pycollo.phase.Phase#

Bases: object

A single continuous time phase as part of an optimal control problem.

name#: The name associated with a problem. Should be something short like ‘A’.

optimal_control_problem#: The OptimalControlProblem with which this phase is to be associated.

state_variables#: The continuous time state variables in this phase.

control_variables#: The continuous time control variables in this phase.

state_equations#: The dynamical state equations associated with this state variables in this phase.

integrand_functions#: The integrand functions corresponding to the integral variables in this phase.

path_constraints#: The continuous time path constraints associated with this phase.

bounds#: The phase bounds on this phase. See :obj:PhaseBounds for more details.

scaling#: The phase scaling on this phase. See :obj:PhaseScaling for more details.

guess#: The initial guess at which this phase is to be solved.

mesh#: This initial mesh on which this phase is to be solved.

_name#: Protected version of name.

_ocp#: Protected version of optimal_control_problem.

_phase_number#: Protected integer number associated with this phase. If not associated with any optimal control problem then defaults to None until one is associated. These are ordered sequentially starting at ‘0’ in the order with which phases are added to an optimal control problem.

_phase_suffix#: Protected str which is used in the naming of auto- generated Pycollo variables such as the endpoint state variables.

_y_var_user#: Protected version of state_variables.

_u_var_user#: Protected version of control_variables.

_q_var_user#: Protected version of integral_variables.

_t_var_user#: Protected version of time_variables.

_y_eqn_user#: Protected version of state_equations.

_c_con_user#: Protected version of path_constraints.

_q_fnc_user#: Protected version of integrand_functions.

_t0_USER#: Protected version of initial_time_variable.

_tF_USER#: Protected version of final_time_variable.

_t0#: Internal Pycollo symbol for phase initial time.

_tF#: Internal Pycollo symbol for phase final time.

_STRETCH#: Convenience expression for phase time scaling stretch.

_SHIFT#

Convenience expression for phase time scaling shift.

Attributes

bounds

control_variables

Symbols for this phase's control variables in order added by user.

final_state_variables

Symbols for this phase's state variables at the final time.

final_time_variable

Symbol for the time at which this phase begins.

guess

initial_state_variables

Symbols for this phase's state variables at the initial time.

initial_time_variable

Symbol for the time at which this phase begins.

integral_variables

Symbols for this phase's integral variables.

integrand_functions

mesh

name

Name of the phase.

number_control_variables

Integer number of control variables in the phase.

number_integral_variables

Integer number of integral variables in the phase.

number_integrand_functions

number_path_constraints

number_state_equations

Integer number of state equations in the phase.

number_state_variables

Integer number of state variables in the phase.

optimal_control_problem

The optimal control problem with which this phase is associated.

path_constraints

phase_number

The integer numerical identifier for the phase.

scaling

state_equations

User-supplied dynamical equations in the phase.

state_variables

Symbols for this phase's state variables in order added by user.

time_variables

The initial and final time symbols as a pair.

Methods

__init__

Initialise the Phase object with minimum a name.

create_new_copy

create_new_copy_like

Constructor class to copy a phase.

Initialise the Phase object with minimum a name.

Parameters:

name – The name associated with a problem. Should be something short like ‘A’.
optimal_control_problem – The OptimalControlProblem with which this phase is to be associated. Default value is None in which case the phase remain uninitialised to an optimal control problem.
state_variables – The continuous time state variables in this phase. Default value is None in which case the phase has no associated state variables and no phase-specific endpoint time or state variables are created.
control_variables – The continuous time control variables in this phase. Default value is None in which case the phase has no associated control variables.
state_equations – The dynamical state equations associated with this state variables in this phase. Default value is None in which case no dynamical equations have been added to the phase yet.
integrand_functions – The integrand functions corresponding to the integral variables in this phase. Default value is None in which case the phase has no integrand functions associated with it and no phase-specific integral variables are created.
path_constraints – The continuous time path constraints associated with this phase. Default value is None in which case the phase has no path constraints associated with it.
bounds – The phase bounds on this phase. See :obj:PhaseBounds for more details. Default value is None in which case an empty PhaseBounds object is instantiated and associated with the phase.
scaling – The phase scaling on this phase. See :obj:PhaseScaling for more details. Default value is None in which case an empty PhaseScaling object is instantiated and associated with the phase.
guess – The initial guess at which this phase is to be solved. Default value is None in which case an empty PhaseGuess object is instantiated and associated with the phase.
mesh – This initial mesh on which this phase is to be solved. Default value is None in which case an empty PhaseMesh object is instantiated and associated with the phase.

__repr__()[source]#: Return repr(self).

__str__()[source]#: Return str(self).

__weakref__#: list of weak references to the object (if defined)

property control_variables: Tuple[Symbol, ...] | NamedTuple#

Symbols for this phase’s control variables in order added by user.

The user may supply either a single symbol or an iterable of symbols. The supplied argument is handled by the format_as_tuple method from the utils module.

static create_new_copy_like(phase_for_copying: Phase, name: str, **kwargs)[source]#: Constructor class to copy a phase.

property final_state_variables: Tuple[Symbol, ...] | NamedTuple#

Symbols for this phase’s state variables at the final time.

Raises:: AttributeError – If optimal_control_problem property has not yet been set to a not None value. See docstring for state_variables for details about why.

property final_time_variable: Symbol#: Symbol for the time at which this phase begins.

property initial_state_variables: Tuple[Symbol, ...] | NamedTuple#

Symbols for this phase’s state variables at the initial time.

Raises:: AttributeError – If optimal_control_problem property has not yet been set to a not None value. See docstring for state_variables for details about why.

property initial_time_variable: Symbol#: Symbol for the time at which this phase begins.

property integral_variables: Tuple[Symbol, ...] | NamedTuple#

Symbols for this phase’s integral variables.

These symbols are auto generated as required by the user-supplied integrand functions.

property name#: Name of the phase.

property number_control_variables: int#: Integer number of control variables in the phase.

property number_integral_variables: int#: Integer number of integral variables in the phase.

property number_state_equations: int#

Integer number of state equations in the phase.

Should be the same as the number of state variables, i.e. there should be a direct mapping between the two.

property number_state_variables: int#: Integer number of state variables in the phase.

property optimal_control_problem: OptimalControlProblem | None#

The optimal control problem with which this phase is associated.

There are two allowable scenarios. In the first scenario a phase may be instantiated without being associated with an optimal control problem. If this is the case then the default values of None for the phase number and ‘X’ for the phase suffix remain.

In the second scenario a phase is instantiated with an associated optimal control problem or is associated with an optimal control problem after the first type of instantiation. In this case the phase is appended to the protected _phases attribute of the OptimalControlProblem, the phase number is set according to its position in the order of addition to the optimal controls problem’s phases, and its phase suffix is set as a string version of the phase number. Finally a replacement of any symbols that may have been used in supplementary information about the phase that contained the placeholder ‘X’ phase suffix are renamed and substituted.

No checking is done to see whether the phase is already associated with the optimal control problem in question or any other optimal control problem. The reason being that if the setter method for this property is accessed after having already been set then an AttributeError is raised (see below). The reason this class works like that is to avoid having to allow phases to be disassociated from an OptimalControlProblem and thus having to handled the complexities that would come with the phase renumbering and substitution of any phase-related information that has already been given to the optimal control problem.

Raises:: AttributeError – If an OptimalControlProblem has already been associated with self. If a argument of any type other than OptimalControlProblem is passed to the optimal_control_problem property setter.

property phase_number: int | None#

The integer numerical identifier for the phase.

If this phase has not yet been associated with an optimal control problem then None is returned.

Corresponds to the chronological order in which it was associated with the optimal control problem in question.

property state_equations: Tuple[Expr, ...]#

User-supplied dynamical equations in the phase.

These equations are the dynamical equations associated with each of the state variables in the phase. There should therefore be exactly one state equation for each dynamics symbol.

State equations can be supplied in a compact form by the user defining additional auxiliary symbols and

property state_variables: Tuple[Symbol, ...] | NamedTuple#

Symbols for this phase’s state variables in order added by user.

The user may supply either a single symbol or an iterable of symbols. The supplied argument is handled by the format_as_tuple method from the utils module. Additional protected attributes _y_t0_user and _y_tF_user are set by post-appending either ‘_PX(t0)’ or ‘_PX(tF)’ to the user supplied symbols where the X is replaced by the phase suffix. As such if this phase has not yet been associated with an optimal control problem yet then self will not have attributes _y_t0_user and _y_tF_user and accessing either the initial_state or final_state property will raise an AttributeError.

property time_variables: Tuple[Symbol, ...] | NamedTuple#: The initial and final time symbols as a pair.

`bounds`
`control_variables`	Symbols for this phase's control variables in order added by user.
`final_state_variables`	Symbols for this phase's state variables at the final time.
`final_time_variable`	Symbol for the time at which this phase begins.
`guess`
`initial_state_variables`	Symbols for this phase's state variables at the initial time.
`initial_time_variable`	Symbol for the time at which this phase begins.
`integral_variables`	Symbols for this phase's integral variables.
`integrand_functions`
`mesh`
`name`	Name of the phase.
`number_control_variables`	Integer number of control variables in the phase.
`number_integral_variables`	Integer number of integral variables in the phase.
`number_integrand_functions`
`number_path_constraints`
`number_state_equations`	Integer number of state equations in the phase.
`number_state_variables`	Integer number of state variables in the phase.
`optimal_control_problem`	The optimal control problem with which this phase is associated.
`path_constraints`
`phase_number`	The integer numerical identifier for the phase.
`scaling`
`state_equations`	User-supplied dynamical equations in the phase.
`state_variables`	Symbols for this phase's state variables in order added by user.
`time_variables`	The initial and final time symbols as a pair.

`__init__`	Initialise the Phase object with minimum a name.
`create_new_copy`
`create_new_copy_like`	Constructor class to copy a phase.