A simplified mathematical model is developed to study the dynamic behavior of an electro-pneumatic proportional valve for pressure control. The valve is capable of supplying a pressure that can ...reproduce an electrical signal (electrical current intensity).
In addition to parameters and independent variables, every differential equation constituting the model contains a coefficient which includes several geometrical parameters and some parameters related to flow through the valve. This coefficient may be determined by comparing results from experiments and simulated tests. The application of this method has given simulation-derived results that sufficiently approximate the experimental results of practical applications.
Pneumatic Positioner with Fuzzy Control Belforte, G.; Raparelli, T.; Velardocchia, M.
IFAC Proceedings Volumes,
October 1992, 1992-10-00, Letnik:
25, Številka:
29
Journal Article
A pneumatic positioner with closed loop fuzzy logic control is described. The system consists of a pneumatic cylinder, two proportional valves, a position and speed sensor, a fuzzy controller and an ...A/D-D/A conversion board. No braking devices for maintaining position are provided on the cylinder rod. The control considers position error and actuator speed as antecedents, and valve control voltages as consequents. Membership functions, the set of rules and the weights of each were obtained by considering the component characteristics and the relationships between the antecedents and the flow rates to the cylinder chambers with varying control voltages. The latter were calculated using the min-max-center of gravity criteria. Experimental tests were carried out on the positioning system with different reference signal shapes and with different applied loads. Results show good positioning accuracy and repeatability, absence of overshoot and system stability under varying operating conditions.
Proportional valves are a great alternative when an application requires more than on-off control, but not the high precision and expense of servovalves. As such, proportional valves are widely used ...in a multitude of applications, including the control of gas and air flow from medical respirators, dialysis machines, and paint-delivery and semiconductor-manufacturing systems. The beauty of the valves is the ease with which they can vary the rate of flow, with output proportional to input current. However, most such valves have several major characteristics that can make precise control difficult, including hysteresis and variable maximum flow and gain.
IC Sensors Inc. has developed a new silicon-based microvalve for vital-signs monitors, respirators and analytical instruments. Unlike conventional microvalves which use magnetic actuation, the new ...Model 4425 microvalve uses thermal actuation which allows it to run silently without the clicking sound usually associated with monitoring equipment. The new microvalve can control gas flow, pressure and liquids in pilot valve arrangements.
High performance proportional valves are commonly utilized for precise control of aircraft actuators to ensure flight safety. Fault diagnosis play a crucial role in maintaining equipment reliability. ...However, traditional diagnostic methods using vibration signals face challenges such as inability to directly measure failure points, fault characteristics being influenced by sensor position, and large data processing volume, limiting engineering application scope. This paper introduces a valve spool wear fault diagnostic method based on energy loss model and data hybrid drive, leveraging throttling loss characteristics. An energy loss failure mechanism model, incorporating differential pressure and flow rate of valve port, was established, and experimentally verified. This method effectively addresses the limitations of vibration sensors in diagnosing aviation hydraulic systems. By combining particle swarm optimization algorithm with deep extreme learning machine, the number of neurons, weight distribution, and data set ratio are rapidly optimized, reducing data processing complexity and enhancing diagnostic efficiency. Comparative tests demonstrate a significant increase in average diagnostic accuracy rate, with more than 8% improvement after integrating energy loss information and particle swarm optimization, reaching over 98%. The proposed method exhibits superior performance in average diagnostic accuracy rate and stability compared to other methods and can be served as a valuable reference for predicting faults in aviation hydraulic valves.
For analyzing ejector's performance in the system, an ejector for a 10 kW polymer electrolyte membrane fuel cell (PEMFC) system was first designed, manufactured, and a 10 kW PEMFC system bench was ...built up. A proportional valve and PI pressure feedback control method were adopted to control the hydrogen supply and anode inlet pressure. During the test, performances between dead-ended anode (DEA) mode and ejector mode were compared. Ejector's performances in the system, i.e., volume flow recirculated ratio, difference pressure, dynamic responses of primary pressure, anode inlet pressure, and recirculated gas flow rate during the purge process and current variation condition, were investigated. The results show that pressure adjustment is accurate, continuous, and fast using the proportional valve and PI pressure feedback control method. The hydrogen consumption rate in the ejector mode can reduce from 5% to 10% compared with the rate in the DEA mode except for the stack current 5 A and 10 A conditions. For better water removal out of the anode channel in ejector mode, the maximum stack power increases from 5.11 kW (DEA mode) to 9.56 kW (ejector mode). Anode pressure surge caused by the purge valve switching enhances the ejector's recirculated performance significantly.
•An ejector for a 10 kW PEMFC system is designed, manufactured and evaluated.•The stack in ejector's mode shows a better performance than that in DEA mode.•Hydrogen recirculation can reduce the hydrogen consumption.•The proportional valve with the PI pressure feedback method can accurately control the anode inlet pressure.•Anode pressure surge can enhance ejector's recirculated performance.
•A modified magnetic cycle method fusing of local finite element and mathematical models was proposed.•Coupled dynamic mathematical models for an electro-hydraulic proportional valve based on ...mechanical, electrical, electromagnetic and fluid subsystems were presented.•A coupled finite element model for an electro-hydraulic proportional valve considering all subsystems was established.
On the basis of differences of the magnetoresistance, magnetic field direction and relative permeability in metal components, a magnetic cycle method with modifications also characterizing magnetic flux densities of different components in real time is firstly proposed, thus establishing mathematical models for the electromagnetic subsystem of an electro-hydraulic proportional valve. Further integrating electrical, electromagnetic, fluid dynamic and mechanical models together, analytical and fully coupled mathematical models are achieved so that nonlinear dynamic performance determined by the structural parameters, materials, fluid, driving strategies and interaction of subsystems will be captured effectively. Secondly, a coupled finite element (FE) model with all subsystems is also established, and dynamic behaviors under different driving strategies such as the high-low voltage (HL), direct current (DC) and pulse width modulation (PWM) are reflected through the moving mesh method in COMSOL Multiphysics, further suggesting the HL strategy as the better one because of small overshoot and shortest response times. Under the same driving strategy such as PWM, results of two models are highly similar to each other with the maximum time difference of 5 ms and the absolute error of steady-state position of 0.0104 mm. Therefore, two dynamic models are relatively accurate, and such an integrated method presents another reference for predicting dynamic behaviors of complex valves.
The main objective of this article was to analyse flow forces acting on a spool of a proportional control valve in the initial phase of the spool gap opening. Accordingly, modification of the spool ...geometry has been proposed in order to reduce flow force values. The modification consisted in making small circular undercuts at the apex of main triangular grooves, which were made on the spool. The undercuts were made in order to improve flow characteristics, for the gap width less or equal to 0.40mm. Two arrangements of undercuts were tested. In the first version the undercut was made only on one groove, while in the second version two undercuts were located symmetrically on both sides of the spool. Simulations were carried out by the means of CFD methods and allowed both axial and radial flow forces to be determined. The simulation results showed that the use of a single undercut allowed the valve to operate at a very low flow. However, a significant radial force asymmetry appeared. The use of symmetric undercuts reduced the unevenness of radial forces, with a relatively small increase in flow rate and axial force. The obtained axial force values were next verified experimentally on a test bench.
•CFD analysis of a proportional control valve.•Obtaining flow characteristics in the initial phase of spool gap opening.•Determining axial and radial components of forces acting on the spool.•Making additional notches at the apex of the main operating grooves.•Improving flow characteristics with simultaneous reduction in resistance forces.
