If users are attempting to use the output range to limit the controller
action, they should use ProfiledPIDController instead. If they actually
intended to clamp the output, they should use std::clamp().
It breaks the unit system badly; the tolerance member variable has
different units depending on percent vs absolute. Absolute tolerance is
a lot more natural than percent tolerance anyway.
Teams that wish to use it asynchronously may still do so - they simply need to handle the thread safety themselves (it is not that difficult, and can be done more cleanly in the calling code anyway).
Originally, PIDController used PIDSource with its "PIDSourceType" to
determine whether a class should return position or velocity to the
controller. However, the supported languages have changed a lot over 10
years and now support lambdas. Instead of using PIDSource and PIDOutput,
users can pass in doubles to the Calculate() function synchronously.
This makes the controller much more flexible for team's needs as they no
longer have to make a separate PIDSource-inheriting class just to
provide a custom input.
The built-in feedforward was removed. Since PIDController is synchronous
now, they can add their own feedforward on top of what Calculate()
returns.
To facilitate running the controller asynchronously, there is a
PIDControllerRunner class that handles that. By separating the loop from
the control law, PIDController can now be composed with others and be
used to control a drivetrain (a multiple input, multiple output system
that requires summing the results from two controllers) much easier.
Also, motion profiling can be used to set the reference over time.
All the classes related to the old PIDController are now deprecated. The
new classes are in an experimental namespace to avoid name conflicts.
While this is a large change, I think it is a necessary one for growth.
The old PIDController design was created in a time when languages only
supported OOP, and we have more tools at our disposal now to solve
problems. This more versatile implementation can be used in more places
like as a replacement for Pathfinder's "EncoderFollower" class.
There has been hesitation to add lambda support to WPILib for a while
now out of concerns for requiring teams to learn more features of C++ or
Java. In my opinion, this change makes PIDController easier to use, not
harder. The concept of a function is a building block of OOP and should
be learned before classes. The ability to store functions as first-class
objects and invoke them just like variables is rather natural.
Note that PID constants for the new controller will be different from
the old one. The original controller didn't take the discretization
period into account. To fix this, teams should just have to divide their
Ki gain by 0.05 and multiply their Kd gain by 0.05 where 0.05 is the
original default period.
* Update MSVC arguments
* Fix json allocator
* Fix simulation diamond
* Bump gtest
* Remove empty varargs in unit tests
* Replace test case with test suite
* Remove deprecation warning in optional
* Remove need for NOMIXMAX to be defined in wpilib headers
The old headers were moved into folders because doing so avoids polluting
the system include directories.
Folder names were also normalized to lowercase.
