New RoboFalcon 2.0 advances biomimetic robotics with FSF cycle validated in real flights

Researchers from Northwestern Polytechnical University, located in Xi’an, in China, presented RoboFalcon 2.0, a robot capable of taking off autonomously by reproducing flight patterns observed in birds and bats. The prototype uses a mechanism that integrates flapping, sweeping and folding of the wings in a continuous cycle, allowing precise control at low speeds.

This innovation solves historic challenges in biomimetic aerial robotics, where previous designs relied on external assistance for takeoff or limited slow maneuvers. Testes carried out in the laboratory and wind tunnel confirmed the effectiveness of the system in varied conditions.

• Tethered flight capability with stable trajectory.
• Independent amplitude adjustment for pitch control.
• Adjustable beat frequency up to 7.5 Hz.

Technical characteristics of the prototype

The RoboFalcon 2.0 weighs approximately 800 grams and has a wingspan of 1.2 meters. The central drive system uses a single motor connected to a conical rocker mechanism, responsible for transmitting movement to the wings.

The wings are divided into three segments covered by a polyester membrane, ensuring flexibility during cycles. Mecanismos of decoupling allows independent variation in bend and sweep, creating inclined stroke planes similar to those of slow-flying birds.

More on this story: Bird robot prototype performs autonomous takeoff and imitates avian biology in tests in China

Integrated FSF movement pattern

The flap-sweep-fold cycle combines three essential actions in each beat. Durante the downstroke, forward ventral movement generates most of the lift, while the retracted upstroke minimizes aerodynamic drag.

The sweep varies between 5 and 25 degrees, modulating the pitching moment in a controlled manner. Larger Amplitudes strengthen the leading edge vortex, improving performance at low speeds.

The folding of the wings contributes to stability in the inactive phases of the cycle. Essa integration provides precise hovering maneuvers and transition to directed flight.

Tests carried out in wind tunnel

Experiments in an open wind tunnel evaluated the prototype at speeds from zero to 7 meters per second. Medições with a six-component load cell recorded a consistent increase in average lift with greater sweep amplitude.

The liquid thrust remained stable at different beating frequencies. The pitching moment became positive at higher speeds, indicating adequate control.

Results showed reduced standard deviations, confirming repeatability of measurements.

Learn more: Researchers in China create autonomous flying robot that imitates exact movements of real birds

Fluid dynamics simulations

Computational analyzes based on Navier-Stokes equations identified strengthening of the leading-edge vortex at maximum sweep configurations. The center of pressure has moved anteriorly, expanding the aerodynamic moment arm.

Pressure distributions on the wing surfaces revealed extensive zones of low pressure on the leading edge. Esses phenomena explain the observed gains in lift during slow flight.

The simulations validated the efficiency of the reconfigurable mechanism in low-speed scenarios.

Control during takeoff process

Dynamic simulation models implemented PID control to analyze autonomous takeoff. Ajustes in wing sweep maintained stable pitch in quasi-hovering below 3 meters per second.

At different scales, the system demonstrated control capacity proportional to demands. Resultados indicated the need for compensation at higher speeds to avoid divergences.

Real flights validated in the laboratory

Tethered tests within a 15-meter radius confirmed takeoff without external assistance. With a standard center of gravity, the trajectory followed an S-shaped pattern, reaching a maximum speed of 4 meters per second at 7 Hz.

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Previous adjustment to the center of gravity allowed acceleration of up to 6 meters per second without pitch instability. Consumo power reached around 400 watts during intense maneuvers.

Evolution compared to previous versions

Unlike the 2021 model, which is restricted to cruise flights, the RoboFalcon 2.0 incorporates specific reconfigurations for low-speed operation. Designs inspired by insects generally use unique degrees of freedom, diverging from patterns observed in vertebrates.

The new prototype addresses historical limitations by coordinating active and inactive phases in an integrated manner. Energy efficiency remains challenging at the bird scale, but advances make the approach viable for practical applications.

Development context at China

The research was conducted at Northwestern Polytechnical University, in Xi’an, Shaanxi province, recognized for its tradition in aeronautical engineering. The responsible team evolved mechanisms from previous prototypes, integrating advanced mechanical and electronic components.

RoboFalcon 2.0 positions the institution as a reference in aerial biomimetic robotics. The results open perspectives for future improvements in autonomy and flight efficiency.