ButterworthFilter.cpp

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/*
 * This file is part of ArmarX.
 *
 * Copyright (C) 2011-2017, High Performance Humanoid Technologies (H2T), Karlsruhe Institute of Technology (KIT), all rights reserved.
 *
 * ArmarX is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * ArmarX 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 this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * @package    ArmarX
 * @author     Mirko Waechter( mirko.waechter at kit dot edu)
 * @date       2017
 * @copyright  http://www.gnu.org/licenses/gpl-2.0.txt
 *             GNU General Public License
 */
#include "ButterworthFilter.h"
#include <ArmarXCore/core/logging/Logging.h>
#include <ArmarXCore/core/exceptions/local/ExpressionException.h>
 
#include <cmath>
 
namespace armarx::rtfilters
{
 
    ButterworthFilter::ButterworthFilter(double frequency, int sampleRate, PassType filterPassType, double resonance) :
        RTFilterBase(0)
    {
        this->resonance = resonance;
        this->frequency = frequency;
        this->sampleRate = sampleRate;
        this->filterPassType = filterPassType;
        switch (filterPassType)
        {
            case Lowpass:
            {
                c = 1.0 / tan(M_PI * frequency / sampleRate);
                ARMARX_CHECK_EXPRESSION(!std::isnan(c)) << VAROUT(frequency) << VAROUT(sampleRate);
                a1 = 1.0 / (1.0 + resonance * c + c * c);
                ARMARX_CHECK_EXPRESSION(!std::isnan(a1)) << VAROUT(c) << VAROUT(frequency) << VAROUT(sampleRate);
                a2 = 2.0 * a1;
                a3 = a1;
                b1 = 2.0 * (1.0 - c * c) * a1;
                b2 = (1.0 - resonance * c + c * c) * a1;
            }
            break;
            case Highpass:
            {
                c = tan(M_PI * frequency / sampleRate);
                a1 = 1.0 / (1.0 + resonance * c + c * c);
                a2 = -2.0 * a1;
                a3 = a1;
                b1 = 2.0 * (c * c - 1.0) * a1;
                b2 = (1.0 - resonance * c + c * c) * a1;
                break;
            }
            default:
                ARMARX_INFO << "Unknown pass type";
 
        }
    }
 
    RTFilterBasePtr ButterworthFilter::clone() const
    {
        RTFilterBase* v = new ButterworthFilter(*this);
        return RTFilterBasePtr(v);
    }
 
    void ButterworthFilter::setInitialValue(double value)
    {
        for (auto& v : inputHistory)
        {
            v = value;
        }
        for (auto& v : outputHistory)
        {
            v = value;
        }
        newestValue = value;
    }
 
    double ButterworthFilter::calculate()
    {
        ARMARX_CHECK_EXPRESSION(!std::isnan(newestValue));
        double newOutput = a1 * newestValue + a2 * this->inputHistory[0] + a3 * this->inputHistory[1] - b1 * this->outputHistory[0] - b2 * this->outputHistory[1];
        ARMARX_CHECK_EXPRESSION(!std::isnan(newOutput));
        this->inputHistory[1] = this->inputHistory[0];
        this->inputHistory[0] = newestValue;
 
        this->outputHistory[2] = this->outputHistory[1];
        this->outputHistory[1] = this->outputHistory[0];
        this->outputHistory[0] = newOutput;
        return newOutput;
    }
 
    double ButterworthFilter::update(const IceUtil::Time& timestamp, double newValue)
    {
        newestValue = newValue;
        return calculate();
    }
 
 
}