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I need to measure the angular variation of a helicopter. Hence, I am looking for a 3-axis gyroscope? However, what kind of specification the gyroscope should have, like sample rate etc? Therefore, I want to know how the angular velocity changes (in any axis) in helicopter. I need to know the range only.

Any reference would be highly appreciated.

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  • $\begingroup$ Angular displacement due to flight manoeuvres? $\endgroup$ – Koyovis Jan 24 '18 at 0:22
  • $\begingroup$ @Koyovis yes, in addition while moving in land in wheels etc. $\endgroup$ – Creator Jan 24 '18 at 0:32
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3-DoF magnetic gyroscopes are a dime a dozen nowadays, together with 3-DoF accelerometers, magnetic field sensors, and GPS position transducers. These are in mobile phones now, tiny and frugal with electricity. A google search for "9-dof position acceleration gyroscope" results in a lot of options.

For the sampling rate: this needs to be at least twice the frequency of the fastest vibration - more is better, since a frequency at half the sampling rate shows up as a triangular wave.

from the linked site

For the frequency range of angular displacement, this article might be of interest. It shows vibration data of a car driving over the road, using an iPhone to measure the vibrations. The article mentions a sprung frequency (inside the vehicle) of 1 - 5 Hz. A helicopter usually has higher inertia than a car, so sprung frequency should be lower. If you take 0 - 10 Hz as a baseline for the range, you should be safe. The ground reaction angular frequency range is always higher than the airborne one: responses in the hover are measured in seconds, not in Hz.

enter image description here

Above graph shows pitch response of an example helicopter, from Prouty, Helicopter Performance, Stability and Control. A helicopter with a rotor mounted on top is unstable in the hover, but in order to still be controllable for human pilots the response frequency may not be too high - it turns out that humans can comfortably control instabilities with a time period in the order of around 10 sec. The military have requirements for the stability response in MIL-H-8501A

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  • $\begingroup$ "The ground reaction angular frequency range is always higher than the airborne one." Is there any reference or insight to it? This is the most important insights I was looking for. $\endgroup$ – Creator Jan 24 '18 at 1:52
  • $\begingroup$ Yes you're right, that is a bit of a sweeping statement. Have expanded the answer. $\endgroup$ – Koyovis Jan 24 '18 at 2:50

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