publish array velocities in a topic?

asked 2015-04-29 05:35:15 -0500

Alvaro Salcedo
149 ●38 ●44 ●49

Hi Ros users! I have just done a .cpp wich publish velocities in a opic (p3dx/cmd_vel) Here it is:

int main(int argc, char **argv)
{
  ros::init(argc, argv, "lanzando_vel");
  ros::NodeHandle n;
  ros::Publisher vel_pub_ = n.advertise<geometry_msgs::Twist>("p3dx/cmd_vel", 1);

  while (ros::ok())
  {
  geometry_msgs::Twist cmd;
  cmd.linear.x = 0;
  cmd.linear.y = 0;
  cmd.linear.z = 0;

  cmd.angular.x = 0;
  cmd.angular.y = 0;
  cmd.angular.z = 0;
    vel_pub_.publish(cmd);
  }
    return 0;
}

I would like to publish an array velocities, for example:

at 1seg ==> cmd.linear.x=1 at 3 seg==> cmd.linear.x=4 . . .

how can I do that?

Thank you so much!

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2

answered 2015-04-29 09:05:05 -0500

marguedas

3606 ●17 ●109 ●57

Hi, You can create your own message Velocity array. Then you fill your array with twist messages. Finally you publish it.
You have an example in python in this answer.

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answered 2015-04-30 23:00:53 -0500

130s

10937 ●203 ●339 ●330 http://www.linkedin.co...

Although I haven't done it personally, I would try using TwistStamped, put its instances into an array (as @marguedas does in the link provided), particularly when you want to specify the timing where the Twist gets executed. You can specify it in its header.stamp.

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answered 2015-07-13 06:27:01 -0500

Alvaro Salcedo
149 ●38 ●44 ●49

Hi. First of all thanks for your responses Did you do this @130s ?

I am trying it. I have done this:

  geometry_msgs::Twist cmd;
  geometry_msgs::TwistStamped tiempo;
  cmd.linear.x = 1; 
  cmd.linear.y = 0;
  cmd.linear.z = 0;

  tiempo.header.stamp=5;
  cmd.angular.x = 0;
  cmd.angular.y = 0;
  cmd.angular.z = 4;
  vel_pub_.publish(cmd);

But when it is compiled i can see these errors on terminal

>     /home/alcor/catkin_ws/src/lanzar_velocidades/src/arrayvel.cpp:52:3:
> error: ‘geometry’ has not been
> declared geometry::TwistStamped
> tiempo; ^
> /home/alcor/catkin_ws/src/lanzar_velocidades/src/arrayvel.cpp:52:26:
> error: expected ‘;’ before ‘tiempo’
>     geometry::TwistStamped tiempo; ^ /home/alcor/catkin_ws/src/lanzar_velocidades/src/arrayvel.cpp:57:3:
> error: ‘tiempo’ was not declared in
> this scope tiempo.header.stamp=5;
>     ^ make[2]: * [lanzar_velocidades/CMakeFiles/arrayvel_node.dir/src/arrayvel.cpp.o]
> Error 1 make[1]: *
> [lanzar_velocidades/CMakeFiles/arrayvel_node.dir/all]
> Error 2

Any ideas?

Thanks!

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