Messages in this thread | | | Date | Tue, 24 Feb 2015 14:21:26 -0400 | From | Eduardo Valentin <> | Subject | Re: [PATCH v1 4/7] thermal: introduce the Power Allocator governor |
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Javi,
One minor clarification as follows:
On Wed, Jan 28, 2015 at 05:00:35PM +0000, Javi Merino wrote:
<big cut>
> + > +k_d > +--- > + > +`k_d` configures the PID loop's derivative term constant. It's > +recommended to leave it as the default: 0. > +
I know we are considering K_d = 0. However, ...
<yet another big cut>
> + /* > + * Calculate the derivative term > + * > + * We do err - prev_err, so with a positive k_d, a decreasing > + * error (i.e. driving closer to the line) results in less > + * power being applied, slowing down the controller) > + */ > + d = mul_frac(tz->tzp->k_d, err - params->prev_err);
... Shouldn't the above d component consider the rate of changes over time of the error?
I would expect you should do: d = k_d * (dE / dt)
or
d = K_d * ((err - params->prev_err) / sampling_period)
in plain C:
+ d = mul_frac(tz->tzp->k_d, err - params->prev_err); + d /= tz->passive_polling; /* might require fixed point division */
--- Eduardo Valentin [unhandled content-type:application/pgp-signature] | |