2 Copyright (C) 2008-2015 EDF R&D
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22 Author: Jean-Philippe Argaud, jean-philippe.argaud@edf.fr, EDF R&D
24 .. index:: single: ExtendedKalmanFilter
25 .. _section_ref_algorithm_ExtendedKalmanFilter:
27 Calculation algorithm "*ExtendedKalmanFilter*"
28 ----------------------------------------------
33 This algorithm realizes an estimation of the state of a dynamic system by a
34 extended Kalman Filter, using a non-linear calculation of the state.
36 Optional and required commands
37 ++++++++++++++++++++++++++++++
39 .. index:: single: Background
40 .. index:: single: BackgroundError
41 .. index:: single: Observation
42 .. index:: single: ObservationError
43 .. index:: single: ObservationOperator
44 .. index:: single: Bounds
45 .. index:: single: ConstrainedBy
46 .. index:: single: EstimationOf
47 .. index:: single: StoreInternalVariables
48 .. index:: single: StoreSupplementaryCalculations
50 The general required commands, available in the editing user interface, are the
54 *Required command*. This indicates the background or initial vector used,
55 previously noted as :math:`\mathbf{x}^b`. Its value is defined as a
56 "*Vector*" or a *VectorSerie*" type object.
59 *Required command*. This indicates the background error covariance matrix,
60 previously noted as :math:`\mathbf{B}`. Its value is defined as a "*Matrix*"
61 type object, a "*ScalarSparseMatrix*" type object, or a
62 "*DiagonalSparseMatrix*" type object.
65 *Required command*. This indicates the observation vector used for data
66 assimilation or optimization, previously noted as :math:`\mathbf{y}^o`. It
67 is defined as a "*Vector*" or a *VectorSerie* type object.
70 *Required command*. This indicates the observation error covariance matrix,
71 previously noted as :math:`\mathbf{R}`. It is defined as a "*Matrix*" type
72 object, a "*ScalarSparseMatrix*" type object, or a "*DiagonalSparseMatrix*"
76 *Required command*. This indicates the observation operator, previously
77 noted :math:`H`, which transforms the input parameters :math:`\mathbf{x}` to
78 results :math:`\mathbf{y}` to be compared to observations
79 :math:`\mathbf{y}^o`. Its value is defined as a "*Function*" type object or
80 a "*Matrix*" type one. In the case of "*Function*" type, different
81 functional forms can be used, as described in the section
82 :ref:`section_ref_operator_requirements`. If there is some control :math:`U`
83 included in the observation, the operator has to be applied to a pair
86 The general optional commands, available in the editing user interface, are
87 indicated in :ref:`section_ref_assimilation_keywords`. In particular, the
88 optional command "*AlgorithmParameters*" allows to choose the specific options,
89 described hereafter, of the algorithm. See
90 :ref:`section_ref_options_AlgorithmParameters` for the good use of this command.
92 The options of the algorithm are the following:
95 This key allows to define upper and lower bounds for every state variable
96 being optimized. Bounds have to be given by a list of list of pairs of
97 lower/upper bounds for each variable, with extreme values every time there
98 is no bound (``None`` is not allowed when there is no bound).
100 Example : ``{"Bounds":[[2.,5.],[1.e-2,10.],[-30.,1.e99],[-1.e99,1.e99]]}``
103 This key allows to choose the type of estimation to be performed. It can be
104 either state-estimation, with a value of "State", or parameter-estimation,
105 with a value of "Parameters". The default choice is "State".
107 Example : ``{"EstimationOf":"Parameters"}``
109 StoreInternalVariables
110 This Boolean key allows to store default internal variables, mainly the
111 current state during iterative optimization process. Be careful, this can be
112 a numerically costly choice in certain calculation cases. The default is
115 Example : ``{"StoreInternalVariables":True}``
117 StoreSupplementaryCalculations
118 This list indicates the names of the supplementary variables that can be
119 available at the end of the algorithm. It involves potentially costly
120 calculations or memory consumptions. The default is a void list, none of
121 these variables being calculated and stored by default. The possible names
122 are in the following list: ["APosterioriCovariance", "BMA", "Innovation"].
124 Example : ``{"StoreSupplementaryCalculations":["BMA","Innovation"]}``
126 Information and variables available at the end of the algorithm
127 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
129 At the output, after executing the algorithm, there are variables and
130 information originating from the calculation. The description of
131 :ref:`section_ref_output_variables` show the way to obtain them by the method
132 named ``get`` of the variable "*ADD*" of the post-processing. The input
133 variables, available to the user at the output in order to facilitate the
134 writing of post-processing procedures, are described in the
135 :ref:`subsection_r_o_v_Inventaire`.
137 The unconditional outputs of the algorithm are the following:
140 *List of vectors*. Each element is an optimal state :math:`\mathbf{x}*` in
141 optimization or an analysis :math:`\mathbf{x}^a` in data assimilation.
143 Example : ``Xa = ADD.get("Analysis")[-1]``
145 The conditional outputs of the algorithm are the following:
147 APosterioriCovariance
148 *List of matrices*. Each element is an *a posteriori* error covariance
149 matrix :math:`\mathbf{A}*` of the optimal state.
151 Example : ``A = ADD.get("APosterioriCovariance")[-1]``
154 *List of vectors*. Each element is a vector of difference between the
155 background and the optimal state.
157 Example : ``bma = ADD.get("BMA")[-1]``
160 *List of values*. Each element is a value of the error function :math:`J`.
162 Example : ``J = ADD.get("CostFunctionJ")[:]``
165 *List of values*. Each element is a value of the error function :math:`J^b`,
166 that is of the background difference part.
168 Example : ``Jb = ADD.get("CostFunctionJb")[:]``
171 *List of values*. Each element is a value of the error function :math:`J^o`,
172 that is of the observation difference part.
174 Example : ``Jo = ADD.get("CostFunctionJo")[:]``
177 *List of vectors*. Each element is a usual state vector used during the
178 optimization algorithm procedure.
180 Example : ``Xs = ADD.get("CurrentState")[:]``
183 *List of vectors*. Each element is an innovation vector, which is in static
184 the difference between the optimal and the background, and in dynamic the
190 References to other sections:
191 - :ref:`section_ref_algorithm_KalmanFilter`
192 - :ref:`section_ref_algorithm_UnscentedKalmanFilter`