RobotOperator.cpp

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#include <nav_msgs/GridCells.h>
#include <math.h>

#include <nav2d_operator/RobotOperator.h>

#define PI 3.14159265

RobotOperator::RobotOperator()
{
        // Create the local costmap
        mLocalMap = new costmap_2d::Costmap2DROS("local_map", mTfListener);
        mRasterSize = mLocalMap->getCostmap()->getResolution();
        
        // Publish / subscribe to ROS topics
        ros::NodeHandle robotNode;
        robotNode.param("robot_frame", mRobotFrame, std::string("robot"));
        robotNode.param("odometry_frame", mOdometryFrame, std::string("odometry_base"));
        mCommandSubscriber = robotNode.subscribe(COMMAND_TOPIC, 1, &RobotOperator::receiveCommand, this);
        mControlPublisher = robotNode.advertise<geometry_msgs::Twist>(CONTROL_TOPIC, 1);
        mCostPublisher = robotNode.advertise<geometry_msgs::Vector3>("costs", 1);
        
        // Get parameters from the parameter server
        ros::NodeHandle operatorNode("~/");
        operatorNode.param("publish_route", mPublishRoute, false);
        if(mPublishRoute)
        {
                ROS_INFO("Will publish desired direction on '%s' and control direction on '%s'.", ROUTE_TOPIC, PLAN_TOPIC);
                mTrajectoryPublisher = operatorNode.advertise<nav_msgs::GridCells>(ROUTE_TOPIC, 1);
                mPlanPublisher = operatorNode.advertise<nav_msgs::GridCells>(PLAN_TOPIC, 1);
        }
        operatorNode.param("max_free_space", mMaxFreeSpace, 5.0);
        operatorNode.param("safety_decay", mSafetyDecay, 0.95);
        operatorNode.param("safety_weight", mSafetyWeight, 1);
        operatorNode.param("conformance_weight", mConformanceWeight, 1);
        operatorNode.param("continue_weight", mContinueWeight, 1);
        operatorNode.param("escape_weight", mEscapeWeight, 1);
        operatorNode.param("max_velocity", mMaxVelocity, 1.0);

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

        // Initialize the lookup table for the driving directions
        ROS_INFO("Initializing LUT...");
        initTrajTable();
        ROS_INFO("...done!");
        
        // Set internal parameters
        mDesiredDirection = 0;
        mDesiredVelocity = 0;
        mCurrentDirection = 0;
        mCurrentVelocity = 0;
        mDriveMode = 0;
        mRecoverySteps = 0;
}

RobotOperator::~RobotOperator()
{
        for(int i = 0; i < LUT_RESOLUTION; i++)
        {
                delete mTrajTable[i];
        }
}

void RobotOperator::initTrajTable()
{
        for(int i = 0; i < (LUT_RESOLUTION * 4) + 2; i++)
        {
                mTrajTable[i] = NULL;
        }       
        for(int i = 1; i < LUT_RESOLUTION; i++)
        {
                double tw = -PI * i / LUT_RESOLUTION;
                double tx = cos(tw) + 1;
                double ty = -sin(tw);
                double tr = ((tx*tx)+(ty*ty))/(ty+ty);
                std::vector<geometry_msgs::Point32> points;
                double alpha = 0;
                while(alpha < PI)
                {
                        double x = tr * sin(alpha);
                        double y = tr * (1.0 - cos(alpha));
                        geometry_msgs::Point32 p;
                        p.x = x;
                        p.y = y;
                        p.z = 0;
                        points.push_back(p);
                        alpha += mRasterSize / tr;
                }
                // Add the PointCloud to the LUT
                // Circle in forward-left direction
                sensor_msgs::PointCloud* flcloud = new sensor_msgs::PointCloud();
                flcloud->header.stamp = ros::Time(0);
                flcloud->header.frame_id = mRobotFrame;
                flcloud->points.resize(points.size());
                
                // Circle in forward-right direction
                sensor_msgs::PointCloud* frcloud = new sensor_msgs::PointCloud();
                frcloud->header.stamp = ros::Time(0);
                frcloud->header.frame_id = mRobotFrame;
                frcloud->points.resize(points.size());
                
                // Circle in backward-left direction
                sensor_msgs::PointCloud* blcloud = new sensor_msgs::PointCloud();
                blcloud->header.stamp = ros::Time(0);
                blcloud->header.frame_id = mRobotFrame;
                blcloud->points.resize(points.size());
                
                // Circle in backward-right direction
                sensor_msgs::PointCloud* brcloud = new sensor_msgs::PointCloud();
                brcloud->header.stamp = ros::Time(0);
                brcloud->header.frame_id = mRobotFrame;
                brcloud->points.resize(points.size());
                
                for(unsigned int j = 0; j < points.size(); j++)
                {
                        flcloud->points[j] = points[j];
                        frcloud->points[j] = points[j];
                        blcloud->points[j] = points[j];
                        brcloud->points[j] = points[j];
                        
                        frcloud->points[j].y *= -1;
                        blcloud->points[j].x *= -1;
                        brcloud->points[j].x *= -1;
                        brcloud->points[j].y *= -1;
                }
                mTrajTable[LUT_RESOLUTION - i] = flcloud;
                mTrajTable[LUT_RESOLUTION + i] = frcloud;
                mTrajTable[(3 * LUT_RESOLUTION + 1) - i] = blcloud;
                mTrajTable[(3 * LUT_RESOLUTION + 1) + i] = brcloud;
        }
        
        // Add First and Last LUT-element
        geometry_msgs::Point32 p;
        p.x = 0;
        p.y = 0;
        p.z = 0;
        
        sensor_msgs::PointCloud* turn = new sensor_msgs::PointCloud();
        turn->header.stamp = ros::Time(0);
        turn->header.frame_id = mRobotFrame;
        turn->points.resize(1);
        turn->points[0] = p;
        
        int straight_len = 5.0 / mRasterSize;
        
        sensor_msgs::PointCloud* fscloud = new sensor_msgs::PointCloud();
        fscloud->header.stamp = ros::Time(0);
        fscloud->header.frame_id = mRobotFrame;
        fscloud->points.resize(straight_len);
        
        sensor_msgs::PointCloud* bscloud = new sensor_msgs::PointCloud();
        bscloud->header.stamp = ros::Time(0);
        bscloud->header.frame_id = mRobotFrame;
        bscloud->points.resize(straight_len);
        
        for(int i = 0; i < straight_len; i++)
        {
                fscloud->points[i] = p;
                bscloud->points[i] = p;
                bscloud->points[i].x *= -1;
                p.x += mRasterSize;
        }
        
        mTrajTable[LUT_RESOLUTION] = fscloud;
        mTrajTable[LUT_RESOLUTION*3 + 1] = bscloud;
        
        mTrajTable[0] = turn;
        mTrajTable[LUT_RESOLUTION*2] = turn;
        mTrajTable[LUT_RESOLUTION*2 + 1] = turn;
        mTrajTable[LUT_RESOLUTION*4 + 1] = turn;
        
        for(int i = 0; i < (LUT_RESOLUTION * 4) + 2; i++)
        {
                if(!mTrajTable[i])
                {
                        ROS_ERROR("Table entry %d has not been initialized!", i);
                }
        }       
}

void RobotOperator::receiveCommand(const nav2d_operator::cmd::ConstPtr& msg)
{
        if(msg->Turn < -1 || msg->Turn > 1)
        {
                // The given direction is invalid.
                // Something is going wrong, so better stop the robot:
                mDesiredDirection = 0;
                mDesiredVelocity = 0;
                mCurrentDirection = 0;
                mCurrentVelocity = 0;
                ROS_ERROR("Invalid turn direction on topic '%s'!", COMMAND_TOPIC);
                return;
        }
        mDesiredDirection = msg->Turn;
        mDesiredVelocity = msg->Velocity * mMaxVelocity;
        mDriveMode = msg->Mode;
}

void RobotOperator::executeCommand()
{
        // 1. Get a copy of the costmap to work on.
        mCostmap = mLocalMap->getCostmap();
        boost::unique_lock<costmap_2d::Costmap2D::mutex_t> lock(*(mCostmap->getMutex()));
        double bestDirection, d;
        
        // 2. Set velocity and direction depending on drive mode
        switch(mDriveMode)
        {
        case 0:
                bestDirection = findBestDirection();
                d = bestDirection - mCurrentDirection;
                if(d < -0.2) d = -0.2;
                if(d > 0.2) d = 0.2;
                mCurrentDirection += d;
                mCurrentVelocity = mDesiredVelocity;
                break;
        case 1:
                mCurrentDirection = mDesiredDirection;
                mCurrentVelocity = mDesiredVelocity;
                break;
        default:
                ROS_ERROR("Invalid drive mode!");
                mCurrentVelocity = 0.0;
        }
        
        // Create some Debug-Info
        evaluateAction(mCurrentDirection, mCurrentVelocity, true);
        
        sensor_msgs::PointCloud* originalCloud = getPointCloud(mCurrentDirection, mDesiredVelocity);
        sensor_msgs::PointCloud transformedCloud;

        try
        {
                mTfListener.transformPointCloud(mOdometryFrame,*originalCloud,transformedCloud);
        }
        catch(tf::TransformException ex)
        {
                ROS_ERROR("%s", ex.what());
                return;
        }
        
        // Determine maximum linear velocity
        int freeCells = calculateFreeSpace(&transformedCloud);
        double freeSpace = mRasterSize * freeCells;

        double safeVelocity = (freeSpace / mMaxFreeSpace) + 0.05;
        if(freeCells == transformedCloud.points.size() && safeVelocity < 0.5)
                safeVelocity = 0.5;
                
        if(freeSpace < 0.3 && freeCells < transformedCloud.points.size())
                safeVelocity = 0;

        if(safeVelocity > mMaxVelocity)
                safeVelocity = mMaxVelocity;

        // Check whether the robot is stuck
        if(mRecoverySteps > 0) mRecoverySteps--;
        if(safeVelocity < 0.1)
        {
                if(mDriveMode == 0)
                {
                        mRecoverySteps = 30; // Recover for 3 seconds
                        ROS_WARN_THROTTLE(1, "Robot is stuck! Trying to recover...");
                }else
                {
                        mCurrentVelocity = 0;
                        ROS_WARN_THROTTLE(1, "Robot cannot move further in this direction!");
                }
        }

        // Publish route via ROS (mainly for debugging)
        if(mPublishRoute)
        {
                nav_msgs::GridCells route_msg;
                route_msg.header.frame_id = mOdometryFrame;
                route_msg.header.stamp = ros::Time::now();
        
                route_msg.cell_width = mCostmap->getResolution();
                route_msg.cell_height = mCostmap->getResolution();
        
                route_msg.cells.resize(freeCells);
                for(int i = 0; i < freeCells; i++)
                {
                        route_msg.cells[i].x = transformedCloud.points[i].x;
                        route_msg.cells[i].y = transformedCloud.points[i].y;
                        route_msg.cells[i].z = transformedCloud.points[i].z;
                }
                mTrajectoryPublisher.publish(route_msg);
        
                // Publish plan via ROS (mainly for debugging)
                sensor_msgs::PointCloud* originalPlanCloud = getPointCloud(mDesiredDirection, mDesiredVelocity);
                sensor_msgs::PointCloud transformedPlanCloud;

                try
                {
                        mTfListener.transformPointCloud(mOdometryFrame,*originalPlanCloud,transformedPlanCloud);
                }
                catch(tf::TransformException ex)
                {
                        ROS_ERROR("%s", ex.what());
                        return;
                }
                nav_msgs::GridCells plan_msg;
                plan_msg.header = route_msg.header;
        
                plan_msg.cell_width = mCostmap->getResolution();
                plan_msg.cell_height = mCostmap->getResolution();
        
                int freeSpacePlan = calculateFreeSpace(&transformedPlanCloud);
                plan_msg.cells.resize(freeSpacePlan);
                for(int i = 0; i < freeSpacePlan; i++)
                {
                        plan_msg.cells[i].x = transformedPlanCloud.points[i].x;
                        plan_msg.cells[i].y = transformedPlanCloud.points[i].y;
                        plan_msg.cells[i].z = transformedPlanCloud.points[i].z;
                }
                mPlanPublisher.publish(plan_msg);
        }
        
        // Publish result via Twist-Message
        geometry_msgs::Twist controlMsg;
        double velocity = mCurrentVelocity;
        if(mCurrentDirection == 0)
        {
                if(velocity > safeVelocity)
                {
                        ROS_DEBUG("Desired velocity of %.2f is limited to %.2f", velocity, safeVelocity);
                        velocity = safeVelocity;
                }else if(velocity < -safeVelocity)
                {
                        ROS_DEBUG("Desired velocity of %.2f is limited to %.2f", velocity, -safeVelocity);
                        velocity = -safeVelocity;
                }
                controlMsg.linear.x = velocity;
                controlMsg.angular.z = 0;
        }else if(mCurrentDirection == -1 || mCurrentDirection == 1)
        {
                controlMsg.linear.x = 0;
                controlMsg.angular.z = -1.0 * mCurrentDirection * velocity;
        }else
        {
                double x = sin(mCurrentDirection * PI);
                double y = (cos(mCurrentDirection * PI) + 1);
                double r = ((x*x) + (y*y)) / (2*x);
                double abs_r = (r > 0) ? r : -r;
                velocity /= (1 + (1.0/abs_r));
                if(velocity > safeVelocity)
                {
                        ROS_DEBUG("Desired velocity of %.2f is limited to %.2f", velocity, safeVelocity);
                        velocity = safeVelocity;
                }else if(velocity < -safeVelocity)
                {
                        ROS_DEBUG("Desired velocity of %.2f is limited to %.2f", velocity, -safeVelocity);
                        velocity = -safeVelocity;
                }
                
                controlMsg.linear.x = velocity;
                controlMsg.angular.z = -1.0 / r * controlMsg.linear.x;
        }
        mControlPublisher.publish(controlMsg);
}

int RobotOperator::calculateFreeSpace(sensor_msgs::PointCloud* cloud)
{       
        unsigned int mx, my;
        int length = cloud->points.size();
        int freeSpace = 0;
        for(int i = 0; i < length; i++)
        {
                if(mCostmap->worldToMap(cloud->points[i].x, cloud->points[i].y, mx, my))
                {
                        if(mCostmap->getCost(mx,my) < costmap_2d::INSCRIBED_INFLATED_OBSTACLE)
                        {
                                freeSpace++;
                        }else
                        {
                                break;
                        }
                }else
                {
                        break;
                }
        }
        return freeSpace;
}

double RobotOperator::evaluateAction(double direction, double velocity, bool debug)
{
        sensor_msgs::PointCloud* originalCloud = getPointCloud(direction, velocity);
        sensor_msgs::PointCloud transformedCloud;
        try
        {
                mTfListener.transformPointCloud(mOdometryFrame, *originalCloud,transformedCloud);
        }
        catch(tf::TransformException ex)
        {
                ROS_ERROR("%s", ex.what());
                return 1;
        }
        
        double valueSafety = 0.0;      // How safe is it to move in that direction?
        double valueEscape = 0.0;      // How much does the safety improve?
        double valueConformance = 0.0; // How conform is it with the desired direction?
        double valueContinue = 0.0;    // How conform is it with the previous command?
        
        double decay = 1.0;
        double safe_max = 0.0;
        double cost_max = 0.0;
        double cost_start = 1.0;
        
        // Calculate safety and escape value
        int length = transformedCloud.points.size();
        for(int i = 0; i < length; i++)
        {
                unsigned int mx, my;
                double cell_cost;
                if(mCostmap->worldToMap(transformedCloud.points[i].x, transformedCloud.points[i].y, mx, my))
                {
                        cell_cost = (double)mCostmap->getCost(mx,my) / costmap_2d::INSCRIBED_INFLATED_OBSTACLE;
                        if(cell_cost >= 1.0)
                        {
                                // Trajectory hit an obstacle
                                break;
                        }
                }
                if(i == 0)
                        cost_start = cell_cost;
                double cost = cell_cost * decay;
                double safe = (cost_start - cell_cost) * decay * 2.0;
                
                if(cost > cost_max) cost_max = cost;
                if(safe > safe_max) safe_max = safe;
                
                decay *= mSafetyDecay;
        }
        
        double action_value = 0.0;
        double normFactor = 0.0;
        
        // Add safety value
        valueSafety = 1.0 - cost_max;
        action_value += valueSafety * mSafetyWeight;
        normFactor += mSafetyWeight;
        
        // Add escape value
        valueEscape = safe_max;
        action_value += valueEscape * mEscapeWeight;
        normFactor += mEscapeWeight;

        if(mRecoverySteps == 0)
        {
                // Calculate continuety value
                valueContinue = (mCurrentDirection - direction) * 0.5;
                valueContinue = 1.0 - (valueContinue * valueContinue);
                
                // Calculate conformance value
                double corr = (mDesiredDirection - direction) * PI;
                valueConformance = 0.5 * cos(corr) + 0.5;
                
                // Add both to action value
                action_value += valueConformance * mConformanceWeight;
                action_value += valueContinue * mContinueWeight;
                normFactor += mConformanceWeight + mContinueWeight;
        }
        
        action_value /= normFactor;
        
        if(debug)
        {
                geometry_msgs::Vector3 cost_msg;
                cost_msg.x = valueSafety;
                cost_msg.y = valueEscape;
                cost_msg.z = valueConformance;
                mCostPublisher.publish(cost_msg); 
        }
        
        return action_value;
}

double diff(double v1, double v2)
{
        if(v1 > v2)
                return v1 - v2;
        else
                return v2 - v1;
}

double RobotOperator::findBestDirection()
{
        double best_dir = -1.0;
        double best_value = 0.0;
        double step = 0.01;
        double dir = -1.0;
        
        while(dir <= 1.0)
        {
                double value = evaluateAction(dir, mDesiredVelocity);
                if(value > best_value)
                {
                        best_dir = dir;
                        best_value = value;
                }
                dir += step;
        }
        return best_dir;
}

sensor_msgs::PointCloud* RobotOperator::getPointCloud(double direction, double velocity)
{
        if(direction < -1) direction = -1;
        if(direction > 1) direction = 1;
        int offset = (velocity >= 0) ? LUT_RESOLUTION : 3*LUT_RESOLUTION + 1;
        int table_index = (direction * LUT_RESOLUTION) + offset;
        return mTrajTable[table_index];
}