Hi there, I need to correct aberrant IMU euler orientation values occurring secondary to Gimbal lock.

I essentially have half the signal oscillating around the 0 degree mark and the other half around the 360mark. As true values will never exceed 180, I thought I could correct the output by reassigning all values > 360 to their original value subtracting 360. I have tried

Array Variable = yaw
yaw(yaw>180)=yaw-360

But this doesn't work, any have any ideas to correct this in an elegant way?

Answer 1

[David Ding]

Hi Luckshman,

I understand that you are trying to limit your angle data to between 0 and 360 degrees. You may make use of the "mod" function to take all your data modulo 360. For example:

% raw data
>> x = randi(500, 10, 1)

x =

   346
   158
   344
   418
    10
   376
   495
   375
   141
   395

Corrected data by setting all angles > 360 to their corresponding values < 360:

 y = mod(x, 360)

y =

   346
   158
   344
    58
    10
    16
   135
    15
   141
    35

This is also more robust than subtraction by 360 because for example if an angle is > 720 (i.e. two revolutions), the angle can still be brought back accordingly to the value between 0 and 360.

More information about MATLAB's "mod" function can be found below:

https://www.mathworks.com/help/releases/R2017b/matlab/ref/mod.html

Best,

David

Answer 2

[James Tursa]

The code you were using was not working because the rhs yaw was not indexed. E.g., to correct this

yaw(yaw>180) = yaw(yaw>180) - 360;

Answer 3

[Luckshman Bavan]

Thank you James and David! Both responses were very clear and helpful.