[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.

wpilibc/src/main/native/cpp/hardware/expansionhub/ExpansionHubMotor.cpp

@@ -92,10 +92,10 @@ ExpansionHubMotor::~ExpansionHubMotor() noexcept {
   m_hub.UnreserveMotor(m_channel);
 }
 
-void ExpansionHubMotor::SetPercentagePower(double power) {
+void ExpansionHubMotor::SetDutyCycle(double dutyCycle) {
   SetEnabled(true);
   m_modePublisher.Set(kPercentageMode);
-  m_setpointPublisher.Set(power);
+  m_setpointPublisher.Set(dutyCycle);
 }
 
 void ExpansionHubMotor::SetVoltage(wpi::units::volt_t voltage) {

wpilibc/src/main/native/cpp/hardware/led/LEDPattern.cpp

@@ -69,7 +69,7 @@ LEDPattern LEDPattern::OffsetBy(int offset) {
   });
 }
 
-LEDPattern LEDPattern::ScrollAtRelativeSpeed(wpi::units::hertz_t velocity) {
+LEDPattern LEDPattern::ScrollAtRelativeVelocity(wpi::units::hertz_t velocity) {
   // velocity is in terms of LED lengths per second (1_hz = full cycle per
   // second, 0.5_hz = half cycle per second, 2_hz = two cycles per second)
   // Invert and multiply by 1,000,000 to get microseconds
@@ -88,7 +88,7 @@ LEDPattern LEDPattern::ScrollAtRelativeSpeed(wpi::units::hertz_t velocity) {
   });
 }
 
-LEDPattern LEDPattern::ScrollAtAbsoluteSpeed(
+LEDPattern LEDPattern::ScrollAtAbsoluteVelocity(
     wpi::units::meters_per_second_t velocity, wpi::units::meter_t ledSpacing) {
   // Velocity is in terms of meters per second
   // Multiply by 1,000,000 to use microseconds instead of seconds

wpilibc/src/main/native/cpp/hardware/motor/MotorController.cpp

@@ -8,7 +8,7 @@
 
 using namespace wpi;
 
-void MotorController::SetVoltage(wpi::units::volt_t output) {
+void MotorController::SetVoltage(wpi::units::volt_t voltage) {
   // NOLINTNEXTLINE(bugprone-integer-division)
-  Set(output / RobotController::GetBatteryVoltage());
+  SetDutyCycle(voltage / RobotController::GetBatteryVoltage());
 }

wpilibc/src/main/native/cpp/hardware/motor/PWMMotorController.cpp

@@ -14,33 +14,28 @@
 
 using namespace wpi;
 
-void PWMMotorController::Set(double speed) {
+void PWMMotorController::SetDutyCycle(double dutyCycle) {
   if (m_isInverted) {
-    speed = -speed;
+    dutyCycle = -dutyCycle;
   }
-  SetSpeed(speed);
+  SetDutyCycleInternal(dutyCycle);
 
   for (auto& follower : m_nonowningFollowers) {
-    follower->Set(speed);
+    follower->SetDutyCycle(dutyCycle);
   }
   for (auto& follower : m_owningFollowers) {
-    follower->Set(speed);
+    follower->SetDutyCycle(dutyCycle);
   }
 
   Feed();
 }
 
-void PWMMotorController::SetVoltage(wpi::units::volt_t output) {
-  // NOLINTNEXTLINE(bugprone-integer-division)
-  Set(output / RobotController::GetBatteryVoltage());
-}
-
-double PWMMotorController::Get() const {
-  return GetSpeed() * (m_isInverted ? -1.0 : 1.0);
+double PWMMotorController::GetDutyCycle() const {
+  return GetDutyCycleInternal() * (m_isInverted ? -1.0 : 1.0);
 }
 
 wpi::units::volt_t PWMMotorController::GetVoltage() const {
-  return Get() * RobotController::GetBatteryVoltage();
+  return GetDutyCycle() * RobotController::GetBatteryVoltage();
 }
 
 void PWMMotorController::SetInverted(bool isInverted) {
@@ -54,8 +49,8 @@ bool PWMMotorController::GetInverted() const {
 void PWMMotorController::Disable() {
   m_pwm.SetDisabled();
 
-  if (m_simSpeed) {
-    m_simSpeed.Set(0.0);
+  if (m_simDutyCycle) {
+    m_simDutyCycle.Set(0.0);
   }
 
   for (auto& follower : m_nonowningFollowers) {
@@ -94,7 +89,7 @@ PWMMotorController::PWMMotorController(std::string_view name, int channel)
 
   m_simDevice = wpi::hal::SimDevice{"PWMMotorController", channel};
   if (m_simDevice) {
-    m_simSpeed = m_simDevice.CreateDouble("Speed", true, 0.0);
+    m_simDutyCycle = m_simDevice.CreateDouble("DutyCycle", true, 0.0);
     m_pwm.SetSimDevice(m_simDevice);
   }
 }
@@ -105,8 +100,8 @@ void PWMMotorController::InitSendable(wpi::util::SendableBuilder& builder) {
   builder.SetSmartDashboardType("Motor Controller");
   builder.SetActuator(true);
   builder.AddDoubleProperty(
-      "Value", [=, this] { return Get(); },
-      [=, this](double value) { Set(value); });
+      "Value", [=, this] { return GetDutyCycle(); },
+      [=, this](double value) { SetDutyCycle(value); });
 }
 
 wpi::units::microsecond_t PWMMotorController::GetMinPositivePwm() const {
@@ -133,34 +128,34 @@ wpi::units::microsecond_t PWMMotorController::GetNegativeScaleFactor() const {
   return GetMaxNegativePwm() - m_minPwm;
 }
 
-void PWMMotorController::SetSpeed(double speed) {
-  if (std::isfinite(speed)) {
-    speed = std::clamp(speed, -1.0, 1.0);
+void PWMMotorController::SetDutyCycleInternal(double dutyCycle) {
+  if (std::isfinite(dutyCycle)) {
+    dutyCycle = std::clamp(dutyCycle, -1.0, 1.0);
   } else {
-    speed = 0.0;
+    dutyCycle = 0.0;
   }
 
-  if (m_simSpeed) {
-    m_simSpeed.Set(speed);
+  if (m_simDutyCycle) {
+    m_simDutyCycle.Set(dutyCycle);
   }
 
   wpi::units::microsecond_t rawValue;
-  if (speed == 0.0) {
+  if (dutyCycle == 0.0) {
     rawValue = m_centerPwm;
-  } else if (speed > 0.0) {
-    rawValue = wpi::units::microsecond_t{static_cast<double>(
-                   std::lround((speed * GetPositiveScaleFactor()).value()))} +
+  } else if (dutyCycle > 0.0) {
+    rawValue = wpi::units::microsecond_t{static_cast<double>(std::lround(
+                   (dutyCycle * GetPositiveScaleFactor()).value()))} +
                GetMinPositivePwm();
   } else {
-    rawValue = wpi::units::microsecond_t{static_cast<double>(
-                   std::lround((speed * GetNegativeScaleFactor()).value()))} +
+    rawValue = wpi::units::microsecond_t{static_cast<double>(std::lround(
+                   (dutyCycle * GetNegativeScaleFactor()).value()))} +
                GetMaxNegativePwm();
   }
 
   m_pwm.SetPulseTime(rawValue);
 }
 
-double PWMMotorController::GetSpeed() const {
+double PWMMotorController::GetDutyCycleInternal() const {
   wpi::units::microsecond_t rawValue = m_pwm.GetPulseTime();
 
   if (rawValue == 0_us) {

wpilibc/src/main/native/cpp/hardware/rotation/Encoder.cpp

@@ -150,7 +150,8 @@ void Encoder::InitSendable(wpi::util::SendableBuilder& builder) {
     builder.SetSmartDashboardType("Encoder");
   }
 
-  builder.AddDoubleProperty("Speed", [=, this] { return GetRate(); }, nullptr);
+  builder.AddDoubleProperty(
+      "Velocity", [=, this] { return GetRate(); }, nullptr);
   builder.AddDoubleProperty(
       "Distance", [=, this] { return GetDistance(); }, nullptr);
   builder.AddDoubleProperty(