indirect.hpp

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#ifndef _BAYES_FILTER_INDIRECT
#define _BAYES_FILTER_INDIRECT

/*
 * Bayes++ the Bayesian Filtering Library
 * Copyright (c) 2002 Michael Stevens
 * See accompanying Bayes++.htm for terms and conditions of use.
 *
 * $Id: indirect.hpp 562 2006-04-05 20:46:23 +0200 (Wed, 05 Apr 2006) mistevens $
 */
 
/*
 * Indirect Filter Adaptor
 *  Hides the details of the indirect operation of the filter
 *  The error filter uses the same linear models as the direct filter,
 *  observation error computation (subtraction) is linear!
 */

/* Filter namespace */
namespace Bayesian_filter
{


template <typename Error_base>
class Indirect_state_filter : public State_filter {
/*
 * Indirect state filter
 *  Estimates state using an associated observation error filter
 */
public:
    Indirect_state_filter (Error_base& error_filter)
        : State_filter(error_filter.x.size()), direct(error_filter)
    {   // Construct and zero initial error filter
        direct.x.clear();
    }

    template <typename P_model>
    void predict (P_model& f)
    {
        x = f.f(x);
        direct.predict(f);              // May be optimised for linear f as x = 0
    };

    template <typename O_model>
    void observe (O_model& h, const FM::Vec& z)
    {
                // Observe error (explict temporary)
        FM::Vec z_error(z.size());
        z_error = h.h(x);
        z_error -= z;
        direct.observe (h, z_error);
                // Update State estimate with error
        x -= direct.x;
                // Reset the error
        direct.x.clear();
    }

    template <typename O_model>
    void observe_error (O_model& h, const FM::Vec& z_error)
    {
        direct.observe (h, z_error);
                // Update State estimate with error
        x -= direct.x;
                // Reset the error
        direct.x.clear();
    }

    void update ()
    /* Update filters state
         Updates x(k|k)
    */
    {}

private:
    Error_base& direct;
};


template <typename Error_base>
class Indirect_kalman_filter : public Kalman_state_filter {
/*
 * Indirect kalman filter
 *  Estimates state using an associated observation error filter
 */
public:
    Indirect_kalman_filter (Error_base& error_filter)
        : Kalman_state_filter(error_filter.x.size()), direct(error_filter)
    {   
    }

    void init ()
    /* Initialise from state and state covariance
    */
    {
        direct.x.clear();               // Zero initial error
        direct.X = X;
        direct.init();
    }

    template <typename P_model>
    void predict (P_model& f)
    {
        x = f.f(x);
        direct.predict(f);              // May be optimised for linear f as x = 0
    };

    template <typename O_model>
    void observe (O_model& h, const FM::Vec& z)
    {
                // Observe error (explict temporary)
        FM::Vec z_error(z.size());
        z_error = h.h(x);
        z_error -= z;
        direct.observe (h, z_error);
        direct.update();
                // Update State estimate with error
        x -= direct.x;
                // Reset the error
        direct.x.clear();
        direct.init ();
    }

    template <typename O_model>
    void observe_error (O_model& h, const FM::Vec& z_error)
    {
        direct.observe (h, z_error);
                // Update State estimate with error
        x -= direct.x;
                // Reset the error
        direct.clear();
    }

    void update ()
    /* Update filters state
         Updates x(k|k)
    */
    {
        direct.update();
        X = direct.X;
    }

private:
    Error_base& direct;
};


}//namespace
#endif

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