Auto altitude holding of quadrotor UAVs with Kalman filter based vertical velocity estimation

Altitude regulation is a fundamental control problem of quadrotor UAVs (unmanned aerial vehicles) to ensure required performance for hovering and autonomous navigation. In this paper, under the assumption that the attitude inter loop has been well designed, the stability features of linear P+D+DD controller for altitude control are investigated. To handle the difficulty that the altitude velocity cannot be measured directly, a Kalman filter based ascending/decending velocity estimator using the measurements of acceleromter and barometer/sonser is adopted for velocity feedback. Given the overall dynamics model, P+D+DD controller design procedure and its stability analysis, the effectiveness of the algorithms is validated by field test using our quadrotor. The approaches can be directly extended to the translation velocity estimation and navigation control.