Perform the steps in exercise 4. Prepare a document with screenshots from your Linux terminal to showcase that the steps were successfully followed. Use 10 seconds instead of five seconds in the document.

Exercise 4:

I need Output SS of Linux Terminal of all steps that is Necessary

The scope of the fourth exercise is to understand the ROS architecture, nodes, and a communication among nodes using action. A client node will contact the server node and the server node will wait for a stipulated duration; then the client node will print the elapsed duration.

1: (First time only)

(2) Create the skeleton for ROS package

Following segments changes based on the home works and directories;

user@hostname$ cd ~/catkin_ws/src

(a project based on rospy package package dependency)

user@hostname$ catkin_create_pkg ex4 rospy

user@hostname$ ls

user@hostname$ cd ex4

user@hostname$ ls

(list and check the files within the directory)

(3) Changes to the package.xml

Edit the packages.xml in the directory ~/catkin_ws/src/ex4 as follows:

roscpp

rospy

std_msgs

message_generation

actionlib_msgs

actionlib_msgs

roscpp

rospy

std_msgs

message_runtime

(4) Create an action file

user@hostname$ cd ~/catkin_ws/src/ex4

user@hostname$ mkdir action

Create a file Tim.action with the following contents:

duration time_to_wait

---

duration time_elapsed

uint32 updates_sent

---

duration time_elapsed

duration time_remaining

(4) Changes to CMakeLists.txt file

Edit the CMakeLists.txt in the directory ~/catkin_ws/src/ex2 as follows:

find_package(catkin REQUIRED COMPONENTS

# other packages are already listed here

actionlib_msgs

)

Uncomment and make the following change:

add_action_files(

DIRECTORY action

FILES Tim.action

)

## Generate added messages and services with any dependencies listed here

Uncomment the following:

generate_messages(

DEPENDENCIES

actionlib_msgs

std_msgs

)

Uncomment and add the following:

catkin_package(

# INCLUDE_DIRS include

# LIBRARIES ex4

CATKIN_DEPENDS

actionlib_msgs

)

(5) Create the directory for python files

(directory for creating python scripts, later we will create other directories as srv, msg)

user@hostname$ cd ~/catkin_ws/src/ex4

user@hostname$ mkdir scripts

user@hostname$ ls -al

you should see the scripts directory

(4) Create the Python file as a node representing client

Open an editor for Python (I use Geany ), and store the following file as fancy_action_client.py in the directory scripts. (make sure indentation are proper for Python programs when you copy/paste)

#! /usr/bin/env python

# BEGIN ALL

#! /usr/bin/env python

import rospy

import time

import actionlib

from ex4.msg import TimAction, TimGoal, TimResult, TimFeedback

# BEGIN PART_1

def feedback_cb(feedback):

print('[Feedback] Time elapsed: %f'%(feedback.time_elapsed.to_sec()))

print('[Feedback] Time remaining: %f'%(feedback.time_remaining.to_sec()))

# END PART_1

rospy.init_node('timer_action_client')

client = actionlib.SimpleActionClient('timer', TimAction)

client.wait_for_server()

goal = TimGoal()

goal.time_to_wait = rospy.Duration.from_sec(5.0)

# BEGIN PART_5

# Uncomment this line to test server-side abort:

#goal.time_to_wait = rospy.Duration.from_sec(500.0)

# END PART_5

# BEGIN PART_2

client.send_goal(goal, feedback_cb=feedback_cb)

# END PART_2

# BEGIN PART_4

# Uncomment these lines to test goal preemption:

#time.sleep(3.0)

#client.cancel_goal()

# END PART_4

client.wait_for_result()

# BEGIN PART_3

print('[Result] State: %d'%(client.get_state()))

print('[Result] Status: %s'%(client.get_goal_status_text()))

print('[Result] Time elapsed: %f'%(client.get_result().time_elapsed.to_sec()))

print('[Result] Updates sent: %d'%(client.get_result().updates_sent))

# END PART_3

# END ALL

The client file will be inside the folder ~/catkin_ws/src/ex4/scripts

user@hostname$ cd ~/catkin_ws/src/ex4/scripts

Make the script executable

user@hostname$ chmod +x fancy_action_client.py

(5) Create the Python file as a node representing server

Open an editor for Python, and store the following file as fancy_action_server.py in the directory scripts. (make sure indentation are proper for Python programs when you copy/paste)

#! /usr/bin/env python

# BEGIN ALL

#! /usr/bin/env python

import rospy

import time

import actionlib

# BEGIN PART_1

from ex4.msg import TimAction, TimGoal, TimResult, TimFeedback

# END PART_1

def do_timer(goal):

start_time = time.time()

# BEGIN PART_2

update_count = 0

# END PART_2

# BEGIN PART_3

if goal.time_to_wait.to_sec() > 60.0:

result = TimResult()

result.time_elapsed = rospy.Duration.from_sec(time.time() - start_time)

result.updates_sent = update_count

server.set_aborted(result, "Timer aborted due to too-long wait")

return

# END PART_3

# BEGIN PART_4

while (time.time() - start_time) < goal.time_to_wait.to_sec():

# END PART_4

# BEGIN PART_5

if server.is_preempt_requested():

result = TimResult()

result.time_elapsed = rospy.Duration.from_sec(time.time() - start_time)

result.updates_sent = update_count

server.set_preempted(result, "Timer preempted")

return

# END PART_5

# BEGIN PART_6

feedback = TimFeedback()

feedback.time_elapsed = rospy.Duration.from_sec(time.time() - start_time)

feedback.time_remaining = goal.time_to_wait - feedback.time_elapsed

server.publish_feedback(feedback)

update_count += 1

# END PART_6

# BEGIN PART_7

time.sleep(1.0)

# END PART_7

# BEGIN PART_8

result = TimResult()

result.time_elapsed = rospy.Duration.from_sec(time.time() - start_time)

result.updates_sent = update_count

server.set_succeeded(result, "Timer completed successfully")

# END PART_8

rospy.init_node('timer_action_server')

server = actionlib.SimpleActionServer('timer', TimAction, do_timer, False)

server.start()

rospy.spin()

# END ALL

(6) Compile and build the Nodes Python Files

Both fancy_action_client.py and fancy_action_server.py should be in the directory ~/catkin_ws/src/ex4/scripts

user@hostname$ cd ~/catkin_ws/src/ex4/scripts

user@hostname$ ls

user@hostname$ chmod +x fancy_action_server.py

Compile the packages so ROS can use it:

user@hostname$ cd ~/catkin_ws

user@hostname$ catkin_make

(7) Run the code

One terminal to run roscore (main ROS application): Open a terminal and run the following:

user@hostname$ roscore

Second terminal 2nd window to run the client node. If you set the setup.bash properly you can use the roscd to get to the package directory; then to the scripts ( cd into scripts) directory. Use the following command to start the client node.

user@hostname$ roscd ex4

user@hostname$ cd scripts

user@hostname$ rosrun ex4 fancy_action_client.py

Third window to run the server node.

user@hostname$ roscd ex4

user@hostname$ cd scripts

user@hostname$ rosrun ex4 fancy_action_server.py

Observe the outputs

Uncomment the following lines at fancy_action_client.py

# Uncomment these lines to test goal preemption:

#time.sleep(3.0)

#client.cancel_goal()

Uncomment the following lines at fancy_action_client.py

# Uncomment this line to test server-side abort:

#goal.time_to_wait = rospy.Duration.from_sec(500.0)