# IMU ### **MPU-9250** * cheap, readily available low-end IMU, at the cost about a few dollars. * Accelerometer noise density: 300 µg/√Hz * Gyroscope noise density: 0.01 º/sec/√Hz ### **Microstrain 3DM-GX5** * Industrial grade IMU made by microstrain; also available from Clearpath at about $2000. * 3DM-GX5-25 is adopted by LIO-SAM project. Note that its accelerometer and gyroscope have different coordinate setup in orientation. (But still, they can be regarded to have the same origin.) For more information, see . * We use 3DM-GX5-AHRS, and in this version the coordinate frames of accelerometer and gyroscope are treated identical. It comes equipped with built-in complementary filter and EKF algorithms, running at 1000Hz and 500Hz respectively. * Accelerometer noise density: 20 µg/√Hz (2 g) * Gyroscope noise density: 0.005°/sec/√Hz (300°/sec) ### VN-100 * High-end calibrated IMU with an onboard processor, provided by vectornav at about $1000. * Adopted by the CoSTAR team in the SubT challenge. * * ### **IMU Calibration Tool** * Kalibr requires the noise parameters of IMU as input, and this can be calibrated using the Allan variance method. Open source repo: ``` # This is the result calibrated for the Microstrain 3DM-GX5-AHRS IMU that we have # Accelerometer accelerometer_noise_density: 0.0002276846771973415 accelerometer_random_walk: 6.706087584689249e-06 # Gyroscope gyroscope_noise_density: 0.00010426654551109309 gyroscope_random_walk: 3.5636559575381104e-06 rostopic: '/sensors/imu' #Make sure this is correct update_rate: 200.0 #Make sure this is correct ```