Dynamic IMU calibration and sensor fusion

A non-transitory computer storage medium that stores a program thereon that causes a computer to execute a process comprising:

• receiving initial IMU data from an inertial measurement unit (IMU) of a wearable health monitoring device having one or more physiological sensors outputting physiological sensor data, the initial IMU data comprising raw accelerometer data, raw gyroscope data, and raw magnetometer data;
• performing sensor calibration using the initial IMU data to calculate a plurality of initial IMU calibration parameters;
• using the plurality of initial IMU calibration parameters, by a sensor fusion module, to calculate an initial estimated orientation of the wearable health monitoring device;
• using the initial estimated orientation, by a gravity removal module, to calculate initial linear acceleration data indicative of the past linear acceleration of the wearable health monitoring device;
• using the past linear acceleration of the wearable health monitoring device to remove motion artifacts from the physiological sensor data output by the wearable health monitoring device;
• storing the initial IMU calibration parameters and the past linear acceleration of the wearable health monitoring device;
• receiving updated IMU data from the IMU of the wearable health monitoring device;
• using the updated IMU data to calculate updated IMU calibration parameters;
• and
• using the updated IMU calibration parameters to back-calibrate linear acceleration data indicative of the past linear acceleration of the wearable health monitoring device.