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91 lines
3.2 KiB
91 lines
3.2 KiB
/**************************************************************************** |
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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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