Fluidic Control System Research Articles

A Pressure Control Valve Using MR Fluid

A novel control valve using MR fluid (MR valve) is proposed for fluid control systems. The MR or Magneto-Rheological fluid is a newly developed functional fluid whose apparent viscosity is controlled by the applied magnetic field intensity wider than that of Electro-Rheological fluid. The MR valve consists of a flow channel between a pair of magnetic poles and the differential pressure is controlled by the applied magnetic field intensity. It features simple, compact and reliable structure without moving parts.An MR valve is fabricated. The magnetic poles have 20mm×3Omm in face size and 3mm in gap length and are connected to an electromagnet. Through experiments on the static characteristics, it is found that the differential pressure is controlled by the applied magnetic field intensity under little influence of the flowrate, which corresponds to a pressure control valve. The differential pressure and output power changes of 0.68MPa and 20W are obtained with the input current and power changes of 710A-turns and 1.9W at the flowrate of 30cm3/s (1.8L/min).

Micro fluidic control systems in deep etch optical lithography

Microfluidic devices and components have the potential to provide robust and reliable controllers for process and control systems within the chemical and nuclear industries. Two fluidic amplifier devices are described and operational results based upon CFD simulations reported. The physical operation of both devices is examined. Simulations indicate that pressures of up to 30 kPa can be switched in less than 1 ms by a pressure of the order of 3 kPa. Each component is intended to form part of a complex combinational control system. Fabrication by the deep etch LIGA process is expected to enhance device versatility by ensuring package sizes are as small as possible. Simulated results suggest that with device heights of 500 μm, operational integrity can be maintained.

Development of a MEMS microvalve array for fluid flow control

A microelectromechanical system (MEMS) microvalve array for fluid flow control is described. The device consists of a parallel array of surface-micromachined binary microvalves working cooperatively to achieve precision how control on a macroscopic level. Flow rate across the microvalve array is proportional to the number of microvalves open, yielding a scalable high-precision fluidic control system. Device design and fabrication, using a one-level polycrystalline silicon surface-micromachining process combined with a single anisotropic bulk etching process are detailed. Performance measurements on fabricated devices confirm feasibility of the fluidic control concept and robustness of the electromechanical design. Air-flow rates of 150 ml/min for a pressure differential of 10 kPa were demonstrated. Linear flow control was achieved over a wide range of operating flow rates. A continuum fluidic model based on incompressible low Reynolds number flow theory was implemented using a finite-difference approximation. The model accurately predicted the effect of microvalve diaphragm compliance on flow rate. Excellent agreement between theoretical predictions and experimental data was obtained over the entire range of flow conditions tested experimentally.

Fuzzy Fluid Control System with confirmation of clinical staffs

Fuzzy Fluid Control System with confirmation of clinical staffs

The fluid systems for the SLD Cherenkov Ring Imaging Detector

The design and operation of the fluid delivery, monitor, and control systems for the SLD barrel Cherenkov Ring Imaging Detector (CRID) are described. The systems deliver drift gas (C/sub 2/H/sub 6/+TMAE), radiator gas (C/sub 5/F/sub 12/+N/sub 2/), and radiator liquid (C/sub 6/F/sub 14/). Measured critical quantities such as electron lifetime in the drift gas and ultraviolet (UV) transparencies of the radiator fluids, together with the operational experience, are reported. >

Integrated micro flow control systems

The integration of fluid control systems on a silicon wafer allows the control of a small volume of fluid by virtue of a negligible dead volume. Microvalves driven by small piezoactuators have been fabricated on a silicon wafer by micromachining. Three types, i.e. normally open, normally closed and three-way, were developed. An integrated mass flow controller consisting of a small thermal mass flow sensor and a normally closed microvalve was fabricated for precise gas control. The small thermal capacity of the flow sensor gives high sensitivity and quick response. The response time of the mass flow controller is less than 2 ms, which is faster than that of previous ones by nearly a thousand times. The integrated system gives rise to a precise flow control for advanced deposition processes, etc.

High-Speed Computing and Artificial Intelligence Connection

High-speed computers, though they provide immense numerical processing power, are often unable to improve significantly the execution time of composite computational processes; the bottleneck is a lack of automated intelligent interfaces and higher-level reasoning functions. It is the expectation that the coupling of high-speed numerical computing with the symbolic knowledge of how to employ numerical processing techniques will be necessary to develop the powerful, highly integrated software systems required to solve those large-scale problems in science and engineering currently deemed intractable. Many scientific and engineering problems require very large amounts of computing, and this demand will continue to grow in the foreseeable future. In some application areas such as aerospace structural design, computational fluid dynamics, propulsion, and control systems design, the speed of supercomputers will have to increase two to three orders of magnitude to meet the demands of the technological progress desired in the next decade.

Physiological responses to prolonged bed rest and fluid immersion in humans.

Rest in bed and immersion in water have been used for centuries by physicians and healers in treating injury and disease. The qualitative similarity of acute and chronic responses to bed rest, immersion, and weightlessness has sparked renewed interest in and a resultant greater understanding of the mechanisms of disuse deconditioning. Some combination of changes in hydrostatic pressure, reduced total metabolism (exercise), compression force on weight-bearing bones, as well as psychological factors associated with prolonged confinement in a new environment probably comprise the major input stimuli for the adaptive responses. Virtually every physiological system is affected. Early responses involve the fluid, electrolyte, and blood pressure control systems with significant muscular atrophy and decreases in bone density occurring over weeks and months. Much effort has been expended to describe the various responses to bed rest and immersion with understandably less effort devoted to research during weightlessness. Future research should be directed mainly toward an understanding of the mechanisms of these adaptive responses. Additional work is especially needed to elucidate the effects of deconditioning on drug metabolism, functioning of the immune system, carbohydrate metabolism, protein and peptide metabolism in muscle, and calcium metabolism as it affects integrity of bone.

Performance characteristics of plane-wall venturi-like reverse flow diverters

The results of an analytical and experimental study of plane-wall venturi-like reverse flow diverters (RFD) are presented. In general, the flow characteristics of the RFD are reasonably well predicted by the mathematical model of the RFD, although a divergence between theory and data is observed for the output characteristics in the reverse flow mode as the output impedance is reduced. Overall, the performance of these devices indicates their usefulness in fluid control and fluid power systems, such as displacement pumping systems.

4387685 Fluidic control system including variable venturi

4387685 Fluidic control system including variable venturi

Fluidics in Aircraft Engine Controls

Fluidics is a particularly appropriate technology for engine controls as it is capable of measuring pressure ratio, one of the basic engine performance parameters, as a fundamental quantity. This results in improved accuracy of measurement and obviates the need of conventional systems to utilize nonoptimum, but easier to measure, control parameters. A wide range of aircraft engine controls has been developed covering controls for compressor inlet guide vanes, compressor bleed valves, engine fuel flow including engine instrumentation. Total fluidic unit deliveries exceed 4200 and the civil operating hours exceed 13.5 million. As a further development, a completely fluidic engine control system is proposed with an electronic computer controlled secondary control or trim system for efficiency optimization.

Frequency Response Analysis of Fluid Control Systems for Parabolic Trough Solar Collectors

Previous studies of solar collector fluid control systems have utilized computer simulations of collector and piping dynamics to evaluate stability and response characteristics. To obtain reasonable simulation accuracy requires substantial computer memory and time and is well beyond the capability of small, desk-top computers. This paper derives a linearized steady-state frequency response for parabolic trough collectors and for connecting piping, which can be used in standard gain-phase analyses to evaluate system stability and closed loop frequency response. The frequency response characteristics of a typical collector string and piping are used in a gain-phase analysis to get some insight into the effect on system stability of various system parameters such as controller gain, sensor and controller time constants, and sensor location.

Hot gas control system design and vortex valve tests

As part of a conceptual study and test program for fluidic hot gas chamber bleed control systems, analytical and experimental investigations were performed on a number of vortex valve design configurations. Subscale vortex valve models (0.63 cm nozzle diam) were tested with high pressure cold gas (GN 2 ) input as supply and control fluid, with flow rates up to, typically, 0.45 kg/s (1 lb/s) at pressures to approximately 17.5 MN/m2(2500 psi) resulting in maximum turn-down ratios of, typically, 4:1. During a second part (follow on) program, the geometry, of this vortex valve was scaled up. The selected system concept is based on the use of four pairs of back-to-back vortex valves with two opposing hot gas supply inlets to minimize erosion problems. The four valve pairs are connected to the rocket motor chamber (pole piece) by way of eight ducts; warm gas generators are provided as a control fluid source. A test fixture was designed and fabricated that contained one back-to-back pair of vortex valves, and tests were conducted with cold gas (GN 2 ), warm gas (TAL-8; 1460 K), and hot gas (FAE-7; 3600 K) as supply fluid, using cold gas (GN 2 or GHe), or liquid (freon or hexane) as control fluid. Test data confirmed that the same range of turn-down ratio values can be achieved for cold gas GN 2 control of GN 2 supply, and for Helium control of hot supply gas (TR=4:1) (FAE-7) with the larger size valves as that obtained earlier with subscale valve models. A maximum turn-down ratio of 9:1 was realized for He control of cold GN 2 . The selected vortex valve configuration had a chamber to nozzle radius ratio of 3:1 and was found to be effective in achieving rapid cutoff of the hot supply gas without significant erosion problems, with flow rates up to 135 kg/s (3 lb/s) and with supply pressures near 6.9 MN/m2(1000 psi). Over the range of mass flow and pressures tested with a variety of supply and control fluids, it was found that a momentum turn-down ratio (MTR)

A microcomputer-based fluid infusion system for the resuscitation of burn patients.

Fluid replacement therapy, essential in the treatment of burn patients, continues to be a difficult clinical responsibility. Inherent variability of individual patient response to conventional burn fluid formulas and the practical limitations involved in manually adjusting fluid infusion rates on a continuous basis combine to hamper proper fluid administration. A microcomputer-based fluid infusion, data acquisition, and control (FIDAC) system has been developed to optimize fluid volume restoration and maintenance in the clinical treatment of burn and trauma patients. The FIDAC system provides real-time measurement of infused fluid and urine output, the display and routine recording of fluid balance parameters, and closed-loop control of fluid resuscitation. The system has been evaluated through a series of animal tests and is currently in clinical use at the University of Utah Medical Center Intermountain Burn Unit.

Stimulator for producing small, heated aerosols

A stimulus delivery system developed for imitating the defensive sprays of arthropods is described. The stimulator employs a fluidic interface valve and a fluidic logic control system to deliver small (approximately 1 μl) droplets. The droplets may contain a suspension of fine particles when the substance of interest is not soluble in a suitable carrier. The temperature of the droplets can be regulated.

粘弾性管内の気体中の波動伝ぱ

In fluidic and pneumatic control systems, vinyl hoses and tubes made of rubber-like materiah have come to be widely used as transmission conduits. Therefore, any analysis of the dynamics of those systems must consider the effects of the transmission tubing. So far, most of the studies conducted on gases have been limited to rigid tubes. Those studies limited to a certain extent, are not expected to give an adequate description of the system dynamics. Therefore, in this research the propagation of small amplitude harmonic pressure waves through gas contained in an infinitely long, thin-walled, viscoelastic tube is analyzed when the effects of the gas viscosity and heat transfer are included while the tube is assumed to move in the radial and axial directions. Axially symmetric wave solutions are obtained for the linearized equations governing the motion of the fluid and the tube. The solution leads to a complicated equation, the so-called frequency equation, relating the propagation constant with the system parameters. Furthermore, this equation is simplified and two fundamental modes of propagation are obtained. One mode of motion has a phase velocity similar to the speed of sound in the tube; whereas, the other one has a phase velocity similar to the speed of sound in the gas. In this analysis the latter mode, which is defined as the first mode, is mainly discussed. The effect of the viscoelastic parameters of the tube materials on the dispersion of waves through the fluid is made clear for different viscoelastic models.

Laboratory and Clinical Evaluation of a New Volume Ventilator

A three phase laboratory and clinical evaluation of a new fluidically controlled volume ventilator (Ohio 550) was undertaken to determine if this more compact, less complex and less costly unit retained the multiple advantages which have been established for volume ventilators in the continuous ventilatory support of patients in respiratory failure. Inspired volume, peak pressure, and flow rates were continuously monitored while a "test lung" was ventilated with its "effective compliance" reduced, and ambulatory patients with varying degrees of obstructive and restrictive ventilatory impairment were ventilated with the 550 respirator. Since adequate tidal and minute volumes were achieved under these conditions of markedly altered breathing mechanics, ten patients in acute respiratory failure requiring mechanical ventilation were managed with the 550 respirator. Aside from the absence of a sighing device, not considered by the authors to be a major disadvantage, the mechanical characteristics, inspired oxygen control and alarm systems were judged satisfactory and compared favorably with the volume ventilators currently available. The fluidic control system is expected to enhance the reliability and minimize the maintenance required of this respirator.

Industrial Robots and Fluid Control Systems

With the word fluid we mean gases and liquids. With a fluid control system we mean a control system in which we use a fluid as the signal carrier. Those fluid control systems in which the fluid is not air or oil are few, at least in connection with industrial robots (IRb).

Liquid level control

A fully automatic low and high level fluidic control system for monitoring the levels of all kinds of fluids has been developed by the Air Power Division of Hunts Engineering of the Nuffield Estate, Poole, Dorset.

Automatic control system for dispensing precise amounts of finely divided solids

A device for automatic dispensing of precise amounts of finely divided solids has been developed. Precision is a function of dispensing time. Smaller than gram quantities may be dispensed at a rate of about 1/3 g/min with a precision corresponding to a weight range of about 0.001 g for a series. The process consists in moving the material with the effect of the vibratory motion of a miniature air-powered vibrator. Operation is automatically controlled by the electronic system of the weighing unit interfaced to the pneumatic dispensing device via a combination fluidic and pneumatic control system.