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Move a certain distance (geometry_msg:Twist)

asked 2015-03-16 04:33:04 -0500

dylankc gravatar image

Currently this is the code that I have, and I am able to get the robot moving by editing the linear x or angular z values (speed).

#include <ros/ros.h>
#include <geometry_msgs/Twist.h>

int main(int argc, char **argv)
{
ros::init(argc, argv, "move_pub");
ros::NodeHandle n;
ros::Publisher movement_pub = n.advertise<geometry_msgs::Twist>("mobile_base/commands/velocity",1); 
ros::Rate rate(10);

while (ros::ok()) 
{
    geometry_msgs::Twist move;
    //velocity controls
    move.linear.x = -0.1; //speed value m/s
    move.angular.z = 0;
    movement_pub.publish(move);

    ros::spinOnce();
    rate.sleep();
}
return 0;
}

Is there a time control in ROS? Whereby I can do something like while time <= 5s, publish linear x velocity of 0.2m/s. Thus, covering 1 meter. I am new to ROS and it is my first week into it. Im working on the TurtleBot 2.

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3

Also see robot pose slightly off when publishing to /cmd_vel for some discussion on the feasibility of what you are trying to achieve.

gvdhoorn gravatar imagegvdhoorn ( 2015-03-16 06:44:31 -0500 )edit

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answered 2015-03-16 05:40:25 -0500

dornhege gravatar image

updated 2015-03-16 05:40:40 -0500

There is ros::Time and ros::Duration, which can be used in an intuitive way. ros::Time::now() gives you the current time. You probably want something like:

ros::Time start = ros::Time::now()
while(ros::Time::now() - start < ros::Duration(5.0))
    ...
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Thank you dornhege for teaching me about the ros::Time & ros::Duration function. However, i've taken a look at "http://answers.ros.org/question/204973/robot-pose-slightly-off-when-publishing-to-cmd_vel/" and realized that my method is prone to inaccuracy!

I'll try publishing to /odom.

dylankc gravatar imagedylankc ( 2015-03-16 20:20:06 -0500 )edit

I appreciate your help very much. Thank you

dylankc gravatar imagedylankc ( 2015-03-16 20:20:33 -0500 )edit

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Asked: 2015-03-16 04:33:04 -0500

Seen: 1,440 times

Last updated: Mar 16 '15