ardupilot/libraries/AC_PID/AC_HELI_PID.cpp

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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/// @file AC_HELI_PID.cpp
/// @brief Generic PID algorithm
#include <AP_Math/AP_Math.h>
#include "AC_HELI_PID.h"
const AP_Param::GroupInfo AC_HELI_PID::var_info[] PROGMEM = {
// @Param: P
// @DisplayName: PID Proportional Gain
// @Description: P Gain which produces an output value that is proportional to the current error value
AP_GROUPINFO("P", 0, AC_HELI_PID, _kp, 0),
// @Param: I
// @DisplayName: PID Integral Gain
// @Description: I Gain which produces an output that is proportional to both the magnitude and the duration of the error
AP_GROUPINFO("I", 1, AC_HELI_PID, _ki, 0),
// @Param: D
// @DisplayName: PID Derivative Gain
// @Description: D Gain which produces an output that is proportional to the rate of change of the error
AP_GROUPINFO("D", 2, AC_HELI_PID, _kd, 0),
// @Param: VFF
// @DisplayName: Velocity FF FeedForward Gain
// @Description: Velocity FF Gain which produces an output value that is proportional to the demanded input
AP_GROUPINFO("VFF", 4, AC_HELI_PID, _vff, 0),
// @Param: IMAX
// @DisplayName: PID Integral Maximum
// @Description: The maximum/minimum value that the I term can output
AP_GROUPINFO("IMAX", 5, AC_HELI_PID, _imax, 0),
// @Param: FILT_HZ
// @DisplayName: PID Input filter frequency in Hz
// @Description:
AP_GROUPINFO("FILT_HZ", 6, AC_HELI_PID, _filt_hz, AC_PID_FILT_HZ_DEFAULT),
// @Param: AFF
// @DisplayName: Acceleration FF FeedForward Gain
// @Description: Acceleration FF Gain which produces an output value that is proportional to the change in demanded input
AP_GROUPINFO("AFF", 7, AC_HELI_PID, _aff, 0),
AP_GROUPEND
};
/// Constructor for PID
AC_HELI_PID::AC_HELI_PID(float initial_p, float initial_i, float initial_d, float initial_imax, float initial_filt_hz, float dt, float initial_vff) :
AC_PID(initial_p, initial_i, initial_d, initial_imax, initial_filt_hz, dt)
{
_vff = initial_vff;
_aff = 0;
_last_requested_rate = 0;
}
float AC_HELI_PID::get_vff(float requested_rate)
{
_pid_info.FF = (float)requested_rate * _vff;
return _pid_info.FF;
}
float AC_HELI_PID::get_aff(float requested_rate)
{
float derivative;
// calculate derivative
if (_dt > 0.0f) {
derivative = (requested_rate - _last_requested_rate) / _dt;
} else {
derivative = 0;
}
_pid_info.AFF = derivative * _aff;
_last_requested_rate = requested_rate;
return _pid_info.AFF;
}
// This is an integrator which tends to decay to zero naturally
// if the error is zero.
float AC_HELI_PID::get_leaky_i(float leak_rate)
{
if(!is_zero(_ki) && !is_zero(_dt)){
_integrator -= (float)_integrator * leak_rate;
_integrator += ((float)_input * _ki) * _dt;
if (_integrator < -_imax) {
_integrator = -_imax;
} else if (_integrator > _imax) {
_integrator = _imax;
}
_pid_info.I = _integrator;
return _integrator;
}
return 0;
}