This instructable shows the process of building a robotic arm using servos, Arduino microprocessor, a gyroscope and multiple bend sensors.
The user wears a glove containing the gyroscope and bend sensors which translate the movement of the users hand into motion of the servos , in turn rotating the wrist and hand of the robotic arm.
The forearm has full motion of a human wrist namely: rotation, radial deviation (movement towards the thumb) ,ulnar deviation (movement towards the little finger) ,flexion (tilting towards the palm) and extension (tilting towards the back of the hand).
The Hand also has movement of the fingers, this is limited as a result of the brittle material used.
All movement is provided by the Servos attached to an extension wire or piano wire. Each having different torque depending on its position.
The fingers contain touch sensitive resistors which provide haptic feedback and allow the user to know when the fingers have grasped an object.
Step 1: Design
I found this design of the finger on the net which allows a single servo to provide full motion of curl of a human finger.The design works best when Aluminium is used for the cut outs of the fingers, but as I had perspex available I went with the weaker option which resulted in brittle fingers.
All the fingers are the same design but a variation of measurements, except for the thumb. they can be found below:
The designs below are the ones I sent through to a laser cutter here in Johannesburg for about R350 for all cuts and material.
they required the files to be sent in 2d DXF format, so if you alter the design in sketchup, make sure you export it in the correct format.
The rest of the cut outs are made up of wrist and palm sections.
index finger, middle finger, ring finger is roughly the same size.
pinky is slightly smaller than other fingers.
Thumb has different dimentions