LowPassVelocityFilter.h

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/*
 * Copyright (c) 2018-2019, CNRS-UM LIRMM
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 * 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.
 *
 * 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 HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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#pragma once

#include <Eigen/Dense>

namespace utils
{

template<typename T>
struct LowPassVelocityFilter
{
  EIGEN_MAKE_ALIGNED_OPERATOR_NEW

  LowPassVelocityFilter(double dt) : dt_(dt)
  {
    reset(T::Zero());
  }

  LowPassVelocityFilter(double dt, double period) : dt_(dt)
  {
    reset(T::Zero());
    cutoffPeriod(period);
  }

  double cutoffPeriod() const
  {
    return cutoffPeriod_;
  }

  void cutoffPeriod(double period)
  {
    period = std::max(period, 2 * dt_); // Nyquist–Shannon sampling theorem
    cutoffPeriod_ = period;
  }

  void reset(T pos)
  {
    pos_ = pos;
    vel_ = T::Zero();
  }

  void update(const T & newPos)
  {
    double x = (cutoffPeriod_ <= dt_) ? 1. : dt_ / cutoffPeriod_;
    T discVel = (newPos - pos_) / dt_;
    T newVel = x * discVel + (1. - x) * vel_;
    pos_ = newPos;
    vel_ = newVel;
  }

  void updatePositionOnly(const T & newPos)
  {
    pos_ = newPos;
  }

  const T & vel()
  {
    return vel_;
  }

private:
  T pos_;
  T vel_;
  double cutoffPeriod_ = 0.;
  double dt_ = 0.005; // [s]
};

} // namespace utils

using utils::LowPassVelocityFilter;