Flying like a bird

Human-made birds (airplanes, and so on) move by using propellers or jets on rigid airframes. Birds fly using only the muscle power of their wings. Birds measure, control, and regulate their motion through the air continuously and fully autonomously.

Leonardo da Vinci has built rudimentary flapping wing models trying to copy bird flight. In 1889, Otto Lilienthal in Germany published the book on bird flight where he described in detail the flight of seagulls. Dr. James DeLaurier and his research team at the University of Toronto did an ornithological project where, in 2006, they succeeded for the first time in taking off from a runway with a flying device powered by a flapping-wing mechanism. In August 2010, a flying machine propelled by its pilot’s muscle power alone covered a distance of about 150 meters after being towed to flying altitude.

In 2011, the engineers at the Bionic Learning Network of Festo, a world leader in industrial automation and bionic technology, developed a flying device called SmartBird that is capable of taking off on its own and flying by using its flapping wings. SmartBird’s most important feature is active torsion of its wings. The goal of the SmartBird project was to produce an efficient structure with efficient resource and energy consumption. Propulsion, lift in the wings, and a flight control unit were functionally integrated into the body and tail regions of SmartBird. Excellent aerodynamics, high power density for propulsion, lift, and maximum agility for the flying device were also achieved.

Small form factors fly inside SmartBird

The Festo engineers functionally integrated coupled hybrid drive units. Efficiency in resource and energy consumption was reached through minimal use of materials and extremely lightweight construction. This implementation of coupled drives for linear and rotary movement can be used in generators that derive energy from water, like stroke wing generators or actuators in process automation.

The self-controlling electronics inside SmartBird reside on a small form-factor board using the Stellaris MCU LM3S811 microcontroller from Texas Instruments. This ARM Cortex-M3 based design features high-performance 32-bit computing, a large selection of analog and digital I/O and other industrial embedded functions that are not available on x86-based designs. SmartBird was shown flying above visitors every hour on the hour during the Hannover Fair (see “European events” section).

Some parameters of SmartBird:

  • Torso length: 1.07 m
  • Wingspan: 2.00 m
  • Weight: 0.450 Kg (about 1 lb)
  • Structure: lightweight carbon fiber
  • Electrical power: 23 W

Wing movement is key in aerodynamic efficiency

Flapping-wing flight is a combination of two principal movements. The wings beat up and down, using a lever mechanism with a degree of deflection that increases from the body to the wing tip. At the same time, the wing twists such that its leading edge is directed upwards during the upward stroke for a positive angle of attack, followed by a negative angle after a fraction of a wing-beat period.

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Figure 1: The SmartBird’s wing movements mimic the active wing torsion of a seagull.
(Click graphic to zoom by 1.9x)

The onboard electronics control wing torsion in relation to wing position. An integrated microcontroller calculates the optimal setting of two servo motors and synchronizes the flapping movement and torsion to precisely control the wing motion. The active joint torsion drive requires controlled coordination between the flapping and twisting movements through continuous monitoring. Two-way radio communication with ZigBee protocol is used to monitor the wing’s position and torsion as well as report battery charge, power consumption, and input by the pilot. The torsion control parameters are optimized in real-time, which allows the electronic control system to adapt to changing requirements within a fraction of a second. SmartBird has an electromechanical efficiency factor of around 45 percent, which is better than a car engine. Measurements of circular flight have demonstrated an aerodynamic efficiency factor as high as 80 percent.

European events

Hannover Fair 2011 (April 4-8) is claimed to be the best-performing industrial fair of the last 10 years. More than 6,500 exhibitors from 65 countries showed more than 5,000 innovations to more than 230,000 visitors.

For more information, contact Hermann at hstrass@opensystemsmedia.com.