[wpimath] Link to docs on LQR and KF tolerances (#5486)

Fixes #4151.

wpimath/src/main/native/include/frc/controller/LTVDifferentialDriveController.h

@@ -35,6 +35,10 @@ class WPILIB_DLLEXPORT LTVDifferentialDriveController {
   /**
    * Constructs a linear time-varying differential drive controller.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-intro.html#lqr-tuning
+   * for how to select the tolerances.
+   *
    * @param plant      The differential drive velocity plant.
    * @param trackwidth The distance between the differential drive's left and
    *                   right wheels.

wpimath/src/main/native/include/frc/controller/LTVUnicycleController.h

@@ -44,6 +44,10 @@ class WPILIB_DLLEXPORT LTVUnicycleController {
   /**
    * Constructs a linear time-varying unicycle controller.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-intro.html#lqr-tuning
+   * for how to select the tolerances.
+   *
    * @param Qelems The maximum desired error tolerance for each state.
    * @param Relems The maximum desired control effort for each input.
    * @param dt     Discretization timestep.

wpimath/src/main/native/include/frc/controller/LinearQuadraticRegulator.h

@@ -36,6 +36,10 @@ class LinearQuadraticRegulator {
   /**
    * Constructs a controller with the given coefficients and plant.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-intro.html#lqr-tuning
+   * for how to select the tolerances.
+   *
    * @param plant  The plant being controlled.
    * @param Qelems The maximum desired error tolerance for each state.
    * @param Relems The maximum desired control effort for each input.
@@ -50,6 +54,10 @@ class LinearQuadraticRegulator {
   /**
    * Constructs a controller with the given coefficients and plant.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-intro.html#lqr-tuning
+   * for how to select the tolerances.
+   *
    * @param A      Continuous system matrix of the plant being controlled.
    * @param B      Continuous input matrix of the plant being controlled.
    * @param Qelems The maximum desired error tolerance for each state.

wpimath/src/main/native/include/frc/estimator/ExtendedKalmanFilter.h

@@ -52,6 +52,10 @@ class ExtendedKalmanFilter {
   /**
    * Constructs an extended Kalman filter.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-observers.html#process-and-measurement-noise-covariance-matrices
+   * for how to select the standard deviations.
+   *
    * @param f                  A vector-valued function of x and u that returns
    *                           the derivative of the state vector.
    * @param h                  A vector-valued function of x and u that returns
@@ -69,6 +73,10 @@ class ExtendedKalmanFilter {
   /**
    * Constructs an extended Kalman filter.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-observers.html#process-and-measurement-noise-covariance-matrices
+   * for how to select the standard deviations.
+   *
    * @param f                  A vector-valued function of x and u that returns
    *                           the derivative of the state vector.
    * @param h                  A vector-valued function of x and u that returns

wpimath/src/main/native/include/frc/estimator/KalmanFilter.h

@@ -46,6 +46,10 @@ class KalmanFilter {
   /**
    * Constructs a state-space observer with the given plant.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-observers.html#process-and-measurement-noise-covariance-matrices
+   * for how to select the standard deviations.
+   *
    * @param plant              The plant used for the prediction step.
    * @param stateStdDevs       Standard deviations of model states.
    * @param measurementStdDevs Standard deviations of measurements.

wpimath/src/main/native/include/frc/estimator/UnscentedKalmanFilter.h

@@ -58,6 +58,10 @@ class UnscentedKalmanFilter {
   /**
    * Constructs an unscented Kalman filter.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-observers.html#process-and-measurement-noise-covariance-matrices
+   * for how to select the standard deviations.
+   *
    * @param f                  A vector-valued function of x and u that returns
    *                           the derivative of the state vector.
    * @param h                  A vector-valued function of x and u that returns
@@ -78,6 +82,10 @@ class UnscentedKalmanFilter {
    * you have angles in the state or measurements, because they allow you to
    * correctly account for the modular nature of angle arithmetic.
    *
+   * See
+   * https://docs.wpilib.org/en/stable/docs/software/advanced-controls/state-space/state-space-observers.html#process-and-measurement-noise-covariance-matrices
+   * for how to select the standard deviations.
+   *
    * @param f                  A vector-valued function of x and u that returns
    *                           the derivative of the state vector.
    * @param h                  A vector-valued function of x and u that returns