Communication systems have recently been very important in mini unmanned aerial vehicles (UAV), which include many research subjects. Directional antennas are generally used in communication systems, and they should continuously and efficiently follow the UAVs with minimal errors. For this purpose, an "Antenna Tracker" system, which is capable of real-time autonomous orientation based on GPS data from the UAV, was designed. In the beginning, the system's 3-dimensional solid model was obtained in SOLIDWORKS TM and its dynamical model was made in MATLAB / Simulink TM environment. For controlling the system, a discrete-time model-based computed torque proportional controller, which is the state-of-the-art innovation in this study, was designed in two axes, and then its simulation studies were conducted on the STM32 board. The simulation studies showed that controlling the pan and tilt axes is sufficient for effective tracking, and the presented antenna tracker system is suitable for use in mobile ground control stations (GCS). By using a short sampling time for the controller, stable and precise antenna tracking is accomplished for a given reference path. When a 0.5 Hz sinusoidal reference signal input which is the maximum speed for any antenna tracker was used as a sample reference track, ±0.3-and ±0.6-degrees position error of pan and tilt angles were obtained, respectively. The controller can easily satisfy a smooth tracking operation with high accuracy.
In this study, a novel received signal strength indicator (RSSI)-based tracking algorithm for antenna tracker systems utilizing directional antennas is proposed. This system has two sequential phases, which are the “Full Area Scan Phase” and the “Active RSSI-Based Tracking Phase” with a unique elliptic trajectory formula for generating an original two-dimensional (2D) RSSI map to detect the maximum signal. An elliptic trajectory paves the way for splitting RSSI measurements into specific regions equally on this map in which any disturbance and noises are eliminated. The proposed method do not require any telemetry data or multiple receivers for antennas. The simulation results showed that the algorithm attained to 98 % accuracy with respect to the Global Positioning System (GPS)-based ones. In real-world experiments, it captures the first handshake signal within 6 seconds even when the unmanned aerial vehicle (UAV) positions are uncertain. Furthermore, it is demonstrated that this novel technique can provide a continuous tracking at high resolution with the error value of [Formula: see text] and [Formula: see text] in the elevation and azimuth axes, respectively, compared with the GPS-based one. In conclusion, the simulation and test studies indicated that the proposed method could achieve a higher precision tracking with its advantages against the former methods.
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