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Robotic Arm Project

A student research project supported by the Drury University Physics Department , in conjunction with the NASA Reduced Gravity Student Flight Opportunities Program.

Construction

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Arm in vertical test position

Each muscle tendon wraps around one of the joints, in its own groove, thus passing from the side with the servo to opposite side where it is fixed to the appropriate arm segment. The biarticular muscles pass around grooves in both the shoulder and elbow joints, thus generating torques on both segments when contraction occurs.

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Breadboard with microcontrollers

The arm is controlled via a microcontroller network composed of two Brainstem modules and one Moto module. The modules communicate thru an IIC interface. Much of the specific communication protocol is encapsulated by the Brainstem API, common to both the Brainstem and Moto modules.

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Brainstem module

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Moto module

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Optical encoder

The optical encoder is attached to the outer pulley. The inner shaft rotates the internal encoder disk.

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Joint pulley with tendon wrapped in groove

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Roller bearings

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Servo for actuating muscle

The muscles are actuated using a simple hobby servo. The servo is controlled directly with a pulse-width-modulated signal from the controller.

Elastic and fishing line used for artificial tendons

The artificial muscle tendons are shown in the figure. The tendons have different elasticities. These are color coded for easier identification. A medium tensile fishing line is used to attach the tendons to the joint connections.