diff options
Diffstat (limited to 'src/lib/mathlib/math/filter')
| -rw-r--r-- | src/lib/mathlib/math/filter/LowPassFilter2p.cpp | 77 | ||||
| -rw-r--r-- | src/lib/mathlib/math/filter/LowPassFilter2p.hpp | 78 | ||||
| -rw-r--r-- | src/lib/mathlib/math/filter/module.mk | 43 |
3 files changed, 198 insertions, 0 deletions
diff --git a/src/lib/mathlib/math/filter/LowPassFilter2p.cpp b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp new file mode 100644 index 000000000..efb17225d --- /dev/null +++ b/src/lib/mathlib/math/filter/LowPassFilter2p.cpp @@ -0,0 +1,77 @@ +// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- + +/**************************************************************************** + * + * Copyright (C) 2012 PX4 Development Team. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name PX4 nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/// @file LowPassFilter.cpp +/// @brief A class to implement a second order low pass filter +/// Author: Leonard Hall <LeonardTHall@gmail.com> + +#include "LowPassFilter2p.hpp" +#include "math.h" + +namespace math +{ + +void LowPassFilter2p::set_cutoff_frequency(float sample_freq, float cutoff_freq) +{ + _cutoff_freq = cutoff_freq; + float fr = sample_freq/_cutoff_freq; + float ohm = tanf(M_PI_F/fr); + float c = 1.0f+2.0f*cosf(M_PI_F/4.0f)*ohm + ohm*ohm; + _b0 = ohm*ohm/c; + _b1 = 2.0f*_b0; + _b2 = _b0; + _a1 = 2.0f*(ohm*ohm-1.0f)/c; + _a2 = (1.0f-2.0f*cosf(M_PI_F/4.0f)*ohm+ohm*ohm)/c; +} + +float LowPassFilter2p::apply(float sample) +{ + // do the filtering + float delay_element_0 = sample - _delay_element_1 * _a1 - _delay_element_2 * _a2; + if (isnan(delay_element_0) || isinf(delay_element_0)) { + // don't allow bad values to propogate via the filter + delay_element_0 = sample; + } + float output = delay_element_0 * _b0 + _delay_element_1 * _b1 + _delay_element_2 * _b2; + + _delay_element_2 = _delay_element_1; + _delay_element_1 = delay_element_0; + + // return the value. Should be no need to check limits + return output; +} + +} // namespace math + diff --git a/src/lib/mathlib/math/filter/LowPassFilter2p.hpp b/src/lib/mathlib/math/filter/LowPassFilter2p.hpp new file mode 100644 index 000000000..208ec98d4 --- /dev/null +++ b/src/lib/mathlib/math/filter/LowPassFilter2p.hpp @@ -0,0 +1,78 @@ +// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- + +/**************************************************************************** + * + * Copyright (C) 2012 PX4 Development Team. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name PX4 nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/// @file LowPassFilter.h +/// @brief A class to implement a second order low pass filter +/// Author: Leonard Hall <LeonardTHall@gmail.com> +/// Adapted for PX4 by Andrew Tridgell + +#pragma once + +namespace math +{ +class __EXPORT LowPassFilter2p +{ +public: + // constructor + LowPassFilter2p(float sample_freq, float cutoff_freq) { + // set initial parameters + set_cutoff_frequency(sample_freq, cutoff_freq); + _delay_element_1 = _delay_element_2 = 0; + } + + // change parameters + void set_cutoff_frequency(float sample_freq, float cutoff_freq); + + // apply - Add a new raw value to the filter + // and retrieve the filtered result + float apply(float sample); + + // return the cutoff frequency + float get_cutoff_freq(void) const { + return _cutoff_freq; + } + +private: + float _cutoff_freq; + float _a1; + float _a2; + float _b0; + float _b1; + float _b2; + float _delay_element_1; // buffered sample -1 + float _delay_element_2; // buffered sample -2 +}; + +} // namespace math diff --git a/src/lib/mathlib/math/filter/module.mk b/src/lib/mathlib/math/filter/module.mk new file mode 100644 index 000000000..f5c0647c8 --- /dev/null +++ b/src/lib/mathlib/math/filter/module.mk @@ -0,0 +1,43 @@ +############################################################################ +# +# Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions +# are met: +# +# 1. Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# 2. Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in +# the documentation and/or other materials provided with the +# distribution. +# 3. Neither the name PX4 nor the names of its contributors may be +# used to endorse or promote products derived from this software +# without specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS +# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED +# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +# POSSIBILITY OF SUCH DAMAGE. +# +############################################################################ + +# +# filter library +# +SRCS = LowPassFilter2p.cpp + +# +# In order to include .config we first have to save off the +# current makefile name, since app.mk needs it. +# +APP_MAKEFILE := $(lastword $(MAKEFILE_LIST)) |