Methods and systems for calibrating an inertial measurement unit of an electronic device

1. A method, comprising:

at a mobile electronic device inserted in a headset, wherein the mobile electronic device has a first inertial measurement unit (IMU):

when a controller having a second IMU is mounted to the headset:

performing a calibration procedure to generate first calibration data for the first IMU and second calibration data for the second IMU;

receiving the second calibration data from the controller;

determining a difference between the first calibration data and the second calibration data received from the controller; and

calibrating the first IMU in accordance with the difference between the first calibration data and the second calibration data;

when the controller has been removed from the headset after performing the calibrating:

executing a virtual-reality application, comprising generating images based in part on motion data generated by the calibrated first IMU, the motion data corresponding to motions of the mobile electronic device, and displaying the images.

2. The method of claim 1 , wherein performing the calibration procedure comprises displaying images that prompt movement of the headset.

3. The method of claim 1 , wherein:

the mobile electronic device comprises a connector; and

the calibration procedure is performed in response to electrically coupling the connector with a dock of the headset.

4. The method of claim 1 , wherein:

the first calibration data comprise one or more measurements taken by the first IMU;

the second calibration data comprise one or more measurements taken by the second IMU; and

determining the difference between the first calibration data and the second calibration data comprises determining respective differences between the one or more measurements taken by the first IMU and the one or more measurements taken by the second IMU.

5. The method of claim 4 , wherein:

the first IMU comprises a plurality of instruments; and

calibrating the first IMU comprises adjusting at least one instrument of the first IMU to account for the respective differences between the one or more measurements taken by the first IMU and the one or more measurements taken by the second IMU.

6. The method of claim 4 , wherein:

calibrating the first IMU comprises storing the respective differences between the one or more measurements taken by the first IMU and the one or more measurements taken by the second IMU; and

the method further comprises, while executing the virtual-reality application, adjusting measurements taken by the first IMU to account for the respective differences;

wherein generating the images is performed in accordance with adjusting the measurements.

7. The method of claim 4 , wherein:

the one or more measurements taken by the first IMU comprise measurements of yaw, pitch, and roll; and

the one or more measurements taken by the second IMU comprise measurements of yaw, pitch, and roll.

8. The method of claim 1 , wherein calibrating the first IMU is performed in response to determining that the difference between the first calibration data and the second calibration data satisfies one or more criteria.

9. The method of claim 1 , wherein the second calibration data is received using near-field communication.

10. The method of claim 1 , further comprising, at the mobile electronic device inserted in the headset, establishing a wireless communication channel with the controller, wherein the second calibration data is received via the wireless communication channel.

11. The method of claim 1 , wherein the first and second IMUs each comprise a respective accelerometer and a respective gyroscope for each dimension in three-dimensional space.

12. The method of claim 1 , wherein the mobile electronic device and the headset compose a head-mounted display.

13. The method of claim 1 , wherein, when the controller is mounted to the headset:

the controller has a predefined orientation with respect to the headset; and

the second IMU has a specified displacement and orientation with respect to the first IMU.

14. The method of claim 13 , wherein:

the method further comprises, at the mobile electronic device inserted in the headset, transforming the second calibration data to account for the specified displacement and orientation of the second IMU with respect to the first IMU; and

determining the difference between the first calibration data and the second calibration data is performed using the transformed second calibration data.

15. A mobile electronic device, comprising:

a first inertial measurement unit (IMU);

one or more processors; and

memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for:

when the mobile electronic device is inserted in a headset and a controller having a second IMU is mounted to the headset:

performing a calibration procedure to generate first calibration data for the first IMU and second calibration data for the second IMU;

receiving the second calibration data from the controller;

determining a difference between the first calibration data and the second calibration data received from the controller; and

calibrating the first IMU in accordance with the difference between the first calibration data and the second calibration data;

when the mobile electronic device is inserted in the headset and the controller has been removed from the headset after performing the calibrating:

executing a virtual-reality application, comprising generating images based in part on motion data generated by the calibrated first IMU, the motion data corresponding to motions of the mobile electronic device, and displaying the images.

16. A non-transitory computer-readable storage medium, storing one or more programs configured for execution by one or more processors of a mobile electronic device having a first inertial measurement unit (IMU), the one or more programs including instructions, which when executed by the one or more processors cause the mobile electronic device to:

when the mobile electronic device is inserted in a headset and a controller having a second IMU is mounted to the headset:

perform a calibration procedure to generate first calibration data for the first IMU and second calibration data for the second IMU;

receive the second calibration data from the controller;

determine a difference between the first calibration data and the second calibration data received from the controller; and

calibrate the first IMU in accordance with the difference between the first calibration data and the second calibration data;

when the mobile electronic device is inserted in the headset and the controller has been removed from the headset after performing the calibrating:

execute a virtual-reality application, comprising generating images based in part on motion data generated by the calibrated first IMU, the motion data corresponding to motions of the mobile electronic device, and displaying the images.