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Rigid Body

Center of mass (CoM) frame with associated mass and inertia matrix

 

Description

Connections

Parameters

See Also

Description

A Rigid Body component is shown schematically in the diagram below. The ground is assumed to be an inertial reference frame and the motion of the body is tracked relative to the ground frame.  When a new rigid body is created, a reference outboard frame (framea) is created at the center of mass, C, of the body. The inertia matrix is then specified in terms of its moments and products about C, resolved in components along the local x, y, and z axes at C. If the the option to treat the rigid body as a varying point mass is selected, these products and moments are ignored.

To treat the rigid body as a varying point mass, select the Variable point mass parameter. This enables the vMass connection, which allows you to connect a real signal to vMass. The mass of the rigid body will change according to the value of the signal connected to vMass.

Connections

Name

Description

framea

Rigid body center of mass frame

vMass

Variable point mass port

Parameters

Note:  In the descriptions below, inboard frame refers to the implicit global inertial frame and outboard frame refers to the fixed frame of the Rigid Body.

Symbol

Default

Units

Description

Modelica ID

Variable point mass

false

If true, the rigid body is treated as a variable point mass (no rotational inertia)

useVariableMass

m

m

kg

The mass of the rigid body

Mass

I

106000106000106

kgm2

The inertia matrix for the rigid body, expressed in the local center of mass frame

Inertia

Typev

Inboard

-

Indicates whether the initial velocity is expressed in the inboard or outboard frame.

VelType

Typeθ

123

-

Indicates the sequence of body-fixed rotations used to describe the initial orientation of the center of mass frame. For example, 1,2,3 refers to sequential rotations about the x, then y, and then z axis (123 - Euler angles)

RotType

Typeω

Euler

-

Indicates whether the initial angular velocity is expressed in the inboard or outboard frame.  If Euler is selected, the initial angular velocities are assumed to be the direct derivatives of the Euler angles.

AngVelType

ICr,v

Ignore

-

Indicates whether MapleSim ignores, tries to enforce, or strictly enforces the translational initial conditions

MechTranTree

r&conjugate0;0

000

m

Initial displacement of the center of mass frame at the start of the simulation. These values are expressed along the x-, y- and z-axis of the inboard frame respectively

InitPos

v&conjugate0;0

000

ms

Initial velocity of the center of mass frame at the start of the simulation. These values are expressed along the x-, y- and z-axis of the inboard frame respectively

InitVel

ICθ,ω

Ignore

-

Indicates whether MapleSim ignores, tries to enforce, or strictly enforces the rotational initial conditions

MechRotTree

θ&conjugate0;0

000

rad

Initial rotation of the center of mass frame at the start of the simulation, based on the Typeθ parameter values

InitAng

ω&conjugate0;0

000

rads

Initial velocity of the center of mass frame at the start of the simulation, based on the Typeω parameter values

InitAngVel

Use quaternion internally

false

-

Indicates whether the 3-D rotations will be represented as a four parameter quaternion or as three Euler angles.  Regardless of the setting, the initial conditions are specified with Euler angles.

useQuats

See Also

Bodies and Frames

Multibody Overview

Signal Blocks Library Overview