MI-Calib: An Open-Source Spatiotemporal Calibrator for Multiple IMUs Based on Continuous-Time Batch Optimization

Abstract

The inertial measurement unit (IMU), as an interoceptive sensor typically providing high-frequency angular velocity and specific force measurements, has been widely exploited for accurate motion estimation in modern robotic applications, such as autonomous navigation and exploration. Recently, there has been a trend of integrating multiple IMUs in inertial systems, which outperforms traditional standalone ones regarding the resiliency of sensor failures and measurement depletion and is commercially affordable due to the significantly reduced price for IMUs. For such multi-IMU systems, accurate and consistent spatiotemporal calibration is inevitably required to perform information fusion in a unified framework. Considering most existing methods generally involve additional aiding sensors in calibration, lacking convenience and usability, we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MI-Calib:</i> a high-performance multi-IMU spatiotemporal calibrator based on continuous-time batch optimization, which utilizes only raw inertial measurements from multiple IMUs and requires no prior. In particular, a rigorous multi-stage initialization procedure is first conducted to recover initial guesses of parameters, followed by a batch optimization, where all states would be refined to global optimal ones. Results from both simulated and real-world experiments demonstrate the high accuracy and consistency of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MI-Calib</i>.