# Revision history [back]

This answer is a bit of a copy-paste. The task you describe is the first assignment in Brown's CS148 Introduction to Robotics course. Here's a solution that isn't exactly pretty but presumably, at some point, did work... :P

#!/usr/bin/env python
import rospy
import random
from geometry_msgs.msg import Twist
from turtlebot_node.msg import TurtlebotSensorState

# global variables
bump = False

action_duration = 0.25
movement_speed = 0.15
turn_speed = 0.5
min_turn_duration = 3.5
max_turn_duration = 10.5

def processSensing(TurtlebotSensorState):
global bump
bump = TurtlebotSensorState.bumps_wheeldrops
#newInfo = True

def hello_create():
pub = rospy.Publisher('/turtlebot_node/cmd_vel', Twist)
rospy.Subscriber('/turtlebot_node/sensor_state', TurtlebotSensorState, processSensing)
rospy.init_node('hello_create')
#listen
global bump
twist = Twist()
while not rospy.is_shutdown():
if bump==1:
str = "right bumper, turning left %s"%rospy.get_time()
turn(pub, random_duration(), turn_speed)
elif bump==2:
str = "left bumper, turning right %s"%rospy.get_time()
turn(pub, random_duration(), -turn_speed)
elif bump==3:
str = "both bumpers, turning left %s"%rospy.get_time()
turn(pub, random_duration(), turn_speed)
else:
str = "moving straight ahead %s"%rospy.get_time()
twist.linear.x = movement_speed; twist.linear.y = 0; twist.linear.z = 0
twist.angular.x = 0; twist.angular.y = 0; twist.angular.z = 0
bump = False
pub.publish(twist)
rospy.sleep(action_duration)

def random_duration():
# Calculates a random amount of time for the Roomba to turn for
duration = min_turn_duration + random.random() * (max_turn_duration - min_turn_duration)
str = "Random duration: %s"%duration
return duration

def turn(pub, duration, weight):
twist = Twist()

# First, back up slightly from the wall
twist.linear.x = -movement_speed; twist.linear.y = 0; twist.linear.z = 0
twist.angular.x = 0; twist.angular.y = 0; twist.angular.z = 0
pub.publish(twist)
rospy.sleep(action_duration)

# Now, keep turning until the end of the specified duration
currentTime = rospy.get_time();
stopTime = rospy.get_time() + duration;
while (rospy.get_time() < stopTime):
str = "turning %s"%rospy.get_time()