RelativeStates

Definition of relative state variables

    RelativeStates

Library

Mechanics/Rotational/Components

Description

Usually, the absolute angle and the absolute angular velocity of Modelica.Mechanics.Rotational.Components.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 rotation angle and the relative angular velocity between the two connectors are used as state variables.

An example is given in the next figure

relativeStates

Here, the relative angle and the relative angular velocity between the two inertias are used as state variables. Additionally, the simulator selects either the absolute angle and absolute angular velocity of model inertia1 or of model inertia2 as state variables.

See also the discussion State Selection in the User's Guide of the Rotational library.

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

mo_phi_nominal

phi_nominal

Nominal value of the relative angle (used for scaling)

Scalar

RelativeStates_1

NameLabelDescriptionData TypeValid Values

mo_phi_rel

phi_rel

phi_rel

Structure

mo_phi_rel/fixed

fixed

Cell of scalars

true
false

mo_phi_rel/start

start

Cell of scalars

mo_w_rel

w_rel

w_rel

Structure

mo_w_rel/fixed

fixed

Cell of scalars

true
false

mo_w_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

Flange of left shaft

input

1

flange_b

implicit

Flange of right shaft

output

1