class BugBrain:
# declearing constants
def LEFT_WALLFOLLOWING(self):
return 0;
def RIGHT_WALLFOLLOWING(self):
return 1;
def LEFT_SIDE(self):
return -1;
def RIGHT_SIDE(self):
return 1;
def TOLERANCE(self):
return planar.EPSILON;
def __init__(self, goal_x, goal_y, side):
self.wall_side = side;
self.wp_destination = Point(goal_x, goal_y);
self.path_started = False;
#the tolerence == planar.EPSILON at default value does not work good
planar.set_epsilon(0.1);
self.distance_when_left = 9999;
# method to determin if the destenation is on opposit side of wall being followed.
# @param: distance
# signed distance from the robot to goal.
# can be obtained by path_line.distance_to(ROBOT CURRENT POSITION).
def is_destination_opposite_to_wall(self,distance):
direction = math.copysign(1,distance);
if(self.wall_side == self.LEFT_WALLFOLLOWING()):
if(direction == self.RIGHT_SIDE()):
return True;
else:
return False;
else:
if(direction == self.LEFT_SIDE()):
return True;
else:
return False;
def follow_wall(self, x, y, theta):
"""
This function is called when the state machine enters the wallfollower
state.
"""
# compute and store necessary variables
theta = degrees(theta);
position = Point(x,y);
self.ln_path = Line.from_points([position,self.wp_destination]);
# saving where it started wall following
self.wp_wf_start = position;
def leave_wall(self, x, y, theta):
"""
This function is called when the state machine leaves the wallfollower
state.
"""
# compute and store necessary variables
self.path_started = False;
self.distance_when_left = self.wp_destination.distance_to(Point(x,y));
self.wp_left_wall_at = Point(x,y);
# self.wp_when_left =
pass
def is_goal_unreachable(self, x, y, theta):
"""
This function is regularly called from the wallfollower state to check
the brain's belief about whether the goal is unreachable.
"""
# if the robot goes around an obstacle and
# reaches the starting point and the destenation is still not reached then
# the goal is unreachable.
distance_to_path= self.ln_path.distance_to(Point(x,y));
if(abs(distance_to_path) < self.TOLERANCE()
and Vec2(x,y).almost_equals(self.wp_wf_start)
and self.path_started):
# self.path_started = False;
rospy.logwarn("UNREACHABLE POINT!");
return True
return False
def is_time_to_leave_wall(self, x, y, theta):
"""
This function is regularly called from the wallfollower state to check
the brain's belief about whether it is the right time (or place) to
leave the wall and move straight to the goal.
"""
theta = degrees(theta);
self.current_theta =theta;
self.wp_current_position = Point(x,y);
self.current_direction = Vec2.polar(angle = theta,length = 1);
#Robot Orientation Line.
self.ln_current_orentation = Line(Vec2(x,y),self.current_direction);
# the prependicular line to the path
self.ln_distance = self.ln_path.perpendicular(self.wp_current_position);
distance_to_path= self.ln_path.distance_to(Point(x,y));
self.distance_to_path = distance_to_path;
distance_to_destination = self.ln_current_orentation.distance_to(self.wp_destination);
if(abs(distance_to_path) > 1):
self.path_started =True;
self.distance_to_goal = self.wp_destination.distance_to(Point(x,y));
"""
checking if distance to the straight path is approx. 0 and
if destenation on the opposit side of wall then leave the path
NOTE and TODO: works only for the circles not for complex path.
"""
if(abs(distance_to_path) < self.TOLERANCE() and
self.distance_to_goal < self.distance_when_left and
self.is_destination_opposite_to_wall(distance_to_destination) and
self.path_started): # is robot started following wall!
self.wp_wf_stop = Point(x,y);
return True;
return False
