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trasnfer function error usgin ULx library for running a DC motor



I am trying to run a DC motor using Labview's control kit. I want to add a transfer function to the system but once in the loop it gives me an error. The function has an added zero to see changes in the system. It is given by :


H(s)= (1/5s +1) / s


There is no error if the added zero is removed. I am aware that the degree of numerator cannot be greater than that of denominator but this has same degree. It works in Matlab . Labview for some reason does not accept it. Any help would be appreciated. Please do let me know if I am going wrong somewhere.



I am attaching the file and pictures of the block diagram and the error incase you cannot run the file.


Thank You,


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Hi rps,


Are you still having trouble? Adding the zero changes the feedthrough of the Transfer Function from Indirect to Direct. Are you using the error wiring and the Merge Errors to control the execution of your program? The error handling of your program creates a cycle that requires the Transfer Function to have indirect feedthrough. This is explained in the “Wire: is a member of a cycle” Errors with the Simulation Module knowledge base article.


Changing the error handling to avoid the cycle or using a Transfer Function with Indirect Feedthrough should resolve this issue.


I hope that information is helpful!

NI Community Team
National Instruments
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