On Tuesday 05 February 2008, LeeE wrote:
> Thanks for the updates to xmlauto.cxx.
>
> As well as fixing the reload bug in cvs, the enabled tag for the
> filters is very useful.
>
> Would it be possible to add a null filter type i.e. a filter that
> acts as a simple pass-though?
Try the attached diff. This adds a new filter type named pass. It only needs
an input and an output. Something like this:
<filter>
<name>pass-through-filter</name>
<debug>false</debug>
<type>pass</type>
<input>/instrumentation/airspeed-indicator/indicated-speed-kt</input>
<output>/autopilot/KAP140/settings/airspeed-kt</output>
</filter>
> The reason I think this would be useful is that it would provide a
> very low-cost method of re-routing control inputs between different
> sub-systems and controllers - the sort of stuff you really need to
> do in Fly-By-Wire/Flight Control Systems.
>
> Also on my wish-list for this area would be the ability to change
> some of the pid controller parameters 'in-flight' without having to
> re-load the A/P e.g. reducing elevator control gain as airspeed
> increases. Because the resolution/frequency of the controllers is
> effectively limited by the frame-rate there can be practical
> difficulties in tuning a controller to work optimally over wide
> ranges such as you'd get with most of the fast jets - typically
> ~120-150kts during approach and landing up to 700kts (AFAIK YASim
> doesn't do supersonic so I don't try to seriously tune for the
> supersonic regime).
Thats an interesting thought. We could do soething like this:
<config>
<Kp prop="/autopilot/KAP140/settings/controller01-gain">10.0</Kp>
...
for the parameters that are to be exposed on the property tree. Any parameter
without the prop attribute gets a constant value as before. Nasal can be used
to change the value of the exposed parameters.
Another method could be:
<config>
<Kp>
<prop>/autopilot/KAP140/settings/controller01-gain</prop>
<value>10.0</value>
</Kp>
...
which is consistent with how it's done for the input to the PID controllers,
but this will break all autopilots.
> Just for info, while re-working the YF-23 I've been playing with
> using closed feedback loop pid controllers as flight surface and
> engine control drivers/servos with some good results:)
>
> The config below is what I'm using as an elevator input driver/servo
> (there's also an identical controller for elevator-trim input,
> aileron input, rudder input and throttle & reheat control inputs)
> and so far it's working pretty well here.
>
> <pid-controller>
> <name>Ruddervator Surface Driver</name>
> <debug>false</debug>
> <enable>
> <prop>/autopilot/FCS/locks/elevator</prop>
> <value>true</value>
> </enable>
> <input>
> <prop>/autopilot/FCS/controls/flight/elevator-norm</prop>
> </input>
> <reference>
> <prop>/autopilot/FCS/internal/target-elevator-norm</prop>
> </reference>
> <output>
> <prop>/autopilot/FCS/controls/flight/elevator-norm</prop>
> </output>
> <config>
> <Ts>0.05</Ts>
> <Kp>0.45</Kp>
> <beta>0.00001</beta>
> <alpha>0.1</alpha>
> <gamma>0.0</gamma>
> <Ti>0.05</Ti>
> <Td>0.0</Td>
> <u_min>-1.0</u_min>
> <u_max>1.0</u_max>
> </config>
> </pid-controller>
Of course now you can do that with a filter, which should be simpler an less
expensive.
--
Roy Vegard Ovesen
? xmlauto.diff
Index: xmlauto.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Autopilot/xmlauto.cxx,v
retrieving revision 1.28
diff -p -u -r1.28 xmlauto.cxx
--- xmlauto.cxx 4 Feb 2008 20:01:20 -0000 1.28
+++ xmlauto.cxx 5 Feb 2008 18:49:01 -0000
@@ -662,6 +662,8 @@ FGDigitalFilter::FGDigitalFilter(SGPrope
filterType = movingAverage;
} else if (cval == "noise-spike") {
filterType = noiseSpike;
+ } else if (cval == "pass") {
+ filterType = pass;
}
} else if ( cname == "input" ) {
input_prop = fgGetNode( child->getStringValue(), true );
@@ -683,11 +685,15 @@ FGDigitalFilter::FGDigitalFilter(SGPrope
void FGDigitalFilter::update(double dt)
{
- if ( input_prop != NULL &&
- enable_prop != NULL &&
- enable_prop->getStringValue() == enable_value) {
+ if ( (input_prop != NULL &&
+ enable_prop != NULL &&
+ enable_prop->getStringValue() == enable_value) ||
+ (enable_prop == NULL &&
+ input_prop != NULL) ) {
+
input.push_front(input_prop->getDoubleValue());
input.resize(samples + 1, 0.0);
+
if ( !enabled ) {
// first time being enabled, initialize output to the
// value of the output property to avoid bumping.
@@ -696,11 +702,6 @@ void FGDigitalFilter::update(double dt)
}
enabled = true;
- } else if (enable_prop == NULL &&
- input_prop != NULL) {
- input.push_front(input_prop->getDoubleValue());
- input.resize(samples + 1, 0.0);
- enabled = true;
} else {
enabled = false;
}
@@ -718,11 +719,6 @@ void FGDigitalFilter::update(double dt)
double alpha = 1 / ((Tf/dt) + 1);
output.push_front(alpha * input[0] +
(1 - alpha) * output[0]);
- unsigned int i;
- for ( i = 0; i < output_list.size(); ++i ) {
- output_list[i]->setDoubleValue( output[0] );
- }
- output.resize(1);
}
else if (filterType == doubleExponential)
{
@@ -730,21 +726,11 @@ void FGDigitalFilter::update(double dt)
output.push_front(alpha * alpha * input[0] +
2 * (1 - alpha) * output[0] -
(1 - alpha) * (1 - alpha) * output[1]);
- unsigned int i;
- for ( i = 0; i < output_list.size(); ++i ) {
- output_list[i]->setDoubleValue( output[0] );
- }
- output.resize(2);
}
else if (filterType == movingAverage)
{
output.push_front(output[0] +
(input[0] - input.back()) / samples);
- unsigned int i;
- for ( i = 0; i < output_list.size(); ++i ) {
- output_list[i]->setDoubleValue( output[0] );
- }
- output.resize(1);
}
else if (filterType == noiseSpike)
{
@@ -762,13 +748,18 @@ void FGDigitalFilter::update(double dt)
{
output.push_front(input[0]);
}
+ }
+ else if (filterType == pass)
+ {
+ output[0] = input[0];
+ }
- unsigned int i;
- for ( i = 0; i < output_list.size(); ++i ) {
- output_list[i]->setDoubleValue( output[0] );
- }
- output.resize(1);
+ unsigned int i;
+ for ( i = 0; i < output_list.size(); ++i ) {
+ output_list[i]->setDoubleValue( output[0] );
}
+ output.resize(1);
+
if (debug)
{
cout << "input:" << input[0]
Index: xmlauto.hxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Autopilot/xmlauto.hxx,v
retrieving revision 1.15
diff -p -u -r1.15 xmlauto.hxx
--- xmlauto.hxx 19 Jan 2008 18:06:05 -0000 1.15
+++ xmlauto.hxx 5 Feb 2008 18:49:01 -0000
@@ -240,7 +240,8 @@ private:
double rateOfChange; // The maximum allowable rate of change [1/s]
deque <double> output;
deque <double> input;
- enum filterTypes { exponential, doubleExponential, movingAverage,
noiseSpike };
+ enum filterTypes { exponential, doubleExponential, movingAverage,
+ noiseSpike, pass };
filterTypes filterType;
bool debug;-------------------------------------------------------------------------
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