WOLFRAM SYSTEMMODELER

Position

Forced movement of a flange according to a reference position

Wolfram Language

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SystemModel["Modelica.Mechanics.Translational.Sources.Position"]
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Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

The input signal s_ref defines the reference position in [m]. Flange flange is forced to move relative to the support connector according to this reference motion. According to parameter exact (default = false), this is done in the following way:

  1. exact=true
    The reference position is treated exactly. This is only possible, if the input signal is defined by an analytical function which can be differentiated at least twice. If this prerequisite is fulfilled, the Modelica translator will differentiate the input signal twice in order to compute the reference acceleration of the flange.
  2. exact=false
    The reference position is filtered and the second derivative of the filtered curve is used to compute the reference acceleration of the flange. This second derivative is not computed by numerical differentiation but by an appropriate realization of the filter. For filtering, a second order Bessel filter is used. The critical frequency (also called cut-off frequency) of the filter is defined via parameter f_crit in [Hz]. This value should be selected in such a way that it is higher as the essential low frequencies in the signal.

The input signal can be provided from one of the signal generator blocks of the block library Modelica.Blocks.Sources.

Connectors (3)

flange

Type: Flange_b

Description: Flange of component

support

Type: Support

Description: Support/housing of component

s_ref

Type: RealInput

Description: Reference position of flange as input signal

Parameters (4)

useSupport

Value: false

Type: Boolean

Description: = true, if support flange enabled, otherwise implicitly grounded

exact

Value: false

Type: Boolean

Description: true/false exact treatment/filtering the input signal

f_crit

Value: 50

Type: Frequency (Hz)

Description: if exact=false, critical frequency of filter to filter input signal

w_crit

Value: 2 * Modelica.Constants.pi * f_crit

Type: AngularFrequency (rad/s)

Description: Critical frequency

Used in Examples (3)

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