation on adaptive pulse width modulation control for high speed on/off valve

High speed on/off valves (HSV) have often been used to control flow or pressure in digital hydraulic systems due to higher switching frequency. However, the dynamic performance and energy efficiency are highly affected by the supply pressure and the carrier frequency. In this paper, a new adaptive PWM control method for HSV based on software is proposed. The proposed adaptive PWM consists of a reference PWM, an excitation PWM, a high frequency PWM, and a reverse PWM. First, the nonlinear model of the HSV was established, and the structural composition and working principle of the proposed adaptive PWM control strategy were presented. Secondly, individual feedback controllers for the excitation PWM, the high frequency PWM, and the reverse PWM were designed, respectively; and each of the individual feedback controllers was experimentally verified. Finally, the comparative experimental results demonstrated that, with the proposed adaptive PWM control, the rising delay time of the control pressure drastically reduces by 84.6 % (from 13 ms to 2 ms), the duty cycle's effective range remains large (12 %-85 %) even with high carrier frequency (100 Hz), and the temperature rise of the valve's coil shell is reduced by 61.5 %, compared to the three-voltage control. In addition, the dynamic performance and the energy efficiency of the HSV are not affected by the supply pressures and carrier frequencies, which proves that the proposed control strategy can improve the robustness and stability of the valve system.

Dynamic Characteristics for the Voice Coil Motor Direct-driven High-speed On-off Valve

Dynamic Characteristics for the Voice Coil Motor Direct-driven High-speed On-off Valve

Adaptive Backstepping Control of Vacuum Servo System Using High-Speed on-off Valves

Using high-speed on-off valves (HSVs) with small size, low cost, and high switching accuracy instead of expensive proportional/servo valves, and researching high-performance vacuum servo system can further enhance the competitiveness of vacuum servo technology. However, due to the delay characteristics of high-speed on-off valve (HSV), the average gas mass flow rate of the output has dead zone, saturated zone and nonlinear zone. A linear compensation method for flow output is designed, so that the average gas mass flow rate of the output is approximately positively correlated with the duty cycle of the pulse width modulation (PWM) signal. Furthermore, because of the air compression and the leakage of the system, there exist parametric uncertainties, unmodeled dynamics and disturbances in the vacuum servo system. An adaptive backstepping control (ABC) strategy based on discontinuous projection mapping is designed. The adaptive backstepping control strategy inhibit the influence of system's parametric uncertainties through on-line update of the uncertain parameters, and uses its own robustness to eliminate the effects of unmodeled dynamics and disturbances. Compared with the sliding mode control (SMC) strategy, the experimental results show that when the tracking frequency reaches 3-4Hz, the adaptive backstepping control strategy can ensure good tracking performance.

On the Design of Energy-Saving Fluid Power Converter

The high energy efficiency and lightweight are recent trends in mobile hydraulics. In this paper, a new energy-saving fluid power converter (FPC) is designed to solve the problem of low energy conversion efficiency in hydraulic systems with variable load. The FPC is a kind of hydraulic transformer, it is similar to the DC transformer in working principle. Pulse width modulation (PWM) signal is used to control the high-speed on-off valves, and the high-speed on-off valve can switch supply ports between different pressure oil sources to achieve the adjustment of the FPC’s output. The FPC’s mathematical principle is analyzed in this paper, the influence of the friction between the inertial mass and the conversion cylinder on the system efficiency is studied. The influence of the PWM signal frequency, conversion cylinder cross-sectional area and inertial mass on the characteristics of FPC system is deduced. The results of the analysis are validated by Matlab/Simulink, and suggestions of selecting the design parameters of FPC are provided.

A Novel Pneumatic Brake Pressure Control Algorithm for Regenerative Braking System of Electric Commercial Trucks

Since the control of brake pressure has a significant impact on regenerative braking performance of electric vehicles, a novel combined brake pressure control algorithm based on two high-speed on-off valves is developed to improve the precision and timeliness of pressure tracking for the regenerative braking system of electric commercial trucks in this paper. First, a comprehensive mathematical model of the valve control system is built up which is composed of several sub-models and verified by experiments. Second, a PID controller with pulse width modulation (PWM) and a fuzzy controller with cooperative PWM are separately adopted in the proposed combined control algorithm to substitute for the traditional PWM approach. Moreover, through the numerical simulation studies, better control performance is obtained in MATLAB/Simulink on the basis of the built models. Finally, the experimental tests under various typical braking pressure input signals are carried out to verify the simulation results. The comparison between the simulation and experimental results fully demonstrates that the proposed control algorithm is feasible and the dynamic performance of this combined valve control algorithm is considerably improved compared with the conventional PID control algorithm.

Dynamic vacuum pressure tracking control with high-speed on-off valves

A vacuum pressure tracking system with high-speed on-off valves is a discontinuous system due to the discrete nature of high-speed on-off valves. Chamber pressure changes in the system are determined by the mass flow rates during the processes of charging and discharging. Here, a sliding mode controller with an asymmetric compensator based on average mass flow rate is designed for accurate vacuum pressure tracking. The controller output signal is converted into the duty cycles of the high-speed on-off valves via a pulse width modulation pulsing scheme. Owing to the extreme asymmetry of the processes, an asymmetric structure comprising one high-speed on-off valve in the charging unit and three high-speed on-off valves in the discharging unit is applied to weaken the impact of asymmetry. In addition, an asymmetric compensator is also designed to modify the pulse width modulation pulsing scheme to further eliminate the asymmetry. Experimental results indicate that the proposed controller achieves better performance in pressure tracking with the asymmetric compensator overcoming process asymmetry and enhancing system robustness.

Optimization of the High-speed On-off Valve of an Automatic Transmission

The response time of the high-speed on-off solenoid valve has a great influence on the performance of the automatic transmission. In order to reduce the response time of the high-speed on-off valve, the simulation model of the valve was built by use of AMESim and Ansoft Maxwell softwares. To reduce the response time, an objective function based on ITAE criterion was built and the Genetic Algorithms was used to optimize five parameters including circle number, working air gap, et al. The comparison between experiment and simulation shows that the model is verified. After optimization, the response time of the valve is reduced by 38.16%, the valve can meet the demands of the automatic transmission well. The results can provide theoretical reference for the improvement of automatic transmission performance.