simscape.multibody.MassDistribution Class

Namespace: simscape.multibody
Superclasses: simscape.multibody.Inertia

Construct custom mass distribution

Since R2022a

Description

Use an object of the simscape.multibody.MassDistribution class to construct a custom mass distribution that explicitly specifies the mass, center of mass, moments of inertia, and products of inertia. The mass distribution has an implicit reference frame. If you use a simscape.multibody.MassDistribution object to specify the mass distribution of a solid, the implicit reference frame is coincident with the reference frame of the solid.

Class Attributes

`Sealed`	`true`
`ConstructOnLoad`	`true`
`RestrictsSubclassing`	`true`

For information on class attributes, see Class Attributes.

Creation

Description

mdmass = simscape.multibody.Massdistribution constructs a custom mass distribution using default values.

mdmass = simscape.multibody.Massdistribution(mass) constructs a custom mass distribution and sets the total mass to mass.

mdmass = simscape.multibody.Massdistribution(mass,com) constructs a custom mass distribution and also sets the specified center of mass to com.

mdmass = simscape.multibody.Massdistribution(mass,com,moi) constructs a custom mass distribution and also sets the moments of inertia to moi.

mdmass = simscape.multibody.Massdistribution(mass,com,moi,poi) constructs a custom mass distribution and also sets the products of inertia to poi.

Properties

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`Mass` — Total mass
`simscape.Value(1,"kg")` (default) | `simscape.Value(M,"Mass unit")`

Total mass, specified as a simscape.Value object that represents a scalar with a unit of mass. The scalar can be positive or negative. Use a negative value to capture the effect of a void or cavity in a compound body that comprises multiple solids. The total mass of the compound body must be positive.

Example: simscape.Value(16,"lbm")

Attributes:

`GetAccess`	`public`
`SetAccess`	`public`
`NonCopyable`	`true`

`CenterOfMass` — Center-of-mass coordinates
`simscape.Value([0 0 0]',"m")` (default) | `simscape.Value([x y z],"Length unit")` | `simscape.Value([x y z]',"Length unit")`

Center-of-mass coordinates, specified as a simscape.Value object that represents a 3-by-1 or 1-by-3 array with a unit of length. The coordinates are resolved in the implicit reference frame of the mass distribution.

Example: simscape.Value([0 0 5],"mm")

Attributes:

`GetAccess`	`public`
`SetAccess`	`public`
`NonCopyable`	`true`

`MomentsOfInertia` — Diagonal elements of inertia matrix
`simscape.Value([0 0 0]',"kgm^2")` (default) | `simscape.Value([`I_xx I_yy I_zz`],"masslength^2")` | `simscape.Value([`I_xx I_yy I_zz`]',"mass*length^2")`

I_xx, I_yy, and I_zz elements of the inertia matrix, specified as a simscape.Value object that represents a 3-by-1 or 1-by-3 array with a unit of mass*length^2.

The quantities, I_xx, I_yy, and I_zz, are the moments of inertia with respect to the axes of a frame whose origin is coincident with the center of mass and whose axes are parallel to the implicit reference frame. The moments of inertia are the diagonal elements of the inertia matrix

$(\begin{matrix} I_{x x} \\ I_{y y} \\ I_{z z} \end{matrix}),$

where:

$I_{x x} = \int_{m} (y^{2} + z^{2}) d m$
$I_{y y} = \int_{m} (x^{2} + z^{2}) d m$
$I_{z z} = \int_{m} (x^{2} + y^{2}) d m$

Example: simscape.Value([12 15 10],"kg*cm^2")

Attributes:

`GetAccess`	`public`
`SetAccess`	`public`
`NonCopyable`	`true`

`ProductsOfInertia` — Off-diagonal elements of inertia matrix
`simscape.Value([0 0 0]',"kgm^2")` (default) | `simscape.Value([`I_yz I_zx I_xy`],"masslength^2")` | `simscape.Value([`I_yz I_zx I_xy`]',"mass*length^2")`

I_yz, I_zx, and I_xy elements of the inertia matrix, specified as a simscape.Value object that represents a 3-by-1 or 1-by-3 array with a unit of mass*length^2.

The quantities, I_xy, I_yz, and I_zx are the products of inertia with respect to the axes of a frame whose origin is coincident with the center of mass and whose axes are parallel to the implicit reference frame. The products of inertia are the off-diagonal elements of the inertia matrix

$(\begin{matrix} I_{x y} & I_{z x} \\ I_{x y} & I_{y z} \\ I_{z x} & I_{y z} \end{matrix}),$

where:

$I_{y z} = - \int_{m} y z d m$
$I_{z x} = - \int_{m} z x d m$
$I_{x y} = - \int_{m} x y d m$

Example: simscape.Value([-2 3 1],"kg*cm^2")

Attributes:

`GetAccess`	`public`
`SetAccess`	`public`
`NonCopyable`	`true`

Methods

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Public Methods

`inertiaMatrix`	Compute inertia matrix
`principalMomentsOfInertia`	Compute principal moments of inertia
`principalToReferenceTransformation`	Compute 3-D rigid transformation between principal and reference frames
`transform`	Transform inertia to different frame

Version History

Introduced in R2022a

simscape.multibody.MassDistribution Class

Description

Class Attributes

Creation

Description

Properties

Mass — Total mass simscape.Value(1,"kg") (default) | simscape.Value(M,"Mass unit")

Attributes:

CenterOfMass — Center-of-mass coordinates simscape.Value([0 0 0]',"m") (default) | simscape.Value([x y z],"Length unit") | simscape.Value([x y z]',"Length unit")

Attributes:

MomentsOfInertia — Diagonal elements of inertia matrix simscape.Value([0 0 0]',"kg*m^2") (default) | simscape.Value([Ixx Iyy Izz],"mass*length^2") | simscape.Value([Ixx Iyy Izz]',"mass*length^2")

Attributes:

ProductsOfInertia — Off-diagonal elements of inertia matrix simscape.Value([0 0 0]',"kg*m^2") (default) | simscape.Value([Iyz Izx Ixy],"mass*length^2") | simscape.Value([Iyz Izx Ixy]',"mass*length^2")

Attributes:

Methods

Public Methods

Version History

See Also

`Mass` — Total mass
`simscape.Value(1,"kg")` (default) | `simscape.Value(M,"Mass unit")`

`CenterOfMass` — Center-of-mass coordinates
`simscape.Value([0 0 0]',"m")` (default) | `simscape.Value([x y z],"Length unit")` | `simscape.Value([x y z]',"Length unit")`

`MomentsOfInertia` — Diagonal elements of inertia matrix
`simscape.Value([0 0 0]',"kgm^2")` (default) | `simscape.Value([`I_xx I_yy I_zz`],"masslength^2")` | `simscape.Value([`I_xx I_yy I_zz`]',"mass*length^2")`

`ProductsOfInertia` — Off-diagonal elements of inertia matrix
`simscape.Value([0 0 0]',"kgm^2")` (default) | `simscape.Value([`I_yz I_zx I_xy`],"masslength^2")` | `simscape.Value([`I_yz I_zx I_xy`]',"mass*length^2")`