control.iosys.InputOutputSystem

class control.iosys.InputOutputSystem(inputs=None, outputs=None, states=None, params={}, dt=None, name=None)

A class for representing input/output systems.

The InputOutputSystem class allows (possibly nonlinear) input/output systems to be represented in Python. It is intended as a parent class for a set of subclasses that are used to implement specific structures and operations for different types of input/output dynamical systems.

Parameters:
  • inputs (int, list of str, or None) – Description of the system inputs. This can be given as an integer count or as a list of strings that name the individual signals. If an integer count is specified, the names of the signal will be of the form s[i] (where s is one of u, y, or x). If this parameter is not given or given as None, the relevant quantity will be determined when possible based on other information provided to functions using the system.
  • outputs (int, list of str, or None) – Description of the system outputs. Same format as inputs.
  • states (int, list of str, or None) – Description of the system states. Same format as inputs.
  • dt (None, True or float, optional) – System timebase. None (default) indicates continuous time, True indicates discrete time with undefined sampling time, positive number is discrete time with specified sampling time.
  • params (dict, optional) – Parameter values for the systems. Passed to the evaluation functions for the system as default values, overriding internal defaults.
  • name (string, optional) – System name (used for specifying signals)
ninputs, noutputs, nstates

Number of input, output and state variables

Type:int
input_index, output_index, state_index

Dictionary of signal names for the inputs, outputs and states and the index of the corresponding array

Type:dict
dt

System timebase. None (default) indicates continuous time, True indicates discrete time with undefined sampling time, positive number is discrete time with specified sampling time.

Type:None, True or float
params

Parameter values for the systems. Passed to the evaluation functions for the system as default values, overriding internal defaults.

Type:dict, optional
name

System name (used for specifying signals)

Type:string, optional

Notes

The InputOuputSystem class (and its subclasses) makes use of two special methods for implementing much of the work of the class:

  • _rhs(t, x, u): compute the right hand side of the differential or difference equation for the system. This must be specified by the subclass for the system.
  • _out(t, x, u): compute the output for the current state of the system. The default is to return the entire system state.
__init__(inputs=None, outputs=None, states=None, params={}, dt=None, name=None)

Create an input/output system.

The InputOutputSystem contructor is used to create an input/output object with the core information required for all input/output systems. Instances of this class are normally created by one of the input/output subclasses: LinearIOSystem, NonlinearIOSystem, InterconnectedSystem.

Parameters:
  • inputs (int, list of str, or None) – Description of the system inputs. This can be given as an integer count or as a list of strings that name the individual signals. If an integer count is specified, the names of the signal will be of the form s[i] (where s is one of u, y, or x). If this parameter is not given or given as None, the relevant quantity will be determined when possible based on other information provided to functions using the system.
  • outputs (int, list of str, or None) – Description of the system outputs. Same format as inputs.
  • states (int, list of str, or None) – Description of the system states. Same format as inputs.
  • dt (None, True or float, optional) – System timebase. None (default) indicates continuous time, True indicates discrete time with undefined sampling time, positive number is discrete time with specified sampling time.
  • params (dict, optional) – Parameter values for the systems. Passed to the evaluation functions for the system as default values, overriding internal defaults.
  • name (string, optional) – System name (used for specifying signals)
Returns:

Input/output system object

Return type:

InputOutputSystem

Methods

__init__([inputs, outputs, states, params, …]) Create an input/output system.
copy() Make a copy of an input/output system.
feedback([other, sign, params]) Feedback interconnection between two input/output systems
find_input(name) Find the index for an input given its name (None if not found)
find_output(name) Find the index for an output given its name (None if not found)
find_state(name) Find the index for a state given its name (None if not found)
linearize(x0, u0[, t, params, eps]) Linearize an input/output system at a given state and input.
set_inputs(inputs[, prefix]) Set the number/names of the system inputs.
set_outputs(outputs[, prefix]) Set the number/names of the system outputs.
set_states(states[, prefix]) Set the number/names of the system states.
copy()

Make a copy of an input/output system.

feedback(other=1, sign=-1, params={})

Feedback interconnection between two input/output systems

Parameters:
  • sys1 (InputOutputSystem) – The primary process.
  • sys2 (InputOutputSystem) – The feedback process (often a feedback controller).
  • sign (scalar, optional) – The sign of feedback. sign = -1 indicates negative feedback, and sign = 1 indicates positive feedback. sign is an optional argument; it assumes a value of -1 if not specified.
Returns:

out

Return type:

InputOutputSystem

Raises:

ValueError – if the inputs, outputs, or timebases of the systems are incompatible.

find_input(name)

Find the index for an input given its name (None if not found)

find_output(name)

Find the index for an output given its name (None if not found)

find_state(name)

Find the index for a state given its name (None if not found)

linearize(x0, u0, t=0, params={}, eps=1e-06)

Linearize an input/output system at a given state and input.

Return the linearization of an input/output system at a given state and input value as a StateSpace system. See linearize() for complete documentation.

set_inputs(inputs, prefix='u')

Set the number/names of the system inputs.

Parameters:
  • inputs (int, list of str, or None) – Description of the system inputs. This can be given as an integer count or as a list of strings that name the individual signals. If an integer count is specified, the names of the signal will be of the form u[i] (where the prefix u can be changed using the optional prefix parameter).
  • prefix (string, optional) – If inputs is an integer, create the names of the states using the given prefix (default = ‘u’). The names of the input will be of the form prefix[i].
set_outputs(outputs, prefix='y')

Set the number/names of the system outputs.

Parameters:
  • outputs (int, list of str, or None) – Description of the system outputs. This can be given as an integer count or as a list of strings that name the individual signals. If an integer count is specified, the names of the signal will be of the form u[i] (where the prefix u can be changed using the optional prefix parameter).
  • prefix (string, optional) – If outputs is an integer, create the names of the states using the given prefix (default = ‘y’). The names of the input will be of the form prefix[i].
set_states(states, prefix='x')

Set the number/names of the system states.

Parameters:
  • states (int, list of str, or None) – Description of the system states. This can be given as an integer count or as a list of strings that name the individual signals. If an integer count is specified, the names of the signal will be of the form u[i] (where the prefix u can be changed using the optional prefix parameter).
  • prefix (string, optional) – If states is an integer, create the names of the states using the given prefix (default = ‘x’). The names of the input will be of the form prefix[i].