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.
Legged locomotion Legged robots may have one, two, four, six, 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 robot and Cheetah are the two fastest running robots so far. 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 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. 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. 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 could 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. Being inspired from geckos, scientists from Stanford university have artificially created 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 a spring will create a stress which bends these microfibers and increase their contact area to the surface of a glass or wall. Using the same technology, gecko grippers were invented by NASA scientists for different applications in space. Stickybots use directional dry adhesives that works best on smooth surfaces. The Spinybot and RiSE robots 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.
Bharals,
hares,
kangaroos,
grasshoppers,
fleas, and
locusts are among the best jumping animals. A miniature 7g jumping robot inspired by locusts has been developed at EPFL that can jump up to 138 cm. 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). 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 and
laughing gas. 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)==