BlockRandGauss.hpp

Go to the documentation of this file.

/****************************************************************************
 *
 *   Copyright (C) 2012 PX4 Development Team. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 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.
 * 3. Neither the name PX4 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.
 *
 ****************************************************************************/

/**
 * @file blocks.h
 *
 * Controller library code
 */

#pragma once

#include <px4_platform_common/defines.h>
#include <assert.h>
#include <time.h>
#include <stdlib.h>
#include <math.h>
#include <mathlib/math/test/test.hpp>
#include <mathlib/math/filter/LowPassFilter2p.hpp>

#include "block/Block.hpp"
#include "block/BlockParam.hpp"

#include "matrix/math.hpp"

namespace control
{

class __EXPORT BlockRandGauss: public Block
{
public:
// methods
    BlockRandGauss(SuperBlock *parent,
               const char *name) :
        Block(parent, name),
        _mean(this, "MEAN"),
        _stdDev(this, "DEV")
    {
        // seed should be initialized somewhere
        // in main program for all calls to rand
        // XXX currently in nuttx if you seed to 0, rand breaks
    }
    virtual ~BlockRandGauss() = default;
    float update()
    {
        static float V1, V2, S;
        static int phase = 0;
        float X;

        if (phase == 0) {
            do {
                float U1 = (float)rand() / RAND_MAX;
                float U2 = (float)rand() / RAND_MAX;
                V1 = 2 * U1 - 1;
                V2 = 2 * U2 - 1;
                S = V1 * V1 + V2 * V2;
            } while (S >= 1 || fabsf(S) < 1e-8f);

            X = V1 * float(sqrtf(-2 * float(logf(S)) / S));

        } else {
            X = V2 * float(sqrtf(-2 * float(logf(S)) / S));
        }

        phase = 1 - phase;
        return X * getStdDev() + getMean();
    }
// accessors
    float getMean() { return _mean.get(); }
    float getStdDev() { return _stdDev.get(); }
private:
// attributes
    control::BlockParamFloat _mean;
    control::BlockParamFloat _stdDev;
};

} // namespace control