RobotNavigator.cpp

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#include <nav2d_operator/cmd.h>
#include <nav_msgs/GridCells.h>
#include <visualization_msgs/Marker.h>

#include <nav2d_navigator/RobotNavigator.h>
#include <nav2d_navigator/ExplorationPlanner.h>

#include <set>
#include <map>

#define PI 3.14159265

using namespace ros;
using namespace tf;

RobotNavigator::RobotNavigator()
{       
        NodeHandle robotNode;

        std::string serviceName;
        robotNode.param("map_service", serviceName, std::string("get_map"));
        mGetMapClient = robotNode.serviceClient<nav_msgs::GetMap>(serviceName);

        mCommandPublisher = robotNode.advertise<nav2d_operator::cmd>("cmd", 1);
        mStopServer = robotNode.advertiseService(NAV_STOP_SERVICE, &RobotNavigator::receiveStop, this);
        mPauseServer = robotNode.advertiseService(NAV_PAUSE_SERVICE, &RobotNavigator::receivePause, this);
        mCurrentPlan = NULL;

        NodeHandle navigatorNode("~/");
        mPlanPublisher = navigatorNode.advertise<nav_msgs::GridCells>("plan", 1);
        mMarkerPublisher = navigatorNode.advertise<visualization_msgs::Marker>("markers", 1, true);
        
        // Get parameters
        navigatorNode.param("map_inflation_radius", mInflationRadius, 1.0);
        navigatorNode.param("robot_radius", mRobotRadius, 0.3);
        navigatorNode.param("exploration_strategy", mExplorationStrategy, std::string("NearestFrontierPlanner"));
        navigatorNode.param("navigation_goal_distance", mNavigationGoalDistance, 1.0);
        navigatorNode.param("navigation_goal_angle", mNavigationGoalAngle, 1.0);
        navigatorNode.param("exploration_goal_distance", mExplorationGoalDistance, 3.0);
        navigatorNode.param("navigation_homing_distance", mNavigationHomingDistance, 3.0);
        navigatorNode.param("min_replanning_period", mMinReplanningPeriod, 3.0);
        navigatorNode.param("max_replanning_period", mMaxReplanningPeriod, 1.0);
        navigatorNode.param("command_target_distance", mCommandTargetDistance, 1.0);
        navigatorNode.param("frequency", mFrequency, 10.0);
        mCostObstacle = 100;
        mCostLethal = (1.0 - (mRobotRadius / mInflationRadius)) * (double)mCostObstacle;

        robotNode.param("map_frame", mMapFrame, std::string("map"));
        robotNode.param("robot_frame", mRobotFrame, std::string("robot"));
        robotNode.param("robot_id", mRobotID, 1);
        robotNode.param("move_action_topic", mMoveActionTopic, std::string(NAV_MOVE_ACTION));
        robotNode.param("explore_action_topic", mExploreActionTopic, std::string(NAV_EXPLORE_ACTION));
        robotNode.param("getmap_action_topic", mGetMapActionTopic, std::string(NAV_GETMAP_ACTION));
        robotNode.param("localize_action_topic", mLocalizeActionTopic, std::string(NAV_LOCALIZE_ACTION));

        // Apply tf_prefix to all used frame-id's
        mRobotFrame = mTfListener.resolve(mRobotFrame);
        mMapFrame = mTfListener.resolve(mMapFrame);

        try
        {
                mPlanLoader = new PlanLoader("nav2d_navigator", "ExplorationPlanner");
                mExplorationPlanner = mPlanLoader->createInstance(mExplorationStrategy);
                ROS_INFO("Successfully loaded exploration strategy [%s].", mExplorationStrategy.c_str());

                mExploreActionServer = new ExploreActionServer(mExploreActionTopic, boost::bind(&RobotNavigator::receiveExploreGoal, this, _1), false);
                mExploreActionServer->start();
        }
        catch(pluginlib::PluginlibException& ex)
        {
                ROS_ERROR("Failed to load exploration plugin! Error: %s", ex.what());
                mExploreActionServer = NULL;
                mPlanLoader = NULL;
        }

        // Create action servers
        mMoveActionServer = new MoveActionServer(mMoveActionTopic, boost::bind(&RobotNavigator::receiveMoveGoal, this, _1), false);
        mMoveActionServer->start();
        
        mLocalizeActionServer = new LocalizeActionServer(mLocalizeActionTopic, boost::bind(&RobotNavigator::receiveLocalizeGoal, this, _1), false);
        mLocalizeActionServer->start();
        
        if(mRobotID == 1)
        {
                mGetMapActionServer = new GetMapActionServer(mGetMapActionTopic, boost::bind(&RobotNavigator::receiveGetMapGoal, this, _1), false);
                mGetMapActionServer->start();
        }else
        {
                mGetMapActionServer = NULL;
        }
        
        mHasNewMap = false;
        mIsStopped = false;
        mIsPaused = false;
        mStatus = NAV_ST_IDLE;
        mCellInflationRadius = 0;
}

RobotNavigator::~RobotNavigator()
{
        delete[] mCurrentPlan;
        delete mMoveActionServer;
        delete mExploreActionServer;
        delete mGetMapActionServer;
        mExplorationPlanner.reset();
        delete mPlanLoader;
}

bool RobotNavigator::getMap()
{       
        if(mHasNewMap) return true;
        
        if(!mGetMapClient.isValid())
        {
                ROS_ERROR("GetMap-Client is invalid!");
                return false;
        }
        
        nav_msgs::GetMap srv;
        if(!mGetMapClient.call(srv))
        {
                ROS_INFO("Could not get a map.");
                return false;
        }
        mCurrentMap.update(srv.response.map);
        
        if(mCurrentPlan) delete[] mCurrentPlan;
        mCurrentPlan = new double[mCurrentMap.getSize()];
        
        if(mCellInflationRadius == 0)
        {
                ROS_INFO("Navigator is now initialized.");
                mCellInflationRadius = mInflationRadius / mCurrentMap.getResolution();
                mCellRobotRadius = mRobotRadius / mCurrentMap.getResolution();
                mInflationTool.computeCaches(mCellInflationRadius);
                mCurrentMap.setLethalCost(mCostLethal);
        }
        
        mHasNewMap = true;
        return true;
}

bool RobotNavigator::receiveStop(std_srvs::Trigger::Request &req, std_srvs::Trigger::Response &res)
{
        mIsStopped = true;
        res.success = true;
        res.message = "Navigator received stop signal.";
        return true;
}

bool RobotNavigator::receivePause(std_srvs::Trigger::Request &req, std_srvs::Trigger::Response &res)
{       
        if(mIsPaused)
        {
                mIsPaused = false;
                res.success = false;
                res.message = "Navigator continues.";
        }else
        {
                mIsPaused = true;
                nav2d_operator::cmd stopMsg;
                stopMsg.Turn = 0;
                stopMsg.Velocity = 0;
                mCommandPublisher.publish(stopMsg);
                res.success = true;
                res.message = "Navigator pauses.";
        }
        return true;
}

typedef std::multimap<double,unsigned int> Queue;
typedef std::pair<double,unsigned int> Entry;

bool RobotNavigator::preparePlan()
{
        // Get the current map
        if(!getMap()) // return false;
        {
                if(mCellInflationRadius == 0) return false;
                ROS_WARN("Could not get a new map, trying to go with the old one...");
        }
        
        // Where am I?
        if(!setCurrentPosition()) return false;
        
        // Clear robot footprint in map
        unsigned int x = 0, y = 0;
        if(mCurrentMap.getCoordinates(x, y, mStartPoint))
                for(int i = -mCellRobotRadius; i < (int)mCellRobotRadius; i++)
                        for(int j = -mCellRobotRadius; j < (int)mCellRobotRadius; j++)
                                mCurrentMap.setData(x+i, y+j, 0);
        
        mInflationTool.inflateMap(&mCurrentMap);
        return true;
}

bool RobotNavigator::createPlan()
{       
        ROS_DEBUG("Map-Value of goal point is %d, lethal threshold is %d.", mCurrentMap.getData(mGoalPoint), mCostLethal);
        
        unsigned int goal_x = 0, goal_y = 0;
        if(mCurrentMap.getCoordinates(goal_x,goal_y,mGoalPoint))
        {
                visualization_msgs::Marker marker;
                marker.header.frame_id = "/map";
                marker.header.stamp = ros::Time();
                marker.id = 0;
                marker.type = visualization_msgs::Marker::CYLINDER;
                marker.action = visualization_msgs::Marker::ADD;
                marker.pose.position.x = mCurrentMap.getOriginX() + (((double)goal_x+0.5) * mCurrentMap.getResolution());
                marker.pose.position.y = mCurrentMap.getOriginY() + (((double)goal_y+0.5) * mCurrentMap.getResolution());
                marker.pose.position.z = 0.5;
                marker.pose.orientation.x = 0.0;
                marker.pose.orientation.y = 0.0;
                marker.pose.orientation.z = 0.0;
                marker.pose.orientation.w = 1.0;
                marker.scale.x = mCurrentMap.getResolution() * 3.0;
                marker.scale.y = mCurrentMap.getResolution() * 3.0;
                marker.scale.z = 1.0;
                marker.color.a = 1.0;
                marker.color.r = 1.0;
                marker.color.g = 0.0;
                marker.color.b = 0.0;
                mMarkerPublisher.publish(marker);
        }else
        {
                ROS_ERROR("Couldn't ressolve goal point coordinates!");
        }
        
        Queue queue;
        
        // Reset the plan
        int mapSize = mCurrentMap.getSize();
        for(int i = 0; i < mapSize; i++)
        {
                mCurrentPlan[i] = -1;
        }

        if(mCurrentMap.isFree(mGoalPoint))
        {
                queue.insert(Entry(0.0, mGoalPoint));
                mCurrentPlan[mGoalPoint] = 0;
        }else
        {
                // Initialize the queue with area around the goal point
                int reach = mCellRobotRadius + (1.0 / mCurrentMap.getResolution());
                std::vector<unsigned int> neighbors = mCurrentMap.getFreeNeighbors(mGoalPoint, reach);
                for(unsigned int i = 0; i < neighbors.size(); i++)
                {
                        queue.insert(Entry(0.0, neighbors[i]));
                        mCurrentPlan[neighbors[i]] = 0;
                }
        }
        
        Queue::iterator next;
        double distance;
        unsigned int x, y, index;
        double linear = mCurrentMap.getResolution();
        double diagonal = std::sqrt(2.0) * linear;
        
        // Do full search with Dijkstra-Algorithm
        while(!queue.empty())
        {
                // Get the nearest cell from the queue
                next = queue.begin();
                distance = next->first;
                index = next->second;
                queue.erase(next);
                
                if(mCurrentPlan[index] >= 0 && mCurrentPlan[index] < distance) continue;
                
//              if(index == mStartPoint) break;
                
                // Add all adjacent cells
                if(!mCurrentMap.getCoordinates(x, y, index)) continue;
                std::vector<unsigned int> ind;
                ind.push_back(index - 1);
                ind.push_back(index + 1);
                ind.push_back(index - mCurrentMap.getWidth());
                ind.push_back(index + mCurrentMap.getWidth());
                ind.push_back(index - mCurrentMap.getWidth() - 1);
                ind.push_back(index - mCurrentMap.getWidth() + 1);
                ind.push_back(index + mCurrentMap.getWidth() - 1);
                ind.push_back(index + mCurrentMap.getWidth() + 1);
                        
                for(unsigned int it = 0; it < ind.size(); it++)
                {
                        unsigned int i = ind[it];
                        if(mCurrentMap.isFree(i))
                        {
                                double delta = (it < 4) ? linear : diagonal;
                                double newDistance = distance + delta + (10 * delta * (double)mCurrentMap.getData(i) / (double)mCostObstacle);
                                if(mCurrentPlan[i] == -1 || newDistance < mCurrentPlan[i])
                                {
                                        queue.insert(Entry(newDistance, i));
                                        mCurrentPlan[i] = newDistance;
                                }
                        }
                }
        }
        
        if(mCurrentPlan[mStartPoint] < 0)
        {
                ROS_ERROR("No way between robot and goal!");
                return false;
        }
        
        publishPlan();
        return true;
}

void RobotNavigator::publishPlan()
{
        nav_msgs::GridCells plan_msg;
        plan_msg.header.frame_id = mMapFrame.c_str();
        plan_msg.header.stamp = Time::now();
        
        plan_msg.cell_width = mCurrentMap.getResolution();
        plan_msg.cell_height = mCurrentMap.getResolution();
        
        unsigned int index = mStartPoint;
        std::vector<std::pair<double, double> > points;
        while(true)
        {
                unsigned int x = 0, y = 0;
                if(mCurrentMap.getCoordinates(x,y,index))
                        points.push_back(std::pair<double, double>(
                                ((x+0.5) * mCurrentMap.getResolution()) + mCurrentMap.getOriginX(), 
                                ((y+0.5) * mCurrentMap.getResolution()) + mCurrentMap.getOriginY()
                        ));

                if(mCurrentPlan[index] == 0) break;
                
                unsigned int next_index = index;
                
                std::vector<unsigned int> neighbors = mCurrentMap.getFreeNeighbors(index);
                for(unsigned int i = 0; i < neighbors.size(); i++)
                {
                        if(mCurrentPlan[neighbors[i]] >= 0 && mCurrentPlan[neighbors[i]] < mCurrentPlan[next_index])
                                next_index = neighbors[i];
                }
                
                if(index == next_index) break;
                index = next_index;
        }
        
        plan_msg.cells.resize(points.size());
        for(unsigned int i = 0; i < points.size(); i++)
        {
                plan_msg.cells[i].x = points[i].first;
                plan_msg.cells[i].y = points[i].second;
                plan_msg.cells[i].z = 0.0;
        }
        mPlanPublisher.publish(plan_msg);
}

bool RobotNavigator::correctGoalPose()
{
        // Reset the plan
        int mapSize = mCurrentMap.getSize();
        for(int i = 0; i < mapSize; i++)
        {
                mCurrentPlan[i] = -1;
        }
        
        // Initialize the queue with the goal point
        Queue queue;
        Entry goal(0.0, mGoalPoint);
        queue.insert(goal);
        mCurrentPlan[mGoalPoint] = 0;
        
        Queue::iterator next;
        double linear = mCurrentMap.getResolution();
        
        // Do full search with Dijkstra-Algorithm
        while(!queue.empty())
        {
                // Get the nearest cell from the queue
                next = queue.begin();
                double distance = next->first;
                unsigned int index = next->second;
                queue.erase(next);
                
                if(mCurrentPlan[index] >= 0 && mCurrentPlan[index] < distance) continue;
                
                // Add all adjacent cells
                std::vector<unsigned int> neighbors = mCurrentMap.getNeighbors(index);
                for(unsigned int i = 0; i < neighbors.size(); i++)
                {
                        if(mCurrentMap.isFree(neighbors[i]))
                        {
                                mGoalPoint = neighbors[i];
                                return true;
                        }else
                        {
                                double newDistance = distance + linear;
                                if(mCurrentPlan[neighbors[i]] == -1)
                                {
                                        queue.insert(Entry(newDistance, neighbors[i]));
                                        mCurrentPlan[neighbors[i]] = newDistance;
                                }
                        }
                }
        }
        return false;
}

void RobotNavigator::stop()
{
        nav2d_operator::cmd stopMsg;
        stopMsg.Turn = 0;
        stopMsg.Velocity = 0;
        mCommandPublisher.publish(stopMsg);
        mStatus = NAV_ST_IDLE;
        mIsPaused = false;
        mIsStopped = false;
}

bool RobotNavigator::generateCommand()
{
        // Do nothing when paused
        if(mIsPaused)
        {
                ROS_INFO_THROTTLE(1.0, "Navigator is paused and will not move now.");
                return true;
        }
        
        if(mStatus != NAV_ST_NAVIGATING && mStatus != NAV_ST_EXPLORING)
        {
                ROS_WARN_THROTTLE(1.0, "Navigator has status %d when generateCommand() was called!", mStatus);
                return false;
        }
        
        // Generate direction command from plan
        unsigned int current_x = 0, current_y = 0;
        if(!mCurrentMap.getCoordinates(current_x, current_y, mStartPoint)) // || !mCurrentMap.isFree(mStartPoint))
        {
                ROS_ERROR("Plan execution failed, robot not in map!");
                return false;
        }

        unsigned int target = mStartPoint;
        int steps = mCommandTargetDistance / mCurrentMap.getResolution();
        for(int i = 0; i < steps; i++)
        {
                unsigned int bestPoint = target;        
                std::vector<unsigned int> neighbors = mCurrentMap.getFreeNeighbors(target);
                for(unsigned int i = 0; i < neighbors.size(); i++)
                {
                        if(mCurrentPlan[neighbors[i]] >= (unsigned int)0 && mCurrentPlan[neighbors[i]] < mCurrentPlan[bestPoint])
                                bestPoint = neighbors[i];
                }       
                target = bestPoint;
        }
        
        // Head towards (x,y)
        unsigned int x = 0, y = 0;
        if(!mCurrentMap.getCoordinates(x, y, target))
        {
                ROS_ERROR("Plan execution failed, target pose not in map!");
                return false;
        }
        double map_angle = atan2((double)y - current_y, (double)x - current_x);
        
        double angle = map_angle - mCurrentDirection;
        if(angle < -PI) angle += 2*PI;
        if(angle > PI) angle -= 2*PI;
        
        // Create the command message
        nav2d_operator::cmd msg;
        msg.Turn = -2.0 * angle / PI;
        if(msg.Turn < -1) msg.Turn = -1;
        if(msg.Turn >  1) msg.Turn = 1;
        
        if(mCurrentPlan[mStartPoint] > mNavigationHomingDistance || mStatus == NAV_ST_EXPLORING)
                msg.Mode = 0;
        else
                msg.Mode = 1;
                
        if(mCurrentPlan[mStartPoint] > 1.0 || mCurrentPlan[mStartPoint] < 0)
        {
                msg.Velocity = 1.0;
        }else
        {
                msg.Velocity = 0.5 + (mCurrentPlan[mStartPoint] / 2.0);
        }
        mCommandPublisher.publish(msg);
        return true;
}

void RobotNavigator::receiveGetMapGoal(const nav2d_navigator::GetFirstMapGoal::ConstPtr &goal)
{
        if(mStatus != NAV_ST_IDLE)
        {
                ROS_WARN("Navigator is busy!");
                mGetMapActionServer->setAborted();
                return;
        }
        
        // Move the robot slowly ahead
        mStatus = NAV_ST_RECOVERING;
        nav2d_operator::cmd msg;
        msg.Turn = 0;
        msg.Velocity = 1.0;
        msg.Mode = 0;
        
        nav2d_navigator::GetFirstMapFeedback f;
        
        Rate loopRate(mFrequency);
        unsigned int cycles = 0;
        while(true)
        {
                if(!ok() || mGetMapActionServer->isPreemptRequested() || mIsStopped)
                {
                        ROS_INFO("GetFirstMap has been preempted externally.");
                        mGetMapActionServer->setPreempted();
                        stop();
                        return;
                }
                
                if(cycles >= 4*mFrequency) break;
                cycles++;
                
                mGetMapActionServer->publishFeedback(f);
                mCommandPublisher.publish(msg);
                spinOnce();
                loopRate.sleep();
        }
        
        if(!getMap() || !setCurrentPosition())
        {
                mGetMapActionServer->setAborted();
                stop();
                return;
        }
        
        // Do a full turn to have a initial map
        msg.Turn = 1;
        msg.Mode = 1;
        double lastDirection = mCurrentDirection;
        double turn = 0;
        while(true)
        {
                if(!ok() || mGetMapActionServer->isPreemptRequested() || mIsStopped)
                {
                        ROS_INFO("GetFirstMap has been preempted externally.");
                        mGetMapActionServer->setPreempted();
                        stop();
                        return;
                }
                
                setCurrentPosition();
                double deltaTheta = mCurrentDirection - lastDirection;
                while(deltaTheta < -PI) deltaTheta += 2*PI;
                while(deltaTheta >  PI) deltaTheta -= 2*PI;
                turn += deltaTheta;
                lastDirection = mCurrentDirection;
                if(turn > 2*PI || turn < -2*PI)
                {
                        break;
                }

                mGetMapActionServer->publishFeedback(f);
                mCommandPublisher.publish(msg);
                spinOnce();
                loopRate.sleep();
        }
        
        stop();
        mHasNewMap = false;
        
        if(getMap() && setCurrentPosition())
        {
                mGetMapActionServer->setSucceeded();
        }else
        {
                ROS_WARN("Navigator could not be initialized!");
                mGetMapActionServer->setAborted();
        }
}

void RobotNavigator::receiveLocalizeGoal(const nav2d_navigator::LocalizeGoal::ConstPtr &goal)
{
        if(mStatus != NAV_ST_IDLE)
        {
                ROS_WARN("[Localize] Action aborted, Navigator is busy!");
                mGetMapActionServer->setAborted();
                return;
        }
        
        // Move the robot slowly ahead
        mStatus = NAV_ST_RECOVERING;
        nav2d_operator::cmd msg;
        msg.Turn = 0;
        msg.Velocity = goal->velocity;
        msg.Mode = 0;
        
        nav2d_navigator::LocalizeFeedback f;
        
        mHasNewMap = false;
        Rate loopRate(1);
        while(true)
        {
                // Check if we are asked to preempt
                if(!ok() || mLocalizeActionServer->isPreemptRequested() || mIsStopped)
                {
                        ROS_INFO("[Localize] Action has been preempted externally.");
                        mLocalizeActionServer->setPreempted();
                        stop();
                        return;
                }
                
                if(mHasNewMap)
                {
                        mCommandPublisher.publish(msg);
                }else
                {
                        getMap();
                }
                
                // Check if we are localized successfully
                if(isLocalized())
                {
                        ROS_INFO("[Localize] Action succeeded.");
                        mLocalizeActionServer->setSucceeded();
                        stop();
                        return;
                }
                
                mLocalizeActionServer->publishFeedback(f);
                spinOnce();
                loopRate.sleep();
        }
}

void RobotNavigator::receiveMoveGoal(const nav2d_navigator::MoveToPosition2DGoal::ConstPtr &goal)
{
        if(mStatus != NAV_ST_IDLE)
        {
                ROS_WARN("Navigator is busy!");
                mMoveActionServer->setAborted();
                return;
        }
        
        ROS_DEBUG("Received Goal: %.2f, %.2f (in frame '%s')", goal->target_pose.x, goal->target_pose.y, goal->header.frame_id.c_str());

        // Start navigating according to the generated plan
        Rate loopRate(mFrequency);
        unsigned int cycle = 0;
        bool reached = false;
        int recheckCycles = mMinReplanningPeriod * mFrequency;
        
        double targetDistance = (goal->target_distance > 0) ? goal->target_distance : mNavigationGoalDistance;
        double targetAngle = (goal->target_angle > 0) ? goal->target_angle : mNavigationGoalAngle;
        
        while(true)
        {
                // Check if we are asked to preempt
                if(!ok() || mMoveActionServer->isPreemptRequested() || mIsStopped)
                {
                        ROS_INFO("Navigation has been preempted externally.");
                        mMoveActionServer->setPreempted();
                        stop();
                        return;
                }
                
                // Constantly replan every 3 seconds
                if(cycle == 0 || (recheckCycles && cycle % recheckCycles == 0))
                {
                        WallTime startTime = WallTime::now();
                        mStatus = NAV_ST_NAVIGATING;
                        
                        // Create the plan for navigation
                        mHasNewMap = false;
                        if(!preparePlan())
                        {
                                ROS_ERROR("Prepare failed!");
                                mMoveActionServer->setAborted();
                                stop();
                                return;
                        }
                        
                        int mapX =  (double)(goal->target_pose.x - mCurrentMap.getOriginX()) / mCurrentMap.getResolution();
                        int mapY =  (double)(goal->target_pose.y - mCurrentMap.getOriginY()) / mCurrentMap.getResolution();
                        if(mapX < 0) mapX = 0;
                        if(mapX >= (int)mCurrentMap.getWidth()) mapX = mCurrentMap.getWidth() - 1;
                        if(mapY < 0) mapY = 0;
                        if(mapY >= (int)mCurrentMap.getHeight()) mapY = mCurrentMap.getHeight() - 1;

                        bool success = false;
                        if(mCurrentMap.getIndex(mapX, mapY, mGoalPoint))
                                success = createPlan();
                                
                        if(!success)
                        {
                                if(correctGoalPose())
                                        success = createPlan();
                        }
                        
                        if(!success)
                        {
                                ROS_ERROR("Planning failed!");
                                mMoveActionServer->setAborted();
                                stop();
                                return;
                        }
                        
                        WallTime endTime = WallTime::now();
                        WallDuration d = endTime - startTime;
                        ROS_INFO("Path planning took %.09f seconds, distance is %.2f m.", d.toSec(), mCurrentPlan[mStartPoint]);
                }
                
                // Where are we now
                mHasNewMap = false;
                if(!setCurrentPosition())
                {
                        ROS_ERROR("Navigation failed, could not get current position.");
                        mMoveActionServer->setAborted();
                        stop();
                        return;
                }
                
                // Are we already close enough?
                if(!reached && mCurrentPlan[mStartPoint] <= targetDistance && mCurrentPlan[mStartPoint] >= 0)
                {
                        ROS_INFO("Reached target, now turning to desired direction.");
                        reached = true;
                }
                
                if(reached)
                {
                        // Are we also headed correctly?
                        double deltaTheta = mCurrentDirection - goal->target_pose.theta;
                        while(deltaTheta < -PI) deltaTheta += 2*PI;
                        while(deltaTheta >  PI) deltaTheta -= 2*PI;
                        
                        double diff = (deltaTheta > 0) ? deltaTheta : -deltaTheta;
                        ROS_INFO_THROTTLE(1.0,"Heading: %.2f / Desired: %.2f / Difference: %.2f / Tolerance: %.2f", mCurrentDirection, goal->target_pose.theta, diff, targetAngle);
                        if(diff <= targetAngle)
                        {
                                ROS_INFO("Final Heading: %.2f / Desired: %.2f / Difference: %.2f / Tolerance: %.2f", mCurrentDirection, goal->target_pose.theta, diff, targetAngle);
                                break;
                        }
                        
                        nav2d_operator::cmd msg;
                        if(deltaTheta > 0)
                        {
                                msg.Turn = 1;
                                msg.Velocity = deltaTheta;
                        }else
                        {
                                msg.Turn = -1;
                                msg.Velocity = -deltaTheta;
                        }
                        if(msg.Velocity > 1) msg.Velocity = 1;
                                msg.Mode = 1;
                                
                        mCommandPublisher.publish(msg);
                }else
                {
                        generateCommand();
                }
                
                // Publish feedback via ActionServer
                if(cycle%10 == 0)
                {
                        nav2d_navigator::MoveToPosition2DFeedback fb;
                        fb.distance = mCurrentPlan[mStartPoint];
                        mMoveActionServer->publishFeedback(fb);
                }

                // Sleep remaining time
                cycle++;
                spinOnce();
                loopRate.sleep();
                if(loopRate.cycleTime() > ros::Duration(1.0 / mFrequency))
                        ROS_WARN("Missed desired rate of %.2fHz! Loop actually took %.4f seconds!",mFrequency, loopRate.cycleTime().toSec());
        }
        
        // Set ActionServer suceeded
        ROS_INFO("Goal reached.");
        nav2d_navigator::MoveToPosition2DResult r;
        r.final_pose.x = mCurrentPositionX;
        r.final_pose.y = mCurrentPositionY;
        r.final_pose.theta = mCurrentDirection;
        r.final_distance = mCurrentPlan[mStartPoint];
        mMoveActionServer->setSucceeded(r);
        stop();

}

void RobotNavigator::receiveExploreGoal(const nav2d_navigator::ExploreGoal::ConstPtr &goal)
{
        if(mStatus != NAV_ST_IDLE)
        {
                ROS_WARN("Navigator is busy!");
                mExploreActionServer->setAborted();
                return;
        }
        
        mStatus = NAV_ST_EXPLORING;
        unsigned int cycle = 0;
        unsigned int lastCheck = 0;
        unsigned int recheckCycles = mMinReplanningPeriod * mFrequency;
        unsigned int recheckThrottle = mMaxReplanningPeriod * mFrequency;
        
        // Move to exploration target
        Rate loopRate(mFrequency);
        while(true)
        {
                // Check if we are asked to preempt
                if(!ok() || mExploreActionServer->isPreemptRequested() || mIsStopped)
                {
                        ROS_INFO("Exploration has been preempted externally.");
                        mExploreActionServer->setPreempted();
                        stop();
                        return;
                }
                
                // Where are we now
                mHasNewMap = false;
                if(!setCurrentPosition())
                {
                        ROS_ERROR("Exploration failed, could not get current position.");
                        mExploreActionServer->setAborted();
                        stop();
                        return;
                }
                
                // Regularly recheck for exploration target
                bool reCheck = lastCheck == 0 || (recheckCycles && (cycle - lastCheck > recheckCycles));
                bool planOk = mCurrentPlan && mCurrentPlan[mStartPoint] >= 0;
                bool nearGoal = planOk && ((cycle - lastCheck) > recheckThrottle && mCurrentPlan[mStartPoint] <= mExplorationGoalDistance);
                
                if(reCheck || nearGoal)
                {
                        WallTime startTime = WallTime::now();
                        lastCheck = cycle;

                        bool success = false;
                        if(preparePlan())
                        {
                                int result = mExplorationPlanner->findExplorationTarget(&mCurrentMap, mStartPoint, mGoalPoint);
                                switch(result)
                                {
                                case EXPL_TARGET_SET:
                                        success = createPlan();
                                        mStatus = NAV_ST_EXPLORING;
                                        break;
                                case EXPL_FINISHED:
                                        {
                                                nav2d_navigator::ExploreResult r;
                                                r.final_pose.x = mCurrentPositionX;
                                                r.final_pose.y = mCurrentPositionY;
                                                r.final_pose.theta = mCurrentDirection;
                                                mExploreActionServer->setSucceeded(r);
                                        }
                                        stop();
                                        ROS_INFO("Exploration has finished.");
                                        return;
                                case EXPL_WAITING:
                                        mStatus = NAV_ST_WAITING;
                                        {
                                                nav2d_operator::cmd stopMsg;
                                                stopMsg.Turn = 0;
                                                stopMsg.Velocity = 0;
                                                mCommandPublisher.publish(stopMsg);
                                        }
                                        ROS_INFO("Exploration is waiting.");
                                        break;
                                case EXPL_FAILED:
                                        break;
                                default:
                                        ROS_ERROR("Exploration planner returned invalid status code: %d!", result);
                                }
                        }
                        
                        if(mStatus == NAV_ST_EXPLORING)
                        {
                                if(success)
                                {
                                        WallTime endTime = WallTime::now();
                                        WallDuration d = endTime - startTime;
                                        ROS_DEBUG("Exploration planning took %.09f seconds, distance is %.2f m.", d.toSec(), mCurrentPlan[mStartPoint]);
                                }else
                                {
                                        mExploreActionServer->setAborted();
                                        stop();
                                        ROS_WARN("Exploration has failed!");
                                        return;
                                }
                        }
                }
                
                if(mStatus == NAV_ST_EXPLORING)
                {
                        // Publish feedback via ActionServer
                        if(cycle%10 == 0)
                        {
                                nav2d_navigator::ExploreFeedback fb;
                                fb.distance = mCurrentPlan[mStartPoint];
                                fb.robot_pose.x = mCurrentPositionX;
                                fb.robot_pose.y = mCurrentPositionY;
                                fb.robot_pose.theta = mCurrentDirection;
                                mExploreActionServer->publishFeedback(fb);
                        }

                        // Create a new command and send it to Operator
                        generateCommand();
                }
                
                // Sleep remaining time
                cycle++;
                spinOnce();
                loopRate.sleep();
                if(loopRate.cycleTime() > ros::Duration(1.0 / mFrequency))
                        ROS_WARN("Missed desired rate of %.2fHz! Loop actually took %.4f seconds!",mFrequency, loopRate.cycleTime().toSec());
        }
}

bool RobotNavigator::isLocalized()
{
        return mTfListener.waitForTransform(mMapFrame, mRobotFrame, Time::now(), Duration(0.1));
}

bool RobotNavigator::setCurrentPosition()
{
        StampedTransform transform;
        try
        {
                mTfListener.lookupTransform(mMapFrame, mRobotFrame, Time(0), transform);
        }catch(TransformException ex)
        {
                ROS_ERROR("Could not get robot position: %s", ex.what());
                return false;
        }
        double world_x = transform.getOrigin().x();
        double world_y = transform.getOrigin().y();
        double world_theta = getYaw(transform.getRotation());

        unsigned int current_x = (world_x - mCurrentMap.getOriginX()) / mCurrentMap.getResolution();
        unsigned int current_y = (world_y - mCurrentMap.getOriginY()) / mCurrentMap.getResolution();
        unsigned int i;
        
        if(!mCurrentMap.getIndex(current_x, current_y, i))
        {
                if(mHasNewMap || !getMap() || !mCurrentMap.getIndex(current_x, current_y, i))
                {
                        ROS_ERROR("Is the robot out of the map?");
                        return false;
                }
        }
        mStartPoint = i;
        mCurrentDirection = world_theta;
        mCurrentPositionX = world_x;
        mCurrentPositionY = world_y;
        return true;
}