/usr/include/ignition/math2/ignition/math/Filter.hh is in libignition-math2-dev 2.9.0+dfsg1-1.
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* Copyright (C) 2014 Open Source Robotics Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#ifndef IGNITION_MATH_FILTER_HH_
#define IGNITION_MATH_FILTER_HH_
#include <ignition/math/Helpers.hh>
#include <ignition/math/Vector3.hh>
#include <ignition/math/Quaternion.hh>
namespace ignition
{
namespace math
{
/// \class Filter Filter.hh ignition/math/Filter.hh
/// \brief Filter base class
template <class T>
class Filter
{
/// \brief Destructor.
public: virtual ~Filter() {}
/// \brief Set the output of the filter.
/// \param[in] _val New value.
public: virtual void Set(const T &_val)
{
y0 = _val;
}
/// \brief Set the cutoff frequency and sample rate.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: virtual void Fc(double _fc, double _fs) = 0;
/// \brief Get the output of the filter.
/// \return Filter's output.
public: virtual const T &Value() const
{
return y0;
}
/// \brief Output.
protected: T y0{};
};
/// \class OnePole Filter.hh ignition/math/Filter.hh
/// \brief A one-pole DSP filter.
/// \sa http://www.earlevel.com/main/2012/12/15/a-one-pole-filter/
template <class T>
class OnePole : public Filter<T>
{
/// \brief Constructor.
public: OnePole() = default;
/// \brief Constructor.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: OnePole(double _fc, double _fs)
{
this->Fc(_fc, _fs);
}
// Documentation Inherited.
public: virtual void Fc(double _fc, double _fs)
{
b1 = exp(-2.0 * IGN_PI * _fc / _fs);
a0 = 1.0 - b1;
}
/// \brief Update the filter's output.
/// \paran[in] _x Input value.
/// \return The filter's current output.
public: const T& Process(const T &_x)
{
this->y0 = a0 * _x + b1 * this->y0;
return this->y0;
}
/// \brief Input gain control.
protected: double a0 = 0;
/// \brief Gain of the feedback.
protected: double b1 = 0;
};
/// \class OnePoleQuaternion Filter.hh ignition/math/Filter.hh
/// \brief One-pole quaternion filter.
class OnePoleQuaternion : public OnePole<math::Quaterniond>
{
/// \brief Constructor.
public: OnePoleQuaternion()
{
this->Set(math::Quaterniond(1, 0, 0, 0));
}
/// \brief Constructor.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: OnePoleQuaternion(double _fc, double _fs)
: OnePole<math::Quaterniond>(_fc, _fs)
{
this->Set(math::Quaterniond(1, 0, 0, 0));
}
/// \brief Update the filter's output.
/// \paran[in] _x Input value.
/// \return The filter's current output.
public: const math::Quaterniond& Process(
const math::Quaterniond &_x)
{
y0 = math::Quaterniond::Slerp(a0, y0, _x);
return y0;
}
};
/// \class OnePoleVector3 Filter.hh ignition/math/Filter.hh
/// \brief One-pole vector3 filter.
class OnePoleVector3 : public OnePole<math::Vector3d>
{
/// \brief Constructor.
public: OnePoleVector3()
{
this->Set(math::Vector3d(0, 0, 0));
}
/// \brief Constructor.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: OnePoleVector3(double _fc, double _fs)
: OnePole<math::Vector3d>(_fc, _fs)
{
this->Set(math::Vector3d(0, 0, 0));
}
};
/// \class BiQuad Filter.hh ignition/math/Filter.hh
/// \brief Bi-quad filter base class.
/// \sa http://www.earlevel.com/main/2003/03/02/the-bilinear-z-transform/
template <class T>
class BiQuad : public Filter<T>
{
/// \brief Constructor.
public: BiQuad() = default;
/// \brief Constructor.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: BiQuad(double _fc, double _fs)
{
this->Fc(_fc, _fs);
}
// Documentation Inherited.
public: void Fc(double _fc, double _fs)
{
this->Fc(_fc, _fs, 0.5);
}
/// \brief Set the cutoff frequency, sample rate and Q coefficient.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
/// \param[in] _q Q coefficient.
public: void Fc(double _fc, double _fs, double _q)
{
double k = tan(IGN_PI * _fc / _fs);
double kQuadDenom = k * k + k / _q + 1.0;
this->a0 = k * k/ kQuadDenom;
this->a1 = 2 * this->a0;
this->a2 = this->a0;
this->b0 = 1.0;
this->b1 = 2 * (k * k - 1.0) / kQuadDenom;
this->b2 = (k * k - k / _q + 1.0) / kQuadDenom;
}
/// \brief Set the current filter's output.
/// \param[in] _val New filter's output.
public: virtual void Set(const T &_val)
{
this->y0 = this->y1 = this->y2 = this->x1 = this->x2 = _val;
}
/// \brief Update the filter's output.
/// \param[in] _x Input value.
/// \return The filter's current output.
public: virtual const T& Process(const T &_x)
{
this->y0 = this->a0 * _x +
this->a1 * this->x1 +
this->a2 * this->x2 -
this->b1 * this->y1 -
this->b2 * this->y2;
this->x2 = this->x1;
this->x1 = _x;
this->y2 = this->y1;
this->y1 = this->y0;
return this->y0;
}
/// \brief Input gain control coefficients.
protected: double a0 = 0,
a1 = 0,
a2 = 0,
b0 = 0,
b1 = 0,
b2 = 0;
/// \brief Gain of the feedback coefficients.
protected: T x1{}, x2{}, y1{}, y2{};
};
/// \class BiQuadVector3 Filter.hh ignition/math/Filter.hh
/// \brief BiQuad vector3 filter
class BiQuadVector3 : public BiQuad<math::Vector3d>
{
/// \brief Constructor.
public: BiQuadVector3()
{
this->Set(math::Vector3d(0, 0, 0));
}
/// \brief Constructor.
/// \param[in] _fc Cutoff frequency.
/// \param[in] _fs Sample rate.
public: BiQuadVector3(double _fc, double _fs)
: BiQuad<math::Vector3d>(_fc, _fs)
{
this->Set(math::Vector3d(0, 0, 0));
}
};
}
}
#endif
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