Newtonian physical activity monitor
First Claim
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1. An apparatus for monitoring posture and acceleration of a user, said apparatus being mountable to said user, comprising:
- a multi-axis sensor operative to sense gravity and acceleration along a plurality of axes by measuring a projection of an apparent gravity vector on each of said plurality of axes, the measured apparent gravity vector having a first component corresponding to an actual gravity vector and a second component corresponding to an acceleration vector;
at least one memory operative to store data representative of the measured apparent gravity vector; and
at least one processor operative to process the data stored in said at least one memory, said at least one processor being operative;
to calculate a representation of the measured apparent gravity vector;
to calculate a representation of said actual gravity vector corresponding to said first component of the measured apparent gravity vector, said actual gravity vector having a predetermined magnitude equal to 1 g;
to subtract said representation of said actual gravity vector from said representation of the measured apparent gravity vector to obtain a representation of said acceleration vector, said representation of said acceleration vector corresponding to said second component of the measured apparent gravity vector; and
to generate at least one indication of one or more of the posture of said user based at least upon a direction of said representation of said actual gravity vector corresponding to said first component of the measured apparent gravity vector, and the acceleration of said user based at least upon said representation of said acceleration vector corresponding to said second component of the measured apparent gravity vector.
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Abstract
An improved apparatus and methods of posture and physical activity monitoring. The apparatus is physically mountable to or associated with an object or person, includes a multi-axis accelerometer, and derives measurements of posture and of acceleration. Methods are disclosed which provide improved estimations of posture, acceleration, energy expenditure, movement characteristics and physical activity, detect the influence of externally-caused motion, and permit automatic calibration of the apparatus in the field.
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Citations
29 Claims
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1. An apparatus for monitoring posture and acceleration of a user, said apparatus being mountable to said user, comprising:
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a multi-axis sensor operative to sense gravity and acceleration along a plurality of axes by measuring a projection of an apparent gravity vector on each of said plurality of axes, the measured apparent gravity vector having a first component corresponding to an actual gravity vector and a second component corresponding to an acceleration vector; at least one memory operative to store data representative of the measured apparent gravity vector; and at least one processor operative to process the data stored in said at least one memory, said at least one processor being operative; to calculate a representation of the measured apparent gravity vector; to calculate a representation of said actual gravity vector corresponding to said first component of the measured apparent gravity vector, said actual gravity vector having a predetermined magnitude equal to 1 g; to subtract said representation of said actual gravity vector from said representation of the measured apparent gravity vector to obtain a representation of said acceleration vector, said representation of said acceleration vector corresponding to said second component of the measured apparent gravity vector; and to generate at least one indication of one or more of the posture of said user based at least upon a direction of said representation of said actual gravity vector corresponding to said first component of the measured apparent gravity vector, and the acceleration of said user based at least upon said representation of said acceleration vector corresponding to said second component of the measured apparent gravity vector. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of monitoring posture and acceleration of a user, comprising the steps of:
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sensing, by a multi-axis sensor mounted to said user, gravity and acceleration along a plurality of axes, wherein said sensing of said gravity and said acceleration includes measuring a projection of an apparent gravity vector on each of said plurality of axes, the measured apparent gravity vector having a first component corresponding to an actual gravity vector and a second component corresponding to an acceleration vector, said actual gravity vector having a predetermined magnitude equal to 1 g; subtracting said actual gravity vector corresponding to said first component of the measured apparent gravity vector from the measured apparent gravity vector to obtain said acceleration vector, said acceleration vector corresponding to said second component of the measured apparent gravity vector; and generating at least one indication of one or more of the posture of said user based at least upon a direction of said actual gravity vector corresponding to said first component of the measured apparent gravity vector, and the acceleration of said user based at least upon said acceleration vector corresponding to said second component of the measured apparent gravity vector. - View Dependent Claims (8, 9, 10, 11)
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12. A method of monitoring energy expended by a user, comprising the steps of;
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measuring an acceleration vector representing an acceleration of said user, said acceleration vector having a vertical component; performing one or more of a first calculating step and a second calculating step, wherein said first calculating step includes calculating a first amount of energy expended by said user based at least upon the measured acceleration vector, said first amount of energy corresponding to a change in kinetic energy of said user, and wherein said second calculating step includes calculating a second amount of energy expended by said user based at least upon said vertical component of said acceleration vector, said second amount of energy expended corresponding to a change in potential energy of said user; and generating an indication of an amount of total energy expended by said user based upon said calculated first and second amounts of energy. - View Dependent Claims (13, 14, 15)
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16. A method of calibrating an accelerometer, said accelerometer including a multi-axis sensor, said method comprising the steps of:
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measuring, by said multi-axis sensor during a specified time interval, an apparent gravity vector, said measured apparent gravity vector having a magnitude and a direction, thereby obtaining a plurality of samples of said apparent gravity vector during said specified time interval, wherein at least one axis of said multi-axis sensor has at least one associated offset and at least one associated gain, one or more of the at least one offset and the at least one gain of the at least one axis of said multi-axis sensor being proportional to at least one adjustable parameter; determining, from said plurality of samples of said apparent gravity vector, whether at least one characteristic of the measured apparent gravity vector is substantially unchanging during said specified time interval; and in the event said at least one characteristic of the measured apparent gravity vector is substantially unchanging during said specified time interval, adjusting said at least one adjustable parameter to adjust one or more of the at least one offset and the at least one gain of the at least one axis of said multi-axis sensor, thereby setting one or more of the magnitude of the measured apparent gravity vector to a first specified value and the direction of the measured apparent gravity vector to a second specified value. - View Dependent Claims (17, 18, 19)
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20. A method of monitoring an externally applied acceleration of a user, comprising the steps of:
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measuring an acceleration vector representing an acceleration of said user, the measured acceleration vector having a vertical component in a vertical direction, and at least one horizontal component in at least one horizontal direction; monitoring, during a specified time interval, one or more of a magnitude of said vertical component and at least one magnitude of said at least one horizontal component of the measured acceleration vector; and in the event one or more of the magnitude of said vertical component and the at least one magnitude of said at least one horizontal component of the measured acceleration vector remain in excess of at least one specified threshold value during said specified time interval, generating at least one signal to indicate a presence of said externally applied acceleration. - View Dependent Claims (21)
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22. A method of calibrating an accelerometer, said accelerometer including a multi-axis sensor, said method comprising the steps of:
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measuring, by said multi-axis sensor, an acceleration vector with reference to a plurality of axes to provide a plurality of analog sensor signals, each of said plurality of analog sensor signals representing a projection of said acceleration vector on a respective one of said plurality of axes, each of said plurality of analog sensor signals having an associated offset proportional to an adjustable parameter; for at least one of the respective analog sensor signals, adjusting said associated adjustable parameter to adjust the offset of the respective analog sensor signal; and converting each of the respective analog sensor signals to a corresponding digital sensor signal, wherein the digital sensor signal corresponding to at least one of the respective analog sensor signals has a dynamic range determined at least in part by the adjusted offset of the respective analog sensor signal. - View Dependent Claims (23)
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24. A method of monitoring energy expended by a user during a specified activity, comprising the steps of:
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measuring, by a sensor mounted to said user, an acceleration vector representing an acceleration of said user, the measured acceleration vector having a plurality of horizontal components;
determining a reference direction relative to said sensor, said reference direction lying in a horizontal plane; andcalculating a plurality of amounts of energy expended by said user based at least upon said plurality of horizontal components of the measured acceleration vector, respectively, each of said plurality of amounts of energy corresponding to a sum of changes in kinetic energy of said user in a respective one of a plurality of horizontal directions lying in said horizontal plane, each of said plurality of horizontal directions being defined relative to said reference direct on of said sensor. - View Dependent Claims (25, 26, 27, 28, 29)
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Specification