Biologically inspired technologies for aeronautics
Through evolution and employing principles of all the science and engineering fields, Nature addressed its challenges by trial and error and came up with inventions that work well and last. Technology inspired by Nature is known as biomimetics and offers enormous potential for many exciting capabilities. Biomimetics can be as simple as copying fins for swimming, and is providing numerous benefits, including the development of prosthetics that closely mimic real limbs. The focus of this chapter is on the aerospace-related innovations that were inspired by Nature, and it covers various examples, the potentials and the challenges.
Nature is a self-maintained experimental laboratory that is addressing its changing challenges through the trial-and-error process of evolution. In performing its experiments every field of science and engineering nature is involved, with testing the principles of physics, chemistry, mechanical engineering, materials science, mobility, control, sensors, and many others. Also, the process involves scaling from the nano and macro scales, as in the case of bacteria and viruses, to the macro and mega scales, including the scale of our lives and that of the whales. The extinction of the dinosaurs may suggest that mega-scale land-living animals are an unsustainable form of life as opposed to mega-size sea creatures such as the whales. Observing and studying the capabilities of living creatures suggest numerous possibilities that can be adapted to solve and support human needs. Nature has always served as a model for mimicking and an inspiration to humans in their efforts to improve the way we live. The subject of copying, imitating, and learning from biology is also known as biomimetics and it represents the studies, imitation and inspiration of Nature’s, methods, designs and processes (Bar-Cohen, 2005; Benyus, 1998; Schmitt, 1969; Vincent, 2001; Vogel, 2003). Some of the capabilities were copied from Nature, while for others it served as an inspiring model. Flying was inspired by insects and birds using human-developed capabilities, whereas the design and function of fins, which divers use, were copied from the legs of water creatures such as the seal, goose and frog. Scientific approaches are helping humans understand Nature’s capabilities and the associated principles, resulting in the development of effective tools, algorithms, approaches and other capabilities to benefit mankind. The ultimate goal of biomimetics may be the development of life-like robots that appear and function like humans. Efforts are currently underway to develop such robots, and impressive capabilities have already been reported where human-like robots can conduct conversation with limited vocabulary and respond to body and facial expressions, as well as avoid obstacles while walking and other capabilities (Bar-Cohen and Hanson, 2009). The focus of this chapter is on biologically inspired innovation in aerospace.
In general, Nature’s materials and processes are far superior to man-made ones. The bodies of biological creatures are laboratories that process chemicals acquired from the surroundings and produce energy, construction materials, multifunctional structures and waste (Mann, 1995; Nemat-Nasser et al., 2004). Some of the capabilities of Nature’s materials include self-replication, reconfigurability, self-healing, and balancing the content of various chemicals, including the pH of fluids, as well as temperature and pressure. Recognizing the advantages of these materials, for thousands of years humans have used them as sources of food, clothing, comfort, construction and many other applications. These materials include fur, leather, honey, wax, milk and silk (Carlson et al., 2005). The need to make these materials in any desired quantity led to developing approaches for enhancing their production from the related creatures as well as producing imitations. Many man-made materials are processed by heating and pressurizing, and this is in contrast to Nature, which uses ambient conditions. Materials such as bone, collagen or silk are made inside the organism’s body using nature-friendly processes with minimal waste, and the resulting strong materials are biodegradable and recyclable by Nature.
Besides the multifunctional structures that make up biological creatures, they also have the capability to produce structures using materials that they make or pick up from the surroundings. The skeletons of animals’ bodies are quite marvellous – they are able to support enormous physical actions even though they are not rigid structures. Also, the produced structures (such as the nest, cocoon’s shell and underground tunnels that gophers and rats build) are quite robust and support the structure’s required function over the duration that it is needed. Often the size of a structure can be significantly larger than the species that builds it, as in the case of the spider’s web. An example of a creature that has a highly impressive engineering skill is the beaver, which constructs dams as its habitat on water streams. The honeycomb is also an inspiring structure, and it provides the bees with a highly efficient packing configuration (Gordon, 1976). Using the same configuration, the honeycomb is used to create aircraft structures benefiting from the low weight and high strength that are obtained. Even plants offer inspiration, where mimicking the adherence of seeds to animals’ fur led to the invention of Velcro and to numerous applications including clothing and electric wire strapping.
The development of biomimetic systems and devices is supported by a growing number of biologically inspired technologies, including artificial intelligence, which mimic the control of biological systems (Amaral et al., 2004; Hecht-Nielsen, 2005; Serruya et al., 2002). The invention of the wheel made the most profound impact on human life, allowing the traverse of enormous distances and performance of tasks that otherwise would have been impossible to perform within the lifetime of a single person. While the wheel enabled enormous capabilities, it has significant limitations when used for mobility in complex terrains that have obstacles. Obviously, legged creatures can operate in many such conditions and in ways far superior to an automobile. Legged robots are increasingly becoming an objective for the developers of robotic machines, and these include even human-like ones (Bar-Cohen and Breazeal, 2003; Bar-Cohen and Hanson, 2009). Generally, the mobility of legged mechanisms currently is enabled via motors. While motors have numerous advantages, since they require gears they are relatively heavy, structurally complex and have many potential points of failure. Advances in electroactive polymers (EAP), also known as artificial muscles, are expected to enable new possibilities for legged robotics, with the potential of turning science fiction ideas into engineering applications (Bar-Cohen, 2004).
As a model for inspiration, it is important to remember that Nature’s solutions are driven by survivability of the fittest, and these solutions are not necessarily optimal for technical performance. Effectively, all organisms need to do is to survive long enough to reproduce. Living systems archive the evolved and accumulated information by coding it into the species’ genes and passing the information from generation to generation through self-replication.
• The dragonfly’s flight performance, its ability to fly backwards, as well as stopping and starting using its relatively small body (Huang and Sun, 2007).
• The toughness of spider silk and the ability of the spider to produce silk at room temperature and pressure conditions (Trotter et al., 2000).
• The navigational capability of the Monarch butterfly, migrating over great distances and reaching targeted locations to which, as an individual, it has never before been. This information is coded into the genes of its small body (Sauman et al., 2005).
• The strength of seashells, which is quite enormous even though they are made of calcium carbonate, which is, effectively, a soft material also known as chalk (Yang, 1995).
The above list is only a small number of examples, and covering them all can be an enormous task, and the challenge to adapt them can be much more complex. This chapter examines various examples that are relevant to aerospace.
Nature and its biological systems were on Earth for many Millions of years before humans reached the level of intelligence that was enough to start making their own tools. In the effort of humans to become domesticated and to minimize their dependence on luck and their harvesting of the surrounding resources, they started seeking to improve the way in which they lived. Observing Nature was part of their daily life and it inspired them with ideas of how to acquire and handle food, how to protect themselves and their resources as well as many other things that were essential to their way of life.
One may wonder how inspiring for human innovation have been the various creatures that lived in their neighborhoods. The presence of spiders in human habitats should have had some inspiring role in making such things as wires, ropes, nets, sieves, screens and woven fabrics. One cannot avoid seeing the similarity of a spider’s web and the fishing net or the screen in screen-doors or even the kitchen sieve, as shown in Fig. 2.1, In addition to the sieve, another inspired tool for application to food handling is the tong, which was probably inspired by the beak of birds, as shown in Fig. 2.2.
From another angle on the subject of biomimetics, one may wonder if all the inventions and tools that are commonly used by humans were inspired by Nature or, perhaps, it was just a coincidence that the solutions have similar features. An example might be the honeycomb, which looks very much the same in the natural and technological versions. In the case of bees, the honeycomb serves as a highly efficient packing container for their offspring and for food storage when their eggs hatch. On the other hand, the honeycomb in aircraft structures provides a highly efficient space filler for parts that is lightweight and has great strength. It is also interesting to note that many mammals are four-legged creatures and that most of our furniture, such as chairs and tables, is supported by four legs (see an illustration of this point in Fig. 2.3). It is hard to believe that all human-made solutions were pure inventions of individuals who ignored what they had seen in Nature and came up with them on their own.
Roboticists are well aware that making robots operate with legs significantly increases their capability and mobility in complex terrains. In recent years, there have been increasing efforts to create legged robots for various applications including space and the military, and examples are shown in Fig. 2.4 and 2.5.
Inspired by insects’ and birds’ ability to fly, the field of aerospace as we know it today uses human-developed technology (Fig. 2.6). The enormous number of species capable of flying suggests that Nature has extensively ‘experimented’ with aerodynamics and has been quite successful. Birds are able to maneuver in flight with quite amazing capabilities, as well as flying while carrying prey that can be quite large and heavy compared with their bodies. They can even catch prey while flying, for example a running rabbit or a swimming fish; they are able to predict their path’s intersection with the hunted creature. This capability to hunt while the hunter and the hunted creature are both moving fast (running, flying, or swimming) is increasingly within the capabilities of military weapons, for example allowing a tank to destroy a moving vehicle while they are both moving quickly. As another example, missiles are used to hit enemy fighter aircraft or other missiles by tracking the moving target and either adjusting the direction in flight or aiming at the moment of launch.
2.6 Inspiration by nature and aerodynamic principles led to the flying capabilities of aircraft such as the supersonic passenger plane, the Concorde. (Source: photographed by the author at the Boeing Aerospace Museum, Seattle, WA.)
Another form of biologically inspired flight for potential future NASA missions is under consideration at the Ohio Aerospace Institute (Fig. 2.7). This study takes into consideration that flying on Mars is much more difficult than on Earth due to the lower air pressure and therefore it is necessary to operate within a very low Reynolds number regime. In addition to this restriction, one needs to take into account the practical size limitations of a vehicle that can be deployed from Earth. An entomopter vehicle was recently proposed that uses biomimetic configuration (http://www.niac.usra.edu/files/studies/abstracts/448Colozza.pdf) and circulation control techniques to achieve substantially higher lift. The concept is based on the use of a micro-scale vortex at the wing’s leading edge as determined in 1994 by Charles Ellington of the University of Cambridge (Scott, 1999). Taking advantage of the lower gravity on Mars, one may be able to develop an insect-inspired flying machine with a size in the range of a meter. For power the wing will be covered with flexible solar cells throughout the structure (Fig. 2.7a). Under a DARPA sponsored study, researchers at the Georgia Tech Research Institute have preliminarily confirmed that this concept may be feasible for operation on Mars, with the vehicle able to take off, fly slowly or hover, and land.
Wagging the tail is the leading form of propulsion in water, and many sea creatures are able to develop significant swimming speeds. Inspired by this propulsion method and using balloon designs, with helium for operation in air, researchers at EMPA, Duebendorf, Switzerland, in collaboration with the Institute of Mechanical Systems of ETH, Zürich, Switzerland, are currently developing such a flying vehicle (Michel et al., 2007). The project objective is to use electroactive polymers emulating muscles to produce a lighter-than-air vehicle (Fig. 2.8). In the first phase, a blimp was developed that has its fins bent to the left and right by EAP-based actuators, allowing the blimp to be steered. The goal is to develop a novel bionic-propelled blimp that is operated like a fish with tail-wagging capability (Fig. 2.9). For this purpose, fluid dynamics, structural mechanics, and flight performance are explored with systematic experimental studies. The commercial application of this technology is the development of larger blimps for use in transportation, observation and reconnaissance, as well as stratospheric platforms.
The dragonfly is an incredible flying insect that can maneuver in air at relatively high speeds. Its capability has been under study for many years in an effort to adapt or inspire aeronautic innovation and solution to existing problems (Huang and Sun, 2007). The dragonfly adjusts the effects of high gravity on its body during its flight and rapidly maneuvers using liquid-filled sacs that surround its cardiac system. This method has inspired the Swiss company Life Support Systems to develop an anti-G suit that allows pilots to fly at high Mach speeds with significantly lower effects on their ability to stay coherent. The developed liquid-filled suit is called Libelle, which means dragonfly in German (http://www.lssag.ch/website%2003%2014.html). Tests of the Libelle suit have shown promise as far as the advantages over pneumatic (compressed air) anti-G suits and they are being tested by several air forces.
Plants use many methods of dispersing their seeds, including being blown in the wind and being shaped in an aerodynamic configuration to enable the largest distance to be traveled. Thus, plant species reduce the danger of crowding a specific type of plant into the same local area, may cause competition over the same resources, as well as being subjected to the same environmental risks that possibly endanger their survival. There are various aerodynamic configurations of seeds, and an example is shown in Fig. 2.10, where the seed of the tree Tipuana tipu (about 6.5 cm long) has a wing that propels it in the wind. It is also interesting to mention the tropical Asian climbing gourd Alsomitra macrocarpa, a tree with a relatively large seed having a 13 cm wingspan. The flight of this seed resembles that of a boomerang, and it is capable of gliding in wide circles through the rain forest. One may see quite a similarity between these seeds and helicopter blades, and it is most likely to have been an inspiration for the design of many aerodynamic parts of aircraft and other human-made flying machines.
Another aerospace-related area that is benefiting from biomimetics is the design and development of potential alternatives for planetary landing of rovers and landers on planets with atmospheres (such as Mars and Venus). Adapting such designs may offer better alternatives to the use of a parachute on Mars and possibly provide a better ability to steer the landing hardware toward selected sites. Some of the issues that are being studied include the determination of the appropriate vehicle size, mass distribution and platform shape to ensure stable autorotation and scalability from operation on Earth to performance on Mars.
The tumbleweed is another plant that offered an inspiring design for planetary mobility that is powered by wind (Wilson et al., 2006). Generally, winds blow throughout Mars and they provide an attractive source for mobilizing a rover by mimicking tumbleweed. As shown in Fig. 2.11, the tumbleweed has inspired a futuristic lander that could one day be used as a vehicle for mobility on Mars for traversing great distances with minimal use of power. At NASA Langley, using three-dimensional dynamic modeling and simulations, Southard et al. (2007) have shown that dispersion and exploration of Mars with tumbleweed rovers is feasible. A likely mission scenario involves an organized search for geologically interesting features using a group of rovers with heterogeneous sensor packages. A tumbleweed rover can potentially travel longer distances and gain access to areas such as valleys and chasms that previously were inaccessible. Varying the location of the mass imbalance is one of the methods currently under consideration for controlling the motion of a wind-blown tumbleweed-like rover.
2.11 Tumbleweed (a) offered an inspiration for a futuristic design of a Mars rover (b). (Source: (b) courtesy of NASA. http://smartmachines.blogspot.com/2007/04/nasas-tumbleweed-inspired-rovers-for.html.)
The manufacture of aerospace structures would benefit greatly if they could be made of materials that have Nature’s characteristics of self-healing, self-replication, reconfigurability, chemical balance, durability and multi-functionality. The advantages of biological and botanical materials were well recognized by humanity, and were used for many applications (Carlson et al., 2005). Learning how to process biologically inspired materials can make our choices greater and improve our ability to create recyclable materials that can better protect the environment. Mimicking natural materials will also benefit humans in many other ways, including the development of more life-like prosthetics, where increasingly artificial parts such as hips, teeth, structural support of bones and others are being produced. There are also many mechanisms that were biologically inspired. Some are discussed below.
Since 1997, the author, members of his group at JPL, and engineers from Cybersonics, Inc. have been involved with research and development of sampling techniques for future in situ exploration of planets in the Universe. The developed techniques are mostly driven by piezoelectric actuators and the Ultrasonic/Sonic Driller/Corer (USDC) in particular (Bao et al., 2003; Bar-Cohen et al., 2005a, 2005b). The general configuration of the USDC allows it to penetrate sub-surfaces to a depth that is no longer than the length of the bit, since the other parts are larger in diameter. In order to reach greater depth with less restriction on the depth, two models of deep drills were conceived that were inspired by the gopher and sand-crab (Bar-Cohen et al., 2005b). A piezoelectric actuator induces vibrations that impact the medium with which it is in contact; and the mechanism consists of a bit with a diameter that is the same as or larger than the actuator. The device that emulates the biological gopher is lowered into the produced borehole, cores the medium, breaks and holds the core, and finally the core is extracted onto the surface. This ultrasonic/sonic device can be lowered and raised from the ground surface via cable as shown in Fig. 2.12. This device was called the Ultrasonic/Sonic Gopher and it was designed analogously to the biological gopher that digs into the ground. It removes the loose soil out of the underground tunnel that it forms, bringing it to the surface, and resumes the process to reach great depths. The Ultrasonic/Sonic Gopher was developed to the level of a prototype and demonstrated at Mount Hood and in Antarctica to perform its intended function. Further, the Ultrasonic/Sonic Crab design emulates the sand crab, which shakes its body to penetrate sand on beaches. This device uses mechanical vibrations on the front surface of the end-effector to penetrate media that consist of loose soil, sand, or particulates. The Ultrasonic/Sonic Crab has not yet been produced; however, its implementation is not expected to pose major technical challenges.
Nature uses many pumping mechanisms that have inspired human-made mechanisms. The most common pumps operate by peristaltic pumping, where liquids are squeezed in the required direction. The lungs pump air in a tidal process using the diaphragm, which allows us to breathe. Pumping via valves and chambers that change volume is found in human and animal hearts, where the chambers expand and contract to allow the flow of the blood. Just as in mechanical pumps, the flow of the blood is critically dependent on the action of the valves in the heart.
Muscles, which are both compliant and linear in behavior (Full and Meijer, 2004), are the actuators of biological systems, allowing all our physical movements. Emulating the characteristics of muscles is important, allowing us to make robots that function with life-like performance. The actuators that are closest to emulating natural muscles are the EAPs, which have emerged in recent years and gained the name ‘artificial muscles’ (Bar-Cohen, 2004). There are many types of EAP materials known today, and most of them emerged in the 1990s. Unfortunately, they are still not generating sufficient forces to perform significant tasks such as lifting heavy objects. In order to help advance the field rapidly, the author initiated and organized in March 1999 the first annual international EAP Actuators and Devices (EAPAD) Conference (Bar-Cohen, 1999). This conference is held annually by the International Society for Optics and Photonics (SPIE) as part of its Smart Structures and Materials Symposium. At the opening of the first conference, he posed a challenge to scientists and engineers worldwide to develop a robotic arm that is actuated by artificial muscles to win an arm-wrestling match against a human opponent (http://ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-armwrestling.htm). The icon of the challenge can be seen in Fig. 2.13, illustrating the wrestling of human with robotic arm driven by artificial muscles.
On 7 March 2005, the author organized the first arm-wrestling match with a human (17-year-old high school female student) as part of the EAP-in-Action Session of the SPIE’s EAPAD Conference. In this contest, three EAP-actuated robotic arms participated and the girl won against all three (Fig. 2.14). Following this match in the second contest, rather than wrestling with a human opponent, the contest consisted of measuring the arm’s performance and comparing the results. A measuring fixture was used to gauge the speed and pulling force. To establish a baseline for comparison, the capability of the above student was measured first and then three participating robotic arms were tested. The second Artificial Muscles Armwrestling Contest was held on 27 February 2006, and the results showed two orders of magnitude lower performance of the arms compared with the student. In a future conference, once advances in developing EAP-actuated arms lead to sufficiently high force, a professional wrestler will be invited for another human/machine wrestling match.
Another form of actuation that was biologically inspired is the movement of the inchworm, a caterpillar of a group of moths called Geomeridae. Emulating the mobility mechanism of this larva or caterpillar led to the development of high-precision motors and linear actuators that are known as inchworms. The forces that are generated by the commercial types of inchworms can reach over 30 N with zero-backlash and high stability. As opposed to biological muscles, the piezoelectric-actuated inchworms have zero-power dissipation when holding position. Inchworm mechanisms have many configurations, with the basic principle using two brakes and an extender. These motors perform cyclical steps, where the first brake clamps onto the shaft and the extender pushes the second brake forward. Clamping the second brake and stretching the extender makes the first step, which is then repeated as many times as needed. Inchworm motors were used already in the Telesat (NASA mission) in the mid-1980s, allowing high-precision articulation in the nanometer range.
It is well recognized that sensors are a critical part of any system, allowing it to monitor its functions and respond to the operation conditions as needed. Sensors emulate the senses in biological creatures, which provide inputs to the central nervous system about the environment around and within their body, and the muscles are then commanded to act after analysis of the received information (Hughes, 1999). Biological sensory systems are extremely sensitive and limited only by quantum effects (Bialek, 1987; Bar-Cohen, 2005). Sensors are widely used and it is not possible to imagine effective operation of any system without them. Pressure, temperature, optical and acoustical sensors are widely in use and continuously being improved in terms of their sensing capability, while reducing their size and consumed power. The eye is emulated by the camera, the whiskers of rodents are emulated with collision avoidance sensors, and acoustic detectors imitate the sonar in bats. Similarly to the ability of our body to monitor the temperature and keep it within healthy, acceptable limits, our homes, offices, and other enclosed areas have environmental controls that allow us to operate at comfortable temperature levels. One of the recent studies related to applications in aerospace includes the development of an artificial fly unmanned aircraft system with combined hearing and vision for navigation to inaccessible locations. This on-going research at the University of Maryland is funded by the US Air Force Office of Scientific Research (AFOSR) (http://www.af.mil/news/story.asp?id=123125017). In this study, the capability of a pair of mechanically-coupled ears that are separated by only 500 microns is being investigated while seeking to incorporate advances in microelectronics and other system-on-a-chip capabilities. This study is focused on the understanding, modeling and emulation of the ability of flies to combine hearing and vision at micro-scale levels as means of rapid flight and response.
Controlling the operation of systems in an automatic way can be limited if simple software with known answers to any of the possibilities is used. Increasingly, systems are being made ‘smart’ using artificial intelligence, where the control algorithms are emulating Nature (Musallam et al., 2004; Mussa-Ivaldi, 2000). The field of AI is providing important tools for making automatic and robotic mechanisms with capabilities such as knowledge capture, representation and reasoning, reasoning under uncertainty, planning, vision, face and feature tracking, language processing, mapping and navigation, natural language processing, and machine learning (Bar-Cohen and Breazeal, 2003; Kurzweil, 1999; Luger, 2001). Generally, AI is a branch of computer science that studies the computational requirements for such tasks as perception, reasoning, and learning, to allow the development of systems that perform these capabilities (Russell and Norvig, 2003). Through improvement of the understanding of human cognition (Hecht-Nielsen, 2005) scientists are able to understand the requirements for intelligence in general, and develop artifacts such as intelligent devices, autonomous agents, and systems that cooperate with humans to enhance their abilities. AI researchers are using models that are inspired by the computational capability of the brain and explaining them in terms of higher-level psychological constructs such as plans and goals.
Creating robots that mimic the shape and performance of biological creatures has always been a highly desirable engineering objective (Bar-Cohen and Breazeal, 2003; Bar-Cohen and Hanson, 2009). The term ‘robot’ refers to a biomimetic machine with human-like features and functions that consist of electro-mechanical mechanisms. Also, it suggests a machine that is capable of manipulating objects and sensing its environment as well as being equipped with a certain degree of intelligence. Searching the Internet for the word robot brings numerous links related to research and development projects that are involved with robots. Manipulator arms that are fixed to a single position and perform such tasks as painting and assembly are part of many production lines, including the manufacture of cars. Rovers that have locomotion with wheels or legs are already being made autonomous, and are able to perform quite sophisticated tasks. These include the Mars Rovers, which have been operating on Mars since 2003 on terrains that are unknown, and they are capable of avoiding obstacles while conducting various tasks in support of the exploration of this planet.
The entertainment and toy industries have greatly benefited from advancement in this technology. Toys that emulate the appearance and movement of such creatures as frogs, fish, dogs and even babies are now supplied by many stores. The higher-end robots and toys are becoming increasingly sophisticated, allowing them to walk and even appear to converse with humans using a limited vocabulary at the level of hundreds of words. Some of these robots can be operated autonomously or can be remotely reprogrammed to change the characteristic behavior. An example of a robot that expresses and reacts to human expressions facially and verbally is Kismet, which was developed at MIT (Bar-Cohen and Breazeal, 2003; Breazeal, 2004). As this technology evolves it is becoming more likely that, in the future, human-like robots may be part of our daily life, operating at our homes and offices and doing work that currently is done by humans. Beside the benefits of this technology there is a need for awareness of the potential risks that these robots may pose due to errors or even malicious intent.
Industry has increasingly benefited from advances in robotics and automation that are biologically inspired (Bar-Cohen, 2000; Bar-Cohen and Breazeal, 2003). Crawlers with the equivalent to legs as well as various manipulation devices are increasingly being used to perform a variety of nondestructive evaluation (NDE) tasks. At JPL, a multifunctional automated crawling system (MACS) was developed to allow rapid scanning of aircraft structures in field conditions (Fig. 2.15). MACS consists of two legs for mobility on structures, with one of the legs designed also to rotate. This crawler performs scanning by ‘walking’ on aircraft fuselages while adhering to the surface via suction cups, and is capable of walking upside down on such structures. Mobility on structures is critically dependent on the capability of the legs to have controlled adherence, and alternative forms that were reported include the use of magnetic wheels and electrostatic fields. The author and his co-investigator (Bar-Cohen and Joffe, 1997) conceived a rover that can operate on ships and submarines using magnetic wheels. Another legged robot is JPL’s STAR, which has four legs and can perform multiple functions (Fig. 2.5), including grabbing objects as well as climbing rocks with the aid of the ultrasonic/sonic anchor on each of the legs (Bar-Cohen, 1999; Bar-Cohen and Sherrit, 2007; Kennedy et al., 2006). This anchor provides the ability to ‘hang onto’ rocks via a mechanism that requires a relatively low axial force to drill into the rocks and then extract the bit. JPL’s legged robots are developed for potential operation on future planetary missions, where a Lemur class robot will be able to autonomously negotiate its way through unknown terrain that is filled with obstacles (Fig. 2.16).
The evolution of Nature over billions of years led to highly effective and reasonably power-efficient biological mechanisms, which are appropriate for the intended tasks and that last (Petr, 1996). Ongoing evolution eliminates failed solutions and often leads to the extinction of specific species that do not survive the changing conditions. As it evolves, Nature archives its solutions in the genes of the creatures that make up the terrestrial life around us. Imitating Nature’s mechanisms offers enormous potential for the improvement of our life and the tools we use. With the capability of today’s science and technology we are significantly more capable of employing, extracting, copying and adapting Nature’s inventions.
Nature offers a model for us as humans in our efforts to address our needs as well as a source for inspiring many human-made devices, processes and mechanisms. By studying Nature from the angle of seeking ideas for biologically inspired technologies many applications can result, including stronger fibers, multifunctional materials, improved drugs, superior robots, and many others. Preventing the loss of Nature’s solutions that managed to survive, at least until we understand them well, is an important aspect of biomimetics, where we need to be assured that species are not extinct since they may harbor inventions that we have not yet appreciated. We can learn manufacturing techniques from animals and plants, such as the use of sunlight and simple production of compounds with no pollution, biodegradable fibers, ceramics, plastics, and various chemicals. One can envisage the emergence of extremely strong fibers that are woven as the spider does, and ceramics that are shatterproof, emulating the pearl, or possibly seashells. Besides providing models, Nature can serve as a guide to determine the appropriateness of our innovations in terms of durability, performance, and compatibility.
The inspiration of Nature on aerospace is expected to continue growing and to enable technological improvements with impacts on every aspect of our lives. Miniature flying devices that are as small as or smaller than a fly, with the speed and performance of a dragonfly, are still a challenge to mimic. However, some of the inspired future capabilities may be considered science fiction in today’s terms, but as we improve our understanding of Nature and develop better capabilities this may become a reality that is closer than we think.
Some of the research reported in this chapter was conducted at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with National Aeronautics and Space Administration (NASA).
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