Unwrapping the Phase Response Functions for Nonlinear Systems.

The higher order phase response functions contain important information about the behaviour of nonlinear systems. Unfortunately, simply adopting the linear convention of plotting the phase between +80 produces higher order phase response functions which are virtually impossible to interpret. In the present paper, two new algorithms are introduced to overcome these problems by unwrapping the multidimensional nonlinear phase. The unwrapped phase responses are shown to be much easier to interpret and details of the implementation together with examples illustrating the new techniques are included.