Unknown Parameter in Transfer Function

Hi,

I am trying to simulate model reference adaptive control algorithm on Simulink. But i couldn't create a transfer function block which defines my plant. It must be like : b/(s+5). "b" is unknown parameter that's why i can't define it as a value. For example, i can't define b = 5 because purpose of algorithm is running by not knowing value of "b". When I define just b but not its value Simulink failed. It says it needs to define "b" with its numerical value. How can I define unknown parameter in transfer function block on Simulink ?

Answer 1

[Ameer Hamza]

You can write the time-domain equation of this transfer function and then implement it using elementary blocks. Then you can vary 'b' however you want. The attached file (saved in R2020b) shows a demo. The model is also shown in the following image

[Mert Candangüler]

The problem is that I don't want to vary or assign a value to 'b'. I want 'b' to stay unknown. Because the purpose of the algorithm is to get reference from model to regulate output of plant which has unknown parameter. I need to be able to define variable ,that has no value, in transfer function. Suppose that you are calculating x*(1/x). Value of x does not mean anything.

[Ameer Hamza]

In Simulink, you cannot leave any value undefined. In my model, I just used the sine wave as an example; you can connect b to anything. If you want to change 'b' based on some other logic, you can implement that and connect the value to 'b' port. In MARC, the unknown means that the control algorithm does not know the value of 'b'. It does not mean that the value of 'b' does not exist. As long as you don't directly input the value of 'b' to the controller and let it estimate the value itself, it should be fine.