mirror of https://github.com/ArduPilot/ardupilot
125 lines
3.2 KiB
C++
125 lines
3.2 KiB
C++
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
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/// @file PID.h
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/// @brief Generic PID algorithm, with EEPROM-backed storage of constants.
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#ifndef __PID_H__
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#define __PID_H__
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#include <AP_Common.h>
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#include <AP_Param.h>
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#include <stdlib.h>
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#include <math.h> // for fabs()
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/// @class PID
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/// @brief Object managing one PID control
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class PID {
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public:
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PID(const float & initial_p = 0.0,
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const float & initial_i = 0.0,
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const float & initial_d = 0.0,
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const int16_t & initial_imax = 0)
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{
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_kp = initial_p;
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_ki = initial_i;
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_kd = initial_d;
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_imax = initial_imax;
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// set _last_derivative as invalid when we startup
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_last_derivative = NAN;
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}
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/// Iterate the PID, return the new control value
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///
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/// Positive error produces positive output.
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///
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/// @param error The measured error value
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/// @param dt The time delta in milliseconds (note
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/// that update interval cannot be more
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/// than 65.535 seconds due to limited range
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/// of the data type).
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/// @param scaler An arbitrary scale factor
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///
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/// @returns The updated control output.
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///
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int32_t get_pid(int32_t error, float scaler = 1.0);
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/// Reset the PID integrator
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///
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void reset_I();
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/// Load gain properties
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///
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void load_gains();
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/// Save gain properties
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///
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void save_gains();
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/// @name parameter accessors
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//@{
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/// Overload the function call operator to permit relatively easy initialisation
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void operator () (const float p,
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const float i,
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const float d,
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const int16_t imaxval) {
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_kp = p; _ki = i; _kd = d; _imax = imaxval;
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}
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float kP() const {
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return _kp.get();
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}
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float kI() const {
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return _ki.get();
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}
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float kD() const {
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return _kd.get();
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}
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int16_t imax() const {
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return _imax.get();
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}
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void kP(const float v) {
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_kp.set(v);
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}
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void kI(const float v) {
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_ki.set(v);
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}
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void kD(const float v) {
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_kd.set(v);
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}
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void imax(const int16_t v) {
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_imax.set(abs(v));
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}
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float get_integrator() const {
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return _integrator;
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}
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static const struct AP_Param::GroupInfo var_info[];
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private:
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AP_Float _kp;
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AP_Float _ki;
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AP_Float _kd;
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AP_Int16 _imax;
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float _integrator;///< integrator value
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int32_t _last_error;///< last error for derivative
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float _last_derivative;///< last derivative for low-pass filter
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uint32_t _last_t;///< last time get_pid() was called in millis
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int32_t _get_pid(int32_t error, uint16_t dt, float scaler);
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/// Low pass filter cut frequency for derivative calculation.
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///
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/// 20 Hz becasue anything over that is probably noise, see
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/// http://en.wikipedia.org/wiki/Low-pass_filter.
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///
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static const uint8_t _fCut = 20;
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};
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#endif
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