imu-calib

Kalibr-compatible IMU intrinsic calibration for Rust: estimate the parameters, then apply them online.

Implements the model from Rehder et al., "Extending Kalibr: Calibrating the Extrinsics of Multiple IMUs and of Individual Axes", ICRA 2016, and reads and writes the YAML files Kalibr uses.

Noise parameters

Record at least 3 hours with the IMU undisturbed, away from vibration.

use imu_calib::allan::{AllanConfig, AllanEstimator};

let mut estimator = AllanEstimator::new(AllanConfig::default());

// for every sample of the recording:
estimator.push(timestamp_seconds, raw_accel, raw_gyro);

let result = estimator.finish()?;
let noise = result.noise()?;

println!("accel noise density: {}", noise.accel_noise_density);
println!("gyro random walk:    {}", noise.gyro_random_walk);

std::fs::write("allan.csv", result.to_csv_string())?;

Intrinsics

Needs no camera and no target. Hold the IMU still in at least nine well-spread orientations, rotating about a different axis between each one. Start at rest: the first seconds set the noise floor that tells a hold from a move.

GuidedCalibration prompts through it live:

use imu_calib::estimate::{GuidedCalibration, GuidedConfig, Status};

let mut session = GuidedCalibration::new(GuidedConfig::default());

// for every incoming sample:
match session.push(t, raw_accel, raw_gyro) {
    Status::Initialising { collected, total } => { /* hold still */ }
    Status::WaitingForMotion { next_pose, total } => { /* pick it up and turn it */ }
    Status::WaitingForStillness { .. }           => { /* put it down */ }
    Status::Collecting { collected, total, .. }  => { /* keep holding */ }
    Status::PoseCaptured { pose, total }         => { /* one down */ }
    Status::Done => {
        let calibration = session.finish()?;
        println!("{}", calibration.report.summary());
        calibration.intrinsics.save_kalibr_yaml("imu.yaml")?;
    }
}

Apply

use imu_calib::ImuIntrinsics;

let intrinsics = ImuIntrinsics::from_kalibr_yaml("imu.yaml")?;
let corrector = intrinsics.corrector()?;   // build once

// per sample:
let (accel, gyro) = corrector.correct(raw_accel, raw_gyro);

Kalibr interop

from_kalibr_yaml reads Kalibr's imu-<bagname>.yaml directly, including the imu0: / imu1: nesting and every key of all three --imu-models:

let intrinsics = ImuIntrinsics::from_kalibr_yaml("imu-dynamic.yaml")?;
let second     = ImuIntrinsics::from_kalibr_yaml_named("imu-dynamic.yaml", "imu1")?;
let all        = ImuIntrinsics::all_from_kalibr_yaml_str(&yaml)?;

Files written by this crate use Kalibr's layout, so the two are interchangeable.

To feed a Kalibr run, write the flat input file after the Allan step:

intrinsics.save_kalibr_input_yaml("imu0.yaml")?;

rosrun kalibr kalibr_calibrate_imu_camera --target april_6x6_80x80cm.yaml --imu imu0.yaml --imu-models scale-misalignment --cam camchain.yaml --bag dynamic.bag

License