The fruit flies (also known as Drosophila) are often used as research subjects in the field of genetics. Not so the flies of the CalTech University (California) research team - these are a model for aviation research.
By: Maya Givon
The fruit flies (also known as Drosophila) are often used as research subjects in the field of genetics. Not so the flies of the CalTech University (California) research team - these are a model for aviation research.
In a study recently published in the journal Proceedings of the National Academy of Science, new insights are published regarding the flies' ability to maintain a constant speed relative to the ground, even in conditions of variable wind. The prevailing view attributes to the complex eyes of the flies - as well as other flying insects - the key role in spatial orientation, and therefore also in the control and control of flight, including maintaining a constant speed and adjusting the speed to the wind resistance. However, recent experiments have produced surprising findings.
The flies at Cal Tech Laboratories in California were placed in a wind tunnel, and were photographed at any given time by five cameras, and from different angles. The cameras fed the data to a computer whose job was to analyze the flies' movement (direction, speed, acceleration, etc.). When they were exposed to bursts of fast wind, at a speed of half a meter per second, they demonstrated the opposite behavior than expected: at the first moment, they accelerated when the wind emerged behind them, or slowed down if the wind came in front of them. Immediately after that, their movement was corrected and they returned to a constant and controlled speed.
The team of researchers believed that the calculation power required by the visual system is extremely large and therefore relatively slow - and wondered if there is an additional sensor that compensates for the delay in the response of the visual system. The solution was discovered in the flies' tentacles. In another experiment, flies with their tentacles removed still accelerated with the direction of the wind, but showed an inability to return and maintain a constant speed relative to the ground.
To examine the role of the visual system separately, the team designed an experiment in which an animation was projected onto the walls of the wind tunnel at a speed that was supposed to trick the flies into thinking there was no change in wind speed. In this experiment as well, the flies responded with a sudden change in acceleration with the direction of the wind - but were unable to return to a constant speed.
From this, the researchers concluded that the wind sensors on the flies' tentacles are responsible for sensing and quickly responding to changes in wind speed, while the information received from the delayed vision system helps them return to a constant speed and maintain it over time. There is actually a mechanism of compensation and savings here: instead of relying only on the "expensive" and slow system of vision, the responsibility for the function was split to another - simpler and much "cheaper" sensor, which is located on the tentacles and provides a specific and quick response to a limited need.
This model may be an inspiration for the construction of small flying robots, even in which maintaining a constant speed is a challenge that requires sensors, some of which require large computing power and slows down the activity. Using an additional simple sensor to calculate this function may solve the problem.
More on the same topic on the science website:
14 תגובות
ls
So a few more small fixes.
There are several speeds in the plane. What you see on the speedometer is IAS, i.e. displayed airspeed. Some planes have a table on the side for calibration, CAS, and this is the calibrated speed. It's less interesting in new planes. The IAS is the speed that matters for flight characteristics, and it does depend directly on the air density. There is also TAS, which is the real speed of the plane and is hardly interesting. To calculate TAS you need an external temperature. There is a Mach number, since it is interesting for example, in optimal climbing. For example, I'm used to climbing like this: maintain an instrument speed of 350 knots up to Mach 0.90 and then maintain a constant Mach.
There is also EAS, which corrects for the air density and not the temperature, but this is of no interest to the pilot. And there is ground speed which is important for navigation.
ISA is international and is of interest in commercial flights. Above a certain height, you switch to the QNE height, which is based on ISA.
At takeoff you don't need to ask for QNH, you simply calibrate the field height on the watch. You get a QNH altitude from the tower when you join the landing, because the altitudes of the pattern are based on this altitude.
And about the fly, I completely agree.
The ro, the air density disappeared for me in response. Mine should be added to the dynamic pressure and the gas equation.
Have a nice flight.
Miracles,
Thanks for the presentation. Enlightening and interesting.
But let's continue to be precise.
third. You are underestimating the value of the pitot tube. Allow me to defend his dignity. Even at the price of a hassle.
A pitot tube by its very nature takes air density and temperature into account since the pressure is RsT ῥ = P, meaning the air density (which changes with altitude and depending on the temperature on that day) times the specific gas constant, times the temperature [K].
Furthermore, EAS and CAS are speeds corrected by the square root of the air density ratio at ground level divided by the air density at flight level.
And also ultimately derives the speed from the dynamic pressure v^2ῥ = 2Pd , as you mentioned. (The formulas don't come out well in Talkback)
Why is all this important, those who plan a flight that requires a two-digit number of hours and repeat fuel bingo need to understand what their most effective speed is for the range under the conditions of that day and not European ISA conditions.
But there are pilots who can refuel in the air and don't have to fly on the edge and look for NCA all the way :).
The differences between static pressure nozzles that are spread around the pitot can also give information about the slip angle and the angle of attack.
What's more, before takeoff, QNH pressure is requested from the air traffic controller to "correct" the barometric altitude that is reported again... Fito, so that everyone in the airspace flies at the same pressure altitude.
After the light surfing we will return to Zvob. It seems to me that the functions of detecting CAS speed changes and glide angle are performed by the fly using the tentacles.
Altitude control is carried out by reference to horizontal contours in the environment and less so by maintaining an angular rate of movement above the ground. Here is a video that shows it.
https://www.youtube.com/watch?v=P4FDRqz3f0k
In a moment we will also get to the control of rate changes (probably not there) and acceleration (there is, the accelerometer behind the wing).
d. Contrary to an airplane, flow interruptions are probably less disturbing to flies because the viscosity plays a dominant role (low Reynolds number) in the flapping rates of the wings and such a wing size. It seems that the fly, according to some videos I found on the net, does not rely at all on bending the wing in order to produce lift like airplanes or birds, but rather produces a leading edge vortex. See the TED video from minute 3:00
https://www.youtube.com/watch?v=e_44G-kE8lE
God. Of course you are correct in the definition, I meant that in the end the fly directs the lift vector to provide it with both thrust and lift, positive or negative. And shoes, I'm a married man and I've seen shoes fly mostly in my direction.
and. Stability - you mean the flight control, and I mean the static or dynamic stability margin.
G. I'm not sure from the videos, but there seems to be an up and down flapping flight mode somewhat similar to a bird, and a flapping and reverse flapping flight mode. One is used for fast forward progress and the other for hovering and maneuvering. Maybe the sample rate in the videos is not fast enough and both are the same…
H. And I think this is the crux of the matter, so how does a fly's flight control work?
Advanced control controls six degrees of freedom - three linear and three angular directions. In each axis, State is controlled, Rate is a derivative of State, Acceleration is a second derivative of State. The Mahedrin also add Jerk & Snap, a fourth and fifth derivative respectively, which for all kinds of reasons is excellent for sharp maneuvers and sharp gusts.
Who knows how to control a fly without gyro systems, without FOG, LRG, MEMS, VGU or RGU, GPS and other technological aids.
Angular position, ground speed and height controlled by vision
Angular rate, apparently there is no control
Angular acceleration using the halters behind the wings
and relative linear acceleration using hypotheses about the tentacles.
And this he performs at approximately a sampling rate of 200 Hz, times per second, 5 milliseconds between samples, with a mind of negligible weight. impressive.
Asaf
I understand that you know more than the experts in the field do.
I don't think you understood the article...
You really discovered that the tentacles help during flight. Maybe if the respected scientists read studies they would find out that they already knew about it more than 100 years ago. For example, the most well-known organ in the sensor that measures speed is called Johnston's organ.
ls
There is a nice explanation for the flight of insects here - http://web.neurobio.arizona.edu/gronenberg/nrsc581/powerpoint%20pdfs/flight.pdf
ls
Let's be precise…
c) A pitot tube is used exclusively to measure total pressure. In addition, there are static openings for measuring static pressure - and the difference between them is the dynamic pressure. The dynamic pressure gives the instrument airspeed (IAS or CAS). With the help of a temperature gauge (which was not part of the Pitot system) it is possible to calculate real air speed. There is no way to know what the wind is like in the plane - except with the help of an inertial navigation system (and/or GPS).
What's more - the lift - in a fixed wing plane only - depends on the instrument speed, not the real speed and certainly not the ground speed (the one that takes into account the wind).
d) What you say here is not so true. The movement of the wings provides both lift and thrust. Therefore, the wings do not try to find an optimal angle of attack - they try to move the fly where it wants. In general, the aerodynamics in insect flight are very different from the aerodynamics of airplanes. The whole issue of vortices there is more influential, for example, because of the low flight speed (and even backward flight).
e) The angle of attack is the angle between the wing chord and the momentary airflow. No standing and no shoes...
f) Regarding the stability - the fly has a completely different patent - gyroscopic stabilizers. It is similar to what the small helicopters that are sold in toy stores have. I personally flew for many years on an unstable plane at all... according to you, this is not possible?
g) You say different flight modes. Different from what? It does not have any mode of flight at a constant angle of attack.
h) It is true what you say, but a helicopter is very different from a propeller. In addition to the normal rotation of the blade - the blade rotates around its longitudinal axis, rises and falls, moves forward and backward (for example in a storm) and even bends continuously.
15) Hooting horn... you are right (my age shows here 🙂 ). In the F16 there is a beep for a high angle of attack (and a high rate of rotation), and in the FXNUMX there is no sound warning for the angle of attack. I guess you're right about civil aviation, I really have no idea.
Nissim and Benjamin,
At least according to the information in the article -
A. The test scenario included straight and horizontal flight in a wind tunnel.
B. Even maneuvers that are not straight and horizontal require maintaining the wing's angle of attack limits, so the test is more complex, but essentially the same.
third. In the plane, the pitot tube is used to measure the air speed and "clean" the effects of the wind (and also the ambient pressure, as well as the air density and temperature), the fly probably uses the change of the air flow on the tentacle to perform the same function.
d. The movement of the fly's wings, as well as birds in this type of flight, as a whole tries to preserve the angle of attack that is suitable for flight. In flight traffic that maintains an optimal thrust-to-drag ratio (L/D_max). In sharp maneuvers the movement of the wing may result in a maximum possible angle of attack (Alpha_max) even if the relative drag is higher and wastes more energy.
God. Angle of attack is a vector of the flow in the direction of flight and perpendicular to the flight. It can be maintained by moving forward at a fixed angle of an airplane wing or by moving up and down during the forward or backward movement of a fly wing.
and. The issue of stability is complex. Basically, in a fixed-wing aircraft, stability is achieved by the fact that the center of gravity is in front (toward the nose) of the center of pressure of the wing (the point on which the lift is equivalent), or more precisely the neutral point, for whom it is critical. In a given aircraft, to increase stability, weight is sometimes added in advance by weights at the surface level, or moving components in the aircraft at the design level. It is possible that the fly works in reverse and moves (closer to) the neutral point to the center of gravity to make it less "stable" and thus facilitate sharp maneuvers, but again this is not implied from the test description.
In the hovering of the fly it is clear that the reversal of the flapping of the wing is what allows the fly to stabilize at one point.
G. The fly has other modes of flight that have not been tested here, as far as I understand, such as flipping a wing and catching the vortices of its own wingtips, but that is outside the topic of the discussion.
H. A helicopter, or any propeller for that matter, uses the revolving wing principle. Like an airplane wing, but with variable speed along the pole, so the installation angle also gets smaller from the center and outwards. Less relevant to our case.
ninth. In today's airplanes, "stall horns" are disappearing, but there is a pleasant female voice that announces "Stall" or "Stall escape" if allowed.
Benjamin May
exactly.
to Is
It seems to me that the fly stabilizes itself through a complex wing movement
which is the main variable factor in the speed of air flow on
The wings and the angle of attack and not the speed regulation of the fly
himself (which is in essence what Nissim wrote, if I understood correctly..).
ls
I think not exactly. Unlike an airplane, the wings of a fly are in motion (similar to a helicopter). A fly can also fly backwards. Apart from that, I have not yet seen a fly fly straight and horizontally 🙂
I wrote not exactly, because a helicopter can also stall (although in the case of a helicopter, the stall happens at high speed). That is - it is possible that there will be a situation of standing up due to a sudden gust.
I also don't think that the fly says to itself - "Well, I hear a stinging horn, I need to take it down immediately so as not to sting!". It's like we don't think about balance when we move our arms while walking or running.
Not related to the escape. The fly tries to maintain a constant airspeed like any plane in a straight and horizontal flight in order not to stall. When the gust in the direction of flight the fly will increase speed otherwise the angle of attack of the wing will increase until the flow is cut off and free fall. And vice versa in the direction of an opposite wind.
It is likely a survival reflex
which causes the flies to speed up or slow down (in the opposite way
to the strength of the wind) first with a sudden gust of wind
to get away from a madman (or a hand that might crush them)
And only then stabilize their speed.
Mr. Dobi Binyamini, developed a flying robot, whose model is the butterfly. The advantage of the butterfly is in utilizing energy in an efficient and economical way.