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I am integrating gyroscope values to get orientation data, but I have a few problems with my code.

When I move my IMU and make like 100 degrees, the IMU can detect the movement somewhat accurately. When I turn it back to its first place, it doesn't read 0. It reads something around 40 degrees which means a huge 40 degrees of error.

I'm not really sure of the reason for this problem. My best guess is my sampling of the IMU being too slow. In my code I also use an RF module and an SD card module which makes my code really slow. My code runs at a speed of 5 times a second (my MCU runs at 154MHz.) That is too slow for fast movements, I think.

Summary of the question is:

Is this error happening because of the slow sampling rate, or is it caused bysomething else? If it's because of slow sampling rate, how can I solve this problem and get 10s of datas from my IMU?

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    \$\begingroup\$ You will never fix this by sampling faster. You are integrating. So, as with all integrations there is that annoying "+C" at the end -- the unknown constant. In your case, you are finding that it is 40 degrees after that one integration process. Welcome to the real world. You'll need more sensors. \$\endgroup\$
    – jonk
    Aug 2, 2021 at 18:58
  • \$\begingroup\$ What do you mean by IMU? The IMU is a bunch of sensors calculated together by a fusion algorithm that outputs AHRS, but it could be also a mechanical device. Surely it is not made only of MEMS Gyro. \$\endgroup\$ Aug 2, 2021 at 22:14
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    \$\begingroup\$ 1 What integration scheme are you using ? 2 Are the forward rotation to 100 deg and the backward rotation to 0 deg at similar angular velocities ? 3 To see if drift /bias is the problem, keep the gyroscope still and see how much the angle drifts in a given duration of time. \$\endgroup\$
    – AJN
    Aug 3, 2021 at 13:06

2 Answers 2

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Get a 9dof imu. If you are stuck using only gyroscopes: I would check your documentation since IMUs generally have features to help you out. I personally would use an IMUs low pass filter since it has a very high sample rate and as long as you aren't moving too fast should have a better response. It is important to have a high sample rate so that you can ignore higher frequency noise that doesn't alter your position significantly. The MPU6050 datasheet says you should read at a bare minimum of 200Hz. So yes your sample rate is way, way too slow. You are going to get high frequency noise folding over to low frequency and causing a total mess.

Also, don't assume that your gyros have a zero mean gausian noise distribution. They probably have an offset you may have to correct.

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Gyroscopes have drift and error, to avoid this problem combine them with another sensor (like a magnetometer and feed the data into a kalman filter) to avoid the error with drift. OR get a 9dof sensor with sensor fusion.

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