Download Trunk

Continuum manipulator
Ville Rahikka
Manipulator basics
• Basic types of manipulators:
o Discrete (arms)
o Serpentine
• more discrete joints,
redundancy/maneuverability increase
o Continuum
• no discrete joints and rigid links
• bends (trunks, tentacles)
Continuum robot
• Two main methods:
o actuation by cable/tendon
o pressurized systems
• Bulk of the mechanisms used for actuation
not located directly on the robot (manipulator)
• “Backbone” structure
o sufficient amount of bending stiffness for support
and maneuverability
Continuum basics
• Conventional
manipulator a):
o A serial of actuated joints
o Every joint is actuated
and rigidly connected to
the next joint (3 DOF)
• Continuum manipulator
b):
o Torque at the tip,
coupling e.g. springs
transmits the torque to
the other joints (1DOF)
QuickTime™ and a
decompressor
are needed to see this picture.
Elephant’s trunk manipulator:
• Hybrid of three
classes
• Four sections with 2
DOF actuated with
cable servo system
= 8 actuable DOF
QuickTime™ and a
decompressor
are needed to see this picture.
Elephant’s
• Each section is
based on four links
serial connected by
four 2 DOF joints
• Elastic connections
between each joint
thus coupling all the
joints
• Total 32 kinematic
DOF
QuickTime™ and a
decompressor
are needed to see this picture.
Objection:
• ”Cable-tendons must be tensioned or
the cables become snarled or fall off
drive pulleys limiting robot speed”
OctArm Continuum
manipulator
• Air muscle actuators
a.k.a McKibben
actuators
o maximum pressure
8,27 bar
o Consturcted by
covering latex tubing
with double helical
weave, plastic mesh
sheath.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
OctArm Continuum
manipulator
QuickTime™ and a
decompressor
are needed to see this picture.
• first 2 sections with 6
control channels and
last two with 2 control
channels
• Six actuator design
o located at large radius
o higher stiffness and load
capacity
QuickTime™ and a
decompressor
are needed to see this picture.
• Three actuators
o closely-spaced actuators
o high curvature
References:
o http://www.ces.clemson.edu/~ianw/
o OCRobotics