Noise
Created Dienstag 19 Juli 2016
Creates a continuously fluctuating noise signal with either variable or constant mean value and standard deviation
1. Purpose of Block
The block is well suited if reproducible random, normally distributed numbers with low event generation are needed.
2. Limits of Validity / Features
- avoids events
- supports continued simulation
- delayed activation at startTime
- optional smoothing of output to create naturally looking curves instead of step-shaped outputs
3. Interfaces
4. Nomenclature
5. Governing Equations
The output signal follows the step-wise generated random numbers
where the function normalvariate and its core for random number generation, random, are functions from [3] generating reproducible random, normally distributed numbers. Reproducible in this context means that the numbers generated are depending only from the simulation time 
and thus produce the same output at repeated simulations.
6. Remarks for Usage
- from Version 3.2.2 on the Modelica standard library features a package for noise generation: Modelica.Blocks.Noise. See [1] for release notes. These blocks provide noise generators with normal and standard distribution, both in a truncated and non-truncated version. However, ClaRa's noise generator avoids event generation whenever possible which can be advantageous with respect to simulation speed.
- the random number generator used here is taken from [2]. This function and the function nomalvariate are discussed in [3] as a preliminary version for calculating random numbers with Modelica means.
7. Validation
8. References
[1] http://modelica.github.io/Modelica/om/Modelica.UsersGuide.ReleaseNotes.Version_3_2_2.html
[2] https://github.com/modelica/Modelica_LinearSystems2
[3] Peter Fritzson: Principles of Object.Oriented Modeling and Simulation with MODELICA 2.1, John Wiley & Sons, inc., 2004
9. Version History
- 10.11.2011 - Version 0.1 - initial implementation - F.Gottelt, XRG Simulation GmbH
- 07.10.2014 - Version 0.2 - updated nomenclature - F.Gottelt, XRG Simulation GmbH
- 09.05.2016 - Version 0.3 - updated icon - F.Gottelt, XRG Simulation GmbH