Robot Arm

From Merlin Systems Wiki

The Merlin Robot Arm is a product of many years' experience of designing with air muscles.

It is a lightweight, flexible actuator system inspired by the human arm, using air muscle actuators to achieve smoothly controlled movements with built-in force compliance for delicate operations.

(click for hi-res version)

Basic Features:

biologically inspired geometry
3 DOF arm movement, plus servo-motor gripper
force-compliant movement
angular movement up to +/-45degrees in any direction
servo-controlled gripper mechanism (optional)
lift capacity of 200-300g when fully extended (i.e. worst-case)

The Merlin Robotic Arm was designed as an ideal demonstration of the power, robustness and flexibility of air-muscle actuators.

The arm has 6 * 20cm air muscles of standard construction - see Dual Valve Muscle. The muscles are electrically controlled using an MDB Muscle Controller.

the muscles are mounted on the arm itself, demonstrating the considerable power-to-weight advantage of air-muscle actuators
all muscles are arranged in antagonistic pairs, like biological muscles
the main ("lift") muscle is oversize for increased force output

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Demonstration Movies

(all in Quicktime format)

Compliant operation + smooth shoulder movements -- Compliance and Shoulder Motion.MOV (12.4Mb)

All basic movements, plus "Pick-and-Place" demo -- RobotArm PickAndPlace.MOV (27.5Mb)

Forearm Movement, showing antagonistic muscle operation -- Forearm Movement.MOV (6.4Mb)

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Constructional Details

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Shoulder

(click for hi-res version)

the arm mount is a die-cast aluminium box with a flanged base, which can be bolted to any suitable mounting surface
the joint is a plastic ball-and-socket design, with passive rotational compliance
the upper arm is controlled by four muscles mounted on it, providing up/down/left/right control
the four upper-arm "tendons" pass through guide brackets, and terminate on the mount box

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Elbow

(click for hi-res version)
The elbow joint is a simple hinge, with two opposing muscles controlling the flexion

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Gripper

(click for hi-res version)

the wrist mounts a standard servo-controller gripper (optional)
a wrist rotation can also be accommodated (optional - not shown)
(Future development: a soft-operating air-powered gripper can replace - not shown)

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Control Equipment

(click for hi-res version)

the control electronics is contained in a single box with pluggable connectors for the arm connection
air supply is via a 4mm air hose
control is via an ethernet cable
power is provided by a PC ATX power supply
air is supplied by a small compressor (not pictured)

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Kit Inventory

Overview -

a 3-DOF air-controlled mechanical arm, providing over +/-45deg movements in each direction
6 air muscle actuators, providing movement with variable stiffness (compliance)
an MDB Control-based control systems, including PC-ATX power supply
a servo-operated gripper "hand" allowing the arm to pick up small objects
a PC-based manual joystick control program (see Robot Arm Control Software)

Full Component list -

surface mountable "shoulder box", from which the rest depends
2-part, 3-DOF mechanical arm
5x Merlin standard-power 20cm air muscles
1x Merlin high-power 20cm air muscle
servo "gripper" hand (optional)
Merlin servo control board (optional)
Merlin MDB Muscle Controller controller board
service box for all control system components, with pluggable connectors
PC-ATX power supply (12v@1A, 5V@25A minimum)
full electrical control wiring, terminating in pluggable electrical connectors
full flexible airline routing, terminating in a single 4mm air-hose connector
support CD

Further requirements:

small air compressor, suitable for ~5slpm operation ("silent" types can be used, but are more expensive):
(Contact Merlin for separate purchase details)

Optional Extras: