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Research Papers

Integrating Solar Cells Into Flapping Wing Air Vehicles for Enhanced Flight Endurance

[+] Author and Article Information
Ariel Perez-Rosado

Department of Mechanical Engineering,
University of Maryland,
College Park, MD 20742
e-mail: aperezro@umd.edu

Hugh A. Bruck

Department of Mechanical Engineering,
University of Maryland,
College Park, MD 20742
e-mail: bruck@umd.edu

Satyandra K. Gupta

Department of Mechanical Engineering
and Institute for Systems Research,
University of Maryland,
College Park, MD 20742
e-mail: skgupta@umd.edu

Manuscript received September 19, 2015; final manuscript received December 18, 2015; published online May 4, 2016. Assoc. Editor: James Schmiedeler.

J. Mechanisms Robotics 8(5), 051006 (May 04, 2016) (11 pages) Paper No: JMR-15-1271; doi: 10.1115/1.4032411 History: Received September 19, 2015; Revised December 18, 2015

Flapping wing aerial vehicles (FWAVs) may require charging in the field where electrical power supply is not available. Flexible solar cells can be integrated into wings, tail, and body of FWAVs to harvest solar energy. The harvested solar energy can be used to recharge batteries and eliminate the need for external electrical power. It can also be used to increase the flight time of the vehicle by supplementing the battery power. The integration of solar cells in wings has been found to alter flight performance because solar cells have significantly different mechanical and density characteristics compared to other materials used for the FWAV construction. Previously, solar cells had been successfully integrated into the wings of Robo Raven, a FWAV developed at the University of Maryland. Despite changes in the aerodynamic forces, the vehicle was able to maintain flight and an overall increase in flight time was achieved. This paper investigates ways to redesign Robo Raven to significantly increase the wing area and incorporate solar cells into the wings, tail, and body. Increasing wing area allows for additional solar cells to be integrated, but there are tradeoffs due to the torque limitations of the servomotors used to actuate the wings as well changes in the lift and thrust forces that affect payload capacity. These effects were modeled and systematically characterized as a function of the wing area to determine the impact on enhancing flight endurance. In addition, solar cells were integrated into the body and the tail. The new design of Robo Raven generated a total of 64% more power using on-board solar cells, and increased flight time by 46% over the previous design. They were also able to recharge batteries at a similar rate to commercial chargers.

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References

Figures

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Fig. 3

Parameters for wing design: S is the semispan, C is the chord, and tn are the diameters of carbon fiber stiffening rods

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Fig. 4

Wings designed, built, and characterized to determine the effects of solar cell integration on flight endurance for Robo Raven

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Fig. 5

Test stand with residual thrust and lift directions identified. The ATI Mini40 6DOF load cell is capable of measuring up to 40 N of force with a resolution of 0.01 N in the thrust direction and 120 N of force with a resolution of 0.02 N in the lift direction.

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Fig. 6

Load cell results and subsequent changes in payload capacities compared to predicted results from models for different wing designs: (a) residual thrust, (b) aerodynamic lift, (c) percentage difference in payload relative to wing A at 3.5 Hz. Mass of each single wing: Wing A = 19.3 g, wing AS = 45.2 g, wing B = 25.4 g, and wing BS = 50.0 g.

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Fig. 7

Solar cell tail designs that were tested: (a) tail 1, (b) tail 2, (c) tail 3, and (d) tail 4 (dimensions in cm)

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Fig. 8

Comparison of the drag from each tail design while wings are stationary and vehicle at a 0 angle of attack

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Fig. 9

Comparison of the residual thrust from each tail design while wings are flapping and vehicle pitched at 20 deg

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Fig. 10

Comparison of the lift from each tail design while wings are flapping and vehicle is pitched at 20 deg. Mass of each tail: tail 0 = 6.2 g, tail 1 = 16.0 g, tail 2 = 13.1 g, tail 3 = 17.0 g, and tail 4 = 14.0 g.

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Fig. 11

Two different design configuration for integrating six additional solar cell modules: (top) two modules in body, four modules in tail; (bottom) three modules in body, three modules in tail

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Fig. 13

Recharging circuit that regulates voltage going to the battery for safe recharging where 4.2 V are supplied to the battery at the blue node and 8.4 V are supplied at the red node

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Fig. 14

Comparison of recharging results

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Fig. 15

Alternative thin film solar cell technologies: (left) gallium arsenide, (middle) polycrystalline, and (right) amorphous silicon

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