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/* Copyright (C) 2013 Ion Torrent Systems, Inc. All Rights Reserved */
//! @file PIDloop.cpp
//! @ingroup BaseCaller
//! @brief PIDloop. Implementation of PID control loop
#include "PIDloop.h"
const float PIDloop::kSaturation = 0.25f;
//! @brief Default constructor
PIDloop::PIDloop()
: kP_(1.0f),
kI_(0.0f),
kD_(0.0f)
{
Initialize(0.0f);
}
//! @brief Constructor
//! @param[in] gainP Proportional gain coefficient
//! @param[in] gainI Integral gain coefficient
//! @param[in] gainD Derivative gain coefficient
//! @param[in] initVal Initial y(t) loop value
PIDloop::PIDloop(const float gainP, const float gainI, const float gainD, const float initVal)
: kP_(gainP),
kI_(gainI),
kD_(gainD)
{
Initialize(initVal);
}
//! @brief Initialize the PID loop to a known starting value
void PIDloop::Initialize(const float initVal)
{
yt_ = initVal;
dt_ = 1.0f;
et_ = 0.0f;
st_ = 0.0f;
iVal_ = 0.0f;
dVal_ = 0.0f;
}
//! @brief Iterate one time step
//! @param[in] val Next time-ordered sample to filter
//! @return Next time-ordered filtered sample
float PIDloop::Step(const float val)
{
float et = val - yt_;
// apply limiting to error signal (anti-windup guard)
if (et < -kSaturation)
et = -kSaturation;
else if (et > kSaturation)
et = kSaturation;
iVal_ += et; // integral
dVal_ = (et - et_) / dt_; // derivative
yt_ += kP_ * et + kI_ * iVal_ + kD_ * dVal_;
// update for next time
et_ = et;
dt_ = 1.0f;
st_ = val;
return yt_;
}
//! @brief Iterate one time step without input
//! @return Next time-ordered filtered sample (extrapolated)
float PIDloop::Step()
{
float et = st_ - yt_;
// apply limiting to error signal (anti-windup guard)
if (et < -kSaturation)
et = -kSaturation;
else if (et > kSaturation)
et = kSaturation;
yt_ += kP_ * et;
dt_ += 1.0f;
iVal_ /= 2.0f; // anti-windup
return yt_;
}
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