Prediction: use free move predictor for slow obstacles

modules/prediction/common/prediction_gflags.cc

@@ -108,6 +108,8 @@ DEFINE_double(still_pedestrian_position_std, 0.5,
               "Position standard deviation for still pedestrians");
 DEFINE_double(still_unknown_position_std, 0.5,
               "Position standard deviation for still unknown obstacles");
+DEFINE_double(slow_obstacle_speed_threshold, 2.0,
+              "Speed threshold for slow obstacles");
 DEFINE_double(max_history_time, 7.0, "Obstacles' maximal historical time.");
 DEFINE_double(target_lane_gap, 2.0, "Gap between two lane points.");
 DEFINE_double(dense_lane_gap, 0.2,

modules/prediction/common/prediction_gflags.h

@@ -72,6 +72,7 @@ DECLARE_double(still_unknown_speed_threshold);
 DECLARE_double(still_obstacle_position_std);
 DECLARE_double(still_pedestrian_position_std);
 DECLARE_double(still_unknown_position_std);
+DECLARE_double(slow_obstacle_speed_threshold);
 DECLARE_double(max_history_time);
 DECLARE_double(target_lane_gap);
 DECLARE_double(dense_lane_gap);

modules/prediction/container/obstacles/obstacle.cc

@@ -100,6 +100,11 @@ bool Obstacle::IsStill() {
   return true;
 }
 
+bool Obstacle::IsSlow() {
+  const Feature& feature = latest_feature();
+  return feature.speed() < FLAGS_slow_obstacle_speed_threshold;
+}
+
 bool Obstacle::IsOnLane() const {
   if (feature_history_.size() > 0) {
     if (feature_history_.front().has_lane() &&

modules/prediction/container/obstacles/obstacle.h

@@ -151,6 +151,12 @@ class Obstacle {
    */
   bool IsStill();
 
+  /**
+   * @brief Check if the obstacle is slow.
+   * @return If the obstacle is slow.
+   */
+  bool IsSlow();
+
   /**
    * @brief Check if the obstacle is on any lane.
    * @return If the obstacle is on any lane.

modules/prediction/predictor/predictor_manager.cc

@@ -270,7 +270,10 @@ void PredictorManager::PredictObstacle(
   } else {
     switch (obstacle->type()) {
       case PerceptionObstacle::VEHICLE: {
-        if (obstacle->HasJunctionFeatureWithExits() &&
+        if (obstacle->IsSlow()) {
+          predictor = GetPredictor(ObstacleConf::FREE_MOVE_PREDICTOR);
+          CHECK_NOTNULL(predictor);
+        } else if (obstacle->HasJunctionFeatureWithExits() &&
             !obstacle->IsCloseToJunctionExit()) {
           predictor = GetPredictor(vehicle_in_junction_predictor_);
           CHECK_NOTNULL(predictor);