299 lines
8.5 KiB
C++
299 lines
8.5 KiB
C++
// pidcontroller.cxx - implementation of PID controller
|
|
//
|
|
// Written by Torsten Dreyer
|
|
// Based heavily on work created by Curtis Olson, started January 2004.
|
|
//
|
|
// Copyright (C) 2004 Curtis L. Olson - http://www.flightgear.org/~curt
|
|
// Copyright (C) 2010 Torsten Dreyer - Torsten (at) t3r (dot) de
|
|
//
|
|
// This program is free software; you can redistribute it and/or
|
|
// modify it under the terms of the GNU General Public License as
|
|
// published by the Free Software Foundation; either version 2 of the
|
|
// License, or (at your option) any later version.
|
|
//
|
|
// This program is distributed in the hope that it will be useful, but
|
|
// WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU General Public License
|
|
// along with this program; if not, write to the Free Software
|
|
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
|
|
//
|
|
|
|
#include "pidcontroller.hxx"
|
|
|
|
using namespace FGXMLAutopilot;
|
|
|
|
using std::endl;
|
|
using std::cout;
|
|
|
|
PIDController::PIDController():
|
|
AnalogComponent(),
|
|
alpha( 0.1 ),
|
|
beta( 1.0 ),
|
|
gamma( 0.0 ),
|
|
ep_n_1( 0.0 ),
|
|
edf_n_1( 0.0 ),
|
|
edf_n_2( 0.0 ),
|
|
u_n_1( 0.0 ),
|
|
desiredTs( 0.0 ),
|
|
elapsedTime( 0.0 ),
|
|
startup_current( false ),
|
|
startup_its( 0 ),
|
|
iteration( 0 )
|
|
{
|
|
}
|
|
|
|
/*
|
|
* Roy Vegard Ovesen:
|
|
*
|
|
* Ok! Here is the PID controller algorithm that I would like to see
|
|
* implemented:
|
|
*
|
|
* delta_u_n = Kp * [ (ep_n - ep_n-1) + ((Ts/Ti)*e_n)
|
|
* + (Td/Ts)*(edf_n - 2*edf_n-1 + edf_n-2) ]
|
|
*
|
|
* u_n = u_n-1 + delta_u_n
|
|
*
|
|
* where:
|
|
*
|
|
* delta_u : The incremental output
|
|
* Kp : Proportional gain
|
|
* ep : Proportional error with reference weighing
|
|
* ep = beta * r - y
|
|
* where:
|
|
* beta : Weighing factor
|
|
* r : Reference (setpoint)
|
|
* y : Process value, measured
|
|
* e : Error
|
|
* e = r - y
|
|
* Ts : Sampling interval
|
|
* Ti : Integrator time
|
|
* Td : Derivator time
|
|
* edf : Derivate error with reference weighing and filtering
|
|
* edf_n = edf_n-1 / ((Ts/Tf) + 1) + ed_n * (Ts/Tf) / ((Ts/Tf) + 1)
|
|
* where:
|
|
* Tf : Filter time
|
|
* Tf = alpha * Td , where alpha usually is set to 0.1
|
|
* ed : Unfiltered derivate error with reference weighing
|
|
* ed = gamma * r - y
|
|
* where:
|
|
* gamma : Weighing factor
|
|
*
|
|
* u : absolute output
|
|
*
|
|
* Index n means the n'th value.
|
|
*
|
|
*
|
|
* Inputs:
|
|
* enabled ,
|
|
* y_n , r_n , beta=1 , gamma=0 , alpha=0.1 ,
|
|
* Kp , Ti , Td , Ts (is the sampling time available?)
|
|
* u_min , u_max
|
|
*
|
|
* Output:
|
|
* u_n
|
|
*/
|
|
|
|
void PIDController::update( bool firstTime, double dt )
|
|
{
|
|
elapsedTime += dt;
|
|
if (firstTime) {
|
|
iteration = 0;
|
|
/* We always initialise edf_n_1 to zero, regardless of startup_its. */
|
|
edf_n_1 = 0;
|
|
}
|
|
else if (elapsedTime <= desiredTs ) {
|
|
// do nothing if not enough time has passed.
|
|
return;
|
|
}
|
|
|
|
iteration += 1;
|
|
|
|
/* We are going to do an iteration so reset elapsedTime. */
|
|
double Ts = elapsedTime;
|
|
elapsedTime = 0.0;
|
|
|
|
/* Read generic things from our AnalogComponent base class. */
|
|
double y_n = _valueInput.get_value(); // input.
|
|
double r_n = _referenceInput.get_value(); // reference.
|
|
double u_min = _minInput.get_value(); // minimum output.
|
|
double u_max = _maxInput.get_value(); // maximum output.
|
|
|
|
/* Read things specific to PIDController. */
|
|
double td = Td.get_value(); // derivative time.
|
|
double ti = Ti.get_value(); // (reciprocal?) integral time.
|
|
|
|
/*
|
|
Now do the PID calculations.
|
|
*/
|
|
|
|
double ep_n = beta * r_n - y_n; // proportional error.
|
|
double e_n = r_n - y_n; // error.
|
|
double ed_n = gamma * r_n - y_n; // derivate error.
|
|
double Tf = alpha * td; // filter time.
|
|
|
|
double edf_n = 0.0; // derivate error.
|
|
if (td > 0.0) {
|
|
edf_n = edf_n_1 / (Ts/Tf + 1)
|
|
+ ed_n * (Ts/Tf) / (Ts/Tf + 1);
|
|
}
|
|
|
|
if (firstTime) {
|
|
if (startup_current) {
|
|
/* Seed our historical state with current values. This avoids spurious
|
|
large terms in calculation of delta_u_n below. */
|
|
ep_n_1 = ep_n;
|
|
edf_n_2 = edf_n;
|
|
edf_n_1 = edf_n;
|
|
}
|
|
else {
|
|
// Default behaviour.
|
|
ep_n_1 = 0;
|
|
edf_n_2 = 0;
|
|
// edf_n_1 is already set to zero above.
|
|
}
|
|
u_n_1 = get_output_value();
|
|
}
|
|
|
|
double delta_u_n = 0.0; // incremental output
|
|
if ( ti > 0.0 ) {
|
|
delta_u_n = Kp.get_value() * (
|
|
(ep_n - ep_n_1)
|
|
+ ((Ts/ti) * e_n)
|
|
+ ((td/Ts) * (edf_n - 2*edf_n_1 + edf_n_2))
|
|
);
|
|
}
|
|
|
|
const char* saturation = "";
|
|
double u_n; // absolute output
|
|
|
|
if (iteration > startup_its) {
|
|
|
|
/* Update the output, clipping to u_min..u_max. */
|
|
|
|
u_n = u_n_1 + delta_u_n;
|
|
|
|
if (u_n > u_max) {
|
|
u_n = u_max;
|
|
saturation = " max_saturation";
|
|
}
|
|
else if (u_n < u_min) {
|
|
u_n = u_min;
|
|
saturation = " min_saturation";
|
|
}
|
|
set_output_value( u_n );
|
|
}
|
|
else {
|
|
/* Do not change the output. Instead get the current output value for
|
|
use in setting our historical state below. */
|
|
if (_debug) {
|
|
cout << subsystemId()
|
|
<< ": doing nothing."
|
|
<< " startup_its=" << startup_its
|
|
<< " iteration=" << iteration
|
|
<< std::endl;
|
|
}
|
|
u_n = get_output_value();
|
|
}
|
|
|
|
if ( _debug ) {
|
|
cout
|
|
<< "Updating " << subsystemId()
|
|
<< " startup_its=" << startup_its
|
|
<< " startup_current=" << startup_current
|
|
<< " firstTime=" << firstTime
|
|
<< " iteration=" << iteration
|
|
<< " Ts=" << Ts
|
|
<< " input=" << y_n
|
|
<< " ref=" << r_n
|
|
<< " ep_n=" << ep_n
|
|
<< " ep_n_1=" << ep_n_1
|
|
<< " e_n=" << e_n
|
|
<< " ed_n=" << ed_n
|
|
<< " Tf=" << Tf
|
|
<< " edf_n=" << edf_n
|
|
<< " edf_n_1=" << edf_n_1
|
|
<< " edf_n_2=" << edf_n_2
|
|
<< " ti=" << ti
|
|
<< " delta_u_n=" << delta_u_n
|
|
<< " P=" << Kp.get_value() * (ep_n - ep_n_1)
|
|
<< " I=" << Kp.get_value() * ((Ts/ti) * e_n)
|
|
<< " D=" << Kp.get_value() * ((td/Ts) * (edf_n - 2*edf_n_1 + edf_n_2))
|
|
<< saturation
|
|
<< " u_n_1=" << u_n_1
|
|
<< " delta_u_n=" << delta_u_n
|
|
<< " output=" << u_n
|
|
<< std::endl;
|
|
}
|
|
|
|
// Updates indexed values;
|
|
u_n_1 = u_n;
|
|
ep_n_1 = ep_n;
|
|
edf_n_2 = edf_n_1;
|
|
edf_n_1 = edf_n;
|
|
}
|
|
|
|
//------------------------------------------------------------------------------
|
|
bool PIDController::configure( SGPropertyNode& cfg_node,
|
|
const std::string& cfg_name,
|
|
SGPropertyNode& prop_root )
|
|
{
|
|
if( cfg_name == "config" ) {
|
|
Component::configure(prop_root, cfg_node);
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "Ts") {
|
|
desiredTs = cfg_node.getDoubleValue();
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "Kp") {
|
|
Kp.push_back( new InputValue(prop_root, cfg_node) );
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "Ti") {
|
|
Ti.push_back( new InputValue(prop_root, cfg_node) );
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "Td") {
|
|
Td.push_back( new InputValue(prop_root, cfg_node) );
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "beta") {
|
|
beta = cfg_node.getDoubleValue();
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "alpha") {
|
|
alpha = cfg_node.getDoubleValue();
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "gamma") {
|
|
gamma = cfg_node.getDoubleValue();
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "startup-its") {
|
|
startup_its = cfg_node.getIntValue();
|
|
return true;
|
|
}
|
|
|
|
if (cfg_name == "startup-current") {
|
|
startup_current = cfg_node.getBoolValue();
|
|
return true;
|
|
}
|
|
|
|
return AnalogComponent::configure(cfg_node, cfg_name, prop_root);
|
|
}
|
|
|
|
|
|
// Register the subsystem.
|
|
SGSubsystemMgr::Registrant<PIDController> registrantPIDController;
|