Saturation function in Simulink

Hi, I would like to implement following block in simulink. How do I do it in Simulink: U = u_d - K/b * sat(σ /θ)

where: sat(σ/θ) = {1 if σ>θ, σ/θ if −θ ≤ σ ≤ θ, −1, σ < −θ}

u_d is input, K and b are constant. If possible even a matlab function would be appritiated.

Answer 1

[Sruthi Geetha]

In Simulink, you can implement this using If block and If action subsystem block. In the If block you can specify the number of inputs, If, elseif and else conditions. Connect three If action subsystems to each condition and generate the outputs as 1, sigma/theta and -1 for each of the conditions. You can also do this using a simple code in MATLAB Fcn block:

if sigma>theta
  out = 1;
elseif (sigma>=-theta)&&(sigma<=theta)
  out = sigma/theta;
else
  out = -1;
end

[Peppe]

I was more interested in doing it using simulink block without using any matlab functions

[Leigh Boyd]

did you ever get an answer to this? I have a similar problrm

[Peppe]

I did it manually in a matlab function. not by using any blocks.

Answer 2

[Endrias]

Simulink have a nice IF expression block which you can program the sat(.) function without any matlab written code. If anybody interested to see the block code, let me know.