Allan Variance ROS
ROS package which loads a rosbag of IMU data and computes Allan Variance parameters
The purpose of this tool is to read a long sequence of IMU data and return the Angle Random Walk (ARW), Bias Instability and Random Walk for the gyroscope as well as Velocity Random Walk (VRW), Bias Instability and Random Walk for the accelerometer.
How to use
Build the package:
catkin build allan_variance_ros
Recommended: Reorganize ROS messages by timestamp using ROS Cookbook:
rosrun allan_variance_ros cookbag.py --input original_rosbag --output cooked_rosbag
Run the Allan Variance computation tool:
rosrun allan_variance_ros allan_variance [path_to_rosbags] [path_to_config_file]
This will compute the Allan Deviation for the IMU and generate a CSV. The next step is to visualize the plots and get parameters. For this run:
rosrun allan_variance_ros analysis.py --data allan_variance.csv
space to go to next figure.
How to collect sequence
Place your IMU on some damped surface and record your IMU data to a rosbag. You must record at least 3 hours of data. The longer the sequence, the more accurate the results.
3 hour log of Realsense D435i IMU already "cooked".
Example terminal output:
ACCELEROMETER: X Velocity Random Walk: 0.00333 m/s/sqrt(s) 0.19983 m/s/sqrt(hr) Y Velocity Random Walk: 0.01079 m/s/sqrt(s) 0.64719 m/s/sqrt(hr) Z Velocity Random Walk: 0.00481 m/s/sqrt(s) 0.28846 m/s/sqrt(hr) X Bias Instability: 0.00055 m/s^2 1.99258 m/hr^2 Y Bias Instability: 0.00153 m/s^2 5.51917 m/hr^2 Z Bias Instability: 0.00052 m/s^2 1.86155 m/hr^2 X Accel Random Walk: 0.00008 m/s^2 Y Accel Random Walk: 0.00020 m/s^2 Z Accel Random Walk: 0.00007 m/s^2 GYROSCOPE: X Angle Random Walk: 0.00787 deg/sqrt(s) 0.47215 deg/sqrt(hr) Y Angle Random Walk: 0.00987 deg/sqrt(s) 0.59204 deg/sqrt(hr) Z Angle Random Walk: 0.00839 deg/sqrt(s) 0.50331 deg/sqrt(hr) X Bias Instability: 0.00049 deg/s 1.76568 deg/hr Y Bias Instability: 0.00136 deg/s 4.88153 deg/hr Z Bias Instability: 0.00088 deg/s 3.15431 deg/hr X Rate Random Walk: 0.00007 deg/s Y Rate Random Walk: 0.00028 deg/s Z Rate Random Walk: 0.00011 deg/s
Kalibr is a useful collection of tools for calibrating cameras and IMUs. For IMU calibration it needs the noise parameters of the IMU generated in a yaml file.
allan_variance_ros automatically generates this file file as
#Accelerometer accelerometer_noise_density: 0.006308226052016165 accelerometer_random_walk: 0.00011673723527962174 #Gyroscope gyroscope_noise_density: 0.00015198973532354657 gyroscope_random_walk: 2.664506559330434e-06 rostopic: '/sensors/imu' #Make sure this is correct update_rate: 400.0 #Make sure this is correct