How to plot frequency response for nonlinear closed loop system

[kramper]

Is there any other methods that can be used to plot the frequency response of the nonlinear closed loop system? Because from what I know, the frequency response/bode plot in matlab can be used only if the system is linear.
Thanks in advanced.
attached is the nonlinear closed loop system.

 

[Wheatley]

The frequency response represented by Bode's Diagrams is only valid for linear systems. Non-linearity means that the gain and phase introduced by your system depends not only of the input frequency but also of other parameters (input signal's amplitude, input signal's bias, input signal's frequency).

Thus, in order to represent the frequency response of your system, you should add more information to the Bode's Diagram. For instante, if the non-linearity cause an harmonic response, you should give the Total Harmonic Distortion.

 

[FvM]

You can derive a small signal frequency response for defined In1 and In2 levels (linearization in operation point).

 

[crutschow]

Where is the equation for the non-linearity?

 

[kramper]

The nonlinearity comes from the phase detector(PD) and the equation is represent by triangular wave.