# RCAIDE/Library/Methods/Stability/Common/update_moments_of_inertia.py
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# RCAIDE imports
# package imports
import numpy as np
# ----------------------------------------------------------------------------------------------------------------------
# update_moments_of_inertia
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def update_moments_of_inertia(state,vehicle):
"""
Updates the vehicle center of gravity accounting for fuel consumption during flight.
Parameters
----------
vehicle : RCAIDE.Library.Components.Vehicle
Vehicle object containing all components and fuel systems
- networks : list
List of propulsion networks
- fuel_lines : list
List of fuel lines within each network
- fuel_tanks : list
List of fuel tanks within each fuel line
- fuel : RCAIDE.Library.Components.Energy.Storages.Fuel
Fuel component with mass properties
- mass_properties : Data
- mass : float
Current fuel mass [kg]
- center_of_gravity : list
Fuel tank center of gravity [m]
- origin : list
Fuel tank origin location [m]
conditions : RCAIDE.Framework.Core.Data
Flight conditions and state data
- aerodynamics : Data
- weights : Data
Returns
-------
CG : numpy.ndarray
Updated moment of intertia tensor variables
Shape: (1, N) where N is the number of flight conditions
Notes
-----
This function calculates the moment of inertia of the vehicle by
accounting for fuel consumption during flight.
**Major Assumptions**
* Fuel tank locations and orientations remain constant
* No fuel sloshing or redistribution effects
* Vehicle structure mass remains constant
* Fuel density is constant
"""
# unoack
conditions = state.conditions
N = state.numerics.number_of_control_points
for network in vehicle.networks:
for fuel_line in network.fuel_lines:
for fuel_tank in fuel_line.fuel_tanks:
update_fuel_tank_moment_of_inertia(fuel_tank,state)
# --------------------------------------------------------------------------
# update aircraft MOI
# --------------------------------------------------------------------------
MOI_Ixx = np.zeros((N,1))
MOI_Ixy = np.zeros((N,1))
MOI_Ixz = np.zeros((N,1))
MOI_Iyx = np.zeros((N,1))
MOI_Iyy = np.zeros((N,1))
MOI_Iyz = np.zeros((N,1))
MOI_Izx = np.zeros((N,1))
MOI_Izy = np.zeros((N,1))
MOI_Izz = np.zeros((N,1))
for item in conditions.weights.components.mass.keys():
MOI_Ixx += conditions.weights.components.moments_of_inertia_Ixx[item]
MOI_Ixy += conditions.weights.components.moments_of_inertia_Ixy[item]
MOI_Ixz += conditions.weights.components.moments_of_inertia_Ixz[item]
MOI_Iyx += conditions.weights.components.moments_of_inertia_Iyx[item]
MOI_Iyy += conditions.weights.components.moments_of_inertia_Iyy[item]
MOI_Iyz += conditions.weights.components.moments_of_inertia_Iyz[item]
MOI_Izx += conditions.weights.components.moments_of_inertia_Izx[item]
MOI_Izy += conditions.weights.components.moments_of_inertia_Izy[item]
MOI_Izz += conditions.weights.components.moments_of_inertia_Izz[item]
conditions.weights.vehicle.moments_of_inertia_Ixx = MOI_Ixx
conditions.weights.vehicle.moments_of_inertia_Ixy = MOI_Ixy
conditions.weights.vehicle.moments_of_inertia_Ixz = MOI_Ixz
conditions.weights.vehicle.moments_of_inertia_Iyx = MOI_Iyx
conditions.weights.vehicle.moments_of_inertia_Iyy = MOI_Iyy
conditions.weights.vehicle.moments_of_inertia_Iyz = MOI_Iyz
conditions.weights.vehicle.moments_of_inertia_Izx = MOI_Izx
conditions.weights.vehicle.moments_of_inertia_Izy = MOI_Izy
conditions.weights.vehicle.moments_of_inertia_Izz = MOI_Izz
return
[docs]
def update_fuel_tank_moment_of_inertia(fuel_tank,state):
conditions = state.conditions
N = state.numerics.number_of_control_points
center_of_gravity = conditions.weights.vehicle.global_center_of_gravity
fuel_tag = fuel_tank.fuel.tag
# mass of fuel
M_fuel = conditions.weights.components.mass[fuel_tag]
# local non-dimensional tensor
MOI_fuel_non_dim = fuel_tank.fuel.mass_properties.moments_of_inertia.non_dimensional_tensor
# local dimensional tensor
I_fuel_local = M_fuel[:,:, None] * np.array(MOI_fuel_non_dim)[None,:,:]
# moment arm
s = np.array(center_of_gravity) - conditions.weights.components.global_center_of_gravity[fuel_tag]
term_1 = np.repeat(np.repeat(np.vecdot(s, s)[:,None, None],3, axis=2), 3, axis=1)
term_2 = np.repeat(np.array(np.identity(3))[None,:,:],N, axis=0)
term_3 = np.multiply.outer(s, s)[:, :, 0, :]
# parallel axis moment
I_fuel_par = M_fuel[:,:, None] * (term_1* term_2 - term_3 )
# total moment of inertia
I_fuel = I_fuel_local + I_fuel_par
# update data structures
conditions.weights.components.moments_of_inertia_Ixx[fuel_tag][:,0] = I_fuel[:,0,0]
conditions.weights.components.moments_of_inertia_Ixy[fuel_tag][:,0] = I_fuel[:,0,1]
conditions.weights.components.moments_of_inertia_Ixz[fuel_tag][:,0] = I_fuel[:,0,2]
conditions.weights.components.moments_of_inertia_Iyx[fuel_tag][:,0] = I_fuel[:,1,0]
conditions.weights.components.moments_of_inertia_Iyy[fuel_tag][:,0] = I_fuel[:,1,1]
conditions.weights.components.moments_of_inertia_Iyz[fuel_tag][:,0] = I_fuel[:,1,2]
conditions.weights.components.moments_of_inertia_Izx[fuel_tag][:,0] = I_fuel[:,2,0]
conditions.weights.components.moments_of_inertia_Izy[fuel_tag][:,0] = I_fuel[:,2,1]
conditions.weights.components.moments_of_inertia_Izz[fuel_tag][:,0] = I_fuel[:,2,2]
return
