Planning: [lattice] separate yield and ovetake buffer in collision cost function

modules/planning/common/planning_gflags.cc

@@ -409,6 +409,9 @@ DEFINE_double(weight_opposite_side_offset, 10.0,
 DEFINE_double(weight_dist_travelled, 10.0, "Weight of travelled distance cost");
 DEFINE_double(weight_target_speed, 1.0, "Weight of target speed cost");
 DEFINE_double(lat_offset_bound, 3.0, "The bound of lateral offset");
-DEFINE_double(lon_collision_buffer, 1.0, "Longitudinal collision buffer");
+DEFINE_double(lon_collision_yield_buffer, 1.0,
+              "Longitudinal collision buffer for yield");
+DEFINE_double(lon_collision_overtake_buffer, 5.0,
+              "Longitudinal collision buffer for overtake");
 DEFINE_double(lon_collision_cost_std, 0.5,
               "The standard deviation of logitudinal collision cost function");

modules/planning/common/planning_gflags.h

@@ -217,7 +217,8 @@ DECLARE_double(weight_opposite_side_offset);
 DECLARE_double(weight_dist_travelled);
 DECLARE_double(weight_target_speed);
 DECLARE_double(lat_offset_bound);
-DECLARE_double(lon_collision_buffer);
+DECLARE_double(lon_collision_yield_buffer);
+DECLARE_double(lon_collision_overtake_buffer);
 DECLARE_double(lon_collision_cost_std);
 
 #endif  // MODULES_PLANNING_COMMON_PLANNING_GFLAGS_H

modules/planning/lattice/trajectory_generator/trajectory_evaluator.cc

@@ -233,14 +233,14 @@ double TrajectoryEvaluator::LonCollisionCost(
     double sigma = FLAGS_lon_collision_cost_std;
     for (const auto& m : pt_interval) {
       double cost = 0.0;
-      if (traj_s > m.first - FLAGS_lon_collision_buffer &&
-          traj_s < m.second + FLAGS_lon_collision_buffer) {
+      if (traj_s > m.first - FLAGS_lon_collision_yield_buffer &&
+          traj_s < m.second + FLAGS_lon_collision_overtake_buffer) {
         cost = 1.0;
       } else if (traj_s < m.first) {
-        double dist = traj_s - m.first + FLAGS_lon_collision_buffer;
+        double dist = (m.first - FLAGS_lon_collision_yield_buffer) - traj_s;
         cost = std::exp(-dist * dist / (2.0 * sigma * sigma));
       } else if (traj_s > m.second) {
-        double dist = m.second + FLAGS_lon_collision_buffer - traj_s;
+        double dist = traj_s - (m.second + FLAGS_lon_collision_overtake_buffer);
         cost = std::exp(-dist * dist / (2.0 * sigma * sigma));
       }
       cost_sqr_sum += cost * cost;