`scipy.signal._ltisys:TransferFunction`

source: /scipy/signal/_ltisys.py:733

Signature

class TransferFunction(*system, dt = None)

Members

Summary

Linear Time Invariant system class in transfer function form.

Extended Summary

Represents the system as the continuous-time transfer function $H (s) = \sum_{i = 0}^{N} b [N - i] s^{i} / \sum_{j = 0}^{M} a [M - j] s^{j}$ or the discrete-time transfer function $H (z) = \sum_{i = 0}^{N} b [N - i] z^{i} / \sum_{j = 0}^{M} a [M - j] z^{j}$ , where $b$ are elements of the numerator num, $a$ are elements of the denominator den, and N == len(b) - 1, M == len(a) - 1. TransferFunction systems inherit additional functionality from the lti, respectively the dlti classes, depending on which system representation is used.

Parameters

*system : arguments

The TransferFunction class can be instantiated with 1 or 2 arguments. The following gives the number of input arguments and their interpretation:

1: lti or dlti system: (StateSpace, TransferFunction or ZerosPolesGain)
2: array_like: (numerator, denominator)

dt : float, optional

Sampling time [s] of the discrete-time systems. Defaults to None (continuous-time). Must be specified as a keyword argument, for example, dt=0.1.

Notes

Changing the value of properties that are not part of the TransferFunction system representation (such as the A, B, C, D state-space matrices) is very inefficient and may lead to numerical inaccuracies. It is better to convert to the specific system representation first. For example, call sys = sys.to_ss() before accessing/changing the A, B, C, D system matrices.

If (numerator, denominator) is passed in for *system, coefficients for both the numerator and denominator should be specified in descending exponent order (e.g. s^2 + 3s + 5 or z^2 + 3z + 5 would be represented as [1, 3, 5])

Examples

Construct the transfer function :math:`H(s) = \frac{s^2 + 3s + 3}{s^2 + 2s + 1}`:

from scipy import signal

✓

num = [1, 3, 3]
den = [1, 2, 1]

✓

signal.TransferFunction(num, den)

✓

TransferFunctionContinuous(
array([1., 3., 3.]),
array([1., 2., 1.]),
dt: None
)

Construct the transfer function :math:`H(z) = \frac{z^2 + 3z + 3}{z^2 + 2z + 1}` with a sampling time of 0.1 seconds:

signal.TransferFunction(num, den, dt=0.1)

✓

TransferFunctionDiscrete(
array([1., 3., 3.]),
array([1., 2., 1.]),
dt: 0.1
)

Aliases

scipy.signal.TransferFunction