[wpilib] Clamp input voltage in sim classes (#2955)

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

@@ -72,6 +72,16 @@ class DifferentialDrivetrainSim {
       units::meter_t trackWidth,
       const std::array<double, 7>& measurementStdDevs = {});
 
+  /**
+   * Clamp the input vector such that no element exceeds the given voltage. If
+   * any does, the relative magnitudes of the input will be maintained.
+   *
+   * @param u          The input vector.
+   * @param maxVoltage The maximum voltage.
+   * @return The normalized input.
+   */
+  Eigen::Matrix<double, 2, 1> ClampInput(Eigen::Matrix<double, 2, 1> u);
+
   /**
    * Sets the applied voltage to the drivetrain. Note that positive voltage must
    * make that side of the drivetrain travel forward (+X).