How do I fix a signal dimensioning error?

Hello all!

I am currently reworking a DC shunt motor simulation. When trying to execute I get following error message:

Unable to determine signal dimensions. There is a loop consisting of 'DCshuntmotor/Torque equation subsystem/Add' that cannot be resolved because signal dimensions are defined by a cyclic relationship. Specifying the signal dimensions on Inport, Mux, Selector, Demuxes will help resolve signal dimensions in the loop. You can also use the Signal Specifications to define the signal dimensions.

Component:Simulink | Category:Block error

Here are the system + subsystems:

The error message is referring to the latest picture = the torque eqaution sub system. I am assuming that multiplying the multiplexed signals is not compatible with the add block, but I do not know for sure. I have tried to change the operational modus of the multiplying block from piecewise to all matrix and vector options. Nothing fixed the issue, also a signal specifications block after the Mux just caused more dimensional error code.

As the entire system is somewhat looped, the other systems may also not be error free.

Any help is greatly appreciated.

TY in advance!

Answer 1

[Sayan]

Hi @Florian Wernegger,

I understand that your issue is that MATLAB is finding a cyclic relationship between the "Torque equation subsystem" and "Armature equation subsystem" in your model. The most probable solution after looking at screenshots of your model subsystems can be:

• Adding one Signal Specification block (available at Simulink/Signal Attributes) after the Mux blocks of both the "Torque equation subsystem" and "Armature equation subsystem" subsystems in the model.
• Define the required signal dimension in the "Dimensions" field of the block.

Further assistance with the Signal Specification block can be found in the following MATLAB documentation:

https://in.mathworks.com/help/releases/R2020b/simulink/slref/signalspecification.html

Hope this resolves the error in the model.