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, said 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 magnitude equal to 1 g;
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, from said representation of the measured apparent gravity vector and said magnitude of said actual gravity vector, a representation of said actual gravity vector said actual gravity vector having an associated direction;
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 acceleration vector having an associated magnitude and an associated direction; and
to generate at least one indication of one or more of the posture of said user based at least upon the direction of said actual gravity vector, and the acceleration of said user based at least upon the magnitude and the direction of said acceleration 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
32 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, said 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 magnitude equal to 1 g; 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, from said representation of the measured apparent gravity vector and said magnitude of said actual gravity vector, a representation of said actual gravity vector said actual gravity vector having an associated direction; 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 acceleration vector having an associated magnitude and an associated direction; and to generate at least one indication of one or more of the posture of said user based at least upon the direction of said actual gravity vector, and the acceleration of said user based at least upon the magnitude and the direction of said acceleration 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, said 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 magnitude equal to 1 g; calculating, by at least one processor, a representation of the measured apparent gravity vector; calculating, by said at least one processor from said representation of the measured apparent gravity vector and said magnitude of said actual gravity vector, a representation of said actual gravity vector, said actual gravity vector having an associated direction; subtracting, by said at least one processor, 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 acceleration vector having an associated magnitude and an associated direction; and generating at least one indication of one or more of the posture of said user based at least upon the direction of said actual gravity vector, and the acceleration of said user based at least upon the magnitude and the direction of said acceleration 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, by a multi-axis sensor, an acceleration vector representing an acceleration of said user, said acceleration vector having an associated magnitude and a vertical component; calculating, by at least one processor, from the measured acceleration vector and a vector representing actual gravity, said vertical component of said acceleration vector, the actual gravity vector having an associated direction, said vertical component of said acceleration vector having an associated magnitude and an associated direction, the direction of said vertical component of said acceleration vector corresponding to the direction of the actual gravity vector; in a first calculating step, calculating, by said at least one processor, a first amount of energy expended by said user based upon the magnitude of said acceleration vector, said first amount of energy corresponding to a change in kinetic energy of said user; in a second calculating step, calculating, by said at least one processor, a second amount of energy expended by said user based upon the magnitude of said vertical component of said acceleration vector, said second amount of energy 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 the calculated first and second amounts of energy. - View Dependent Claims (13, 14, 15, 16)
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17. 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 to obtain a plurality of samples of said apparent gravity vector during said specified time interval, said apparent gravity vector having an associated magnitude and an associated direction, 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; calculating, by at least one processor, the magnitude and the direction of said apparent gravity vector; determining, from said plurality of samples of said apparent gravity vector, whether the magnitude and the direction of said apparent gravity vector are substantially unchanging during said specified time interval; and in the event the magnitude and the direction of said apparent gravity vector are 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 said apparent gravity vector to a first specified value and the direction of said apparent gravity vector to a second specified value. - View Dependent Claims (18, 19, 20)
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21. A method of monitoring an externally applied acceleration of a user, comprising the steps of:
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measuring, by a multi-axis sensor, an acceleration vector representing an acceleration of said user, said acceleration vector having a vertical component and at least one horizontal component, each of said vertical component and said at least one horizontal component of said acceleration vector having an associated magnitude and an associated direction; calculating, by at least one processor from the measured acceleration vector and a vector representing actual gravity, said vertical component of said acceleration vector, the actual gravity vector having an associated direction, the direction of said vertical component of said acceleration vector corresponding to the direction of the actual gravity vector; calculating, by said at least one processor, the horizontal component of the measured acceleration vector; monitoring, during a specified time interval, one or more of the magnitude of said vertical component and the magnitude of the horizontal component of said acceleration vector; and in the event one or more of the magnitude of said vertical component and the magnitude of the horizontal component of said 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 (22, 23, 24)
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25. 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 apparent 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 apparent acceleration vector onto 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; converting, by at least one analog-to-digital converter, each of the respective analog sensor signals to a corresponding digital sensor signal, the analog-to-digital converter having an associated conversion range; and 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 so that the corresponding digital sensor signal lies within the conversion range of the respective analog-to-digital converter, wherein the corresponding digital sensor signal has a dynamic range based at least in part upon the adjusted offset of the respective analog sensor signal. - View Dependent Claims (26)
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27. A method of monitoring energy expended by a user in a plurality of horizontal directions during a specified time period and during performance of a specified activity, comprising the steps of:
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measuring, by a sensor mounted to said user, an apparent acceleration vector; calculating, by at least one processor, a gravity vector from the measured apparent acceleration vector; subtracting, by said at least one processor, the calculated gravity vector from said apparent acceleration vector to obtain an actual acceleration vector, said actual acceleration vector representing an acceleration of said user; defining a horizontal plane perpendicular to said gravity vector; determining a reference direction relative to said sensor, said reference direction lying in said horizontal plane; defining said plurality of horizontal directions relative to said reference direction of said sensor, said plurality of horizontal directions lying in said horizontal plane; projecting, during said specified time period, said actual acceleration vector onto said horizontal plane in said plurality of horizontal directions; and calculating, by said at least one processor, a plurality of amounts of energy expended by said user in said plurality of horizontal directions based upon the projection of said actual acceleration vector onto said horizontal plane in said plurality of horizontal directions, 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 said plurality of horizontal directions. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification