| Note: This tutorial assumes you already completed the getting started tutorial. |
Creating an full robot in NXT-ROS
Description: This tutorial shos you how to create an nxt_ros.yaml file for you nxt robot and launch it to view the data.Tutorial Level: BEGINNER
Next Tutorial: Creating a simple robot model using lxf2urdf.py
Conncect Sensors
For this tutorial, let's add some more sensors and motors: plug in a touch sensor, a color sensor, an ultrasonic sensor, and a servo motor.
- PORT1: intensity sensor
- PORT2: ultrasonic sensor
- PORT3: touch sensor
- PORTA: servo
Create robot.yaml
The yaml file
First, create learning_nxt/robot.yaml in your favorite editor, and place the following inside it:
1 nxt_robot:
2 - type: motor
3 name: l_motor_joint
4 port: PORT_A
5 desired_frequency: 10.0
6 - type: touch
7 frame_id: r_touch_link
8 name: touch_sensor
9 port: PORT_3
10 desired_frequency: 10.0
11 - type: ultrasonic
12 frame_id: r_ultrasonic_link
13 name: ultrasonic_sensor
14 port: PORT_2
15 spread_angle: 0.2
16 min_range: 0.01
17 max_range: 2.5
18 desired_frequency: 10.0
19 - type: intensity
20 frame_id: l_intensity_link
21 name: intensity_sensor
22 port: PORT_1
23 color_r: 1.0
24 color_g: 0.0
25 color_b: 0.0
26 desired_frequency: 10.0
The yaml explained
Now, let's break down the ymal piece by piece.
1 nxt_robot:
Here we are putting everything in the nxt_robot namespace.
These lines creates a motor object with name L_motor_joint that are connected to PORT_A with a pulling frequency of 10Hz.
These lines creates a touch object with name touch_sensor and a frame_id r_touch_link of that is connected to PORT_3. The pulling frequency in this case is 10Hz.
These lines creates an ultrasonic sensor with a spread angle of 0.2m, a min range of 0.01m, and a max range of 2.5m that is connected to PORT_2.
These lines creates a intensity object with name intensity_sensor and a frame_id l_intensity_link of that is connected to PORT_1 with the red LED on.
Launch the yaml File
Now we need to create a launch file to launch the robot.yaml file. Create learning_nxt/robot.launch in your favorite editor, and place the following inside it:
<launch>
<node pkg="nxt_ros" type="nxt_ros.py" name="nxt_ros" output="screen" respawn="true">
<rosparam command="load" file="$(find learning_nxt)/robot.yaml" />
</node>
<node pkg="nxt_ros" type="joint_states_aggregator.py" name="joint_state_publisher" output="screen" />
</launch>Turn on your nxt brick and connect it to the computer via USB. Now roslaunch:
$ roslaunch robot.launch
You should see something similar to:
SUMMARY ======== PARAMETERS * /nxt_ros/nxt_robot NODES / nxt_ros (nxt_ros/nxt_ros.py) joint_state_publisher (nxt_ros/joint_states_aggregator.py) starting new master (master configured for auto start) process[master]: started with pid [32451] ROS_MASTER_URI=http://bvo:11311/ setting /run_id to 281dd58e-afb1-11df-98e9-00251148e8cf process[rosout-1]: started with pid [32464] started core service [/rosout] process[nxt_ros-3]: started with pid [32493] process[joint_state_publisher-4]: started with pid [32494] [INFO] 1282676127.009863: Creating motor with name l_motor_joint on PORT_A [INFO] 1282676127.016516: Creating touch with name touch_sensor on PORT_3 [INFO] 1282676127.022412: Creating ultrasonic with name ultrasonic_sensor on PORT_2 [INFO] 1282676127.127735: Creating intensity with name intensity_sensor on PORT_1
Viewing Data
Now you can list all the topics:
$ rostopic list
Now you can see all the sensor and joint data:
/intensity_sensor /joint_command /joint_state /joint_states /rosout /touch_sensor /ultrasonic_sensor
You will see topics for each sensor and state/command topics for the joints in this case (motor1 and motor2).
Run:
$ rostopic echo joint_states