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[wpimath] Add RamseteController comparison to LTV controller docs (NFC) (#5559)

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Tyler Veness
2023-08-24 00:04:54 -07:00
committed by GitHub
parent b3ef536677
commit 7889b35b67
4 changed files with 31 additions and 10 deletions
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14
wpimath/src/main/native/include/frc/controller/LTVDifferentialDriveController.h
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@@ -23,9 +23,17 @@ namespace frc {
/**
* The linear time-varying differential drive controller has a similar form to
* the LQR, but the model used to compute the controller gain is the nonlinear
* model linearized around the drivetrain's current state. We precomputed gains
* for important places in our state-space, then interpolated between them with
* a LUT to save computational resources.
* differential drive model linearized around the drivetrain's current state. We
* precompute gains for important places in our state-space, then interpolate
* between them with a lookup table to save computational resources.
*
* This controller has a flat hierarchy with pose and wheel velocity references
* and voltage outputs. This is different from a Ramsete controller's nested
* hierarchy where the top-level controller has a pose reference and chassis
* velocity command outputs, and the low-level controller has wheel velocity
* references and voltage outputs. Flat hierarchies are easier to tune in one
* shot. Furthermore, this controller is more optimal in the "least-squares
* error" sense than a controller based on Ramsete.
*
* See section 8.7 in Controls Engineering in FRC for a derivation of the
* control law we used shown in theorem 8.7.4.

7
wpimath/src/main/native/include/frc/controller/LTVUnicycleController.h
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@@ -20,8 +20,11 @@ namespace frc {
/**
* The linear time-varying unicycle controller has a similar form to the LQR,
* but the model used to compute the controller gain is the nonlinear model
* linearized around the drivetrain's current state.
* but the model used to compute the controller gain is the nonlinear unicycle
* model linearized around the drivetrain's current state.
*
* This controller is a roughly drop-in replacement for RamseteController with
* more optimal feedback gains in the "least-squares error" sense.
*
* See section 8.9 in Controls Engineering in FRC for a derivation of the
* control law we used shown in theorem 8.9.1.