Calibration of a chest-mounted wireless sensor device for posture and activity detection

A wireless sensor device, comprising:

• a processor;
• and
• a memory coupled to the processor, wherein the memory includes an application that, when executed by the processor, causes the processor to:
• transmit a signal to a relay device;
• in response to a determination, by the relay device, that the wireless sensor device is within a predetermined proximity from the relay device based on the transmitted signal, communicatively connect the wireless sensor device to the relay device, and receive a manual calibration request from the relay device,
• wherein the determination, by the relay device, that the wireless sensor device is within a predetermined proximity from the relay device is based on:
• a first determination, by the relay device, of a signal index from the transmitted signal,
• a second determination, by the relay device, of a threshold value for the signal index,
• a third determination, by the relay device, that the signal index equals or exceeds the threshold value;
• determine a vertical calibration vector using a manual calibration;
• and
• determine a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes,
• wherein the manual calibration request includes one of:
• an upright manual calibration request, a walking manual calibration request, or a bedridden user manual calibration request,
• wherein in response to the received manual calibration request is an upright manual calibration request, the determining the vertical calibration vector using the manual calibration includes:
• detecting a microelectromechanical systems (MEMS) based vertical calibration vector;
• filtering the MEMS based vertical calibration vector using a lowpass filter;
• replacing a current upright vertical calibration vector with the filtered MEMS based vertical calibration vector;
• and
• transmitting a status message to the relay device,
• wherein in response to the received manual calibration request is the walking manual calibration request, the determining the vertical calibration vector using the manual calibration includes:
• calculating a microelectromechanical systems (MEMS) based vertical calibration vector during a user's walking period;
• determining whether the walking period meets a minimum footstep number threshold;
• and
• transmitting a status message to the relay device, and
• wherein in response to the received manual calibration request is the bedridden user manual calibration request, the determining the vertical calibration vector using the manual calibration includes:
• determining both a supine calibration vector and a leaning calibration vector;
• calculating a microelectromechanical systems (MEMS) based vertical calibration vector based on the supine calibration vector and the leaning calibration vector;
• and
• transmitting a status message to the relay device.