Add TrapezoidProfile external PID examples (#2131)

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/Constants.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <units/units.h>
+#include <wpi/math>
+
+/**
+ * The Constants header provides a convenient place for teams to hold robot-wide
+ * numerical or bool constants.  This should not be used for any other purpose.
+ *
+ * It is generally a good idea to place constants into subsystem- or
+ * command-specific namespaces within this header, which can then be used where
+ * they are needed.
+ */
+
+namespace DriveConstants {
+constexpr int kLeftMotor1Port = 0;
+constexpr int kLeftMotor2Port = 1;
+constexpr int kRightMotor1Port = 2;
+constexpr int kRightMotor2Port = 3;
+
+// These are example values only - DO NOT USE THESE FOR YOUR OWN ROBOT!
+// These characterization values MUST be determined either experimentally or
+// theoretically for *your* robot's drive. The RobotPy Characterization
+// Toolsuite provides a convenient tool for obtaining these values for your
+// robot.
+constexpr auto ks = 1_V;
+constexpr auto kv = 0.8_V * 1_s / 1_m;
+constexpr auto ka = 0.15_V * 1_s * 1_s / 1_m;
+
+constexpr double kp = 1;
+
+constexpr auto kMaxSpeed = 3_mps;
+constexpr auto kMaxAcceleration = 3_mps_sq;
+
+}  // namespace DriveConstants
+
+namespace OIConstants {
+constexpr int kDriverControllerPort = 1;
+}  // namespace OIConstants

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/ExampleSmartMotorController.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/SpeedController.h>
+
+/**
+ * A simplified stub class that simulates the API of a common "smart" motor
+ * controller.
+ *
+ * <p>Has no actual functionality.
+ */
+class ExampleSmartMotorController : public frc::SpeedController {
+ public:
+  enum PIDMode { kPosition, kVelocity, kMovementWitchcraft };
+
+  /**
+   * Creates a new ExampleSmartMotorController.
+   *
+   * @param port The port for the controller.
+   */
+  explicit ExampleSmartMotorController(int port) {}
+
+  /**
+   * Example method for setting the PID gains of the smart controller.
+   *
+   * @param kp The proportional gain.
+   * @param ki The integral gain.
+   * @param kd The derivative gain.
+   */
+  void SetPID(double kp, double ki, double kd) {}
+
+  /**
+   * Example method for setting the setpoint of the smart controller in PID
+   * mode.
+   *
+   * @param mode The mode of the PID controller.
+   * @param setpoint The controller setpoint.
+   * @param arbFeedforward An arbitrary feedforward output (from -1 to 1).
+   */
+  void SetSetpoint(PIDMode mode, double setpoint, double arbFeedforward) {}
+
+  /**
+   * Places this motor controller in follower mode.
+   *
+   * @param master The master to follow.
+   */
+  void Follow(ExampleSmartMotorController master) {}
+
+  /**
+   * Returns the encoder distance.
+   *
+   * @return The current encoder distance.
+   */
+  double GetEncoderDistance() { return 0; }
+
+  /**
+   * Returns the encoder rate.
+   *
+   * @return The current encoder rate.
+   */
+  double GetEncoderRate() { return 0; }
+
+  /**
+   * Resets the encoder to zero distance.
+   */
+  void ResetEncoder() {}
+
+  void Set(double speed) override {}
+
+  double Get() const override { return 0; }
+
+  void SetInverted(bool isInverted) override {}
+
+  bool GetInverted() const override { return false; }
+
+  void Disable() override {}
+
+  void StopMotor() override {}
+
+  void PIDWrite(double output) override {}
+};

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/Robot.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017-2019 FIRST. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/TimedRobot.h>
+#include <frc2/command/Command.h>
+
+#include "RobotContainer.h"
+
+class Robot : public frc::TimedRobot {
+ public:
+  void RobotInit() override;
+  void RobotPeriodic() override;
+  void DisabledInit() override;
+  void DisabledPeriodic() override;
+  void AutonomousInit() override;
+  void AutonomousPeriodic() override;
+  void TeleopInit() override;
+  void TeleopPeriodic() override;
+  void TestPeriodic() override;
+
+ private:
+  // Have it null by default so that if testing teleop it
+  // doesn't have undefined behavior and potentially crash.
+  frc2::Command* m_autonomousCommand = nullptr;
+
+  RobotContainer m_container;
+};

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/RobotContainer.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/XboxController.h>
+#include <frc/smartdashboard/SendableChooser.h>
+#include <frc2/command/Command.h>
+#include <frc2/command/InstantCommand.h>
+#include <frc2/command/ParallelRaceGroup.h>
+#include <frc2/command/RunCommand.h>
+#include <frc2/command/SequentialCommandGroup.h>
+#include <frc2/command/StartEndCommand.h>
+
+#include "Constants.h"
+#include "subsystems/DriveSubsystem.h"
+
+/**
+ * This class is where the bulk of the robot should be declared.  Since
+ * Command-based is a "declarative" paradigm, very little robot logic should
+ * actually be handled in the {@link Robot} periodic methods (other than the
+ * scheduler calls).  Instead, the structure of the robot (including subsystems,
+ * commands, and button mappings) should be declared here.
+ */
+class RobotContainer {
+ public:
+  RobotContainer();
+
+  frc2::Command* GetAutonomousCommand();
+
+ private:
+  // The driver's controller
+  frc::XboxController m_driverController{OIConstants::kDriverControllerPort};
+
+  // The robot's subsystems and commands are defined here...
+
+  // The robot's subsystems
+  DriveSubsystem m_drive;
+
+  frc2::InstantCommand m_driveHalfSpeed{[this] { m_drive.SetMaxOutput(0.5); },
+                                        {}};
+  frc2::InstantCommand m_driveFullSpeed{[this] { m_drive.SetMaxOutput(1); },
+                                        {}};
+
+  void ConfigureButtonBindings();
+};

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/commands/DriveDistanceProfiled.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc2/command/CommandHelper.h>
+#include <frc2/command/TrapezoidProfileCommand.h>
+
+#include "subsystems/DriveSubsystem.h"
+
+class DriveDistanceProfiled
+    : public frc2::CommandHelper<frc2::TrapezoidProfileCommand<units::meters>,
+                                 DriveDistanceProfiled> {
+ public:
+  DriveDistanceProfiled(units::meter_t distance, DriveSubsystem* drive);
+};

wpilibcExamples/src/main/cpp/examples/DriveDistanceOffboard/include/subsystems/DriveSubsystem.h

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+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <frc/Encoder.h>
+#include <frc/controller/SimpleMotorFeedforward.h>
+#include <frc/drive/DifferentialDrive.h>
+#include <frc/trajectory/TrapezoidProfile.h>
+#include <frc2/command/SubsystemBase.h>
+#include <units/units.h>
+
+#include "Constants.h"
+#include "ExampleSmartMotorController.h"
+
+class DriveSubsystem : public frc2::SubsystemBase {
+ public:
+  DriveSubsystem();
+
+  /**
+   * Will be called periodically whenever the CommandScheduler runs.
+   */
+  void Periodic() override;
+
+  // Subsystem methods go here.
+
+  /**
+   * Attempts to follow the given drive states using offboard PID.
+   *
+   * @param left The left wheel state.
+   * @param right The right wheel state.
+   */
+  void SetDriveStates(frc::TrapezoidProfile<units::meters>::State left,
+                      frc::TrapezoidProfile<units::meters>::State right);
+
+  /**
+   * Drives the robot using arcade controls.
+   *
+   * @param fwd the commanded forward movement
+   * @param rot the commanded rotation
+   */
+  void ArcadeDrive(double fwd, double rot);
+
+  /**
+   * Resets the drive encoders to currently read a position of 0.
+   */
+  void ResetEncoders();
+
+  /**
+   * Gets the distance of the left encoder.
+   *
+   * @return the average of the TWO encoder readings
+   */
+  units::meter_t GetLeftEncoderDistance();
+
+  /**
+   * Gets the distance of the right encoder.
+   *
+   * @return the average of the TWO encoder readings
+   */
+  units::meter_t GetRightEncoderDistance();
+
+  /**
+   * Sets the max output of the drive.  Useful for scaling the drive to drive
+   * more slowly.
+   *
+   * @param maxOutput the maximum output to which the drive will be constrained
+   */
+  void SetMaxOutput(double maxOutput);
+
+ private:
+  // Components (e.g. motor controllers and sensors) should generally be
+  // declared private and exposed only through public methods.
+
+  // The motor controllers
+  ExampleSmartMotorController m_leftMaster;
+  ExampleSmartMotorController m_leftSlave;
+  ExampleSmartMotorController m_rightMaster;
+  ExampleSmartMotorController m_rightSlave;
+
+  // A feedforward component for the drive
+  frc::SimpleMotorFeedforward<units::meters> m_feedforward;
+
+  // The robot's drive
+  frc::DifferentialDrive m_drive{m_leftMaster, m_rightMaster};
+};