.

src/tutorial_pkg/CMakeLists.txt

@@ -31,3 +31,9 @@ add_executable(img_control_node src/img_control.cpp)
 target_link_libraries(img_control_node
         ${catkin_LIBRARIES}
 )
+
+add_executable(follow_img_node src/follow_img.cpp)
+target_link_libraries(follow_img_node
+        ${catkin_LIBRARIES}
+        ${OpenCV_LIBRARIES}
+)

src/tutorial_pkg/src/CMakeLists.txt

@@ -30,3 +30,9 @@ add_executable(img_control_node src/img_control.cpp)
 target_link_libraries(img_control_node
         ${catkin_LIBRARIES}
 )
+
+add_executable(follow_img_node src/follow_img.cpp)
+target_link_libraries(follow_img_node
+        ${catkin_LIBRARIES}
+        ${OpenCV_LIBRARIES}
+)

src/tutorial_pkg/src/follow_img.cpp

@@ -0,0 +1,106 @@
+#include <ros/ros.h>
+#include <std_msgs/Float32MultiArray.h>
+#include <geometry_msgs/Twist.h>
+#include <opencv2/opencv.hpp>
+#include <sensor_msgs/Range.h>
+
+#define OBJECT_TO_FOLLOW 3
+#define CAMERA_WIDTH     640 // left 0, right 640
+
+#define MIN_ANG_VEL     0.15f
+#define MAX_ANG_VEL     0.5f
+#define ANGULAR_GAIN    2e-3 // 0.002 rad/s for each pixel of difference
+
+#define DESIRED_DIST    0.6f
+#define MIN_LIN_VEL     0.05f
+#define MAX_LIN_VEL     0.4f
+#define LINEAR_GAIN     0.4f // 0.4 m/s for each meter of difference
+
+
+ros::Publisher vel_pub;
+geometry_msgs::Twist vel_msg;
+
+float distFL = 0;
+float distFR = 0;
+
+void distFL_callback(const sensor_msgs::Range &range)
+{
+    distFL = range.range;
+}
+
+void distFR_callback(const sensor_msgs::Range &range)
+{
+    distFR = range.range;
+}
+
+void objectCallback(const std_msgs::Float32MultiArrayPtr &object)
+{
+    int obj_x_pos;
+    float ang_vel;
+    float avg_dist;
+    float x_vel;
+
+    // Reset linear and angular speed value
+    vel_msg.linear.x = 0;
+    vel_msg.angular.z = 0;
+
+    if (object->data.size() > 0){
+        int id = object->data[0];
+        float objectWidth = object->data[1];
+        float objectHeight = object->data[2];
+
+        cv::Mat cvHomography(3, 3, CV_32F);
+        std::vector<cv::Point2f> inPts, outPts;
+        switch (id)
+        {
+            case OBJECT_TO_FOLLOW:
+
+                // Matrix completion
+                for(int i=0; i<9; i++){
+                    cvHomography.at<float>(i%3, i/3) = object->data[i+3];
+                }
+
+                // Save corners to vector
+                inPts.push_back(cv::Point2f(0, 0));
+                inPts.push_back(cv::Point2f(objectWidth, 0));
+                inPts.push_back(cv::Point2f(0, objectHeight));
+                inPts.push_back(cv::Point2f(objectWidth, objectHeight));
+                cv::perspectiveTransform(inPts, outPts, cvHomography);
+
+                obj_x_pos = (outPts.at(0).x + outPts.at(1).x + outPts.at(2).x + outPts.at(3).x) / 4;
+                ang_vel = ANGULAR_GAIN*(CAMERA_WIDTH/2 - obj_x_pos);
+
+                avg_dist = (distFL + distFR) / 2.0;
+                x_vel = LINEAR_GAIN*(avg_dist - DESIRED_DIST);
+
+                // Set angular speed
+                if(ang_vel <= -MIN_ANG_VEL || ang_vel >= MIN_ANG_VEL){
+                    vel_msg.angular.z = std::max(-MAX_ANG_VEL, std::min(ang_vel, MAX_ANG_VEL));
+                }
+                    // Set linear speed
+                else if(x_vel <= -MIN_LIN_VEL || x_vel >= MIN_LIN_VEL){
+                    vel_msg.linear.x = std::max(-MAX_LIN_VEL, std::min(x_vel, MAX_LIN_VEL));
+                }
+                ROS_INFO("id: %d\t ang_vel: %f\t x_vel: %f", id, vel_msg.angular.z, x_vel);
+                break;
+        }
+    }
+
+    vel_pub.publish(vel_msg);
+}
+
+int main(int argc, char **argv)
+{
+    ros::init(argc, argv, "follow_obj");
+    ros::NodeHandle n("~");
+    ros::Subscriber sub = n.subscribe("/objects", 1, objectCallback);
+    ros::Subscriber distL_sub = n.subscribe("/range/fl", 1, distFL_callback);
+    ros::Subscriber distR_sub = n.subscribe("/range/fr", 1, distFR_callback);
+    ros::Rate loop_rate(30);
+    vel_pub = n.advertise<geometry_msgs::Twist>("/cmd_vel", 1);
+    while (ros::ok())
+    {
+        ros::spinOnce();
+        loop_rate.sleep();
+    }
+}