Force Noise Source

R2026b

Model zero-mean normally (Gaussian) distributed force

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Force Noise Source block

To add a block to a model, double-click the canvas and start typing the block name. Then, select the block from the list.

Libraries:
Simscape / Driveline / Sources

Description

The Force Noise Source block generates zero-mean normally (Gaussian) distributed force using the PS Random Number source in the Simscape™ Foundation library. The force produced by the block depends on two factors:

• The noise power spectral density input to the block

• A random number seed that you control using the Repeatability and, as applicable, Seed parameters

The defining equation for the force that the block generates is

$$F=\sqrt{PSD/2}\frac{N\left(0,1\right)}{\sqrt{h}},$$

where:

• F is the output force.

• PSD is the single-sided noise power spectral density.

• N is a Gaussian random number with zero mean and standard deviation of one.

• h is the sampling interval.

Ports

Input

P — Single-sided noise power spectral density

physical signal

The power spectral density (PSD) of noise is the average noise power per unit of bandwidth, in N²/Hz.

Programmatic Use

Port: PSD

Conserving

B — Base interface

mechanical translational

Mechanical translational conserving port associated with the base interface.

Programmatic Use

Port: B

F — Follower interface

mechanical translational

Mechanical translational conserving port associated with the follower interface.

Programmatic Use

Port: F

Parameters

Sample time — Time step period and offset

1e-3 s (default) | [step, offset] s

The values of the time step period and the initial time offset. If you specify a scalar value for step, the block assumes an offset value of 0.To specify a nonzero value for the initial time offset, specify the parameter values using the vector [step, offset]. The offset value must be less than the step value and greater than or equal to zero.

Programmatic Use

Parameter: sample_time

Repeatability — Random number seed control

Not repeatable (default) | Repeatable | Specify seed

The random number seed is the number that initializes the random number generator. The seed is 0 or a positive integer. To control the random number seed, set this parameter to:

• Not repeatable — The seed changes every time you simulate your model. The block resets the random seed using the MATLAB^® random number generator command:

  seed = randi(2^32-1);

• Repeatable — The seed is the same random number at the start of every simulation. The block sets the value using the same MATLAB random number generator command used by the Not repeatable parameter.

  When you add a Force Noise Source block to your model from the Sources library, the block generates and stores a random value for the repeated seed. When you make a copy of the Force Noise Source block from an existing block in a model, the copy generates a new random value for the repeated seed.

• Specify seed — The seed is a number that you specify using the Seed parameter. The Seed parameter is only available when you choose Specify seed for the Repeatability parameter.

Programmatic Use

Parameter:	repeatability
Values:	"sdl.enum.seedInitialization.NotRepeatable" | "sdl.enum.seedInitialization.Repeatable" | "sdl.enum.seedInitialization.SpecifySeed"

Seed — Random number generation seed value

0 (default)

The seed must be 0 or a positive integer. This parameter is only available when you select Specify seed for the Repeatability parameter.

Programmatic Use

Parameter: user_seed

Auto-generated seed used for repeatable option — Auto-generated seed for repeatable noise

-1 (default) | scalar

Seed value that the block auto-generates when Repeatability is set to Repeatable. This value ensures the noise sequence is the same each time you simulate.

Dependencies

To enable this parameter, set Repeatability to Repeatable.

Programmatic Use

Parameter: auto_seed

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"sdl_lib/Sources/Force Noise Source"

Example: add_block("sdl_lib/Sources/Force Noise Source","myModel/myBlock",MakeNameUnique="on")

For information about programmatic access to individual block parameters, see the Programmatic Use section of parameter descriptions on this page.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2016b