Re: [Orekit Users] My EventDetector class can't correct detecting event?

[beowulf zhang <beowulf.zhang@gmail.com>]

I find recursive in debug, stack is:

ClassicalRungeKuttaIntegrator(RungeKuttaIntegrator).integrate(FirstOrderDifferentialEquations,
double, double[], double, double[]) line: 172
NumericalPropagator.propagate(AbsoluteDate) line: 419	
NumericalPropagator.getPVCoordinates(AbsoluteDate, Frame) line: 462	
LocalOrbitalFrame.updateFrame(AbsoluteDate) line: 81	
EME2000Frame(Frame).getTransformTo(Frame, AbsoluteDate) line: 201	
EquinoctialOrbit(Orbit).getPVCoordinates(Frame) line: 240	
SpacecraftState.getPVCoordinates(Frame) line: 361	
CWAxisYDetector.g(SpacecraftState) line: 37	
AdaptedEventDetector.g(double, double[]) line: 74	
EventState.reinitializeBegin(double, double[]) line: 152	
CombinedEventsManager.evaluateStep(StepInterpolator) line: 142	
ClassicalRungeKuttaIntegrator(RungeKuttaIntegrator).integrate(FirstOrderDifferentialEquations,
double, double[], double, double[]) line: 172
NumericalPropagator.propagate(AbsoluteDate) line: 419	
SlaveMode.main(String[]) line: 138	

Maybe this is a debug!

2011/5/31, beowulf zhang <beowulf.zhang@gmail.com>:
> locOrbFrm object is referenced to another object.
>
> My main function code is:
>
>             // configure Orekit
>             Autoconfiguration.configureOrekit();
>
>             // Initial orbit parameters
>             double a = 7396159; // semi major axis in meters
>             double e = 0.001; // eccentricity
>             double i = Math.toRadians(7); // inclination
>             double omega = Math.toRadians(180); // perigee argument
>             double raan = Math.toRadians(261); // right ascension of
> ascending node
>             double lM = 0; // mean anomaly
>
>             // Inertial frame
>             Frame inertialFrame = FramesFactory.getEME2000();
>
>             // Initial date in UTC time scale
>             TimeScale utc = TimeScalesFactory.getUTC();
>             AbsoluteDate initialDate = new AbsoluteDate(2004, 01, 01,
> 23, 30, 00.000, utc);
>
>             // gravitation coefficient
>             double mu =  3.986004415e+14;
>
>
> //////////////////////////////////////////////////////////////////////////////////
>             // Orbit construction as Keplerian
>             Orbit initialOrbit = new KeplerianOrbit(a, e, i, omega, raan,
> lM,
>
> KeplerianOrbit.MEAN_ANOMALY,
>                                                     inertialFrame,
> initialDate, mu);
>
>             // Simple extrapolation with Keplerian motion
>             //KeplerianPropagator kepler = new
> KeplerianPropagator(initialOrbit);
>             double stepSize = 9;  // the step is ten seconds
>             FirstOrderIntegrator integrator = new
> ClassicalRungeKuttaIntegrator(stepSize);
>             NumericalPropagator prop = new NumericalPropagator(integrator);
>             SpacecraftState initialState = new
> SpacecraftState(initialOrbit);
>             prop.setInitialState(initialState);
>
>             // Set the propagator to slave mode (could be omitted as
> it is the default mode)
>             prop.setSlaveMode();
>
>             // 生成目标当地轨道系
>             LocalOrbitalFrame lof = new
> LocalOrbitalFrame(inertialFrame, LOFType.QSW, prop, "LOF");
>
>
> //////////////////////////////////////////////////////////////////////////////////
>             // 根据相对状态构造追踪星
>             PVCoordinates relSt = new PVCoordinates(new
> Vector3D(0.0,0.0,0.0),
>             										new Vector3D(0.0,1.0,0.0));
>             PVCoordinates initPV = lof.getTransformTo(inertialFrame,
>             										  initialDate).transformPVCoordinates(relSt);
>
>             // Simple extrapolation with Keplerian motion
>             //KeplerianPropagator kepler = new
> KeplerianPropagator(initialOrbit);
>             FirstOrderIntegrator integratorS = new
> ClassicalRungeKuttaIntegrator(stepSize);
>             NumericalPropagator propS = new
> NumericalPropagator(integratorS);
>             SpacecraftState initialStateS = new SpacecraftState(new
> CartesianOrbit(initPV,
>             		inertialFrame, initialDate, mu));
>             propS.setInitialState(initialStateS);
>
>             // Set the propagator to slave mode (could be omitted as
> it is the default mode)
>             propS.setSlaveMode();
>             propS.addEventDetector(new CWAxisYDetector(initialOrbit,
> lof, initialDate));
>
>
> //////////////////////////////////////////////////////////////////////////////////
>             // Overall duration in seconds for extrapolation
>             double duration = initialOrbit.getKeplerianPeriod() * 2.0;
>
>             PrintWriter relFile = null;
>             try {
> 				relFile = new PrintWriter("relst.txt");
> 			} catch (FileNotFoundException e1) {
> 				e1.printStackTrace();
> 			}
>
>             // Stop date
>             final AbsoluteDate finalDate =  new
> AbsoluteDate(initialDate, duration, utc);
>
>             // Extrapolation loop
>             boolean first = true;
>             AbsoluteDate extrapDate = initialDate;
>             while (extrapDate.compareTo(finalDate) <= 0)  {
>
>                 SpacecraftState targ = prop.propagate(extrapDate);
>                 SpacecraftState inter = propS.propagate(extrapDate);
>                 PVCoordinates relst = inter.getPVCoordinates(lof);
>                 double tm = extrapDate.durationFrom(initialDate);
>                 relFile.printf("%f %f %f %f\n",
>                 		tm, relst.getPosition().getX(),
> relst.getPosition().getY(), relst.getPosition().getZ());
>
>                 extrapDate = new AbsoluteDate(extrapDate, stepSize, utc);
>             }
>
>             relFile.close();
>             System.out.println("The End");
>
>
> 2011/5/31, MAISONOBE Luc <luc.maisonobe@c-s.fr>:
>> beowulf zhang <beowulf.zhang@gmail.com> a écrit :
>>
>>> I write a class CWAxisYDetector derived from AbstractDetector, the code
>>> is:
>>>
>>> public class CWAxisYDetector extends AbstractDetector {
>>>
>>> 	private LocalOrbitalFrame locOrbFrm;
>>>
>>> 	private AbsoluteDate initDate;
>>>
>>> 	protected CWAxisYDetector(Orbit targOrb, LocalOrbitalFrame lof,
>>> AbsoluteDate iDate) {
>>> 		super(targOrb.getKeplerianPeriod() / 3, 1.0e-13 *
>>> targOrb.getKeplerianPeriod());
>>> 		this.locOrbFrm = lof;
>>> 		this.initDate = iDate;
>>> 	}
>>>
>>> 	public int eventOccurred(SpacecraftState s, boolean increasing)
>>> 			throws OrekitException {
>>> 		System.out.println(s.getDate().durationFrom(initDate));
>>> 		return CONTINUE;
>>> 	}
>>>
>>> 	public double g(SpacecraftState s) throws OrekitException {
>>> 		return s.getPVCoordinates(locOrbFrm).getPosition().getX();
>>> 	}
>>
>> If the local orbital frame here is linked to the same spacecraft whose
>> orbit is propagated, then
>> s.getPVCoordinates(locOrbFrm).getPosition().getX() should always be 0
>> (as well as Y and Z since the spacecraft defines the origin of this
>> frame).
>> So the function is essentially an observation of numerical errors in
>> interpolation polynomials, it is not a function that clearly crosses
>> the zero axis at one precise time.
>>
>> Are you sure about the frame ? Shouldn't it be related to another
>> spacecraft (for relative motion observation for example) ?
>>
>> Luc
>>
>>>
>>> }
>>>
>>> but this class can't correct detecting event, and in some integrate
>>> step getinig error information:
>>>
>>> Exception in thread "main"
>>> org.apache.commons.math.MathRuntimeException$4: function values at
>>> endpoints do not have different signs.  Endpoints: [0.539, 0.539],
>>> Values: [0, 0]
>>> 	at
>>> org.apache.commons.math.MathRuntimeException.createIllegalArgumentException(MathRuntimeException.java:305)
>>> 	at
>>> org.apache.commons.math.analysis.solvers.BrentSolver.solve(BrentSolver.java:219)
>>> 	at
>>> org.apache.commons.math.ode.events.EventState.evaluateStep(EventState.java:229)
>>> 	at
>>> org.apache.commons.math.ode.events.CombinedEventsManager.evaluateStep(CombinedEventsManager.java:152)
>>> 	at
>>> org.apache.commons.math.ode.nonstiff.RungeKuttaIntegrator.integrate(RungeKuttaIntegrator.java:172)
>>> 	at
>>> org.orekit.propagation.numerical.NumericalPropagator.propagate(NumericalPropagator.java:419)
>>> 	at fr.cs.examples.propagation.SlaveMode.main(SlaveMode.java:136)
>>>
>>> why?
>>>
>>>
>>
>>
>>
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>>
>>
>>
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