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I am using a 3 axis gyroscope (Android device) to record angular velocities using a sensor data logger application.

When the device is placed stationary, the gyroscope recorded the following values:

  • X: 0.003
  • Y:0.00042
  • Z:0.0045

At an instantaneous time t.

If I resolve the vector components to find angular velocity using the below formula,

enter image description here

(Is this formula correct btw?)

The angular velocity of the device = sqrt(0.0000009+0.0000001764+0.00002025) =0.0046 rad/sec = 0.26 deg/sec

What is the reason that the device is calculating a rotational speed of 0.26 deg/sec even when the device is stationary?

The Earth's rotation rate is only 0.0041 deg/sec. What am I missing here? Is this a calculation mistake or is this due to the sensor noise?

I am aware that cheap sensors used in Android devices are susceptible to noise data.

What I wanted to know is:

  1. Do gyroscopes in general (fiber optic gyroscopes and MEMS gyroscopes) record the angular velocity of the Earth's rotation around its own axis?
  2. Do gyroscopes also record the angular velocity of the Earth's revolution around the sun?

If the angular velocity of the Earth's rotation and Earth's revolution around the sun is recorded by the gyroscope, what is the optimal method to remove it?

Update

  1. For the final project we are using fibre optic gyro scope to measure orientation of a ground vehicle, The above experiment was only for Proof of concept using MEMS IMU.

However I understand that due to difference in sensitivities of measurement and error factors in MEMS and Fibre optic gyroscopes these devices may or may not measure earth's rotational velocity (It is possible for fibre optic gyroscope to measure earth's rotational rate i.e., earth's angular velocity)

Goal

My end goal is to design a system which records the orientation of a car in 3D space for a time period of 24 hours using a fiber optic gyroscope,

However if fiber optic gyroscopes record earth's rotational rate velocities I am here to ask for the method of compensation of these velocity from my gyroscope readings. Since rotational velocity of earth is subjected to change in each axis of gyro to give different values w.r.t orientation of device on earth, what is the optimal method to remove earth's rotational velocity from gyroscope readings any literature/Research Papers recommendation for this specific topic will be helpful I am using integration for the recorded angular velocities to find the angular displacement in each axis.

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    $\begingroup$ I think the issue is that, being rate devices, they are often not sensitive enough for that use even though they theoretically detect them. Something like a gyrocompass is an absolute sensor so you can see the accumulated result of slow motions over time whereas a rate sensor just drowns out the slow motion in noise. $\endgroup$
    – DKNguyen
    Mar 14, 2023 at 13:46
  • $\begingroup$ I was using a MEMS gyroscope just for proof of concept, however I will be using a fibre optic gyroscope for the project, I have updated the question for more details related to the application, Kindly go through it one more time. $\endgroup$ Mar 15, 2023 at 5:58
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    $\begingroup$ you have clearly forgotten zeroing, experimental set up is no joke: When something seems wrong with your measurement, 99% chance you have made a mistake in the set up. When something seems right with your measurement, 80% you have still made a mistake in the set up. $\endgroup$
    – Jonathan
    Mar 15, 2023 at 10:38
  • $\begingroup$ With the update for your end goal, this is essentially a dead-reckoning application. If you aren't a nuclear submarine operating in the deep sea completely blind to navitational inputs other than inertial, you don't need to limit yourself to relying only on a gyro. Indeed, even a run of the mill fiber optic gyro is likely to be insufficient. $\endgroup$
    – DKNguyen
    Mar 15, 2023 at 18:00

1 Answer 1

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Gyroscopes, like every sensors and every measuring instruments, need before usage a step of calibration.

If your device is properly stationary, then what you are measuring here is your reference. every further measurements will have to be substracted by these values.

Do not forget to also check the error margin provided by the fabricant, so you you are clear with the precision of your measurements.

Note: In general measuring devices, are (roughly) pre-calibrated in the factory. The factory which is most likely on earth then also rotating. This means what you are measuring here is definitely not earth rotation, just device variation.

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