discrete_filter.hpp

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/********** !!! WARNING: CODE GENERATED BY TAPROOT. DO NOT EDIT !!! **********/
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/*
 * Copyright (c) 2024-2025 Advanced Robotics at the University of Washington <robomstr@uw.edu>
 *
 * This file is part of Taproot.
 *
 * Taproot is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Taproot is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Taproot.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef TAPROOT_DISCRETE_FILTER_HPP_
#define TAPROOT_DISCRETE_FILTER_HPP_
 
#include <array>
#include <cstdint>
 
namespace tap
{
namespace algorithms
{
template <uint8_t SIZE, typename T = float>
class DiscreteFilter
{
public:
    DiscreteFilter(
        std::array<T, SIZE> &naturalResponseCoefficients,
        std::array<T, SIZE> &forcedResponseCoefficients)
        : naturalResponseCoefficients(naturalResponseCoefficients),
          forcedResponseCoefficients(forcedResponseCoefficients)
    {
        reset();
    }
 
    T filterData(float dat)
    {
        for (int i = SIZE - 1; i > 0; i--)
        {
            forcedResponse[i] = forcedResponse[i - 1];
        }
        forcedResponse[0] = dat;
 
        float sum = 0;
        // Sum of forced response coefficients multiplied by the forced response X(n-k)
        // (previous input data)
        for (int i = 0; i < SIZE; i++)
        {
            sum += forcedResponseCoefficients[i] * forcedResponse[i];
        }
        // Sum of natural response coefficients multiplied by the natural response Y(n-k)
        // (previous output data)
        for (int i = 0; i < SIZE - 1; i++)
        {
            sum -= naturalResponseCoefficients[i + 1] * naturalResponse[i];
        }
        // Apply the 1/a_0 scaling to the output
        sum /= naturalResponseCoefficients[0];
 
        // Shift the natural response array to make room for the new output
        for (int i = SIZE - 1; i > 0; i--)
        {
            naturalResponse[i] = naturalResponse[i - 1];
        }
 
        naturalResponse[0] = sum;
 
        return naturalResponse[0];
    }
 
    T getLastFiltered() { return naturalResponse[0]; }
 
    T reset()
    {
        // Reset the filter state to zero
        naturalResponse.fill(0.0f);
        forcedResponse.fill(0.0f);
        return 0.0f;
    }
 
private:
    std::array<T, SIZE> naturalResponseCoefficients;
    std::array<T, SIZE> forcedResponseCoefficients;
    std::array<T, SIZE> naturalResponse;
    std::array<T, SIZE> forcedResponse;
};
 
}  // namespace algorithms
 
}  // namespace tap
 
#endif  // TAPROOT_DISCRETE_FILTER_HPP_