mirror of https://github.com/ArduPilot/ardupilot
140 lines
3.6 KiB
C++
140 lines
3.6 KiB
C++
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
|
|
|
|
/// @file PID.cpp
|
|
/// @brief Generic PID algorithm
|
|
|
|
#include <math.h>
|
|
|
|
#include "PID.h"
|
|
#include <AP_HAL/AP_HAL.h>
|
|
#include <AP_Math/AP_Math.h>
|
|
|
|
extern const AP_HAL::HAL& hal;
|
|
|
|
const AP_Param::GroupInfo PID::var_info[] = {
|
|
|
|
// @Param: P
|
|
// @DisplayName: PID Proportional Gain
|
|
// @Description: P Gain which produces an output value that is proportional to the current error value
|
|
AP_GROUPINFO("P", 0, PID, _kp, 0),
|
|
|
|
// @Param: I
|
|
// @DisplayName: PID Integral Gain
|
|
// @Description: I Gain which produces an output that is proportional to both the magnitude and the duration of the error
|
|
AP_GROUPINFO("I", 1, PID, _ki, 0),
|
|
|
|
// @Param: D
|
|
// @DisplayName: PID Derivative Gain
|
|
// @Description: D Gain which produces an output that is proportional to the rate of change of the error
|
|
AP_GROUPINFO("D", 2, PID, _kd, 0),
|
|
|
|
// @Param: IMAX
|
|
// @DisplayName: PID Integral Maximum
|
|
// @Description: The maximum/minimum value that the I term can output
|
|
AP_GROUPINFO("IMAX", 3, PID, _imax, 0),
|
|
|
|
AP_GROUPEND
|
|
};
|
|
|
|
float PID::get_pid(float error, float scaler)
|
|
{
|
|
uint32_t tnow = AP_HAL::millis();
|
|
uint32_t dt = tnow - _last_t;
|
|
float output = 0;
|
|
float delta_time;
|
|
|
|
if (_last_t == 0 || dt > 1000) {
|
|
dt = 0;
|
|
|
|
// if this PID hasn't been used for a full second then zero
|
|
// the intergator term. This prevents I buildup from a
|
|
// previous fight mode from causing a massive return before
|
|
// the integrator gets a chance to correct itself
|
|
reset_I();
|
|
}
|
|
_last_t = tnow;
|
|
|
|
delta_time = (float)dt / 1000.0f;
|
|
|
|
// Compute proportional component
|
|
output += error * _kp;
|
|
|
|
// Compute derivative component if time has elapsed
|
|
if ((fabsf(_kd) > 0) && (dt > 0)) {
|
|
float derivative;
|
|
|
|
if (isnan(_last_derivative)) {
|
|
// we've just done a reset, suppress the first derivative
|
|
// term as we don't want a sudden change in input to cause
|
|
// a large D output change
|
|
derivative = 0;
|
|
_last_derivative = 0;
|
|
} else {
|
|
derivative = (error - _last_error) / delta_time;
|
|
}
|
|
|
|
// discrete low pass filter, cuts out the
|
|
// high frequency noise that can drive the controller crazy
|
|
float RC = 1/(2*M_PI*_fCut);
|
|
derivative = _last_derivative +
|
|
((delta_time / (RC + delta_time)) *
|
|
(derivative - _last_derivative));
|
|
|
|
// update state
|
|
_last_error = error;
|
|
_last_derivative = derivative;
|
|
|
|
// add in derivative component
|
|
output += _kd * derivative;
|
|
}
|
|
|
|
// scale the P and D components
|
|
output *= scaler;
|
|
|
|
// Compute integral component if time has elapsed
|
|
if ((fabsf(_ki) > 0) && (dt > 0)) {
|
|
_integrator += (error * _ki) * scaler * delta_time;
|
|
if (_integrator < -_imax) {
|
|
_integrator = -_imax;
|
|
} else if (_integrator > _imax) {
|
|
_integrator = _imax;
|
|
}
|
|
output += _integrator;
|
|
}
|
|
|
|
return output;
|
|
}
|
|
|
|
int16_t PID::get_pid_4500(float error, float scaler)
|
|
{
|
|
float v = get_pid(error, scaler);
|
|
return constrain_float(v, -4500, 4500);
|
|
}
|
|
|
|
void
|
|
PID::reset_I()
|
|
{
|
|
_integrator = 0;
|
|
// we use NAN (Not A Number) to indicate that the last
|
|
// derivative value is not valid
|
|
_last_derivative = NAN;
|
|
}
|
|
|
|
void
|
|
PID::load_gains()
|
|
{
|
|
_kp.load();
|
|
_ki.load();
|
|
_kd.load();
|
|
_imax.load();
|
|
}
|
|
|
|
void
|
|
PID::save_gains()
|
|
{
|
|
_kp.save();
|
|
_ki.save();
|
|
_kd.save();
|
|
_imax.save();
|
|
}
|