Source code for RCAIDE.Library.Methods.Mass_Properties.Center_of_Gravity.update_center_of_gravity
# RCAIDE/Library/Methods/Stability/Common/update_center_of_gravity.py
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# IMPORT
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# RCAIDE imports
# package imports
import numpy as np
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# update_center_of_gravity
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[docs]
def update_center_of_gravity(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 center of gravity coordinates [m]
Shape: (3, N) where N is the number of flight conditions
Notes
-----
This function calculates the updated center of gravity of the vehicle by
accounting for fuel consumption during flight. It computes the mass and
moment contributions of remaining fuel and combines them with the dry
vehicle mass and moment to determine the new center of gravity location.
**Major Assumptions**
* Fuel tank locations and orientations remain constant
* No fuel sloshing or redistribution effects
* Vehicle structure mass remains constant
* Fuel density is constant
**Theory**
The center of gravity is calculated using the principle of moments:
:math:`\\vec{r}_{CG} = \\frac{\\sum m_i \\vec{r}_i}{\\sum m_i}`
where :math:`m_i` is the mass of component :math:`i` and :math:`\\vec{r}_i` is its position.
**Definitions**
'Center of Gravity'
Point where the total mass of the vehicle can be considered to act.
"""
# unpack
conditions = state.conditions
N = state.numerics.number_of_control_points
# --------------------------------------------------------------------------
# update center of gravity
# --------------------------------------------------------------------------
Mom_tot = np.zeros((N,3))
Mass_tot = np.zeros((N,1))
for item in conditions.weights.components.mass.keys():
mass = conditions.weights.components.mass[item]
CG = conditions.weights.components.global_center_of_gravity[item]
sym = conditions.weights.components.symmetry_flag[item]
Mass_tot += conditions.weights.components.mass[item]
Mom_tot += CG*sym * mass
state.conditions.weights.vehicle.global_center_of_gravity = Mom_tot / Mass_tot
return
