In this paper, we propose a novel robocentric formulation of visual-inertial navigation systems (VINS)within a multi-state constraint Kalman filter (MSCKF)framework and develop an efficient, lightweight, robocentric visual-inertial odometry (R-VIO)algorithm for consistent localization in challenging environments using only monocular vision. The key idea of the proposed approach is to deliberately reformulate the 3D VINS with respect to a moving local frame (i.e., robocentric), rather than a fixed global frame of reference as in the standard world-centric VINS, and instead utilize high-accuracy relative motion estimates for global pose update. As an immediate advantage of using this robocentric formulation, the proposed R-VIO can start from an arbitrary pose, without the need to align its orientation with the global gravity vector. More importantly, we analytically show that the proposed robocentric EKF-based VINS does not undergo the observability mismatch issue as in the standard world-centric frameworks which was identified as the main cause of inconsistency of estimation. The proposed R-VIO is extensively tested through both Monte Carlo simulations and real-world experiments using different sensor platforms in different environments and shown to achieve competitive performance with the state-of-the-art VINS algorithms in terms of consistency, accuracy and efficiency.
As mentioned earlier, the VINS algorithms generally include the VI-SLAM @cite_41 @cite_33 @cite_15 and the VIO @cite_27 @cite_40 @cite_10 . The former jointly estimates the feature positions and the camera IMU pose that together form the state vector, whereas the latter does not include the features in the state but still utilizes the visual measurements to impose motion constraints between the camera IMU poses. In general, by performing mapping, the VI-SLAM gains the better accuracy from the feature map and the possible loop closures while incurring higher computational complexity than the VIO, although different methods have been proposed to address this issue (e.g., @cite_15 @cite_33 @cite_12 @cite_34 ). While there were also efforts to integrate VIO and SLAM @cite_22 @cite_2 , in this paper we focus on the design of lightweight VIO that can serve as an essential building block for large-scale navigation systems.
@cite_33 @cite_22 @cite_41 @cite_27 @cite_40 @cite_2 @cite_15 @cite_34 @cite_10 @cite_12
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In this paper, we propose a novel robocentric formulation of the visual-inertial navigation system (VINS) within a sliding-window filtering framework and design an efficient, lightweight, robocentric visual-inertial odometry (R-VIO) algorithm for consistent motion tracking even in challenging environments using only a monocular camera and a 6-axis IMU. The key idea is to deliberately reformulate the VINS with respect to a moving local frame, rather than a fixed global frame of reference as in the standard world-centric VINS, in order to obtain relative motion estimates of higher accuracy for updating global poses. As an immediate advantage of this robocentric formulation, the proposed R-VIO can start from an arbitrary pose, without the need to align the initial orientation with the global gravitational direction. More importantly, we analytically show that the linearized robocentric VINS does not undergo the observability mismatch issue as in the standard world-centric counterpart which was identified in the literature as the main cause of estimation inconsistency. Additionally, we investigate in-depth the special motions that degrade the performance in the world-centric formulation and show that such degenerate cases can be easily compensated in the proposed robocentric formulation, without resorting to additional sensors as in the world-centric formulation, thus leading to better robustness. The proposed R-VIO algorithm has been extensively tested through both Monte Carlo simulations and real-world experiments with different sensor platforms navigating in different environments, and shown to achieve better (or competitive at least) performance than the state-of-the-art VINS, in terms of consistency, accuracy and efficiency. We present PennCOSYVIO, a new challenging Visual Inertial Odometry (VIO) benchmark with synchronized data from a VI-sensor (stereo camera and IMU), two Project Tango hand-held devices, and three GoPro Hero 4 cameras. Recorded at UPenn's Singh center, the 150m long path of the hand-held rig crosses from outdoors to indoors and includes rapid rotations, thereby testing the abilities of VIO and Simultaneous Localization and Mapping (SLAM) algorithms to handle changes in lighting, different textures, repetitive structures, and large glass surfaces. All sensors are synchronized and intrinsically and extrinsically calibrated. We demonstrate the accuracy with which ground-truth poses can be obtained via optic localization off of fiducial markers. The data set can be found at https: daniilidis-group.github.io penncosyvio . One camera and one low-cost inertial measurement unit (IMU) form a monocular visual-inertial system (VINS), which is the minimum sensor suite (in size, weight, and power) for the metric six degrees-of-freedom (DOF) state estimation. In this paper, we present VINS-Mono: a robust and versatile monocular visual-inertial state estimator. Our approach starts with a robust procedure for estimator initialization. A tightly coupled, nonlinear optimization-based method is used to obtain highly accurate visual-inertial odometry by fusing preintegrated IMU measurements and feature observations. A loop detection module, in combination with our tightly coupled formulation, enables relocalization with minimum computation. We additionally perform 4-DOF pose graph optimization to enforce the global consistency. Furthermore, the proposed system can reuse a map by saving and loading it in an efficient way. The current and previous maps can be merged together by the global pose graph optimization. We validate the performance of our system on public datasets and real-world experiments and compare against other state-of-the-art algorithms. We also perform an onboard closed-loop autonomous flight on the microaerial-vehicle platform and port the algorithm to an iOS-based demonstration. We highlight that the proposed work is a reliable, complete, and versatile system that is applicable for different applications that require high accuracy in localization. We open source our implementations for both PCs ( https: github.com HKUST-Aerial-Robotics VINS-Mono ) and iOS mobile devices ( https: github.com HKUST-Aerial-Robotics VINS-Mobile ). Vision-aided inertial navigation techniques are described. In one example, a vision-aided inertial navigation system (VINS) comprises an image source to produce image data at a first set of time instances along a trajectory within a three-dimensional (3D) environment, wherein the image data captures features within the 3D environment at each of the first time instances. An inertial measurement unit (IMU) to produce IMU data for the VINS along the trajectory at a second set of time instances that is misaligned with the first set of time instances, wherein the IMU data indicates a motion of the VINS along the trajectory. A processing unit comprising an estimator that processes the IMU data and the image data to compute state estimates for 3D poses of the IMU at each of the first set of time instances and 3D poses of the image source at each of the second set of time instances along the trajectory. The estimator computes each of the poses for the image source as a linear interpolation from a subset of the poses for the IMU along the trajectory.