Hydraulic Proportional Valve Research Articles

Semi-empirical model for a hydraulic servo-solenoid valve

High-performance proportional valves, also called servo-solenoid valves, can be used today in closed-loop applications that previously were only possible with servo-valves. The valve spool motion is controlled in a closed loop with a dedicated hardware controller that enhances the valve frequency response and minimizes some non-linear effects. Owing to their lower cost and maintenance requirements as well as increasing performance they can compete with servo-valves in a large number of applications. This paper describes a new semi-empirical modelling approach for hydraulic proportional spool valves to be used in hardware-in-the-loop simulation experiments. The developed models use either data sheet or experimental values to fit the model parameters in order to reproduce both static (pressure gain, leakage flowrate and flow gain) and dynamic (frequency response) valve characteristics. Valve behaviour is divided into two parts: the static behaviour and the dynamic behaviour. A parameter decoupled model, with a variable equation structure, and a flexible model, with a fixed equation structure, are proposed for the static part. Spool dynamics are modelled by a non-linear second-order system, with limited velocity and acceleration, the parameters being adjusted using optimization techniques.

Steady State and Dynamic Characteristics of Water Hydraulic Proportional Ceramic Spool Valve

AbstractWater hydraulics is both old and new technology area. The first fluid power applications were using water as pressure medium already in 18th-century, but the modern water hydraulics has been rapidly growing just recently in 1980's and 1990's. The main reasons for the comeback are environmental and safety aspects. Water hydraulics offers a significant alternative to establish motion control systems in environments, where possible oil leakage can cause serious problems.One of the major tasks to solve in modern water hydraulics is to achieve more accurate control systems than today`s technology provides. The present water hydraulic control valves are not yet at the same technology level as that of oil hydraulics. This means that a lot of effort has to be put to develop better and more accurate valve constructions and on the other hand more intelligent control methods has to be developed to achieve reasonable valve characteristics.This paper concentrates on a study of water hydraulic proportional valv...

Design and Simulation of an Entry Edge Guide Control System for Tandem Cold Mills

A new entry edge guide control system for cold mills was designed using a dual-mode control system. One control loop regulated the cylinder pressure to prevent machine damage due to pressure surge while the other loop provided edge guide position control. The target control level was ±1.59 mm accuracy for a maximum operating strip speed of 530 mpm with coil sidewall location variations of ±12.5 mm/sec. A mathematical model was developed to simulate the dynamic behavior of the control system using the state space design method. The control system features two PID controllers, two hydraulic proportional valves, and a digital edge sensor. The PID tuning constants and the hydraulic proportional valves were specified by simulation results considering system response and signal noise. Data from 35 coils was used to investigate control performance. The results show that the average standard error is entirely acceptable. The majority of the coils are expected to have tracking errors less than the required accuracy.

DEVELOPMENT OF WATER HYDRAULIC PROPORTIONAL CONTROL VALVE

Our development program fabricated a proportional control valve that exclusively uses water as its working fluid. The valve is equipped with a spool, and the spool is directly driven by a proportional solenoid that is modified for water use. Characteristics of the proportional solenoid are described first in this report while proving its performances similar to those of the conventional oil hydraulics.Following, structural characteristics of the water hydraulic proportional control valve are discussed. Water, the valve's working fluid, is low in lubricity and viscosity; therefore, hydrostatic bearings that support the spool are installed in the valve. In addition, to stabilize movement of the spool, damping orifices are provided. Particularly, the hydrostatic bearing portion is designed such that it minimizes the total leakage including bearing flow while obtaining load carrying capacity. The constant flow from the hydrostatic bearings prevents water from decaying in the valve. Lastly, the paper introduces experimental results of cylinder positioning controlled by the developed water hydraulic proportional control valve to verify its satisfactory performances as a control valve.

Adaptive Flow Rate Control of a Hydraulic Proportional Valve.

The use of hydraulic proportional valves in industry is becoming increasingly popular as they have better performance than conventional on-off valves and lower cost than servovalves. However, due to significant time delay in valve dynamics, they are currently used for low-accuracy and low-dynamics applications. In this study, an adaptive self-tuning controller is proposed to enable a hydraulic proportional valve to achieve accurate set-point flow rate control. A moving model which reduces the system order and hence reduces the identification effort was used for the controller design. The controller is based on the pole-placement technique which shifts the dominant pole to the desired location. In addition, a predictor has been proposed to overcome the effect of the time delay. Experimental results have shown that the proposed self-tuning controller is better than the conventional PI controller as both transient oscillation and steady-state error shown in the PI control have been significantly reduced. Also, the performance of the closed-loop system is very robust as the system response remains the same under Various operating conditions.