Excavator

Posted by Will on Jul 23, 2011 in Uncategorized

I’ve had an idea for awhile to build a mini-excavator.  (For a sense of scale the arms are 11″ long.) Nothing past the concept stage yet.  This is designed to use steppers and timing belts to control the three joints.  3mm HTD timing belts, 72 and 15 tooth pulleys.  4.8:1, 23.04:1, and 110.592:1 gear ratios on wrist, elbow and shoulder respectively.  (Double reduction on the elbow and triple reduction on the shoulder.)  I thought about using linear actuators like a real excavator but screw type actuators have limited travel for their overall length and pneumatic or hydraulic cylinders would be more difficult to control electronically.  I need some kind of positioning feedback (linear / rotary encoders or potentiometer) and pulse width modulated valves.  Steppers (with the reduction) will have the torque I need and will be easy to control with no position feedback.