Abstract
As the "low-altitude economy" expands across logistics, agriculture, and environmental monitoring, drone flight efficiency and endurance have become critical constraints. This research presents a redesign of the DJI F450 drone arm using a dual-stage optimization workflow. By combining topology optimization in SolidWorks with Computational Fluid Dynamics (CFD) analysis in COMSOL Multiphysics®, the study achieved a mass reduction to 41 grams while significantly enhancing structural rigidity and aerodynamic performance. The optimized design demonstrates a 36.2% reduction in drag at a 0° attack angle and a 300% decrease in maximum displacement compared to the stock DJI F450 arm, providing a robust framework for developing high-performance, lightweight UAV components.
Introduction
The primary challenge in modern UAV design is overcoming the energy density limitations of current battery technology. To extend flight times, engineers must minimize "dead weight" and aerodynamic resistance. This study targets the structural arms of the DJI F450, a widely used industry-standard platform. The objective was to reduce the arm's mass without compromising its safety factor, while simultaneously optimizing its geometry to facilitate better airflow.
Methodology
The researchers implemented a two-stage digital design workflow to balance structural integrity with aerodynamic efficiency.
Topology Optimization
Using the Solid Isotropic Material with Penalization (SIMP) method in SolidWorks, the team defined a design space based on a solid block version of the F450 arm. A 50N lift force was applied as the primary load. The algorithm iteratively removed material that did not contribute significantly to the load path, targeting a 90% mass reduction from the initial solid volume.
Aerodynamic Refinement and CFD
The raw, jagged output from the topology optimization was manually refined into a manufacturable triangular truss structure. This geometry was then imported into COMSOL Multiphysics® for CFD analysis. Using a $k-\omega$ turbulence model, the researchers simulated airflow at 3 m/s across attack angles of 0°, 3°, and 6° to evaluate drag coefficients and pressure distributions.
Key Insights and Results
Structural Performance
The optimization process naturally converged on a triangular truss configuration. Triangles provide the most stable geometric structure, allowing for maximum material removal while maintaining high strength. Under a 50N load, the optimized arm exhibited a displacement of only 3.08 mm, a significant improvement over the 12.3 mm displacement of the stock arm. This represents a four-fold increase in stiffness. Furthermore, the safety factor improved by 19%, reaching 1.9 compared to the original 1.6.
Aerodynamic Efficiency
A critical finding was that the structural holes intended for weight reduction also served as passive airflow channels. By allowing air to pass through the arm, the design minimized low-pressure separation zones and turbulence behind the component. At a 0° attack angle, drag was reduced by 36.2%. Even at higher angles of attack (3° and 6°), the design maintained a drag reduction of approximately 21-22%.
Mass Reduction
The final design achieved a mass of 41g, a modest 2% reduction from the 42g stock arm but a nearly 50% reduction from the initial solid design space used for optimization. The primary gain, however, was the massive increase in structural efficiency per unit of mass.
Conclusion
This research demonstrates that topology optimization and CFD can be integrated to create drone components that are both lighter and significantly higher-performing than standard commercial parts. By aligning material distribution with specific load paths and leveraging structural voids for aerodynamic gain, the study achieved a design that is 4x stiffer and up to 36% more aerodynamic. Future work will focus on multi-objective optimization to solve for mass and drag simultaneously and experimental validation via 3D-printed prototypes in real-world flight conditions.