Nature-inspired ‘monocopter’ folds its wings in the air and quickly dives to escape

Taking inspiration from nature, researchers have developed a new rotary-wing drone capable of folding and extending its wings during flight.

The Singapore University of Technology (SUT) team and Design’s FROW (Foldable Rotary Origami Wing) drone take design inspiration from the Samara Seed Flight-inspired monocopter platform.

The wings are made using origami techniques, which allows them to fold during flight. Two configurations are offered, each with active or passive wing folding mechanisms, tailored to meet the needs of particular applications.

The team presents two versions of the design, each with active or passive wing-folding mechanics based on the particular needs of the application. In flight, both configurations can minimize their total footprint by approximately 39% and 69%, respectively.

Monocopter innovations

In recent years, unmanned aerial vehicles (UAVs), particularly quadrotors, have become essential in various industries for tasks such as package delivery, building inspection, and surveillance due to their agility.

However, the direct lift generated by the propeller of quadcopters makes them less energy efficient. Fixed-wing drones offer greater efficiency but lack versatility in confined spaces.

Inspired by Samara Seeds, the monocopters rotate around their yaw axis, providing efficient lift. They are being researched for lightweight sensors, urban surveillance, LiDAR odometry and environmental mapping.

Powered monocopters use motors and servos for flight control, while recent variants explore twin-wing and foldable designs for adaptability and storage convenience.

According to the researchers, folding wings of aerial vehicles during flight constitute a new concept. They aim to actively or passively control the wingspan in mid-flight. Previous designs focus on active shape changes for agility or passive unfolding for storage, but lack repeated shape change capability.

The team’s FROW design is inspired by the graceful folding of birds’ wings to navigate tight spaces. According to the researchers, it overcomes the monocopter challenge of maneuvering in confined areas by folding its wings in mid-flight, reducing its footprint.

The researchers developed two configurations: FROW-A, with active wing folding controlled by actuators, and FROW-P, with passive folding without actuators. Both configurations share a design principle inspired by bird flight, improving flexibility and usability.

Origami inspired flight

Origami techniques inspired FROW’s wing design, which facilitates accordion folding to reduce bulk. The suspension brackets attach directly to the folds, simplifying the mechanism.

The wing, imitating a samara seed, balances rigidity for flight and flexibility for folding. Balsa wood panels, laminated with plastic, provide structural integrity. Hot air molding maintains a folded shape.

The FROW-A design limits wing folding to 40% of total span to maintain lift capacity. The integration of two wings minimizes the stress on the actuators. FROW-P uses a spiral spring for passive folding, reducing the wing area by 70%. Telescopic rods eliminate excess carbon fiber protrusion, ensuring smooth movement without twisting.

The results demonstrate successful flight in both deployed and stowed modes, validating the practical ease of use by reducing bulk and navigating small spaces.

Additionally, the researchers say experiments demonstrate the effectiveness of the passively folding mechanism, as the platform successfully performs dives and mid-air recoveries.

These advances promise to improve the versatility of monocopter platforms, providing solutions for agile navigation and efficient use of space in various applications.

The researchers suggest that future work will optimize the wing shape and improve other flight characteristics to improve performance.

Details of the research have been published in the journal Bioinspiration & Biomimetics.