control.iosys.NonlinearIOSystem

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

Nonlinear I/O system.

This class is used to implement a system that is a nonlinear state space system (defined by and update function and an output function).

__init__(updfcn, outfcn=None, inputs=None, outputs=None, states=None, params={}, dt=None, name=None)

Create a nonlinear I/O system given update and output functions.

Creates an InputOutputSystem for a nonlinear system by specifying a state update function and an output function. The new system can be a continuous or discrete time system (Note: discrete-time systems not yet supported by most function.)

Parameters

• updfcn (callable) –

  Function returning the state update function

  updfcn(t, x, u[, param]) -> array

  where x is a 1-D array with shape (nstates,), u is a 1-D array with shape (ninputs,), t is a float representing the currrent time, and param is an optional dict containing the values of parameters used by the function.

• outfcn (callable) –

  Function returning the output at the given state

  outfcn(t, x, u[, param]) -> array

  where the arguments are the same as for upfcn.

• inputs (int, list of str or None, optional) – 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, optional) – Description of the system outputs. Same format as inputs.

• states (int, list of str, or None, optional) – Description of the system states. Same format as inputs.

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

• dt (timebase, optional) –

  The timebase for the system, 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 with unspecified sampling time

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

Returns

iosys – Nonlinear system represented as an input/output system.

Return type

NonlinearIOSystem

Methods

__init__(updfcn[, outfcn, inputs, outputs, …])	Create a nonlinear I/O system given update and output functions.
copy([newname])	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.
name_or_default([name])
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.

Attributes

idCounter

copy(newname=None)

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].