Editing Robot locomotion (section)

== Biologically inspired locomotion  ==
The desire to create robots with dynamic locomotive abilities has driven scientists to look to nature for solutions. Several robots capable of basic locomotion in a single mode have been invented but are found to lack several capabilities, hence limiting their functions and applications. Highly intelligent robots are needed in several areas such as search and rescue missions, battlefields, and landscape investigation. Thus robots of this nature need to be small, light, quick, and possess the ability to move in multiple locomotive modes. As it turns out, multiple animals have provided inspiration for the design of several robots. Some such animals are:

'''Pteromyini (flying squirrels)'''
[[File:Oggetto MuSe 020.JPG|thumb|Illustrative image of the flying squirrel (Pteromyini)]]
[[Flying squirrel|Pteromyini]] (a [[Tribe (biology)|tribe]] made up of flying squirrels) exhibit great mobility while on land by making use of their quadruped walking ability with high-[[Degrees of freedom (mechanics)|degrees of freedom]] (DoF) legs. In air, flying squirrels glide through by utilizing lift forces from the membrane between their legs. They possess a highly flexible membrane that allows for unrestrained movement of the legs.<ref name=":0">{{Cite journal|last1=Shin|first1=Won Dong|last2=Park|first2=Jaejun|last3=Park|first3=Hae-Won|date=July 2019|title=Development and experiments of a bio-inspired robot with multi-mode in aerial and terrestrial locomotion|journal=Bioinspiration & Biomimetics|volume=14|issue=5|pages=056009|doi=10.1088/1748-3190/ab2ab7|pmid=31212268|bibcode=2019BiBi...14e6009S |issn=1748-3190|doi-access=free}}</ref> They use their highly elastic membrane to glide while in air and demonstrate lithe movement on the ground. In addition, Pteromyini are able to exhibit multi-modal locomotion due to the membrane that connects the fore and hind legs which also enhances their gliding ability.<ref name=":0" /> It has been proven that a flexible membrane possesses a higher lift coefficient than rigid plates and delays the angle of attack at which stall occurs.<ref name=":0" /> The flying squirrel also possesses thick bundles on the edges of its membrane, wingtips and tail which helps to minimize fluctuations and unnecessary energy loss.<ref name=":0" /> 
[[File:Platyrrhinus helleri2.jpg|thumb|Image showing the location of the uropatagium]]
Pteromyini are able to boost their gliding ability due to the numerous physical attributes they possess.

The flexible muscle structure serves multiple purposes. For one, the [[Patagium|plagiopatagium]], which serves as the primary generator of lift for the flying squirrel, is able to effectively function due to its thin and flexible muscles.<ref name=":1">{{Cite journal|last1=Thorington|first1=Richard W.|last2=Darrow|first2=Karolyn|last3=Anderson|first3=C. Gregory|date=1998-02-20|title=Wing Tip Anatomy and Aerodynamics in Flying Squirrels|journal=Journal of Mammalogy|volume=79|issue=1|pages=245–250|doi=10.2307/1382860|issn=0022-2372|jstor=1382860|doi-access=free}}</ref><ref name=":2">{{Cite journal|last=Johnson-Murray|first=Jane L.|date=1977-08-20|title=Myology of the Gliding Membranes of Some Petauristine Rodents (Genera: Glaucomys, pteromys, petinomys, and Petaurista)|url=https://academic.oup.com/jmammal/article/58/3/374/888797|journal=Journal of Mammalogy|volume=58|issue=3|pages=374–384|doi=10.2307/1379336|issn=0022-2372|jstor=1379336|url-access=subscription}}</ref> The plagiopatagium is able to control tension on the membrane due to contraction and expansion. Tension control can ultimately help in energy savings due to minimized fluttering of the membrane. Once the squirrel lands, it contracts its membrane to ensure that the membrane does not sag when it is walking.<ref name=":2" />

The propatagium and uropatagium serve to provide extra lift for Pteromyini.<ref name=":2" /> While the propatagium is situated between the head and forelimbs of the flying squirrel, the uropatagium is located at the tail and hind limbs and these serve to provide the flying squirrel with increased agility and drag for landing.<ref name=":2" />

Additionally, the flying squirrel possesses thick rope-like muscle structures on the edges of its membrane to maintain the shape of the membranes.<ref name=":2" /> These muscular structures called platysma, tibiocarpalis, and [[Semitendinosus muscle|semitendinosus]], are located on the propatagium, plagiopatagium and uropatagium respectively.<ref name=":2" /> These thick muscle structures serve to guard against unnecessary fluttering due to strong wind pressures during gliding hence minimizing energy loss.<ref name=":2" />

The wingtips are situated at the forelimb wrists and serve to form an [[airfoil]] which minimizes the effect of [[Lift-induced drag|induced drag]] due to the formation of [[wingtip vortices]].<ref name=":1" /> The wingtips dampen the effects of the vortices and obstruct the induced drag from affecting the whole wing. Flying squirrels are able to unfold and fold their wingtips while gliding by using their thumbs. This serves to prevent undesired sagging of the wingtips.<ref name=":1" />

The tail of the flying squirrel allows for improved gliding abilities as it plays a critical role. As opposed to other vertebrates, Pteromyini possess a tail that is flattened to gain more aerodynamic surface as they glide.<ref>{{Cite journal|last=Norberg|first=Ulla M.|date=1985-09-01|title=Evolution of Vertebrate Flight: An Aerodynamic Model for the Transition from Gliding to Active Flight|journal=The American Naturalist|volume=126|issue=3|pages=303–327|doi=10.1086/284419|s2cid=85306259|issn=0003-0147}}</ref><ref>{{Cite journal|last1=Paskins|first1=Keith E.|last2=Bowyer|first2=Adrian|last3=Megill|first3=William M.|last4=Scheibe|first4=John S.|date=2007-04-15|title=Take-off and landing forces and the evolution of controlled gliding in northern flying squirrels Glaucomys sabrinus|journal=Journal of Experimental Biology|volume=210|issue=8|pages=1413–1423|doi=10.1242/jeb.02747|issn=0022-0949|pmid=17401124|doi-access=free}}</ref> This also allows the flying squirrel to maintain pitch angle stability of its tail. This is particularly useful during landing as the flying squirrel is able to widen its pitch angle and induce more drag so as to decelerate and land safely.<ref name=":2" />

Furthermore, the legs and tail of Pteromyini serve to control their gliding direction. Due to the flexibility of the membranes around the legs, the chord angle and dihedral angle between the membrane and coronal plane of the body is controlled.<ref name=":0" /> This allows the animal to create rolling, pitching, and yawing movements which in turn control the speed and direction of the gliding.<ref name=":3">{{Cite journal|last=Bishop|first=Kristin L.|date=2006-02-15|title=The relationship between 3-D kinematics and gliding performance in the southern flying squirrel, Glaucomys volans|journal=Journal of Experimental Biology|volume=209|issue=4|pages=689–701|doi=10.1242/jeb.02062|issn=0022-0949|pmid=16449563|doi-access=free}}</ref><ref name=":4">{{Cite journal|last=Bishop|first=Kristin L.|date=2007-08-01|title=Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps)|journal=Journal of Experimental Biology|volume=210|issue=15|pages=2593–2606|doi=10.1242/jeb.002071|issn=0022-0949|pmid=17644674|doi-access=free}}</ref> During landing, the animal is able to rapidly reduce its speed by increasing drag and changing its pitch angle using its membranes and further increasing air resistance by loosening the tension between the membranes of its legs.<ref name=":3" /><ref name=":4" />

'''Desmodus Rotundus (vampire bat)'''
[[File:Desmodus rotundus 1.jpg|thumb|Image showing the Desmodus Rotundus (vampire bat)]]
The common [[vampire bat]]s are known to possess powerful modes of terrestrial locomotion, such as jumping, and aerial locomotion such as gliding. Several studies have demonstrated that the morphology of the bat enables it to easily and effectively alternate between both locomotive modes.<ref name=":5">{{Cite journal|last1=Woodward|first1=Matthew A.|last2=Sitti|first2=Metin|date=2014-09-04|title=MultiMo-Bat: A biologically inspired integrated jumping–gliding robot|journal=The International Journal of Robotics Research|volume=33|issue=12|pages=1511–1529|doi=10.1177/0278364914541301|s2cid=206500583|issn=0278-3649}}</ref> The anatomy that aids in this is essentially built around the largest muscle in the body of the bat, ''pectoralis profundus'' (posterior division).<ref name=":5" /> Between the two modes of locomotion, there are three bones that are shared. These three main bones are integral parts of the arm structure, namely the humerus, ulna, and radius. Since there already exists a sharing of components for both modes, no additional muscles are needed when transitioning from jumping to gliding.<ref name=":5" /> 
[[File:Schistocerca gregaria - normal.jpg|thumb|Image showing the schistocerca gregaria (desert locust)]]
A detailed study of the morphology of the shoulder of the bat shows that the bones of the arm are slightly sturdier and the ulna and the radius have been fused so as to accommodate heavy reaction forces from the ground<ref name=":5" />

'''Schistocerca gregaria (desert locust)'''

The [[desert locust]] is known for its ability to jump and fly over long distances as well as crawl on land.<ref>{{Cite journal|last1=Rillich|first1=Jan|last2=Stevenson|first2=Paul A.|last3=Pflueger|first3=Hans-Joachim|date=2013-05-09|title=Flight and Walking in Locusts–Cholinergic Co-Activation, Temporal Coupling and Its Modulation by Biogenic Amines|journal=PLOS ONE|volume=8|issue=5|pages=e62899|doi=10.1371/journal.pone.0062899|issn=1932-6203|pmc=3650027|pmid=23671643|bibcode=2013PLoSO...862899R|doi-access=free}}</ref> A detailed study of the anatomy of this organism provides some detail about the mechanisms for locomotion. The hind legs of the locust are developed for jumping. They possess a semi-lunar process which consists of the large extensor tibiae muscle, small flexor tibiae muscle, and banana-shaped thickened cuticle.<ref name=":6">{{Cite web|url=https://www.st-andrews.ac.uk/~wjh/jumping/index.html|title=How Grasshoppers Jump|website=www.st-andrews.ac.uk|access-date=2019-11-04}}</ref><ref name=":7">{{Cite journal|last1=Truong|first1=Ngoc Thien|last2=Phan|first2=Hoang Vu|last3=Park|first3=Hoon Cheol|date=2019-03-13|title=Design and demonstration of a bio-inspired flapping-wing-assisted jumping robot|journal=Bioinspiration & Biomimetics|volume=14|issue=3|pages=036010|doi=10.1088/1748-3190/aafff5|pmid=30658344|bibcode=2019BiBi...14c6010T |s2cid=58665597 |issn=1748-3190}}</ref> When the tibiae muscle flexes, the mechanical advantage of the muscles and the vertical thrust component of the leg extension are increased.<ref>{{Cite journal|last=Burrows|first=M.|date=1995-05-01|title=Motor patterns during kicking movements in the locust|journal=Journal of Comparative Physiology A|volume=176|issue=3|pages=289–305|doi=10.1007/BF00219055|pmid=7707268|s2cid=21759140|issn=1432-1351}}</ref> These desert locusts utilize a catapult mechanism wherein the energy is first stored in the hind legs and then released to extend the legs.<ref>{{Cite journal|last1=Burrows|first1=Malcolm|last2=Sutton|first2=Gregory P.|date=2012-10-01|title=Locusts use a composite of resilin and hard cuticle as an energy store for jumping and kicking|journal=Journal of Experimental Biology|volume=215|issue=19|pages=3501–3512|doi=10.1242/jeb.071993|issn=0022-0949|pmid=22693029|doi-access=free}}</ref>

In order for a perfect jump to occur, the locust must push its legs on the ground with a strong enough force so as to initiate a fast takeoff. The force must be adequate enough in order to attain a quick takeoff and decent jump height. The force must also be generated quickly. In order to effectively transition from the jumping mode to the flying mode, the insect must adjust the time during the wing opening to maximize the distance and height of the jump. When it is at the zenith of its jump, the flight mode becomes actuated.<ref name=":6" />