Fluidics
Encyclopedia
Fluidics or Fluidic logic is the use of a fluid
to perform analog
or digital
operations similar to those performed with electronics
.
The physical basis of fluidics is pneumatics
and hydraulics
, based on the theoretical foundation of fluid dynamics
. The term Fluidics is normally used when devices have no moving parts
, so ordinary hydraulic components such as hydraulic cylinder
s and spool valves are not considered or referred to as fluidic devices. The 1960s saw the application of fluidics to sophisticated control system
s, with the introduction of the fluidic amplifier.
A jet of fluid can be deflected by a weaker jet striking it at the side. This provides nonlinear
amplification
, similar to the transistor
used in electronic digital logic. It is used mostly in environments where electronic digital logic would be unreliable, as in systems exposed to high levels of electromagnetic interference
or ionizing radiation
.
Nanotechnology
considers fluidics as one of its instruments. In this domain, effects such as fluid-solid and fluid-fluid interface forces are often highly significant. Fluidics have also been used for military applications.
The basic concept of the fluidic amplifier is shown here. A fluid supply, which may be air, water, or hydraulic fluid
, enters at the bottom. Pressure applied to the control ports C1 or C2 deflects the stream, so that it exits via either port O1 or O2. The stream entering the control ports may be much weaker than the stream being deflected, so the device has gain
.
Given this basic device, flip flops
and other fluidic logic elements can be constructed. Simple systems of digital logic can thus be built.
Fluidic amplifiers typically have bandwidths in the low kilohertz range, so systems built from them are quite slow compared to electronic devices.
is an amplification
device that uses a fluid
to convey the signal.
Although much studied in the laboratory they have few practical applications. Many expect them to be key elements of nanotechnology
.
Fluidic triodes were used as the final stage in the main Public Address system at the 1964 New York World's Fair
.
s. As digital logic has become more accepted in industrial control, the role of fluidics in industrial control has declined.
to control direction, in two ways: circulation control and thrust vectoring. In both, larger more complex mechanical parts are replaced by fluidic systems, in which larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles.
In circulation control, near the trailing edges of wings, aircraft flight control systems such as aileron
s, elevators
, elevon
s, flap
s and flaperon
s are replaced by slots which emit fluid flows.
In thrust vectoring
, in jet engine
nozzles, swiveling parts are replaced by slots which inject fluid flows into jets. Such systems divert thrust via fluid effects. Tests show that air forced into a jet engine exhaust stream can deflect thrust up to 15 degrees.
In such uses, fluidics is desirable for lower: mass, cost (up to 50% less), drag (up to 15% less during use), inertia
(for faster, stronger control response), complexity (mechanically simpler, fewer or no moving parts or surfaces, less maintenance), and radar cross section
for stealth
. This will likely be used in many unmanned aerial vehicle
s (UAVs), 6th generation fighter aircraft
, and ship
s.
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
to perform analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
or digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
operations similar to those performed with electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
.
The physical basis of fluidics is pneumatics
Pneumatics
Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...
and hydraulics
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...
, based on the theoretical foundation of fluid dynamics
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
. The term Fluidics is normally used when devices have no moving parts
Moving parts
The moving parts of a machine are those parts of it that move. Machines comprise both moving and fixed parts. The moving parts have controlled and constrained motions....
, so ordinary hydraulic components such as hydraulic cylinder
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
s and spool valves are not considered or referred to as fluidic devices. The 1960s saw the application of fluidics to sophisticated control system
Control system
A control system is a device, or set of devices to manage, command, direct or regulate the behavior of other devices or system.There are two common classes of control systems, with many variations and combinations: logic or sequential controls, and feedback or linear controls...
s, with the introduction of the fluidic amplifier.
A jet of fluid can be deflected by a weaker jet striking it at the side. This provides nonlinear
Nonlinearity
In mathematics, a nonlinear system is one that does not satisfy the superposition principle, or one whose output is not directly proportional to its input; a linear system fulfills these conditions. In other words, a nonlinear system is any problem where the variable to be solved for cannot be...
amplification
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
, similar to the transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
used in electronic digital logic. It is used mostly in environments where electronic digital logic would be unreliable, as in systems exposed to high levels of electromagnetic interference
Electromagnetic interference
Electromagnetic interference is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit...
or ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
.
Nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
considers fluidics as one of its instruments. In this domain, effects such as fluid-solid and fluid-fluid interface forces are often highly significant. Fluidics have also been used for military applications.
Amplifier
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...
, enters at the bottom. Pressure applied to the control ports C1 or C2 deflects the stream, so that it exits via either port O1 or O2. The stream entering the control ports may be much weaker than the stream being deflected, so the device has gain
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
.
Given this basic device, flip flops
Flip-flop (electronics)
In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic...
and other fluidic logic elements can be constructed. Simple systems of digital logic can thus be built.
Fluidic amplifiers typically have bandwidths in the low kilohertz range, so systems built from them are quite slow compared to electronic devices.
Triode
The fluidic triodeTriode
A triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electronic amplification device...
is an amplification
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
device that uses a fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
to convey the signal.
Although much studied in the laboratory they have few practical applications. Many expect them to be key elements of nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
.
Fluidic triodes were used as the final stage in the main Public Address system at the 1964 New York World's Fair
1964 New York World's Fair
The 1964/1965 New York World's Fair was the third major world's fair to be held in New York City. Hailing itself as a "universal and international" exposition, the fair's theme was "Peace Through Understanding," dedicated to "Man's Achievement on a Shrinking Globe in an Expanding Universe";...
.
The Fluidic Triode was invented in 1962 by Murray O. Meetze, Jr., a high school student in Heath Springs, S.C. He also built a fluid diode, a fluid oscillator and a variety of hydraulic "circuits," including one that has no electronic counterpart. As a result he was invited to the National Science Fair, held this year at the Seattle Century 21 Exposition. There his project won an award.
Logic elements
Logic gates can be built that use water instead of electricity to power the gating function. These are reliant on being positioned in one orientation to perform correctly. An OR gate is simply two pipes being merged, a NOT gate consists of "A" deflecting a supply stream to produce Ā. An inverter could also be implemented with the XOR gate, as A XOR 1 = Ā.Uses
Fluidic components appear in some hydraulic and pneumatic systems, including some automotive automatic transmissionAutomatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...
s. As digital logic has become more accepted in industrial control, the role of fluidics in industrial control has declined.
Research
Fluidic injection is being researched for use in aircraftAircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
to control direction, in two ways: circulation control and thrust vectoring. In both, larger more complex mechanical parts are replaced by fluidic systems, in which larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles.
In circulation control, near the trailing edges of wings, aircraft flight control systems such as aileron
Aileron
Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...
s, elevators
Elevator (aircraft)
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...
, elevon
Elevon
Elevons are aircraft control surfaces that combine the functions of the elevator and the aileron , hence the name. They are frequently used on tailless aircraft such as flying wings. An elevon that is not part of the main wing, but instead is a separate tail surface, is a stabilator...
s, flap
Flap (aircraft)
Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed an aircraft can be safely flown at and to increase the angle of descent for landing without increasing air speed. They shorten takeoff and landing distances as well as...
s and flaperon
Flaperon
A flaperon is a type of aircraft control surface that combines aspects of both flaps and ailerons. In addition to controlling the roll or bank of an aircraft as do conventional ailerons, both flaperons can be lowered together to function similarly to a dedicated set of flaps...
s are replaced by slots which emit fluid flows.
In thrust vectoring
Thrust vectoring
Thrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....
, in jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
nozzles, swiveling parts are replaced by slots which inject fluid flows into jets. Such systems divert thrust via fluid effects. Tests show that air forced into a jet engine exhaust stream can deflect thrust up to 15 degrees.
In such uses, fluidics is desirable for lower: mass, cost (up to 50% less), drag (up to 15% less during use), inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
(for faster, stronger control response), complexity (mechanically simpler, fewer or no moving parts or surfaces, less maintenance), and radar cross section
Radar cross section
Radar cross section is a measure of how detectable an object is with a radar. A larger RCS indicates that an object is more easily detected.An object reflects a limited amount of radar energy...
for stealth
Stealth technology
Stealth technology also termed LO technology is a sub-discipline of military tactics and passive electronic countermeasures, which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, to make them less visible to radar, infrared, sonar and other detection...
. This will likely be used in many unmanned aerial vehicle
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...
s (UAVs), 6th generation fighter aircraft
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
, and ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
s.
External links
- A four-bit Adder made using fluidic logic
- Latest news on Fluidics www.fluidics.eu
- Scanned article available online from Google Books: Popular Science June 1967, Fluidics: How They've Taught A Stream of Air to Think Pp. 118-121,196.197, illustrating several switch designs and discussing applications