[wpimath] Replace Speeds with Velocities (#8479)

I left "free speed" alone since that's the technical term for it. In
general, velocity is a vector quantity, and speed is a magnitude (i.e.,
a strictly positive value).

This PR also replaces the speed verbiage in MotorController with duty
cycle.

Fixes #8423.

wpilibcExamples/src/main/cpp/examples/XRPReference/include/commands/DriveDistance.hpp

@@ -14,14 +14,15 @@ class DriveDistance
  public:
   /**
    * Creates a new DriveDistance. This command will drive your your robot for a
-   * desired distance at a desired speed.
+   * desired distance at a desired velocity.
    *
-   * @param speed The speed at which the robot will drive
+   * @param velocity The velocity at which the robot will drive
    * @param distance The distance the robot will drive
    * @param drive The drivetrain subsystem on which this command will run
    */
-  DriveDistance(double speed, wpi::units::meter_t distance, Drivetrain* drive)
-      : m_speed(speed), m_distance(distance), m_drive(drive) {
+  DriveDistance(double velocity, wpi::units::meter_t distance,
+                Drivetrain* drive)
+      : m_velocity(velocity), m_distance(distance), m_drive(drive) {
     AddRequirements(m_drive);
   }
 
@@ -31,7 +32,7 @@ class DriveDistance
   bool IsFinished() override;
 
  private:
-  double m_speed;
+  double m_velocity;
   wpi::units::meter_t m_distance;
   Drivetrain* m_drive;
 };

wpilibcExamples/src/main/cpp/examples/XRPReference/include/commands/DriveTime.hpp

@@ -14,14 +14,15 @@ class DriveTime : public wpi::cmd::CommandHelper<wpi::cmd::Command, DriveTime> {
  public:
   /**
    * Creates a new DriveTime. This command will drive your robot for a desired
-   * speed and time.
+   * velocity and time.
    *
-   * @param speed The speed which the robot will drive. Negative is in reverse.
+   * @param velocity The velocity which the robot will drive. Negative is in
+   *     reverse.
    * @param time How much time to drive
    * @param drive The drivetrain subsystem on which this command will run
    */
-  DriveTime(double speed, wpi::units::second_t time, Drivetrain* drive)
-      : m_speed(speed), m_duration(time), m_drive(drive) {
+  DriveTime(double velocity, wpi::units::second_t time, Drivetrain* drive)
+      : m_velocity(velocity), m_duration(time), m_drive(drive) {
     AddRequirements(m_drive);
   }
 
@@ -31,7 +32,7 @@ class DriveTime : public wpi::cmd::CommandHelper<wpi::cmd::Command, DriveTime> {
   bool IsFinished() override;
 
  private:
-  double m_speed;
+  double m_velocity;
   wpi::units::second_t m_duration;
   Drivetrain* m_drive;
   wpi::Timer m_timer;

wpilibcExamples/src/main/cpp/examples/XRPReference/include/commands/TeleopArcadeDrive.hpp

@@ -15,19 +15,19 @@ class TeleopArcadeDrive
  public:
   /**
    * Creates a new ArcadeDrive. This command will drive your robot according to
-   * the speed suppliers. This command does not terminate.
+   * the velocity suppliers. This command does not terminate.
    *
    * @param drivetrain The drivetrain subsystem on which this command will run
-   * @param xaxisSpeedSupplier Supplier of forward/backward speed
-   * @param zaxisRotateSupplier Supplier of rotational speed
+   * @param xaxisVelocitySupplier Supplier of forward/backward velocity
+   * @param zaxisRotateSupplier Supplier of rotational velocity
    */
   TeleopArcadeDrive(Drivetrain* subsystem,
-                    std::function<double()> xaxisSpeedSupplier,
+                    std::function<double()> xaxisVelocitySupplier,
                     std::function<double()> zaxisRotateSupplier);
   void Execute() override;
 
  private:
   Drivetrain* m_drive;
-  std::function<double()> m_xaxisSpeedSupplier;
+  std::function<double()> m_xaxisVelocitySupplier;
   std::function<double()> m_zaxisRotateSupplier;
 };

wpilibcExamples/src/main/cpp/examples/XRPReference/include/commands/TurnDegrees.hpp

@@ -15,14 +15,15 @@ class TurnDegrees
  public:
   /**
    * Creates a new TurnDegrees. This command will turn your robot for a desired
-   * rotation (in degrees) and rotational speed.
+   * rotation (in degrees) and rotational velocity.
    *
-   * @param speed The speed which the robot will drive. Negative is in reverse.
+   * @param velocity The velocity which the robot will drive. Negative is in
+   *     reverse.
    * @param angle Degrees to turn. Leverages encoders to compare distance.
    * @param drive The drive subsystem on which this command will run
    */
-  TurnDegrees(double speed, wpi::units::degree_t angle, Drivetrain* drive)
-      : m_speed(speed), m_angle(angle), m_drive(drive) {
+  TurnDegrees(double velocity, wpi::units::degree_t angle, Drivetrain* drive)
+      : m_velocity(velocity), m_angle(angle), m_drive(drive) {
     AddRequirements(m_drive);
   }
 
@@ -32,7 +33,7 @@ class TurnDegrees
   bool IsFinished() override;
 
  private:
-  double m_speed;
+  double m_velocity;
   wpi::units::degree_t m_angle;
   Drivetrain* m_drive;
 

wpilibcExamples/src/main/cpp/examples/XRPReference/include/commands/TurnTime.hpp

@@ -15,12 +15,13 @@ class TurnTime : public wpi::cmd::CommandHelper<wpi::cmd::Command, TurnTime> {
   /**
    * Creates a new TurnTime.
    *
-   * @param speed The speed which the robot will turn. Negative is in reverse.
+   * @param velocity The velocity which the robot will turn. Negative is in
+   *     reverse.
    * @param time How much time to turn
    * @param drive The drive subsystem on which this command will run
    */
-  TurnTime(double speed, wpi::units::second_t time, Drivetrain* drive)
-      : m_speed(speed), m_duration(time), m_drive(drive) {
+  TurnTime(double velocity, wpi::units::second_t time, Drivetrain* drive)
+      : m_velocity(velocity), m_duration(time), m_drive(drive) {
     AddRequirements(m_drive);
   }
 
@@ -30,7 +31,7 @@ class TurnTime : public wpi::cmd::CommandHelper<wpi::cmd::Command, TurnTime> {
   bool IsFinished() override;
 
  private:
-  double m_speed;
+  double m_velocity;
   wpi::units::second_t m_duration;
   Drivetrain* m_drive;
   wpi::Timer m_timer;

wpilibcExamples/src/main/cpp/examples/XRPReference/include/subsystems/Drivetrain.hpp

@@ -32,10 +32,10 @@ class Drivetrain : public wpi::cmd::SubsystemBase {
   /**
    * Drives the robot using arcade controls.
    *
-   * @param xaxisSpeed the commanded forward movement
+   * @param xaxisVelocity the commanded forward movement
    * @param zaxisRotate the commanded rotation
    */
-  void ArcadeDrive(double xaxisSpeed, double zaxisRotate);
+  void ArcadeDrive(double xaxisVelocity, double zaxisRotate);
 
   /**
    * Resets the drive encoders to currently read a position of 0.
@@ -111,8 +111,8 @@ class Drivetrain : public wpi::cmd::SubsystemBase {
   wpi::Encoder m_rightEncoder{6, 7};
 
   wpi::DifferentialDrive m_drive{
-      [&](double output) { m_leftMotor.Set(output); },
-      [&](double output) { m_rightMotor.Set(output); }};
+      [&](double output) { m_leftMotor.SetDutyCycle(output); },
+      [&](double output) { m_rightMotor.SetDutyCycle(output); }};
 
   wpi::xrp::XRPGyro m_gyro;
 };