Simple problem with TwistStamped msg

edit

hi Ros users:

I am trying to do an array of velocities. This is my code:

  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!