Method for estimating velocities and/or displacements from accelerometer measurement samples
First Claim
1. A fall detector for detecting falls by a user, the fall detector comprising:
- an accelerometer for producing a time series of measurement samples representing the acceleration acting on the fall detector;
a transmitter for transmitting an alarm signal to summon assistance;
a processor for estimating a vertical velocity and/or vertical displacement of the fall detector from the measurement samples and using the estimated vertical velocity and/or vertical displacement to determine whether the user has suffered a fall;
wherein the processor is configured to estimate a vertical velocity and/or vertical displacement of the fall detector from the measurement samples by;
estimating a corresponding time series of unit vectors representing acceleration due to gravity in a reference frame of the accelerometer from the time series of measurement samples;
projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give a series of estimates for the vertical acceleration of the fall detector;
after projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give the series of estimates for the vertical acceleration of the fall detector, correcting the series of estimates to correct for excess acceleration due to sampling errors and/or clipping in the measurement samples including dividing the excess vertical acceleration across each of the series of estimates of the vertical acceleration in said time period to generate a corrected series of estimates of the vertical acceleration;
integrating the corrected series of estimates for the vertical acceleration to give a time series of values for the vertical velocity and/or vertical displacement of the fall detector,from the time series of values for the vertical velocity and/or vertical displacement, determining whether the user has fallen, andin response to determining that the user has fallen, causing the transmitter to transmit the alarm signal to summon assistance.
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Accused Products
Abstract
A fall detector includes an accelerometer for producing a time series of measurement samples representing the acceleration acting on the fall detector; a processor for estimating a vertical velocity and/or displacement of the fall detector from the measurement samples and using the estimated vertical velocity and/or displacement to determine whether the user has suffered a fall. The processor is configured to estimate a vertical velocity and/or displacement of the fall detector by estimating a corresponding time series of unit vectors representing acceleration due to gravity in the reference frame of the accelerometer from the time series of measurement samples; projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give a series of estimates for the vertical acceleration of the fall detector; and integrating the series of estimates to give a time series of values for the vertical velocity and/or displacement of the fall detector.
11 Citations
16 Claims
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1. A fall detector for detecting falls by a user, the fall detector comprising:
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an accelerometer for producing a time series of measurement samples representing the acceleration acting on the fall detector; a transmitter for transmitting an alarm signal to summon assistance; a processor for estimating a vertical velocity and/or vertical displacement of the fall detector from the measurement samples and using the estimated vertical velocity and/or vertical displacement to determine whether the user has suffered a fall;
wherein the processor is configured to estimate a vertical velocity and/or vertical displacement of the fall detector from the measurement samples by;estimating a corresponding time series of unit vectors representing acceleration due to gravity in a reference frame of the accelerometer from the time series of measurement samples; projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give a series of estimates for the vertical acceleration of the fall detector; after projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give the series of estimates for the vertical acceleration of the fall detector, correcting the series of estimates to correct for excess acceleration due to sampling errors and/or clipping in the measurement samples including dividing the excess vertical acceleration across each of the series of estimates of the vertical acceleration in said time period to generate a corrected series of estimates of the vertical acceleration; integrating the corrected series of estimates for the vertical acceleration to give a time series of values for the vertical velocity and/or vertical displacement of the fall detector, from the time series of values for the vertical velocity and/or vertical displacement, determining whether the user has fallen, and in response to determining that the user has fallen, causing the transmitter to transmit the alarm signal to summon assistance. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A fall detector for use in detecting falls by a user, the fall detector comprising:
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an accelerometer configured to produce a time series of measurement samples representing acceleration acting on the fall detector; a transmitter configured to transmit an alarm signal to a base station; a processor configured to estimate a vertical velocity and/or vertical displacement of the fall detector from the measurement samples by; estimating a corresponding time series of unit vectors representing acceleration due to gravity in a reference frame of the accelerometer from the time series of measurement samples; projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give a series of estimates for the vertical acceleration of the fall detector; integrating the series of estimates of the vertical acceleration in a time period in which the vertical acceleration is non-zero to generate an initial estimate of the vertical acceleration; when the initial estimate of the vertical acceleration is non-zero, a resulting non-zero amount being denoted an excess vertical acceleration; dividing the excess vertical acceleration across each of the series of estimates of the vertical acceleration in said time period to generate a series of refined estimates of the vertical acceleration; integrating the series of refined estimates of the vertical acceleration over the time period when the vertical acceleration and vertical velocity are non-zero to give a time series of values for the vertical velocity and/or vertical displacement corrected for the excess vertical acceleration of the fall detector; based on at least one of vertical velocity and/or the vertical displacement, determining whether the user has suffered a fall; and in response to determining that the user has suffered a fall, controlling the transmitter to transmit the alarm signal to the base station. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method for use in detecting falls by a user of a fall detector which includes an accelerometer, the method comprising:
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obtaining a time series of measurement samples from the accelerometer representing the acceleration acting on the fall detector; estimating a corresponding time series of unit vectors representing acceleration due to gravity in the reference frame of the accelerometer from the time series of measurement samples; projecting each measurement sample onto the corresponding unit vector and subtracting acceleration due to gravity to give a series of estimates for the vertical acceleration of the object; correcting the series of estimates to correct for excess acceleration due to sampling errors and/or clipping in the measured samples that occur when the fall detector has an impact including dividing the excess vertical acceleration across each estimate of the series of estimates of the vertical acceleration in said time period to generate a corrected series of estimates of the vertical acceleration; integrating the corrected series of estimates for the vertical acceleration over a time period to give a time series of values for the vertical velocity and/or vertical displacement of the object; using the estimated vertical velocity and/or vertical displacement to determine whether the user has suffered a fall; in response to determining that the user has suffered a fall, controlling a transmitter to transmit an alarm signal to a base station to summon help. - View Dependent Claims (14, 15, 16)
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Specification