fix(simple_planning_simulator): set ego pitch to 0 if road slope is n…

…ot simulated (autowarefoundation#5501) (autowarefoundation#1027)

set ego pitch to 0 if road slope is not simulated

Signed-off-by: Daniel Sanchez <danielsanchezaran@gmail.com>
Co-authored-by: danielsanchezaran <daniel.sanchez@tier4.jp>

simulator/simple_planning_simulator/src/simple_planning_simulator/simple_planning_simulator_core.cpp

@@ -321,9 +321,9 @@ void SimplePlanningSimulator::on_timer()
   }
 
   // calculate longitudinal acceleration by slope
-  const double ego_pitch_angle = calculate_ego_pitch();
-  const double acc_by_slope =
-    enable_road_slope_simulation_ ? -9.81 * std::sin(ego_pitch_angle) : 0.0;
+  constexpr double gravity_acceleration = -9.81;
+  const double ego_pitch_angle = enable_road_slope_simulation_ ? calculate_ego_pitch() : 0.0;
+  const double acc_by_slope = gravity_acceleration * std::sin(ego_pitch_angle);
 
   // update vehicle dynamics
   {