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[wpimath] Remove RamseteController and RamseteCommand (#7522)

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This commit is contained in:
Tyler Veness
2024-12-07 23:38:35 -08:00
committed by GitHub
parent ae44295024
commit 220f4e1ba4
14 changed files with 8 additions and 996 deletions
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5
wpimath/src/main/java/edu/wpi/first/math/controller/LTVDifferentialDriveController.java
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@@ -27,11 +27,10 @@ import edu.wpi.first.math.trajectory.Trajectory;
* state-space, then interpolate between them with a lookup table to save computational resources.
*
* <p>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
* outputs. This is different from a unicycle 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.
* in one shot.
*
* <p>See section 8.7 in Controls Engineering in FRC for a derivation of the control law we used
* shown in theorem 8.7.4.

3
wpimath/src/main/java/edu/wpi/first/math/controller/LTVUnicycleController.java
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@@ -23,9 +23,6 @@ import edu.wpi.first.math.trajectory.Trajectory;
* compute the controller gain is the nonlinear unicycle model linearized around the drivetrain's
* current state.
*
* <p>This controller is a roughly drop-in replacement for {@link RamseteController} with more
* optimal feedback gains in the "least-squares error" sense.
*
* <p>See section 8.9 in Controls Engineering in FRC for a derivation of the control law we used
* shown in theorem 8.9.1.
*/

174
wpimath/src/main/java/edu/wpi/first/math/controller/RamseteController.java
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@@ -1,174 +0,0 @@
// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
package edu.wpi.first.math.controller;
import edu.wpi.first.math.geometry.Pose2d;
import edu.wpi.first.math.kinematics.ChassisSpeeds;
import edu.wpi.first.math.trajectory.Trajectory;
/**
* Ramsete is a nonlinear time-varying feedback controller for unicycle models that drives the model
* to a desired pose along a two-dimensional trajectory. Why would we need a nonlinear control law
* in addition to the linear ones we have used so far like PID? If we use the original approach with
* PID controllers for left and right position and velocity states, the controllers only deal with
* the local pose. If the robot deviates from the path, there is no way for the controllers to
* correct and the robot may not reach the desired global pose. This is due to multiple endpoints
* existing for the robot which have the same encoder path arc lengths.
*
* <p>Instead of using wheel path arc lengths (which are in the robot's local coordinate frame),
* nonlinear controllers like pure pursuit and Ramsete use global pose. The controller uses this
* extra information to guide a linear reference tracker like the PID controllers back in by
* adjusting the references of the PID controllers.
*
* <p>The paper "Control of Wheeled Mobile Robots: An Experimental Overview" describes a nonlinear
* controller for a wheeled vehicle with unicycle-like kinematics; a global pose consisting of x, y,
* and theta; and a desired pose consisting of x_d, y_d, and theta_d. We call it Ramsete because
* that's the acronym for the title of the book it came from in Italian ("Robotica Articolata e
* Mobile per i SErvizi e le TEcnologie").
*
* <p>See <a href="https://file.tavsys.net/control/controls-engineering-in-frc.pdf">Controls
* Engineering in the FIRST Robotics Competition</a> section on Ramsete unicycle controller for a
* derivation and analysis.
*/
public class RamseteController {
private final double m_b;
private final double m_zeta;
private Pose2d m_poseError = Pose2d.kZero;
private Pose2d m_poseTolerance = Pose2d.kZero;
private boolean m_enabled = true;
/**
* Construct a Ramsete unicycle controller.
*
* @param b Tuning parameter (b &gt; 0 rad²/m²) for which larger values make convergence more
* aggressive like a proportional term.
* @param zeta Tuning parameter (0 rad⁻¹ &lt; zeta &lt; 1 rad⁻¹) for which larger values provide
* more damping in response.
* @deprecated Use LTVUnicycleController instead.
*/
@Deprecated(since = "2025", forRemoval = true)
public RamseteController(double b, double zeta) {
m_b = b;
m_zeta = zeta;
}
/**
* Construct a Ramsete unicycle controller. The default arguments for b and zeta of 2.0 rad²/m²
* and 0.7 rad⁻¹ have been well-tested to produce desirable results.
*
* @deprecated Use LTVUnicycleController instead.
*/
@Deprecated(since = "2025", forRemoval = true)
public RamseteController() {
this(2.0, 0.7);
}
/**
* Returns true if the pose error is within tolerance of the reference.
*
* @return True if the pose error is within tolerance of the reference.
*/
public boolean atReference() {
final var eTranslate = m_poseError.getTranslation();
final var eRotate = m_poseError.getRotation();
final var tolTranslate = m_poseTolerance.getTranslation();
final var tolRotate = m_poseTolerance.getRotation();
return Math.abs(eTranslate.getX()) < tolTranslate.getX()
&& Math.abs(eTranslate.getY()) < tolTranslate.getY()
&& Math.abs(eRotate.getRadians()) < tolRotate.getRadians();
}
/**
* Sets the pose error which is considered tolerable for use with atReference().
*
* @param poseTolerance Pose error which is tolerable.
*/
public void setTolerance(Pose2d poseTolerance) {
m_poseTolerance = poseTolerance;
}
/**
* Returns the next output of the Ramsete controller.
*
* <p>The reference pose, linear velocity, and angular velocity should come from a drivetrain
* trajectory.
*
* @param currentPose The current pose.
* @param poseRef The desired pose.
* @param linearVelocityRefMeters The desired linear velocity in meters per second.
* @param angularVelocityRefRadiansPerSecond The desired angular velocity in radians per second.
* @return The next controller output.
*/
public ChassisSpeeds calculate(
Pose2d currentPose,
Pose2d poseRef,
double linearVelocityRefMeters,
double angularVelocityRefRadiansPerSecond) {
if (!m_enabled) {
return new ChassisSpeeds(linearVelocityRefMeters, 0.0, angularVelocityRefRadiansPerSecond);
}
m_poseError = poseRef.relativeTo(currentPose);
// Aliases for equation readability
final double eX = m_poseError.getX();
final double eY = m_poseError.getY();
final double eTheta = m_poseError.getRotation().getRadians();
final double vRef = linearVelocityRefMeters;
final double omegaRef = angularVelocityRefRadiansPerSecond;
// k = 2ζ√(ω_ref² + b v_ref²)
double k = 2.0 * m_zeta * Math.sqrt(Math.pow(omegaRef, 2) + m_b * Math.pow(vRef, 2));
// v_cmd = v_ref cos(e_θ) + k e_x
// ω_cmd = ω_ref + k e_θ + b v_ref sinc(e_θ) e_y
return new ChassisSpeeds(
vRef * m_poseError.getRotation().getCos() + k * eX,
0.0,
omegaRef + k * eTheta + m_b * vRef * sinc(eTheta) * eY);
}
/**
* Returns the next output of the Ramsete controller.
*
* <p>The reference pose, linear velocity, and angular velocity should come from a drivetrain
* trajectory.
*
* @param currentPose The current pose.
* @param desiredState The desired pose, linear velocity, and angular velocity from a trajectory.
* @return The next controller output.
*/
public ChassisSpeeds calculate(Pose2d currentPose, Trajectory.State desiredState) {
return calculate(
currentPose,
desiredState.poseMeters,
desiredState.velocityMetersPerSecond,
desiredState.velocityMetersPerSecond * desiredState.curvatureRadPerMeter);
}
/**
* Enables and disables the controller for troubleshooting purposes.
*
* @param enabled If the controller is enabled or not.
*/
public void setEnabled(boolean enabled) {
m_enabled = enabled;
}
/**
* Returns sin(x) / x.
*
* @param x Value of which to take sinc(x).
*/
private static double sinc(double x) {
if (Math.abs(x) < 1e-9) {
return 1.0 - 1.0 / 6.0 * x * x;
} else {
return Math.sin(x) / x;
}
}
}

5
wpimath/src/main/native/include/frc/controller/LTVDifferentialDriveController.h
View File

@@ -29,12 +29,11 @@ namespace frc {
* 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
* and voltage outputs. This is different from a unicycle 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.
* shot.
*
* See section 8.7 in Controls Engineering in FRC for a derivation of the
* control law we used shown in theorem 8.7.4.

3
wpimath/src/main/native/include/frc/controller/LTVUnicycleController.h
View File

@@ -24,9 +24,6 @@ namespace frc {
* 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.
*/

193
wpimath/src/main/native/include/frc/controller/RamseteController.h
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@@ -1,193 +0,0 @@
// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
#pragma once
#include <wpi/SymbolExports.h>
#include <wpi/deprecated.h>
#include "frc/geometry/Pose2d.h"
#include "frc/kinematics/ChassisSpeeds.h"
#include "frc/trajectory/Trajectory.h"
#include "units/angle.h"
#include "units/angular_velocity.h"
#include "units/length.h"
#include "units/math.h"
#include "units/velocity.h"
namespace frc {
/**
* Ramsete is a nonlinear time-varying feedback controller for unicycle models
* that drives the model to a desired pose along a two-dimensional trajectory.
* Why would we need a nonlinear control law in addition to the linear ones we
* have used so far like PID? If we use the original approach with PID
* controllers for left and right position and velocity states, the controllers
* only deal with the local pose. If the robot deviates from the path, there is
* no way for the controllers to correct and the robot may not reach the desired
* global pose. This is due to multiple endpoints existing for the robot which
* have the same encoder path arc lengths.
*
* Instead of using wheel path arc lengths (which are in the robot's local
* coordinate frame), nonlinear controllers like pure pursuit and Ramsete use
* global pose. The controller uses this extra information to guide a linear
* reference tracker like the PID controllers back in by adjusting the
* references of the PID controllers.
*
* The paper "Control of Wheeled Mobile Robots: An Experimental Overview"
* describes a nonlinear controller for a wheeled vehicle with unicycle-like
* kinematics; a global pose consisting of x, y, and theta; and a desired pose
* consisting of x_d, y_d, and theta_d. We call it Ramsete because that's the
* acronym for the title of the book it came from in Italian ("Robotica
* Articolata e Mobile per i SErvizi e le TEcnologie").
*
* See <https://file.tavsys.net/control/controls-engineering-in-frc.pdf> section
* on Ramsete unicycle controller for a derivation and analysis.
*/
class WPILIB_DLLEXPORT RamseteController {
public:
using b_unit =
units::compound_unit<units::squared<units::radians>,
units::inverse<units::squared<units::meters>>>;
using zeta_unit = units::inverse<units::radians>;
/**
* Construct a Ramsete unicycle controller.
*
* @param b Tuning parameter (b > 0 rad²/m²) for which larger values make
* convergence more aggressive like a proportional term.
* @param zeta Tuning parameter (0 rad⁻¹ < zeta < 1 rad⁻¹) for which larger
* values provide more damping in response.
* @deprecated Use LTVUnicycleController instead.
*/
[[deprecated("Use LTVUnicycleController instead.")]]
constexpr RamseteController(units::unit_t<b_unit> b,
units::unit_t<zeta_unit> zeta)
: m_b{b}, m_zeta{zeta} {}
WPI_IGNORE_DEPRECATED
/**
* Construct a Ramsete unicycle controller. The default arguments for
* b and zeta of 2.0 rad²/m² and 0.7 rad⁻¹ have been well-tested to produce
* desirable results.
*
* @deprecated Use LTVUnicycleController instead.
*/
[[deprecated("Use LTVUnicycleController instead.")]]
constexpr RamseteController()
: RamseteController{units::unit_t<b_unit>{2.0},
units::unit_t<zeta_unit>{0.7}} {}
WPI_UNIGNORE_DEPRECATED
/**
* Returns true if the pose error is within tolerance of the reference.
*/
constexpr bool AtReference() const {
const auto& eTranslate = m_poseError.Translation();
const auto& eRotate = m_poseError.Rotation();
const auto& tolTranslate = m_poseTolerance.Translation();
const auto& tolRotate = m_poseTolerance.Rotation();
return units::math::abs(eTranslate.X()) < tolTranslate.X() &&
units::math::abs(eTranslate.Y()) < tolTranslate.Y() &&
units::math::abs(eRotate.Radians()) < tolRotate.Radians();
}
/**
* Sets the pose error which is considered tolerable for use with
* AtReference().
*
* @param poseTolerance Pose error which is tolerable.
*/
constexpr void SetTolerance(const Pose2d& poseTolerance) {
m_poseTolerance = poseTolerance;
}
/**
* Returns the next output of the Ramsete controller.
*
* The reference pose, linear velocity, and angular velocity should come from
* a drivetrain trajectory.
*
* @param currentPose The current pose.
* @param poseRef The desired pose.
* @param linearVelocityRef The desired linear velocity.
* @param angularVelocityRef The desired angular velocity.
*/
constexpr ChassisSpeeds Calculate(
const Pose2d& currentPose, const Pose2d& poseRef,
units::meters_per_second_t linearVelocityRef,
units::radians_per_second_t angularVelocityRef) {
if (!m_enabled) {
return ChassisSpeeds{linearVelocityRef, 0_mps, angularVelocityRef};
}
m_poseError = poseRef.RelativeTo(currentPose);
// Aliases for equation readability
const auto& eX = m_poseError.X();
const auto& eY = m_poseError.Y();
const auto& eTheta = m_poseError.Rotation().Radians();
const auto& vRef = linearVelocityRef;
const auto& omegaRef = angularVelocityRef;
// k = 2ζ√(ω_ref² + b v_ref²)
auto k = 2.0 * m_zeta *
units::math::sqrt(units::math::pow<2>(omegaRef) +
m_b * units::math::pow<2>(vRef));
// v_cmd = v_ref cos(e_θ) + k e_x
// ω_cmd = ω_ref + k e_θ + b v_ref sinc(e_θ) e_y
return ChassisSpeeds{
vRef * m_poseError.Rotation().Cos() + k * eX, 0_mps,
omegaRef + k * eTheta + m_b * vRef * Sinc(eTheta) * eY};
}
/**
* Returns the next output of the Ramsete controller.
*
* The reference pose, linear velocity, and angular velocity should come from
* a drivetrain trajectory.
*
* @param currentPose The current pose.
* @param desiredState The desired pose, linear velocity, and angular velocity
* from a trajectory.
*/
constexpr ChassisSpeeds Calculate(const Pose2d& currentPose,
const Trajectory::State& desiredState) {
return Calculate(currentPose, desiredState.pose, desiredState.velocity,
desiredState.velocity * desiredState.curvature);
}
/**
* Enables and disables the controller for troubleshooting purposes.
*
* @param enabled If the controller is enabled or not.
*/
constexpr void SetEnabled(bool enabled) { m_enabled = enabled; }
private:
units::unit_t<b_unit> m_b;
units::unit_t<zeta_unit> m_zeta;
Pose2d m_poseError;
Pose2d m_poseTolerance;
bool m_enabled = true;
/**
* Returns sin(x) / x.
*
* @param x Value of which to take sinc(x).
*/
static constexpr decltype(1 / 1_rad) Sinc(units::radian_t x) {
if (units::math::abs(x) < 1e-9_rad) {
return decltype(1 / 1_rad){1.0 - 1.0 / 6.0 * x.value() * x.value()};
} else {
return units::math::sin(x) / x;
}
}
};
} // namespace frc

62
wpimath/src/test/java/edu/wpi/first/math/controller/RamseteControllerTest.java
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@@ -1,62 +0,0 @@
// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
package edu.wpi.first.math.controller;
import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;
import edu.wpi.first.math.MathUtil;
import edu.wpi.first.math.geometry.Pose2d;
import edu.wpi.first.math.geometry.Rotation2d;
import edu.wpi.first.math.geometry.Twist2d;
import edu.wpi.first.math.trajectory.TrajectoryConfig;
import edu.wpi.first.math.trajectory.TrajectoryGenerator;
import java.util.ArrayList;
import org.junit.jupiter.api.Test;
class RamseteControllerTest {
private static final double kTolerance = 1 / 12.0;
private static final double kAngularTolerance = Math.toRadians(2);
@SuppressWarnings("removal")
@Test
void testReachesReference() {
final var controller = new RamseteController(2.0, 0.7);
var robotPose = new Pose2d(2.7, 23.0, Rotation2d.kZero);
final var waypoints = new ArrayList<Pose2d>();
waypoints.add(new Pose2d(2.75, 22.521, Rotation2d.kZero));
waypoints.add(new Pose2d(24.73, 19.68, new Rotation2d(5.846)));
var config = new TrajectoryConfig(8.8, 0.1);
final var trajectory = TrajectoryGenerator.generateTrajectory(waypoints, config);
final double kDt = 0.02;
final var totalTime = trajectory.getTotalTimeSeconds();
for (int i = 0; i < (totalTime / kDt); ++i) {
var state = trajectory.sample(kDt * i);
var output = controller.calculate(robotPose, state);
robotPose =
robotPose.exp(
new Twist2d(output.vxMetersPerSecond * kDt, 0, output.omegaRadiansPerSecond * kDt));
}
final var states = trajectory.getStates();
final var endPose = states.get(states.size() - 1).poseMeters;
// Java lambdas require local variables referenced from a lambda expression
// must be final or effectively final.
final var finalRobotPose = robotPose;
assertAll(
() -> assertEquals(endPose.getX(), finalRobotPose.getX(), kTolerance),
() -> assertEquals(endPose.getY(), finalRobotPose.getY(), kTolerance),
() ->
assertEquals(
0.0,
MathUtil.angleModulus(
endPose.getRotation().getRadians() - finalRobotPose.getRotation().getRadians()),
kAngularTolerance));
}
}

50
wpimath/src/test/native/cpp/controller/RamseteControllerTest.cpp
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@@ -1,50 +0,0 @@
// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
#include <gtest/gtest.h>
#include <wpi/deprecated.h>
#include "frc/MathUtil.h"
#include "frc/controller/RamseteController.h"
#include "frc/trajectory/TrajectoryGenerator.h"
#include "units/math.h"
#define EXPECT_NEAR_UNITS(val1, val2, eps) \
EXPECT_LE(units::math::abs(val1 - val2), eps)
static constexpr units::meter_t kTolerance{1 / 12.0};
static constexpr units::radian_t kAngularTolerance{2.0 * std::numbers::pi /
180.0};
WPI_IGNORE_DEPRECATED
TEST(RamseteControllerTest, ReachesReference) {
frc::RamseteController controller{2.0 * 1_rad * 1_rad / (1_m * 1_m),
0.7 / 1_rad};
frc::Pose2d robotPose{2.7_m, 23_m, 0_deg};
auto waypoints = std::vector{frc::Pose2d{2.75_m, 22.521_m, 0_rad},
frc::Pose2d{24.73_m, 19.68_m, 5.846_rad}};
auto trajectory = frc::TrajectoryGenerator::GenerateTrajectory(
waypoints, {8.8_mps, 0.1_mps_sq});
constexpr units::second_t kDt = 20_ms;
auto totalTime = trajectory.TotalTime();
for (size_t i = 0; i < (totalTime / kDt).value(); ++i) {
auto state = trajectory.Sample(kDt * i);
auto [vx, vy, omega] = controller.Calculate(robotPose, state);
static_cast<void>(vy);
robotPose = robotPose.Exp(frc::Twist2d{vx * kDt, 0_m, omega * kDt});
}
auto& endPose = trajectory.States().back().pose;
EXPECT_NEAR_UNITS(endPose.X(), robotPose.X(), kTolerance);
EXPECT_NEAR_UNITS(endPose.Y(), robotPose.Y(), kTolerance);
EXPECT_NEAR_UNITS(frc::AngleModulus(endPose.Rotation().Radians() -
robotPose.Rotation().Radians()),
0_rad, kAngularTolerance);
}
WPI_UNIGNORE_DEPRECATED