Instead of having a separate PID component with auto tuning support,
it is easier for users to have only one PID component where auto
tuning is a runtime option for those that want to use it.
Drop the at_pid HAL component and move its implementation and
documentation into the pid HAL component. The code is marked
using #ifdef AUTO_TUNING to make it easy to identify in the code,
and trivial to compile out for those that want to.
There is some questions on how useful and efficient the implemented
auto tuning method is, and while I am sure it can be improved, it
did work for my machie and provided useful Pgain, Igain and Dgain
values for my X and Y axis. As it is a runtime option, those
that do not want automatic tuning can simply ignore this feature.
Keep the at_pid(9) manual page to let earlier users know to use
the pid component instead.
groff treats '-' (the character you get when you hit the "minus" key on
the keyboard) as "hyphen", not as "minus". Thus it renders incorrectly
in some locales, and line-wraps strangely.
groff treats the two-character sequence "\-" as "minus", and the
four-character sequence "\(hy" as "hyphen".
Details here: https://lists.debian.org/debian-devel/2003/03/msg01481.html
This commit replaces every instance of "-" in our manpages where the
meaning is "minus" with "\-", so it works right.
This fixes many lintian warnings.
One problem frequently identified with pid is that the D term is
excessively noisy due to quantization (particularly of feedback position).
Introduce command-deriv and feedback-deriv pins. These can be connected
to some (hopefully superior) source of the derivative. For example, a
system with an analog tach signal in hal could use that value for
feedback-deriv. It also becomes easier to test different derivative
computation functions, such as explicit smoothing of the D term or
the five-point method mentioned on wikipedia
http://en.wikipedia.org/wiki/Numerical_differentiation#Higher_order_methods
Zero, one, or both of the -deriv pins may be connected. When a -deriv
pin is not connected, the related value input is computed by the
traditional two-point difference method. This means that when neither
pin is connected the behavior is the same as before (except for rounding
differences).
pid saturation is another way to detect a fault in the servo amplifier or feedback. the exact policy for fault detection via saturation is left to the integrator.
