# US 10,375,632 B1 · Power management for electromagnetic position tracking systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,375,632 B1 - Document ID: US10375632B1 - Status: Granted - Kind: B1 - Application number: 15/889,861 - Filed: 2018-02-06 - Published: 2019-08-08 - Granted: 2019-08-06 - Earliest claimed: 2018-02-06 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Murphy Stein; Ian Atkinson; Advait Jain; Lucine Oganesian; Sherk Chung; Saket Patkar - Web page: https://patentgrep.com/patent/US10375632B1 ## CPC - H04W 52/0209: {in terminal devices} - G01S 1/024: {of beacon transmitters} - G01S 5/0205: {Details} - G06F 1/163: {Wearable computers, e.g. on a belt} - G06F 1/325: {Power saving in peripheral device} - G06F 1/3259: {Power saving in cursor control device, e.g. mouse, joystick, trackball} - G06F 3/011: {Arrangements for interaction with the human body, e.g. for user immersion in virtual reality (blind teaching G09B21/00)} - G06F 3/012: {Head tracking input arrangements} - G06F 3/0346: with detection of the device orientation or free movement in a three-dimensional [3D] space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors - H04B 5/266: {One coil at each side, e.g. with primary and secondary coils} - H04B 5/73: for taking measurements, e.g. using sensing coils - Y02D 10/00: Energy efficient computing, e.g. low power processors, power management or thermal management - Y02D 30/70: in wireless communication networks - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04B: TRANSMISSION - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## 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 ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) 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. ### Claim 4 (depends on 3) 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. ### Claim 5 (depends on 3) 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. ### Claim 6 (depends on 3) The method of claim 3, further comprising: calculating the first threshold based on, at least in part, data received from the receiver. ### Claim 7 (depends on 1) 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. ### Claim 8 (depends on 1) 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. ### Claim 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. ### Claim 10 (depends on 9) 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. ### Claim 11 (depends on 9) The method of claim 9 wherein the sleep mode corresponds to an off mode of the EM transmitter. ### Claim 12 (depends on 9) 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. ### Claim 13 (depends on 9) 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. ### Claim 14 (depends on 9) The method of claim 9 wherein detecting the sleep condition comprises detecting the computed motion of a device is below a threshold. ### Claim 15 (depends on 14) 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. ### Claim 16 (depends on 14) 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. ### Claim 17 (depends on 9) 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. ### Claim 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. ### Claim 19 (depends on 18) 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. ### Claim 20 (depends on 18) 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. ### Claim 21 (depends on 20) 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. ### Claim 22 (depends on 20) 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. ### Claim 23 (depends on 20) 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. ### Claim 24 (depends on 18) 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. ### Claim 25 (depends on 18) 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. ### Claim 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. ### Claim 27 (depends on 26) 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. ### Claim 28 (depends on 26) The position tracking system of claim 26 wherein the sleep mode corresponds to an off mode of the EM transmitter. ### Claim 29 (depends on 26) 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. ### Claim 30 (depends on 26) 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. ### Claim 31 (depends on 26) The position tracking system of claim 26 wherein detecting the sleep condition comprises detecting the computed motion of a device is below a threshold. ### Claim 32 (depends on 31) 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. ### Claim 33 (depends on 31) 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. ### Claim 34 (depends on 26) 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.