Main Content

simscape.multibody.MassDistribution class

Package: simscape.multibody
Superclasses: simscape.multibody.Inertia

Construct custom mass distribution

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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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

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

Ixx, Iyy, and Izz 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, Ixx, Iyy, and Izz, 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

(IxxIyyIzz),

where:

  • Ixx=m(y2+z2)dm

  • Iyy=m(x2+z2)dm

  • Izz=m(x2+y2)dm

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

Attributes:

GetAccess
public
SetAccess
public
NonCopyable
true

Iyz, Izx, and Ixy 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, Ixy, Iyz, and Izx 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

(IxyIzxIxyIyzIzxIyz),

where:

  • Iyz=myzdm

  • Izx=mzxdm

  • Ixy=mxydm

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

Attributes:

GetAccess
public
SetAccess
public
NonCopyable
true

Methods

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Version History

Introduced in R2022a