mirror of
https://github.com/ArduPilot/ardupilot
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72cf1b4e57
git-svn-id: https://arducopter.googlecode.com/svn/trunk@959 f9c3cf11-9bcb-44bc-f272-b75c42450872
110 lines
2.6 KiB
C++
110 lines
2.6 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 <stdint.h>
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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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/// Constructor
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///
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/// A PID constructed in this fashion does not support save/restore.
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///
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PID() :
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_address(0)
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{}
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/// Constructor
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///
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/// @param address EEPROM base address at which PID parameters
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/// are stored. Zero if the PID does not support
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/// save/restore.
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///
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PID(uint16_t address) :
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_address(address)
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{}
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/// Constructor
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///
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/// @param gain_array Address of an array of floats from which
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/// gains will be loaded and to which they
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/// are saved.
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///
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PID(float *gain_array) :
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_gain_array(gain_array),
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_address(0) // must init address to zero to have gain_array respected
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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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long get_pid(int32_t error, uint16_t dt, 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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_integrator = 0;
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_last_error = 0;
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_last_derivative = 0;
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}
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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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float kP() { return _kp; }
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float kI() { return _ki; }
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float kD() { return _kd; }
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float imax() { return _imax; }
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void kP(float v) { _kp = v; }
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void kI(float v) { _ki = v; }
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void kD(float v) { _kd = v; }
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void imax(float v);
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//@}
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private:
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uint16_t _address; ///< EEPROM address for save/restore of P/I/D
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float *_gain_array; ///< pointer to the gains for this pid
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float _kp; ///< proportional gain
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float _ki; ///< integral gain
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float _kd; ///< derivative gain
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float _imax; ///< integrator magnitude clamp
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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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/// 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 _RC = 20;
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};
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#endif
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