Proportional Directional Valve Research Articles

Experimental and numerical analysis of cavitation in hydraulic proportional directional valves

This paper evaluates the effects of cavitation upon the performance of a hydraulic, proportional, directly-operated, directional valve by means of thorough experimental and numerical investigations. The experimental campaign is performed to estimate how cavitation changes the performance curves of the valve; in particular, the experimental equipment assembled to control the cavitation phenomenon inside the proportional valve is described, and the influence of cavitation on the flow rate and the flow coefficient as a function of the spool position is assessed. In addition, a full three-dimensional mixture model of the flow field within the valve is developed to accurately predict cavitation within the flow path for several spool positions. The accuracy of the numerical model is proven by previous experiences and by comparing the numerical results with the experimental data. After their validation, the numerical predictions are employed to analyse the characteristics of cavitation that cannot be experimentally evaluated, such as the volume of vapour, and to identify the zones where cavitation occurs. The numerical simulations are finally employed to predict how the variation in cavitation intensity influences the driving forces required to move the sliding spool and to calculate the minimum cavitation number for which the effects of cavitation are negligible.

Performance Analysis of Directional Control Valve: An Overview

Directional control valves start, stop or change the direction of flow in compressed air applications. To understand the different applications of compressed air and how valves are used, one must first have knowledge of the kinds and types of valves used by industries. This paper studies local valve control of the electro-hydraulic system. The slow response of hydraulic control valve usually becomes the hold-up of whole system performance. Although fast valves (e.g. high-bandwidth servo-valves) are available, they are far more expensive than slow valves (e.g. proportional directional control valves). To improve the performance of proportional directional control valves, three different types of controllers are synthesized. Firstly, based on the pole zero cancellation technique, an open loop compensator is designed which requires the accurate valve dynamic model information; Secondly, a full state feedback adaptive robust controller (ARC) is synthesized, which effectively takes into account the effect of parametric uncertainties and uncertain nonlinearities such as friction force and flow force. Finally, an output feedback ARC controller is synthesized to address the problem of un measurable states. Keywords: valve, hydraulic device, Simulink.

Control Strategy for Hydraulic Hybrid Servo Drive System of Heavy Load Robot

A kind of compound servo drive system is designed using the characteristics of hydraulic motor large torque and servo motor high accuracy positioning. Proportional pressure valve, proportional flow valve and electromagnetic directional valve was used to control hydraulic motor for tracking servo motor drive control and to achieve servo motor control for weight load of large torque and high accuracy positioning. Pressure, speed control strategy of using PID control is proposed based on the above hydraulic tracking drive system, achieve precise control for trajectory of robot articulated arm under heavy load conditions. And according to the requirements of the pressure, flow rate and reversing in the process of compound servo drive, a torque, speed and direction of the switching control strategy is put forward. Mathematical model is established and simulated based on tracking control system. The experiments indicate: under heavy load conditions, response speed, torque and angle control accuracy of hydraulic hybrid drive system meet the requirements with this control method and torque, speed switching control strategy.

Linear Analysis of Hydraulic Control System of an Electric-Hydraulic Proportion

1780 mm hot rolling transport chain electro-hydraulic proportional hydraulic control system of Shanghai Meishan Iron and Steel Co., LTD. Of Baosteel is taken as an example in this paper. The features, the controlling method, the electro-hydraulic proportional directional valve selection and the decision of the specific circuits of this kind of metallurgical equipment are introduced in this paper.

Neural Network Control for PPDCV Clinker Cooler System

Pilot Proportional Directional Control Valve (PPDCV) is used to control the clinker cooler actuator position for Cement Industries. PID controllers are satisfying control for the actuator position control with transient response and reduce steady state error. Uncertainty parameter cause unsmooth response small oscillation in actuator position. This work explains a neural network control for (PPDCV) system with uncertainty parameter, reduces the disturbance, and removes the oscillation in the response. The paper is focused on the possibilities of applying trained artificial neural networks for creating the system inverse models that are used to design inverse control algorithm for non-linear dynamic system. The simulation experiment is performed using Matlab and Simulink to show the response of these controllers.

Contour Error of the 3-DoF Hydraulic Translational Parallel Manipulator

The paper deals with a selected problem of contour error for the desired tracking trajectory of the spatial 3-DoF hydraulic translational parallel manipulator (TPM). The prototype hydraulic TPM consists of a fixed base and a moving platform connected by the joints with three hydraulic linear axes. The closed-loop kinematic chains of the hydraulic TPM create a 3-RRPRR structure in which revolute joints R and prismatic joints P step out. The three equal integrated electro-hydraulic axes are prismatic joints P in which hydraulic cylinders are integrated with position measuring systems and proportional directional control valves.

Experimental Modelling and Identification of Compressible Flow through Proportional Directional Control Valves

This paper derives an empirical model of the air flow through a variable area orifice of a 5-port proportional valve, in function of pressures at the supply port and at the pneumatic cylinder, i.e. including the flow resistance of the connecting tubes and fittings, and the (quasi-static) valve’s

2D21 Control schemes for an overlap type proportional directional control valve(The 12th International Conference on Motion and Vibration Control)

In a hydraulic control system(here, we call this a major control loop), a proportional directional control(PDC) valve with spool position feedback may work in minor(or inner) control loop. In this study the authors suggest control schemes to improve the performance of PDC valve control loop(a minor control loop). At first, the mathematical model for the PDC valve is obtained through an experimental identification process. Then, a dead-zone compensation scheme is devised. And the control schemes for the PDC valve are suggested so as to reject disturbances effectively, and to obtain good reference tracking ability. Finally, the suggested control schemes are verified through experiments.

The Pneumatic Position Control System Based on Fuzzy-PID

Put forward a kind of control system to achieve precise positioning of the pneumatic cylinder, coring to PC upper monitor and using Visual C++ as the development platform. Establish an experimental platform of pneumatic cylinder positioning control system: selecting the parameter self-tuning Fuzzy-PID control algorithm, using the proportional directional control valve, standard cylinder, displacement sensordata acquisition card and other components. the use of MATLAB to simulate and optimize, carry out the actual experiment on the basis of simulation. The experimental results proved the effectiveness and correctness of Fuzzy PID in pneumatic control system.

Research on the Dynamic and Static Characteristics of Electro-hydraulic Proportional Direction Valve with Flow Feedback

Research on the Dynamic and Static Characteristics of Electro-hydraulic Proportional Direction Valve with Flow Feedback

Adaptive robust motion trajectory tracking control of pneumatic cylinders

High-accuracy motion trajectory tracking control of a pneumatic cylinder driven by a proportional directional control valve was considered. A mathematical model of the system was developed firstly. Due to the time-varying friction force in the cylinder, unmodeled dynamics, and unknown disturbances, there exist large extent of parametric uncertainties and rather severe uncertain nonlinearities in the pneumatic system. To deal with these uncertainties effectively, an adaptive robust controller was constructed in this work. 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, unmodeled dynamics and disturbances. 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 was applied. In order to solve the conflicts between the sliding mode control design and the adaptive control design, the projection mapping was used to condition the RLSE algorithm so that the parameter estimates are kept within a known bounded convex set. Extensive experimental results were presented to illustrate the excellent achievable performance of the proposed controller and performance robustness to the load variation and sudden disturbance.

Development of a New Type 4D Dynamic Seat Platform Control System Based on PLC

This article has introduced the development method of a kind of 4d cinema dynamic seat control system based on PLC, expounds the system's hardware structure , working principle, function characteristics, etc. The system's power is provided by hydraulic pump, hardware adopts closed loop feedback control system constituted by omron PLC, A/D module, D/A module, linear displacement sensor and electromagnetic proportional directional valve. The system has good stability, high cost performance, miniaturization, intelligent, etc.

The Design of Control System for Motion Platform Based PLC

In this paper, a new-style platform control system with three degree of freedoms: up-down motion, left-right rolling and front-rear pitching is designed ,and also its composition, operating principle and soft design method are introduced. The system is driven by air cylinder and consists of FX series PLC, AD module, DA module, proportional valves , sliding rheostats and so on. Among these modules, sliding rheostats works as a feedback component to comprise a closed loop. Furthermore, to ensure the high positioning precision, thePIDalgorithm is applied. In addition, to control the motion flow reliably, the ladder logic diagram of the turn-off prior to turn-on is used to replace Sequential Function Chart. Experiments show that the motion platform is steady and safety when the proportional valves and directional valves are controlled by PLC.

Fluid-dynamic design optimization of hydraulic proportional directional valves

This article proposes an effective methodology for the fluid-dynamic design optimization of the sliding spool of a hydraulic proportional directional valve: the goal is the minimization of the flow force at a prescribed flow rate, so as to reduce the required opening force while keeping the operation features unchanged. A full three-dimensional model of the flow field within the valve is employed to accurately predict the flow force acting on the spool. A theoretical analysis, based on both the axial momentum equation and flow simulations, is conducted to define the design parameters, which need to be properly selected in order to reduce the flow force without significantly affecting the flow rate. A genetic algorithm, coupled with a computational fluid dynamics flow solver, is employed to minimize the flow force acting on the valve spool at the maximum opening. A comparison with a typical single-objective optimization algorithm is performed to evaluate performance and effectiveness of the employed genetic algorithm. The optimized spool develops a maximum flow force which is smaller than that produced by the commercially available valve, mainly due to some major modifications occurring in the discharge section. Reducing the flow force and thus the electromagnetic force exerted by the solenoid actuators allows the operational range of direct (single-stage) driven valves to be enlarged.

피드백 선형화 보상기와 외란 관측기를 이용한 2개 유압 실린더의 동기 제어

In the study, a control strategy using a feedback linearization compensator and a disturbance observer was suggested and applied to the synchronization control of two hydraulic cylinders. The hydraulic system consists of a proportional directional control valve with overlap characteristic near the neutral position, a conventional hydraulic cylinder and an external load. The control performances of the system were verified through numerical simulations. From the simulations, it was ascertained that excellent control performances were obtained with the suggested control strategy.

Theoretical and Experimental Analysis of a Coupled System Proportional Control Valve and Hydraulic Cylinder

The aim of this paper is to analyze the driving system actuated by a proportional directional control valve on a hydraulic cylinder. In order to evaluate the dynamic interaction between the proportional valve and the cylinder theoretical analysis, numerical simulations as well as experimental test are performed. Coupling cylinder and proportional valve, it is very important to know the ratio of their natural frequencies. In particular, if the valve is characterized by a lower natural frequency, its behavior prevails so that no resonance peak can be observed on the coupled system. On the contrary, resonance phenomena can be observed in all the other cases. It is important that these phenomena are preventively taken into account to realize a precise and accurate control system of a hydraulic axle.At last, three different control methods are tested on the coupled system:Proportional Integral Derivative technique (PID), the adaptive One-Step-Ahead control technique, and an expert control technique and the obtained precisions are very interesting.

Suppressing water hammer of ship steering systems with hydraulic accumulator

This article is a contribution to the design of the hydraulic steering system with an accumulator of different parameters on suppressing water hammer. The accurate model taking account of the characteristics of the entrance of the hydraulic accumulator, which have great influence on the frequency characteristics of the accumulator is developed. In addition, this article proposes a more comprehensive distributed parameter model of the hydraulic steering system with an accumulator installed before the proportional directional valve, which takes into account both the relief valve and the pipeline between the hydraulic accumulator and the proportional directional valve. The dynamic characteristics of the hydraulic steering system were analyzed both in the frequency and time domain. The numerical simulation of water hammer which used a holistic unsteady-friction model has been performed by the method of characteristics and finite difference method with spatial interpolation using Fortran language. The law that the natural frequency of the accumulator which is equal or approximate to the frequency of water hammer in pipeline has good effect on suppressing water hammer is validated by analytical and numerical simulations as well as experimental results, for the design of the nominal volume and charged pressure of the hydraulic accumulator in the hydraulic steering system.

Control of four wheel steering using independent actuators

In four wheel steering (4WS) system the steering angles in each wheel must follow Ackermann steering geometry in order to eliminate the lateral slippage of the wheels. In agricultural vehicles, the steering actuators are typically hydraulic cylinders. In pure four wheel steering with two degrees of freedom and without additional constraints, a straight forward way is to install one actuator with a position sensor per wheel to realize Ackermann principle. In agricultural robot studies four wheel steering is a common kinematic structure. In this paper, modeling and control of steering in a 4WS remote controlled tractor is studied. The tractor is equipped with four asymmetric cylinders that steer each wheel, without any additional mechanical rods. The hydraulic system consists of one variable displacement pump and four proportional directional valves with load sensing function. The system model is split into subsystems and the overall model contains both dead-time delay, first order dynamics, static nonlinearities, temperature dependency and combined saturation. Besides modeling and analysis, the paper presents a control design that compensates nonlinearities but also takes care of saturation while compensating the dynamics. The objective in control is synchronous motion in the position control of the steering angles of all wheels. The results show controller performance in single wheel motion without saturation and overall controller performance under saturated pump flow.

Hydraulic System Research of the Pumping Unit Based on Electro-Hydraulic Proportional Control Technology

Trapezoidal curve is selected as the hydraulic pumping unit load running speed curve. Designed a new hydraulic system of hydraulic pumping unit according to the electro hydraulic proportional control technology and then expounded its working principle, in which the electro-hydraulic proportional directional throttle valve have been used. The system is feasible on the theory by analyzing its mathematical model. It would meet the requirement of hydraulic pumping unit and realize the advantages of it via controlling the input current signal of the amplifier.

PID Parameters Tuning of Proportional Directional Valve Based on Multiple Orthogonal Experiments Method: Method and Experiments

This paper presents a method to tune the PID parameters of controller for proportional directional valve without modeling and priori knowledge of the system. The optimization of the PID parameters is achieved through statistic analysis by using the proposed method. The principle and the implement of the method is explicitly introduced first. Then, the experiment is executed, and Ziegler-Nichols method is also applied in PID tuning for comparison. The results show that the presented method performs better and is proved to be effective. And the method is also straightforward to carry out.