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Hexapod (robotics)
Encyclopedia
A six-legged walking robot should not be confused with a Stewart platform
, a kind of parallel manipulator
used in robotics applications.
A hexapod robot is a mechanical vehicle that walks on six legs. Since a robot can be statically stable on three or more legs, a hexapod robot has a great deal of flexibility in how it can move. If legs become disabled, the robot may still be able to walk. Furthermore, not all of the robot's legs are needed for stability; other legs are free to reach new foot placements or manipulate a payload.
Many hexapod robots
are biologically
inspired by Hexapoda
locomotion
. Hexapods may be used to test biological theories about insect locomotion, motor control, and neurobiology.
Hexapod designs vary in leg arrangement. Insect-inspired robots are typically laterally symmetric, such as the RiSE robot at Carnegie Mellon. A radially symmetric hexapod is ATHLETE (All-Terrain Hex-Legged Extra-Terrestrial Explorer) robot at JPL.
Typically, individual legs range from two to six degrees of freedom
. Hexapod feet are typically pointed, but can also be tipped with adhesive material to help climb walls or wheels so the robot can drive quickly when the ground is flat.
most common gaits are as follows:
Gaits for hexapods are often stable, even in slightly rocky and uneven terrain.
Motion may also be nongaited, which means the sequence of leg motions is not fixed, but rather chosen by the computer in response to the sensed environment. This may be most helpful in very rocky terrain, but existing techniques for motion planning are computationally expensive.
is simpler than other animal species. Also, complex behaviours can be attributed to just a few neurons and the pathway between sensory input and motor output is relatively shorter. Insects' walking behaviour and neural architecture are used to improve robot locomotion. Alternatively, biologists can use hexapod robots for testing different hypotheses.
Biologically inspired hexapod robots largely depend on the insect
species used as a model. The cockroach
and the stick insect are the two most commonly used insect species; both have been ethologically
and neurophysiologically
extensively studied. At present no complete nervous system
is known, therefore, models usually combine different insect models, including those of other insects.
Insect gaits are usually obtained by two approaches: the centralized and the decentralized control architectures. Centralized controllers directly specify transitions of all legs, whereas in decentralized architectures, six nodes (legs) are connected in a parallel network; gaits arise by the interaction between neighbouring legs.
Stewart platform
A Stewart platform is a type of parallel robot that incorporates six prismatic actuators, commonly hydraulic jacks. These actuators are mounted in pairs to the mechanism's base, crossing over to three mounting points on a top plate. Devices placed on the top plate can be moved in the six degrees...
, a kind of parallel manipulator
Parallel manipulator
Parallel robots and parallel manipulators are articulated robots that use similar mechanisms for the movement of either the robot on its base, or one or more manipulator arms...
used in robotics applications.
Many hexapod robots
Robotics
Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...
are biologically
Bionics
Bionics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology.The word bionic was coined by Jack E...
inspired by Hexapoda
Hexapoda
The subphylum Hexapoda constitutes the largest grouping of arthropods and includes the insects as well as three much smaller groups of wingless arthropods: Collembola, Protura, and Diplura . The Collembola are very abundant in terrestrial environments...
locomotion
Terrestrial locomotion in animals
Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that on water, with reduced friction being replaced by the effects of gravity....
. Hexapods may be used to test biological theories about insect locomotion, motor control, and neurobiology.
Designs
Typically, individual legs range from two to six degrees of freedom
Degrees of freedom (engineering)
In mechanics, degrees of freedom are the set of independent displacements and/or rotations that specify completely the displaced or deformed position and orientation of the body or system...
. Hexapod feet are typically pointed, but can also be tipped with adhesive material to help climb walls or wheels so the robot can drive quickly when the ground is flat.
Locomotion
Most often, hexapods are controlled by gaits, which allow the robot to move forward, turn, and perhaps side-step. Some of themost common gaits are as follows:
- Alternating tripod: 3 legs on the ground at a time.
- Quadruped.
- Crawl: move just one leg at a time.
Gaits for hexapods are often stable, even in slightly rocky and uneven terrain.
Motion may also be nongaited, which means the sequence of leg motions is not fixed, but rather chosen by the computer in response to the sensed environment. This may be most helpful in very rocky terrain, but existing techniques for motion planning are computationally expensive.
Biologically inspired
Insects are chosen as models because their nervous systemNervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
is simpler than other animal species. Also, complex behaviours can be attributed to just a few neurons and the pathway between sensory input and motor output is relatively shorter. Insects' walking behaviour and neural architecture are used to improve robot locomotion. Alternatively, biologists can use hexapod robots for testing different hypotheses.
Biologically inspired hexapod robots largely depend on the insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
species used as a model. The cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
and the stick insect are the two most commonly used insect species; both have been ethologically
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....
and neurophysiologically
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
extensively studied. At present no complete nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
is known, therefore, models usually combine different insect models, including those of other insects.
Insect gaits are usually obtained by two approaches: the centralized and the decentralized control architectures. Centralized controllers directly specify transitions of all legs, whereas in decentralized architectures, six nodes (legs) are connected in a parallel network; gaits arise by the interaction between neighbouring legs.
List of robots
- DIGbot at Case Western Reserve University and The University of South Florida
- The RiSE robot at Carnegie Mellon
- The ATHLETE rover at JPL
- Autonomous walking machine AMOS
- HexbugHexbug‘’Hexbug’’ is a brand of toy robot developed and distributed by Innovation First, Inc. Hexbug was inspired by BEAM robotics, and uses many elements of it. Originally released in the US through Radio Shack, it is now sold in most major retail stores. The original was based on 6-legged arthropods,...
(insectoid toy robot) - StiquitoStiquitoStiquito is a small, inexpensive hexapod robot commonly used by universities, high schools, and hobbyists, since 1992.Stiquito's "muscles" are made of nitinol, a shape memory alloy that expands and contracts, roughly emulating the operation of a muscle. The application of heat causes a crystalline...
(inexpensive insectoid robot) - Per's Hexapod (hobbyist's prototype robot)
- RhexRhexRHex is a power - and computation - autonomous hexapod robot with compliant legs and only one actuator per leg. It is the first documented autonomous legged machine to have exhibited general mobility over general terrain...
- Amphibious and swimming hexpod
- WhegsWhegsWhegs are a series of robots developed at the Biologically Inspired Robotics Laboratory at Case Western Reserve University. Whegs use a strategy of locomotion that combines the simplicity of the wheel with the obstacle-clearing advantages of the foot....
- LAURONLAURONLAURON is a six-legged walking robot, which is being developed at the Forschungszentrum Informatik Karlsruhe in Germany. The mechanics and the movements of the robot are biologically-inspired, mimicking the stick insect Carausius Morosus....
External links
- Biological Cybernetics/Theoretical Biology
- Poly-pedal Laboratory at Berkeley
- Hexapod project and competition at the University of Applied Sciences of UA at Hagenberg - (German)
- iC Hexapod - An interactive face tracking hexapod robot
- Hexapod Controller - On The Fly Inverse Kinematics - See A-POD
- Spidey - Project at Birla Institute of technology, MESRA, India