RewardFunctions.py

import numpy as np

"""
Various reward functinos associated with mobile robot navigation
"""


def reward_reachGoalSparse(distance_from_goal, velocity, position_threshold=0.0, reward_value=1.0, velocity_threshold=np.inf):
    """
    Receive a nonzero reward only upon reaching the destination. This is a sparse reward.
    :param distance_from_goal: the distance from the goal in meters
    :param velocity: the velocity (m/s) of the vehicle
    :param position_threshold: the distance around the destination where a nonzero reward exists
    :param reward_value: the maximum reward value that can be achieved (accounting for nontrivial uses of position and velocity thresholds)
    :param velocity_threshold: the velocity (m/s) below which a nonzero reward exists. Used so that a vehicle tries to arrive at a point, not rush through it.
    :return: a scalar representing the reward the learner should receive for the queried state and action
    """
    if distance_from_goal <= position_threshold and velocity < velocity_threshold:
        return reward_value
    return 0


def reward_reachGoalDense(distance_from_goal, position_length_scale=1.0, reward_value=1.0, velocity_length_scale=np.inf):
    """
    Receive a nonzero reward as a function of distance to the destination. This is a dense reward.
    :param distance_from_goal: the distance from the goal in meters
    :param position_length_scale: used to shape the reward surface as a function of position
    :param reward_value: the maximum value that can be achieved
    :param velocity_length_scale: used to shape the reward surface as a function of velocity
    :return:
    """
    return 0


def reward_lineFollowing(distance_from_goal, distance_from_line, distance_from_line_length_scale=1.0, distance_from_destination_length_scale=1.0, velocity_length_scale=np.inf):
    """
    Receive a nonzero reward as a function of distance from a straight line between source and destination. This is a dense reward
    :param distance_from_line:
    :param distance_from_goal:
    :param distance_from_line_length_scale:
    :param distance_from_destination_length_scale:
    :param velocity_length_scale:
    :return:
    """
    return 0