Updated scan filter script.

src/scan_filter.py

@@ -9,35 +9,30 @@ from sensor_msgs.msg import LaserScan
 
 class Scanfilter:
 	def __init__(self):
+		# We're going to assume that the robot is pointing up the x-axis, so that
 
-		# We're going to assume that the robot is pointing up the x-axis, so that any points with y coordinates further
-		# than half a robot width from the axis are not in front of the robot.
-		self.extent = .5 / 2.0
+		# any points with y coordinates further than half of the defined
+		# width (1 meter) from the axis are not considered.
+		self.width = 1
+		self.extent = self.width / 2.0
 
-		# Set up a subscriber.  We're going to subscribe to the topic "counter",
-		# looking for Int64 messages.  When a message comes in, ROS is going to pass
-		# it to the function "callback" automatically.
+		# Set up a subscriber.  We're going to subscribe to the topic "scan",
+		# looking for LaserScan messages.  When a message comes in, ROS is going
+		# to pass it to the function "callback" automatically.
 		self.sub = rospy.Subscriber('/scan', LaserScan, self.callback)
-		self.pub = rospy.Publisher('filtered_scan', LaserScan, queue_size=10)
 
+		# Set up a publisher.  This will publish on a topic called "filtered_scan",
+		# with a LaserScan message type.
+		self.pub = rospy.Publisher('filtered_scan', LaserScan, queue_size=10)
 
 	def callback(self,msg):
-		# print('Minimum scan value = ' + str(len(msg.ranges)))
-		#
-		# center_index = len(msg.ranges)/3
-		# rospy.sleep(1)
-		"""
-		:param self: Self reference.
-		:param msg: LaserScan message.
-		"""
-
 		# Figure out the angles of the scan.  We're going to do this each time, in case we're subscribing to more than one
 		# laser, with different numbers of beams.
 		angles = linspace(msg.angle_min, msg.angle_max, len(msg.ranges))
 
-		# # Work out the y coordinates of the ranges.
+		# Work out the y coordinates of the ranges.
 		points = [r * sin(theta) if (theta < -2.5 or theta > 2.5) else inf for r,theta in zip(msg.ranges, angles)]
-		#
+
 		# If we're close to the x axis, keep the range, otherwise use inf, which means "no return".
 		new_ranges = [r if abs(y) < self.extent else inf for r,y in zip(msg.ranges, points)]
 
@@ -46,10 +41,13 @@ class Scanfilter:
 		self.pub.publish(msg)
 
 if __name__ == '__main__':
-	# Initialize the node, and call it "move".
+	# Initialize the node, and call it "scan_filter".
 	rospy.init_node('scan_filter')
 
-	# Setup Move class to base_motion
-	Scan()
+	# Setup Scanfilter class
+	Scanfilter()
 
+	# Give control to ROS.  This will allow the callback to be called whenever new
+	# messages come in.  If we don't put this line in, then the node will not work,
+	# and ROS will not process any messages.
 	rospy.spin()