Systems and methods for determining swimming metrics

1. A method for improving an accuracy of a wearable device while determining swimming metrics of a user during a swimming session, the method comprising:

receiving, by a processor circuit of the wearable device, motion data from one or more motion sensors of the wearable device;

determining, by the processor circuit using the motion data, a first set of rotational data of the wearable device, wherein the first set of rotational data is expressed in a first frame of reference;

converting, by the processor circuit, the first set of rotational data into a second set of rotational data, wherein the second set of rotational data is expressed in a second frame of reference;

determining, by the processor circuit, one or more swimming metrics of the user based on the second set of rotational data, where determining the one or more swimming metrics includes:

detecting a number of turns and a number of strokes of the user during the swimming session based on the received motion data;

determining a number of strokes per lap based on the number of turns and the number of strokes;

determining a variance of the number of strokes per lap;

adjusting the number of turns to reduce the variance of the number of strokes per lap;

determining a lap count of the user based on the adjusted number of turns; and

outputting, by the processor circuit, the one or more swimming metrics of the user.

2. The method of claim 1 , wherein detecting a number of turns further comprises:

determining whether a turn is not detected; and

inserting a missing turn in the number of turns in response to a determination that a turn is not detected.

3. The method of claim 2 , wherein determining whether a turn is not detected comprises:

determining a stroke range per lap; and

comparing the number of strokes between two consecutive turns with the determined stroke range per lap.

4. The method of claim 2 , wherein determining whether a turn is not detected comprises:

comparing the number of strokes between two consecutive turns with a threshold, wherein the threshold is determined by multiplying a mean value of the number of strokes per lap with a ratio.

5. The method of claim 1 , further comprising:

determining whether the number of strokes made by the user converges in the swimming session; or

determining whether the number of strokes made by the user converges in a historical swimming session.

6. The method of claim 5 , wherein determining whether the number of strokes made by the user converges in the swimming session comprises:

determining a standard deviation of the number of strokes among consecutive turns; and

comparing the standard deviation with a threshold.

7. The method of claim 6 , wherein the threshold is 1.5 strokes.

8. The method of claim 1 , wherein the first frame of reference comprises a body-fixed frame of reference with respect to the wearable device.

9. The method of claim 1 , wherein the second frame of reference comprises an inertial frame of reference.

10. A method comprising:

receiving, by a processor circuit of a wearable device worn on a wrist of a user during a swimming session, motion data from one or more motion sensors of the wearable device;

determining, by the processor circuit using the motion data, a first set of rotational data of the wearable device, wherein the first set of rotational data is expressed in a first frame of reference;

converting, by the processor circuit, the first set of rotational data into a second set of rotational data, wherein the second set of rotational data is expressed in a second frame of reference, and wherein the second set of rotational data includes data indicative of the user's arm or wrist movements;

determining, by the processor circuit, one or more swimming metrics of the user based on the second set of rotational data, where determining the one or more swimming metrics includes:

detecting a number of turns and a number of strokes of the user during the swimming session based on the received motion data;

determining a number of strokes per lap based on the number of turns and the number of strokes;

determining a variance of the number of strokes per lap;

adjusting the number of turns to reduce the variance of the number of strokes per lap;

determining a lap count of the user based on the adjusted number of turns; and

outputting, by the processor circuit, the one or more swimming metrics of the user.

11. The method of claim 10 , further comprising:

determining whether the number of strokes of the user converges in the swimming session; or

determining whether the number of strokes made by the user converges in a historical swimming session.

12. The method of claim 11 , wherein determining whether the number of strokes of the user converges in the swimming session comprises:

determining a standard deviation of the number of strokes among consecutive turns; and

comparing the standard deviation with a threshold.

13. The method of claim 12 , wherein the threshold is 1.5 strokes.

14. The method of claim 11 , wherein determining whether a turn is not detected comprises:

determining a stroke range per lap; and

comparing the number of strokes between two consecutive turns with the determined stroke range per lap.

15. The method of claim 11 , wherein determining whether a turn is not detected comprises:

comparing the number of strokes between two consecutive turns with a threshold, wherein the threshold is determined by multiplying a mean value of the number of strokes per lap with a ratio.

16. The method of claim 10 , wherein the first frame of reference comprises a body-fixed frame of reference with respect to the wearable device.

17. The method of claim 10 , wherein the second frame of reference comprises an inertial frame of reference.

18. The method of claim 10 , wherein detecting a number of turns further comprises:

determining whether a turn is not detected; and

inserting a missing turn in the number of turns in response to a determination that a turn is not detected.

19. A system for improving an accuracy of a wearable device while determining one or more swimming metrics of a user during a swimming session, the system comprising:

one or more motion sensors configured to collect motion data; and

a processor circuit coupled to the one or more motion sensors and configured to execute instructions causing the processor to:

determine a first set of rotational data, wherein the first set of rotational data is expressed in a first frame of reference;

convert the first set of rotational data into a second set of rotational data, wherein the second set of rotational data is expressed in a second frame of reference;

determine one or more swimming metrics of the user based on the second set of rotational data, where determining the one or more swimming metrics includes:

detecting a number of turns and a number of strokes of the user during the swimming session based on the received motion data;

determine a number of strokes per lap based on the number of turns and the number of strokes;

determine a variance of the number of strokes per lap;

adjust the number of turns to reduce the variance of the number of strokes per lap;

determine a lap count of the user based on the adjusted number of turns; and

output the one or more swimming metrics of the user.

20. A system comprising:

one or more motion sensors configured to collect motion data, the one or more sensors included in or coupled to a wearable device worn on a wrist of a user during a swimming session;

a processor circuit coupled to the one or more motion sensors and configured to execute instructions causing the processor to:

receive motion data from one or more motion sensors of the wearable device;

determine, using the motion data, a first set of rotational data of the wearable device, wherein the first set of rotational data is expressed in a first frame of reference;

convert the first set of rotational data into a second set of rotational data, wherein the second set of rotational data is expressed in a second frame of reference, and wherein the second set of rotational data includes data indicative of the user's arm or wrist movements;

determine one or more swimming metrics of the user based on the second set of rotational data, where the instructed are further executed to:

detect a number of turns and a number of strokes of the user during the swimming session based on the received motion data;

determine a number of strokes per lap based on the number of turns and the number of strokes;

determine a variance of the number of strokes per lap;

adjust the number of turns to reduce the variance of the number of strokes per lap;

determine a lap count of the user based on the adjusted number of turns; and

output the one or more swimming metrics of the user.