Tilt estimator for 3D non-rigid pendulum based on a tri-axial accelerometer and gyrometer
This addresses the need for accurate tilt estimation in balance control for humanoid robots, but it appears incremental as it builds on existing observer methods for similar systems.
The paper tackles the problem of tilt estimation for a 3D non-rigid pendulum, such as a humanoid robot, by developing a new observer that uses inertial measurements and joint encoders, achieving almost global asymptotic convergence and local exponential stability as proven in simulations.
The paper presents a new observer for tilt estimation of a 3-D non-rigid pendulum. The system can be seen as a multibody robot attached to the environment with a ball joint. There is no sensor for the joint position of the sensor. The estimation of tilt, i.e. roll and pitch angles, is mandatory for balance control for a humanoid robot and all tasks requiring verticality. Our method obtains tilt estimations using encoders on other joints and inertial measurements given by an IMU equipped with tri-axial accelerometer and gyrometer mounted in any body of the robot. The estimator takes profit from the kinematic coupling resulting from the pivot constraint and uses the entire signal of accelerometer including linear accelerations. Almost Global Asymptotic convergence of the estimation errors is proven together with local exponential stability. The performance of the proposed observer is illustrated by simulations.