# ROS Tutorials ## we will start by creating a package ``` cd ~/catkin_ws/src catkin_create_pkg turtlesim_cleaner geometry_msgs rospy ``` we created a pkg named turtlesim\_cleaner with geometry\_msgs and rospy dependency. ``` cd ~/catkin_ws catkin_make cd ~/catkin_ws/src/turtlesim_cleaner mkdir src cd ~/catkin_ws catkin_make ``` catkin\_make and creating a src folder for our package. ``` cd ~/catkin_ws/src/turtlesim_cleaner/src gedit move.py ``` this opens a empty file ``` #!/usr/bin/env python import rospy from geometry_msgs.msg import Twist def move(): # Starts a new node rospy.init_node('robot_cleaner', anonymous=True) velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10) vel_msg = Twist() #Receiveing the user's input print("Let's move your robot") speed = input("Input your speed:") distance = input("Type your distance:") isForward = input("Foward?: ")#True or False #Checking if the movement is forward or backwards if(isForward): vel_msg.linear.x = abs(speed) else: vel_msg.linear.x = -abs(speed) #Since we are moving just in x-axis vel_msg.linear.y = 0 vel_msg.linear.z = 0 vel_msg.angular.x = 0 vel_msg.angular.y = 0 vel_msg.angular.z = 0 while not rospy.is_shutdown(): #Setting the current time for distance calculus t0 = rospy.Time.now().to_sec() current_distance = 0 #Loop to move the turtle in an specified distance while(current_distance < distance): #Publish the velocity velocity_publisher.publish(vel_msg) #Takes actual time to velocity calculus t1=rospy.Time.now().to_sec() #Calculates distancePoseStamped current_distance= speed*(t1-t0) #After the loop, stops the robot vel_msg.linear.x = 0 #Force the robot to stop velocity_publisher.publish(vel_msg) if __name__ == '__main__': try: #Testing our function move() except rospy.ROSInterruptException: pass ``` ``` #for making your phython node executable. chmod u+x ~/catkin_ws/src/turtlesim_cleaner/src/move.py ``` Now testing code ``` roscore #open new terminal rosrun turtlesim turtlesim_node #this will open simulator #run our straight line node rosrun turtlesim_cleaner move.py ``` Rotate Node ``` cd ~/catkin_ws/src/turtlesim_cleaner/src gedit rotate.py ``` ``` #!/usr/bin/env python import rospy from geometry_msgs.msg import Twist PI = 3.1415926535897 def rotate(): #Starts a new node rospy.init_node('robot_cleaner', anonymous=True) velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10) vel_msg = Twist() # Receiveing the user's input print("Let's rotate your robot") speed = input("Input your speed (degrees/sec):") angle = input("Type your distance (degrees):") clockwise = input("Clockwise?: ") #True or false #Converting from angles to radians angular_speed = speed*2*PI/360 relative_angle = angle*2*PI/360 #We wont use linear components vel_msg.linear.x=0 vel_msg.linear.y=0 vel_msg.linear.z=0 vel_msg.angular.x = 0 vel_msg.angular.y = 0 # Checking if our movement is CW or CCW if clockwise: vel_msg.angular.z = -abs(angular_speed) else: vel_msg.angular.z = abs(angular_speed) # Setting the current time for distance calculus t0 = rospy.Time.now().to_sec() current_angle = 0 while(current_angle < relative_angle): velocity_publisher.publish(vel_msg) t1 = rospy.Time.now().to_sec() current_angle = angular_speed*(t1-t0) #Forcing our robot to stop vel_msg.angular.z = 0 velocity_publisher.publish(vel_msg) rospy.spin() if __name__ == '__main__': try: # Testing our function rotate() except rospy.ROSInterruptException: pass ``` ``` #for making your phython node executable. chmod u+x ~/catkin_ws/src/turtlesim_cleaner/src/rotate.py ``` ``` roscore #open new terminal rosrun turtlesim turtlesim_node #this will open simulator #run our straight line node rosrun turtlesim_cleaner rotate.py ``` Go to Goal ``` cd ~/catkin_ws/src/turtlesim_cleaner/src gedit gotogoal.py ``` ``` #!/usr/bin/env python #!/usr/bin/env python import rospy from geometry_msgs.msg import Twist from turtlesim.msg import Pose from math import pow, atan2, sqrt class TurtleBot: def __init__(self): # Creates a node with name 'turtlebot_controller' and make sure it is a # unique node (using anonymous=True). rospy.init_node('turtlebot_controller', anonymous=True) # Publisher which will publish to the topic '/turtle1/cmd_vel'. self.velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10) # A subscriber to the topic '/turtle1/pose'. self.update_pose is called # when a message of type Pose is received. self.pose_subscriber = rospy.Subscriber('/turtle1/pose', Pose, self.update_pose) self.pose = Pose() self.rate = rospy.Rate(10) def update_pose(self, data): """Callback function which is called when a new message of type Pose is received by the subscriber.""" self.pose = data self.pose.x = round(self.pose.x, 4) self.pose.y = round(self.pose.y, 4) def euclidean_distance(self, goal_pose): """Euclidean distance between current pose and the goal.""" return sqrt(pow((goal_pose.x - self.pose.x), 2) + pow((goal_pose.y - self.pose.y), 2)) def linear_vel(self, goal_pose, constant=1.5): return constant * self.euclidean_distance(goal_pose) def steering_angle(self, goal_pose): return atan2(goal_pose.y - self.pose.y, goal_pose.x - self.pose.x) def angular_vel(self, goal_pose, constant=6): return constant * (self.steering_angle(goal_pose) - self.pose.theta) def move2goal(self): """Moves the turtle to the goal.""" goal_pose = Pose() # Get the input from the user. goal_pose.x = input("Set your x goal: ") goal_pose.y = input("Set your y goal: ") # Please, insert a number slightly greater than 0 (e.g. 0.01). distance_tolerance = input("Set your tolerance: ") vel_msg = Twist() while self.euclidean_distance(goal_pose) >= distance_tolerance: # Porportional controller. # https://en.wikipedia.org/wiki/Proportional_control # Linear velocity in the x-axis. vel_msg.linear.x = self.linear_vel(goal_pose) vel_msg.linear.y = 0 vel_msg.linear.z = 0 # Angular velocity in the z-axis. vel_msg.angular.x = 0 vel_msg.angular.y = 0 vel_msg.angular.z = self.angular_vel(goal_pose) # Publishing our vel_msg self.velocity_publisher.publish(vel_msg) # Publish at the desired rate. self.rate.sleep() # Stopping our robot after the movement is over. vel_msg.linear.x = 0 vel_msg.angular.z = 0 self.velocity_publisher.publish(vel_msg) # If we press control + C, the node will stop. rospy.spin() if __name__ == '__main__': try: x = TurtleBot() x.move2goal() except rospy.ROSInterruptException: pass ``` ``` chmod u+x ~/catkin_ws/src/turtlesim_cleaner/src/gotogoal.py ``` ``` roscore #open new terminal rosrun turtlesim turtlesim_node #this will open simulator #in a new terminal #run our straight line node rosrun turtlesim_cleaner gotogoal.py ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://sankeerthreddy1002.gitbook.io/wally/ros-tutorials.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.