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

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

what I finded in my app is that the EventDetector.threshold is
sensitive, if the value is improper set, and the result is error.

2011/6/4, beowulf zhang <beowulf.zhang@gmail.com>:
> I see, Thank You！
>
> 2011/6/4, MAISONOBE Luc <luc.maisonobe@c-s.fr>:
>> beowulf zhang <beowulf.zhang@gmail.com> a écrit :
>>
>>> I finded that the integrator called the class CombinedEventsManager
>>> and EventState of the common-math, not those in the orekit5. why?
>>
>> The NumericalPropagator in Orekit delegates everything to Apache
>> Commons Math, including events and step handling. It only add wrappers
>> to convert between the low level double arrays Apache Commons Math
>> uses and the higher level SpacecraftState and AbsoluteDate Orekit uses.
>>
>> The EventState class from Orekit is used by the non-numerical (i.e.
>> analytical) propagtors, since they do not rely on any service provided
>> by Apache Commons Math. The CombinedEventsDetectorsManager class is
>> obsolete and is not used anymore, we should remove it.
>>
>> Luc
>>
>>>
>>> 2011/5/31, 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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>>
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