An Analytical Solution to the IMU Initialization Problem for Visual-Inertial Systems

TL;DR

This paper introduces an efficient analytical method for initializing IMU parameters in visual-inertial systems, improving speed and accuracy over iterative methods without needing initial guesses.

Contribution

It presents a novel non-iterative, maximum-likelihood analytical solution for IMU bias, gravity direction, and scale estimation, enhancing computational efficiency and robustness.

Findings

Achieves comparable accuracy to state-of-the-art methods

Reduces computational cost significantly

Does not require initial scale guess

Abstract

The fusion of visual and inertial measurements is becoming more and more popular in the robotics community since both sources of information complement well each other. However, in order to perform this fusion, the biases of the Inertial Measurement Unit (IMU) as well as the direction of gravity must be initialized first. Additionally, in case of a monocular camera, the metric scale is also needed. The most popular visual-inertial initialization approaches rely on accurate vision-only motion estimates to build a non-linear optimization problem that solves for these parameters in an iterative way. In this paper, we rely on the previous work in [1] and propose an analytical solution to estimate the accelerometer bias, the direction of gravity and the scale factor in a maximum-likelihood framework. This formulation results in a very efficient estimation approach and, due to the non-iterative nature of the solution, avoids the intrinsic issues of previous iterative solutions. We present an extensive validation of the proposed IMU initialization approach and a performance comparison against the state-of-the-art approach described in [2] with real data from the publicly available EuRoC dataset, achieving comparable accuracy at a fraction of its computational cost and without requiring an initial guess for the scale factor. We also provide a C++ open source reference implementation.