Inertia

class compas_fab.robots.Inertia

Bases: object

The moments of inertia represent the spatial distribution of mass in a rigid body.

It depends on the mass, size, and shape of a rigid body with units of [mass * m**2]. The moments of inertia can be expressed as the components of a symmetric positive-definite 3x3 matrix, with 3 diagonal elements, and 3 unique off-diagonal elements. Each inertia matrix is defined relative to a coordinate frame or set of axes.

Attributes:

inertia_tensorlist of float

A symmetric positive-definite 3x3 matrix: | ixx ixy ixz | | ixy iyy iyz | | ixz iyz izz | with [ixx, iyy, izz] as the principal moments of inertia and [ixy, ixz, iyz] as the products of inertia.

mass: float

The mass of the object in kg.

center_of_massPoint

The center of mass of the object in meters.

Notes

Assuming uniform mass density, inertial data can be obtained using the free software MeshLab, refering to this great tutorial.

Examples

>>> inertia = Inertia([[0] * 3] * 3, 1.0, Point(0.1, 3.1, 4.4))
>>> inertia
Inertia([[0, 0, 0], [0, 0, 0], [0, 0, 0]], 1.0, Point(x=0.1, y=3.1, z=4.4))
>>> inertia.principal_moments
[0, 0, 0]

Methods

calculate_inertia_tensor

Returns the inertia tensor.