Replace old PID library with a new unit tested C++ class

[MaEtUgR]

Solved Problem

When doing heli rpm and boat control I found that there is a PID library in PX4 which is pretty tedious to use.

Solution

I wrote a new one with a C++ interface and unit tests.

Changelog Entry

Replace old PID library with a new unit tested C++ class

Test coverage

I successfully used this library for heli rpm control and boat heading control but without a derivative term. PI control only.
For a more practical derivative implementation it'd need a filter on the derivative and possibly one that considers the change of error not just feedback.

Note that the PID speed control instance in RoverPositionControl supplied a vehicle acceleration but configured the old library with PID_MODE_DERIVATIV_CALC which made it calculate a numerical derivative and ignore the provided acceleration all along:
aef5225#diff-0e5af3f25fa84fecddb10c4607acaf89f788f58553835199b217b5d230dfde14R142

FYI @TomasTwardzik

[chfriedrich98]

LGTM, seems to be a lot easier to implement then the old library.
I just have one fix on the implementation in the ackermann module (which is due to the fact that I had initially implemented the old PID library wrong) and a suggestion on handling the Output/Integral limits.

[github-actions]

FLASH Analysis

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Updated: 2024-11-26T13:10:55

[chfriedrich98]

These changes fix the unit tests, but I also noticed that the integral is delayed in the output by one update step. Is this on purpose?

[MaEtUgR]

Thanks @chfriedrich98 for following up! I didn't even realize the tests were failing 🙈 I accepted both your suggestions but changed them as in having a separate function for the derivative since we'll likely add filtering to it, similar to https://github.com/PX4/PX4-Autopilot/blob/e194a52907083783f7e67ff93504016ca1275ce8/src/lib/mathlib/math/filter/FilteredDerivative.hpp and having the test verify the reset to zero and the first integral update.

[MaEtUgR]

MAVROS fails on every new pr 😬