Pitch Moment Generation and Measurement in a Robotic Hummingbird

Abstract

Micro Air Vehicles (MAVs) with flapping wings try to mimic their biological counterparts, insects and hummingbirds, as they can combine high agility manoeuvres with precision hovering flight. Near-hovering flapping flight is naturally unstable and needs to be stabilized actively. We present a novel mechanism for pitch moment generation in a robotic hummingbird that uses wing twist modulation via flexible wing root bars. A custom build force balance, sensitive enough to measure the cycle averaged pitch moment as well as lift force, is also presented. The introduced prototype mechanism generates pitch moment of up to ± 0.5 mNm. Finally we integrate a Shape Memory Alloy (SMA) wire to actuate the wing root bar ends. We present achievable displacement versus bandwidth as well as generated pitch moment.

Pitch and Roll Control Mechanism for a Hovering Flapping Wing MAV

“…The flapping mechanism was already presented in [12], see Figure 2. A linkage mechanism, driven by a DC motor, is used to transform the motor shaft rotation into the flapping motion of the wings.…”

“…The experiments presented here include high speed camera measurements of the wing kinematics as well as lift and pitch moment measurements on a custom built force balance [12]. Unless mentioned otherwise, all the tests were carried out at a moderate flapping frequency of 15 Hz in order to have consistent results in all the tests.…”

“…Its role is to generate moments for attitude stabilization and flight control. In our previous work [12] we presented a concept inspired by the Nano hummingbird [10] that produces the moments by modulating the wing twist. This concept, however, requires specific wing design.…”

Experimental Studies of Tail Shapes for Hummingbird-Like Flapping Wing Micro Air Vehicles

“…That is to say, the posture of flapping-wing MAVs can be performed via adjusting the position of the tail, which is firstly presented and trialled in twin-wing hovering flapping wing MAVs. In the previous study of twin-wing hovering flapping wing MAVs, the wing twist modulators [17], [23], [38], [39] were universally employed to produce pitch and roll moment then achieved the stability of flapping wing MAVs.…”

Design and analysis of the link mechanism for the flapping wing MAV using flexible multi-body dynamic analysis

“…Finally, appropriate flapping amplitude and actuation frequency which would create sufficient lift were estimated using UBET prediction. 8 UBET refers to an unsteady blade element theory which is based on quasi-steady aerodynamics. In the present UBET analysis, the wing mass and center of gravity were set to 0.1 g and 0.1%, respectively, along the chord length in each case.…”