Guy and Seth on Simulink

May 14th, 2012

How to Load and Save Bus Signal Data

In R2012a, the From Workspace, To Workspace, From File and To File blocks all support bus signals. This is an often requested capability, and I have been looking forward to it for a long time.

MATLAB Timeseries

In R2012a, most methods for importing and exporting data to and from a model have been standardized to use MATLAB Timeseries.

For example, if you open the dialog of the To Workspace, you will see that timeseries is now the default save format:

save formats for the To Workspace block

Using MATLAB timeseries offers a lot of advantages as I described in a previous post on the dataset logging format.

Importing Bus Data

Let's say I want to import bus data, I create a structure of timeseries:

Creating bus data

Then I specify the name of the variable or file, and the bus object in the From Workspace or From File dialog.

Configuring the From Workspace block to import bus data

and we have a model importing buses!

Model importing bus data

Exporting Bus data

To export bus data, all you need to do do is connect the bus signal to a To Workspace or To File block and ensure the block is configured to use timeseries as save format (the default).

Once the data is in the MATLAB Workspace, you can use all timeseries methods to process your data.

For example, I can quickly detrend, filter and plot a random signal "b", contained inside bus "busOut":

processing bus data using MATLAB timeseries

Processed data

Now its your turn

Are you going to include these new methods of loading and saving bus data in your workflow? Which is be best block pair for loading/saving buses? Let us know by leaving a comment here

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By Guy Rouleau

20:48 UTC | Posted in Signals, What's new? | Permalink | 7 Comments »

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7 Responses to “How to Load and Save Bus Signal Data”

  1. KE replied on May 15th, 2012 at 12:40 UTC :

    FYI to beginners like me: a bus is a composite signal that bundles together several time series which can have *different* data types, unlike a mux which composites time series with the *same* data type, see , http://blogs.mathworks.com/seth/2008/03/27/what-is-a-composite-signal/ . In earlier versions of Matlab, you could only pass a mux to the ToWorkspace block, but now you can pass a bus as well. [Let me know if I have misunderstood].

  2. Guy Rouleau replied on May 15th, 2012 at 13:08 UTC :

    Thank you KE for the precision.

    For those more familiar with the MATLAB language, a bus is like a structure. A mux, is like an array or a vector.

    One important thing to keep in mind is that, for backward compatibility, Simulink allows you to mix buses and muxes. However it is recommend to avoid that.

    See the documentation section titled “Avoiding Mux/Bus Mixtures” for more details:

    http://www.mathworks.com/help/toolbox/simulink/ug/bq4jp6i.html

  3. St replied on May 29th, 2012 at 08:30 UTC :

    How is bus different from mux? Kindly explain in terms of begineers language…thanks

  4. Kyle Andringa replied on November 19th, 2012 at 16:41 UTC :

    Guy & Seth,

    I’m glad to see this capability coming along, however it doesn’t quite satisfy what I am looking for yet. Here’s my issue and how I’m getting around it.

    I have a large simulation which uses buses to enforce interfaces and reduce the complexity of block connection. I like the idea of using the TimeSeries type to be able to output an entire bus. However, TimeSeries types are not compatible with Rapid Accelerator, which is a critical need for my sim given that we run thousands of Monte Carlo simulations with ParFor. The only solution I have to this is to break out every variable from the bus into it’s own ToWorkspace block and specify the Type as Array. This can be a real mess to do and doesn’t allow any structured naming.

    Do you have any recommendations on capturing simulation data for models with Buses, while still being compatible with rapid accelerator?

    Thanks,
    Kyle

  5. Guy Rouleau replied on November 20th, 2012 at 09:39 UTC :

    @Kyle: Since R2012a, the To File block can be used to log buses in Rapid Accelerator mode. It saves a structure of time series like in normal mode.

  6. Jason S replied on February 20th, 2013 at 15:25 UTC :

    Oh, so close.

    I want to set up a From Workspace block. You mention all the details of how to do this above… except that the picture of the From Workspace dialog in this blog entry shows “Data: myBus” and “Output Data Type: Bus: busObj”.

    What is “busObj”?

  7. Guy Rouleau replied on February 21st, 2013 at 09:02 UTC :

    @Jason: busObj is a bus object. Depending on how your bus is created, you sometimes need a bus object to declare to the Simulink engine what the bus look like.

    You can find more information on this topic here:

    http://www.mathworks.com/help/simulink/ug/using-bus-objects.html

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Guy Rouleau and Seth Popinchalk are Application Engineers for MathWorks. They write here about Simulink and other MathWorks tools used in Model-Based Design.

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