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Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion

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Science  20 May 2016:
Vol. 352, Issue 6288, pp. 978-982
DOI: 10.1126/science.aaf1092
  • Fig. 1 Robot design and principle of operation.

    (A) Before initiating a perching maneuver, the robot attains stable hovering underneath the target surface. A compliant mount assures successful alignment between the adhesive patch and the target surface. Upon contact, the electrodes in the patch induce surface charges on the substrate, leading to an electrostatic attraction between the surface and the patch. These surface charges recombine when the voltage between the electrodes is switched off, allowing for a smooth detachment. (B) Depiction of the flapping wing MAV capable of landing on and relaunching from the underside of nearly any material. (C) The adhesion mechanism relies on compliant circular copper electrodes on a polyimide film that are embedded in Parylene C to generate electrostatic adhesion. This is supported by a carbon fiber cross and integrated with the robot through a polyurethane foam mount. The final version of the mechanism weighs 13.4 mg (robot without payload, 84mg). (D and E) The polyurethane foam mount provides damping and passive alignment to facilitate perching over a wide envelope of trajectories and allows us to integrate features to assist with characterizing the flight performance before perching experiments (fig. S11).

  • Fig. 2 Characteristics of the electroadhesives and control approach.

    (A) Normal adhesion of the presented conformal electrodes on various materials at 1000 V. All measurements were conducted with the same test patch (comb-like interdigitated electrodes, scaled up from the final flightworthy size) without cleaning between tests. Error bars indicate 1 SD from five consecutive measurements. For each substrate, the arithmetic mean of the absolute values of the surface asperities is stated in parentheses. The dashed red line indicates the pressure required to support the vehicle weight (including the adhesion mechanism), assuming a patch size as used in our demonstrations. (B) Charging current for the circular patch on glass at 1000 V [switched on at time (t) = 0 s]. Charging requires 37.7 μJ on glass, 37.4 μJ on wood, and 46.6 μJ on copper. (C) Current in the charging phase and during steady state on glass (1000 V). A leakage current of 6.9 nA occurs on glass (1.4 nA on wood; 1.0 nA on copper). The mechanism requires 6.9 μW to remain perched on glass (1.4 μW on wood; 1.0 μW on copper). This is substantially lower than the flight power of 19 mW (23). (D) Commanded and measured altitude during an exemplary perching flight. The logic module initiates a bio-inspired landing trajectory once the robot has achieved stable hovering in the target region underneath the substrate. The flapping amplitude is ramped down (corresponding to a decrease in commanded altitude) once the logic module detects a successful attachment.

  • Fig. 3 Perching and relaunch demonstrations on a leaf, glass, and unfinished plywood.

    (A) Frame overlay from a high-speed video taken of a successful landing maneuver on a natural leaf. (B to D) The micro aerial vehicle after successfully landing on a leaf, glass, and unfinished plywood (wings turned off). (E) Frame overlay from a high-speed video taken of a successful relaunch from unfinished wood, followed by stable hovering flight (10.5 s) and a smooth landing on the ground (12.28 s).

Supplementary Materials

  • Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion

    M. A. Graule, P. Chirarattananon, S. B. Fuller, N. T. Jafferis, K. Y. Ma, M. Spenko, R. Kornbluh, R. J. Wood

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

    Download Supplement
    • Materials and Methods
    • Figs. S1 to S11
    • Table S1
    • Full Reference List

    Images, Video, and Other Other Media

    Movie S1
    This video shows successful perching on plywood, glass and a natural leaf in real-time, followed by a segment showing the landing on a leaf played back at 0.125x real-time speed. The last segment shows two takeoffs to stable hovering flight from plywood, the first played back at real-time speed and the second played back at 0.125x real-time speed. A US quarter dollar is shown for scale.

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