ROS进阶学习手记 10 - 搭建自己的TurtleBot（4）- Nodes of Base Driver
ROS进阶学习手记 10 - 搭建自己的TurtleBot（4）- Nodes of Base Driver
Here we are going to continue playing with the launchfile:[ turtlebot_minimal_create.launch ]
and look into the nodes, topics, messages, publisher, and subscriber about that.
Let’s refer the log printed when we start this launchfile here:
SUMMARY
========
PARAMETERS
* /cmd_vel_mux/yaml_cfg_file
* /diagnostic_aggregator/analyzers/digital_io/path
* /diagnostic_aggregator/analyzers/digital_io/startswith
* /diagnostic_aggregator/analyzers/digital_io/timeout
* /diagnostic_aggregator/analyzers/digital_io/type
* /diagnostic_aggregator/analyzers/mode/path
* /diagnostic_aggregator/analyzers/mode/startswith
* /diagnostic_aggregator/analyzers/mode/timeout
* /diagnostic_aggregator/analyzers/mode/type
* /diagnostic_aggregator/analyzers/nodes/contains
* /diagnostic_aggregator/analyzers/nodes/path
* /diagnostic_aggregator/analyzers/nodes/timeout
* /diagnostic_aggregator/analyzers/nodes/type
* /diagnostic_aggregator/analyzers/power/path
* /diagnostic_aggregator/analyzers/power/startswith
* /diagnostic_aggregator/analyzers/power/timeout
* /diagnostic_aggregator/analyzers/power/type
* /diagnostic_aggregator/analyzers/sensors/path
* /diagnostic_aggregator/analyzers/sensors/startswith
* /diagnostic_aggregator/analyzers/sensors/timeout
* /diagnostic_aggregator/analyzers/sensors/type
* /diagnostic_aggregator/base_path
* /diagnostic_aggregator/pub_rate
* /robot/name
* /robot/type
* /robot_description
* /robot_pose_ekf/freq
* /robot_pose_ekf/imu_used
* /robot_pose_ekf/odom_used
* /robot_pose_ekf/output_frame
* /robot_pose_ekf/publish_tf
* /robot_pose_ekf/sensor_timeout
* /robot_pose_ekf/vo_used
* /robot_state_publisher/publish_frequency
* /rosdistro
* /rosversion
* /turtlebot_laptop_battery/acpi_path
* /turtlebot_node/bonus
* /turtlebot_node/port
* /turtlebot_node/update_rate
* /use_sim_time
NODES
/
cmd_vel_mux (nodelet/nodelet)
diagnostic_aggregator (diagnostic_aggregator/aggregator_node)
kinect_breaker_enabler (create_node/kinect_breaker_enabler.py)
mobile_base_nodelet_manager (nodelet/nodelet)
robot_pose_ekf (robot_pose_ekf/robot_pose_ekf)
robot_state_publisher (robot_state_publisher/robot_state_publisher)
turtlebot_laptop_battery (linux_hardware/laptop_battery.py)
turtlebot_node (create_node/turtlebot_node.py) 
Let’s run the commands below:
$ roslaunch rbx1_bringup turtlebot_minimal_create.launch
$ rostopic pub -r 10 /cmd_vel geometry_msgs/Twist '{linear: {x: 0.1, y: 0, z: 0}, angular: {x: 0, y: 0, z: 0.5}}'
this will make My Turtlebot_me (I call mine is Turtlebot_me) move slowly. so we can observe its nodes and messages.
then use the rqt tool to monitor the nodes and topics.:
$ rqt_graph
we get this:
Here we didn’t use ekf(Extended Karman Filter). Lets’ print out what’s in the topic /tf and /robot_pose_ekf
$ rostopic echo /tf
$ rostopic echo /robot_pose_ekf
We get below for /tf :
header:
seq: 0
stamp:
secs: 1448269102
nsecs: 722203525
frame_id: plate_2_link
child_frame_id: standoff_kinect_1_link
transform:
translation:
x: -0.1024382
y: -0.098
z: 0.0032004
rotation:
x: 0.0
y: 0.0
z: 0.0
w: 1.0
We can see there is no change except the nsecs num.
and:
$ rostopic echo /robot_pose_ekf
WARNING: topic [/robot_pose_ekf] does not appear to be published yet
Let’s see /joint_states & /diagnostics :
$ rostopic echo /joint_states
header:
seq: 395
stamp:
secs: 1448269407
nsecs: 869920969
frame_id: ''
name: ['left_wheel_joint', 'right_wheel_joint', 'front_castor_joint', 'back_castor_joint']
position: [0.0, 0.0, 0.0, 0.0]
velocity: [0.0, 0.0, 0.0, 0.0]
effort: [0.0, 0.0, 0.0, 0.0]
---
we see the ‘position’ is all zeros. This may be a proble of my gear wheel. I’ll try to fix it now.
& /diagnostics :
header:
seq: 2238
stamp:
secs: 1448269540
nsecs: 681997060
frame_id: ''
status:
-
level: 0
name: TurtleBot Node
message: RUNNING
hardware_id: ''
values: []
-
level: 0
name: Operating Mode
message: Full
hardware_id: ''
values: []
-
level: 0
name: Battery
message: OK
hardware_id: ''
values:
-
key: Voltage (V)
value: 15.613
-
key: Current (A)
value: -0.344
-
key: Temperature (C)
value: 32
-
key: Charge (Ah)
value: 2.297
-
key: Capacity (Ah)
value: 2.696
-
level: 0
name: Charging Sources
message: None
hardware_id: ''
values: []
-
level: 0
name: Cliff Sensor
message: OK
hardware_id: ''
values:
-
key: Left
value: False
-
key: Left Signal
value: 2475
-
key: Front Left
value: False
-
key: Front Left Signal
value: 2561
-
key: Front Right
value: False
-
key: Front Right Signal
value: 2606
-
key: Right
value: False
-
key: Right Signal
value: 2609
-
level: 0
name: Wall Sensor
message: OK
hardware_id: ''
values:
-
key: Wall
value: False
-
key: Wall Signal
value: 61
-
key: Virtual Wall
value: False
-
level: 2
name: Gyro Sensor
message: Gyro Power Problem: For more information visit http://answers.ros.org/question/2091/turtlebot-bad-gyro-calibration-also.
hardware_id: ''
values:
-
key: Gyro Enabled
value: True
-
key: Raw Gyro Rate
value: 0
-
key: Calibration Offset
value: 0
-
key: Calibration Buffer
value: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
-
level: 0
name: Digital Outputs
message: OK
hardware_id: ''
values:
-
key: Raw Byte
value: 1
-
key: Digital Out 2
value: ON
-
key: Digital Out 1
value: OFF
-
key: Digital Out 0
value: OFF
---
we see a lot of ‘0’s here. This may be a proble of my gear wheel. I’ll try to fix it now.
This should be read:http://answers.ros.org/question/31935/createroomba-odometry/?answer=221438#post-id-221438
Note this message (from: iRobot_Roomba_600_Open_Interface_Spec_0908.pdf)
NOTE: Create 2 and Roomba 500/600 firmware versions prior to 3.3.0 return an incorrect value for
sensors measured in millimeters. It is recommended that you read the left and right encoder counts
directly (packets IDs 43 and 44) and do the unit conversion yourself.
To determine the firmware version on your robot, send a 7 via the serial port to reset it. The robot will
print a long welcome message which will include the firmware version, for example:
r3_robot/tags/release-3.3.0.
Looks like i’m going to read the real value of distace and do the unit convert by my self.(mine is 3.2.0)
The ‘Create Open Interface_v2.pdf’ shows us a 25pin connector which is not contained in ROOMBA600/Create2.
Now the Tasks are:
- First read out the ‘packets IDs 43 and 44’ and convert them into distance.
- Read out the ‘packet IDs 43 and 44’: angle in radians = (right wheel distance – left wheel distance) / wheel base distance.
- Understand and modify the base driver, and to let it read packet IDs 43 and 44, and let it convert them into pose and direction.
- make the base driver publish the pose info as a topic.
- make all the systems started by the turtlebot_bringup_minimal_me.launch file works well along with that replaced the Gyro data by the Distance data.
- Add an enternal Gyro Sensor and intergrate it into the systems started by the turtlebot_bringup_minimal_me.launch file. Make the system works well.
Let’s get into the 1st one next blog. :)