forked from Archive/PX4-Autopilot
92 lines
3.2 KiB
C++
92 lines
3.2 KiB
C++
/****************************************************************************
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*
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* Copyright (c) 2019-2020 PX4 Development Team. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file AlphaFilter.hpp
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*
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* @brief First order "alpha" IIR digital filter also known as leaky integrator or forgetting average.
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*
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* @author Mathieu Bresciani <brescianimathieu@gmail.com>
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* @author Matthias Grob <maetugr@gmail.com>
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*/
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#pragma once
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template <typename T>
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class AlphaFilter {
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public:
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AlphaFilter() = default;
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~AlphaFilter() = default;
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/**
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* Set filter parameters for time abstraction
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*
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* Both parameters have to be provided in the same units.
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*
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* @param sample_interval interval between two samples
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* @param time_constant filter time constant determining convergence
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*/
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void setParameters(float sample_interval, float time_constant) {
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setAlpha(sample_interval / (time_constant + sample_interval));
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}
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/**
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* Set filter parameter alpha directly without time abstraction
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*
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* @param alpha [0,1] filter weight for the previous state. High value - long time constant.
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*/
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void setAlpha(float alpha) { _alpha = alpha; }
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/**
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* Set filter state to an initial value
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*
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* @param sample new initial value
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*/
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void reset(const T &sample) { _filter_state = sample; }
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/**
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* Add a new raw value to the filter
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*
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* @return retrieve the filtered result
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*/
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void update(const T &sample) { _filter_state = updateCalculation(sample); }
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const T &getState() const { return _filter_state; }
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protected:
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T updateCalculation(const T &sample) { return (1.f - _alpha) * _filter_state + _alpha * sample; }
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float _alpha{0.f};
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T _filter_state{};
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};
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