Re: answers cntd.

On Fri, 28 Sep 2001, Cezary Zielinski wrote:

[...]
> The sensor input implements high level feedback - not the servo
> level one. Usually those generators generate trajectories, which can
> be modified by sensor readings. To be strict they generate the next
> target position. As our servo sampling rate is either 1 or 2 ms the
> generator usually performs at the rate of 6 or 8 ms (for the 2 ms
> sampling rate), so its influence on the trajectory is fairly rapid.
>
This is an interesting remark, because I think the way you present it
(which is the `classical' way) doesn't cope well with things like
`adaptive control': the controller changes its parameters based on
feedback through the sensors; and also the next target position can
depend on _instantaneous_ sensor feedback, not on a change in setpoint
that comes 5 sample periods later...

Probably we are again saying the same things but using underdefined
terminology :-) I mean: if you need this instantaneous feedback, it
has to be part of the servo controller, isn't this what you mean?

IF it is, this brings me to another related question/problem, i.e.,
that of the functionality of the trajectory generator: if one uses
sensor feedback to let the servo adapt setpoints, _and_ also in the
generator, how can one make sure that both are not fighting each
other? As far as I see now, this can only be done if the generator
also has to ability to adapt to the sensor results. But then whose
responsibility is it to keep both in sync? These are (some of) the
kinds of problems we are now trying to find a satisfying software
engineering answer to in Leuven...

Herman