Bio-inspired robotic locomotion is a fairly new sub-category of bio-inspired design. It is about learning from nature and applying it to the real world engineering systems. More specifically, this field is about making robots that are inspired by the biological systems. Biomimicry and bio-inspired design sometimes get mixed up. Biomimicry is copying the 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. The biological systems have been optimized for specific tasks according to their habitat. However, they are multi-functional and are not designed for only one specific functionality. Bio-inspired robotics is about studying biological systems, and look 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), or biomaterials (e.g. spider silk). Most of the robots have some type of locomotion system. Thus, in this article different modes of animal locomotion and few examples of the corresponding bio-inspired robots are introduced.
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Biolocomotion or animal locomotion is usually categorized as below:
 Locomotion on a surface
 Locomotion in a fluid
 Behavioral classification (terrestrial locomotion)
There are many animal and insects moving on land with or without legs. We will discuss about 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.
 Legged locomotion
Legged robots may have one, two, four, six, or many legs 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 filed of bio-inspired robotics. Rhex, a Reliable Hexapedal robot and Cheetah are the two fastest running robots so far. iSprawl is another hexapedal robot inspired by cockroach locomotion that has been developed at Stanford University. 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.
 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 worms, snails, caterpillars, and snakes are capable of limbless locomotion. A review of snake-like robots is presented by Hirose et al. 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 provide a forward-transverse frictional anisotropy. 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. 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.
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. Geckobots typically use van der waals forces that work only on smooth surfaces. Stickybots, and use directional dry adhesives that works best on smooth surfaces. Spinybot and the RiSE 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.
One of the tasks commonly performed by a variety of living organisms is jumping. Bharal, hares, kangaroo, grasshopper, flea, and locust are among the best jumping animals. A miniature 7g jumping robot inspired by locust has been developed at EPFL that can jump up to 138 cm.
 Morphological classification
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 inspired robot developed at EPFL that can walk and swim, a snake inspired robot developed at Carnegie Melon that has four different modes of terrestrial locomotion, and a cockroach inspired robot can run and climb on a variety of complex terrain.
Humanoid robots are robots that look like human or are inspired by human. There are many different types of humanoid robots for applications such as personal assistance, reception, work at industries, or companionship. This 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. On the other hand, there are some humanoid robots like the root developed at Cornell University that do not have any actuators and walk passively descending a shallow slope.
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 can sense its 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.
Soft robotics is a new field in robotics and the idea is to make all of the components in the robot soft and flexible in order to move in very limited spaces and change gaits fairly easily. This field is inspired by animals such as octopus or starfish. One of the first multigait soft robots is developed at Harvard University and is inspired by starfish.
 See also
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- Poly-PEDAL Lab (Prof. Bob Full)
- Biomimetic Milisystems Lab (Prof. Ron Fearing)
- Biomimetics & Dexterous Manipulation Lab (Prof. Mark Cutkosky)
- Bimimetic Robotics Lab (Prof. Sangbae Kim)
- Harvard Microrobotics Lab (Prof. Rob Wood)
- Leg lab at MIT
- Boston Dynamics
- Center for Biologically Inspired Design at Georgia Tech
- Research for this Wikipedia entry was conducted as a part of a Locomotion Neuromechanics course (APPH 6232) offered in the School of Applied Physiology at Georgia Tech