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Mechanical gull takes off as flight mysteries are `solved`

01 April, 2011

At this month’s Hannover Fair, Festo is unveiling the latest in its menagerie of mechanical creatures inspired by nature – an uncannily lifelike flying robot called SmartBird (below).

Festo says that its researchers have succeeded, for the first time, in unravelling the mystery of precisely how birds fly. It has harnessed this knowledge to give SmartBird a unique movement that distinguishes it from all previous mechanical flapping wing systems and allows the contraption to take off, fly and land autonomously.

The 450g “bird” flies, glides and sails through the air just like the herring gull on which it is modelled, with no additional drive mechanisms. Its 2m-wide wings not only beat up and down, but also twist to precise angles. This is achieved using an active, articulated torsional drive which, in combination with a complex control system, is said to deliver “unprecedented efficiency” for mechanical flight systems.

The aim of the SmartBird project was to achieve a lightweight structure that is efficient both in terms of resources and of energy consumption. It also had to deliver good aerodynamics, a high power density, and extreme agility.

The bird’s propulsion and lift are achieved solely by flapping its wings using just 23W of power. There are four onboard servodrives – two for controlling wing torsion, and two for the head and tail sections. The driving power comes from a tiny brushless exterior-rotor motor and a 450mA, 7.4V lithium polymer battery.

The wings are driven via a two-stage helical transmission system, causing them to beat up and down with a reduction ratio of 1:45. Three Hall sensors monitor their positions. The flapping and bending forces are conveyed from the transmission to the wings via a flexible link. Opposing movements of the head and torso sections are synchronised using two of the servo actuators. The torso thus bends aerodynamically, displacing its weight and helping to improve the SmartBird’s manoeuvrability.

The bird’s wing positions, torsion, and other factors such as battery charge and power consumption, are monitored wirelessly using the ZigBee protocol. This information is used to allow the mechanism to adapt to new situations within a fraction of a second.

Measurements have shown that the bird has an electromechanical efficiency of around 45% and an aerodynamic efficiency of up to 80%.

The torsion control parameters can be adjusted and optimised in real time during flight. The wing flapping and twisting sequence is controlled to within a few milliseconds to optimise airflow around the wings.

Festo believes that the SmartBird project could lead to practical applications ranging from energy generators to actuators for process automation.




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