RelativeStates

Definition of relative state variables

    RelativeStates

Library

Mechanics/Translational/Components

Description

Usually, the absolute position and the absolute velocity of Modelica.Mechanics.Translational.Inertia models are used as state variables. In some circumstances, relative quantities are better suited, e.g., because it may be easier to supply initial values. In such cases, model RelativeStates allows the definition of state variables in the following way:

  • Connect an instance of this model between two flange connectors.
  • The relative position and the relative velocity between the two connectors are used as state variables.

An example is given in the next figure

relativeStates2

Here, the relative position and the relative velocity between the two masses are used as state variables. Additionally, the simulator selects either the absolute position and absolute velocity of model mass1 or of model mass2 as state variables.

Parameters

RelativeStates_0

NameLabelDescriptionData TypeValid Values

mo_stateSelect

stateSelect

Priority to use the relative angle and relative speed 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

RelativeStates_1

NameLabelDescriptionData TypeValid Values

mo_s_rel

s_rel

s_rel

Structure

mo_s_rel/fixed

fixed

Cell of scalars

true
false

mo_s_rel/start

start

Cell of scalars

mo_v_rel

v_rel

v_rel

Structure

mo_v_rel/fixed

fixed

Cell of scalars

true
false

mo_v_rel/start

start

Cell of scalars

mo_a_rel

a_rel

a_rel

Structure

mo_a_rel/fixed

fixed

Cell of scalars

true
false

mo_a_rel/start

start

Cell of scalars

Ports

NameTypeDescriptionIO TypeNumber

flange_a

implicit

(left) driving flange (flange axis directed in to cut plane, e. g. from left to right)

input

1

flange_b

implicit

(right) driven flange (flange axis directed out of cut plane)

output

1