control.InputOutputSystem

class control.InputOutputSystem(name=None, inputs=None, outputs=None, states=None, input_prefix='u', output_prefix='y', state_prefix='x', **kwargs)

Bases: object

A class for representing input/output systems.

The InputOutputSystem class allows (possibly nonlinear) input/output systems to be represented in Python. It is used 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.

The timebase for the system, dt, is used to specify whether the system is operating in continuous or discrete time. It can have the following values:

• dt = None No timebase specified

• dt = 0 Continuous time system

• dt > 0 Discrete time system with sampling time dt

• dt = True Discrete time system with unspecified sampling time

Parameters

• inputs (int, list of str, or None) – Description of the system inputs. This can be given as an integer count or 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 given by the input_prefix parameter and has default value ‘u’). 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, with the prefix given by output_prefix (defaults to ‘y’).

• states (int, list of str, or None) – Description of the system states. Same format as inputs, with the prefix given by state_prefix (defaults to ‘x’).

• dt (None, True or float, optional) – System timebase. 0 (default) indicates continuous time, True indicates discrete time with unspecified sampling time, positive number is discrete time with specified sampling time, None indicates unspecified timebase (either continuous or discrete time).

• name (string, optional) – System name (used for specifying signals). If unspecified, a generic name <sys[id]> is generated with a unique integer id.

• params (dict, optional) – Parameter values for the system. Passed to the evaluation functions for the system as default values, overriding internal defaults.

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. 0 (default) indicates continuous time, True indicates discrete time with unspecified sampling time, positive number is discrete time with specified sampling time, None indicates unspecified timebase (either continuous or discrete 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

Parameters

• input_prefix (string, optional) – Set the prefix for input signals. Default = ‘u’.

• output_prefix (string, optional) – Set the prefix for output signals. Default = ‘y’.

• state_prefix (string, optional) – Set the prefix for state signals. Default = ‘x’.

Methods

copy	Make a copy of an input/output system
find_input	Find the index for an input given its name (None if not found)
find_inputs	Return list of indices matching input spec (None if not found)
find_output	Find the index for an output given its name (None if not found)
find_outputs	Return list of indices matching output spec (None if not found)
find_state	Find the index for a state given its name (None if not found)
find_states	Return list of indices matching state spec (None if not found)
isctime	Check to see if a system is a continuous-time system.
isdtime	Check to see if a system is a discrete-time system
issiso	Check to see if a system is single input, single output.
set_inputs	Set the number/names of the system inputs.
set_outputs	Set the number/names of the system outputs.
set_states	Set the number/names of the system states.
update_names	Update signal and system names for an I/O system.

copy(name=None, use_prefix_suffix=True)

Make a copy of an input/output system

A copy of the system is made, with a new name. The name keyword can be used to specify a specific name for the system. If no name is given and use_prefix_suffix is True, the name is constructed by prepending config.defaults[‘iosys.duplicate_system_name_prefix’] and appending config.defaults[‘iosys.duplicate_system_name_suffix’]. Otherwise, a generic system name of the form sys[<id>] is used, where <id> is based on an internal counter.

find_input(name)

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

find_inputs(name_list)

Return list of indices matching input spec (None if not found)

find_output(name)

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

find_outputs(name_list)

Return list of indices matching output spec (None if not found)

find_state(name)

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

find_states(name_list)

Return list of indices matching state spec (None if not found)

isctime(strict=False)

Check to see if a system is a continuous-time system.

Parameters

• sys (Named I/O system) – System to be checked

• strict (bool, optional) – If strict is True, make sure that timebase is not None. Default is False.

isdtime(strict=False)

Check to see if a system is a discrete-time system

Parameters

strict (bool, optional) – If strict is True, make sure that timebase is not None. Default is False.

issiso()

Check to see if a system is single input, single output.

ninputs

Number of system inputs.

noutputs

Number of system outputs.

nstates

Number of system states.

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].

update_names([name, inputs, outputs, states])

Update signal and system names for an I/O system.

Parameters

• name (str, optional) – New system name.

• inputs (list of str, int, or None, optional) – List of strings that name the individual input signals. If given as an integer or None, signal names default to the form u[i]. See InputOutputSystem for more information.

• outputs (list of str, int, or None, optional) – Description of output signals; defaults to y[i].

• states (int, list of str, int, or None, optional) – Description of system states; defaults to x[i].