Add ProfiledPIDSubsystem example (#2076)

wpilibcExamples/src/main/cpp/examples/ArmBot/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;
+
+constexpr int kLeftEncoderPorts[]{0, 1};
+constexpr int kRightEncoderPorts[]{2, 3};
+constexpr bool kLeftEncoderReversed = false;
+constexpr bool kRightEncoderReversed = true;
+
+constexpr int kEncoderCPR = 1024;
+constexpr double kWheelDiameterInches = 6;
+constexpr double kEncoderDistancePerPulse =
+    // Assumes the encoders are directly mounted on the wheel shafts
+    (kWheelDiameterInches * wpi::math::pi) / static_cast<double>(kEncoderCPR);
+}  // namespace DriveConstants
+
+namespace ArmConstants {
+constexpr int kMotorPort = 4;
+
+constexpr double kP = 1;
+
+// These are fake gains; in actuality these must be determined individually for
+// each robot
+constexpr auto kS = 1_V;
+constexpr auto kCos = 1_V;
+constexpr auto kV = 0.5_V * 1_s / 1_rad;
+constexpr auto kA = 0.1_V * 1_s * 1_s / 1_rad;
+
+constexpr auto kMaxVelocity = 3_rad_per_s;
+constexpr auto kMaxAcceleration = 10_rad / (1_s * 1_s);
+
+constexpr int kEncoderPorts[]{4, 5};
+constexpr int kEncoderPPR = 256;
+constexpr auto kEncoderDistancePerPulse = 2.0_rad * wpi::math::pi / kEncoderPPR;
+
+// The offset of the arm from the horizontal in its neutral position,
+// measured from the horizontal
+constexpr auto kArmOffset = 0.5_rad;
+}  // namespace ArmConstants
+
+namespace AutoConstants {
+constexpr auto kAutoTimeoutSeconds = 12_s;
+constexpr auto kAutoShootTimeSeconds = 7_s;
+}  // namespace AutoConstants
+
+namespace OIConstants {
+constexpr int kDriverControllerPort = 1;
+}  // namespace OIConstants

wpilibcExamples/src/main/cpp/examples/ArmBot/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/ArmBot/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/ConditionalCommand.h>
+#include <frc2/command/InstantCommand.h>
+#include <frc2/command/ParallelRaceGroup.h>
+#include <frc2/command/RunCommand.h>
+#include <frc2/command/SequentialCommandGroup.h>
+#include <frc2/command/WaitCommand.h>
+#include <frc2/command/WaitUntilCommand.h>
+
+#include "Constants.h"
+#include "subsystems/ArmSubsystem.h"
+#include "subsystems/DriveSubsystem.h"
+
+namespace ac = AutoConstants;
+
+/**
+ * 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;
+  ArmSubsystem m_arm;
+
+  // The chooser for the autonomous routines
+
+  void ConfigureButtonBindings();
+};

wpilibcExamples/src/main/cpp/examples/ArmBot/include/subsystems/ArmSubsystem.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/PWMVictorSPX.h>
+#include <frc/controller/ArmFeedforward.h>
+#include <frc2/command/ProfiledPIDSubsystem.h>
+#include <units/units.h>
+
+/**
+ * A robot arm subsystem that moves with a motion profile.
+ */
+class ArmSubsystem : public frc2::ProfiledPIDSubsystem<units::radians> {
+  using State = frc::TrapezoidProfile<units::radians>::State;
+
+ public:
+  ArmSubsystem();
+
+  void UseOutput(double output, State setpoint) override;
+
+  void SetGoal(units::radian_t goal);
+
+  State GetGoal() override;
+
+  units::radian_t GetMeasurement() override;
+
+ private:
+  frc::PWMVictorSPX m_motor;
+  frc::Encoder m_encoder;
+  frc::ArmFeedforward m_feedforward;
+
+  State m_goal;
+};

wpilibcExamples/src/main/cpp/examples/ArmBot/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/PWMVictorSPX.h>
+#include <frc/SpeedControllerGroup.h>
+#include <frc/drive/DifferentialDrive.h>
+#include <frc2/command/SubsystemBase.h>
+
+#include "Constants.h"
+
+class DriveSubsystem : public frc2::SubsystemBase {
+ public:
+  DriveSubsystem();
+
+  /**
+   * Will be called periodically whenever the CommandScheduler runs.
+   */
+  void Periodic() override;
+
+  // Subsystem methods go here.
+
+  /**
+   * 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 average distance of the TWO encoders.
+   *
+   * @return the average of the TWO encoder readings
+   */
+  double GetAverageEncoderDistance();
+
+  /**
+   * Gets the left drive encoder.
+   *
+   * @return the left drive encoder
+   */
+  frc::Encoder& GetLeftEncoder();
+
+  /**
+   * Gets the right drive encoder.
+   *
+   * @return the right drive encoder
+   */
+  frc::Encoder& GetRightEncoder();
+
+  /**
+   * 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
+  frc::PWMVictorSPX m_left1;
+  frc::PWMVictorSPX m_left2;
+  frc::PWMVictorSPX m_right1;
+  frc::PWMVictorSPX m_right2;
+
+  // The motors on the left side of the drive
+  frc::SpeedControllerGroup m_leftMotors{m_left1, m_left2};
+
+  // The motors on the right side of the drive
+  frc::SpeedControllerGroup m_rightMotors{m_right1, m_right2};
+
+  // The robot's drive
+  frc::DifferentialDrive m_drive{m_leftMotors, m_rightMotors};
+
+  // The left-side drive encoder
+  frc::Encoder m_leftEncoder;
+
+  // The right-side drive encoder
+  frc::Encoder m_rightEncoder;
+};