Urzua, S.; Munguia, R.F.; Grau, A. Journal of intelligent and robotic systems: theory and applications (Online) Vol. 2018, p. 1-15 DOI: 10.1007/s10846-018-0775-y Data de publicació: 2018-02-02 Article en revista
A typical navigation system for a Micro Aerial Vehicle (MAV) relies basically on GPS for position estimation. However,for several kinds of applications, the precision of the GPS is inappropriate or even its signal can be unavailable. In this context, and due to its flexibility, Monocular Simultaneous Localization and Mapping (SLAM) methods have become a good alternative for implementing visual-based navigation systems for MAVs that must operate in GPS-denied environments.
On the other hand, one of the most important challenges that arises with the use of the monocular vision is the difficulty to recover the metric scale of the world. In this work, a monocular SLAM system for MAVs is presented. In order to overcome the problem of the metric scale, a novel technique for inferring the approximate depth of visual features from an ultrasonic range-finder is developed. Additionally, the altitude of the vehicle is updated using the pressure measurements of a barometer. The proposed approach is supported by the theoretical results obtained from a nonlinear observability test.
Experiments performed with both computer simulations and real data are presented in order to validate the performance of the proposal. The results confirm the theoretical findings and show that the method is able to work with low-cost sensors.
Rotondo, D.; Cristofaro, A.; Johansen , T. A.; Nejjari, F.; Puig, V. Journal of intelligent and robotic systems: theory and applications (Online) p. 1-15 DOI: 10.1007/s10846-017-0716-1 Data de publicació: 2017-10-05 Article en revista
This paper proposes a discrete-time linear parameter varying (LPV) unknown input observer (UIO) for the diagnosis of actuator faults and ice accretion in unmanned aerial vehicles (UAVs). The proposed approach, which is suited to an implementation on-board, exploits a complete 6-degrees of freedom (DOF) UAV model, which includes the coupled longitudinal/lateral dynamics and the impact of icing. The LPV formulation has the advantage of allowing the icing diagnosis scheme to be consistent with a wide range of operating conditions. The developed theory is supported by simulations illustrating the diagnosis of actuator faults and icing in a small UAV. The obtained results validate the effectiveness of the proposed approach.