Power management for electromagnetic position tracking systems

• US 10,375,632 B1
• Filed: 02/06/2018
• Issued: 08/06/2019
• Est. Priority Date: 02/06/2018
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Stein, Murphy, Atkinson, Ian, Jain, Advait, Oganesian, Lucine, Chung, Sherk, Patkar, Saket
• Primary Examiner(s): Nguyen, Hai V
• Application Number:
  US15/889,861
• Publication Number:
  US 20190246350A1
• Time in Patent Office: 546 Days
• Field of Search: 455 411, 455 412
• CPC Class Codes: G01S 1/024 of beacon transmitters
• CPC Class Codes: G01S 5/0205 Details
• CPC Class Codes: G06F 1/163 Wearable computers, e.g. on a belt
• CPC Class Codes: G06F 1/325 Power saving in peripheral device
• CPC Class Codes: G06F 1/3259 Power saving in cursor control device, e.g. mouse, joystick, trackball
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/012 Head tracking input arrangements
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/73 for taking measurements, e.g. using sensing coils
• CPC Class Codes: H04W 52/0209 in terminal devices terminal devices per se H04W88/02
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An EM pose tracking system controls a power mode by adjusting a transmit power of the EM transmitter based on a metric correlated with jitter in the EM readings. Such a metric includes metrics such as estimated noise computed from received EM data, a computed distance between the transmitter and the receiver, a measured signal power between the transmitter and the receiver, and the like. By adjusting the transmit power based on the jitter metric, the EM tracking system can reduce overall power consumption at a device that employs the EM tracking system, thus allowing the system to be used in a wider variety of devices and improving the user experience with those devices.

Claims

1. A method comprising:

identifying, at an EM position tracking system, a first metric that is correlated to jitter in a relative pose between a transmitter and a receiver of the EM position tracking system;

setting a power mode of at least one of the transmitter and the receiver based on the first metric; and

in response to setting the power mode based on the first metric, discarding one or more samples generated from received EM data.

2. The method of claim 1, wherein the first metric is selected from the group consisting of:

estimated noise computed from received EM data, a computed distance between the transmitter and the receiver, and a measured signal power between the transmitter and the receiver.

3. The method of claim 1, wherein setting the power mode comprises setting the power mode to a first mode in response to the first metric exceeding a first threshold.

4. The method of claim 3, wherein setting the power mode comprises setting the power mode to a second mode in response to the first metric falling below a second threshold different from the first threshold.

5. The method of claim 3, wherein the first threshold corresponds to a threshold at which a user is expected to perceive the jitter in the relative pose.

6. The method of claim 3, further comprising:

calculating the first threshold based on, at least in part, data received from the receiver.

7. The method of claim 1, wherein discarding the one or more samples comprises:

discarding the one or more samples based on inspection of the received EM data.

8. The method of claim 1, wherein discarding the one or more samples comprises:

identifying a time window relative to a time when a request to change the power mode is received; and

discarding samples for a threshold amount of time during the time window.

9. A method, comprising:

sensing, by an electromagnetic (EM) receiver of an EM tracking system, data from an EM transmitter of the EM tracking system transmitting at a first power level; and

in response to detecting a sleep condition, placing the EM transmitter in a sleep mode by lowering a transmission power level of the EM transmitter, wherein in response to placing the EM transmitter in a sleep mode, discarding one or more samples of data from the EM transmitter.

10. The method of claim 9, wherein detecting the sleep condition comprises detecting the sleep condition for one of a threshold amount of time and a threshold number of samples.

11. The method of claim 9 wherein the sleep mode corresponds to an off mode of the EM transmitter.

12. The method of claim 9, wherein detecting the sleep condition comprises detecting that an application executing at a computer system associated with the EM tracking system is executing an application that does not use poses generated by the EM tracking system.

13. The method of claim 9, wherein detecting the sleep condition comprises detecting a distance between the EM transmitter and the EM receiver is greater than a threshold.

14. The method of claim 9 wherein detecting the sleep condition comprises detecting the computed motion of a device is below a threshold.

15. The method of claim 14, wherein detecting the computed motion of the device comprises detecting the computed motion of the device based on a secondary sensor.

16. The method of claim 14, wherein detecting the computed motion of the device comprises detecting the computed motion of the device based on the data sensed by the EM receiver.

17. The method of claim 9, wherein detecting the sleep condition comprises detecting at least one of:

receiving an indication that an associated device has entered a sleep mode, detecting a user selecting a mode that triggers the sleep mode, and detecting that a communications link between the EM transmitter and EM receiver has been interrupted.

18. A position tracking system comprising:

an electromagnetic (EM) receiver configured to generate a relative pose between an EM transmitter and the EM receiver; and

,

one or more processors configured to;

identify a first metric that is correlated to jitter in the relative pose; and

set a power mode of at least one of the EM transmitter and the EM receiver based on the first metric, wherein in response to setting the power mode based on the first metric, one or more samples are discarded that are generated from received EM data.

19. The position tracking system of claim 18, wherein the first metric is selected from the group consisting of:

estimated noise computed from received EM data, a measured distance between the transmitter and the receiver, and a measured signal power between the transmitter and the receiver.

20. The position tracking system of claim 18, wherein the one or more processors set the power mode comprises to a first mode in response to the first metric exceeding a first threshold.

21. The position tracking system of claim 20, wherein the one or more processors set the power mode to a second mode in response to the first metric exceeding a second threshold different from the first threshold.

22. The position tracking system of claim 20, wherein the first threshold corresponds to a threshold at which a user is expected to perceive the jitter in the relative pose.

23. The position tracking system of claim 20, wherein the one or more processors are configured to:

calculate the first threshold based on at least in part, data received from the EM receivers.

24. The position tracking system of claim 18, wherein the one or more processors are configured to:

in response to setting the power mode based on the first metric, discard one or more samples generated from received EM data.

25. The position tracking system of claim 18 wherein the one or more processors are configured to discard samples taken for a threshold amount of time after a request to change the power mode is received.

26. A position tracking system, comprising:

an electromagnetic (EM) receiver configured to generate a relative pose between an EM transmitter and the EM receiver; and

,

one or more processors configured to;

in response to detecting a sleep condition, placing the EM transmitter in a sleep mode by lowering a transmission power level of the EM transmitter, wherein in response to placing the EM transmitter in the sleep mode, discarding one or more samples of data from the EM transmitter.

27. The position tracking system of claim 26, wherein detecting the sleep condition comprises detecting the sleep condition for one of a threshold amount of time and a threshold number of samples.

28. The position tracking system of claim 26 wherein the sleep mode corresponds to an off mode of the EM transmitter.

29. The position tracking system of claim 26, wherein detecting the sleep condition comprises detecting that a computer system associated with the position tracking system is executing an application that does not use poses generated by the position tracking system.

30. The position tracking system of claim 26, wherein detecting the sleep condition comprises detecting a distance between the EM transmitter and the EM receiver has crossed a threshold.

31. The position tracking system of claim 26 wherein detecting the sleep condition comprises detecting the computed motion of a device is below a threshold.

32. The position tracking system of claim 31, wherein detecting the computed motion of the device comprises detecting the computed motion of the device based on a secondary sensor.

33. The position tracking system of claim 31, wherein detecting the computed motion of the device comprises detecting the computed motion of the device based on the data sensed by the EM receiver.

34. The position tracking system of claim 26, wherein detecting the sleep condition comprises detecting at least one of:

receiving an indication that an associated device has entered a sleep mode, detecting a user selecting a mode that triggers the sleep mode, and detecting that a communications link between the EM transmitter and EM receiver has been interrupted.