Dynamic Droplet Size Control in Unmanned Aerial Spraying Systems for Balancing Drift Risk and Spray Quality

Objective

Unmanned Aerial Spraying Systems (UASS) are rapidly expanding in global agriculture, yet spray drift remains a major constraint, particularly under strict regulatory frameworks such as those in the EU. The key challenge is the inherent trade-off between spray quality and drift reduction: fine droplets provide better coverage but are highly drift-prone, while coarse droplets reduce drift but compromise deposition uniformity. This project proposes a dynamic droplet size control strategy to resolve this contradiction. Within a single spraying mission, the system will apply fine droplets in upwind areas to secure target coverage, and switch to coarser droplets when approaching field boundaries to mitigate drift risk. The objectives will be achieved by combining engineering design, physical and data-driven modeling, and agronomic validation. A coupled model linking droplet size, drift distance, and environmental parameters will be developed, embedded into a variable droplet spray system, and validated through both semi-controlled and multi-factor field trials. This integrated approach will ensure scientific robustness and practical feasibility. The project is hosted by the Universitat Politècnica de Catalunya (UPC, Spain) under the supervision of Prof. Emilio Gil, with co-supervision from Dr. Jean-Paul Douzals at INRAE (France). UPC contributes expertise in engineering-based pesticide application and European standardization, while INRAE provides the artificial wind wall platform for drift evaluation. The expected outcome is a validated strategy that achieves a dynamic balance between spray coverage and drift reduction, achieving up to 20% drift reduction in field trials. This directly supports the objectives of the Directive 2009/128/EC on the Sustainable Use of Plant Protection Products , contributes to the European Green Deal goals for sustainable agriculture, and advances the development of intelligent, environmentally responsible aerial spraying technologies.