1 // digitalfilter.cxx - a selection of digital filters
3 // Written by Torsten Dreyer
4 // Based heavily on work created by Curtis Olson, started January 2004.
6 // Copyright (C) 2004 Curtis L. Olson - http://www.flightgear.org/~curt
7 // Copyright (C) 2010 Torsten Dreyer - Torsten (at) t3r (dot) de
9 // This program is free software; you can redistribute it and/or
10 // modify it under the terms of the GNU General Public License as
11 // published by the Free Software Foundation; either version 2 of the
12 // License, or (at your option) any later version.
14 // This program is distributed in the hope that it will be useful, but
15 // WITHOUT ANY WARRANTY; without even the implied warranty of
16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 // General Public License for more details.
19 // You should have received a copy of the GNU General Public License
20 // along with this program; if not, write to the Free Software
21 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
24 #include "digitalfilter.hxx"
25 #include "functor.hxx"
33 namespace FGXMLAutopilot {
39 class DigitalFilterImplementation : public SGReferenced {
41 virtual bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode) = 0;
43 virtual ~DigitalFilterImplementation() {}
44 DigitalFilterImplementation();
45 virtual void initialize( double output ) {}
46 virtual double compute( double dt, double input ) = 0;
47 bool configure( SGPropertyNode_ptr configNode );
49 void setDigitalFilter( DigitalFilter * digitalFilter ) { _digitalFilter = digitalFilter; }
52 DigitalFilter * _digitalFilter;
55 /* --------------------------------------------------------------------------------- */
56 /* --------------------------------------------------------------------------------- */
57 class GainFilterImplementation : public DigitalFilterImplementation {
59 InputValueList _gainInput;
60 bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode );
62 GainFilterImplementation() : _gainInput(1.0) {}
63 double compute( double dt, double input );
66 class ReciprocalFilterImplementation : public GainFilterImplementation {
68 double compute( double dt, double input );
71 class DerivativeFilterImplementation : public GainFilterImplementation {
72 InputValueList _TfInput;
74 bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode );
76 DerivativeFilterImplementation();
77 double compute( double dt, double input );
80 class ExponentialFilterImplementation : public GainFilterImplementation {
82 InputValueList _TfInput;
83 bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode );
85 double output_1, output_2;
87 ExponentialFilterImplementation();
88 double compute( double dt, double input );
89 virtual void initialize( double output );
92 class MovingAverageFilterImplementation : public DigitalFilterImplementation {
94 InputValueList _samplesInput;
96 std::deque <double> _inputQueue;
97 bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode );
99 MovingAverageFilterImplementation();
100 double compute( double dt, double input );
101 virtual void initialize( double output );
104 class NoiseSpikeFilterImplementation : public DigitalFilterImplementation {
107 InputValueList _rateOfChangeInput;
108 bool configure( const std::string & nodeName, SGPropertyNode_ptr configNode );
110 NoiseSpikeFilterImplementation();
111 double compute( double dt, double input );
112 virtual void initialize( double output );
115 /* --------------------------------------------------------------------------------- */
116 /* --------------------------------------------------------------------------------- */
118 } // namespace FGXMLAutopilot
120 using namespace FGXMLAutopilot;
122 /* --------------------------------------------------------------------------------- */
123 /* --------------------------------------------------------------------------------- */
124 DigitalFilterImplementation::DigitalFilterImplementation() :
129 bool DigitalFilterImplementation::configure( SGPropertyNode_ptr configNode )
131 for (int i = 0; i < configNode->nChildren(); ++i ) {
132 SGPropertyNode_ptr prop;
134 SGPropertyNode_ptr child = configNode->getChild(i);
135 string cname(child->getName());
137 if( configure( cname, child ) )
140 } // for configNode->nChildren()
145 /* --------------------------------------------------------------------------------- */
146 /* --------------------------------------------------------------------------------- */
148 double GainFilterImplementation::compute( double dt, double input )
150 return _gainInput.get_value() * input;
153 bool GainFilterImplementation::configure( const std::string & nodeName, SGPropertyNode_ptr configNode )
155 if (nodeName == "gain" ) {
156 _gainInput.push_back( new InputValue( configNode, 1 ) );
163 /* --------------------------------------------------------------------------------- */
164 /* --------------------------------------------------------------------------------- */
166 double ReciprocalFilterImplementation::compute( double dt, double input )
168 if( input >= -SGLimitsd::min() && input <= SGLimitsd::min() )
169 return SGLimitsd::max();
171 return _gainInput.get_value() / input;
175 /* --------------------------------------------------------------------------------- */
176 /* --------------------------------------------------------------------------------- */
178 DerivativeFilterImplementation::DerivativeFilterImplementation() :
183 bool DerivativeFilterImplementation::configure( const std::string & nodeName, SGPropertyNode_ptr configNode )
185 if( GainFilterImplementation::configure( nodeName, configNode ) )
188 if (nodeName == "filter-time" ) {
189 _TfInput.push_back( new InputValue( configNode, 1 ) );
196 double DerivativeFilterImplementation::compute( double dt, double input )
198 double output = (input - _input_1) * _TfInput.get_value() * _gainInput.get_value() / dt;
204 /* --------------------------------------------------------------------------------- */
205 /* --------------------------------------------------------------------------------- */
207 MovingAverageFilterImplementation::MovingAverageFilterImplementation() :
212 void MovingAverageFilterImplementation::initialize( double output )
217 double MovingAverageFilterImplementation::compute( double dt, double input )
219 std::deque<double>::size_type samples = _samplesInput.get_value();
220 _inputQueue.resize(samples+1, 0.0);
222 double output_0 = _output_1 + (input - _inputQueue.back()) / samples;
224 _output_1 = output_0;
225 _inputQueue.push_front(input);
229 bool MovingAverageFilterImplementation::configure( const std::string & nodeName, SGPropertyNode_ptr configNode )
231 if (nodeName == "samples" ) {
232 _samplesInput.push_back( new InputValue( configNode, 1 ) );
239 /* --------------------------------------------------------------------------------- */
240 /* --------------------------------------------------------------------------------- */
242 NoiseSpikeFilterImplementation::NoiseSpikeFilterImplementation() :
247 void NoiseSpikeFilterImplementation::initialize( double output )
252 double NoiseSpikeFilterImplementation::compute( double dt, double input )
254 double delta = input - _output_1;
255 if( fabs(delta) <= SGLimitsd::min() ) return input; // trivial
257 double maxChange = _rateOfChangeInput.get_value() * dt;
258 const PeriodicalValue * periodical = _digitalFilter->getPeriodicalValue();
259 if( periodical ) delta = periodical->normalizeSymmetric( delta );
261 if( fabs(delta) <= maxChange )
262 return (_output_1 = input);
264 return (_output_1 = _output_1 + copysign( maxChange, delta ));
267 bool NoiseSpikeFilterImplementation::configure( const std::string & nodeName, SGPropertyNode_ptr configNode )
269 if (nodeName == "max-rate-of-change" ) {
270 _rateOfChangeInput.push_back( new InputValue( configNode, 1 ) );
277 /* --------------------------------------------------------------------------------- */
278 /* --------------------------------------------------------------------------------- */
280 ExponentialFilterImplementation::ExponentialFilterImplementation()
281 : _isSecondOrder(false),
287 void ExponentialFilterImplementation::initialize( double output )
289 output_1 = output_2 = output;
292 double ExponentialFilterImplementation::compute( double dt, double input )
294 input = GainFilterImplementation::compute( dt, input );
295 double tf = _TfInput.get_value();
299 // avoid negative filter times
300 // and div by zero if -tf == dt
302 double alpha = tf > 0.0 ? 1 / ((tf/dt) + 1) : 1.0;
305 output_0 = alpha * alpha * input +
306 2 * (1 - alpha) * output_1 -
307 (1 - alpha) * (1 - alpha) * output_2;
309 output_0 = alpha * input + (1 - alpha) * output_1;
312 return (output_1 = output_0);
315 bool ExponentialFilterImplementation::configure( const std::string & nodeName, SGPropertyNode_ptr configNode )
317 if( GainFilterImplementation::configure( nodeName, configNode ) )
320 if (nodeName == "filter-time" ) {
321 _TfInput.push_back( new InputValue( configNode, 1 ) );
325 if (nodeName == "type" ) {
326 string type(configNode->getStringValue());
327 _isSecondOrder = type == "double-exponential";
333 /* --------------------------------------------------------------------------------- */
334 /* Digital Filter Component Implementation */
335 /* --------------------------------------------------------------------------------- */
337 DigitalFilter::DigitalFilter() :
339 _initializeTo(INITIALIZE_INPUT)
343 DigitalFilter::~DigitalFilter()
348 static map<string,FunctorBase<DigitalFilterImplementation> *> componentForge;
350 bool DigitalFilter::configure(const string& nodeName, SGPropertyNode_ptr configNode)
352 if( componentForge.empty() ) {
353 componentForge["gain"] = new CreateAndConfigureFunctor<GainFilterImplementation,DigitalFilterImplementation>();
354 componentForge["exponential"] = new CreateAndConfigureFunctor<ExponentialFilterImplementation,DigitalFilterImplementation>();
355 componentForge["double-exponential"] = new CreateAndConfigureFunctor<ExponentialFilterImplementation,DigitalFilterImplementation>();
356 componentForge["moving-average"] = new CreateAndConfigureFunctor<MovingAverageFilterImplementation,DigitalFilterImplementation>();
357 componentForge["noise-spike"] = new CreateAndConfigureFunctor<NoiseSpikeFilterImplementation,DigitalFilterImplementation>();
358 componentForge["reciprocal"] = new CreateAndConfigureFunctor<ReciprocalFilterImplementation,DigitalFilterImplementation>();
359 componentForge["derivative"] = new CreateAndConfigureFunctor<DerivativeFilterImplementation,DigitalFilterImplementation>();
362 SG_LOG( SG_AUTOPILOT, SG_BULK, "DigitalFilter::configure(" << nodeName << ")" << endl );
363 if( AnalogComponent::configure( nodeName, configNode ) )
366 if (nodeName == "type" ) {
367 string type( configNode->getStringValue() );
368 if( componentForge.count(type) == 0 ) {
369 SG_LOG( SG_AUTOPILOT, SG_BULK, "unhandled filter type <" << type << ">" << endl );
372 _implementation = (*componentForge[type])( configNode->getParent() );
373 _implementation->setDigitalFilter( this );
377 if( nodeName == "initialize-to" ) {
378 string s( configNode->getStringValue() );
380 _initializeTo = INITIALIZE_INPUT;
381 } else if( s == "output" ) {
382 _initializeTo = INITIALIZE_OUTPUT;
383 } else if( s == "none" ) {
384 _initializeTo = INITIALIZE_NONE;
386 SG_LOG( SG_AUTOPILOT, SG_WARN, "unhandled initialize-to value '" << s << "' ignored" );
391 SG_LOG( SG_AUTOPILOT, SG_BULK, "DigitalFilter::configure(" << nodeName << ") [unhandled]" << endl );
392 return false; // not handled by us, let the base class try
395 void DigitalFilter::update( bool firstTime, double dt)
397 if( _implementation == NULL ) return;
400 switch( _initializeTo ) {
402 case INITIALIZE_INPUT:
403 SG_LOG(SG_AUTOPILOT,SG_DEBUG, "First time initialization of " << get_name() << " to " << _valueInput.get_value() );
404 _implementation->initialize( _valueInput.get_value() );
407 case INITIALIZE_OUTPUT:
408 SG_LOG(SG_AUTOPILOT,SG_DEBUG, "First time initialization of " << get_name() << " to " << get_output_value() );
409 _implementation->initialize( get_output_value() );
413 SG_LOG(SG_AUTOPILOT,SG_DEBUG, "First time initialization of " << get_name() << " to (uninitialized)" );
418 double input = _valueInput.get_value() - _referenceInput.get_value();
419 double output = _implementation->compute( dt, input );
421 set_output_value( output );
424 cout << "input:" << input
425 << "\toutput:" << output << endl;