  In this paper, WALK-VIO, a novel visual-inertial odometry (VIO) with
walking-motion-adaptive leg kinematic constraints that change with body motion
for localization of quadruped robots, is proposed. Quadruped robots primarily
use VIO because they require fast localization for control and path planning.
However, since quadruped robots are mainly used outdoors, extraneous features
extracted from the sky or ground cause tracking failures. In addition, the
quadruped robots' walking motion cause wobbling, which lowers the localization
accuracy due to the camera and inertial measurement unit (IMU). To overcome
these limitations, many researchers use VIO with leg kinematic constraints.
However, since the quadruped robot's walking motion varies according to the
controller, gait, quadruped robots' velocity, and so on, these factors should
be considered in the process of adding leg kinematic constraints. We propose
VIO that can be used regardless of walking motion by adjusting the leg
kinematic constraint factor. In order to evaluate WALK-VIO, we create and
publish datasets of quadruped robots that move with various types of walking
motion in a simulation environment. In addition, we verified the validity of
WALK-VIO through comparison with current state-of-the-art algorithms.
