from abc import abstractmethod
from ..base import Base, Property
from ..models.measurement import MeasurementModel
[docs]class Updater(Base):
r"""Updater base class
An updater is used to update the predicted state, utilising a measurement
and a :class:`~.MeasurementModel`. The general observation model is
.. math::
\mathbf{z} = h(\mathbf{x}, \mathbf{\sigma})
where :math:`\mathbf{x}` is the state, :math:`\mathbf{\sigma}`, the
measurement noise and :math:`\mathbf{z}` the resulting measurement.
"""
measurement_model: MeasurementModel = Property(doc="measurement model")
def _check_measurement_model(self, measurement_model):
"""Check that the measurement model passed actually exists. If not
attach the one in the updater. If that one's not specified, return an
error.
Parameters
----------
measurement_model : :class`~.MeasurementModel`
A measurement model to be checked
Returns
-------
: :class`~.MeasurementModel`
The measurement model to be used
"""
if measurement_model is None:
if self.measurement_model is None:
raise ValueError("No measurement model specified")
else:
measurement_model = self.measurement_model
return measurement_model
[docs] @abstractmethod
def predict_measurement(
self, state_prediction, measurement_model=None, **kwargs):
"""Get measurement prediction from state prediction
Parameters
----------
state_prediction : :class:`~.StatePrediction`
The state prediction
measurement_model: :class:`~.MeasurementModel`, optional
The measurement model used to generate the measurement prediction.
Should be used in cases where the measurement model is dependent
on the received measurement. The default is `None`, in which case
the updater will use the measurement model specified on
initialisation
Returns
-------
: :class:`~.MeasurementPrediction`
The predicted measurement
"""
raise NotImplementedError
[docs] @abstractmethod
def update(self, hypothesis, **kwargs):
"""Update state using prediction and measurement.
Parameters
----------
hypothesis : :class:`~.Hypothesis`
Hypothesis with predicted state and associated detection used for
updating.
Returns
-------
: :class:`~.State`
The state posterior
"""
raise NotImplementedError