lejos.robotics.filter

Class OffsetCorrectionFilter

java.lang.Object

lejos.robotics.filter.AbstractFilter

lejos.robotics.filter.OffsetCorrectionFilter

All Implemented Interfaces:

SampleProvider

public class OffsetCorrectionFilter
extends AbstractFilter

The OffsetCorrectionFilter is used to correct sensors that have an unknown offset error.
The offset error is calculated by this class and then substracted from the sample to give a corrected sample. The filter works by calculating a running mean of a sample. this mean value is compared to the reference value, the difference between the two is the offset error. Not all samples are used to calculate the running mean. Only those samples that seem to indicate a stable (initial) situation are used for calculating the mean.

Author:

Aswin

Field Summary

Fields inherited from class lejos.robotics.filter.AbstractFilter

sampleSize, source

Constructor Summary

Constructors

Constructor and Description
OffsetCorrectionFilter(SampleProvider source) Constructor for the offset correction filter using default parameters.
OffsetCorrectionFilter(SampleProvider source, float[] reference) Constructor for the offset correction filter using default window of 200 samples.
OffsetCorrectionFilter(SampleProvider source, float[] reference, int bufferSize) Constructor for the offset correction filter. Constructor

Method Summary

Modifier and Type	Method and Description
void	fetchSample(float[] sample, int offset) Fetches a sample from a sensor or filter.
float[]	getMean() Returns the mean sample value
float[]	getStandardDeviation() Returns the standard deviation from the mean sample value
void	reset() Resets the filter

Methods inherited from class lejos.robotics.filter.AbstractFilter

sampleSize

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

OffsetCorrectionFilter

public OffsetCorrectionFilter(SampleProvider source)

Constructor for the offset correction filter using default parameters.
All samples are corrected to a reference value of zero using a window of 200 samples for calculating the mean

Parameters:

source - source for sample

OffsetCorrectionFilter

public OffsetCorrectionFilter(SampleProvider source,
                              float[] reference)

Constructor for the offset correction filter using default window of 200 samples.
All samples are corrected to the specified reference values

Parameters:

source - source for sample

reference - An array with reference values. The array length should match the sample size.

OffsetCorrectionFilter

public OffsetCorrectionFilter(SampleProvider source,
                              float[] reference,
                              int bufferSize)

Constructor for the offset correction filter.
Constructor

Parameters:

source - Source for sample

reference - An array with reference values. The array length should match the sample size.

bufferSize - Number of samples to use for calculating offset error

Method Detail

fetchSample

public void fetchSample(float[] sample,
                        int offset)

Description copied from interface: SampleProvider

Fetches a sample from a sensor or filter.

Specified by:

fetchSample in interface SampleProvider

Overrides:

fetchSample in class AbstractFilter

Parameters:

sample - The array to store the sample in.

offset - The elements of the sample are stored in the array starting at the offset position.

reset

public void reset()

Resets the filter

getMean

public float[] getMean()

Returns the mean sample value

Returns:

the mean sample value

getStandardDeviation

public float[] getStandardDeviation()

Returns the standard deviation from the mean sample value

Returns:

the standard deviation from the mean sample value