I have been working on a humanoid robot for some time and was able to get the protoype finger to move fast enough to strip the gearing from its servo. The finger·is controlled via fish line (50lb test) to contract and rubber bands to pull it straight.·Motion control has been tested to much better then .10 of a second. The original prototype is made out of 1 inch wood doll rod with metal eyelets for cable running and rubber band attachment.
Plans are already made to build a finger from PVC and run cables via the interior. PVC was chosen as the second version because of its light weight, cheap costs and availability. Version 3 is in the works which will be built out of milled aluminum, but is not now being built·because of re-occuring issues of the fish line getting stuck if the finger is in the wrong position. This probelm was solved by restringing the fishline through washers. Crude but effective. Version two is meant to work out design flaws prior to makeing version 3 which will cost more.
There is nothing special about·the programing other then bumping up the PWM to around 5. The BS2 so far has been able to complete all opperations. The servo holds the finger nicely and the tension from the rubber bands allows the hand to curl like a humans when not in use.
Cables with servos were selected·over motors, pnumatics· and hydraluic power for several reasons. Motors are harder to locate in the space of a humanoids hand or arm and get them to function correctly. Pnumatics (Air Power) was rejected because of complexities involved with valves, locations to place the compressor, power·and bounce. Pnumatics have power and speed but wear out faster and when contracting will stop and bounce back and forth slightly. Hudraluics were rejected for lack of space for the pump, power usage and valves. Because of these things cables with servos were selected even though the stringing of cables can get complexe at times. The other benefit is that cables and servos are easy to come by where getting small valves and cylinders can be challenging at best. Research into using pnumatics or hydraluics included checking out pricing for unusual parts and it was found to be rather high.
Post Edited (AIman) : 10/9/2006 7:37:28 PM GMT