[ODE] RC-servo modeling

[Doron Tal]

Howdy,

We need to model an RC servo motor as part of a larger model of an
articulated robot.  We need the RC servo model to be a good
approximation to reality.

The current RC digital servos have a bang-bang controller inside the
servo that keeps the servo arm in one place once it is commanded to go
there.  The bang-bang controller simply checks if the motor overshoots
its position and if so sends the motor in the reverse direction as
fast as possible.

The question is: do we need to model the bang-bang controller inside
each servo, which operates on a fine time scale (microseconds?) and
would be expensive to compute, or can we get by with using the
built-ins of ODE, while still getting a realistic simulation of an
RC-servo?

We need a realistic model, because we are training articulated robots
how to walk and we start by training them in simulation, only later
transferring the learned walking gait to the real robot.  Without a
realistic simulation, the transfer to the real robot may fail..

Any help would be greatly appreciated and if there is enough
advice in the replies to aggregate, I will post a summary of the
replies.

Thanks!
-Doron

-- 
Doron Tal
USRA/RIACS Research Scientist
NASA Ames Research Center
Moffett Field, CA 94035-1000, USA