control.tf

Create a transfer function system. Can create MIMO systems.

The function accepts either 1, 2, or 3 parameters:

Convert a linear system into transfer function form. Always creates a new system, even if sys is already a TransferFunction object.

Create a transfer function system from its numerator and denominator polynomial coefficients.

If num and den are 1D array_like objects, the function creates a SISO system.

To create a MIMO system, num and den need to be 2D nested lists of array_like objects. (A 3 dimensional data structure in total.) (For details see note below.)

Create a discrete time transfer function system; dt can either be a positive number indicating the sampling time or ‘True’ if no specific timebase is given.

Create a transfer function representing the differential operator (‘s’) or delay operator (‘z’).

sys (LTI (StateSpace or TransferFunction)) – A linear system

num (array_like, or list of list of array_like) – Polynomial coefficients of the numerator

den (array_like, or list of list of array_like) – Polynomial coefficients of the denominator

display_format (None, 'poly' or 'zpk') – Set the display format used in printing the TransferFunction object. Default behavior is polynomial display and can be changed by changing config.defaults[‘xferfcn.display_format’]..

inputs (str, or list of str, optional) – List of strings that name the individual signals of the transformed system. If not given, the inputs and outputs are the same as the original system.

outputs (str, or list of str, optional) – List of strings that name the individual signals of the transformed system. If not given, the inputs and outputs are the same as the original system.

name (string, optional) – System name. If unspecified, a generic name is generated with a unique integer id.

out – The new linear system

TransferFunction

ValueError – if num and den have invalid or unequal dimensions

TypeError – if num or den are of incorrect type

See also

TransferFunction, ss, ss2tf, tf2ss

Notes

num[i][j] contains the polynomial coefficients of the numerator for the transfer function from the (j+1)st input to the (i+1)st output. den[i][j] works the same way.

The list [2, 3, 4] denotes the polynomial .

The special forms tf('s') and tf('z') can be used to create transfer functions for differentiation and unit delays.

Examples