Answer by Humpelstilzchen for I want to move my turtlebot 2 a fixed set of distances such as 1m forward, 1m right and etc accurately using odometry. This is the C++ code i have currently. However, it does not seem to be using the odometry. How should I change the code to enable myself to move the robot accurately ?Below is the code that I currently have. What it does is enable me to move the turtlebot as well as received odometry data on the console. class TurtleMoveAvoid; class TurtleMoveAvoid { public: TurtleMoveAvoid() { _pub = _n.advertise<geometry_msgs::Twist>("/mobile_base/commands/velocity", 1); _sub = _n.subscribe("/odom", 1, &TurtleMoveAvoid::odomCallback, this); _left = true; _right = true; } void publish() { if (_left && _right) { forward(); } else if (_right) { turnRight(); } else if (_left) { turnLeft(); } else { reverse(); } } void forward() { geometry_msgs::Twist vel; vel.linear.x = 0.2; vel.angular.z = 0.0; _pub.publish(vel); } void reverse() { geometry_msgs::Twist vel; vel.linear.x = -0.2; vel.angular.z = 0.0; _pub.publish(vel); } void turnLeft() { geometry_msgs::Twist vel; vel.linear.x = 0.0; vel.angular.z = 0.7; _pub.publish(vel); } void turnRight() { geometry_msgs::Twist vel; vel.linear.x = 0.0; vel.angular.z = -0.7; _pub.publish(vel); } void odomCallback(const nav_msgs::Odometry::ConstPtr& odom) { ROS_INFO("I received odom: [%f,%f,%f]", odom->twist.twist.linear.x, odom->pose.pose.position.y,odom->pose.pose.orientation.z); double xpos = odom->twist.twist.linear.x; if(xpos < 0.2) //assuming 0.2 is the end { _right = true; _left = true; } else { _right = false; _left = false; } publish(); } private: ros::NodeHandle _n; ros::Publisher _pub; ros::Subscriber _sub; bool _right, _left; };// End of class TurtleMoveAvoid int main(int argc, char **argv) { ros::init(argc, argv, "turtle_move_odom"); TurtleMoveAvoid turtle; ros::Rate loop_rate(10); while (ros::ok()) { ros::spinOnce(); //get new callback, adjust publish then publish again. loop_rate.sleep(); } return 0; }

For starters, the questioner is trying to compare the variable xpos with a velocity (twist). When moving a distance forward someone probably wants to use the navigation stack instead. Novinho you should open a new question.