BlockDerivative.hpp

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

#pragma once

#include "BlockLowPass.hpp"

#include <px4_platform_common/defines.h>
#include <math.h>

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

#include "matrix/math.hpp"

namespace control
{

/**
 * A simple derivative approximation.
 * This uses the previous and current input.
 * This has a built in low pass filter.
 * @see LowPass
 */
class __EXPORT BlockDerivative : public SuperBlock
{
public:
// methods
    BlockDerivative(SuperBlock *parent, const char *name) :
        SuperBlock(parent, name),
        _u(0),
        _initialized(false),
        _lowPass(this, "LP")
    {}
    virtual ~BlockDerivative() = default;

    /**
     * Update the state and get current derivative
     *
     * This call updates the state and gets the current
     * derivative. As the derivative is only valid
     * on the second call to update, it will return
     * no change (0) on the first. To get a closer
     * estimate of the derivative on the first call,
     * call setU() one time step before using the
     * return value of update().
     *
     * @param input the variable to calculate the derivative of
     * @return the current derivative
     */
    float update(float input);
// accessors
    void setU(float u) {_u = u;}
    void reset() { _initialized = false; };
    float getU() {return _u;}
    float getLP() {return _lowPass.getFCut();}
    float getO() { return _lowPass.getState(); }
protected:
// attributes
    float _u; /**< previous input */
    bool _initialized;
    BlockLowPass _lowPass; /**< low pass filter */
};

} // namespace control