Calibration of a chest-mounted wireless sensor device for posture and activity detection
First Claim
1. A method to calibrate a wireless sensor device, comprising:
- determining a first section and a second section of a rotation matrix algorithm to line up native axes of the wireless sensor device with body axes,wherein the first section of the rotation matrix algorithm includes;
determining a first vertical calibration vector in a first frame of reference,calculating, by the wireless sensor device, a new horizontal axis using the first vertical calibration vector,calculating, by the wireless sensor device, a first cross product of a native horizontal X-axis and the new horizontal axis,calculating a first rotation angle using the first cross product, andcalculating a first rotation matrix using the first rotation angle,wherein the second section of the rotation matrix algorithm includes;
calculating a second vertical calibration vector in a second frame of reference,calculating a new vertical axis using the second vertical calibration vector,calculating a second cross product of the second calibration vector and the new vertical axis,calculating a second rotation angle using the second cross product, andcalculating a second rotation matrix using the second rotation angle;
rotating, in accordance with the first rotation matrix of the first section of a rotation matrix algorithm, a native accelerometer X-axis of the wireless sensor device to align horizontally with a medial-lateral (ML) axis of a body; and
rotating, in accordance with the second rotation matrix of the second section of the rotation matrix algorithm, a native accelerometer Y-axis of the wireless sensor device to align vertically with a vertical (VT) axis of the body.
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Abstract
A method and system for calibrating a wireless sensor device are disclosed. In a first aspect, the method comprises determining a vertical calibration vector and determining a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes. In a second aspect, a wireless sensor device comprises a processor and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to determine a vertical calibration vector and to determine a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes.
22 Citations
18 Claims
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1. A method to calibrate a wireless sensor device, comprising:
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determining a first section and a second section of a rotation matrix algorithm to line up native axes of the wireless sensor device with body axes, wherein the first section of the rotation matrix algorithm includes; determining a first vertical calibration vector in a first frame of reference, calculating, by the wireless sensor device, a new horizontal axis using the first vertical calibration vector, calculating, by the wireless sensor device, a first cross product of a native horizontal X-axis and the new horizontal axis, calculating a first rotation angle using the first cross product, and calculating a first rotation matrix using the first rotation angle, wherein the second section of the rotation matrix algorithm includes; calculating a second vertical calibration vector in a second frame of reference, calculating a new vertical axis using the second vertical calibration vector, calculating a second cross product of the second calibration vector and the new vertical axis, calculating a second rotation angle using the second cross product, and calculating a second rotation matrix using the second rotation angle; rotating, in accordance with the first rotation matrix of the first section of a rotation matrix algorithm, a native accelerometer X-axis of the wireless sensor device to align horizontally with a medial-lateral (ML) axis of a body; and rotating, in accordance with the second rotation matrix of the second section of the rotation matrix algorithm, a native accelerometer Y-axis of the wireless sensor device to align vertically with a vertical (VT) axis of the body. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method to calibrate a wireless sensor device, comprising:
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determining a vertical calibration vector using a manual calibration vector; determining a first section of a rotation matrix algorithm that enables rotation of an X-axis of an accelerometer of the wireless sensor device to line up with a horizontal plane of a body by using the vertical calibration vector; rotating, in accordance with the first section of a rotation matrix algorithm, the X-axis of the accelerometer of the wireless sensor device to align horizontally with the horizontal plane of the body for calibration that constitutes a first rotation matrix; determining a second section of the rotation matrix algorithm that enables rotation of a Y-axis of the accelerometer of the wireless sensor device to line up a vertical (VT) axis of the body; and rotating, in accordance with the second section of rotation matrix algorithm, the Y-axis of the accelerometer of the wireless sensor device to align vertically with the VT axis of the body for calibration that constitutes a second rotation matrix. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification