Abstract
In recent years the use of Unmanned Aerial Vehicles (UAVs) has considerably grown in the civil sectors, due to their high flexibility of use. Currently, two important key points are making them more and more successful in the civil field, namely the decrease of production costs and the increase in navigation accuracy. In this paper, we propose a Kalman filtering-based sensor fusion algorithm, using a low cost navigation platform that contains an inertial measurement unit (IMU), five ultrasonic ranging sensors and an optical flow camera. The aim is to improve navigation in indoor or GPS-denied environments. A multi-rate version of the Extended Kalman Filter is considered to deal with the use of heterogeneous sensors with different sampling rates, and the presence of non-linearities in the model. The effectiveness of the proposed sensor platform is evaluated by means of numerical tests on the dynamic flight simulator of a quadrotor. Results show high precision and robustness of the attitude estimation algorithm, with a reduced computational cost, being ready to be implemented on low-cost platforms.
Highlights
In the last two decades, the use of small and micro-Unmanned Aerial Vehicles (UAVs) has considerably spread, with the increased level of autonomy and the development of low cost electronics devices, i.e., microcontrollers, sensors, etc. [1]
Nowadays the most widely used platforms for UAV navigation are based on the Global Positioning System (GPS) [4] and the Inertial Navigation System (INS) [5] including an inertial measurement unit (IMU) with magnetic, angular rate, and gravity sensors (MARG)
We propose a novel technique to compute accurate attitude and altitude estimation, by fusing data from an IMU, a downward oriented optical flow and five downward oriented distance sensors based on ultrasonic or time of flight (TOF) devices
Summary
In the last two decades, the use of small and micro-UAVs has considerably spread, with the increased level of autonomy and the development of low cost electronics devices, i.e., microcontrollers, sensors, etc. [1]. The possibility of multi-rotors (quadcopter, hexacopeter, etc.) to take off and land vertically, to move in any direction and hover over a fixed position gives them employment for reconnaissance missions in hostile and hazardous environment [2,3], where other aircraft and robots cannot be used Their use requires the solution of different technological problems, first of all the need of a robust and reliable attitude estimator, possibly executable on low-cost computational hardware and using only measurements from light-weight sensors. The paper is organized as follows: Section 2 defines the UAV attitude and altitude estimation problems; Section 3 presents the multi-rate EKF approach and, Section 4 describes the proposed testing platform and it shows the numerical results obtained by integrating the system on a quadrotor dynamic simulator
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