Error using transfer functions

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Shyam 2017-11-7

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https://ww2.mathworks.cn/matlabcentral/answers/365536-error-using-transfer-functions

编辑： Ramu Nair R 2017-12-1

Please help me sort out the issue. I am not understanding why the gain block dimension is shown as 2, where as i am expecting only 1. Please see the attached screenshot of simulink blocks.

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Shyam 2017-11-7

I get these errors, included in attached screenshot.

Shyam 2017-11-7

编辑：Shyam 2017-11-7

Hi, errors are no longer there. I just closed and opened the model. But, as you said, it is running very slow. Any idea, why...? It runs normally if the compensator blocks are not there (2 transfer functions and 1 gain block), which adds to the summer

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Birdman 2017-11-7

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It is normal for simulation to run faster if you substract Transfer functions from the model but the main reason it is slow is that there are too many mathematical calculations to be done and too many states coming up from transfer functions and integrators. The variable-step solver tries to automatically adjust the step size for solving the states but since this model is an electrical system and since naturally electrical systems tends to behave quickly, the solver reduces the step size to almost 1e-4 and this results in simulation to slow. I have some suggestions:

-First, try to find the most suitable sampling time for your model. This means discretizing the continuous blocks in a suitable manner(Transfer Functions and Integrators). Because the variable step solver automatically increases the step size(narrows) in order to give you a solution but this results in slow simulation. I suggest you to look for Bode Plots of Transfer functions and controllers in your model.

-Second, be careful with the potential algebraic loops while discretizing the system.

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Shyam 2017-11-11

Thanks, i figured out the issue.

Birdman 2017-11-11

I was about to solve it, too. Glad you figured that out.

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Shyam 2017-11-30

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https://ww2.mathworks.cn/matlabcentral/answers/365536-error-using-transfer-functions#answer_293909

Another problem involving simple transfer function. I have attached the simulink model and init mfile. I am getting the error regarding singularity in the solution.

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Ramu Nair R 2017-11-30

编辑：Ramu Nair R 2017-12-1

I installed latest version and opened the model. I am trying to use memory blocks instead of delay block. Also, is it necessary to use z domain for transfer function. The block is a part of a bigger system, which are in continuous time, fixed step and solver is Runge-kutta

Ramu Nair R 2017-12-1