Init commit.

src/navigation.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python
+
+import rospy
+import actionlib
+
+# We need the MoveBaseAction and MoveBaseGoal from the move_base_msgs package.
+from move_base_msgs.msg import MoveBaseAction, MoveBaseGoal
+
+# We're going to use the quaternion type here.
+from geometry_msgs.msg import Quaternion
+
+# tf includes a handy set of transformations to move between Euler angles and quaternions (and back).
+from tf import transformations
+
+import sys
+
+
+class StretchNavigation:
+    """
+    A simple encapsulation of the navigation stack for a Stretch robot.
+    """
+    def __init__(self):
+        """
+        Create an instance of the simple navigation interface.
+        :param self: The self reference.
+        """
+        # Make an action client, and wait for the server.
+        self.client = actionlib.SimpleActionClient('move_base', MoveBaseAction)
+        self.client.wait_for_server()
+        rospy.loginfo('{0}: Made contact with move_base server'.format(self.__class__.__name__))
+
+        # Initialize the callback functions
+        self.active_callback = None
+        self.feedback_callback = None
+        self.done_callback = None
+
+        # Create a MoveBaseGoal message type, and fill in all of the relevant fields.
+        self.goal = MoveBaseGoal()
+        self.goal.target_pose.header.frame_id = 'map'
+        self.goal.target_pose.header.stamp = rospy.Time()
+
+        # Set a position in the coordinate frame
+        self.goal.target_pose.pose.position.x = 0.0
+        self.goal.target_pose.pose.position.y = 0.0
+        self.goal.target_pose.pose.position.z = 0.0
+
+        # Set a orientation in the coordinate frame
+        self.goal.target_pose.pose.orientation.x = 0.0
+        self.goal.target_pose.pose.orientation.y = 0.0
+        self.goal.target_pose.pose.orientation.z = 0.0
+        self.goal.target_pose.pose.orientation.w = 1.0
+
+    def get_quaternion(self,theta):
+        """
+        A function to build Quaternians from Euler angles. Since the Stretch only
+        rotates around z, we can zero out the other angles.
+
+        :param theta: The angle the robot makes with the x-axis.
+        """
+        return Quaternion(*transformations.quaternion_from_euler(0.0, 0.0, theta))
+
+    def go_to(self, x, y, theta, wait=False):
+        """
+        Drive the robot to a particlar pose on the map. The Stretch only needs
+        (x, y) coordinates and a heading.
+
+        :param x: x coordinate in the map frame.
+        :param y: y coordinate in the map frame.
+        :param theta: heading (angle with the x-axis in the map frame)
+        """
+        rospy.loginfo('{0}: Heading for ({1}, {2}) at {3} radians'.format(self.__class__.__name__,
+        x, y, theta))
+
+        # Set the x and y positions
+        self.goal.target_pose.pose.position.x = x
+        self.goal.target_pose.pose.position.y = y
+
+        # Set the orientation.  This is a quaternion, so we use the helper function.
+        self.goal.target_pose.pose.orientation = self.get_quaternion(0.0)
+
+        # Make the action call.  Include the callbacks.  Unless these have been set somewhere else, they are passed
+        # as None, which means no callback.
+        self.client.send_goal(self.goal,
+                              active_cb=self.active_callback,
+                              feedback_cb=self.feedback_callback,
+                              done_cb=self.done_callback)
+
+        self.client.wait_for_result()
+
+
+if __name__ == '__main__':
+    # Initialize the node, and call it "navigation"
+	rospy.init_node('navigation', argv=sys.argv)
+
+	# Declare a `StretchNavigation` object
+	nav = StretchNavigation()
+
+    # Send a nav goal to the `go_to()` method
+	nav.go_to(0.25, 0.0, 0.0, wait=True)