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Fork of PES1 by
EncoderCounter/LowpassFilter.cpp
- Committer:
- itslinear
- Date:
- 2017-05-09
- Revision:
- 18:6547e54ac803
File content as of revision 18:6547e54ac803:
/* * LowpassFilter.cpp * Copyright (c) 2016, ZHAW * All rights reserved. */ #include "LowpassFilter.h" using namespace std; /** * Creates a LowpassFilter object with a default corner frequency of 1000 [rad/s]. */ LowpassFilter::LowpassFilter() { period = 1.0f; frequency = 1000.0f; a11 = (1.0f+frequency*period)*exp(-frequency*period); a12 = period*exp(-frequency*period); a21 = -frequency*frequency*period*exp(-frequency*period); a22 = (1.0f-frequency*period)*exp(-frequency*period); b1 = (1.0f-(1.0f+frequency*period)*exp(-frequency*period))/frequency/frequency; b2 = period*exp(-frequency*period); x1 = 0.0f; x2 = 0.0f; } /** * Deletes the LowpassFilter object. */ LowpassFilter::~LowpassFilter() {} /** * Resets the filtered value to zero. */ void LowpassFilter::reset() { x1 = 0.0f; x2 = 0.0f; } /** * Resets the filtered value to a given value. * @param value the value to reset the filter to. */ void LowpassFilter::reset(float value) { x1 = value/frequency/frequency; x2 = (x1-a11*x1-b1*value)/a12; } /** * Sets the sampling period of the filter. * This is typically the sampling period of the realtime thread of a controller that uses this filter. * @param the sampling period, given in [s]. */ void LowpassFilter::setPeriod(float period) { this->period = period; a11 = (1.0f+frequency*period)*exp(-frequency*period); a12 = period*exp(-frequency*period); a21 = -frequency*frequency*period*exp(-frequency*period); a22 = (1.0f-frequency*period)*exp(-frequency*period); b1 = (1.0f-(1.0f+frequency*period)*exp(-frequency*period))/frequency/frequency; b2 = period*exp(-frequency*period); } /** * Sets the corner frequency of this filter. * @param frequency the corner frequency of the filter in [rad/s]. */ void LowpassFilter::setFrequency(float frequency) { this->frequency = frequency; a11 = (1.0f+frequency*period)*exp(-frequency*period); a12 = period*exp(-frequency*period); a21 = -frequency*frequency*period*exp(-frequency*period); a22 = (1.0f-frequency*period)*exp(-frequency*period); b1 = (1.0f-(1.0f+frequency*period)*exp(-frequency*period))/frequency/frequency; b2 = period*exp(-frequency*period); } /** * Gets the current corner frequency of this filter. * @return the current corner frequency in [rad/s]. */ float LowpassFilter::getFrequency() { return frequency; } /** * Filters a value. * @param value the original unfiltered value. * @return the filtered value. */ float LowpassFilter::filter(float value) { float x1old = x1; float x2old = x2; x1 = a11*x1old+a12*x2old+b1*value; x2 = a21*x1old+a22*x2old+b2*value; return frequency*frequency*x1; }