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/tendono pressurized systems

• Bulk of the mechanisms used for actuation not located directly on the robot (manipulator)

• “Backbone” structureo sufficient amount of bending stiffness for

support and maneuverability

Continuum basics

• Conventional manipulator a):o A serial of actuated

jointso 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)

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Elephant’s trunk manipulator:• Hybrid of three

classes• Four sections with

2 DOF actuated with cable servo system = 8 actuable DOF

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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

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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 baro Consturcted by

covering latex tubing with double helical weave, plastic mesh sheath.

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OctArm Continuum manipulator

• first 2 sections with 6 control channels and last two with 2 control channels

• Six actuator designo located at large radiuso higher stiffness and

load capacity

• Three actuatorso closely-spaced

actuatorso high curvature

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References:

o http://www.ces.clemson.edu/~ianw/o OCRobotics