control.tf2ss

control.tf2ss(sys)[source]

Transform a transfer function to a state space system.

The function accepts either 1 or 2 parameters:

tf2ss(sys)

Convert a transfer function into space space form. Equivalent to ss(sys).

tf2ss(num, den)

Create a state space system from its numerator and denominator polynomial coefficients.

For details see: tf.

Parameters

sysStateSpace or TransferFunction: A linear system.
numarray_like, or list of list of array_like: Polynomial coefficients of the numerator.
denarray_like, or list of list of array_like: Polynomial coefficients of the denominator.

Returns

outStateSpace: New linear system in state space form.

Other Parameters

inputs, outputsstr, 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.
namestring, optional: System name. If unspecified, a generic name ‘sys[id]’ is generated with a unique integer id.
methodstr, optional: Set the method used for computing the result. Current methods are ‘slycot’ and ‘scipy’. If set to None (default), try ‘slycot’ first and then ‘scipy’ (SISO only).

Raises

ValueError: If num and den have invalid or unequal dimensions, or if an invalid number of arguments is passed in.
TypeError: If num or den are of incorrect type, or if sys is not a TransferFunction object.

See also

ss, tf, ss2tf

Notes

The slycot routine used to convert a transfer function into state space form appears to have a bug and in some (rare) instances may not return a system with the same poles as the input transfer function. For SISO systems, setting method = ‘scipy’ can be used as an alternative.

Examples

>>> num = [[[1., 2.], [3., 4.]], [[5., 6.], [7., 8.]]]
>>> den = [[[9., 8., 7.], [6., 5., 4.]], [[3., 2., 1.], [-1., -2., -3.]]]
>>> sys1 = ct.tf2ss(num, den)

>>> sys_tf = ct.tf(num, den)
>>> sys2 = ct.tf2ss(sys_tf)