The COVID-19 pandemic has revealed numerous global health system deficits, even in developed countries. The high cost and shortage of treatment, health care, and medical devices are the reasons. ...Aside from new mutations, the availability of respirators is an urgent concern, especially in developing countries. Even after the pandemic, respiratory diseases are among the most prevalent diseases. Researchers can help reduce treatment costs by offering scalable, open-source solutions that are manufacturable. Since March 2020, serious efforts have been made to reduce the problems caused by the lack of respirators at the lowest possible cost. In this research paper, a unique and integrated solution for a fully automatic ventilator is presented and described. The design considers the cost, speed of assembly, safety, ease of use, robustness, portability issues, and scalability to fit all requirements for emergency ventilation. Furthermore, the device was developed using turbine technology to generate air pressure. The work describes a low-cost alternative ventilator that uses a novel proportional-valve approach to control oxygen mixing process, control circuit, and control algorithm. The current software supports pressure mode controllers, and it can be upgraded to volume-mode or dual mode without any modifications in the hardware. In addition, the hardware, particularly the electronic circuit, has idle input/output ports for further development. Based on the evaluations of the developed ventilator using an artificial lung, the system exhibited acceptable accuracy regarding to the pressure, leak compensation, and oxygen concentration levels. The designated safety conditions have been met, and the safety alarms tripped according to any violations. Moreover, all design files are provided with clear instructions to rebuild the device, despite the complexity of electronics assembly. The system can be described as a development kit, which can shorten the time for researchers/manufacturers to develop a device equivalent to the expensive devices available in the market.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Due to a sharp change in the direction and velocity of the fluid flow in the hydraulic distributor, hydrodynamic forces arise. When positioning and holding the spool, the magnitude of the above ...forces determines the required control power. The aim of the article was to find an optimal constructive solution that would reduce the influence of hydrodynamic forces. In the article we have considered the theoretical foundations laid in the analytical solution of the problem of calculating the magnitude of the hydrodynamic force acting on the plunger of the spool. In addition, a numerical experiment was carried out using CAD Solidworks and the Flow Simulation application package and a comparison of the results obtained with the analytical solution of the problem. During the numerical experiment, it was found that by upgrading the spool sleeve, it is possible to reduce the value of the hydrodynamic force by 4.5 times, compared with the original design. At the same time, it was found that the modernization of the plunger does not further reduce the maximum hydrodynamic forces. The article highlights the economic benefits of reducing the required power to control the hydraulic distributor. The article may be of interest to both researchers whose research interests lie in the field of hydrodynamics, and manufacturers of hydraulics.
The main objective of this article is to analyse flow coefficient of a proportional directional valve with integrated spool position controller. The valve geometry has been modified by creating ...additional undercuts on the spool, which provide improved flow characteristics, especially at low flow rates. The analysis consisted of two phases, including computer simulations and test bench experiments. At first, flow through the valve was simulated by the means of CFD method in ANSYS/Fluent software, assuming the fixed spool positions. Based on the results, flow coefficient values were determined. The results showed, that in the examined gap width range, the coefficient value is mainly related to the spool position, and to a lesser extent to the volumetric flow rate. Hence, a proposal to formulate the flow coefficient value as a function of spool position or spool position and flow rate was made. Three approximating functions were determined in Matlab system on the basis of the obtained CFD results: a linear curve μ=f(xg), as well as a linear polynomial surface and a quadratic polynomial surface μ=f(xg,Q). Next, the results were verified by experiments conducted at a test bench.
The best fit flow coefficient function was then used in the subsequent simulations on a multi-actuator system comprising three parallel-connected valves supplied by a single pump. In this case, each valve was set a different fixed spool position, which resulted in a different throttle gap width. Analysis of the system was carried out using an own-developed computer software for solving the analytical equations. Finally, the results were compared to those obtained by means of a CFD method, and a satisfactory compliance was achieved.
•Research of a proportional directional control valve with a spool position controller.•A concept of formulating flow coefficient as a function of spool position and flow rate.•CFD simulations in a wide range of spool positions and flow rates.•Determination of flow coefficient functions and verification by test bench experiments.•Analysis of a multi-valve system using the determined flow coefficient function.
Abstract
The dynamic characteristic parameters of the synchronous dual-proportional pressure integrated valve are of great significance to its research. Among them, the outlet pressure tracking error ...and the flow resistance characteristics of the internal flow field have a great influence on the dynamic characteristics of the valve. The tracking error of the valve under specific working conditions is analyzed by means of digital simulation, and the flow resistance characteristics of the internal flow field are further obtained.
This paper presents a new rotary proportional flow control valve with Cam-Nozzle configuration. The rotating cam against the fixed nozzle changes the flow area and then can meter the fuel flow. This ...valve equipped with a pressure compensator plunger type valve to retaining constant pressure difference across the flow control or metering valve. The cam shaft directly coupled to an electronic servomotor type rotary actuator and then it is possible to apply digital control techniques such as pulse width modulation (PWM) in this control system. This new valve configuration is developed for an electro hydro mechanical fuel control system in a gas turbine engine. In addition to aero engine application, this type of flow metering valve can widely be used in industrial hydraulic systems. In this unit, the output flow is proportional to the cam's angular position (or throttle command) and it is not sensitive to pressure fluctuations at nozzle inlet and outlet. The aim of this new design is to modify a manual single adjusted hydro-pneumatic fuel control unit to obtain a new electro-hydraulic fuel control system for a gas turbine engine. The main innovations in the presented fuel metering unit include new design of the rotary valve opening shape (Cam-Nozzle) without metal to metal contact, use of a rotary electronic actuating mechanism and also direct coupling between the actuator and the rotating cam. The increased fuel metering precision in the new flow control valve has improved the ultimate control accuracy of system. A computer simulation software based on the proposed model, is performed to predict the steady state and transient performance and to analyze effect of important design parameters on valve outlet fuel flow and obtain the final design parameters. The validity of the proposed valve configuration is assessed experimentally in the steady state and transient modes of operation. The results show good agreement between simulation and experimental in both modes (max. 4% deviation).
•A rotary proportional flow control valve with high precision flow control without metal to metal contact is studied.•Proposal of using flow control valves with new opening shape (Cam-Nozzle).•Derivation of simulations in Matlab and verified experimentally on a test bench.•Proposal of a modified rotary direct drive proportional valve for turbine engine fuel control systems.•A novel flow control valves actuation system in gas turbine fuel control units using servomotors.
This study was conducted to develop a proportional-integral-derivative (PID) control algorithm considering viscosity for the planting depth control system of a rice transplanter using various ...hydraulic oils at different temperatures and to evaluate the performance of the control algorithm, and compare the performance of the PID control algorithm without considering viscosity and considering viscosity. In this study, the simulation model of the planting depth control system and a PID control algorithm were developed based on the power flow of the rice transplanter (ERP60DS). The primary PID coefficients were determined using the Ziegler-Nichols (Z-N) second method. Routh’s stability criteria were applied to optimize the coefficients. The pole and double zero points of the PID controller were also applied to minimize the sustained oscillations of the responses. The performance of the PID control algorithm was evaluated for three ISO (The International Organization for Standardization) standard viscosity grade (VG) hydraulic oils (VG 32, 46, and 68). The response characteristics were analyzed using statistical method (ANOVA) and Duncan’s multiple range test (DMRT) at a significant level of 0.05 were performed through the statistical software SPSS. The results show that the control algorithm considering viscosity is able to control the pressure of the proportional valve, which is associated with the actuator displacement for various types of hydraulic oils. It was noticed that the maximum pressure was 15.405 bars at 0, 20, 40, 60, 80, and 100 °C for all of the hydraulic oils. The settling time and steady-state errors were 0.45 s at 100 °C for VG 32 and 0% for all of the conditions. The maximum overshoots were found to be 17.50% at 100 °C for VG 32. On the other hand, the PID control algorithm without considering viscosity could not control the planting depth, because the response was slow and did not satisfy the boundary conditions. The PID control algorithm considering viscosity could sufficiently compensate for the nonlinearity of the hydraulic system and was able to perform for any of temperature-dependent viscosity of the hydraulic oils. In addition, the rice transplanter requires a faster response for accurately controlling and maintaining the planting depth. Planting depth is highly associated with actuator displacement. Finally, this control algorithm considering viscosity could be helpful in minimizing the tilting of the seedlings planted using the rice transplanter. Ultimately, it would improve the transplanter performance.
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•A resonant piezoelectric proportional valve driven by a bending actuator was proposed.•The flowrate proportional regulation of the proposed valve was realized.•The theoretical model ...was adopted to predict the flowrate.•The flowrates for the deionized water and silicone oil were 1.256 L/min and 0.221 L/min.
A resonant piezoelectric proportional valve for large flowrate regulation was proposed in this work. The large flowrate of the valve and its proportional regulation under high differential pressure were achieved using a bending sandwich actuator (BSA). First, the configuration and operation principle of the valve were depicted, and its structural parameters were determined by simulated analyses. Then, the theoretical analysis method was accomplished to predict the flowrate, and the direct fluid structure interaction simulation was used to validate the theoretical model. Ultimately, a prototype was fabricated and experimentally measured for the output performances. The results denoted that the output displacement of the BSA under the loaded condition was 91.69 μm when the resonant frequency and voltage were 2.19 kHz and 100 Vp-p; and the corresponding flowrates for the deionized water (DIW) and silicone oil (SLO) were 1.256 L/min and 0.221 L/min at 344.75 kPa. Besides, the cut-off pressures for the DIW and SLO were 289.59 kPa and 310.275 kPa under −300 V0-p; and the leakages were 0.5 mL/min and 0.2 mL/min under 344.75 kPa. This valve is expected to be applied to the cooling systems, hydraulic actuators.
An electro-hydraulic elevator is a new type of enhanced elevators that are used in low-rise buildings that do not exceed more than three floors. In this paper, an electro-hydraulic servo system for ...controlling the speed of a hydraulic elevator prototype by using a proportional valve and PID controller was investigated theoretically and experimentally. A three floors elevator prototype model with 76cm height was built including hydraulics components and electrical components. The elevator system is fully automated using the Arduino UNO board based Data Acquisition (DAQ) system. LabVIEW software is used to control the hydraulic elevator system through L298 DC drive via the DAQ board. The best PID gains was obtained experimentally. The elevator system prototype could be emplimented for educational purposes; such as learning the undergraduate students in the Electromechanical Engineering Department in the University of Technology how to structuring the electro-hydraulic elevator as well as the appropriate control strategy.
The moving mesh method of computational fluid dynamics (CFD) in COMSOL Multiphysics is utilized to obtain transient characteristics of the flow force associated with displacements, velocities and ...pressures. Secondly, a dynamic finite element model (FEM) of the electromagnetic subsystem is also established by the moving mesh. Thirdly, the transient force of the fluid subsystem and the spring force of the mechanical subsystem will be loaded on the valve spool, and the control voltage characterized as an analytic equation is associated with the electromagnetic coil. As a result, a coupling FEM of this valve combining the dynamic data of fluid system, a dynamic FEM of the electromagnetic system and mathematical models could be achieved. Finally, dynamic characteristics of the valve can be directly extracted from computing results in this software. Reflected through the fast response time, displacement, velocity and flow rate, dynamic behaviors of a miniature valve have been simulated effectively through such a coupled method.
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