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resources:eval:user-guides:inertial-mems:imu-overview [21 Jul 2021 01:23] – [Bias Error] Chas Frickresources:eval:user-guides:inertial-mems:imu-overview [31 Aug 2021 22:00] (current) – [Linear Acceleration Effect (Linear-g), Linear Acceleration Effect on Bias, Linear-g Rejection (Linear-g Sensitivity)] Chas Frick
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 This can be thought of as the sensor resolution in an "ideal case." It is also found as the minimum of the AVAR plot. This can be thought of as the sensor resolution in an "ideal case." It is also found as the minimum of the AVAR plot.
  
-====== Angular Random Walk (ARW) ====== +====== Angle Random Walk (ARW) ====== 
-Applies to gyroscopes. It is the "close-in" (small τ) on the AVAR curve and is noise that comes from the quantization process. Taken at Τ = 1 second.+Measured in °/hour/√Hz or °/√hour.
  
-====== (Angular) Rate Random Walk (ARRW) ======+Applies to gyroscopes. It is the "close-in" (small τ) on the AVAR curve and is noise that comes from the quantization process. Taken at Τ = 1 second. In order to calculate the ARW, take the value of the square-root of the AllanVariance and divide by 60 [iMAR]. 
 + 
 +For an example consider the ADIS16153, with datasheet here: [[adi>media/en/technical-documentation/data-sheets/ADIS16135.pdf#Page=08]]. The graph of the AllanVariance is this:  
 +{{ :resources:eval:user-guides:inertial-mems:2021-07-22_09_29_19-adis16135_rev._f_.png |}} 
 + 
 + 
 + 
 + 
 +Additional notes: [[http://home.engineering.iastate.edu/~shermanp/AERE432/lectures/Rate%20Gyros/Rate%20Gyro%20Explanations.pdf|iMAR Research Background]] 
 + 
 + 
 +====== Rate Random Walk (ARRW) ======
 Applies to gyroscopes and is the "far out" (large Τ) on the Allan Variance (AVAR) curve. Applies to gyroscopes and is the "far out" (large Τ) on the Allan Variance (AVAR) curve.
 This quantity represents long-term stability of the sensor measurement. This quantity represents long-term stability of the sensor measurement.
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 Can be approximated with the formula: ND ≅ ARW/60* √2 Can be approximated with the formula: ND ≅ ARW/60* √2
  
-====== Linear Acceleration Effect (Linear-g) ====== 
-Measured in degrees/sec/g.  
  
 ====== Vibration Rectification Error (VRE) ====== ====== Vibration Rectification Error (VRE) ======
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 ====== Cross-Axis Sensitivity ====== ====== Cross-Axis Sensitivity ======
-Unintended effect where rotation/acceleration from one axis is detected on another axis+Unintended effect where rotation/acceleration from one axis is detected on another axis. 
 +Can be calculated from axis to axis misalignment error for accels/gyros: sin(axis to axis misalignment) in % 
 + 
 +Example: For the ADIS16448, the accel axis to axis misalignment is 0.2 degrees. Therefore Cross-axis sensitivity accel is sin(0.2) = 0.197%. Gyro is sin(0.05) = 0.09%. Magnetometer: sin(0.25) = 0.247% 
 + 
 +====== Linear Acceleration Effect (Linear-g), Linear Acceleration Effect on Bias, Linear-g Rejection (Linear-g Sensitivity) ====== 
 +Unintended effect where linear acceleration is detected as rotation. Measured in degrees/sec/g.  
 + 
 +====== Vibration Rejection (Gyros) ====== 
 +A combination of Linear-g and Vibration Rectification (VRE) specs. 
 + 
 +Vibration response of a gyro = Linear-g X-Axis Acceleration + (VRE X-Axis Acceleration)^2
  
-====== Linear-g Rejection (Linear-g Sensitivity) ====== +====== Additional Resources! ====== 
-Unintended effect where linear acceleration is detected as rotation+* Information on Allan Variance for Gyros: http://www.alexandertrusov.com/uploads/pdf/2011-UCI-trusov-whitepaper-noise.pdf
  
  
  
resources/eval/user-guides/inertial-mems/imu-overview.1626823425.txt.gz · Last modified: 21 Jul 2021 01:23 by Chas Frick

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