MoveBase源码阅读笔记

1 构造函数 MoveBase

构造函数MoveBase::MoveBase()为该节点的入口，初始化了相关变量，加载recovery behaviors，局部和全局的地图、路径规划器等plugin，以及开启服务和线程等。该函数中定义了多个ros::NodeHandle变量，其作用主要是给出开话题的命名空间和区分私有话题（内部线程间通信），具体可参考ros官网的说明和ros::NodeHandle博客,rosrun move_base move_base后可以看到其节点的话题情况。

ros::NodeHandle private_nh("~");
ros::NodeHandle nh;

构造函数中采用了actionlib给出了可中断、及时反馈状态的服务接口, executeCb()为服务回调函数。对外给出了导航目标点话题为/move_base_simple/goal ，在goalCB()回调函数中给将其转化为as_服务器的MoveBaseActionGoal格式目标，并发布到话题/move_base/goal，其实该话题为就是actionlib服务器的目标话题，从而进入executeCb()回调函数（与官方例程中定义客户端发送目标不同，个人认为原理上就是订阅该目标话题进入回调函数）。

as_ = new MoveBaseActionServer(ros::NodeHandle(), "move_base", boost::bind(&MoveBase::executeCb, this, _1), false);
ros::NodeHandle simple_nh("move_base_simple");
goal_sub_ = simple_nh.subscribe<geometry_msgs::PoseStamped>("goal", 1, boost::bind(&MoveBase::goalCB, this, _1));

开启了规划线程planThread()函数：

//set up the planner's thread
planner_thread_ = new boost::thread(boost::bind(&MoveBase::planThread, this));

发布两个服务，规划和清除地图;

//advertise a service for getting a plan
make_plan_srv_ = private_nh.advertiseService("make_plan", &MoveBase::planService, this);
//advertise a service for clearing the costmaps
clear_costmaps_srv_ = private_nh.advertiseService("clear_costmaps", &MoveBase::clearCostmapsService, this);

2 目标点action服务回调函数 executeCb

代码如下，得到新的目标位置会唤醒planThread规划全局路径，整体状态的操作在executeCycle函数中执行，在循环中一直执行。
movebase状态机有三种：

PLANNING 全局路径规划状态
CONTROLLING 局部控制状态
CLEARING 故障恢复状态：故障恢复触发的方式也有三种 PLANNING_R（全局路径规划）, CONTROLLING_R（局部路径规划）, OSCILLATION_R（振荡摆动）

   //　转为全局坐标系位置geometry_msgs::PoseStamped goal = goalToGlobalFrame(move_base_goal->target_pose);//we have a goal so start the planner　唤醒planThread线程开始规划boost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);planner_goal_ = goal;runPlanner_ = true;planner_cond_.notify_one();lock.unlock();ros::NodeHandle n;while(n.ok()){if(as_->isPreemptRequested()){if(as_->isNewGoalAvailable()){//if we're active and a new goal is available, we'll accept it, but we won't shut anything down// 如果目标被抢占且收到新目标，继续在该函数中执行上述操作(个人理解executeCb回调函数没有运行完时收到新目标会继续新的规划和没有终止)move_base_msgs::MoveBaseGoal new_goal = *as_->acceptNewGoal();if(!isQuaternionValid(new_goal.target_pose.pose.orientation)){as_->setAborted(move_base_msgs::MoveBaseResult(), "Aborting on goal because it was sent with an invalid quaternion");return;}goal = goalToGlobalFrame(new_goal.target_pose);//we'll make sure that we reset our state for the next execution cyclerecovery_index_ = 0;state_ = PLANNING;//we have a new goal so make sure the planner is awake　唤醒规划进程lock.lock();planner_goal_ = goal;runPlanner_ = true;planner_cond_.notify_one();lock.unlock();}else {//if we've been preempted explicitly we need to shut things downresetState();//notify the ActionServer that we've successfully preemptedROS_DEBUG_NAMED("move_base","Move base preempting the current goal");as_->setPreempted();//we'll actually return from execute after preempting  终止return;}}//we also want to check if we've changed global frames because we need to transform our goal pose // 检查目标是否改变，若没用继续执行上述操作if(goal.header.frame_id != planner_costmap_ros_->getGlobalFrameID()){goal = goalToGlobalFrame(goal);//we want to go back to the planning state for the next execution cyclerecovery_index_ = 0;state_ = PLANNING;//we have a new goal so make sure the planner is awakelock.lock();planner_goal_ = goal;runPlanner_ = true;planner_cond_.notify_one();lock.unlock();}//for timing that gives real time even in simulationros::WallTime start = ros::WallTime::now();//the real work on pursuing a goal is done here 主要工作在executeCycle()函数中bool done = executeCycle(goal, global_plan);//if we're done, then we'll return from execute  完成目标终止回调if(done)return;//check if execution of the goal has completed in some wayros::WallDuration t_diff = ros::WallTime::now() - start;ROS_DEBUG_NAMED("move_base","Full control cycle time: %.9f\n", t_diff.toSec());r.sleep();//make sure to sleep for the remainder of our cycle timeif(r.cycleTime() > ros::Duration(1 / controller_frequency_) && state_ == CONTROLLING)ROS_WARN("Control loop missed its desired rate of %.4fHz... the loop actually took %.4f seconds", controller_frequency_, r.cycleTime().toSec());}//wake up the planner thread so that it can exit cleanlylock.lock();runPlanner_ = true;planner_cond_.notify_one();lock.unlock();//if the node is killed then we'll abort and returnas_->setAborted(move_base_msgs::MoveBaseResult(), "Aborting on the goal because the node has been killed");return;

3 主循环状态控制函数executeCycle

executeCylcle函数会将新生成的全局路径给到局部控制器，根据状态机对整体状态进行切换，CONTROLLING状态时局部规划器中computeVelocityCommands计算速度。

 //we need to be able to publish velocity commandsgeometry_msgs::Twist cmd_vel;//update feedback to correspond to our curent positiongeometry_msgs::PoseStamped global_pose;getRobotPose(global_pose, planner_costmap_ros_);const geometry_msgs::PoseStamped& current_position = global_pose;//push the feedback out  反馈goal服务状态move_base_msgs::MoveBaseFeedback feedback;feedback.base_position = current_position;as_->publishFeedback(feedback);//check to see if we've moved far enough to reset our oscillation timeout 判断是否振荡TODOif(distance(current_position, oscillation_pose_) >= oscillation_distance_){last_oscillation_reset_ = ros::Time::now();oscillation_pose_ = current_position;//if our last recovery was caused by oscillation, we want to reset the recovery index if(recovery_trigger_ == OSCILLATION_R)recovery_index_ = 0;}//check that the observation buffers for the costmap are current, we don't want to drive blindif(!controller_costmap_ros_->isCurrent()){ROS_WARN("[%s]:Sensor data is out of date, we're not going to allow commanding of the base for safety",ros::this_node::getName().c_str());publishZeroVelocity();return false;}//if we have a new plan then grab it and give it to the controller// 新的全局路径生成给局部控制器if(new_global_plan_){//make sure to set the new plan flag to falsenew_global_plan_ = false;ROS_DEBUG_NAMED("move_base","Got a new plan...swap pointers");//do a pointer swap under mutexstd::vector<geometry_msgs::PoseStamped>* temp_plan = controller_plan_;boost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);controller_plan_ = latest_plan_;latest_plan_ = temp_plan;lock.unlock();ROS_DEBUG_NAMED("move_base","pointers swapped!");if(!tc_->setPlan(*controller_plan_)){//ABORT and SHUTDOWN COSTMAPSROS_ERROR("Failed to pass global plan to the controller, aborting.");resetState();//disable the planner threadlock.lock();runPlanner_ = false;lock.unlock();as_->setAborted(move_base_msgs::MoveBaseResult(), "Failed to pass global plan to the controller.");return true;}//make sure to reset recovery_index_ since we were able to find a valid planif(recovery_trigger_ == PLANNING_R)recovery_index_ = 0;}//the move_base state machine, handles the control logic for navigation状态机导航switch(state_){//if we are in a planning state, then we'll attempt to make a plancase PLANNING:{boost::recursive_mutex::scoped_lock lock(planner_mutex_);runPlanner_ = true;planner_cond_.notify_one();}ROS_DEBUG_NAMED("move_base","Waiting for plan, in the planning state.");break;//if we're controlling, we'll attempt to find valid velocity commandscase CONTROLLING:ROS_DEBUG_NAMED("move_base","In controlling state.");//check to see if we've reached our goalif(tc_->isGoalReached()){ROS_DEBUG_NAMED("move_base","Goal reached!");resetState();//disable the planner threadboost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);runPlanner_ = false;lock.unlock();as_->setSucceeded(move_base_msgs::MoveBaseResult(), "Goal reached.");return true;}//check for an oscillation conditionif(oscillation_timeout_ > 0.0 &&last_oscillation_reset_ + ros::Duration(oscillation_timeout_) < ros::Time::now()){publishZeroVelocity();state_ = CLEARING;recovery_trigger_ = OSCILLATION_R;}{boost::unique_lock<costmap_2d::Costmap2D::mutex_t> lock(*(controller_costmap_ros_->getCostmap()->getMutex()));// 计算速度if(tc_->computeVelocityCommands(cmd_vel)){ROS_DEBUG_NAMED( "move_base", "Got a valid command from the local planner: %.3lf, %.3lf, %.3lf",cmd_vel.linear.x, cmd_vel.linear.y, cmd_vel.angular.z );last_valid_control_ = ros::Time::now();//make sure that we send the velocity command to the basevel_pub_.publish(cmd_vel);if(recovery_trigger_ == CONTROLLING_R)recovery_index_ = 0;}else {ROS_DEBUG_NAMED("move_base", "The local planner could not find a valid plan.");ros::Time attempt_end = last_valid_control_ + ros::Duration(controller_patience_);//check if we've tried to find a valid control for longer than our time limitif(ros::Time::now() > attempt_end){//we'll move into our obstacle clearing modepublishZeroVelocity();state_ = CLEARING;recovery_trigger_ = CONTROLLING_R;}else{//otherwise, if we can't find a valid control, we'll go back to planninglast_valid_plan_ = ros::Time::now();planning_retries_ = 0;state_ = PLANNING;publishZeroVelocity();//enable the planner thread in case it isn't running on a clockboost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);runPlanner_ = true;planner_cond_.notify_one();lock.unlock();}}}break;//we'll try to clear out space with any user-provided recovery behaviorscase CLEARING:ROS_DEBUG_NAMED("move_base","In clearing/recovery state");//we'll invoke whatever recovery behavior we're currently on if they're enabledif(recovery_behavior_enabled_ && recovery_index_ < recovery_behaviors_.size()){ROS_DEBUG_NAMED("move_base_recovery","Executing behavior %u of %zu", recovery_index_, recovery_behaviors_.size());recovery_behaviors_[recovery_index_]->runBehavior();//we at least want to give the robot some time to stop oscillating after executing the behaviorlast_oscillation_reset_ = ros::Time::now();//we'll check if the recovery behavior actually workedROS_DEBUG_NAMED("move_base_recovery","Going back to planning state");last_valid_plan_ = ros::Time::now();planning_retries_ = 0;state_ = PLANNING;//update the index of the next recovery behavior that we'll tryrecovery_index_++;}else{ROS_DEBUG_NAMED("move_base_recovery","All recovery behaviors have failed, locking the planner and disabling it.");//disable the planner threadboost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);runPlanner_ = false;lock.unlock();ROS_DEBUG_NAMED("move_base_recovery","Something should abort after this.");if(recovery_trigger_ == CONTROLLING_R){ROS_ERROR("Aborting because a valid control could not be found. Even after executing all recovery behaviors");as_->setAborted(move_base_msgs::MoveBaseResult(), "Failed to find a valid control. Even after executing recovery behaviors.");}else if(recovery_trigger_ == PLANNING_R){ROS_ERROR("Aborting because a valid plan could not be found. Even after executing all recovery behaviors");as_->setAborted(move_base_msgs::MoveBaseResult(), "Failed to find a valid plan. Even after executing recovery behaviors.");}else if(recovery_trigger_ == OSCILLATION_R){ROS_ERROR("Aborting because the robot appears to be oscillating over and over. Even after executing all recovery behaviors");as_->setAborted(move_base_msgs::MoveBaseResult(), "Robot is oscillating. Even after executing recovery behaviors.");}resetState();return true;}break;default:ROS_ERROR("This case should never be reached, something is wrong, aborting");resetState();//disable the planner threadboost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);runPlanner_ = false;lock.unlock();as_->setAborted(move_base_msgs::MoveBaseResult(), "Reached a case that should not be hit in move_base. This is a bug, please report it.");return true;}//we aren't done yetreturn false;

4 全局规划线程 planThread

代码如下，其中调用 makePlan函数进行全局规划 planner_->makePlan(start, goal, plan)

ros::NodeHandle n;ros::Timer timer;bool wait_for_wake = false;boost::unique_lock<boost::recursive_mutex> lock(planner_mutex_);while(n.ok()){//check if we should run the planner (the mutex is locked) 等待唤醒同步while(wait_for_wake || !runPlanner_){//if we should not be running the planner then suspend this threadROS_DEBUG_NAMED("move_base_plan_thread","Planner thread is suspending");planner_cond_.wait(lock);wait_for_wake = false;}ros::Time start_time = ros::Time::now();//time to plan! get a copy of the goal and unlock the mutex  规划开始geometry_msgs::PoseStamped temp_goal = planner_goal_;lock.unlock();ROS_DEBUG_NAMED("move_base_plan_thread","Planning...");//run plannerplanner_plan_->clear();bool gotPlan = n.ok() && makePlan(temp_goal, *planner_plan_);   // 全局规划函数if(gotPlan){   //规划成功ROS_DEBUG_NAMED("move_base_plan_thread","Got Plan with %zu points!", planner_plan_->size());//pointer swap the plans under mutex (the controller will pull from latest_plan_)std::vector<geometry_msgs::PoseStamped>* temp_plan = planner_plan_;lock.lock();planner_plan_ = latest_plan_;latest_plan_ = temp_plan;last_valid_plan_ = ros::Time::now();planning_retries_ = 0;new_global_plan_ = true;  // 新的全局规划路径//make sure we only start the controller if we still haven't reached the goalif(runPlanner_)state_ = CONTROLLING;if(planner_frequency_ <= 0)runPlanner_ = false;lock.unlock();}//if we didn't get a plan and we are in the planning state (the robot isn't moving)// 全局路径规划失败else if(state_==PLANNING){ROS_DEBUG_NAMED("move_base_plan_thread","No Plan...");ros::Time attempt_end = last_valid_plan_ + ros::Duration(planner_patience_);//check if we've tried to make a plan for over our time limit or our maximum number of retries//issue #496: we stop planning when one of the conditions is true, but if max_planning_retries_//is negative (the default), it is just ignored and we have the same behavior as everlock.lock();planning_retries_++;// 若规划时间超时或次数超限 则进入 CLEARING状态， recovery 恢复模式if(runPlanner_ &&(ros::Time::now() > attempt_end || planning_retries_ > uint32_t(max_planning_retries_))){//we'll move into our obstacle clearing modestate_ = CLEARING;runPlanner_ = false;  // proper solution for issue #523publishZeroVelocity();recovery_trigger_ = PLANNING_R;}lock.unlock();}//take the mutex for the next iterationlock.lock();//setup sleep interface if neededif(planner_frequency_ > 0){ros::Duration sleep_time = (start_time + ros::Duration(1.0/planner_frequency_)) - ros::Time::now();if (sleep_time > ros::Duration(0.0)){wait_for_wake = true;// 小于要求的规划时间，则sleep多余的时间来唤醒该进程， wait_for_wake为True后下一个循环线程将进入等待// 状态，定时器函数wakePlanner将唤醒本线程，若planner_frequency=0则只在有新目标时候才唤醒本线程timer = n.createTimer(sleep_time, &MoveBase::wakePlanner, this);}}}