1.1 Lane Change Decider

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Lane Change Decider

File Path: modules/planning/tasks/deciders/lane_change_decider/lane_change_decider.cc

首先取出上一刻的换道状态prev_status 

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auto* prev_status = injector_->planning_context()
                          ->mutable_planning_status()
                          ->mutable_change_lane();
prev_status是定义在proto中的结构体(modules/planning/proto/planning_status.proto) 包括： Status - IN_CHANGE_LANE、CHANGE_LANE_FAILED 、CHANGE_LANE_FINISHED path_id、timestamp

exist_lane_change_start_position - 换道起点flag lane_change_start_postion - 换道起点

last_succeed_timestamp

is_current_opt_succeed - path和speed是否规划成功 is_clear_to_change_lane - 周围环境是否clear 

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message ChangeLaneStatus {
  enum Status {
    IN_CHANGE_LANE = 1;        // during change lane state
    CHANGE_LANE_FAILED = 2;    // change lane failed
    CHANGE_LANE_FINISHED = 3;  // change lane finished
  }
  optional Status status = 1;
  // the id of the route segment that the vehicle is driving on
  optional string path_id = 2;
  // the time stamp when the state started.
  optional double timestamp = 3;
  // the starting position only after which lane-change can happen.
  optional bool exist_lane_change_start_position = 4 [default = false];
  optional apollo.common.Point3D lane_change_start_position = 5;
  // the last time stamp when the lane-change planning succeed.
  optional double last_succeed_timestamp = 6;
  // if the current path and speed planning on the lane-change
  // reference-line succeed.
  optional bool is_current_opt_succeed = 7 [default = false];
  // denotes if the surrounding area is clear for ego vehicle to
  // change lane at this moment.
  optional bool is_clear_to_change_lane = 8 [default = false];
}
将初始状态初始化为CHANGE_LANE_FINISHED： 
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if (!prev_status->has_status()) {
  UpdateStatus(now, ChangeLaneStatus::CHANGE_LANE_FINISHED,
               GetCurrentPathId(*reference_line_info));
  prev_status->set_last_succeed_timestamp(now);
  return Status::OK();
}
在有多条参考线的情况下认为可以换道 bool has_change_lane = reference_line_info->size() > 1; 然后进行换道状态的判断，逻辑框图大致如下：

更新状态后Lane_Change_Decider就跑完了。

相关内容：

  1. 这里有个疑问，reference_line_info > 1时就直接进入IN_CHANGE_LANE了， 也就是说只有在需要换道时，routing才会给出多条参考线吗？

  2. 在lane_change_decider的配置中有一项reckless_change_line,默认关闭，打开后直接执行优先换道然后退出task，和正常的相比少了failed_freeze_time和success_freeze_time.

  3. PrioritizeChangeLane（）函数，传True表示优先处理换道path，False表示优先处理当前path。 具体做法为：遍历Reference_line_inf（std::list type），找到第一个符合要求的path（True- ischangelane || False - is not changelane），将它插回Reference_line_info的头部 代码： 

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    auto iter = reference_line_info->begin();
      while (iter != reference_line_info->end()) {
        ADEBUG << "iter->IsChangeLanePath(): " << iter->IsChangeLanePath();
        /* is_prioritize_change_lane == true: prioritize change_lane_reference_line
           is_prioritize_change_lane == false: prioritize
           non_change_lane_reference_line */
        if ((is_prioritize_change_lane && iter->IsChangeLanePath()) ||
            (!is_prioritize_change_lane && !iter->IsChangeLanePath())) {
          ADEBUG << "is_prioritize_change_lane: " << is_prioritize_change_lane;
          ADEBUG << "iter->IsChangeLanePath(): " << iter->IsChangeLanePath();
          break;
        }
        ++iter;
      }
      reference_line_info->splice(reference_line_info->begin(),
                                  *reference_line_info, iter);
    链接：std::list::splice on cppreference