def iter_dE(velocity, latitude, longitude, start_time, end_time, cloudy):
# Time Objects for Kevin's Program
# Arguments should be in this format: "Year Month Day Hour:Min"
# "2011 10 11 14:00"
st = time.strptime(start_time, "%Y %m %d %H:%M")
et = time.strptime(end_time, "%Y %m %d %H:%M")
# Datetime Objects for Wesley's Program
# Arguments should be in this format: "Year Month Day Hour:Min"
# "2011 10 11 14:00"
dST = datetime.strptime(start_time, "%Y %m %d %H:%M")
dET = datetime.strptime(end_time, "%Y %m %d %H:%M")
it = defaultModel.energy_loss_iterator(velocity,
latitude,
longitude,
time.mktime(et)-time.mktime(st))
for (done, losses) in it:
yield (False, -losses)
if done:
break
yield (True, powerGeneration(latitude, velocity, dST, dET, cloudy) - losses)
def iter_V(energy, latitude, longitude, altitude, start_time, end_time, cloudy):
# Start with an arbitrary average velocity... say...50 km/h
velocity_guess = 50.0
# error_bound
error = 0.01
# limit the number of iterations in case newton's method diverges
iteration_limit = 200
current_iteration = 0
dv = 0.01
# Time Objects
st = time.strptime(start_time, "%Y %m %d %H:%M")
et = time.strptime(end_time, "%Y %m %d %H:%M")
dt = time.mktime(et) - time.mktime(st)
# Datetime Objects
dST = datetime.strptime(start_time, "%Y %m %d %H:%M")
dET = datetime.strptime(end_time, "%Y %m %d %H:%M")
start = GPSCoordinate(latitude, longitude, altitude)
# We try to find a velocity such that the energy generated - the energy
# consumed = the specified energy change. In order to do this, we start
# with a guess for the correct velocity and use Newton's method to get
# closer and closer to the correct velocity. Newton's method is a method
# to approximate the root of a function f(x) by starting with a guess of
# the root and repeatedly updating the guess by finding the tangent to f(x)
# at the guess and then finding the intersection of that tangent and the x
# axis. This x-value of this intersection point is the new guess.
while current_iteration < iteration_limit:
energy_gen = powerGeneration(latitude, velocity_guess, dST, dET, cloudy)
energy_loss = powerConsumption(start, velocity_guess, dt)
energy_change = energy_gen - energy_loss
if math.fabs(energy_change - energy) < error:
yield (True, velocity_guess)
print 'answer=',velocity_guess
break
else:
# Update velocity guess value
energy_gen = powerGeneration(latitude, velocity_guess+dv, dST, dET, cloudy)
energy_loss = powerConsumption(start, velocity_guess+dv, dt)
print 'powerGeneration: ', energy_gen
print 'powerConsumption: ', energy_loss
E_prime = ((energy_gen - energy_loss) - energy_change) / dv
velocity_guess = velocity_guess - (energy_change - energy) / E_prime
current_iteration += 1
yield (False, velocity_guess)
if not(math.fabs(energy_change - energy) < error):
# Sometime's Newton's method diverges, so we use a more reliable naive
# method if Newton's fails to converge after the set amount of iterations.
# Reset velocity_guess
velocity_guess = 50.0
# Reset current_iteration
current_iteration = 0
# Change limit
iteration_limit = 1000
# Start with some increment amount
increment_amount = 25.0
# Hold onto our previous guesses just in case...
prev_guess = 0
# We assume that energy generated - energy consumed generally decreases
# when velocity increases. So when the calculated energy change - the
# desired change in energy at the guess velocity is positive, we increase
# the guess velocity to get closer to the correct velocity. On the other
# hand, if the calculated energy change - the desired change in energy at
# the guess velocity is negative, we decrease the guess velocity to get
# closer to the correct velocity. Everytime we change the direction in
# which we increment the guess velocity, we know we have overshot the
# correct velocity, so we half the increment amount to zero in on the
# correct velocity.
while current_iteration < iteration_limit:
energy_gen = powerGeneration(latitude, velocity_guess, dST, dET, cloudy)
energy_loss = powerConsumption(start, velocity_guess, dt)
energy_change = energy_gen - energy_loss
if math.fabs(energy_change-energy) < error:
if velocity_guess < 0:
print "Input energy too high -> velocity ended up negative."
yield (True, velocity_guess)
print 'answer=',velocity_guess
break
elif energy_change-energy > 0:
#check to see if we overshot:
if velocity_guess+increment_amount == prev_guess:
increment_amount = increment_amount/2
prev_guess = velocity_guess
velocity_guess += increment_amount
else:
#check to see if we overshot:
if velocity_guess-increment_amount == prev_guess:
increment_amount = increment_amount/2
prev_guess = velocity_guess
velocity_guess -= increment_amount
current_iteration += 1
yield (False, velocity_guess)
if not(math.fabs(energy_change - energy) < error):
# DOOM
print "Max iterations exceeded. Try different inputs."
yield (True, -1)
# Dummy test functions
##def powerGeneration(latitude, velocity, start_time, end_time, cloudy):
## energy_change = (1-cloudy)*(time.mktime(end_time)-time.mktime(start_time))
## return energy_change
def powerConsumption((latitude, longitude, altitude), velocity, time):
energy_eaten = 0.3*time*velocity
return energy_eaten
# Main Caller and Loop Function
if __name__ == '__main__':
# Previous calculation state:
calcType = 0
energyState = 0
inputVelocity = 0
inputEnergy = 0
endTime = "0:00"
#initialize route database:
load_data()
# User input loop
while True:
# Asks user whether to start a new calculation or modify the previous one
operationType = raw_input("Enter 'n' to start a new calculation. Enter 'm' to modify a previous calculation. ")
if operationType=="n":
# Starting new calculation
calcType=raw_input("Enter 'v' to calculate the average velocity given a change in battery energy. Enter 'e' to calculate change in battery energy given an average velocity. ")
# Calculate velocity given a change in energy
if calcType=="v":
inputEnergy=raw_input("Please enter the desired energy change: ")
longitude=raw_input("Please enter your current longitude coordinate: ")
lat=raw_input("Please enter your current latitude coordinate: ")
alt=raw_input("Please enter your current altitude: ")
startTime=raw_input("Please enter your desired start time. Format: 'year month day hr:min' (24 hr time) If you leave this field blank, 'now' will be the start time. ")
if startTime=="":
print ("Start time defaulted to now")
startTime=time.strftime("%Y %m %d %H:%M",time.localtime())
endTime=raw_input("Please enter your desired end time. Format: 'year month day hr:min' (24 hr time) If you leave this field blank, 17:00 will be the start time. ")
if endTime=="":
print ("End time defaulted to today at 17:00")
# Default endTime will be handled along the way
endTime="17:00"
energyState=raw_input("Please enter the energy level (in MJ) of the batteries at the start location: ")
cloudiness=raw_input("Please enter a projected %cloudy value [0,1]. If you leave this field blank, historical values will be used. ")
if cloudiness=="":
cloudiness=-1
print str(calc_V(float(inputEnergy),float(longitude),float(lat),float(alt),startTime,endTime,float(cloudiness))) + "km/h"
# Calculate change in energy given a velocity
if calcType=="e":
inputVelocity=raw_input("Please enter the desired average velocity: ")
longitude=raw_input("Please enter your current longitude coordinate: ")
lat=raw_input("Please enter your current latitude coordinate: ")
alt=raw_input("Please enter your current altitude: ")
startTime=raw_input("Please enter your desired start time. Format: 'year month day hr:min' (24 hr time) If you leave this field blank, 'now' will be the start time. ")
if startTime=="":
print ("Start time defaulted to now")
startTime=time.strftime("%Y %m %d %H:%M",time.localtime())
endTime=raw_input("Please enter your desired end time. Format: 'hr:min' (24 hr time) If you leave this field blank, 17:00 will be the start time. ")
if endTime=="":
print ("End time defaulted to today at 17:00")
# This'll be handled later
endTime="17:00"
energyState=raw_input("Please enter the energy level (in MJ) of the batteries at the start location: ")
cloudiness=raw_input("Please enter a projected %cloudy value [0,1]. If you leave this field blank, historical values will be used. ")
if cloudiness=="":
cloudiness=-1
print str(calc_dE(float(inputVelocity),float(longitude),float(lat), float(alt), startTime,endTime,float(cloudiness))) + "MJ"
elif operationType == "m" and type!=0:
# Modifying previous calculation
ce = raw_input("Please enter the current energy of the car: ")
currentEnergy = float(ce)
newEnergy = float(inputEnergy) - (currentEnergy - float(energyState))
clouds = raw_input("Please enter a new %cloudy value [0,1]: ")
cloudiness = float(clouds)
newLongitude = raw_input("Please enter a new longitude value: ")
longitude = float(newLongitude)
newLat = raw_input("Please enter a new latitude value: ")
lat = float(newLat)
startTime = time.strftime("%Y %m %d %H:%M", time.localtime())
if type == "v":
# Calculate velocity given a change in energy
print str(calc_V(newEnergy, longitude, lat, startTime, endTime, cloudiness))+ "km/h"
else:
# Calculate change in energy given a velocity
print str(calc_dE(float(inputVelocity), longitude, lat, startTime, endTime, cloudiness) + (currentEnergy - float(energyState))+"MJ")
