@Article{benallegue:ral:2020,
  author    = {Benallegue, Mehdi and Cisneros, Rafael and Benallegue, Abdelaziz and Chitour, Yacine and Morisawa, Mitsuharu and Kanehiro, Fumio},
  title     = {Lyapunov-Stable Orientation Estimator for Humanoid Robots},
  journal   = {IEEE Robotics and Automation Letters},
  year      = {2020},
  volume    = {5},
  number    = {4},
  pages     = {6371--6378},
  month     = {October},
  doi       = {10.1109/lra.2020.3013854},
  url       = {https://ras.papercept.net/proceedings/IROS20/3072.pdf},
  keywords  = {Attitude estimation, Inertial measurement unit},
  abstract  = {In this letter, we present an observation scheme, with proven Lyapunov stability, for estimating a humanoid\textquotesingle s floating base orientation. The idea is to use velocity aided attitude estimation, which requires to know the velocity of the system. This velocity can be obtained by taking into account the kinematic data provided by contact information with the environment and using the IMU and joint encoders. We demonstrate how this operation can be used in the case of a fixed or a moving contact, allowing it to be employed for locomotion. We show how to use this velocity estimation within a selected two-stage state tilt estimator: (i) the first which has a global and quick convergence (ii) and the second which has smooth and robust dynamics. We provide new specific proofs of almost global Lyapunov asymptotic stability and local exponential convergence for this observer. Finally, we assess its performance by employing a comparative simulation and by using it within a closed-loop stabilization scheme for HRP-5P and HRP-2KAI robots performing whole-body kinematic tasks and locomotion.},
  publisher = {IEEE-INST Electrical Electronics Engineers Inc},
  address   = {445 Hoes Lane, Piscataway, NJ 08855-4141, USA}
}