# Wind Source Localization System Based on a Palm-Sized Quadcopter
## 2 Problem Statement  
This study aims to implement anemotaxis capabilities in a palm-sized quadcopter and achieve wind source localization (WSL). As quadcopter size increases, benefits include longer flight times and increased payload capacity; however, larger quadcopters face challenges such as difficulty navigating indoor spaces [22] and potential harm to individuals.  
Therefore, this research adopts the palm-sized quadcopter platform (Tello, Ryze Technology, Shenzhen, China).  
To measure environmental winds using quadcopters, environmental winds must be distinguished from wakes generated during flight. Two main methods are utilized for quadcopter-based wind observations: The first is to estimate wind indirectly from the relationship between the ideal attitude--which changes according to the control input of the quadcopter--and the actual attitude. The second is to measure wind directly by attaching the wind sensor in a location where the influence of the wake is minimal. Indirect estimation methods avoid additional wind sensors, thus benefiting payload capacity, although they may fail to accurately estimate wind speed and direction under unexpected conditions. In contrast, direct measurement using wind sensors ensures the accurate acquisition of wind speed and direction as long as the sensors remain operational. This study adopts the direct measurement method using a wind direction sensor to achieve WSL under varying wind conditions.  
Past research implementing wind sensors on a quadcopter primarily proposed them as tools for monitoring environmental winds capable of measuring one-dimensional wind speeds. A human pilot was in control of navigating to specific destinations because its research goal was monitoring the environment. This study aims to detect wind speed and direction using a sensor, developing a system that autonomously makes appropriate decisions based on this information. To achieve this objective, the following components are integrated into the system:  
* The arrangement of a wind direction sensor to minimize wake interference and detect wind direction effectively.
* The development of an anemotaxis algorithm capable of making the appropriate decisions based on wind speed and direction information.  
Regarding sensor arrangement, past research suggests positioning them centrally and at a vertical distance from the quadcopter [19; 20]. However, the exact height adjustment for different quadcopter sizes remains unknown, and its position should be determined experimentally. Although the sensor directly measures wind speed and direction, considering the possibility that the effects of wakes cannot be eliminated, we must develop an anemotaxis algorithm that prevents movement in the wrong direction by utilizing wind speed information comprehensively in addition to wind direction. The combination of the proposed sensor arrangement and anemotaxis algorithm is experimentally evaluated by conducting WSL experiments in environments with different wind speeds. Assuming that localization is not achieved in a windless environment and the localization success rate is 70% or higher in wind environments with different wind speeds, the system is deemed to have been successfully constructed. This 70% standard was set as the same localization success rate as in the initial research into odor source localization using a palm-sized quadcopter [22].