How to give Initial Condition to Transfer Function

Hello All,

I want the graph to start at 5 after it leaves the transfer function block in Simulink.

However, it starts at zero as default.

I have tried to use the Transfer Fcn with initial inputs but did not succeed -the output osciallates between 5 and -5.

Any help is appreciated. Thanks.

Answer 1

[Arkadiy Turevskiy]

From the doc:

Specifying Initial Conditions

Initial conditions are preset to zero. To specify initial conditions, convert to state-space form using tf2ss and use the State-Space block. The tf2ss utility provides the A, B, C, and D matrices for the system. For more information, type help tf2ss or see the Control System Toolbox™ documentation.

HTH.

Arkadiy

[ali veysel]

Thank you Arkadiy but I am using simulink blocks directly.

Is there any way to do it using the blocks?

[Kaustubha Govind]

Ali: Arkadiy is indeed talking about the Simulink Transfer Fcn block. His quote is from the Block reference page for the Transfer Fcn. It looks like you need to use convert your transfer function to a state space equation and use the State Space block instead. The State Space block allows you to specify initial conditions on its dialog.

Answer 2

[Martín José Caro Sanz]

Hello Ali.

There is a simple but effective way to do what you want in Simulink. You only have to change your equilibrium point. Your default initial condition is zero, and you can't change it in the mask of the transfer function, but you can make it manually.

You need to include a "sum" block at the input and at the output of the transfer function block. In the first one you are going to rest your equilibrium point, and in the second one, at the output, you are going to sum your equilibrium point. So the transfer function acts in the signal, but you change your initial point.

Maybe it is more clear if I show you a picture of your specific case.

Hope it helps.