[docs] Fix wpilibj JavaDoc warnings (#6154)

wpilibc/src/main/native/include/frc/simulation/DifferentialDrivetrainSim.h

@@ -187,6 +187,13 @@ class DifferentialDrivetrainSim {
    */
   void SetPose(const frc::Pose2d& pose);
 
+  /**
+   * The differential drive dynamics function.
+   *
+   * @param x The state.
+   * @param u The input.
+   * @return The state derivative with respect to time.
+   */
   Vectord<7> Dynamics(const Vectord<7>& x, const Eigen::Vector2d& u);
 
   class State {

wpilibc/src/main/native/include/frc/simulation/GenericHIDSim.h

@@ -136,6 +136,7 @@ class GenericHIDSim {
   double GetRumble(GenericHID::RumbleType type);
 
  protected:
+  /// GenericHID port.
   int m_port;
 };
 

wpilibc/src/main/native/include/frc/simulation/LinearSystemSim.h

@@ -140,11 +140,20 @@ class LinearSystemSim {
         u, frc::RobotController::GetInputVoltage());
   }
 
+  /// The plant that represents the linear system.
   LinearSystem<States, Inputs, Outputs> m_plant;
 
+  /// State vector.
   Vectord<States> m_x;
-  Vectord<Outputs> m_y;
+
+  /// Input vector.
   Vectord<Inputs> m_u;
+
+  /// Output vector.
+  Vectord<Outputs> m_y;
+
+  /// The standard deviations of measurements, used for adding noise to the
+  /// measurements.
   std::array<double, Outputs> m_measurementStdDevs;
 };
 }  // namespace frc::sim

wpilibc/src/main/native/include/frc/simulation/PneumaticsBaseSim.h

@@ -177,9 +177,22 @@ class PneumaticsBaseSim {
   virtual void ResetData() = 0;
 
  protected:
+  /// PneumaticsBase index.
   const int m_index;
-  explicit PneumaticsBaseSim(const PneumaticsBase& module);
+
+  /**
+   * Constructs a PneumaticsBaseSim with the given index.
+   *
+   * @param index The index.
+   */
   explicit PneumaticsBaseSim(const int index);
+
+  /**
+   * Constructs a PneumaticsBaseSim for the given module.
+   *
+   * @param module The module.
+   */
+  explicit PneumaticsBaseSim(const PneumaticsBase& module);
 };
 
 }  // namespace frc::sim

wpilibc/src/main/native/include/frc/simulation/UltrasonicSim.h

@@ -36,14 +36,14 @@ class UltrasonicSim {
   /**
    * Sets if the range measurement is valid.
    *
-   * @param isValid True if valid
+   * @param valid True if valid
    */
-  void SetRangeValid(bool isValid);
+  void SetRangeValid(bool valid);
 
   /**
-   * Sets the range measurement
+   * Sets the range measurement.
    *
-   * @param range The range
+   * @param range The range.
    */
   void SetRange(units::inch_t range);