Bio-inspired robotic locomotion is a fairly new subcategory of bio-inspired design. It is about learning concepts from nature and applying them to the design of real-world engineered systems. More specifically, this field is about making robots that are inspired by

biological Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...

systems, including

Biomimicry Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms "biomimetics" and "biomimicry" are derived from grc, βίος (''bios''), life, and μίμησ ...

. Biomimicry is copying from nature while bio-inspired design is learning from nature and making a mechanism that is simpler and more effective than the system observed in nature. Biomimicry has led to the development of a different branch of robotics called

soft robotics Soft robotics is a subfield of robotics that concerns the design, control, and fabrication of robots composed of compliant materials, instead of rigid links. In contrast to rigid-bodied robots built from metals, ceramics and hard plastics, the ...

. The biological systems have been optimized for specific tasks according to their habitat. However, they are multifunctional and are not designed for only one specific functionality. Bio-inspired robotics is about studying biological systems, and looking for the mechanisms that may solve a problem in the engineering field. The designer should then try to simplify and enhance that mechanism for the specific task of interest. Bio-inspired roboticists are usually interested in biosensors (e.g. eye), bioactuators (e.g.

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

), or biomaterials (e.g.

spider silk Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can ...

). Most of the robots have some type of locomotion system. Thus, in this article different modes of

animal locomotion Animal locomotion, in ethology, is any of a variety of methods that animals use to move from one place to another. Some modes of locomotion are (initially) self-propelled, e.g., running, swimming, jumping, flying, hopping, soaring and gliding. Th ...

and few examples of the corresponding bio-inspired robots are introduced.

Biolocomotion

Biolocomotion or animal locomotion is usually categorized as below:

Locomotion on a surface

Locomotion on a surface may include

terrestrial locomotion Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that in water, with reduced friction being replaced by the increased effects of gravity. As viewe ...

and

arboreal locomotion Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...

. We will specifically discuss about

in detail in the next section.

Locomotion in a fluid

Locomotion in a blood stream or cell culture media swimming and flying. There are many swimming and flying robots designed and built by roboticists. Some of them use miniaturized motors or conventional MEMS actuators (such as piezoelectric, thermal, magnetic, etc),R. Fearing, S. Avadhanula, D. Campolo, M. Sitti, J. Jan, and R. Wood, "A micromechanical flying insect thorax," Neurotechnology for Biomimetic Robots, pp. 469–480, 2002.G. Dudek, M. Jenkin, C. Prahacs, A. Hogue, J. Sattar, P. Giguere, A. German, H. Liu, S. Saun- derson, A. Ripsman, et al., "A visually guided swimming robot," in IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS, pp. 3604–3609, 2005.A. Alessi, A. Sudano, D. Accoto, E. Guglielmelli, "Development of an autonomous robotic fish," In Biomedical Robotics and Biomechatronics (BioRob), 2012 4th IEEE RAS & EMBS International Conference on (pp. 1032-1037). IEEE. while others use animal muscle cells as motors.

Behavioral classification (terrestrial locomotion)

There are many animal and insects moving on land with or without legs. We will discuss legged and limbless locomotion in this section as well as climbing and jumping. Anchoring the feet is fundamental to locomotion on land. The ability to increase traction is important for slip-free motion on surfaces such as smooth rock faces and ice, and is especially critical for moving uphill. Numerous biological mechanisms exist for providing purchase: claws rely upon friction-based mechanisms; gecko feet upon van der walls forces; and some insect feet upon fluid-mediated adhesive forces.R. M. Alexander, Principles of animal locomotion. Princeton University Press, 2003

Legged locomotion

Legged robots may have one,M. H. Raibert, H. B. Brown, "Experiments in balance with a 2D one-legged hopping machine," ASME Journal of Dynamic Systems, Measurement, and Control, pp75-81, 1984.M. Ahmadi and M. Buehler, "Stable control of a simulated one-legged running robot with hip and leg compliance," IEEE Transactions on Robotics and Automation, vol. 13, no. 1, pp. 96– 104, 1997.P. Gregorio, M. Ahmadi, and M. Buehler, "Design, control, and energetics of an electrically actuated legged robot," IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics, vol. 27, no. 4, pp. 626–634, 1997. two,R. Niiyama, A. Nagakubo, and Y. Kuniyoshi, "Mowgli: A bipedal jumping and landing robot with an artificial musculoskeletal system," in IEEE International Conference on Robotics and Automation, pp. 2546–2551, 2007. four,M. Raibert, K. Blankespoor, G. Nelson, R. Playter, et al., "Bigdog, the rough-terrain quadruped robot," in Proceedings of the 17th World Congress, pp. 10823–10825, 2008. six, or many legsS. Wakimoto, K. Suzumori, T. Kanda, et al., "A bio-mimetic amphibious soft cord robot," Transactions of the Japan Society of Mechanical Engineers Part C, vol. 18, no. 2, pp. 471–477, 2006. depending on the application. One of the main advantages of using legs instead of wheels is moving on uneven environment more effectively. Bipedal, quadrupedal, and hexapedal locomotion are among the most favorite types of legged locomotion in the field of bio-inspired robotics. Rhex, a Reliable Hexapedal robotU. Saranli, M. Buehler, and D. Koditschek, "Rhex: A simple and highly mobile hexapod robot," The International Journal of Robotics Research, vol. 20, no. 7, pp. 616–631, 2001. and CheetahY. Li, B. Li, J. Ruan, and X. Rong, "Research of mammal bionic quadruped robots: A review," in Robotics, IEEE Conference on Automation and Mechatronics, pp. 166–171, 2011. are the two fastest running robots so far. iSprawl is another hexapedal robot inspired by

cockroach Cockroaches (or roaches) are a paraphyletic group of insects belonging to Blattodea, containing all members of the group except termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known ...

locomotion that has been developed at Stanford University.J. Clark, J. Cham, S. Bailey, E. Froehlich, P. Nahata, M. Cutkosky, et al., "Biomimetic design and fabrication of a hexapedal running robot," in Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on, vol. 4, pp. 3643–3649, 2001. This robot can run up to 15 body length per second and can achieve speeds of up to 2.3 m/s. The original version of this robot was pneumatically driven while the new generation uses a single electric motor for locomotion.S. Kim, J. Clark, and M. Cutkosky, "isprawl: Design and tuning for high-speed autonomous open-loop running," The International Journal of Robotics Research, vol. 25, no. 9, pp. 903– 912, 2006.

Limbless locomotion

Terrain involving topography over a range of length scales can be challenging for most organisms and biomimetic robots. Such terrain are easily passed over by limbless organisms such as snakes. Several animals and insects including

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wor ...

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class ...

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sy ...

s, and

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...

s are capable of limbless locomotion. A review of snake-like robots is presented by Hirose et al.S. Hirose, P. Cave, and C. Goulden, Biologically inspired robots: snake- like locomotors and manipulators, vol. 64. Oxford University Press Oxford, UK, 1993 These robots can be categorized as robots with passive or active wheels, robots with active treads, and undulating robots using vertical waves or linear expansions. Most snake-like robots use wheels, which are high in friction when moving side to side but low in friction when rolling forward (and can be prevented from rolling backward). The majority of snake-like robots use either lateral undulation or rectilinear locomotion and have difficulty climbing vertically. Choset has recently developed a modular robot that can mimic several snake gaits, but it cannot perform concertina motion.R. Hatton and H. Choset, "Generating gaits for snake robots: annealed chain fitting and keyframe wave extraction," Autonomous Robots, vol. 28, no. 3, pp. 271–281, 2010. Researchers at Georgia Tech have recently developed two snake-like robots called Scalybot. The focus of these robots is on the role of snake ventral scales on adjusting the frictional properties in different directions. These robots can actively control their scales to modify their frictional properties and move on a variety of surfaces efficiently.H. Marvi, G. Meyers, G. Russell, D. Hu, "Scalybot: a Snake-inspired Robot with Active Frictional Anisotropy," ASME Dynamic Systems and Control Conference, Arlington, VA, 2011. Researchers at CMU have developed both scaled and conventional actuated snake-like robots.

Climbing

Climbing is an especially difficult task because mistakes made by the climber may cause the climber to lose its grip and fall. Most robots have been built around a single functionality observed in their biological counterparts. GeckobotsO. Unver, A. Uneri, A. Aydemir, and M. Sitti, "Geckobot: a gecko inspired climbing robot using elastomer adhesives," in International Conference on Robotics and Automation, pp. 2329–2335, 2006. typically use van der waals forces that work only on smooth surfaces. Being inspired from geckos, scientists from Stanford university have artificially created recreated the adhesive property of a gecko. Similar to seta in a gecko's leg, millions of microfibers were placed and attached to a spring. The tip of the microfiber will be sharp and pointed in usual circumstances, but upon actuation, the movement of spring will create a stress which bends these microfibers and increase their contact area to the surfce of a glass or wall. Using the same technology, gecko grippers were invented by NASA scientists for different applications in space. Stickybots,S. Kim, M. Spenko, S. Trujillo, B. Heyneman, D. Santos, and M. Cutkosky, "Smooth vertical surface climbing with directional adhesion," IEEE Transactions on Robotics, vol. 24, no. 1, pp. 65–74, 2008.S. Kim, M. Spenko, S. Trujillo, B. Heyneman, V. Mattoli, and M. Cutkosky, "Whole body adhesion: hierarchical, directional and distributed control of adhesive forces for a climbing robot," in IEEE International Conference on Robotics and Automation, pp. 1268–1273, 2007.D. Santos, B. Heyneman, S. Kim, N. Esparza, and M. Cutkosky, "Gecko-inspired climbing behaviors on vertical and overhanging surfaces," in IEEE International Conference on Robotics and Automation, pp. 1125–1131, 2008.A. Asbeck, S. Dastoor, A. Parness, L. Fullerton, N. Esparza, D. Soto, B. Heyneman, and M. Cutkosky, "Climbing rough vertical surfaces with hierarchical directional adhesion," in IEEE International Conference on Robotics and Automation, pp. 2675–2680, 2009. andS. Trujillo, B. Heyneman, and M. Cutkosky, "Constrained convergent gait regulation for a climbing robot," in IEEE International Conference on Robotics and Automation, pp. 5243–5249, 2010. use directional dry adhesives that works best on smooth surfaces. SpinybotA. Asbeck, S. Kim, M. Cutkosky, W. Provancher, M. Lanzetta, "Scaling hard vertical surfaces with compliant microspine arrays," The International Journal of Robotics Research, Vol.25, No. 12, pp. 1165-1179, 2006. and the RiSEM. Spenko, G. Haynes, J. Saunders, M. Cutkosky, A. Rizzi, D. Koditschek, et al., "Biologically inspired climbing with a hexapedal robot," Journal of Field Robotics, vol. 25, no. 4-5, pp. 223– 242, 2008. robot are among the insect-like robots that use spines instead. Legged climbing robots have several limitations. They cannot handle large obstacles since they are not flexible and they require a wide space for moving. They usually cannot climb both smooth and rough surfaces or handle vertical to horizontal transitions as well.

Jumping

One of the tasks commonly performed by a variety of living organisms is jumping. Bharal, hares,

kangaroo Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern ...

grasshopper Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago. Grasshopp ...

flea Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, ...

, and

locust Locusts (derived from the Vulgar Latin ''locusta'', meaning grasshopper) are various species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumstanc ...

are among the best jumping animals. A miniature 7g jumping robot inspired by

has been developed at EPFL that can jump up to 138 cm.M. Kovac, M. Fuchs, A. Guignard, J. Zufferey, and D. Floreano, "A miniature 7g jumping robot," in IEEE International Conference on Robotics and Automation, pp. 373–378, 2008. The jump event is induced by releasing the tension of a spring. The highest jumping miniature robot is inspired by the locust, weighs 23 grams with its highest jump to 365 cm is "TAUB" (Tel-Aviv University and Braude College of engineering).V. Zaitsev, O. Gvirsman, U. Ben Hanan, A. Weiss, A. Ayali and G. Kosa, "A locust-inspired miniature jumping robot," in Bioinspiration & biomimetics, 10(6), p.066012. It uses torsion springs as energy storage and includes a wire and latch mechanism to compress and release the springs. ETH Zurich has reported a soft jumping robot based on the combustion of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...

and laughing gas.M. Loepfe, C.M. Schumacher, U.B. Lustenberger, and W.J. Stark, "An Untethered, Jumping Roly-Poly Soft Robot Driven by Combustion," Soft Robotics, Vol. 2, No. 1, pp. 33-41, 2015. The thermal gas expansion inside the soft combustion chamber drastically increases the chamber volume. This causes the 2 kg robot to jump up to 20 cm. The soft robot inspired by a roly-poly toy then reorientates itself into an upright position after landing.

Behavioral classification (aquatic locomotion)

Swimming (piscine)

It is calculated that when swimming some fish can achieve a

propulsive A prokinetic agent (also gastroprokinetic agent, gastrokinetic agent or propulsive) is a type of drug which enhances gastrointestinal motility by increasing the frequency or strength of contractions, but without disrupting their rhythm. They are ...

efficiency greater than 90%. Furthermore, they can accelerate and maneuver far better than any man-made boat or submarine, and produce less noise and water disturbance. Therefore, many researchers studying underwater robots would like to copy this type of locomotion. Notable examples are the Essex University Computer Science Robotic Fish G9, and the Robot Tuna built by the Institute of Field Robotics, to analyze and mathematically model thunniform motion. The Aqua Penguin, designed and built by Festo of Germany, copies the streamlined shape and propulsion by front "flippers" of

penguin Penguins (order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adap ...

s. Festo have also built the Aqua Ray and Aqua Jelly, which emulate the locomotion of manta ray, and jellyfish, respectively. ISplash Robotic Fish

In 2014, ''iSplash''-II was developed by PhD student Richard James Clapham and Prof. Huosheng Hu at Essex University. It was the first robotic fish capable of outperforming real carangiform fish in terms of average maximum velocity (measured in body lengths/ second) and endurance, the duration that top speed is maintained. This build attained swimming speeds of 11.6BL/s (i.e. 3.7 m/s). The first build, ''iSplash''-I (2014) was the first robotic platform to apply a full-body length carangiform swimming motion which was found to increase swimming speed by 27% over the traditional approach of a posterior confined waveform.

Morphological classification

Modular

The modular robots are typically capable of performing several tasks and are specifically useful for search and rescue or exploratory missions. Some of the featured robots in this category include a

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...

inspired robot developed at EPFL that can walk and swim,A. J. Ijspeert, A. Crespi, D. Ryczko and J.-M. Cabelguen, "From swimming to walking with a salamander robot driven by a spinal cord model," Science, vol. 315, num. 5817, p. 1416-1420, 2007. a

inspired robot developed at Carnegie-Mellon University that has four different modes of terrestrial locomotion, and a

inspired robot can run and climb on a variety of complex terrain.

Humanoid

Humanoid robots are robots that look human-like or are inspired by the human form. There are many different types of humanoid robots for applications such as personal assistance, reception, work at industries, or companionship. These type of robots are used for research purposes as well and were originally developed to build better orthosis and prosthesis for human beings. Petman is one of the first and most advanced humanoid robots developed at Boston Dynamics. Some of the humanoid robots such as Honda Asimo are over actuated.K. Hirer, M. Hirose, Y. Haikawa, and T. Takenaka, "The development of honda humanoid robot," in IEEE International Conference on Robotics and Automation, vol. 2, pp. 1321–1326, 1998. On the other hand, there are some humanoid robots like the robot developed at Cornell University that do not have any actuators and walk passively descending a shallow slope.S. Collins, M. Wisse, and A. Ruina, "A three-dimensional passive-dynamic walking robot with two legs and knees," The International Journal of Robotics Research, vol. 20, no. 7, pp. 607–615, 2001.

Swarming

The collective behavior of animals has been of interest to researchers for several years. Ants can make structures like rafts to survive on the rivers.

Fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...

can sense their environment more effectively in large groups. Swarm robotics is a fairly new field and the goal is to make robots that can work together and transfer the data, make structures as a group, etc.E. S ̧ahin, "Swarm robotics: From sources of inspiration to domains of application," Swarm Robotics, pp. 10–20, 2005.

Soft

Soft robotsTrivedi, D., Rahn, C. D., Kier, W. M., & Walker, I. D. (2008). Soft robotics: Biological inspiration, state of the art, and future research. Applied Bionics and Biomechanics, 5(3), 99-117. are robots composed entirely of soft materials and moved through pneumatic pressure, similar to an

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...

starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish a ...

. Such robots are flexible enough to move in very limited spaces (such as in the human body). The first multigait soft robots was developed in 2011R. Shepherd, F. Ilievski, W. Choi, S. Morin, A. Stokes, A. Mazzeo, X. Chen, M. Wang, and G. Whitesides, "Multigait soft robot," Proceedings of the National Academy of Sciences, vol. 108, no. 51, pp. 20400–20403, 2011. and the first fully integrated, independent soft robot (with soft batteries and control systems) was developed in 2015.

References

External links

The Soft Robotics ToolkitBoston Dynamics

Research labs

* ttps://web.archive.org/web/20120415171146/http://polypedal.berkeley.edu/cgi-bin/twiki/view/PolyPEDAL/WebHome Poly-PEDAL Lab (Prof. Bob Full)br>Biomimetic Milisystems Lab (Prof. Ron Fearing)Biomimetics & Dexterous Manipulation Lab (Prof. Mark Cutkosky)Biomimetic Robotics Lab (Prof. Sangbae Kim)Harvard Microrobotics Lab (Prof. Rob Wood)Harvard Biodesign Lab (Prof. Conor Walsh)ETH Functional Material Lab (Prof. Wendelin Stark)Center for Biologically Inspired Design at Georgia TechBiologically Inspired Robotics Lab, Case Western Reserve University

Biorobotics research group (S. Viollet/ F. Ruffier)Institute of Movement Science, CNRS/Aix-Marseille University
(France)
Center for Biorobotics, Tallinn University of TechnologyBioRob EPFL (Prof Auke Ijspeert)
{{robotics Robot locomotion Bionics Bioinspiration