Mass management

class mauspaf.core.mauspaf.MassElement(mass, cg=0, id=None, name=None)

Class to describe objects with mass properties.

Simplified class for longitudinal calculations without taking inertia into account.

mass

Mass of the element.

Type:

int or float or uncertain.UncertainValue

cg

x-Position of the center of gravity of the element. Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

id

unique ID to identify the mass element. Relevant for working with tree structures. If not given, a random 8-digit string is used.

Type:

string, optional

name

Name of the mass element.

Type:

string, optional

class mauspaf.core.mauspaf.MassElement3D(mass, x=0, y=0, z=0, ixx=0, iyy=0, izz=0, ixy=0, iyz=0, izx=0, id=None, name=None)

Class to describe objects with mass properties.

Full properties in 3D: mass, cg (x, y, z) and inertias (ixx, iyy, izz, ixy, iyz, izx). For the asymmetric inertias, the convention with a negative factor is used:

\[I_{xy} = - \sum{m_{k} \cdot x_{k} \cdot y_{k}}\]

The moments and products of inertia are given around a coordinate system parallel to the global coordinate system and located on the center of gravity of the object.

mass

Mass of the element.

Type:

int or float or uncertain.UncertainValue

x

x-Position of the center of gravity of the element. Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

y

y-Position of the center of gravity of the element. Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

z

z-Position of the center of gravity of the element. Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

ixx

Inertia of the object around the x-axis (moment of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

iyy

Inertia of the object around the y-axis (moment of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

izz

Inertia of the object around the z-axis (moment of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

ixy

Inertia of the object around the y-axis when the object is rotated around the x-axis (product of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

iyz

Inertia of the object around the z-axis when the object is rotated around the y-axis (product of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

izx

Inertia of the object around the x-axis when the object is rotated around the z-axis (product of inertia). Default value is 0.

Type:

int or float or uncertain.UncertainValue, optional

id

unique ID to identify the mass element. Relevant for working with tree structures. If not given, a random 8-digit string is used.

Type:

string, optional

name

Name of the mass element.

Type:

string, optional

cg_vector()

Returns the cg as an array.

Returns:

[1 x 3] Vector

Return type:

numpy.ndarray

describe()

Prints the mass properties of the element.

inertia_matrix()

Returns the inertial data as a matrix.

Returns:

[3 x 3] Inertia matrix.

Return type:

numpy.ndarray

rotate(axis, angle, point=[0, 0, 0])

Rotates the object around an axis by a given angle.

_images/doc_inertia_rotation_01.svg

This function updates the center of gravity, moments and products of inertia. If you want a new instance with the rotated properties, use a copy (deepcopy) of the object.

Parameters:

  • axis (list or numpy.ndarray) – Vector [1 x 3] describing the rotation axis in the global coordinate system.

  • angle (float) – Rotation angle.

  • point (list or numpy.ndarray or None) – Vector [1 x 3] describing the point the object is rotated around. The default value is the center of gravity of the part.

class mauspaf.core.mauspaf.MassObject3D(estimated=None, calculated=None, measured=None, active='estimated', id=None, name=None)

Class to describe objects with different types of mass properties.

estimated

Estimated properties of the object.

Type:

MassElement3D

calculated

Calculated properties of the object adding the values of all children mass objects.

Type:

MassElement3D

measured

Measured properties of the object.

Type:

MassElement3D

id

unique ID to identify the mass object. Relevant for working with tree structures. If not given, a random 8-digit string is used.

Type:

string, optional

name

Name of the mass object.

Type:

string, optional

active_properties()

Return the currently active properties.

class mauspaf.core.mauspaf.MassObjectTree(elements_list, parent_dict)

Hierarchy between several mass objects (MassObject3D).

elements

dictionary with MassElements. Their IDs are used as a key.

Type:

dict

parent_dict

dictionary ponting to the ID of the parent of each element. The keys used are the IDs of the elements. The root element is not a key in the dictionary.

Type:

dict

update()

Recalculates the mass properties of non-leaf elements.

class mauspaf.core.mauspaf.MassTree(elements, parent_dict)

Hierarchy between several simple mass elements (MassElements).

elements

dictionary with MassElements. Their IDs are used as a key.

Type:

dict

parent_dict

dictionary ponting to the ID of the parent of each element. The keys used are the IDs of the elements. The root element is not a key in the dictionary.

Type:

dict