ROS and MORSE tutorial ros¶
This is an extension of the current tutorial using the ROS as our middleware (instead of raw sockets).
The builder script is the same as the one used in the sockets tutorial.
Except the part on the inteface, which in this case is ROS.
You can find it in examples/tutorials/tutorial-1-ros.py.
Configuring ROS¶
pose.add_stream('ros')
motion.add_stream('ros')
Running the simulation¶
Run morse with:
morse run examples/tutorials/tutorial-1-ros.py
In another terminal, use the rostopic, rqt_plot and rqt_graph
commands to control the robot.
rostopic¶
First, send a motion command to the robot’s MotionVW actuator:
rostopic pub -1 /atrv/motion geometry_msgs/Twist "{linear: {x: .5}, angular: {z: .5}}"
pubstands for publish-1will publish 1 message/atrv/motioncorrespond to the robots’s motion controller topicgeometry_msgs/Twistis the message’s type"{linear: {x: .8}, angular: {z: .5}}"the message in json0.8 m/s for the linear speed
v0.5 rad/s for the angular speed
w
Second, look at its pose:
rostopic echo -n10 /atrv/pose
echowill subscribe and print-n10will print 10 messages/atrv/posecorrespond to the robots’s pose sensor topic
rqt_plot¶
Once you sent a motion command, you can plot the pose in realtime with:
rqt_plot /atrv/pose/pose/position/x,/atrv/pose/pose/position/y /atrv/pose/pose/orientation/z
Note
in former ROS versions, this tool was called rxplot
rqt_grah¶
It’s an alternative to rostopic list showing a connexion of nodes and topics.
rospy¶
From a terminal, start an interactive Python session typing python
and paste the following code:
import rospy
from geometry_msgs.msg import PoseStamped
from geometry_msgs.msg import Twist
cmd = rospy.Publisher("/atrv/motion", Twist)
motion = Twist()
def callback(msg):
position = msg.pose.position
if position.x < 1:
motion.linear.x = +0.5
if position.x > 2:
motion.linear.x = -0.5
cmd.publish(motion)
rospy.init_node("rostuto1")
rospy.Subscriber("/atrv/pose", PoseStamped, callback)
rospy.spin() # this will block untill you hit Ctrl+C
You should see the robot move forward then backward after 1m.
etc¶
For more, visit ROS wiki, where you will find many well written tutorials