By Vienna Li
- Introduction
In recent years, many scientists have turned to biology for inspiration in designing moving robots. The motion of animals– such as crawling, swimming, leaping, or flying– provides integral insights into furthering technology, especially in aerospace engineering. Whether analyzing how insects respond to information in their environment, or how aquatic animals lower their drag in the water, animals on Earth can carry out tasks with the efficiency that many of our machines are yet to reach.
- History
Following the energy crisis in the 1970s and a dramatic increase in oil prices, many countries sought to incorporate more fuel-efficient techniques into their commercial airplanes. In a study at the Friedberg University of Mining and Technology in Germany, researchers analyzed peregrine falcons and how the shape of their wings affects drag. Using a wind tunnel, the researchers observed the flow of air for different flight configurations and analyzed how falcons increased their maneuverability at high speeds. A few years later, a team of researchers from London conducted a similar study, in which they focused on how the structural aspects of bat wings could optimize their flight efficiency (Budholiya). With the growth of manufacturing methods and rapid increase in bioinspired designs in the aerospace industry, scientists targeted the process, structure, and characteristics that could improve the flight performance of aircraft and other systems.
- Application
The first application of bioinspired concepts in the aerospace sector is wing designs. Taking inspiration from seagulls that could modify their wings to improve their aerodynamic build, engineers implemented the concept by employing lightweight components and an actuator, a system that altered the aircraft wing’s morphology, as seen in Figure 1.
Figure 1 (left). Different wing morphologies. Sourced from MDPI Journal
Figure 2 (right). Design for flexing wings. Sourced from MDPI Journal
By attaching a flapping wing mechanism towards the rear end of a MAV (micro-air vehicles), engineers found that the bio-inspired concept generated the most amount of lift and thrust while also decreasing the drag of the main fuselage, resulting in an efficient design that could reduce the weight and fuel costs. The goal of implementing the flapping motion was to provide airplanes with an aerodynamic benefit similar to that of flying birds through the flexing of the wing, which replaced the traditional, fixed wind element (Figure 2).
Another application of the flapping wing mechanism is to provide necessary defense mechanisms to decrease turbulence during the flight. Birds normally glide or hover to counter turbulence, an action that allows their covert feathers, which help smooth the airflow over the winds), to divert turbulent winds. Scientists have mimicked this process using synthetic mechanisms seen in Figure 3. Similar to the covert feathers, the goal of the flapping wing UAVs is to reduce drag and redirect gusts of wings during turbulence.
Figure 3. Positioning of covert feathers. Sourced from MDPI Journal
- Recent Innovations
Scientists have begun to shift their focus on applying the mysteries of flight performance to real innovations and designs. One such design is morphing surfaces, which allow pilots to have a greater ability to control altitude and replace the traditional stiff hinges employed in modern aircraft. Inspired by the strong yet flexible structures in nature, Sridhar Kota, a professor of mechanical engineering at the University of Michigan, decided to develop aircraft flight control surfaces that could bend and twist by tweaking the positions of the composite beams underneath the surface. Although this application is relatively new, the U.S. The Air Force is planning to test these surfaces on the wings of a KC-135 refueling tanker. In previous years, an earlier version of morphing flaps improved the fuel efficiency of a NASA Gulfstream III jet from 3% to 4% (Tegler). The main feature of these surfaces is that they serve as one continuous surface. Unlike the traditional surfaces, which depend on seams and hinges, flexible surfaces, Kota explains, function like “a bow and arrow”, which essentially allows the machinery to expand and contract, similar to how an archer would pull and release an arrow. So far, engineers are currently in the testing phase for these morphing control surfaces and hope to incorporate them into future aircraft.
Figure 4. (Left) Bow and arrow surface mechanisms. Sourced from NASA’s Glenn Research Center
Figure 5. (Right) Adding winglets to the KC-135 refueling tankers. Sourced from Aerospace America
- Future
With the growth of new technologies and artificial intelligence, bio-inspired designs are rapidly accelerating. From designing simplified models to test patterns observed in nature to creating accurate models to test such motions, the continued expansion of resources resulted in great progress in bionic aerodynamics. However, there are still many aspects of the long development and application process which demand attention, such as simulating mechanisms that model flexible deformations, increasing the precision of such simulations, and constructing large-scale structures.
References
Budholiya, Sejal, et al. “State of the Art Review about Bio-Inspired Design and Applications: An Aerospace Perspective.” Applied Sciences, vol. 11, no. 11, May 2021, p. 5054. Crossref, https://doi.org/10.3390/app11115054. Accessed 25 March 2023
Jan Tegler. “Bio-Inspired.” Aerospace America, AIAA Foundation, 22 Nov. 2021, https://aerospaceamerica.aiaa.org/features/bio-inspired/. Accessed 25 March 2023
Jiakun Han, et al. “Review on Bio-Inspired Flight Systems and Bionic Aerodynamics.” Chinese Journal of Aeronautics, vol. 34, no. 7, 21 June 2021, pp. 170–186., https://doi.org/https://doi.org/10.1016/j.cja.2020.03.036. Accessed 25 March 2023
Savage, Neil. “Bioinspired Robots Walk, Swim, Slither and Fly.” Nature News, Nature Publishing Group, 29 Sep. 2022, https://www.nature.com/articles/d41586-022-03014-x. Accessed 25 March 2023
International Youth Scientists 