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2016-07-25 16:39:02 -0600 asked a question Inbound TCP/IP connection failed

I'm getting this warning when launching a .launch file. I have already configured my network and i have also exported master URI on slave.

Inbound TCP/IP connection failed: connection from sender terminated before handshake header received. 0 >bytes were received. Please check sender for additional details

Why is this happening? I'm using ros on two pc's connected via wifi. Pinging each one i get approx 20ms of delay.

2016-07-25 15:44:45 -0600 commented answer catkin is not creating package.

Thank u! this was exactly what i was missing

2016-07-25 15:44:01 -0600 answered a question catkin is not creating package.

Thank u man!

2016-07-25 15:38:00 -0600 asked a question catkin is not creating package.

cd ~/catkin_ws/src
catkin_create_pkg mypack
cd ..

Everything is ok.

roscd mypack
mypack not found.


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2016-07-25 13:48:44 -0600 commented answer Obstacle avoidance with navigation stack without map!

Hello cagatay! Can you explain better? I have local planner, global costmap and local costmap configured, what should i do now?

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2016-07-22 05:53:39 -0600 asked a question What is the difference between tf_broadcaster and tf_listener?

I'm trying to code tf configuration in navigation stack, i'm having some problem in understanding if i need to code one tf_broadcaster and one tf_listener for each sensor or just one tf_broadcaster per sensor.

For example:
My robot has 4 sonar sensor, i'm publishing they'r values as 4 Range messages and 1 LaserScan message.
In the same node where values of sensor are taken i coded 4 tf_broadcaster per 4 Range messages, and 1 tf_broadcaster per LaserScan message.
Should i code even the tf_listener? What is the right configuration for my case? Can u help me? Thank u!

2016-07-21 05:07:44 -0600 asked a question Robot is not moving, Please check my rqt_graph

Hello everyone, i'm trying to create a map for my robot, i'm following this guide:

So, i launch my_robot_configuration.launch and move_base.launch from the navigation stack.

i'm giving the following commands from the previous guide:

rosrun gmapping slam_gmapping scan:=sonar_laser_scan
rosbag record -O sonarscan /sonar_laser_scan /tf

Everything seems okay, so now i open rviz to lookup what is going on:

rosrun rviz rviz

and set up a static map on topic /map to see the results.

The maps shows up, but the robot is stuck in start position. I would like to let my robot move avoiding obstacles in order to create a map. I tried to set up 2d nav goal, but nothing is happening.

Here is my rqt_graph:


Here is my rviz:


How can i move my robot in order to create the map? is there something wrong with my rqt_graph? Thank u so much!

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2016-07-19 16:42:06 -0600 asked a question Obstacle avoidance with navigation stack without map!

I've got a little robot with 4 sonar sensor, is it possible to do obstacle avoidance without have a map? I've just finish to configure navigation stack and setting up launch files, but now i'm stuck. Thank u!

2016-07-19 15:20:36 -0600 marked best answer How to use cmd_vel data in navigation stack?

I'm trying to convert geometry_msgs::Twist message received from cmd_vel topic to something that can make my arduino robot move. I know that from geometry_msgs::Twist message i'll receive linear velocity and angular velocity. My motors are actually controlled by calling functions like that:

void RobotControl::goAhead(int PWM){

digitalWrite(_IN1, LOW); digitalWrite(_IN2, HIGH);

digitalWrite(_IN3, LOW);

digitalWrite(_IN4, HIGH);

analogWrite(_ENB, PWM);

analogWrite(_ENA, PWM); }

in this case, PWM is a value between 0 and 200 and sets speed for my motors in this range.

The main question is:

Is there a way to use received cmd_vel data and convert this to instructions that can make my robot move by simpy call goAhead() function? If my goAhead function has not been implemented in the right way, how to implement a funciton that solve the problem?

Thank u!

--- EDIT--- ok, let's see if i understand this:

velCallback(Twist &twistmsg) {
vel_x = twistmsg.linear.x;
vel_th = twistmsg.angular.z;
if(vel_x == 0){
right_vel = vel_th * width_robot / 2.0;
left_vel = (-1) * right_vel; }
else if(vel_th == 0){
left_vel = right_vel = vel_x;
left_vel = vel_x - vel_th / 2.0;
right_vel = vel_x + vel_th / 2.0;

now if everything is right i can calcolate RPM:

RPMleft = ((60 * left_vel) / (diameter * PI))
RPMright = ((60 * right_vel) / (diameter * PI))

now i should calcalate PWM, i googled for almost one hour but i can't find anything. Do you know how can i do it?

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2016-07-18 06:36:27 -0600 asked a question Problem with Int32MultiArray publisher/subscriber

I have a problem with a Int32Multiarray message.

My publisher is like that:

std_msgs::Int32MultiArray msg;

and my subscriber uses rosserial, so it is like that:

void motorCmdVelSub(const std_msgs::Int32MultiArray& msg)
char temp_msg[100];
long int sx;
long int dx;[0];[1];
sprintf(temp_msg,"left %ld , right %ld", sx, dx);

when i execute:

'rostopic echo motor'

it prints:

dim: []
data_offset: 0
data: [255, 255]

and this are the right values, but at the same time my subscriber via function call to nh.loginfo prints out to me the wrong values.

sx 128 dx 255

Can you help me? thank u!

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2016-07-18 01:46:56 -0600 asked a question How to configure navigation stack?

I know that there should be many tutorials about this but i can't find anything. I've just set publishers and subscribers for sensors stuff, odometry stuff and IMU. Now, how can i set everything to notice navigation stack the creation of this stuff? what configuration files should i create? and where? Thank you! ps: My sensors are sonar, i published a Range message, i've read that it is possible to integrate this in navigation stack, but how?