Systems for fused acoustic and inertial position determination

Abstract

A synchronization system for an acoustic signal-based and inertial signal-based positioning system is provided, the synchronization system generating a magnetic field as a synchronization signal. A modulated magnetic synchronization signal is transmitted by a transmitter of the positioning system and received by a receiver of the positioning system. The receiver can make an acoustic position determination of the transmitter based on the received modulated synchronization signal, and can make an inertial position determination of the transmitter based on the received inertial signal, so that the acoustic position determination and the inertial position determination are merged.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application Serial No. 62 / 595,562, filed on December 6, 2017, entitled “SYSTEM FOR DETERMINING POSITION AND ORIENTATION OF A MOBILE DEVICE IN 6 DEGREES OF FREEDOM,” and U.S. Patent Application Serial No. 16 / 212,075, filed on December 6, 2018, entitled “SYSTEM FOR FUSINGACOUSTIC AND INERTIAL POSITION DETERMINATION,” both of which are assigned to the assignee herein and are incorporated by reference in their entireties. Technical Field

[0003] The present disclosure relates generally to motion sensors, and more particularly to a transmitter in communication with a receiver, wherein the receiver determines position information of the transmitter. Background Art

[0004] The development of microelectromechanical systems (MEMS) has enabled the incorporation of various sensors into mobile devices, such as cell phones, laptops, tablets, gaming devices, and other portable electronic devices. Non-limiting examples of such sensors include accelerometers, gyroscopes, magnetometers, pressure sensors, microphones, proximity sensors, ambient light sensors, infrared sensors, etc. In addition, sensor fusion processing can be performed to combine data from multiple sensors to provide an improved characterization of the motion or orientation of the device.

[0005] Many applications can benefit from using such sensors to determine the position and / or motion of a portable device. As a non-limiting example, augmented reality (AR) systems and virtual reality (VR) systems typically have a head-mounted display (HMD) for which it would be desirable to provide user input via a portable device, such as a controller worn or held in the user's hand. Accordingly, the HMD can employ position information about the controller for a wide range of user inputs, including recognition of predetermined gestures or creating a correspondence between a physical controller and a virtual object (such as a cursor or pointer).

[0006] Although MEMS technology has allowed widespread use of sensors of the type discussed above, one disadvantage associated with the use of these relatively low-cost devices is performance degradation due to accumulated sensor offsets and biases. In particular, these characteristics can complicate the use of motion sensors for accurate translation determination. One strategy for mitigating the disadvantages associated with motion sensors (including inertial sensors such as accelerometers and gyroscopes) is to provide a complementary position determination system that can be used to correct or enhance the determination of the motion sensor. For example, a positioning system based on acoustic signals can be used with many types of portable devices such as smartphones, tablets, laptops, and controllers in the context of HMD applications discussed above. In fact, a positioning system based on acoustic signals can be used to provide information about the relative position of the controller relative to the HMD and, by extension, relative to the user. A conventional positioning system based on acoustic signals includes a transmitter that transmits an acoustic signal and a receiver that receives the transmitted signal. The receiver measures the propagation time delay of the received acoustic signal, called the time of arrival ("TOA"), and can multiply the TOA by the speed of sound to determine the position of the transmitter. The use of multiple receivers may allow triangulation and / or another form of multilateration and provide determination of position in two or even three dimensions.

[0007] It would be desirable to employ an inertial based positioning system in conjunction with a positioning system based on acoustic signals to exploit the relative strengths of the different systems. To address this need and others, the present disclosure is directed to techniques for fusing position information based on an inertial sensor system with position information from an acoustic system as described in the following materials. Summary of the invention

[0008] As will be described in detail below, the present disclosure includes a positioning system having a transmitter, the transmitter including an acoustic signal transmitter configured to transmit a modulated acoustic signal, a magnetic synchronization signal transmitter configured to transmit a modulated magnetic synchronization signal, and at least one inertial sensor assembly having at least one sensor configured to receive the modulated magnetic synchronization signal as input and configured to transmit an inertial signal. The positioning system also has a receiver, the receiver including an acoustic signal receiver configured to receive the transmitted modulated acoustic signal, a magnetic synchronization signal receiver configured to receive the transmitted modulated magnetic synchronization signal, an inertial signal receiver configured to receive the transmitted inertial signal, and at least one processor configured to receive the modulated acoustic signal from the acoustic signal receiver, the modulated magnetic synchronization signal from the magnetic synchronization signal receiver, and the inertial signal from the inertial signal receiver on the same time domain to determine the position of the transmitter based on a determined time delay of the received modulated synchronization signal, the received modulated acoustic signal, and the received inertial signal.

[0009] The present disclosure also relates to a portable transmitter, which includes an acoustic signal transmitter configured to send a modulated acoustic signal, a magnetic synchronization signal transmitter configured to send a modulated magnetic synchronization signal, and at least one inertial sensor assembly, which has at least one sensor configured to receive the modulated magnetic synchronization signal as input and is configured to send an inertial signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a positioning system having a transmitter and a receiver according to an embodiment.

[0011] Figure 2 is a schematic diagram of a transmitter of a positioning system according to an embodiment.

[0012] Figure 3 is a schematic diagram of a receiver of a positioning system according to an embodiment.

[0013] Figure 4 is a schematic diagram illustrating synchronization between an acoustic signal and an inertial signal according to an embodiment.

[0014] Figure 5 is a schematic timing diagram illustrating synchronization between an acoustic signal and an inertial signal according to an embodiment. DETAILED DESCRIPTION

[0015] At the outset, it should be understood that the present disclosure is not limited to the specifically exemplified materials, architectures, routines, methods or structures, as such, which may vary. Therefore, although many such options similar or equivalent to those described herein may be used in the practice or embodiments of the present disclosure, preferred materials and methods are described herein.

[0016] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the present disclosure only, and is not intended to be limiting.

[0017] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of exemplary embodiments of the present disclosure, and is not intended to represent the only exemplary embodiments in which the present disclosure can be practiced. The term "exemplary" used throughout this description means "used as an example, instance, or illustration," and should not necessarily be interpreted as being preferred or advantageous over other exemplary embodiments. For the purpose of providing a thorough understanding of the exemplary embodiments of the specification, the detailed description includes specific details. It will be apparent to those skilled in the art that the exemplary embodiments of the specification can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the novelty of the exemplary embodiments presented herein.

[0018] For purposes of convenience and clarity only, directional terms such as top, bottom, left, right, up, down, over, above, below, below, rear, back, and front may be used with respect to the drawings or chip embodiments. These and similar directional terms should not be construed in any way to limit the scope of the present disclosure.

[0019] In this specification and claims, it will be understood that when an element is referred to as being "connected to" or "coupled to" another element, it can be directly connected or coupled to the other element, or there can be intervening elements. Conversely, when an element is referred to as being "directly connected to" or "directly coupled to" another element, there are no intervening elements.

[0020] Some parts of the following detailed description are presented in terms of programs, logic blocks, processing and other symbolic representations of the operations on the data bits in the computer memory. These descriptions and representations are the means by which the technical personnel in the field of data processing use to most effectively convey the essence of their work to other technical personnel in the field. In this application, programs, logic blocks, processes, etc. are conceived as self-consistent sequences of steps or instructions that lead to a desired result. The steps are steps that require physical manipulation of physical quantities. Typically, although not required, these quantities take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared, and otherwise manipulated in a computer system.

[0021] It should be kept in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically noted, as will be apparent from the following discussion, it should be appreciated that throughout this application, discussions utilizing terms such as "access," "receive," "send," "use," "select," "determine," "normalize," "multiply," "average," "monitor," "compare," "apply," "update," "measure," "obtain," etc. refer to actions and processes of a computer system or similar electronic computing device that manipulates data represented as physical (electronic) quantities in the computer system's registers and memories and converts it into other data similarly represented as physical quantities in the computer system memories or registers or other such information storage, transmission, or display devices.

[0022] The embodiments described herein may be discussed in the general context of processor-executable instructions residing on some form of non-transitory processor-readable media, such as program modules, executed by one or more computers or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of the program modules may be combined or distributed as desired.

[0023] In the accompanying drawings, a single block may be described as performing one function or multiple functions; however, in actual practice, one or more functions performed by the block may be performed in a single component or across multiple components, and / or may be performed using hardware, using software, or using a combination of hardware and software. In order to clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. The technician may implement the described functionality in varying ways for each specific application, but such implementation decisions should not be interpreted as resulting in a departure from the scope of the present disclosure. Moreover, the exemplary wireless communication device may include components other than the components shown, including well-known components such as processors, memories, and the like.

[0024] Unless specifically described as being implemented in a particular manner, the techniques described herein may be implemented in hardware, software, firmware, or any combination thereof. Any features described as modules or components may also be implemented together in an integrated logic device, or separately as discrete but interoperable logic devices. If implemented in software, the techniques may be implemented at least in part by a non-transitory processor-readable storage medium comprising instructions that, when executed, perform one or more of the methods described above. The non-transitory processor-readable data storage medium may form part of a computer program product, which may include packaging materials.

[0025] Non-transitory processor-readable storage media may include random access memory (RAM), such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, other known storage media, etc. In addition or alternatively, the technology may be implemented at least in part by a processor-readable communication medium that carries or transmits code in the form of instructions or data structures and which can be accessed, read and / or executed by a computer or other processor. For example, a carrier wave may be used to carry computer-readable electronic data, such as those used in sending and receiving e-mails or in accessing networks such as the Internet or a local area network (LAN). Of course, many modifications may be made to this configuration without departing from the scope or spirit of the claimed subject matter.

[0026] Various illustrative logic blocks, modules, circuits, and instructions described in conjunction with the embodiments disclosed herein may be executed by one or more processors, such as one or more sensor processing units (SPUs), digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), application-specific instruction set processors (ASIPs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. As used herein, the term "processor" may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within a dedicated software module or hardware module configured as described herein. Likewise, the technology may be fully implemented in one or more circuits or logic elements. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a motion processor unit (MPU) or a sensor processing unit (SPU) with a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with an MPU / SPU core, or any other such configuration.

[0027] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0028] Finally, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise.

[0029] Details regarding one embodiment of a system 100 incorporating features of the present disclosure are provided in Figure 1102 and receiver 104 are depicted as high-level schematic blocks. As will be appreciated, the transmitter 102 and receiver 104 are implemented as portable devices or apparatuses, such as controllers and head-mounted displays (HMDs). Although both the transmitter 102 and receiver 104 are typically movable in space by a user, the context of the present disclosure involves making a relative position determination of the transmitter 102 relative to the receiver 104 as an indication of its position, motion, and / or orientation in space. As used herein, unless otherwise indicated, the term "position" may refer to either or both of position and orientation. In addition, assuming that the motion is a change in position or orientation, the position information may also include motion information. For example, a given orientation and / or position sequence may be associated with a predetermined gesture, which may be recognized to provide user input to the system 100. Similarly, a given orientation and / or position sequence may also be mapped to a virtual object for controlling the object as user input to the system 100. Accordingly, the receiver 104 may be a dedicated HMD or other AR / VR device, or may be another portable device with capabilities that can be exploited to provide some degree of functionality associated with the HMD, including a mobile phone (e.g., a cellular phone, a phone operating on a local network, or any other telephone handset), a wired phone (e.g., a phone attached by a wire), a personal digital assistant (PDA), a video game console, a video game controller, a navigation device, an activity or fitness tracker device (e.g., a bracelet or clip), a smart watch, other wearable device, a mobile Internet device (MID), a personal navigation device (PND), a digital camera, a digital video camera, binoculars, a telephoto lens, a portable music, video or media player, a remote control or other handheld device, or a combination of one or more of these devices. The transmitter 102 is a device used in conjunction with the receiver 104, such as a dedicated controller or other input device, or may also be another type of portable device, including any of the portable devices noted above that provide this functionality. Furthermore, multiple transmitters 102 may be used, such as two or more separate controllers, each of which is capable of independent movement, and each of which is capable of providing user input alone or in conjunction with one or more other transmitters 102. More generally, a transmitter 102 is a device in communication with a receiver 104 that would benefit from determining its position, orientation, or motion relative to the receiver, e.g., for the purpose of providing user input.

[0030] As shown, the transmitter 102 includes a transmitter processor 106, which may be one or more microprocessors, central processing units (CPUs), or other processors, to run software programs, which may be stored in memory 108, associated with the functionality of the device 100. The transmitter 102 includes at least one sensor component, as shown here in the form of an integrated sensor processing unit (SPU) 110, which features a sensor processor 112, a memory 114, and an internal sensor 116. The memory 114 may store algorithms, routines, or other instructions for processing data output by the internal sensor 116 and / or other sensors as described below using the logic or controller of the sensor processor 112, and storing raw data and / or motion data output by the internal sensor 116 or other sensors. Depending on the architecture, the memory 114 or the memory 108, or a combination, may be used to store data, executable instructions, or any other suitable operations involving the transmitter 102. The internal sensor 116 may be one or more sensors for measuring the motion of the transmitter 102 in space, including inertial sensors such as accelerometers and gyroscopes, or other motion sensors, including magnetometers, pressure sensors, or others. Depending on the configuration, the SPU 110 measures one or more rotation axes and / or one or more acceleration axes of the device. In one embodiment, the internal sensor 116 may include a rotational motion sensor or a linear motion sensor. For example, the rotational motion sensor may be a gyroscope to measure angular velocity along one or more orthogonal axes, and the linear motion sensor may be an accelerometer to measure linear acceleration along one or more orthogonal axes. In one aspect, three gyroscopes and three accelerometers may be employed, wherein the sensor readings are sent to the receiver 104, so that a sensor fusion operation may be performed as described below to combine data from the internal sensors 116 to provide a six-axis motion determination or six degrees of freedom (6DOF). Alternatively or additionally, the sensor processor 112 or other processing resources of the transmitter 102 may perform sensor fusion. As desired, the internal sensor 116 may be implemented using a micro-electromechanical system (MEMS) to be integrated in a single package with the SPU 110. Exemplary details regarding suitable configurations for the transmitter processor 106 and the SPU 110 may be found in commonly owned U.S. Patent Nos. 8,250,921, issued on August 28, 2012, and 8,952,832, issued on February 10, 2015, which are hereby incorporated by reference in their entireties. Suitable implementations of the SPU 110 in the transmitter 102 may be obtained from InvenSense, Inc. of San Jose, California. In some embodiments, one or more motion algorithm layers may provide motion algorithms for low-level processing of raw sensor data provided from internal or external sensors.Additionally, a sensor device driver layer may provide a software interface to the hardware sensors of transmitter 102. Some or all of these layers may be provided in memory 108 for access by transmitter processor 106, in memory 114 for access by sensor processor 112, or in any other suitable architecture.

[0031] Alternatively or additionally, the transmitter 102 may implement a sensor component in the form of an external sensor 118. This is optional and not required in all embodiments. The external sensor may represent one or more sensors as described above, such as an accelerometer and / or a gyroscope. As used herein, "external" means not integrated with the SPU 110 and may be remote or local relative to the transmitter 102. Similarly, alternatively or additionally, the SPU 110 may receive data from an auxiliary sensor 120 that is configured to measure one or more aspects of the environment around the transmitter 102. This is optional and not required in all embodiments. For example, a pressure sensor and / or a magnetometer may be used to improve the motion determination performed using the internal sensor 116. In one embodiment, the auxiliary sensor 120 may include a magnetometer that measures along three orthogonal axes and outputs data that is to be fused with gyroscope and accelerometer inertial sensor data to provide a nine-axis motion determination. In another embodiment, the auxiliary sensor 120 may also include a pressure sensor to provide a height determination that may be fused with other sensor data to provide a ten-axis motion determination. Again, sensor fusion involving this optional data from one or both of the external sensor 118 and the auxiliary sensor 120 may be performed at the receiver 104, at the transmitter 102, or at both. Although described in the context of one or more sensors being MEMS-based, the techniques of the present disclosure may be applied to any sensor design or implementation.

[0032] In the illustrated embodiment, the transmitter processor 106, memory 108, SPU 110 and other components of the transmitter 102 may be coupled via bus 122, while the sensor processor 112, memory 114, internal sensor 116 and / or auxiliary sensor 120 may be coupled via bus 124, each of which may be any suitable bus or interface, such as a peripheral component interconnect express (PCIe) bus, a universal serial bus (USB), a universal asynchronous receiver / transmitter (UART) serial bus, a suitable advanced microcontroller bus architecture (AMBA) interface, an inter-integrated circuit (I2C) bus, a serial digital input output (SDIO) bus, a serial peripheral interface (SPI), or other equivalents. Depending on the architecture, different bus configurations may be employed as desired. For example, additional buses may be used to couple the various components of the transmitter 102, such as by using a dedicated bus between the transmitter processor 106 and the memory 108.

[0033] In turn, the receiver 104 may include a receiver processor 126 and a memory 128 to implement any desired operations, coupled via a bus 129, which also couples other functional components of the receiver 104. As described in further detail below, this may include using motion sensor data from the transmitter 102, including inertial sensor information, to determine any suitable aspects of information about the relative position, orientation, and / or motion of the transmitter 102 relative to the receiver 104 by executing instructions stored in the memory 128, as indicated by the inertial module 130. Further, the memory 128 may also include instructions, represented as an acoustic module 132, to process information associated with the acoustic signal-based positioning of the transmitter 102, as also described in further detail below. Still further, the memory 128 may include a fusion module 134, which may include instructions for integrating information determined by the inertial module 130 and the acoustic module 132. In some embodiments, such as when the receiver 104 is used as an HMD, the display 136 may be configured to deliver content to the user, such as using stereo information to simulate a three-dimensional virtual or augmented reality environment. In this schematic representation, the display 136 may also be considered to deliver audio information, such as through a suitable speaker system. The receiver 104 may also include a sensor processing unit, such as SPU 110, having internal sensors such as, for example, inertial sensors, and may also include external sensors, such as external sensors 118 (not shown). As such, these sensors in the receiver 104 may be used to determine the position, location, and / or orientation of the receiver 104, independently or dependent on the transmitter 102.

[0034] Multiple layers of software may be provided in the memory 128, which may be any combination of computer-readable media (such as electronic memory) or other storage media (such as hard disks, optical disks, etc.) for use with the receiver processor 126. For example, an operating system layer may be provided for the transmitter 102 to control and manage system resources in real time, enable the functions of application software and other layers, and interface the application with other software and functions of the receiver 104. Similarly, different software applications may be provided, such as menu navigation software, games, camera function control, navigation software, communication software (such as telephone or wireless local area network (WLAN) software), or any of a variety of other software and function interfaces. In some embodiments, multiple different applications may be provided on a single receiver 104, and in some of those embodiments, multiple applications may be run simultaneously.

[0035] Algorithms, routines, or other instructions for processing sensor data may be employed by the inertial module 130 to perform any operations associated with the techniques of this disclosure, such as determining the motion, position, distance, and / or orientation of the portable transmitter 102 relative to the receiver 104. Determining the motion or orientation of the portable transmitter 102 may involve sensor fusion or similar operations performed by the receiver processor 126. Such determinations may be absolute or relative, as desired. Examples of determining position changes based on motion sensors may be found in co-pending, commonly owned U.S. patent application Ser. No. 14 / 537,503, filed Nov. 10, 2014, which is hereby incorporated by reference in its entirety.

[0036] As noted above, the transmitter 102 and the receiver 104 may include a positioning system based on acoustic signals, such that the transmitter 102 includes a synchronization signal transmitter 138 and an acoustic signal transmitter 140. More details about suitable positioning systems based on acoustic signals can be found in U.S. Patent No. 9,897,682, which is hereby incorporated herein by reference in its entirety. The acoustic signal transmitter 138 transmits a modulated ultrasonic signal, such as a modulated continuous ultrasonic signal. For example, the signal range of the modulated continuous ultrasonic signal can vary between about 20kHz and 80kHz and / or up to 200kHz. The modulated continuous ultrasonic signal includes a modulated continuous wave ultrasonic signal having a carrier signal portion and a baseband signal portion modulated onto the carrier signal portion. Similarly, the receiver 104 includes a synchronization signal receiver 142 and an acoustic signal receiver 144 accordingly. In some embodiments, the acoustic signal receiver 140 can be one or more microphones. In some embodiments, the sound receiver 144 may be able to receive the acoustic signal emitted by the acoustic signal transmitter 140.

[0037] For example, the acoustic module 132 can compare the received signal with the expected signal based on instructions stored in the memory 128 and the stored expected signal or the expected signal generated by the receiver processor 126. In some embodiments, the expected signal can correspond to a predefined modulated continuous signal or a calculated copy of the modulated continuous wave signal stored in the memory 128 based on the template, model and / or feature stored in the memory 128. In some embodiments, the receiver processor 126 can use carrier and baseband correlation to compare the received acoustic signal. Comparing the received acoustic signal with the expected acoustic signal is further discussed in U.S. Patent No. 8,184,504, which is hereby incorporated by reference in its entirety.

[0038] The synchronization signal transmitter 138 transmits a modulated synchronization signal that can be detected by the synchronization receiver 144 and used by the acoustic module 132 to initiate a delay count for receiving a modulated acoustic signal from the acoustic signal transmitter 140, which can be slower than the modulated synchronization signal sent from the synchronization signal transmitter 106. The delay count can then be used to determine the time delay of the received acoustic signal, which can be used together with the propagation speed of the acoustic signal to determine the distance between the transmitter 102 and the receiver 104. In some embodiments, the transmitted acoustic signal has a known speed, such as the speed of sound in air. In some embodiments, the modulated synchronization signal can have a very small time delay relative to the distance between the transmitter 102 and the receiver 104. The received modulated synchronization signal can also be used to synchronize the clocks between the transmitter 102 and the receiver 104 to compensate for clock errors and / or offsets. In some embodiments, a synchronization mechanism is included in the receiver 104, which can be stored in, for example, the memory 128 and executed by the receiver processor 126.

[0039] In some embodiments, the acoustic module 132 may be able to determine the position of the transmitter 102 relative to the receiver 104 by measuring the time delay of the transmitted acoustic signal through the line of sight (LOS). In some embodiments, the position of the transmitter 102 relative to the receiver 104 can be determined based on the carrier signal and the baseband signal from the received acoustic signal. In some embodiments, the acoustic module 132 includes a fast Fourier transform (FFT) capability and can be used to perform phase and amplitude analysis of the received acoustic signal. In addition, the acoustic module 132 can compare the received acoustic signal with the expected signal, which can be calibrated based on the difference in phase, amplitude and / or group delay. Accordingly, the position information including the distance between the transmitter 102 and the receiver 104 can be determined based on the time delay of the acoustic signal from the transmitter 102 to the receiver 104 on the LOS, for example, the shortest distance between the transmitter 102 and the receiver 104. The position of the transmitter 102 can be determined based on triangulation of the distance determined from the receiver 104 or another form of multi-lateration. To determine the position in additional dimensions, additional receiving devices and / or additional acoustic signal receivers 144 may be used. In some embodiments, the gain is processed using summation. Based on the received signals, the acoustic module 132 may calculate time delays based on the carrier and baseband signals, and may perform triangulation or other forms of multilateration to determine the position of the transmitting device as a function of time.

[0040] According to the technology of the present disclosure, a positioning system based on an acoustic signal can use a modulated magnetic synchronization signal, wherein the synchronization signal transmitter 138 is the magnetic synchronization signal transmitter 106, and the synchronization signal receiver 142 is the magnetic synchronization signal receiver 106. The magnetic synchronization signal transmitter 138 transmits a magnetic synchronization signal received by the magnetic synchronization signal receiver 142, so that the magnetic synchronization signal transmitter 138 is magnetically coupled to the magnetic synchronization signal receiver 142. In some embodiments, the modulated magnetic synchronization signal can have the same modulation as the acoustic signal transmitted by the acoustic signal transmitter 140.

[0041] The transmitter 102 and the receiver 104 may employ communication modules 146 and 148, respectively, to transmit location information obtained from sensors in the SPU 110 in the form of raw sensor data, determinations obtained through fusion operations, or any other relevant information. In some embodiments, the communication module 126 may employ a wireless local area network (WLAN) compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 protocol. Other systems may be used, including cellular-based and WLAN technologies, such as Universal Terrestrial Radio Access (UTRA), Code Division Multiple Access (CDMA) networks, Global System for Mobile Communications (GSM), IEEE 802.16 (WiMAX), Long Term Evolution (LTE), other transmission control protocols, communications based on Internet Protocol (TCP / IP) packets, and the like. In some embodiments, multiple communication systems may be employed to utilize different capabilities. Generally, communications involving higher bandwidths may be associated with greater power consumption, such that other channels may utilize lower power communication protocols such as BLUETOOTH®, ZigBee®, ANT, and the like. In addition, while wireless communications allow for greater freedom of movement, depending on the embodiment, wired connections may be used for the communication of some information between the various components of the system. In addition, the transmitter 102 and the receiver 104 can communicate directly or indirectly, such as through one or more interconnected networks. As will be appreciated, various systems, components and network configurations, topologies and infrastructures can be employed, such as client / server, peer-to-peer or hybrid architectures, to support a distributed computing environment. For example, computing systems can be connected together through wired or wireless systems, through local area networks or widely distributed networks. Currently, many networks are coupled to the Internet, which provides an infrastructure for widely distributed computing and covers many different networks, although any network infrastructure can be used for exemplary communications that are easy to make for the techniques described in various embodiments.

[0042] Figure 2 is a diagram illustrating various aspects of transmitter 102 consistent with some embodiments. Figure 2As shown, the acoustic signal transmitter 138 may include one or more speakers 200-1-200-n (collectively referred to as speakers 200) capable of transmitting acoustic signals. In some embodiments, the speakers 200 may each be capable of transmitting a modulated continuous ultrasonic signal with a signal range between approximately 20 and 80 kHz and / or up to 200 kHz. In some embodiments, the modulated continuous ultrasonic signal transmitted by the speaker 200 may include a carrier signal portion and a baseband signal portion modulated onto the carrier signal portion. In addition, the speaker 200 may be oriented at different locations, different angles, different orientations, etc. on the transmitter 102 so as to transmit the ultrasonic signal to the receiver 104 at different distances to allow the ultrasonic signal to be triangulated to determine the position of the transmitter 102 relative to the receiver 104. In addition, the speaker 200 may be located at different locations on the transmitter 102 to transmit the ultrasonic signal for determining the attitude or angle of the transmitter 102 relative to the receiver 104.

[0043] The magnetic synchronization signal transmitter 138 may be or include a coil or transformer coupled by a power source drive. In some embodiments, the magnetic synchronization signal transmitter 138 may correspond to a coil or transformer coupled to the acoustic signal transmitter 140 for enhancing the acoustic signal. The magnetic field or signal generated by the magnetic synchronization signal transmitter 138 may establish magnetic coupling with the detection magnetic synchronization signal receiver 142. The generated field that establishes magnetic coupling acts as a modulated magnetic synchronization signal between the magnetic synchronization signal transmitter 138 and the magnetic synchronization signal receiver 142. In some embodiments, the modulated magnetic synchronization signal or field provides a timing retrieval accuracy of less than 30ns. The magnetic synchronization signal transmitter 138 may also generate a spread spectrum modulated magnetic synchronization signal by extending the energy of the field across the frequency band to increase the redundancy and robustness of the generated modulated magnetic synchronization signal. In some embodiments, the larger the extended bandwidth, the more accurate the timing recovery achieved by synchronization. In some embodiments, the magnetic synchronization signal transmitter 138 may be coupled to a power source different from the acoustic signal transmitter 140, and therefore coupled to an electrical path or channel separated from the acoustic signal transmitter 140.

[0044] The acoustic signal transmitter 140 and the magnetic synchronization signal transmitter 138 may be coupled to a bandpass filter 202, which may be capable of filtering the modulated signal generated by the modulator 203 so that the acoustic component of the modulated signal is sent to the acoustic signal transmitter 140 and the non-acoustic component of the signal is sent to the magnetic synchronization signal transmitter 138. In some embodiments, the modulator 203 may be a delta-sigma modulator capable of modulating a carrier signal portion onto a baseband signal portion. The bandpass filter 202 may be capable of filtering out-of-band components of sigma-delta from the modulated signal generated by the modulator 203 to reduce current consumption. In addition, both the baseband signal portion and the carrier signal portion may be modulated to provide improved timing accuracy and reduced interference. In some embodiments, both the magnetic synchronization signal and the acoustic signal may be modulated by the modulator 203. In some embodiments, the magnetic synchronization signal and the acoustic signal may be modulated by the modulator 203 in at least one of amplitude, frequency, and phase. In some embodiments, the magnetic synchronization signal and the acoustic signal may be modulated with a modulation period that is large enough to allow determination of timing within the modulation period.

[0045] The modulator 203 may be coupled to the transmitter processor 106, which is further coupled to the memory 108 or other suitable processing resources of the transmitter 102, and the power supply 210. Accordingly, the transmitter processor 106 may control the modulator 203 and generate signals for modulation by the modulator 203 and transmission by the acoustic signal transmitter 138 and the magnetic synchronization signal transmitter 140. The power supply 210 may be a DC power supply, an AC power supply, and may also include a battery. In accordance with some embodiments, if the acoustic signal transmitter 140 has a large capacitance component, the power supply 210 may be able to drive the magnetic synchronization signal transmitter 138 to have a matching inductance. In some embodiments, the inductance value may be fixed by the magnetic synchronization signal transmitter 138. Using a matching inductive driver may make the center frequency of the modulation also the center frequency of the resonator formed by the inductive driver and the acoustic signal transmitter 140, thereby improving the efficiency and effectiveness of the acoustic signal transmitter 140.

[0046] Figure 3 is a diagram illustrating various aspects of receiver 104 consistent with some embodiments. Figure 3As shown in , the acoustic signal receiver 144 may include acoustic sensors 302-1-302-n (collectively referred to as acoustic sensors 302). In some embodiments, the acoustic sensor 302 may be a microphone capable of detecting ultrasonic signals, and in further embodiments, may be a micro-electromechanical system (MEMS) microphone. The acoustic signal receiver 144 may include as many acoustic sensors 302 as required by the positioning requirements, but may generally include: a single acoustic sensor 302 for determining the position of the transmitter 102 in one dimension, two acoustic sensors 302 for determining the position of the transmitter 102 in two dimensions, and three acoustic sensors 302 for determining the position of the transmitter 102 in three dimensions. Depending on the relative position and orientation of the transmitter 102 and the receiver 104, additional acoustic sensors 302 may also be used to account for the possibility that one or more other acoustic sensors are not in a suitable LOS relationship.

[0047] Figure 3 Circuits with similar inputs are illustrated. In this case, the received acoustic and magnetic signals can be interchanged without adversely affecting system performance. The same timing domain as used for the magnetic input is used for circuits that sample microphone outputs, such as audio codecs. Audio codecs typically have a programmable gain amplifier followed by an A / D converter. Samples from the A / D converter are streamed to the audio processor. In some embodiments, acoustic and magnetic signals are sampled simultaneously in the same time domain of the audio codec. Sampling the magnetic signal in the same time domain in synchronization with the audio sensor provides: maintaining precise timing between the magnetic and acoustic signals. Sampling the magnetic (or RF) signal in the RE-front IC will not allow the same level of synchronization as sampling the two signals in the same time domain as in the audio codec. For example, the RF circuit may have a timing offset, and the acoustic sample will have some time offset due to the different times at which the jumper connection jumpstarts the RF circuit and the audio circuit. This is what "same time domain" means.

[0048] like Figure 3 As shown in FIG. 1 , the magnetic synchronization signal receiver 142 can be coupled to an input similar to the acoustic signal receiver 144 so that the modulated acoustic signal received by the acoustic sensors 302-1 to 302-n and the modulated magnetic synchronization signal received by the magnetic synchronization receiver 142 are provided for processing on the same timing domain. Consistent with some embodiments, the modulated magnetic synchronization signal can be generated by the magnetic synchronization signal transmitter 138 and the magnetic synchronization receiver 142, wherein the magnetic synchronization receiver 142 includes a coil or similar feature for detecting the modulated magnetic synchronization signal and establishing magnetic coupling. Although in FIG. Figure 3Only one magnetic synchronization receiver 142 is shown, however, in some embodiments additional synchronization receivers for receiving additional modulated magnetic synchronization signals or other synchronization signals may be included.

[0049] The modulated acoustic signal and the modulated magnetic synchronization signal may be provided to a coder-decoder (CODEC) 304. In some embodiments, the CODEC 304 may act as a coprocessor to the receiver processor 126. The CODEC 304 may include a preamplifier, a digitizer 310, and a filter 312. In some embodiments, the CODEC 304 may have a ratio Figure 3 More or less components, modules, circuits, etc. shown in the CODEC 304 may include, for example, a decoder. The preamplifier 306 may amplify the received modulated acoustic signal and the modulated magnetic synchronization signal. The decoder 308 may then decode the information encoded by the encoder 204 as the modulated acoustic signal and the modulated magnetic synchronization signal. Then, the decoded acoustic signal and the magnetic synchronization signal may be digitized by the digital converter 310. In some embodiments, the digital converter 310 may be an analog-to-digital converter (ADC) that is capable of digitizing the received signal to output to the receiver processor 126. The CODEC 304 may also include a filter 312, which may include one or more filtering components. Typically, the filter removes out-of-band components to avoid aliasing during extraction. One or more filtering components may be able to dynamically filter out defects or anomalies in the received acoustic signal and the received modulated magnetic synchronization signal, such as magnetic spikes or spurs. In addition, if the magnetic synchronization signal is modulated with a sufficiently large bandwidth, the filter 312 may improve the quality of the received modulated magnetic synchronization signal without adversely affecting the timing of the synchronization signal. In some embodiments, filter 312 may be a decimation filter. In addition, filter 312 may be located external to CODEC 304 so that, in some embodiments, the received modulated acoustic signal and modulated magnetic synchronization signal are filtered in parallel with the processing and conditioning performed by CODEC 304. Figure 3 3, CODEC 304 may include a digital core 308 that receives signals from filter 312 and provides them to receiver processor 126. Receiver processor 126 may be coupled to CODEC 304 via bus 129 to receive signals from CODEC 304, which may also be coupled to memory 128 and digital inputs and outputs 314. Digital EO 314 may include any component capable of receiving a digital output from or providing a digital input to receiver processor 126.

[0050] As another example, the receiver processor 126 may be capable of executing instructions for increasing the signal-to-noise ratio of the received synchronization signal and acoustic signal, which may include a signal summation algorithm, a differential correlation summation algorithm, and a linear fitting algorithm. Although not shown, the receiver 104 may include a phase-locked loop (PLL), a delay-locked loop (DLL), or a digital phase-locked loop (DPLL) for increasing the signal-to-noise ratio of the received synchronization signal and acoustic signal. In some embodiments, the delay or phase-locked loop may be a circuit included in the receiver 104, while in other embodiments, the loop may be encoded as an algorithm executed by the receiver processor 126. In some embodiments, the receiver processor 126 may be capable of searching for the best offset and delay given an error cost function. In some embodiments, the signal-to-noise ratio may be increased by adding an additional magnetic synchronization signal receiver 142 to the receiver 104 to improve the reception of the modulated magnetic synchronization signal. In addition, the receiver processor 126 may determine a received signal strength indication (RSSI) by determining the signal level of the received modulated magnetic synchronization signal, which will be used as a measure of the distance between the transmitter 102 and the receiver 104.

[0051] According to some embodiments, the receiver 104 may include a Figure 3 More or fewer components may be shown. Figure 3 Other components shown in the figure may be coupled to bus 129 instead of being directly coupled to one or more other components. Figure 3 The components shown in the may be shown as being part of a single system, but may also be part of a system in which the components are separate but coupled and in communication. Figure 3 The components shown in are shown as examples of components in a receiver 104 that are capable of performing the embodiments disclosed herein. However, the receiver 104 may have more or fewer components and still be capable of performing some of the embodiments disclosed herein.

[0052] Therefore, consistent with some embodiments, the acoustic module 132 can determine the location information of the transmitter 102 based on the transmitted modulated acoustic positioning signal and the modulated magnetic synchronization signal. The modulated acoustic positioning signal is received by the acoustic sensor 302 from the transmitter 102, which in some embodiments can generate an electrical signal from the received modulated acoustic signal for processing. The received modulated magnetic synchronization signal can be received by the magnetic synchronization signal receiver 144, which can include a coil or a hollow cylinder wrapped around a core, so that an electrical signal is generated for processing. In some embodiments, the received modulated acoustic signal and the received modulated magnetic signal can be received and sent for processing in the same time domain, so that the received modulated acoustic signal and the received modulated magnetic signal can be processed in the same domain. The received modulated acoustic signal and the modulated magnetic synchronization signal can be decoded by the decoder 308 of the CODEC 304. In some embodiments, decoding can include extracting encoded information from the received modulated acoustic and modulated magnetic synchronization signals. The decoded signal can then be digitized by the digital converter 310. Based on the received digitized signal, the acoustic module 132 can measure the time delay between the received version of the acoustic signal and the received version of the modulated magnetic synchronization signal. In some embodiments, each acoustic sensor 302 can receive a version of the acoustic signal transmitted by the speaker 200 of the transmitter 102. In addition, each acoustic sensor 302 can receive a version of the acoustic signal transmitted by a different speaker 200 of the transmitting device. Due to the speed of the acoustic signal, there is an associated flight time associated with each received acoustic signal, so that the acoustic signal can be received after a certain time delay from the start of the transmission. Since the modulated magnetic synchronization signal can be received by the magnetic synchronization signal receiver 110 almost immediately, the received modulated magnetic synchronization signal can be used to determine the time delay associated with the flight time of each version of the received acoustic signal.

[0053] The measured time delay can then be converted into at least a first distance and a second distance. In some embodiments, the acoustic module 132 can use each version of the received acoustic signal to determine the time delay, and can use each time delay to determine the distance by knowing the speed and time delay of the acoustic signal. The acoustic module 132 can then triangulate the first distance and the second distance to determine the position of the transmitter 102. Based on the number of speakers 200 in the transmitter 102 and the number of acoustic sensors 302 in the receiver 104, the determined position can have a one-dimensional, two-dimensional, or three-dimensional position. In addition, in addition to the position, the attitude or angle of the transmitter 102 can also be determined based on the position of the speaker 200.

[0054] Thus, embodiments as described herein may provide an acoustic signal based positioning system that may be synchronized by establishing a magnetic coupling between a transmitter and a receiver. The magnetic coupling may be established by a modulated magnetic synchronization signal generated by a synchronization signal generator that may be more easily integrated with a transmitter device than conventional synchronization systems. Moreover, the modulated magnetic synchronization signal may be received by a synchronization signal receiver that may be integrated within the receiver and received on the same path as the acoustic signal, thereby eliminating the need for dedicated synchronization signal processing hardware.

[0055] From the above material, it will be appreciated that the inertial module 130 determines position information about the transmitter 102 based on motion sensor data (such as inertial sensor data from the SPU 110), while the acoustic module 132 determines position information about the transmitter 102 based on received acoustic signal sounds and synchronization signals. Accordingly, the fusion module 134 functions to combine the position information determined by each of the inertial module 130 and the acoustic module 132 in order to improve the characterization of the relative position, motion, and / or orientation of the transmitter 102 relative to the receiver 104. In order to more accurately combine the position information determined by these separate systems, it is necessary to be able to correlate the relevant (respect) timing information of each system and thereby synchronize the systems. According to the techniques of the present disclosure, this is achieved by combining the modulated magnetic synchronization signal of the acoustic signal-based positioning system with the inertial-based positioning system.

[0056] exist Figure 4 The coordination of an acoustic signal-based positioning system and an inertial-based positioning system is schematically depicted in FIG. Figure 4 Aspects of each system implemented in the transmitter 102 are shown. Specifically, the output of the acoustic signal transmitter 140, represented here by four indicated channels of modulated acoustic signals, is aligned with the output of the magnetic synchronization signal transmitter 138 on the magnetic channels so as to represent synchronization of the modulated acoustic and magnetic signals. The acoustic signal transmitter 140 and the magnetic synchronization signal transmitter 138 may be driven by a common clock CLK1, such as that associated with the transmitter processor 106. However, the SPU 110 and its sensor data may utilize different clocks, such as, as indicated, CLK2. CLK2 may be an internal clock generated within the SPU 110. Similar to the clock difference between the transmitter 102 and the receiver 104 discussed above, in order to accurately fuse the position information based on the motion sensor data and the position information based on the acoustic sensor data, any clock offset and / or clock error must be corrected. Therefore, the magnetic synchronization signal transmitter 138 may output signals to the SPU 110 simultaneously, such as Figure 4The sync channel in the sync signal transmitter 138 can output a sync pulse, and as can be seen, the rising edge of the sync channel signal can be aligned with the start of the acoustic signal on both the magnetic channel and the acoustic channel. The sync channel can be connected to a dedicated sync input pin on the SPU or sensor, and the SPU 110 can be configured to detect the rising edge on the sync channel. The SPU 110 can then determine any time difference between its sensor reading and the magnetic sync signal. Figure 5 The details of sensor data synchronization are schematically shown in the timing diagram of . The top trace indicates a repeating pattern or modulation pattern of the acoustic signal sent by the acoustic signal transmitter 140 on the acoustic channel. Next, a magnetic channel is shown, where a modulated magnetic synchronization signal has a pulse aligned with the start of the acoustic signal pattern as sent by the magnetic synchronization signal transmitter 138. The rising edge of the synchronization channel as input to the SPU 110 on the dedicated synchronization input pin is shown as an upward arrow aligned with the start of the pulse of the modulated magnetic synchronization signal. Accordingly, the SPU 110 can determine the timing delay Δ between the sensor data sample (also indicated as an upward arrow) and the synchronization signal. The timing delay Δ is determined by starting a counter when a rising edge is detected on the dedicated synchronization input pin, and the counter stops at the first sensor data after the synchronization signal. As shown in Figure 5 As indicated in the bottom trace of , the sensor data of the SPU 110 is time stamped based on the internal clock CLK2 of the SPU 110. By combining the timing delay Δ with the timestamp of the first received sensor data, the timestamp of the synchronization signal based on the internal clock CLK2 of the SPU 110 is determined. The timestamped sensor data from the SPU 110 is then transmitted from the transmitter 102 to the receiver 104 along with the timestamped synchronization signal, for example, using the communication modules 146 to 148. The transmission may be performed using, for example, a Bluetooth protocol. The data transmitted to the receiver 104 includes the sensor data and the associated timestamp data, and when the synchronization signal is detected, also includes the timestamp of the received synchronization signal or the timing delay Δ relative to the received synchronization signal. The received data and timestamps are then used by the fusion module 134 so that the position information determined by the inertial module 130 can be aligned with the position information determined by the acoustic module 132. By comparing the timestamp of the synchronization signal based on the clock CLK2 of the SPU 110 and the timing information of the magnetic synchronization signal received at the receiver 104, the sensor data with the timestamp can be aligned with the acoustic data received at the receiver 104. Figure 5In the embodiment shown in , the acoustic signal pattern repeats, and at the beginning of the next pattern, another pulse is sent by the magnetic synchronization signal transmitter 138. Similarly, another synchronization signal is sent to the SPU 110 so that a new timing delay Δ can be determined and applied in combination with subsequent sensor data timestamps.

[0057] According to the above discussion, the positioning system of the present disclosure may include: a transmitter: a transmitter having an acoustic signal transmitter configured to transmit a modulated acoustic signal; a magnetic synchronization signal transmitter configured to transmit a modulated magnetic synchronization signal; and at least one inertial sensor assembly having at least one sensor configured to receive the modulated magnetic synchronization signal as input and configured to transmit an inertial signal. The positioning system also has a receiver, which includes: an acoustic signal receiver configured to receive the transmitted modulated acoustic signal; a magnetic synchronization signal receiver configured to receive the transmitted modulated magnetic synchronization signal; an inertial signal receiver configured to receive the transmitted inertial signal; and at least one processor configured to receive the modulated acoustic signal from the acoustic signal receiver, the modulated magnetic synchronization signal from the magnetic synchronization signal receiver, and the inertial signal from the inertial signal receiver in the same time domain to determine the position of the transmitter based on the determined time delay of the received modulated synchronization signal, the received modulated acoustic signal, and the received inertial signal.

[0058] On the one hand, the at least one processor can be configured to determine the position of the transmitter as follows: make an acoustic position determination of the transmitter based on a determined time delay of a received modulated synchronization signal and a received modulated acoustic signal, make an inertial position determination of the transmitter based on a received inertial signal, and fuse the acoustic position determination and the inertial position determination.

[0059] In one aspect, acoustic position determination and inertial position determination are synchronized based on a modulated magnetic synchronization signal.

[0060] In one aspect, the inertial sensor assembly can be configured to receive as input an indication of the start of a modulated magnetic synchronization signal and determine timing data relative to the inertial signal. The timing data can be a time delay between the received indication of the start of the modulated magnetic synchronization signal and the acquired inertial sensor samples. The inertial sensor assembly can also determine a timestamp for the received indication of the start of the modulated magnetic synchronization signal based on the time delay.

[0061] In one aspect, the inertial sensor assembly can have at least one of an accelerometer and a gyroscope. The inertial sensor assembly can also have a magnetometer.

[0062] In one aspect, the receiver can be a virtual reality display and / or an augmented reality display. The transmitter can be a handheld controller.

[0063] On the one hand, the positioning system can have: an additional acoustic signal transmitter capable of independent movement, which is configured to send a modulated acoustic signal; a magnetic synchronization signal transmitter, configured to send a modulated magnetic synchronization signal; and at least one inertial sensor assembly, having at least one sensor that is synchronized with the modulated magnetic synchronization signal and configured to send an inertial signal.

[0064] On the one hand, radio frequency communication can be used to send the inertial signal.

[0065] In the described embodiments, a chip is defined as including at least one substrate, typically formed of a semiconductor material. A single chip may be formed of multiple substrates, where the substrates are mechanically bonded to maintain functionality. A multi-chip includes at least two substrates, where the two substrates are electrically connected, but do not require mechanical bonding. The package provides electrical connections between bonding pads on the chip and metal leads that can be soldered to a PCB. The package typically includes a substrate and a cover. An integrated circuit (IC) substrate may refer to a silicon substrate with circuits, typically CMOS circuits. In some configurations, a portion of the substrate, referred to as a MEMS cover, provides mechanical support for the MEMS structure. The MEMS structure layer is attached to the MEMS cover. The MEMS cover is also referred to as an operating substrate or operating wafer. In the described embodiments, an electronic device incorporating a sensor may employ a sensor tracking module, also referred to as a sensor processing unit (SPU), which includes at least one sensor in addition to the electronic circuit. Sensors such as gyroscopes, magnetometers, accelerometers, microphones, pressure sensors, proximity sensors, or ambient light sensors are contemplated in addition to other sensors known in the art. Some embodiments include accelerometers and gyroscopes, each of which provides measurements along three axes orthogonal to each other. Such devices are generally referred to as 6-axis devices. Other embodiments include accelerometers, gyroscopes, and magnetometers, each of which provides measurements along three axes that are orthogonal to each other. Such devices are generally referred to as 9-axis devices. Other embodiments may not include all sensors, or may provide measurements along one or more axes. The sensors may be formed on a first substrate. Other embodiments may include solid-state sensors or any other type of sensor. The electronic circuit in the SPU receives measurement outputs from one or more sensors. In some embodiments, the electronic circuit processes the sensor data. The electronic circuit may be implemented on a second silicon substrate. In some embodiments, the first substrate may be in a single semiconductor chip: vertically stacked, attached, and electrically connected to the second substrate, while in other embodiments, the first substrate may be in a single semiconductor package: laterally arranged and electrically connected to the second substrate.

[0066] In one embodiment, the first substrate is attached to the second substrate by wafer bonding as described in commonly owned U.S. Patent No. 7,104,129, which is incorporated herein by reference in its entirety, to simultaneously provide electrical connections and hermetically seal the MEMS device. This manufacturing technique advantageously enables a technology that allows high performance, multi-axis, inertial sensors to be designed and manufactured in a very compact and economical package. Integration at the wafer level minimizes parasitic capacitance, thereby allowing for an improved signal-to-noise ratio relative to discrete solutions. This integration at the wafer level also enables the incorporation of a rich feature set that minimizes the need for external amplification.

[0067] In the described embodiments, raw data refers to measurement output from a sensor that has not been processed. Motion data may refer to processed and / or raw data. Processing may include applying a sensor fusion algorithm or applying any other algorithm. In the case of a sensor fusion algorithm, data from multiple sensors may be combined to provide, for example, an orientation of a device. In the described embodiments, the SPU may include a processor, memory, control logic, and sensors in a structure.

[0068] The reference system of a portable device such as transmitter 102 can be a body coordinate system with three orthogonal axes. Switching from the body coordinate system to the world coordinate system or any other suitable reference system (such as, for example, a reference system associated with one or more of the receivers 104) can be performed by applying appropriate rotation to the data, or vice versa. Similarly, the axis of the world coordinate system may be fixed to the earth, such as by aligning the Z axis of the world coordinate system with the gravity vector generated from the earth's gravity field, pointing from the earth's surface to the sky. Although the mathematics and descriptions provided in the present disclosure are in the context of these coordinate systems, those skilled in the art will recognize that other definitions and reference systems can be used to perform similar operations. All teachings can be redone with different definitions. Therefore, the orientation of the portable device can be expressed as a rotation operation that translates the body coordinate system to the world coordinate system, such as a rotation operation that aligns the Z axis of the body coordinate system with the gravity vector. In some embodiments, the rotation operation can be expressed in the form of a unit quaternion. As used herein, for convenience, the terms "quaternion" and "unit quaternion" can be used interchangeably. Thus, a quaternion can be a four-element vector that describes a transition from one rotational orientation to another, and can be used to represent the orientation of a portable device. A unit quaternion has one scalar term and three imaginary terms. In the present disclosure, quaternions are represented first by the scalar term, followed by the imaginary term, but appropriate modifications can be made to the formulas, equations, and operations to accommodate different definitions of quaternions.

[0069] Although the present invention has been described in terms of the illustrated embodiments, a person of ordinary skill in the art will readily recognize that the embodiments may vary, and that those variations will be within the spirit and scope of the present invention. For example, the technology of the present disclosure has been explained in the context of an HMD and a controller, but the technology may be applied in any other suitable context. A person of ordinary skill in the art may readily design other systems consistent with the disclosed embodiments, which are intended to fall within the scope of the present disclosure.

Claims

1. A positioning system, comprising: A transmitter, the transmitter comprising: an acoustic signal transmitter configured to transmit a modulated acoustic signal; a magnetic synchronization signal transmitter configured to transmit a modulated magnetic synchronization signal; and at least one inertial sensor assembly having at least one sensor configured to receive as input the modulated magnetic synchronization signal and configured to transmit an inertial signal; and A receiver, the receiver comprising: an acoustic signal receiver configured to receive the transmitted modulated acoustic signal; a magnetic synchronization signal receiver configured to receive the transmitted modulated magnetic synchronization signal; an inertial signal receiver configured to receive the transmitted inertial signal; and At least one processor is configured to receive a modulated acoustic signal from an acoustic signal receiver, a modulated magnetic synchronization signal from a magnetic synchronization signal receiver, and an inertial signal from an inertial signal receiver in the same time domain, and is configured to determine a position of a transmitter based on the received modulated magnetic synchronization signal, a determined time delay of the received modulated acoustic signal, and the received inertial signal, and by fusing the acoustic position determination and the inertial position determination, wherein the acoustic position determination and the inertial position determination are synchronized based on the modulated magnetic synchronization signal.

2. The positioning system according to claim 1, wherein: The at least one processor is configured to: making said acoustic position determination of the transmitter based on a determined time delay of the received modulated magnetic synchronization signal and the received modulated acoustic signal; and Based on the received inertial signal, the inertial position determination of the transmitter is made.

3. The positioning system according to claim 1 or 2, wherein: The inertial sensor assembly is configured to receive as input an indication of the start of the modulated magnetic synchronization signal and determine timing data relative to the inertial signal.

4. The positioning system according to claim 3, wherein: The timing data includes a time delay between an indication of the start of a received modulated magnetic synchronization signal and an acquired inertial sensor sample.

5. The positioning system according to claim 4, wherein: The inertial sensor assembly is further configured to determine a timestamp of an indication of the start of the received modulated magnetic synchronization signal based on the time delay.

6. The positioning system according to claim 5, wherein: The inertial sensor assembly receives the modulated magnetic synchronization signal on a dedicated input.

7. The positioning system according to claim 1, wherein: The inertial sensor assembly includes at least one of an accelerometer and a gyroscope.

8. The positioning system according to claim 7, wherein: The inertial sensor assembly also includes a magnetometer.

9. The positioning system according to claim 1, wherein: The receiver includes at least one of a virtual reality display and an augmented reality display.

10. The positioning system according to claim 9, wherein: The transmitter includes a handheld controller for the receiver.

11. The positioning system according to claim 1, further comprising: an additional acoustic signal transmitter capable of undergoing independent movement and configured to transmit a modulated acoustic signal; a magnetic synchronization signal transmitter configured to transmit a modulated magnetic synchronization signal; and At least one inertial sensor assembly having at least one sensor synchronized with the modulated magnetic synchronization signal and configured to transmit an inertial signal.

12. The positioning system according to claim 2, wherein: The inertial signal is sent using radio frequency communication.

13. A portable transmitter comprising: an acoustic signal transmitter configured to transmit a modulated acoustic signal; a magnetic synchronization signal transmitter configured to transmit a modulated magnetic synchronization signal; and At least one inertial sensor assembly has at least one sensor configured to receive the modulated magnetic synchronization signal as input and configured to transmit an inertial signal.

14. The portable transmitter according to claim 13, wherein: The inertial sensor assembly is configured to receive as input an indication of the start of the modulated magnetic synchronization signal and determine timing data relative to the inertial signal.

15. The portable transmitter according to claim 14, wherein: The timing data includes a time delay between an indication of the start of a received modulated magnetic synchronization signal and an acquired inertial sensor sample.

16. The portable transmitter according to claim 15, wherein: The inertial sensor assembly is further configured to determine a timestamp of an indication of the start of the received modulated magnetic synchronization signal based on the time delay.

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