ardupilot/libraries/AC_PID/AC_HELI_PID.h

#pragma once

/// @file	AC_HELI_PID.h
/// @brief	Helicopter Specific Rate PID algorithm, with EEPROM-backed storage of constants.

#include <AP_Common/AP_Common.h>
#include <AP_Param/AP_Param.h>
#include <stdlib.h>
#include <cmath>
#include "AC_PID.h"

#define AC_PID_LEAK_MIN     0.1  // Default I-term Leak Minimum

/// @class	AC_HELI_PID
/// @brief	Heli PID control class
class AC_HELI_PID : public AC_PID {
public:

    /// Constructor for PID
    AC_HELI_PID(float initial_p, float initial_i, float initial_d, float initial_imax, float initial_filt_hz, float dt, float initial_ff);

    /// get_vff - return Velocity FeedForward Term 
    float       get_vff(float requested_rate);

    /// get_leaky_i - replacement for get_i but output is leaded at leak_rate
    float       get_leaky_i(float leak_rate);

    // accessors
    float       ff() const { return _vff.get(); }
    void        ff(const float v) { _vff.set(v); }

    static const struct AP_Param::GroupInfo        var_info[];

private:
    AP_Float        _vff;
    AP_Float        _leak_min;

    float           _last_requested_rate;       // Requested rate from last iteration, used to calculate rate change of requested rate
};