TransferFunction — SciPy v1.15.3 Manual (original) (raw)
scipy.signal.
class scipy.signal.TransferFunction(*system, **kwargs)[source]#
Linear Time Invariant system class in transfer function form.
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 orZerosPolesGain)
- 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 theTransferFunction 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\(H(s) = \frac{s^2 + 3s + 3}{s^2 + 2s + 1}\):
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\(H(z) = \frac{z^2 + 3z + 3}{z^2 + 2z + 1}\) 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 )
Attributes:
Denominator of the TransferFunction system.
Return the sampling time of the system, None for lti systems.
Numerator of the TransferFunction system.
Poles of the system.
Zeros of the system.
Methods