10387Re: [SeattleRobotics] Johnny5 head control
- Mar 1, 2002Bob and the SRS,
You sent the following: "Tom Carroll should step into this
discussion. He's developed several robots for Hollywood including "Number 5"
for the movie Short Circuit. Tom where are you?"
Well, I decided to sit back and watch the different responses,
rather than doing my usual bit of purposely placing a lively bit of
controversy on the list server and watching the resulting flames. But, you
forced my hand, Bob.
I've been reading the comments about the Short Circuit #5 and the "so
called" actuator cylinders. This multi-million dollar project by Gary
Foster, Dennis Jones, Aric Allerd and others used lots of small players like
me to do sub-systems. I was a full-time engineer at Rockwell at the time
doing space robotics for NASA. If I recall, those cylinders were dampers
used as props to simulate actuators. To use pneumatics on a mobile prop is
quite difficult and noisy. I've seen the robot "opened up for all its glory"
and I believe the head actuation used an x-y joint with some rather large
gearmotors attached to move that heavy head. As you might remember, #5 had
a rather large head with some very heavy surplus optical lens assemblies with
the motorized irises.
If the person trying to duplicate the 'apparent motion" of two linear
actuators, he could use a better version of the "string method" mentioned
later in the responses. Using two sail winch servos made for R/C sail boats
and a small diameter steel cable to pull the head in two axes, and using
springs to counterbalance the mass of the head, I think he could pull off
this head control quite well. He could use the 1-2 ms pulse train to control
it with R/C, or use a microcontroller and two sets of "H" bridges to control
a modified set of servos with software.
Anyway, that's my two bits,
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