Add MPG reward (#931)

Add an MPG reward

flow/core/kernel/vehicle/base.py

@@ -297,6 +297,20 @@ def get_num_not_departed(self):
         """
         raise NotImplementedError
 
+    def get_fuel_consumption(selfself, veh_id, error=-1001):
+        """Return the mpg / s of the specified vehicle.
+
+        Parameters
+        ----------
+        veh_id : str or list of str
+            vehicle id, or list of vehicle ids
+        error : any, optional
+            value that is returned if the vehicle is not found
+        Returns
+        -------
+        float
+        """
+
     def get_speed(self, veh_id, error=-1001):
         """Return the speed of the specified vehicle.
 

flow/core/kernel/vehicle/traci.py

@@ -335,7 +335,8 @@ def _add_departed(self, veh_id, veh_type):
             tc.VAR_EDGES,
             tc.VAR_POSITION,
             tc.VAR_ANGLE,
-            tc.VAR_SPEED_WITHOUT_TRACI
+            tc.VAR_SPEED_WITHOUT_TRACI,
+            tc.VAR_FUELCONSUMPTION
         ])
         self.kernel_api.vehicle.subscribeLeader(veh_id, 2000)
 
@@ -370,6 +371,8 @@ def _add_departed(self, veh_id, veh_type):
             self.kernel_api.vehicle.getLaneIndex(veh_id)
         self.__sumo_obs[veh_id][tc.VAR_SPEED] = \
             self.kernel_api.vehicle.getSpeed(veh_id)
+        self.__sumo_obs[veh_id][tc.VAR_FUELCONSUMPTION] = \
+            self.kernel_api.vehicle.getFuelConsumption(veh_id)
 
         # make sure that the order of rl_ids is kept sorted
         self.__rl_ids.sort()
@@ -533,6 +536,13 @@ def get_num_not_departed(self):
         """See parent class."""
         return self.num_not_departed
 
+    def get_fuel_consumption(self, veh_id, error=-1001):
+        """Return fuel consumption in gallons/s."""
+        ml_to_gallons = 0.000264172
+        if isinstance(veh_id, (list, np.ndarray)):
+            return [self.get_fuel_consumption(vehID, error) for vehID in veh_id]
+        return self.__sumo_obs.get(veh_id, {}).get(tc.VAR_FUELCONSUMPTION, error) * ml_to_gallons
+
     def get_previous_speed(self, veh_id, error=-1001):
         """See parent class."""
         if isinstance(veh_id, (list, np.ndarray)):

flow/core/rewards.py

@@ -330,3 +330,109 @@ def energy_consumption(env, gain=.001):
         power += M * speed * accel + M * g * Cr * speed + 0.5 * rho * A * Ca * speed ** 3
 
     return -gain * power
+
+
+def veh_energy_consumption(env, veh_id, gain=.001):
+    """Calculate power consumption of a vehicle.
+
+    Assumes vehicle is an average sized vehicle.
+    The power calculated here is the lower bound of the actual power consumed
+    by a vehicle.
+    """
+    power = 0
+
+    M = 1200  # mass of average sized vehicle (kg)
+    g = 9.81  # gravitational acceleration (m/s^2)
+    Cr = 0.005  # rolling resistance coefficient
+    Ca = 0.3  # aerodynamic drag coefficient
+    rho = 1.225  # air density (kg/m^3)
+    A = 2.6  # vehicle cross sectional area (m^2)
+    speed = env.k.vehicle.get_speed(veh_id)
+    prev_speed = env.k.vehicle.get_previous_speed(veh_id)
+
+    accel = abs(speed - prev_speed) / env.sim_step
+
+    power += M * speed * accel + M * g * Cr * speed + 0.5 * rho * A * Ca * speed ** 3
+
+    return -gain * power
+
+
+def miles_per_megajoule(env, veh_ids=None, gain=.001):
+    """Calculate miles per mega-joule of either a particular vehicle or the total average of all the vehicles.
+
+    Assumes vehicle is an average sized vehicle.
+    The power calculated here is the lower bound of the actual power consumed
+    by a vehicle.
+
+    Parameters
+    ----------
+    env : flow.envs.Env
+        the environment variable, which contains information on the current
+        state of the system.
+    veh_ids : [list]
+        list of veh_ids to compute the reward over
+    gain : float
+        scaling factor for the reward
+    """
+    mpj = 0
+    counter = 0
+    if veh_ids is None:
+        veh_ids = env.k.vehicle.get_ids()
+    elif not isinstance(veh_ids, list):
+        veh_ids = [veh_ids]
+    for veh_id in veh_ids:
+        speed = env.k.vehicle.get_speed(veh_id)
+        # convert to be positive since the function called is a penalty
+        power = -veh_energy_consumption(env, veh_id, gain=1.0)
+        if power > 0 and speed >= 0.0:
+            counter += 1
+            # meters / joule is (v * \delta t) / (power * \delta t)
+            mpj += speed / power
+    if counter > 0:
+        mpj /= counter
+
+    # convert from meters per joule to miles per joule
+    mpj /= 1609.0
+    # convert from miles per joule to miles per megajoule
+    mpj *= 10**6
+
+    return mpj * gain
+
+
+def miles_per_gallon(env, veh_ids=None, gain=.001):
+    """Calculate mpg of either a particular vehicle or the total average of all the vehicles.
+
+    Assumes vehicle is an average sized vehicle.
+    The power calculated here is the lower bound of the actual power consumed
+    by a vehicle.
+
+    Parameters
+    ----------
+    env : flow.envs.Env
+        the environment variable, which contains information on the current
+        state of the system.
+    veh_ids : [list]
+        list of veh_ids to compute the reward over
+    gain : float
+        scaling factor for the reward
+    """
+    mpg = 0
+    counter = 0
+    if veh_ids is None:
+        veh_ids = env.k.vehicle.get_ids()
+    elif not isinstance(veh_ids, list):
+        veh_ids = [veh_ids]
+    for veh_id in veh_ids:
+        speed = env.k.vehicle.get_speed(veh_id)
+        gallons_per_s = env.k.vehicle.get_fuel_consumption(veh_id)
+        if gallons_per_s > 0 and speed >= 0.0:
+            counter += 1
+            # meters / gallon is (v * \delta t) / (gallons_per_s * \delta t)
+            mpg += speed / gallons_per_s
+    if counter > 0:
+        mpg /= counter
+
+    # convert from meters per gallon to miles per gallon
+    mpg /= 1609.0
+
+    return mpg * gain