I am trying to program for a TurtleBot, but there is a significant lack of tutorials for the robot and I have been unable to write my own C++ which works. I am trying to use a tutorial from another robot just to make the robot move when a key is pressed.
The source tutorial is found here: , which I only modified the publish topic to "/cmd_vel"
#include <iostream>
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
class RobotDriver
{
private:
//! The node handle we'll be using
ros::NodeHandle nh_;
//! We will be publishing to the "/base_controller/command" topic to issue commands
ros::Publisher cmd_vel_pub_;
public:
//! ROS node initialization
RobotDriver(ros::NodeHandle &nh)
{
nh_ = nh;
//set up the publisher for the cmd_vel topic
cmd_vel_pub_ = nh_.advertise<geometry_msgs::Twist>("/cmd_vel", 1);
}
//! Loop forever while sending drive commands based on keyboard input
bool driveKeyboard()
{
std::cout << "Type a command and then press enter. "
"Use '+' to move forward, 'l' to turn left, "
"'r' to turn right, '.' to exit.\n";
//we will be sending commands of type "twist"
geometry_msgs::Twist base_cmd;
char cmd[50];
while(nh_.ok()){
std::cin.getline(cmd, 50);
if(cmd[0]!='+' && cmd[0]!='l' && cmd[0]!='r' && cmd[0]!='.')
{
std::cout << "unknown command:" << cmd << "\n";
continue;
}
base_cmd.linear.x = base_cmd.linear.y = base_cmd.angular.z = 0;
//move forward
if(cmd[0]=='+'){
base_cmd.linear.x = 0.25;
}
//turn left (yaw) and drive forward at the same time
else if(cmd[0]=='l'){
base_cmd.angular.z = 0.75;
base_cmd.linear.x = 0.25;
}
//turn right (yaw) and drive forward at the same time
else if(cmd[0]=='r'){
base_cmd.angular.z = -0.75;
base_cmd.linear.x = 0.25;
}
//quit
else if(cmd[0]=='.'){
break;
}
//publish the assembled command
cmd_vel_pub_.publish(base_cmd);
}
return true;
}
};
int main(int argc, char** argv)
{
//init the ROS node
ros::init(argc, argv, "robot_driver");
ros::NodeHandle nh;
RobotDriver driver(nh);
driver.driveKeyboard();
}
The code compiles and runs correctly, but the turtlebot does not move when commands are issued. Any ideas why?
Additional Info:
When I'm on the laptop provided with my Turtlebot messages appear to not be being sent (or are not being delivered). In separate terminals, I have:
turtlebot@turtlebot-0516:~$ sudo service turtlebot start
[sudo] password for turtlebot:
turtlebot start/running, process 1470
turtlebot@turtlebot-0516:~$ rostopic echo /cmd_vel
And
turtlebot@turtlebot-0516:~$ rostopic pub /cmd_vel geometry_msgs/Twist '[1.0, 0.0, 0.0]' '[0.0, 0.0, 0.0]'
publishing and latching message. Press ctrl-C to terminate
With info:
turtlebot@turtlebot-0516:~$ rostopic info /cmd_vel
Type: geometry_msgs/Twist
Publishers:
* /rosttopic_2547_1352476947372 (http://turtlebot-0516:40275/)
Subscribers:
* /turtlebot_node (http://10.143.7.81:58649/)
* /rostopic_2278_1352476884936 (http://turtlebot-0516:39291/)
There is no output for the echo at all
Originally posted by Emordnys on ROS Answers with karma: 1 on 2012-11-05
Post score: 0
Original comments
Comment by Lorenz on 2012-11-05:
What's the output of rostopic echo /cmd_vel when you are sending commands? What's the output of rostopic info /cmd_vel. Please edit your question to add more information. Also please tag it correctly to make sure the right people get notified.
Comment by Lorenz on 2012-11-09:
Hm. Weird that rostopic pub does not work. You should receive exactly one message since rostopic pub latches the topic. Can you try rostopic pub /cmd_vel geometry_msgs/Twist '{linear: {x: 1.0}}' -r 10 to repeat the message with 10 Hz? Btw. my syntax will have the same effect as yours.
Comment by qubaish g on 2013-04-01:
if we want to move two turtle bot by rostopic pub /cmd_vel geometry_msgs/Twist what can i do ..... because by giving this command both turtle bot move in the same direction ..... i want to move one turtlebbot in one direction and other turtlebot in another direction .... thanks for the help @lorenz