mirror of
https://github.com/ArduPilot/ardupilot
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52abef58d5
git-svn-id: https://arducopter.googlecode.com/svn/trunk@932 f9c3cf11-9bcb-44bc-f272-b75c42450872
90 lines
2.2 KiB
C++
90 lines
2.2 KiB
C++
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
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/// @file PID.cpp
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/// @brief Generic PID algorithm, with EEPROM-backed storage of constants.
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#include <math.h>
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#include "PID.h"
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long
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PID::get_pid(long error, long dt, float scaler)
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{
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float output = 0;
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float delta_time = (float)dt / 1000;
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// Compute proportional component
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output += error * _kp;
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// Compute derivative component if time has elapsed
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if (_kd && (dt > 0)) {
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float derivative = (error - _last_error) / delta_time;
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// discrete low pass filter, cuts out the
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// high frequency noise that can drive the controller crazy
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derivative = _last_derivative +
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((delta_time / (_RC + delta_time)) * (derivative - _last_derivative));
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// update state
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_last_error = error;
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_last_derivative = derivative;
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// add in derivative component
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output += _kd * derivative;
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}
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// scale the P and D components
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output *= scaler;
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// Compute integral component if time has elapsed
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if (_ki && (dt > 0)) {
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_integrator += (error * _ki) * scaler * delta_time;
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if (_integrator < -_imax) {
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_integrator = -_imax;
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} else if (_integrator > _imax) {
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_integrator = _imax;
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}
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output += _integrator;
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}
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return output;
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}
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void
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PID::imax(float v)
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{
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_imax = fabs(v);
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}
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void
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PID::load_gains()
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{
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if (_address) {
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_kp = (float)(eeprom_read_word((uint16_t *) _address)) / 1000.0;
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_ki = (float)(eeprom_read_word((uint16_t *) (_address + 2))) / 1000.0;
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_kd = (float)(eeprom_read_word((uint16_t *) (_address + 4))) / 1000.0;
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_imax = eeprom_read_word((uint16_t *) (_address + 6)) * 100;
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} else {
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_kp = _gain_array[0]/ 1000.0;
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_ki = _gain_array[1]/ 1000.0;
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_kd = _gain_array[2]/ 1000.0;
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_imax = _gain_array[3]/ 1000.0;
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}
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}
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void
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PID::save_gains()
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{
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if (_address) {
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eeprom_write_word((uint16_t *) _address, (int)(_kp * 1000));
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eeprom_write_word((uint16_t *) (_address + 2), (int)(_ki * 1000));
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eeprom_write_word((uint16_t *) (_address + 4), (int)(_kd * 1000));
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eeprom_write_word((uint16_t *) (_address + 6), (int)_imax/100);
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} else {
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_gain_array[0] = _kp * 1000;
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_gain_array[1] = _ki * 1000;
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_gain_array[2] = _kd * 1000;
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_gain_array[3] = _imax * 1000;
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}
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}
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