US20150308861A1 - Wireless position sensing using magnetic field of two transmitters - Google Patents
Wireless position sensing using magnetic field of two transmitters Download PDFInfo
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- US20150308861A1 US20150308861A1 US14/697,042 US201514697042A US2015308861A1 US 20150308861 A1 US20150308861 A1 US 20150308861A1 US 201514697042 A US201514697042 A US 201514697042A US 2015308861 A1 US2015308861 A1 US 2015308861A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/0206—Three-component magnetometers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/20—Instruments for performing navigational calculations
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/204—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils
- G01D5/2073—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils by movement of a single coil with respect to two or more coils
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/20—Instruments for performing navigational calculations
- G01C21/206—Instruments for performing navigational calculations specially adapted for indoor navigation
Definitions
- the present application relates to wirelessly detecting positions of devices, e.g., portable or mobile devices.
- FIG. 1 is a simplified block diagram of a positioning system according to one embodiment.
- FIG. 2 is a block diagram showing the system of FIG. 1 in a 3-dimensional environment.
- FIG. 3A is a simplified block diagram illustrating envelope detection using a computing unit according to one embodiment.
- FIG. 3B is a simplified block diagram illustrating envelope detection using an analog envelope detector according to one embodiment.
- FIG. 4 is a plot showing a predicted field model for a single coil according to one embodiment.
- FIG. 5 is a plot showing a predicted field model for two coils according to one embodiment.
- FIG. 6 is a simplified block diagram of a positioning process according to one embodiment.
- FIG. 7 is a diagram showing an example experimental setup of the system of FIG. 1 .
- FIG. 8 is a flowchart illustrating a positioning process according to one embodiment.
- Various aspects herein advantageously permit position to be determined rapidly using a low-power microcontroller. No large database of hotspots or antennas is required. Various aspects permit very high-speed tracking of motion.
- the term “coil” when used in reference to an antenna is not limiting, and other types of antennas capable of performing the listed functions can be used.
- Various aspects herein use low frequencies, e.g., ⁇ 1 MHz or ⁇ 500 kHz, ⁇ 70 kHz, or ⁇ 80 kHz or ⁇ 35kHz. Other frequencies can also be used, e.g., >1 MHz.
- Magnetic sensors described herein can include sensors including two or more substantially orthogonal coils for measuring components of a magnetic field.
- a triaxial or other magnetoresistive sensor can also or alternatively be used.
- references to the Earth's coordinate system include other reference coordinate systems common or substantially common to transmitter and receiver.
- an approximate location can be used as a starting point to locate the magnetic-field vector of interest. Initial estimates of the approximate location can be made in various ways. The approximate location is within an area determined using the determined signal strengths (magnetic field strengths) of the arriving signals and a corresponding estimate of distance to each transmitter (as in distance estimation using WiFi, Bluetooth, RFID signal strength).
- an exhaustive search is performed of coarsely-spaced sample points in the search area. More closely-spaced sample points are then tested around the coarsely-spaced point that gives the minimum error. This procedure is repeated with successively more closely-spaced sets of sample points (successively finer sampling grids) until the required spatial accuracy is satisfied.
- a position or orientation of the receiver can be transformed into other coordinate systems, e.g., Earth-relative systems such as WGS84 or local systems such as a coordinate frame of a room or building. Coordinate transforms can be done using rotations, skews, and other techniques well known in the computer-graphics and cartographic arts.
- a technical effect is to detect magnetic fields from the transmitter(s) and determine the location of the receiver using the detected fields. Further technical effects of various aspects include presenting an indication of the receiver's position on an electronic display and transmitting the determined position to the transmitter, a computer or computing unit, or another device.
- FIG. 1 illustrates a basic block diagram of a positioning system 100 according to one embodiment.
- the positioning system 100 includes two transmitters (shown as antenna coils 102 ) and at least one receiver 104 .
- the receiver 104 includes a tri-axis magnetic sensor 106 .
- the coils 102 are placed in different positions and can have any two-dimensional and three-dimensional shape: circular, elliptic, rectangle, square, diamond, triangle, etc.
- Signal generator 110 and drivers 112 may be included to generate waveforms and drive the coils 102 simultaneously to transmit periodic beacon signals which have a fixed frequency. Any periodic signal can be used, but a sinusoidal signal is preferred as it is most effective for simplifying the transmitter and receiver design.
- the frequencies f 1 and f 2 of the two periodic signals from the two transmitting coils are close to each other but different.
- the transmitting coils 102 will generate a spatial magnetic field where the field strength and direction depends on the position in the space. Because the two signals from the two transmitters have slightly different frequencies, the amplitude of the magnetic field signal at any given position (x, y, z) will be modulated where the modulation frequency is the difference between the two transmitting signal frequencies
- Amplifiers 112 , A/D converters 116 may be operatively connected as shown to amplify and convert the output of the magnetic sensor 106 to a digital form suitable for input by a computing unit 118 .
- FIG. 2 illustrates operation of the system 100 in a 3-dimensional environment.
- the tri-axis magnetic sensor 106 in the receiver 104 measures the signal transmitted by the two transmitting coils 102 .
- the sensor 106 may comprise three planar coils orthogonally placed relative to each other as a tri-axis magnetic sensor.
- a solid state tri-axis magnetic sensor such as three orthogonally placed magnetoresistive sensors may be used as sensor 106 .
- the computing unit 118 may be placed in the receiver 104 , in the transmitter, or remoted located somewhere else. When the computing unit 118 is not placed in the receiver 104 , the measured data may be sent to a remote computing unit placed outside of the receiver 104 through a wireless channel or wired channel.
- the envelope of the amplitude modulated signal 113 from the coils 102 may be detected using the computing unit 118 ( FIG. 3A ).
- the envelope detection may be performed by an analog envelope detector 115 connected to the sensor 106 ( FIG. 3B ).
- FIG. 4 shows an equi-magnetic field magnitude surface 400 when one transmitting coil 102 transmits.
- the equi-magnitude surface 400 has an ellipsoid shape.
- the crossing line between the two ellipsoids is an oval shaped closed line 503 on a curved 2-dimensional plane, and the receiver 104 is located on the crossing line of the two ellipsoids 501 and 502 .
- the crossing line 503 may be only using the magnitudes of the measured magnetic fields by the receiver 104 , no orientation information is required.
- the receiver position may be found by comparing the estimated angle ⁇ with the measured angle ⁇ M because the difference between the estimated angle and the measured angle
- the position of the receiver 104 above is found without its orientation information.
- the rotation matrix we can estimate the orientation of the receiver ( ⁇ , ⁇ , ⁇ ) with respect to the transmitter's coordinate frame (X, Y, Z).
- FIG. 6 shows a simplified block diagram of the positioning process 600 using two transmitting coils.
- the process starts at stage 602 where the magnetic sensor 106 senses the transmitter 102 magnetic field vector in the receiver 104 coordinate frame.
- the envelope detector 115 (or alternatively the computing unit 118 ) detects the envelope of the magnetic field signals.
- the computing unit 118 calculates the magnetic field signal vectors in the receiver 104 coordinate fram using the maxima and minima of the envelope.
- the magnitudes of the magnetic field vectors are evaluated.
- the position of the receiver 104 is determined using the magnitudes and angle of the expected (modeled) and measured values of the transmitting coil 102 field.
- coordinate correction is optionally applied to the position.
- the receiver 104 position is used to determine the magnetic field vectors at the receiver location in the transmitter coil's (X, Y, Z) coordinate frame.
- the rotation matrix is determined to find the orientation of the receiver 104 .
- FIG. 7 shows an example implementation of the system 100 for determining the location and orientation of the receiver relative to the transmitters 102 using a distributed magnetic field model from the two transmitters 102 .
- Use of the distributed model improves location accuracy significantly.
- FIG. 8 shows a process 800 for implementing the disclosed method. The process starts at stage 802 where the amplitudes from the three orthogonal coils in the magnetic sensor 106 are read. At stage 804 , the envelope of the received signals is detected and the magnetic field vectors in the receiver coordinate system (u, v, w) are computed. At stage 808 , the absolute magnetic field vectors from the two transmitter coils 102 , along with the angle between the two vectors, is calculated using the dot product formula.
- the computing unit 118 checks the error between the magnetic model of the transmitter coils 102 .
- the model is constructed by breaking the transmitter loop into smaller sections and applying Biot-Savart law to calculate the magnetic-filed vector at any given location (x,y,z) using it. To reduce the compute time, this calculation is done for just one loop of the coil 102 and the resultant field is multiplied be the total number of turns. If the error between the measured field values and the modeled values is not less than a predetermined minimum error, the process moves to stage 812 . At stage 812 , the expected magnetic field values for a plurality of positions around the estimated position are calculated.
- 27 corners are evaluated (x ⁇ x: ⁇ x:x+ ⁇ x, y ⁇ y: ⁇ y:y+ ⁇ y, z ⁇ z: ⁇ z:z+ ⁇ z), where ⁇ is the step size.
- the Euclidean distance is then found between the expected magnetic-field value and the one calculated for the 27 corners.
- the corner with the least distance (out of 27) is selected as the new starting position (stage 814 ) and the process is repeated (returns to step 810 ) until the solution converges and the error is within the predetermined limit.
- step 810 If the error from step 810 is within the predetermined limit, the process moves to stage 816 , where the x/y/z step size is compared to a predetermined minimum. If the step size is at the minimum, the computing unit 118 outputs the estimated x,y,z position of the receiver 104 (stage 820 ). If not, the step size is reduced (stage 818 ) and the error is again evaluated (step 810 ).
- the magnetic-field vector at the receiver 104 position (x, y, z) in the transmitter coil 102 co-ordinate system is determined. From the magnetic field vectors ( ⁇ right arrow over (E) ⁇ 1 and ⁇ right arrow over (E) ⁇ z ) in the transmitter coil 102 co-ordinate system (which uses (X, Y, Z)) and its projection in the receiver 104 co-ordinate system (which uses (U, V, W)), the rotation or orientation angles are determined and output (stage 824 ).
- the receiver 104 can possibly be located in one of the four quadrants relative to the transmitter coils 102 : (+X, +Y), (+X, ⁇ Y), ( ⁇ X, +Y), (+X, +Y).
- the signals directly from the tri-axial magnetic sensor 106 are processed to determine the polarity.
- angle correction needs to be applied based on the magnetic field vectors at estimated (x, y, z) location and then the above algorithm is reapplied.
- a 3-Dimensional sensor e.g., a compass+accelerometer
- a 3-Dimensional sensor can be used to find out the rotation angle direction with respect to the transmitter 102 which can be used to detect the quadrant of the receiver 104 .
- the sign of rotation is to be determined here with some computation, one of the sensors can be removed.
- the transmitter coils 102 are laid flat on a table and the receiver 104 hovers above it, only pitch and roll angles are required to detect the correct quadrant of the receiver and hence the quadrant detection will be achieved only with an accelerometer.
- Indoor RF transmission modalities can be heavily affected by channel characteristics, e.g., the structure of buildings.
- frequencies ⁇ 1 MHz are used for effective propagation through, e.g., walls, human bodies, and other features of indoor environments. Such frequencies have wavelengths in the tens of meters, so the receivers can operate in the near field of the transmitting antenna, and not in the far field. Therefore radiative effects do not need to be considered or compensated for, in various examples.
- Lower frequencies increase the antenna size and provide improved penetration of objects.
- position accuracy can be more affected by walls than at lower frequencies.
- frequencies of 12 MHz and above can be used, and advantageously still pass through human bodies.
- various low frequencies can be used since the electromagnetic spectrum is not heavily used at LF.
- Other users include ham radio operators.
- Multiple frequencies can be used for different transmitters, and receivers can include notch filters corresponding to specific transmitter frequencies to avoid interference.
- any of the computing units 118 , the receiver 104 , the magnetic sensor 106 , the signal generator 110 , the driver 112 may include one or more computer processors, memory, and data storage units for analyzing data and performing other analyses described herein, and related components.
- the processors can each include one or more microprocessors, microcontrollers, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), programmable logic devices (PLDs), programmable logic arrays (PLAs), programmable array logic devices (PALs), or digital signal processors (DSPs).
- the data storage unit can include or be communicatively connected with one or more processor-accessible memories configured to store information.
- the memories can be, e.g., within a chassis or as parts of a distributed system.
- processor-accessible memory is intended to include any data storage device to or from which processor 186 can transfer data, whether volatile or nonvolatile; removable or fixed; electronic, magnetic, optical, chemical, mechanical, or otherwise.
- Exemplary processor-accessible memories include but are not limited to: registers, floppy disks, hard disks, tapes, bar codes, Compact Discs, DVDs, read-only memories (ROM), erasable programmable read-only memories (EPROM, EEPROM, or Flash), and random-access memories (RAMs).
- One of the processor-accessible memories in the data storage system 140 can be a tangible non-transitory computer-readable storage medium, i.e., a non-transitory device or article of manufacture that participates in storing instructions that can be provided to processor for execution.
- aspects described herein may be embodied as systems or methods. Accordingly, various aspects herein may take the form of an entirely hardware aspect, an entirely software aspect (including firmware, resident software, micro-code, etc.), or an aspect combining software and hardware aspects. These aspects can all generally be referred to herein as a “service,” “circuit,” “circuitry,” “module,” or “system.”
- various aspects herein may be embodied as computer program products including computer readable program code stored on a tangible non-transitory computer readable medium. Such a medium can be manufactured as is conventional for such articles, e.g., by pressing a CD-ROM.
- the program code includes computer program instructions that can be loaded into the processor (and possibly also other processors), to cause functions, acts, or operational steps of various aspects herein to be performed by the processor.
- Computer program code for carrying out operations for various aspects described herein may be written in any combination of one or more programming language(s).
Abstract
A positioning system for determining the location of a receiver relative to a transmitter. The system includes two transmitting coils configured to transmit a periodic signal with a respective selected frequency during a positioning event, wherein the frequencies of the two signals transmitted by the two transmitting coils during the positioning event are different. A receiver includes a sensing unit for measuring the magnetic field vectors produced by the two simultaneously transmitting coils. A computing unit is configured to use the measured magnetic field vectors to calculate the position and orientation of the receiver with respect to the transmitter's coordinate frame.
Description
- The present application claims the benefit of U.S. provisional application Ser. No. 61/984,242, filed Apr. 25, 2014, the contents of which are hereby incorporated by reference in its entirety.
- The present application relates to wirelessly detecting positions of devices, e.g., portable or mobile devices.
- There is an increasing need for ways of determining the location of mobile or portable objects or devices, e.g., cellular telephones or blood-borne sensors. GPS, LORAN, and similar systems can provide location information, but often only with resolution on the order of 15 m. Moreover, such systems can be more difficult to use indoors due to changes in signal propagation through walls and other features of buildings. WIFI or BLUETOOTH triangulation has been proposed and may have an accuracy as low as 1-2 m indoors. However, these schemes often require large databases of known transmitters (TX). There is, therefore, a need of positioning systems that provide high accuracy and do not require large databases.
- Reference is made to US 2013/0166002 by Jung et al., published Jun. 27, 2013, the disclosure of which is incorporated herein by reference.
- The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein:
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FIG. 1 is a simplified block diagram of a positioning system according to one embodiment. -
FIG. 2 is a block diagram showing the system ofFIG. 1 in a 3-dimensional environment. -
FIG. 3A is a simplified block diagram illustrating envelope detection using a computing unit according to one embodiment. -
FIG. 3B is a simplified block diagram illustrating envelope detection using an analog envelope detector according to one embodiment. -
FIG. 4 is a plot showing a predicted field model for a single coil according to one embodiment. -
FIG. 5 is a plot showing a predicted field model for two coils according to one embodiment. -
FIG. 6 is a simplified block diagram of a positioning process according to one embodiment. -
FIG. 7 is a diagram showing an example experimental setup of the system ofFIG. 1 . -
FIG. 8 is a flowchart illustrating a positioning process according to one embodiment. - The attached drawings are for purposes of illustration and are not necessarily to scale.
- In the following description, some aspects will be described in terms that would ordinarily be implemented as software programs. Those skilled in the art will readily recognize that the equivalent of such software can also be constructed in hardware, firmware, or micro-code. Because data-manipulation algorithms and systems are well known, the present description will be directed in particular to algorithms and systems forming part of, or cooperating more directly with, systems and methods described herein. Other aspects of such algorithms and systems, and hardware or software for producing and otherwise processing the signals involved therewith, not specifically shown or described herein, are selected from such systems, algorithms, components, and elements known in the art. Given the systems and methods as described herein, software not specifically shown, suggested, or described herein that is useful for implementation of any aspect is conventional and within the ordinary skill in such arts.
- Various aspects herein advantageously permit position to be determined rapidly using a low-power microcontroller. No large database of hotspots or antennas is required. Various aspects permit very high-speed tracking of motion.
- Throughout this disclosure, the term “coil” when used in reference to an antenna is not limiting, and other types of antennas capable of performing the listed functions can be used. Various aspects herein use low frequencies, e.g., <1 MHz or <500 kHz, ˜70 kHz, or ˜80 kHz or ˜35kHz. Other frequencies can also be used, e.g., >1 MHz. Magnetic sensors described herein can include sensors including two or more substantially orthogonal coils for measuring components of a magnetic field. A triaxial or other magnetoresistive sensor can also or alternatively be used.
- Throughout this disclosure, references to the Earth's coordinate system include other reference coordinate systems common or substantially common to transmitter and receiver.
- In one embodiment, an approximate location can be used as a starting point to locate the magnetic-field vector of interest. Initial estimates of the approximate location can be made in various ways. The approximate location is within an area determined using the determined signal strengths (magnetic field strengths) of the arriving signals and a corresponding estimate of distance to each transmitter (as in distance estimation using WiFi, Bluetooth, RFID signal strength).
- In one example, an exhaustive search is performed of coarsely-spaced sample points in the search area. More closely-spaced sample points are then tested around the coarsely-spaced point that gives the minimum error. This procedure is repeated with successively more closely-spaced sets of sample points (successively finer sampling grids) until the required spatial accuracy is satisfied.
- Throughout this disclosure, once a position or orientation of the receiver is determined with respect to the transmitter, that position or orientation can be transformed into other coordinate systems, e.g., Earth-relative systems such as WGS84 or local systems such as a coordinate frame of a room or building. Coordinate transforms can be done using rotations, skews, and other techniques well known in the computer-graphics and cartographic arts.
- In view of the foregoing, various aspects providing determination of the location of a receiver in proximity to a wireless transmitter are disclosed. A technical effect is to detect magnetic fields from the transmitter(s) and determine the location of the receiver using the detected fields. Further technical effects of various aspects include presenting an indication of the receiver's position on an electronic display and transmitting the determined position to the transmitter, a computer or computing unit, or another device.
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FIG. 1 illustrates a basic block diagram of apositioning system 100 according to one embodiment. As shown, thepositioning system 100 includes two transmitters (shown as antenna coils 102) and at least onereceiver 104. Thereceiver 104 includes a tri-axismagnetic sensor 106. Thecoils 102 are placed in different positions and can have any two-dimensional and three-dimensional shape: circular, elliptic, rectangle, square, diamond, triangle, etc.Signal generator 110 anddrivers 112 may be included to generate waveforms and drive thecoils 102 simultaneously to transmit periodic beacon signals which have a fixed frequency. Any periodic signal can be used, but a sinusoidal signal is preferred as it is most effective for simplifying the transmitter and receiver design. The frequencies f1 and f2 of the two periodic signals from the two transmitting coils are close to each other but different. Preferably, f1≠f2, |f1−f2|<f1/10, and |f1−f2|<f2/10. - The transmitting
coils 102 will generate a spatial magnetic field where the field strength and direction depends on the position in the space. Because the two signals from the two transmitters have slightly different frequencies, the amplitude of the magnetic field signal at any given position (x, y, z) will be modulated where the modulation frequency is the difference between the two transmitting signal frequencies |f1−f2|. -
Amplifiers 112, A/D converters 116 may be operatively connected as shown to amplify and convert the output of themagnetic sensor 106 to a digital form suitable for input by acomputing unit 118. -
FIG. 2 illustrates operation of thesystem 100 in a 3-dimensional environment. The tri-axismagnetic sensor 106 in thereceiver 104 measures the signal transmitted by the two transmittingcoils 102. In the illustrated embodiment, thesensor 106 may comprise three planar coils orthogonally placed relative to each other as a tri-axis magnetic sensor. In other embodiments, a solid state tri-axis magnetic sensor such as three orthogonally placed magnetoresistive sensors may be used assensor 106. Thecomputing unit 118 may be placed in thereceiver 104, in the transmitter, or remoted located somewhere else. When thecomputing unit 118 is not placed in thereceiver 104, the measured data may be sent to a remote computing unit placed outside of thereceiver 104 through a wireless channel or wired channel. - As shown in
FIG. 3 , the envelope of the amplitude modulated signal 113 from thecoils 102 may be detected using the computing unit 118 (FIG. 3A ). Alternatively, the envelope detection may be performed by ananalog envelope detector 115 connected to the sensor 106 (FIG. 3B ). - By measuring the maximum and minimum values of the modulated signal,) we can estimate the magnetic field signal vectors (Eu1, Ev1, Ew1) and (Eu2, Ev2, Ew2) in the
receiver 104 coordinate frame (U, V, W). The magnitudes of the two measured magnetic field signal vectors and the angle between the two vectors may be estimated using the following equations: -
- The magnetic field vectors in the transmitter coils 102 coordinate frame (X, Y, Z) is still unknown. However, because the magnitude of a magnetic field vector measured by the
receiver 104 at a given position must be the same regardless of the coordinate frame, we can show that: -
|E1|=√{square root over (Eu1 2 E+ v1 2 +E w1 2)}=√{square root over (E x1 2 + E y1 2 +E z1 2)} -
|E2|=√{square root over (Eu2 2 +E v2 2 +E w2 2)}=√{square root over (E x2 2 +E y2 2 +E z2 2)} (2) - where
(Ex1, Ey1, Ez1) and (Ex2, Ey2, Ez2) are the expected magnetic field vectors in the transmitter's coordinate frame (X, Y, Z), and
(Eu1, Ev1, Ew1) and (Eu2, Ev2, Ew2) are the measured magnetic field vectors in the receiver's coordinate frame (U, V, W). - The following is a graphical explanation of the above method.
FIG. 4 shows an equi-magneticfield magnitude surface 400 when one transmittingcoil 102 transmits. When the transmittingcoil 102 has a circular shape, the equi-magnitude surface 400 has an ellipsoid shape. We used a circular shaped transmittingcoil 102 in this example for mathematical simplicity, but the transmitting coil can have any shape. Because we measure two magnetic field magnitudes from the two transmittingcoils 102, we can draw twoellipsoids FIG. 5 . The crossing line between the two ellipsoids is an oval shapedclosed line 503 on a curved 2-dimensional plane, and thereceiver 104 is located on the crossing line of the twoellipsoids crossing line 503 may be only using the magnitudes of the measured magnetic fields by thereceiver 104, no orientation information is required. At each point on the crossing line, we can estimate the expected magnetic field vectors in the transmitter's coordinate frame (X, Y, Z), (Ex1, Ey1, Ez1) and (Ex2, Ey2, Ez2), using a physical model. We can also estimate the angle between the two estimated vectors, (Ex1, Ey1, Ez1) and (Ex2, Ey2, Ez2), at each point on the crossing line as follows: -
- The receiver position may be found by comparing the estimated angle θ with the measured angle θM because the difference between the estimated angle and the measured angle |θ−θM| will be the minimum, ideally zero, at the
receiver 104 position. This works because the angle between any two vectors remains the same when the coordinate frame rotates, and hence the calculated angle between the two estimated vectors in the transmitter's 104 coordinate frame (X, Y, Z) and the angle between the two measured vectors in the receiver's own coordinate frame (U, V, W) must be the same ideally at the position of thereceiver 104. - Note that the position of the
receiver 104 above is found without its orientation information. To find the orientation of the receiver 104 (α, β, γ) with respect to thetransmitter 102 coordinate frame (X, Y, Z), we can use the estimated magnetic field vectors (Ex1, Ey1, Ez1) and (Ex2, Ey2, Ez2) at the found position and the measured magnetic field vectors (Eu1, Ev1, Ew1) and (Eu2, Ev2, Ew2). For example, we can estimate the rotation matrix for the rotation from (Ex1, Ey1, Ez1) to (Eu1, Ev1, Ew1), and/or from (Ex2, Ey2, Ez2) to (Eu2, Ev2, Ew2). Using the rotation matrix, we can estimate the orientation of the receiver (α, β, γ) with respect to the transmitter's coordinate frame (X, Y, Z). -
FIG. 6 shows a simplified block diagram of thepositioning process 600 using two transmitting coils. The process starts atstage 602 where themagnetic sensor 106 senses thetransmitter 102 magnetic field vector in thereceiver 104 coordinate frame. Atstage 604 the envelope detector 115 (or alternatively the computing unit 118) detects the envelope of the magnetic field signals. Atstage 606, thecomputing unit 118 calculates the magnetic field signal vectors in thereceiver 104 coordinate fram using the maxima and minima of the envelope. Atstage 608, the magnitudes of the magnetic field vectors are evaluated. Atstep 610, the position of thereceiver 104 is determined using the magnitudes and angle of the expected (modeled) and measured values of the transmittingcoil 102 field. Atstage 612, coordinate correction is optionally applied to the position. Atstage 614, thereceiver 104 position is used to determine the magnetic field vectors at the receiver location in the transmitter coil's (X, Y, Z) coordinate frame. Atstep 616, the rotation matrix is determined to find the orientation of thereceiver 104. -
FIG. 7 shows an example implementation of thesystem 100 for determining the location and orientation of the receiver relative to thetransmitters 102 using a distributed magnetic field model from the twotransmitters 102. Use of the distributed model improves location accuracy significantly.FIG. 8 shows aprocess 800 for implementing the disclosed method. The process starts atstage 802 where the amplitudes from the three orthogonal coils in themagnetic sensor 106 are read. Atstage 804, the envelope of the received signals is detected and the magnetic field vectors in the receiver coordinate system (u, v, w) are computed. Atstage 808, the absolute magnetic field vectors from the twotransmitter coils 102, along with the angle between the two vectors, is calculated using the dot product formula. Atstage 810, thecomputing unit 118 checks the error between the magnetic model of the transmitter coils 102. The model is constructed by breaking the transmitter loop into smaller sections and applying Biot-Savart law to calculate the magnetic-filed vector at any given location (x,y,z) using it. To reduce the compute time, this calculation is done for just one loop of thecoil 102 and the resultant field is multiplied be the total number of turns. If the error between the measured field values and the modeled values is not less than a predetermined minimum error, the process moves to stage 812. Atstage 812, the expected magnetic field values for a plurality of positions around the estimated position are calculated. In one example, 27 corners are evaluated (x−Δx:Δx:x+Δx, y−Δy:Δy:y+Δy, z−Δz:Δz:z+Δz), where Δ is the step size. The Euclidean distance is then found between the expected magnetic-field value and the one calculated for the 27 corners. The corner with the least distance (out of 27) is selected as the new starting position (stage 814) and the process is repeated (returns to step 810) until the solution converges and the error is within the predetermined limit. - If the error from
step 810 is within the predetermined limit, the process moves to stage 816, where the x/y/z step size is compared to a predetermined minimum. If the step size is at the minimum, thecomputing unit 118 outputs the estimated x,y,z position of the receiver 104 (stage 820). If not, the step size is reduced (stage 818) and the error is again evaluated (step 810). - At
stage 822, The magnetic-field vector at thereceiver 104 position (x, y, z) in thetransmitter coil 102 co-ordinate system is determined. From the magnetic field vectors ({right arrow over (E)}1 and {right arrow over (E)}z) in thetransmitter coil 102 co-ordinate system (which uses (X, Y, Z)) and its projection in thereceiver 104 co-ordinate system (which uses (U, V, W)), the rotation or orientation angles are determined and output (stage 824). - In order to resolve potential problems with polarity ambiguity, the following method may be used in one embodiment. The
receiver 104 can possibly be located in one of the four quadrants relative to the transmitter coils 102: (+X, +Y), (+X, −Y), (−X, +Y), (+X, +Y). The signals directly from the tri-axial magnetic sensor 106 (before low-pass filtering) are processed to determine the polarity. The following algorithm is used to find polarity (No rotation is assumed here: α=β=γ0, and w,coil >(u,coil+w,coil)): - 1. If max(u,coil+w,coil)>max(w,coil), then X is positive, else X is negative
- 2. If max(v,coil+w,coil)>max(w,coil), then Y is positive, else Y is negative
- 3. If α≠0 or β≠0 or γ≠0, then angle correction needs to be applied based on the magnetic field vectors at estimated (x, y, z) location and then the above algorithm is reapplied.
- This method works because, assuming α=β=γ=0, when the receiver position is shifted from one quadrant to another, the direction of flux lines entering the u, v coil (among the three tri-axial coils) changes, changing the amplitude sign. The w coil at the same time, always remains in one side of the coil and is hence used as a reference.
- In another embodiment, a 3-Dimensional sensor (e.g., a compass+accelerometer) can be used to find out the rotation angle direction with respect to the
transmitter 102 which can be used to detect the quadrant of thereceiver 104. As only the sign of rotation is to be determined here with some computation, one of the sensors can be removed. E.g. if the transmitter coils 102 are laid flat on a table and thereceiver 104 hovers above it, only pitch and roll angles are required to detect the correct quadrant of the receiver and hence the quadrant detection will be achieved only with an accelerometer. - Indoor RF transmission modalities can be heavily affected by channel characteristics, e.g., the structure of buildings. In various embodiments, frequencies <1 MHz are used for effective propagation through, e.g., walls, human bodies, and other features of indoor environments. Such frequencies have wavelengths in the tens of meters, so the receivers can operate in the near field of the transmitting antenna, and not in the far field. Therefore radiative effects do not need to be considered or compensated for, in various examples. Lower frequencies increase the antenna size and provide improved penetration of objects. In various embodiments using frequencies of 12 MHz or higher, position accuracy can be more affected by walls than at lower frequencies. However, frequencies of 12 MHz and above can be used, and advantageously still pass through human bodies.
- In the disclosed embodiments, various low frequencies can be used since the electromagnetic spectrum is not heavily used at LF. Other users include ham radio operators. Multiple frequencies can be used for different transmitters, and receivers can include notch filters corresponding to specific transmitter frequencies to avoid interference.
- Any of the
computing units 118, thereceiver 104, themagnetic sensor 106, thesignal generator 110, thedriver 112 may include one or more computer processors, memory, and data storage units for analyzing data and performing other analyses described herein, and related components. The processors can each include one or more microprocessors, microcontrollers, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), programmable logic devices (PLDs), programmable logic arrays (PLAs), programmable array logic devices (PALs), or digital signal processors (DSPs). The data storage unit can include or be communicatively connected with one or more processor-accessible memories configured to store information. The memories can be, e.g., within a chassis or as parts of a distributed system. The phrase “processor-accessible memory” is intended to include any data storage device to or from which processor 186 can transfer data, whether volatile or nonvolatile; removable or fixed; electronic, magnetic, optical, chemical, mechanical, or otherwise. Exemplary processor-accessible memories include but are not limited to: registers, floppy disks, hard disks, tapes, bar codes, Compact Discs, DVDs, read-only memories (ROM), erasable programmable read-only memories (EPROM, EEPROM, or Flash), and random-access memories (RAMs). One of the processor-accessible memories in the data storage system 140 can be a tangible non-transitory computer-readable storage medium, i.e., a non-transitory device or article of manufacture that participates in storing instructions that can be provided to processor for execution. - Various aspects described herein may be embodied as systems or methods. Accordingly, various aspects herein may take the form of an entirely hardware aspect, an entirely software aspect (including firmware, resident software, micro-code, etc.), or an aspect combining software and hardware aspects. These aspects can all generally be referred to herein as a “service,” “circuit,” “circuitry,” “module,” or “system.”
- Furthermore, various aspects herein may be embodied as computer program products including computer readable program code stored on a tangible non-transitory computer readable medium. Such a medium can be manufactured as is conventional for such articles, e.g., by pressing a CD-ROM. The program code includes computer program instructions that can be loaded into the processor (and possibly also other processors), to cause functions, acts, or operational steps of various aspects herein to be performed by the processor. Computer program code for carrying out operations for various aspects described herein may be written in any combination of one or more programming language(s).
- The invention is inclusive of combinations of the aspects described herein. References to “a particular aspect” or “embodiment” and the like refer to features that are present in at least one aspect of the invention. Separate references to “an aspect” (or “embodiment”) or “particular aspects” or the like do not necessarily refer to the same aspect or aspects; however, such aspects are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to “method” or “methods” and the like is not limiting. The word “or” is used in this disclosure in a non-exclusive sense, unless otherwise explicitly noted.
- The invention has been described in detail with particular reference to certain preferred aspects thereof, but it will be understood that variations, combinations, and modifications can be effected by a person of ordinary skill in the art within the spirit and scope of the invention.
Claims (20)
1. A positioning system, comprising:
a) two transmitting coils, each coil configured to transmit a periodic signal with a respective selected frequency during a positioning event, wherein the frequencies of the two signals transmitted by the two transmitting coils during the positioning event are different;
b) a receiver including a sensing unit for measuring the magnetic field vectors produced by the two simultaneously transmitting coils; and
c) a computing unit configured to use the measured magnetic field vectors to calculate the position and orientation of the receiver with respect to the transmitter's coordinate frame.
2. The system according to claim 1 , wherein the sensing unit includes a tri-axis magnetic sensor.
3. The system according to claim 1 , in which one or both of the transmitting coils are integrated into a mobile electronic device, and both the transmitting coils and sensing unit move simultaneously, and wherein the orientation of the transmitting coil(s) in the earth's coordinate system is provided to the computing unit in the receiver at real time.
4. The system of claim 1 , comprising a plurality of receivers which operate simultaneously and independently.
5. The system according to claim 1 , wherein the computing unit is integrated in the receiver.
6. The system according to claim 1 , wherein the computing unit is located remotely from the receiver, the receiver transmits the measured magnetic field vector in the receiver's own coordinate system to the computing unit through a wired or wireless channel.
7. The system according to claim 1 , wherein the magnetic sensor includes three planar coils oriented orthogonally to each other.
8. The system according to claim 1 , wherein the receiver comprises a plurality of tri-axis magnetic sensors for measuring the magnetic field of the transmitting coil.
9. The system according to claim 1 , wherein the receiver comprises a a solid-state compass to measure the receiver orientation in the earth's coordinate system, the receiver orientation is transmitted to the computing unit.
10. The system according to claim 1 , wherein the transmitting coils are integrated into a computing unit, the position data of the receiver is transmitted to the computing unit.
11. The system according to claim 10 , wherein the computing unit comprises at least one of a television, mobile phone, tablet computer, notebook computer, desktop computer, wearable device and a video gaming device.
12. The system according to claim 1 , wherein the receiver is integrated into the computing unit, allowing the position of the computing unit with respect to the transmitting coils to be determined.
13. The system according to claim 1 , wherein the receiver is configured as a stand-alone unit, the receiver sends the position and orientation data to the computing unit through a wired or wireless channel.
14. The system according to claim 1 , wherein the transmitting coils are configured to transmit a beacon signal, the beacon signal including a periodic signal portion for determining the receiver position and an auxiliary signal portion.
15. The system according to claim 14 , wherein the auxiliary signal portion includes at least one of coil identification information, coil orientation, transmitting signal frequency, transmitting coil size, and transmitting coil shape.
16. The system according to claim 1 , further comprising:
a plurality of pairs of transmitting coils, each pair configured to transmit at a different set of frequencies than the other pairs; and
a plurality of receivers, each of said receivers configured to receive signals from one of said pairs.
17. The system according to claim 1 , wherein the computing unit is configured to perform an initial estimate of the receiver position and orientation of the receiver, and then evaluate a plurality of positions around the initial estimated position.
18. The system according to claim 17 , wherein the computing unit is further configured to evaluate errors between measured field values for the plurality of positions and predicted field values.
19. The system according to claim 18 , the computing unit further configured to select a second estimated position from the plurality of positions, the second estimated position having the smallest field error compared to the remaining plurality of positions.
20. A method of determining a position of a receiver in relation to a pair of transmitting coils, comprising:
simultaneously transmitting a pair of periodic signals during a positioning event using the pair of transmitting coils, the periodic signals having different frequencies;
using a receiver, sensing a magnetic field vector produced by the transmitting coils;
using a computing device, estimating a position and orientation of the receiver with respect to the transmitter coils' coordinate system using the measured magnetic field vector from the two transmitter coils.
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170017787A1 (en) * | 2015-07-16 | 2017-01-19 | Linkedin Corporation | Automatically securing an electronic device |
US20180338297A1 (en) * | 2017-05-19 | 2018-11-22 | Microsoft Technology Licensing, Llc | Magnetic tracker with dual-transmit frequency |
CN110133582A (en) * | 2018-02-08 | 2019-08-16 | 阿森松技术公司 | Distortion in compensation electromagnetic tracking system |
US10830572B2 (en) | 2017-10-12 | 2020-11-10 | Google Llc | Hemisphere ambiguity correction in electromagnetic position tracking systems |
US20220082722A1 (en) * | 2016-11-08 | 2022-03-17 | Frederick Energy Products, Llc | Managing vehicle movement in aisles by use of magnetic vectors |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10101408B2 (en) * | 2014-04-25 | 2018-10-16 | Purdue Research Foundation | Wireless position sensing using magnetic field of single transmitter |
KR102348926B1 (en) * | 2015-08-25 | 2022-01-11 | 삼성전자주식회사 | Method and apparatus for estimating location in communication system |
US10199881B2 (en) * | 2015-10-23 | 2019-02-05 | Mediatek Inc. | Robust foreign objects detection |
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CN110945745B (en) | 2018-07-19 | 2023-09-01 | 联发科技(新加坡)私人有限公司 | Foreign object detection in a wireless power transfer system |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20030184285A1 (en) * | 2002-03-27 | 2003-10-02 | Visualization Technology | Magnetic tracking system |
US20090115406A1 (en) * | 2007-11-01 | 2009-05-07 | General Electric Company | System and method for minimizing mutual inductance coupling between coils in an electromagnetic tracking system |
US20100141261A1 (en) * | 2008-12-05 | 2010-06-10 | Johan Overby | Precise location and orientation of a concealed dipole transmitter |
US20120080957A1 (en) * | 2008-08-20 | 2012-04-05 | Cooper Emily B | Wireless power transfer apparatus and method thereof |
US20120242160A1 (en) * | 2011-02-17 | 2012-09-27 | Qualcomm Incorporated | Systems and methods for controlling output power of a wireless power transmitter |
US20120248891A1 (en) * | 2011-03-31 | 2012-10-04 | Qualcomm Incorporated | Systems and methods for detecting and protecting a wireless power communication device in a wireless power system |
US20150137746A1 (en) * | 2012-05-14 | 2015-05-21 | Lg Electronics Inc. | Wireless power transfer device and wireless charging system having same |
US20150285612A1 (en) * | 2014-04-07 | 2015-10-08 | Cgg Services Sa | Electromagnetic receiver tracking and real-time calibration system and method |
US20150309126A1 (en) * | 2014-04-25 | 2015-10-29 | Purdue Research Foundation | Wireless position sensing using magnetic field of single transmitter |
US20160356601A1 (en) * | 2013-11-06 | 2016-12-08 | Tdm | Hybrid inertial/magnetic system for determining the position and orientation of a mobile body |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2161808A3 (en) * | 2007-03-22 | 2012-05-30 | Powermat Technologies Ltd. | Inductive power outlet locator |
EP2504723A4 (en) * | 2009-11-27 | 2016-10-05 | Geotech Airborne Ltd | Receiver coil assembly for airborne geophysical surveying with noise mitigation |
AU2011220469A1 (en) * | 2010-02-25 | 2012-08-30 | Mcw Research Foundation, Inc. | Method for simultaneous multi-slice magnetic resonance imaging using single and multiple channel receiver coils |
US9115569B2 (en) * | 2010-06-22 | 2015-08-25 | Halliburton Energy Services, Inc. | Real-time casing detection using tilted and crossed antenna measurement |
US9474909B2 (en) | 2011-12-12 | 2016-10-25 | Purdue Research Foundation | Wireless magnetic tracking |
US9836028B2 (en) * | 2013-02-08 | 2017-12-05 | Chuck Fung | Method, system and processor for instantly recognizing and positioning an object |
US9367061B2 (en) * | 2014-02-07 | 2016-06-14 | Enovate Medical, Llc | Medical cart for dispensing medication |
-
2015
- 2015-04-27 US US14/697,008 patent/US10101408B2/en active Active
- 2015-04-27 US US14/697,042 patent/US20150308861A1/en not_active Abandoned
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20030184285A1 (en) * | 2002-03-27 | 2003-10-02 | Visualization Technology | Magnetic tracking system |
US20090115406A1 (en) * | 2007-11-01 | 2009-05-07 | General Electric Company | System and method for minimizing mutual inductance coupling between coils in an electromagnetic tracking system |
US20120080957A1 (en) * | 2008-08-20 | 2012-04-05 | Cooper Emily B | Wireless power transfer apparatus and method thereof |
US20100141261A1 (en) * | 2008-12-05 | 2010-06-10 | Johan Overby | Precise location and orientation of a concealed dipole transmitter |
US20120242160A1 (en) * | 2011-02-17 | 2012-09-27 | Qualcomm Incorporated | Systems and methods for controlling output power of a wireless power transmitter |
US20120248891A1 (en) * | 2011-03-31 | 2012-10-04 | Qualcomm Incorporated | Systems and methods for detecting and protecting a wireless power communication device in a wireless power system |
US20150137746A1 (en) * | 2012-05-14 | 2015-05-21 | Lg Electronics Inc. | Wireless power transfer device and wireless charging system having same |
US20160356601A1 (en) * | 2013-11-06 | 2016-12-08 | Tdm | Hybrid inertial/magnetic system for determining the position and orientation of a mobile body |
US20150285612A1 (en) * | 2014-04-07 | 2015-10-08 | Cgg Services Sa | Electromagnetic receiver tracking and real-time calibration system and method |
US20150309126A1 (en) * | 2014-04-25 | 2015-10-29 | Purdue Research Foundation | Wireless position sensing using magnetic field of single transmitter |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20170017787A1 (en) * | 2015-07-16 | 2017-01-19 | Linkedin Corporation | Automatically securing an electronic device |
US20220082722A1 (en) * | 2016-11-08 | 2022-03-17 | Frederick Energy Products, Llc | Managing vehicle movement in aisles by use of magnetic vectors |
US11726226B2 (en) * | 2016-11-08 | 2023-08-15 | Frederick Energy Products, Llc | Managing vehicle movement in aisles by use of magnetic vectors |
US20180338297A1 (en) * | 2017-05-19 | 2018-11-22 | Microsoft Technology Licensing, Llc | Magnetic tracker with dual-transmit frequency |
US10416333B2 (en) | 2017-05-19 | 2019-09-17 | Microsoft Technology Licensing, Llc | Magnetic tracker with dual-transmit frequency |
US10830572B2 (en) | 2017-10-12 | 2020-11-10 | Google Llc | Hemisphere ambiguity correction in electromagnetic position tracking systems |
CN110133582A (en) * | 2018-02-08 | 2019-08-16 | 阿森松技术公司 | Distortion in compensation electromagnetic tracking system |
Also Published As
Publication number | Publication date |
---|---|
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