Custom Block Frequency Simulation

[peters]

When trying to run Frequency Simulation involving non trivial custom blocks in a model, I received the following message:
Error 43: System has nonlinear blocks
I created a simple block with only one input port and one output port directly connected to each other and repeated the simulation involving only this block. I received the same message again. Did I overlook a parameter setting somewhere, or if it an issue or limitation, is there a workaround for this?

[PeterWay]

The frequency simulation cannot be done with nonlinear blocks in the model. Frequency simulations are only defined for linear systems since the Laplace transform depends on this. If you have any nonlinear blocks anywhere in the model, the Frequency response will show an error. Time responses can be calculated with any nonlinear systems.

If you wish to simulate frequency responses for nonlinear systems, establish an operating point by driving the system with an appropriate step. Determine the steady state value at the input to each nonlinearity and the slope at that point.. Then replace that non-linearity with a proportional block with a gain equivalent to the slope of the nonlinearity at that operating point. For example: if the nonlinearity is x^2, the slope of this function is 2x. If your operating point is x=3, the gain you need is 6.