Units of simulink simulations

Question

Saraswathi S 2021-9-8

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评论： Saraswathi S 2021-9-18

I have my dynamical transfer function time constants in minutes. But simulink simulation says its default unit for time is seconds. How can I proceed further.

For sample:

My transfer function: 7/(5s+1). Here 5 is in minutes. And Im designing PID controller for the same. Does the units create any issue in final answers when i run the simulation?

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Answer 1

Tanmay Das 2021-9-16

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Hi,

The default unit for time is seconds in Simulink. You can get a list of all default units from showunitslist command. Transfer function is nothing but the impulse response of a system converted to laplace domain. Here, in this transfer function, 5*60/7 seconds is the time constant according to you but it is 5/7 seconds according to Simulink. So, the response time of the simulink model will be much faster(60 times) as compared to your actual model. Therefore, it is a good practice to change all the units to the default unit before running the simulation.