Why do I have an algebraic loop when I substitute the control block for it's PIL equivalent, even though the simulation runs without this error?

Hi everyone,

I am currently wanting to learn how to do a processor-in-the-loop (PIL) for a 6 phase PMSM in particular and I found this matlab example "ee_six_phase_pmsm_velocity_control", but when I substitute the control block with the PIL equivalent, I have this algebraic loop error. When I run the simulation I don't run into this problem, so I'm confused as to why I have this.

I am using the TI Delfino F28379D , so changes I've made is I've converted the data type from double to single using data conversion blocks because the processor can only handle 32-bit data.

I have attached images and the files that I've used. Any solution or even just an idea that points me in the right direction would be great. I apologize if I missed out any info that should be included as well. Please let me know though. Thank you!

Answer 1

[Karanjot]

Hi Christian,

I understand that you want to resolve an algebraic loop while running a processor-in-the-loop (PIL) for a 6 phase PMSM.

I investigated and found that the non-PIL variant of the control logic resolves the algebraic loop and the PIL variant does not. Hence, the algebraic loop must be removed in the PIL variant.

An algebraic loop occurs when a signal loop in a model contains only blocks that have direct feedthrough. Direct feedthrough refers to blocks that use the input value for the current time step to calculate the output value for the current time step. Feedback loops can create algebraic loops in a model. You can remove these algebraic loops by introducing a delay in the loop using the Unit Delay block.

To learn more about this, you can refer to the below documentation:

Remove Algebraic Loops - MATLAB & Simulink - MathWorks India

In case you require more assistance, you may raise a new request here:

http://www.mathworks.com/support/servicerequests/create.html

I hope this helps!

Regards,

Karanjot Singh