ardupilot/libraries/PID/PID.h

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2013-05-29 20:50:37 -03:00
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/// @file PID.h
/// @brief Generic PID algorithm, with EEPROM-backed storage of constants.
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#ifndef __PID_H__
#define __PID_H__
#include <AP_Common/AP_Common.h>
#include <AP_Param/AP_Param.h>
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#include <stdlib.h>
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#include <math.h> // for fabs()
/// @class PID
/// @brief Object managing one PID control
class PID {
public:
PID(const float & initial_p = 0.0f,
const float & initial_i = 0.0f,
const float & initial_d = 0.0f,
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const int16_t & initial_imax = 0)
{
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AP_Param::setup_object_defaults(this, var_info);
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_kp = initial_p;
_ki = initial_i;
_kd = initial_d;
_imax = initial_imax;
// set _last_derivative as invalid when we startup
_last_derivative = NAN;
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}
/// Iterate the PID, return the new control value
///
/// Positive error produces positive output.
///
/// @param error The measured error value
/// @param scaler An arbitrary scale factor
///
/// @returns The updated control output.
///
float get_pid(float error, float scaler = 1.0);
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// get_pid() constrained to +/- 4500
int16_t get_pid_4500(float error, float scaler = 1.0);
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/// Reset the PID integrator
///
void reset_I();
/// Load gain properties
///
void load_gains();
/// Save gain properties
///
void save_gains();
/// @name parameter accessors
//@{
/// Overload the function call operator to permit relatively easy initialisation
void operator () (const float p,
const float i,
const float d,
const int16_t imaxval) {
_kp = p; _ki = i; _kd = d; _imax = imaxval;
}
float kP() const {
return _kp.get();
}
float kI() const {
return _ki.get();
}
float kD() const {
return _kd.get();
}
int16_t imax() const {
return _imax.get();
}
void kP(const float v) {
_kp.set(v);
}
void kI(const float v) {
_ki.set(v);
}
void kD(const float v) {
_kd.set(v);
}
void imax(const int16_t v) {
_imax.set(abs(v));
}
float get_integrator() const {
return _integrator;
}
static const struct AP_Param::GroupInfo var_info[];
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private:
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AP_Float _kp;
AP_Float _ki;
AP_Float _kd;
AP_Int16 _imax;
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float _integrator;///< integrator value
float _last_error;///< last error for derivative
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float _last_derivative;///< last derivative for low-pass filter
uint32_t _last_t;///< last time get_pid() was called in millis
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float _get_pid(float error, uint16_t dt, float scaler);
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/// Low pass filter cut frequency for derivative calculation.
///
/// 20 Hz becasue anything over that is probably noise, see
/// http://en.wikipedia.org/wiki/Low-pass_filter.
///
static const uint8_t _fCut = 20;
};
#endif