VariablePointMass

Rigid body with variable mass where body rotation and inertia tensor is neglected (6 potential states)

    VariablePointMass

Library

ModelicaExtras/Mechanics/MultiBody

Description

Rigid body where the inertia tensor is neglected. This body is solely defined by its mass. By default, this component is visualized by a sphere that has its center at frame_a. Note, that the animation may be switched off via parameter animation = false.

Every PointMass has potential states. If possible a tool will select the states of joints and not the states of PointMass because this is usually the most efficient choice. In this case the position and velocity of frame_a of the body will be computed by the component that is connected to frame_a. However, if a PointMass is moving freely in space, variables of the PointMass have to be used as states. The potential states are: The position vector frame_a.r_0 from the origin of the world frame to the origin of frame_a of the body, resolved in the world frame and the absolute velocity v_0 of the origin of frame_a, resolved in the world frame (= der(frame_a.r_0)).

Whether or not variables of the body are used as states is usually automatically selected by the Modelica translator. If parameter enforceStates is set to true in the "Advanced" menu, then PointMass variables frame_a.r_0 and der(frame_a.r_0) are forced to be used as states.

Parameters

VariablePointMass_0

NameLabelDescriptionData TypeValid Values

mo_animation

animation

= true, if animation shall be enabled (show sphere)

Scalar

true
false

mo_r_0

r_0

r_0

Structure

mo_r_0/fixed

fixed

Cell of vectors of size 3

true
false

mo_r_0/start

start

Cell of vectors of size 3

mo_v_0

v_0

v_0

Structure

mo_v_0/fixed

fixed

Cell of vectors of size 3

true
false

mo_v_0/start

start

Cell of vectors of size 3

mo_a_0

a_0

a_0

Structure

mo_a_0/fixed

fixed

Cell of vectors of size 3

true
false

mo_a_0/start

start

Cell of vectors of size 3

VariablePointMass_1

NameLabelDescriptionData TypeValid Values

mo_sphereDiameter

sphereDiameter

Diameter of sphere

Scalar

mo_sphereColor

sphereColor

Color of sphere

Vector of size 3

mo_specularCoefficient

specularCoefficient

Reflection of ambient light (= 0: light is completely absorbed)

Scalar

VariablePointMass_2

NameLabelDescriptionData TypeValid Values

mo_stateSelect

stateSelect

Priority to use frame_a.r_0, v_0 (= der(frame_a.r_0)) as states

Structure

mo_stateSelect/choice1

StateSelect.never

Number

0
1

mo_stateSelect/choice2

StateSelect.avoid

Number

0
1

mo_stateSelect/choice3

StateSelect.default

Number

0
1

mo_stateSelect/choice4

StateSelect.prefer

Number

0
1

mo_stateSelect/choice5

StateSelect.always

Number

0
1

VariablePointMass_3

NameLabelDescriptionData TypeValid Values

mo__nmodifiers

Number of Modifiers

Specifies the number of modifiers

Number

mo__modifiers

Modifiers

Add new modifier

Structure

mo__modifiers/varname

Variable name

Cell of strings

mo__modifiers/attribute

Attribute

Cell of strings

'start'
'fixed'

mo__modifiers/value

Value

Ports

NameTypeDescriptionIO TypeNumber

frame_a

implicit

Coordinate system fixed at center of mass point

input

1

m

implicit

Variable mass of the rigid body

input

2

See Also