Supplementary Materials

Mechanisms of collision recovery in flying beetles and flapping-wing robots

Hoang Vu Phan and Hoon Cheol Park

Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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  • Materials and Methods
  • Supplementary Text
  • Figs. S1 to S26
  • Tables S1 to S5
  • Captions for Movies S1 to S14
  • References

Images, Video, and Other Media

Movie S1
Unfolding process of the hindwing captured by a high-speed camera at 2,000 fps (playback at 30 fps). The movie shows the unfolding of the hindwing in a real beetle and a motor-driven system. Both experiments show that the apical field is released at the beginning, and fully unfolded at the end of upstroke motion, in one wing beat.
Movie S2
Unfolding process of a beetle's hindwing with clipped flexible joint (CFJ) and clipped membrane surface (CMS) captured by a high-speed camera at 2,000 fps (playback at 30 fps). The CFJ unfolding experiment was recorded after the first 10 wing beats. The CFJ wing is unable to be locked in outspread configuration during flapping. In the CMS unfolding experiment, the right wing with CMS requires more wing beats to unfold, compared to the left intact wing.
Movie S3
Self-unfolding of the beetle's hindwing. When the creases are tightened, the apical field is unable to be locked in its folded configuration. The stored energy enables the wing tip to unfold quickly to its outspread shape.
Movie S4
The beetle folding the hindwing after flight. The beetle uses its dorsal side of abdomen (tergum) to push the apical field back to a locked configuration.
Movie S5
Collision flight experiment of the beetle with perching behavior. The beetle uses its legs to catch the vertical post for perching while the hindwing (RA vein) hits the post. The outspread legs cover most of the length of the RA vein. The videos were captured by a high-speed camera at 2,000 fps (playback at 60 fps).
Movie S6
Collision flight experiment of the beetle with tumbling behavior after collision. The RA3 vein of the hindwing hits the vertical post first at the ventral side of the beetle, and collapses to pass the post. When the post approaches the mid-stroke, the hindwing hits the post at the RA vein out of the covering range of the legs (near the MJ). The vertical post disrupts the flapping wing motion (during downstroke), and causes substantial changes in the flight path and body attitude of the beetle. The video was captured by a high-speed camera at 2,000 fps (playback at 60 fps).
Movie S7
Collision flight experiment of the beetle with stable flight behavior after collision. The RA3 vein (wing tip) of the hindwing hits the vertical post and collapses to pass the post, facilitating the continuity of flapping motion. The collision thus occurs in both downstroke and upstroke wing motions. The video was captured by a high-speed camera at 2,000 fps (playback at 60 fps).
Movie S8
An artificially foldable wing with folding and self-unfolding capabilities. The wing performs both longitudinal and transverse folds at the BJ, and unfolds rapidly.
Movie S9
Flapping motion of the artificially foldable wing with and without reinforced vein (RV3) linkage captured by a high-speed camera at 2,000 fps (playback at 30 fps). The RV3 plays a significant role in retaining the outspread shape of the wing tip during flapping motion.
Movie S10
Wing collision tests of the beetle-inspired foldable wing versus unfoldable wing. In the collision torque measurement, the robot is mounted on the load cell Nano 17, and positioned at the location that the right wing collides with an obstacle (5 mm carbon rod) approaching with a speed of about 0.7 m/s at 75 % wingspan at the mid-stroke. The flapping wings are operated at a frequency of 24 Hz, to avoid failure recording of the load cell at high-frequency noises. The folding mechanism facilitates the continuity of the flapping motion. However, in the case of unfoldable wing, the obstacle causes the robot to stop flapping. In the free yaw test, the folding mechanism allows the wing tip to collapse and pass the obstacle, resulting in collision with only one wing, and small change in heading direction. With unfoldable wing, the robot yaws around until the other wing hits the obstacle, causing a reverse yawing. The video was captured by a high-speed camera at 2,000 fps (playback at 60 fps).
Movie S11
The tailless beetle-inspired robot taking off and hovering with foldable wings. The inherently unstable robot is remotely controlled by a pilot with equipped feedback control sensors. The video shows three flight tests; two hovering flights, and one quick takeoff. The video was captured by a high-speed camera at 125 fps (playback at 30 fps).
Movie S12
Colliding flight of the tailless robot implementing foldable wings without folding function. The robot is remotely controlled to fly across two vertical carbon rods located side-by-side, and spaced 180 mm apart from each other. The video was captured by a high-speed camera at 1,000 fps (playback at 30 fps).
Movie S13
Colliding flight of the tailless robot implementing foldable wings with folding function. The robot is remotely controlled to fly across two vertical carbon rods located side-by-side, and spaced 180 mm apart from each other. The video was captured by a high-speed camera at 1,000 fps (playback at 30 fps).
Movie S14
Colliding flight of the tailless robot without using foldable wings. The robot is remotely controlled to fly across two vertical carbon rods located side-by-side, and spaced 180 mm apart from each other. The video was captured by a high-speed camera at 1,000 fps (playback at 30 fps).