dither.h

Go to the documentation of this file.

/*********************************************************************
 * Software License Agreement (BSD License)
 *
 *  Copyright (c) 2009, Willow Garage, Inc.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * 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.
 *   * Neither the name of the Willow Garage nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  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 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 *  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 *  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *********************************************************************/

#ifndef CTRL_TOOLBOX_DITHER_H
#define CTRL_TOOLBOX_DITHER_H

#include <cstdlib>
#include <ctime>
#include <math.h>
#include <ros/ros.h>

namespace control_toolbox {

/***************************************************/
class Dither
{
public:

  Dither();

  ~Dither();

  double update();

   /*
   *\brief Dither gets an amplitude, must be >0 to initialize
   *
   *\param amplitude Amplitude of white noise output
   *\param seed Random seed for white noise
   */
  bool init(const double &amplitude, const double &seed)
  {
    if (amplitude < 0.0)
    {
      ROS_ERROR("Dither amplitude not set properly. Amplitude must be >0.");
      return false;
    }
    
    amplitude_ = amplitude;

    // Somewhat mimics the old code.  A given seed gives a
    // reproducible sequence of random numbers, and that's what
    // matters.
    unsigned long s = (unsigned long)seed;
    seed_[0] = (s) ^ 45213;
    seed_[1] = (s >> 16) ^ 39204;
    seed_[2] = (s >> 32) ^ 5598;
    
    return true;
  }


private:
  double amplitude_;   
  double saved_value_;
  bool has_saved_value_;
  double s_;
  double x_;
  unsigned short seed_[3];
};
}

#endif