Gyro Mechanism ??

[Texas Buzzard]

I have just purchased two small Esky gyros.

My flying buddy said I have to leave them out in the light.
I once heard gyros we ue use the earth's magnetic field. They are sesitive to
a magnetic field, and there is no moveing part in a modeling gyro.

Please talk to me and enlighten me about how it works. THANKS.

[JetPlaneFlyer]

They sense acceleration. Older ones used to have mechanical components but I believe newer types are all electronic.
They certainly don’t have to be in the light to work :rolleyes: .. and they don’t use the earths magnetic field.
I’ve never used one but I'd guess location and orientation are quite critical so they can detect acceleration in the plane you want them to work in.. for instance in yaw.. I'd assume the instructions provided with the gyro give some guidance?

Steve

[Andrew McGregor]

They sense rotation internally, by a change in the dynamics of some internal structure. No light, no magnetic field, it's all inertial.

I can't be more specific because there are many different kinds... but for one example, try getting hold of a musician's tuning fork, setting it ringing and then waving it around. You should find it changes pitch if you rotate it in one direction, but not any other. That's the basis of one kind of gyro.

ESky gyros have the particular property that they are temperature dependant, and need a little time to warm up before they'll trim correctly.

[Texas Buzzard]

Good words from Andrew and JetPlane Flier,
Thanks guys.

Since the entire Esky gyro is small, the housing id only ~ 1,2" dia.
That little animal inside has to be very small.

Since the detect a change in acceleration and that means it could also detect a CHANGE in inertia too - I am accepting both of the above comments. I think you 2 are saying the same thing

In my Dinged Out Mind - I can picture a tiny ball bearing "floating" right inthe center of some very squeezable materiel. This squeezable stuff id in a tube.
In a tube because the gyro detects changes in plans attitude in just one axis - assuming you are looking at one gyro acting on the elevator servo.

I am anxious to try these little jewels out on ailerons and rudder on a fairly manuverable electric of 2 pounds and 48"w.s. Then later put them in my X-country ship.

Thanks men.

[JetPlaneFlyer]

The ball moving around in a 'squeezable' material is a reasonable anology of how they work... The actual technology is i believe Piezoelectric: http://en.wikipedia.org/wiki/Piezoelectric_sensor

Steve

[vintage1]

I believe they are not gyros at all: They are accelerometers. Piezo or ceramic.

There must be some fancy circuitry to integrate out acceleration*time integrals, and produce (or modify) servo output until those sum to zero.

I've always wanted to play with one. But helicopters bore me.

[kcaldwel]

Since the detect a change in acceleration and that means it could also detect a CHANGE in inertia too

Since inertia is a property of matter, I doubt they are detecting changes in inertia.

Many of the modern RC gyros are MEMS (Micro Electric-Mechanical System), not piezo:

http://www.rchelisite.com/how_do_gyros_work.php

Kevin

[MCarlton]

I've always wanted to play with one. But helicopters bore me.

Do I remember rightly that your Pushy Cat (?) had some issues, perhaps a gyro on rudder / elevator may tame some of those issues?

I don't KNOW, but I was just thinking of a practical application :)

[mnowell129]

They are typically vibrating beam or vibrating tuning forks at the mems level. When yawed, Coriolis forces cause a bending moment in the orthogonal axis which is then sensed.
Some of the JR's use a silicon ring sensor (also mems) that is flexing and when rotated Coriolis forces make the flexing change modes off axis which is then sensed.
They are fun to play with, I put a simple rate gyro on the rudder of a foamy and it would axial roll all day long with no rudder input and would fly knife edge with no rudder input. It was too easy. Used on a rudder it makes hovering a no brainer.

[Andrew McGregor]

I believe they are not gyros at all: They are accelerometers. Piezo or ceramic.

There must be some fancy circuitry to integrate out acceleration*time integrals, and produce (or modify) servo output until those sum to zero.

I've always wanted to play with one. But helicopters bore me.

They're angular accelerometers, yes. Most of the electronics is digital...

The process is something like: run the raw output of the sensor through a temperature correction, then a Kalman filter to estimate the aircraft's heading or angular rate, compare that with the target established by similarly Kalman filtering the signal from the RX, then drive the servo (through a fairly complicated algorithm itself) to try to correct.

A Kalman filter is roughly like an integral, except it remains numerically stable in the presence of noise, measurement error, and finite-precision math.

[vintage1]

Right. With the Kalman filter, but why bother with making them vibrate?

Is it just easier to detect a frequency change than a DC potential?

[Andrew McGregor]

A tuning fork doesn't actually sense rotation if it isn't vibrating... it's a second order effect on the dynamics of the fork ringing.

However, you're right about it being easier to sense frequency than DC potential or still worse very small currents. Some of the other kinds wouldn't need to vibrate, except for that.

[Texas Buzzard]

I believe they are not gyros at all: They are accelerometers. Piezo or ceramic.

There must be some fancy circuitry to integrate out acceleration*time integrals, and produce (or modify) servo output until those sum to zero.

I've always wanted to play with one. But helicopters bore me.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>o0o<<<<<<<<<<<<<<<<<<<<<

I do not get close to helecopters. Don't like Copters. The use of gyros will be in semi-3-D airplanes. I have been watching the evolution of Gyro use in Dave Powers videos ( he has 66 vids up) Find him at RCPowers.com
The video that shows the latest testa of a VTOL F-35 can be found at
<http://www.youtube.com/profile?user=RCSuperPowers&view=videos&start=20&sort=v> copy & paste please.
Then click page two - on the bottom and look Left for the F-35. It is amazing how gyros allow him to fly an unstable plane. He's been working with gyros in big parkjets for over two yers. Great site!

[Andrew McGregor]

Ok, well, in terms of knowing about the practicalities of using gyros... all the experience is with helis. But don't worry, heli pilots don't bite (our aircraft, on the other hand, can... so you can at least be sure that the gyros are pretty reliable).

So, gyros come in three kinds.

First are rate gyros, they sense angular rate and try to make it what rate you command with the stick. Second are heading hold gyros, they integrate the angular rate to get an attitude estimate, and let you control the attitude target with the stick. The difference is that a heading hold gyro will return to assigned attitude if the aircraft is disturbed, whereas a rate gyro will resist the disturbance but not return if displaced. In most cases you want rate gyros on planes because HH gyros make the handling extremely unnatural.

The third kind are 'cyclic gyros', intended to electronically replace the flybar on a helicopter. Unlike the other two, they have two or three axes of measurement, both pitch and roll, sometimes yaw as well, and use a mixture of both rate and heading hold behaviour. You could use one of these to stabilise a plane, and they'd be good for a VTOL like the F35. Some kinds have extra sensors to allow auto-hover (basically a camera that looks at the ground like an optical mouse)... that might even work on a VTOL.

[pmackenzie]

Right. With the Kalman filter, but why bother with making them vibrate?

Is it just easier to detect a frequency change than a DC potential?

mnowell had the correct description.

If you picture the crystal as a cantilevered beam, when it vibrates it is actually rotating about the fixed end with each vibration. With out this vibration/rotation they can't measure pure yaw.
Because of the way that they are vibrating and the way they measure the deflections that occur (both direction of measurement and filtering only for the same frequency they vibrate at) they don't measure acceleration at all, only yaw rate in a single axis.

Pat MacKenzie

[pmackenzie]

Some more info:

http://www.xbow.com/support/Support_pdf_files/RateSensorAppNote.pdf
http://www.nec-tokin.com/english/product/piezodevice2/ceramicgyro.html

Pat MacKenzie

[pmackenzie]

.

Since the detect a change in acceleration and that means it could also detect a CHANGE in inertia too - I am accepting both of the above comments. I think you 2 are saying the same thing

Minor point - "inertia" does not change. It is a property of matter and has no units.
Momentum does have units, but not inertia.

Pat MacKenzie

[mnowell129]

With out this vibration/rotation they can't measure pure yaw.

Correct. You could measure acceleration with a spring loaded beam, but this would also measure a translation and would provide any output once at steady state. The vibrating beams measure yaw rate. The heading hold models integrate the yaw rate to get position.