Application of UKF on quaternions

1. Is Ukf always better than EKF?
2. What are quaternions used for?
3. Why should you use quaternions over Euler angles?
4. What is EKF and UKF?

Is Ukf always better than EKF?

The accuracy of the predicted measurement in UKF is more accurate than that of EKF. UKF approximates the predicted measurements with the sigma points via the system dynamic model and then the observation model.

What are quaternions used for?

Unit quaternions, known as versors, provide a convenient mathematical notation for representing spatial orientations and rotations of elements in three dimensional space. Specifically, they encode information about an axis-angle rotation about an arbitrary axis.

Why should you use quaternions over Euler angles?

For rotations, quaternions are superior to using Euler angles. The reason is that quaternions avoid a problem known as gimbal lock. That happens if two of the three rotational axes happen to align.

What is EKF and UKF?

The Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) are derived from the KF. The EKF is the nonlinear version of the KF which linearizes about the mean and covariance, while the UKF is best known nonlinear estimates.