The implementation of wpi::circular_buffer has been effectively replaced
with a dynamically sized copy of wpi::static_circular_buffer with a
resize() member function.
The units for angular Kv and Ka were inconsistent with the derivation. A
second factory function overload was added for angular units that uses a
trackwidth to convert to the other form.
Notice how section 15.2 of https://file.tavsys.net/control/controls-engineering-in-frc.pdf
defines the angular feedforward as u = Kv,angular v instead of u = Kv,angular + omega.
The units cancel for elements of A but not B, so just the B matrix was incorrect in our code.
This breaks existing C++ code since the units are part of the function
signature.
There were three options for where to put this function:
1. A free function in LinearQuadraticRegulator.h. Returning a K matrix
means the user can't use the LinearQuadraticRegulator in a loop
anymore.
2. A default argument added to ctors in LinearQuadraticRegulator for a
time delay (default of 0). This has the smallest API footprint from
the user perspective, but it bloats the already substantial
constructor overload set of LinearQuadraticRegulator.
3. A member function in LinearQuadraticRegulator that modifies the
internal K. This would still have to take in a LinearSystem or (A, B)
pair because the ctor doesn't store it. Storing it internally feels
like paying for what we don't use most of the time.
I went with option 3.
I verified the tests's expected values in Python with
scipy.linalg.fractional_matrix_power().
Closes#2877.
The wpimath library is a new library designed to separate the reusable math functionality
from the common utility library (wpiutil) and the hardware-dependent library (wpilibc/j).
Package names / include file names were NOT changed to minimize breakage. In a future year
it would be good to revamp these for a more uniform user experience and to reduce the risk
of accidental naming conflicts.
While theoretically all of this functionality could be placed into wpiutil, several pieces
of this library (e.g. DARE) are very time-consuming to compile, so it's nice to avoid this
expense for users who only want cscore or ntcore. It also allows for easy future separation
of build tasks vs number of workers on memory-constrained machines.
This moves the following functionality from wpiutil into wpimath:
- Eigen
- ejml
- Drake
- DARE
- wpiutil.math package (Matrix etc)
- units
And the following functionality from wpilibc/j into wpimath:
- Geometry
- Kinematics
- Spline
- Trajectory
- LinearFilter
- MedianFilter
- Feed-forward controllers
