mirror of https://github.com/ArduPilot/ardupilot
85 lines
1.6 KiB
C++
85 lines
1.6 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
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#include <math.h>
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#include "PID.h"
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const AP_Param::GroupInfo PID::var_info[] PROGMEM = {
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AP_GROUPINFO("P", PID, _kp),
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AP_GROUPINFO("I", PID, _ki),
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AP_GROUPINFO("D", PID, _kd),
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AP_GROUPINFO("IMAX", PID, _imax),
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AP_GROUPEND
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};
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long
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PID::get_pid(int32_t error, uint16_t dt, float scaler)
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{
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float output = 0;
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float delta_time = (float)dt / 1000.0;
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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 ((fabs(_kd) > 0) && (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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float RC = 1/(2*M_PI*20);
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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 ((fabs(_ki) > 0) && (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::reset_I()
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{
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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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void
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PID::load_gains()
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{
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_kp.load();
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_ki.load();
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_kd.load();
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}
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void
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PID::save_gains()
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{
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_kp.save();
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_ki.save();
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_kd.save();
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}
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