Digital Control with very low sample rate

Johannes Eble wrote:

What does "regulate fuel consumption" mean? Can your loop be stable if
its output remains constant for two hours?

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

There is no time.
There are only samples.

--
MIkolaj

Johannes Eble wrote:

I've been trying to follow the discussion, but I evidently missed some
critical details.

What can cause the fuel consumption to vary? Does the load vary? Is
there an attempt to keep the engine speed constant?

A system that uses an engine to accomplish a task, in which the
important aspect is fuel consumption rather than the task, seems odd.
More like an accountant's view of the project, rather than an engineer's.

If the system is reasonably linear for small changes, establishing the
system gain can be useful. Keep a record of the last correction applied.
When a new sample is received, calculate the change due to the last
correction, the new correction needed, and from these, the best estimate
of the correction to be applied. This works well when a system
correction will have fully settled before the next correction is
applied. That seems likely in this case.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

On Fri, 10 Jul 2009 13:28:26 -0400, Jerry Avins wrote:


I'm wondering that myself.

I can think of times when you may wish to servo the resource consumption
-- mostly in cases where you're strictly resource-constrained.  A homey
example would be if you're broke (or snowed in) and you're almost out of
heating oil -- it's better to live for a week at 55 degrees F than to
have a nice warm house for three days and then freeze for four.

--
http://www.wescottdesign.com

Hello Tim and Jerry,


Aging of the mechanical system (mainly injectors). In other words, the
plant (or the disturbances) vary, not the setpoint.


Seldom. And if it does, I will deactivate the controller alltogether,
if necessary.


No, it is a stationary engine.


when did I say that?


Well, fuel consumption is an issue, at least in Europe ;-}

The system already fulfills the task, without fuel regulation. But we
are confident that a fuel regulation will mitigate aging.


Good idea. Something like that is what I plan to do now.


Best regards


Johannes