Classes
class	LatencyOutlierFilter
interface	LocalUptimeProvider
class	UptimeCalculationResult
Public Member Functions
void	calibrate (int sampleSize, double samplingDelayMillis)
double	toLocalUptime (double remoteUptime)
void	update ()
Static Public Member Functions
static RemoteUptimeClock	newDefault (final TimeProvider timeProvider, Callable< Double > callable, double driftSensitivity, double errorReductionCoefficientSensitivity, int latencyOutlierFilterSampleSize, double latencyOutlierFilterThreshold)
Package Functions
double	getDrift ()
double	getErrorReductionCoefficient ()
	RemoteUptimeClock (LocalUptimeProvider localUptimeProvider, Callable< Double > callable, double driftSensitivity, double errorReductionCoefficientSensitivity, int latencyOutlierFilterSampleSize, double latencyOutlierFilterThreshold)
Private Member Functions
double	calculateDrift (double localUptimeDelta, double remoteUptimeDelta)
UptimeCalculationResult	calculateNewUptime (Callable< Double > callable)
Private Attributes
final Callable< Double >	callable
double	drift
final double	driftSensitivity
double	errorReductionCoefficient
final double	errorReductionCoefficientSensitivity
final LatencyOutlierFilter	latencyOutlierFilter
double	localUptime
final LocalUptimeProvider	localUptimeProvider
double	measuredRemoteUptime
double	predictedRemoteUptime
Static Private Attributes
static final boolean	DEBUG = false
static final Log	log = LogFactory.getLog(RemoteUptimeClock.class)

Detailed Description

Author:: damonkohler@google.com (Damon Kohler)

Definition at line 35 of file RemoteUptimeClock.java.

Constructor & Destructor Documentation

org.ros.time.RemoteUptimeClock.RemoteUptimeClock	(	LocalUptimeProvider	localUptimeProvider,
		Callable< Double >	callable,
		double	driftSensitivity,
		double	errorReductionCoefficientSensitivity,
		int	latencyOutlierFilterSampleSize,
		double	latencyOutlierFilterThreshold
	)		`[inline, package]`

Definition at line 194 of file RemoteUptimeClock.java.

Member Function Documentation

double org.ros.time.RemoteUptimeClock.calculateDrift	(	double	localUptimeDelta,
		double	remoteUptimeDelta
	)		`[inline, private]`

See also:: drift

Parameters:

localUptimeDelta	the delta between the two local uptimes that correspond to the two remote uptimes used to determine remoteUptimeDelta
remoteUptimeDelta	the delta between the two remote uptimes that correspond to the two local uptimes used to determine localUptimeDelta

Returns:: the calculated drift

Definition at line 264 of file RemoteUptimeClock.java.

UptimeCalculationResult org.ros.time.RemoteUptimeClock.calculateNewUptime ( Callable< Double > callable ) [inline, private]

Creates a new UptimeCalculationResult where the local uptime has been adjusted to compensate for latency while retrieving the remote uptime.

Parameters:

callable returns the remote uptime as quickly as possible

Returns:: a new UptimeCalculationResult

Definition at line 333 of file RemoteUptimeClock.java.

void org.ros.time.RemoteUptimeClock.calibrate	(	int	sampleSize,
		double	samplingDelayMillis
	)		`[inline]`

Good calibration settings will depend on the remote uptime provider. In general, choosing a sample size around 10 and a delay that is large enough to include more than 100 uptime ticks will give reasonable results.

Parameters:

sampleSize	the number of samples to use for calibration
samplingDelayMillis	the delay in milliseconds between collecting each sample

Definition at line 219 of file RemoteUptimeClock.java.

double org.ros.time.RemoteUptimeClock.getDrift ( ) [inline, package]

Definition at line 362 of file RemoteUptimeClock.java.

double org.ros.time.RemoteUptimeClock.getErrorReductionCoefficient ( ) [inline, package]

Definition at line 367 of file RemoteUptimeClock.java.

static RemoteUptimeClock org.ros.time.RemoteUptimeClock.newDefault	(	final TimeProvider	timeProvider,
		Callable< Double >	callable,
		double	driftSensitivity,
		double	errorReductionCoefficientSensitivity,
		int	latencyOutlierFilterSampleSize,
		double	latencyOutlierFilterThreshold
	)		`[inline, static]`

The provided Callable should return the current measuredRemoteUptime of the remote clock with minimal overhead since the run time of this call will be used to further improve the estimation of measuredRemoteUptime.

Parameters:

timeProvider	the local time provider
callable	returns the current remote uptime in arbitrary units
driftSensitivity	the sensitivity to drift adjustments, must be in the range [0, 1]
errorReductionCoefficientSensitivity	the sensitivity to error reduction coefficient adjustments, must be in the range [0, 1]

Returns:: a new RemoteUptimeClock

Definition at line 180 of file RemoteUptimeClock.java.

double org.ros.time.RemoteUptimeClock.toLocalUptime ( double remoteUptime ) [inline]

Returns the estimated local uptime in seconds for the given remote uptime.

Parameters:

remoteUptime the remote uptime to convert to local uptime

Returns:: the estimated local uptime in seconds at the provided remote uptime

Definition at line 355 of file RemoteUptimeClock.java.

void org.ros.time.RemoteUptimeClock.update ( ) [inline]

Update this RemoteUptimeClock with the latest uptime from the remote clock.

This will update internal estimates of drift and error. Ideally, it should be called periodically with a consistent time interval between updates (e.g. 10 seconds).

Definition at line 278 of file RemoteUptimeClock.java.

Member Data Documentation

final Callable<Double> org.ros.time.RemoteUptimeClock.callable [private]

Definition at line 41 of file RemoteUptimeClock.java.

final boolean org.ros.time.RemoteUptimeClock.DEBUG = false [static, private]

Definition at line 37 of file RemoteUptimeClock.java.

double org.ros.time.RemoteUptimeClock.drift [private]

Drift is measured in local uptime ticks per remote uptime tick.

See also:: calculateDrift(double, double)

Definition at line 76 of file RemoteUptimeClock.java.

final double org.ros.time.RemoteUptimeClock.driftSensitivity [private]

Sensitivity values are used to sampleSize the effect of jitter. The value should be in the range [0, 1] where 0 indicates that the current estimate will never change (i.e. new measurements have no effect on estimates) and 1 indicates that previous estimates have no effect on changes to the current estimate.

Definition at line 51 of file RemoteUptimeClock.java.

double org.ros.time.RemoteUptimeClock.errorReductionCoefficient [private]

With drift alone, it is possible to accumulate a constant error that will never be corrected for. The errorReductionCoefficient is an additional term for removing this error.

Definition at line 83 of file RemoteUptimeClock.java.

final double org.ros.time.RemoteUptimeClock.errorReductionCoefficientSensitivity [private]