Move With PID

  
void trackCallback (const geometry_msgs::Point::ConstPtr & track_msg)
  {
    ros::NodeHandle nh;
    geometry_msgs::Twist move_msg;
    geometry_msgs::Point plot_msg;
    ros::Time time = ros::Time::now();
    double effort = 0;

    // Set the turn - turn on the z axis
    move_msg.linear.x = 0;
    move_msg.linear.y = 0;
    move_msg.linear.z = 0;
    move_msg.angular.x = 0;
    move_msg.angular.y = 0;

    // PID update
    effort = pid.updatePid(track_msg->x - MID_X, time - last_time);
    move_msg.angular.z = -effort / SCALE *  MAX_POWER;
    if (move_msg.angular.z >  MAX_POWER) move_msg.angular.z =  MAX_POWER;  
    if (move_msg.angular.z < -MAX_POWER) move_msg.angular.z = -MAX_POWER;  
 
    // Execute turn
    mover.publish(move_msg);

    // debug output
    plot_msg.x = track_msg->x - MID_X;
    plot_msg.y = - effort;
    plot_msg.z = move_msg.angular.z;
    plot.publish(plot_msg);
  }