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[DPRG] Velocity Profiling move of RC Servos

Subject: [DPRG] Velocity Profiling move of RC Servos
From: Randy M. Dumse rmd at newmicros.com
Date: Sun Dec 8 13:51:00 CST 2002

Hey All,

One of the outcomes of my recent "Arm in a day" project was
dealing with RC Servos which basically move by position command
and driving them in such as way so they moved as if by velocity
profiling. (I polished up this code today, added the limited
acceleration profiling to the velocity move, and think its
finished, now. The velocity move was done in a day, but the
profiling took more than a day to really smooth up and

In other words, when I make the RC Servos move, I ramped them up
to a maximum speed holding a constant acceleration, hold that
maximum speed, and slowed them down through a constant
decceleration at the end of the move. That's the basic
description of velocity profiling of a move. Of course I was
running open loop, so I was commanding positions for the RC
servo to move to, but updating those continuously so the move
looked smooth, like a real servo under a profiled move command.
(It actually had even thing except the feedback, which is
something I'm working on as well).

So I'm pretty pleased with this accomplishment, and I'm
wondering ...is something everybody else has already done, or
not. Is it old hat? or relatively new (as in generally
unpublished and unknown to treat RC Servos this way)?


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