HEXAPODS

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Robots are working all over the world almost every day to make the lives of humans easier.  Since the advent of microprocessors and computers, the possibilities for Robots to improve our civilisation are that much more.

We already have robot factories churning out cars to a higher standard, than those produced in manned factories.  Simple domestic robots are finding their way onto the market to relieve us of tedious tasks.  This is sure to mean more complex robots will be designed and become cheaper, to in turn, free humans more and more from everyday chores.  Put this emerging technology together with renewable energy, such as solar cells, and the possibilities are endless.  Not only could the world rely on plentiful renewable energy, but we'd have more time to devote to other problem areas in our society.  We could build a higher society where food, energy, healthcare and transport are available to all.  

For the above reasons I believe that we should encourage our children to become the engineers of tomorrow, to build on the current state of the art, to produce practical robotic solutions for our future. NK

"ROBOTS ARE A VALUABLE RESOURCE IN THE MAKING"

Quote: Nelson Kruschandl  January 2005

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 whose locomotion is based on three pair of legs. 

The term commonly refers to robots biologically inspired by Hexapoda locomotion. Hexapod robots are considered to be more stable than bipedal robots because in most cases hexapods are statically stable. Therefore, they do not have to depend on balance mechanisms, although, for a smoother walk, feedback and positive reaction will count for much.

Stewart platforms should not be confused with hexapods in the sense of a kind of six-legged walking robot.  A Stewart platform, is a kind of parallel manipulator using an octahedral assembly of struts. 

Hexapod robots are considered to be more stable than bipedal robots because in most cases hexapods are statically stable. Therefore, they do not have to depend on real-time controllers for standing or walking. Nonetheless, it has been demonstrated that at high walking speeds, insects do depend on dynamic factors.

Biologically Inspired

Insects are chosen as models because their nervous system 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. Insect's walking behaviour and neural architecture are used to improve robot locomotion. Alternatively, biologist use hexapod robots for testing different hypotheses.

Biologically inspired hexapod robots largely depend on the insect specie 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.

Hexapod robots have some clear limitations compared to their biological counterparts. Their morphology is subject to mechanical constrains, like the lack of effective artificial tarsi and unrealistic insect-like actuators. Furthermore, dynamics between insects and mechanical robots differ significantly because of their mass and size. Nonetheless, hexapod robots have demonstrated the ability to complete tasks that wheeled vehicles have failed.


Leg Coordination

Leg coordination refers to the mechanism responsible for controlling leg step transitions (stance and swing); assuring that the body will not tumble. Most approaches try to replicate known insect gaits, e.g. tripod or tetrapod gaits. However, other approaches have been used to find stable gaits; for instance, by running genetic algorithms or optimizing walking energy cost function.

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.


Single Leg Controller

There is no boundary to the complexity of leg morphology. However, legs of those based on insect models usually range from two to six degrees of freedom. Leg segments are typically named after their biologically counterpart; which is similar for most species. From the body to the leg’s tip, segments are known as coxa, femur and tibia; typically the coxa-femur and the femur tibia joint are assumed to be a simple hinge joint. The body-coxa joint model ranges from one to three degrees of freedom, depending on the species and the thoracic segment that leg resides.

Hexapod Walker Robot
( Model Number : RHP-D01 )

Hexapod Walker Robot is quite similar in mechanism as quadruped walker robot, but it has 2 more legs of each 2 degree of freedom. (i.e., totally 6 legs and 2 degree of freedom for each leg) And consequently, 4 more servo motors are equipped. (12 servo motors in total) This robot delivers more stable and natural walking action than quadruped robot. By experiencing this product, users can understand and learn about the moving or walking algorithm. Besides, by using extension module such as proper sensors, etc., you can diversify its movement. That is, if you adopt some sensor module in it, then, the robot moves forward avoiding collision against front obstacles or tracing after some specific objects. Users also can make their own program or modify supplied program with ease.

Features

• Motion control : open loop

• Number of Legs : 6 -Size: W260 x L320 x H150 (mm)

• Weight : 1,925g -Number of Servo Motors : 12 (HS-303) -Servo Voltage : rated for 6vdc at 7.2vdc

• Servo current required (idle) : 10mA each

• Servo current required (moving) : 130mA each

• Servo Torque : 3.5kg-cm at 6.0 volt

• Servo Speed : 0.16sec/60˚ at 6.0 volt

• Overall current draw (standing) : 150 ~ 280mA

• Overall current draw (walking) : 1300mA average

• Board Input Voltage : 5vdc

• CPU : Atmega128

• Program tool : C

• Memory : External Flash Memory 2K (4K Extension Available)

• Power : DC 7.2V

• Size : W260 L320 H150(mm)

• Weight : 1,925g

• Option :
  - D02 : IR communication set added
  - D03 : RF communication set added
  - D04 : RF+IR communication set added Package Contents

• Quadruped Robot Body

• Power supply (5V 6A) -Download Cable -CD including program source, etc.

• IR/RF Trans & Receive Unit (Option) -RS232 communication cable -User manual

http://dajin.en.ec21.com/product detail Hexapod Walker Robot

BIPEDS | HEXAPODS | OCTOPODS | QUADRUPEDS  | TRIPODS

LINK and REFERENCE

• Biological Cybernetics/Theoretical Biology

• Poly-pedal Laboratory at Berkeley

• Hexapod project at the University of Applied Sciences of UA at Hagenberg

This website is Copyright © 1999 & 2008  NJK.   The bird logo and name Solar Navigator are trademarks. All rights reserved.  All other trademarks are hereby acknowledged.       Max Energy Limited is an educational charity.

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