"""
Defines the Action for the 2D Multi-Object Search domain;
Action space:
Motion :math:`\cup` Look :math:`\cup` Find
* Motion Actions scheme 1: South, East, West, North.
* Motion Actions scheme 2: Left 45deg, Right 45deg, Forward
* Look: Interprets sensor input as observation
* Find: Marks objects observed in the last Look action as
(differs from original paper; reduces action space)
It is possible to force "Look" after every N/S/E/W action;
then the Look action could be dropped. This is optional behavior.
"""
import pomdp_py
import math
###### Actions ######
[docs]
class Action(pomdp_py.Action):
"""Mos action; Simple named action."""
def __init__(self, name):
self.name = name
def __hash__(self):
return hash(self.name)
def __eq__(self, other):
if isinstance(other, Action):
return self.name == other.name
elif type(other) == str:
return self.name == other
def __str__(self):
return self.name
def __repr__(self):
return "Action(%s)" % self.name
MOTION_SCHEME = "xy" # can be either xy or vw
STEP_SIZE = 1
[docs]
class MotionAction(Action):
# scheme 1 (vx,vy,th)
SCHEME_XYTH = "xyth"
EAST = (STEP_SIZE, 0, 0) # x is horizontal; x+ is right. y is vertical; y+ is down.
WEST = (-STEP_SIZE, 0, math.pi)
NORTH = (0, -STEP_SIZE, 3 * math.pi / 2)
SOUTH = (0, STEP_SIZE, math.pi / 2)
# scheme 2 (vt, vw) translational, rotational velocities.
SCHEME_VW = "vw"
FORWARD = (STEP_SIZE, 0)
BACKWARD = (-STEP_SIZE, 0)
LEFT = (0, -math.pi / 4) # left 45 deg
RIGHT = (0, math.pi / 4) # right 45 deg
# scheme 3 (vx,vy)
SCHEME_XY = "xy"
EAST2D = (STEP_SIZE, 0) # x is horizontal; x+ is right. y is vertical; y+ is down.
WEST2D = (-STEP_SIZE, 0)
NORTH2D = (0, -STEP_SIZE)
SOUTH2D = (0, STEP_SIZE)
SCHEMES = {"xyth", "xy", "vw"}
def __init__(self, motion, scheme=MOTION_SCHEME, distance_cost=1, motion_name=None):
"""
motion (tuple): a tuple of floats that describes the motion;
scheme (str): description of the motion scheme; Either
"xy" or "vw"
"""
if scheme not in MotionAction.SCHEMES:
raise ValueError("Invalid motion scheme %s" % scheme)
if scheme == MotionAction.SCHEME_XYTH:
if motion not in {
MotionAction.EAST,
MotionAction.WEST,
MotionAction.NORTH,
MotionAction.SOUTH,
}:
raise ValueError("Invalid move motion %s" % str(motion))
elif scheme == MotionAction.SCHEME_VW:
if motion not in {
MotionAction.FORWARD,
MotionAction.BACKWARD,
MotionAction.LEFT,
MotionAction.RIGHT,
}:
raise ValueError("Invalid move motion %s" % str(motion))
elif scheme == MotionAction.SCHEME_XY:
if motion not in {
MotionAction.EAST2D,
MotionAction.WEST2D,
MotionAction.NORTH2D,
MotionAction.SOUTH2D,
}:
raise ValueError("Invalid move motion %s" % str(motion))
self.motion = motion
self.scheme = scheme
self.distance_cost = distance_cost
if motion_name is None:
motion_name = str(motion)
super().__init__("move-%s-%s" % (scheme, motion_name))
# Define some constant actions
MoveEast = MotionAction(
MotionAction.EAST, scheme=MotionAction.SCHEME_XYTH, motion_name="East"
)
MoveWest = MotionAction(
MotionAction.WEST, scheme=MotionAction.SCHEME_XYTH, motion_name="West"
)
MoveNorth = MotionAction(
MotionAction.NORTH, scheme=MotionAction.SCHEME_XYTH, motion_name="North"
)
MoveSouth = MotionAction(
MotionAction.SOUTH, scheme=MotionAction.SCHEME_XYTH, motion_name="South"
)
MoveForward = MotionAction(
MotionAction.FORWARD, scheme=MotionAction.SCHEME_VW, motion_name="Forward"
)
MoveBackward = MotionAction(
MotionAction.BACKWARD, scheme=MotionAction.SCHEME_VW, motion_name="Backward"
)
MoveLeft = MotionAction(
MotionAction.LEFT, scheme=MotionAction.SCHEME_VW, motion_name="TurnLeft"
)
MoveRight = MotionAction(
MotionAction.RIGHT, scheme=MotionAction.SCHEME_VW, motion_name="TurnRight"
)
MoveEast2D = MotionAction(
MotionAction.EAST2D, scheme=MotionAction.SCHEME_XY, motion_name="East2D"
)
MoveWest2D = MotionAction(
MotionAction.WEST2D, scheme=MotionAction.SCHEME_XY, motion_name="West2D"
)
MoveNorth2D = MotionAction(
MotionAction.NORTH2D, scheme=MotionAction.SCHEME_XY, motion_name="North2D"
)
MoveSouth2D = MotionAction(
MotionAction.SOUTH2D, scheme=MotionAction.SCHEME_XY, motion_name="South2D"
)
[docs]
class LookAction(Action):
# For simplicity, this LookAction is not parameterized by direction
def __init__(self):
super().__init__("look")
[docs]
class FindAction(Action):
def __init__(self):
super().__init__("find")
Look = LookAction()
Find = FindAction()
if MOTION_SCHEME == "xy":
ALL_MOTION_ACTIONS = [MoveEast, MoveWest, MoveNorth, MoveSouth]
elif MOTION_SCHEME == "vw":
ALL_MOTION_ACTIONS = [MoveForward, MoveBackward, MoveLeft, MoveRight]
else:
raise ValueError("motion scheme '%s' is invalid" % MOTION_SCHEME)
