PATENT DOCUMENT

Publication Number: US-10557724-B1
Application Number: US-201816145941-A
Country: US
Kind Code: B1

Title: Angle detection of a rotating system using a single magnet and multiple hall sensors

Abstract:
An angular detection system including a magnet and sensors is disclosed. The magnet can be located on a rotating component and the sensors can be located on a stationary component, or vice versa. The magnet can generate a plurality of magnetic flux lines. The plurality of sensors can be located and spatially separated along the motion path of the magnet for detecting the magnetic flux densities. The strength of the magnetic flux lines sensed by a given sensor can be used to determine the location of the magnet along its motion path. The plurality of sensors can generate one or more signals indicative of the strength of the sensed magnetic field lines. Based on the strength of the magnetic flux lines, the location of the magnet, or both, the system can determine the angle of rotation of the device by using a polynomial function or a look-up table.

Claims:
The invention claimed is: 
     
       1. An angular detection system comprising:
 a stationary component; 
 a rotating component, wherein the rotating component is capable of rotating relative to the stationary component; 
 a magnet located on one of the stationary component or the rotating component, where the magnet generates a plurality of magnetic flux lines; 
 a plurality of sensors located on the other of the stationary component and the rotating component, where the plurality of sensors is placed along a motion path of the magnet, 
 wherein the plurality of sensors senses the plurality of magnetic flux lines and generates one or more signals indicative of the sensed plurality of magnetic flux lines; and 
 logic that determines an angle of rotation of the angular detection system based on the one or more signals. 
 
     
     
       2. The angular detection system of  claim 1 , wherein the magnet is a permanent magnet. 
     
     
       3. The angular detection system of  claim 1 , further comprising:
 a screw for attaching the magnet to the rotating component, wherein the screw rotates as the rotating component rotates. 
 
     
     
       4. The angular detection system of  claim 1 , wherein the rotating component is a roll-bar included in a headset. 
     
     
       5. The angular detection system of  claim 1 , wherein the stationary component is a portion of a frame included in a headset. 
     
     
       6. The angular detection system of  claim 1 , wherein the plurality of sensors includes one or more of Hall effect sensors, anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) sensors, and tunnel magnetoresistance (TMR) sensors. 
     
     
       7. The angular detection system of  claim 1 , wherein the plurality of sensors include at least two different types of sensors. 
     
     
       8. The angular detection system of  claim 1 , wherein separation distances between pairs of adjacent sensors of the plurality of sensors are the same. 
     
     
       9. The angular detection system of  claim 1 , wherein a first sensor of the plurality of sensors is located at a reference point along the motion path, a second sensor of the plurality of sensors is located 10 degrees counter-clockwise from the reference point, and a third sensor of the plurality of sensors is located 20 degrees counter-clockwise from the reference point. 
     
     
       10. The angular detection system of  claim 1 , further comprising:
 a flex board located on the stationary component, the flex board including:
 the plurality of sensors, and 
 one or more routing traces that connect the plurality of sensors to a power supply. 
 
 
     
     
       11. The angular detection system of  claim 1 , wherein the angular detection system is capable of sensing an angle of rotation of the system of 20 degrees. 
     
     
       12. The angular detection system of  claim 1 , wherein each of the plurality of sensors are associated with a unique pre-assigned range. 
     
     
       13. A method for detecting an angle of rotation of a head-worn device, the method comprising:
 generating a plurality of magnetic flux lines from a magnet; 
 rotating the magnet to a location along a motion path; 
 sensing the plurality of magnetic flux lines using a plurality of sensors; 
 for each of the plurality of sensors, generating a signal indicative of a strength of the sensed plurality of magnetic flux lines; and 
 determining the angle of rotation based on the signals from the plurality of sensors. 
 
     
     
       14. The method of  claim 13 , further comprising:
 determining the location of the magnet by determining for at least one of the plurality of sensors that the at least one of the plurality of sensors is not located in a path of the plurality of magnetic flux lines when the respective signal is equal to zero. 
 
     
     
       15. The method of  claim 13 , wherein the determination of the angle of rotation includes:
 comparing intensities of the signals of the plurality of sensors, 
 associating the location of the magnet to one of the plurality of sensors based on the comparison, and 
 determining the angle of rotation based on the association. 
 
     
     
       16. The method of  claim 13 , wherein the determination of the angle of rotation includes:
 determining whether an intensity of at least one signal generated by at least one of the plurality of sensors is greater than or equal to a threshold value; and 
 in accordance with the determination that the intensity is greater than or equal to the threshold value, determining that the angle of rotation is within a range associated with the threshold value. 
 
     
     
       17. The method of  claim 13 , further comprising:
 combining the signals generated by the plurality of sensors using a transfer function, wherein the determination of the angle of rotation is based on the combined signals. 
 
     
     
       18. A headset comprising:
 a frame; 
 a roll-bar; 
 an angular detection system including:
 a magnet located on one of the frame or roll-bar, where the magnet generates a plurality of magnetic flux lines; 
 a plurality of sensors located on the other of the frame or the roll-bar, where the plurality of sensors is placed along a motion path of the magnet, 
 wherein the plurality of sensors senses the plurality of magnetic flux lines and generates one or more signals indicative of the sensed plurality of magnetic flux lines; and 
 
 logic that determines an angle of rotation of the angular detection system based on the one or more signals. 
 
     
     
       19. The headset of  claim 18 , wherein the headset is included in a virtual reality system. 
     
     
       20. The headset of  claim 18 , wherein the headset is headphones that exclude a display.

Description:
FIELD OF THE DISCLOSURE 
     This disclosure relates to a system for detecting the angle of rotation using magnetic sensing. 
     BACKGROUND OF THE DISCLOSURE 
     Virtual reality (VR) technology can be used for many applications such as military training, educational learning, and video games. VR technology can use one or more electronic devices to simulate a virtual environment and the user&#39;s physical presence in that virtual environment. One type of VR technology is augmented reality (AR) technology, where the user&#39;s real environment can be supplemented with computer-generated objects or content. Another type of VR technology is mixed reality (MR) technology, where the user&#39;s real environment and the virtual environment can be blended together. 
     VR/AR/MR technology can be simulated using one or more electronic devices. One electronic device can be a VR headset, where the user can use the VR headset to see the simulated virtual environment. As the user moves his or her head to look around, a display included in the headset can update to reflect the user&#39;s head movement. The VR headset can be worn on the user&#39;s head while the user is interacting with the VR system and can be removed from the user&#39;s head at other instances. In some examples, it may be beneficial for the VR headset to be able to detect when a head-worn device (e.g., headset, eyeglasses, headphones, etc.) is being removed from the user&#39;s head, is being placed on the user&#39;s head, or both. 
     SUMMARY OF THE DISCLOSURE 
     This disclosure relates to an angular detection system included in a device such as headphones or a headset. The angular detection system can include a magnet and a plurality of sensors, one of which can be located on a rotating component and the other can be located on a stationary component. The magnet can generate a plurality of magnetic flux lines. The plurality of sensors can be located and spatially separated along the motion path of the magnet for detecting the magnetic flux densities. The strength of the magnetic flux lines sensed by a given sensor can be used to determine the location of the magnet along its motion path. The plurality of sensors can generate one or more signals, such as voltage signals, which can be indicative of the strength of the sensed magnetic field lines. Based on the strength of the magnetic flux lines, the location of the magnet, or both, the system can determine the angle of rotation of the device. The relationship between the voltage signal(s) and the angle of rotation may be determined by a polynomial function or a look-up table, which may be stored in memory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary headphone or headset system according to examples of the disclosure. 
         FIG. 2A  illustrates a perspective view of an exemplary angular detection system according to examples of the disclosure. 
         FIG. 2B  illustrates a block diagram of an exemplary angular detection system according to examples of the disclosure. 
         FIG. 3A  illustrates an exemplary flow of operation of an angular detection system according to examples of the disclosure. 
         FIG. 3B  illustrates an exemplary simplified block diagram according to examples of the disclosure. 
         FIG. 4  illustrates a schematic diagram of exemplary circuitry for detecting the angle of rotation according to examples of the disclosure. 
         FIG. 5A  illustrates a process flow for an exemplary scan management function according to examples of the disclosure. 
         FIG. 5B  illustrates a corresponding timing diagram according to examples of the disclosure. 
         FIG. 6  illustrates exemplary output signals from the sensors as a function of angle of rotation according to examples in the disclosure. 
         FIG. 7  illustrates an exemplary combined output voltage according to examples of the disclosure. 
         FIG. 8  illustrates a block diagram of the hardware and software components included in an exemplary headset according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     Various techniques and process flow steps will be described in detail with reference to examples as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or referenced herein. 
     Further, although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, any sequence or order of steps that can be described in the disclosure does not, in and of itself, indicate a requirement that the steps be performed in that order. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one-step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     Virtual reality (VR) technology can be used for many applications such as military training, educational learning, and video games. VR technology can use one or more electronic devices to simulate a virtual environment and the user&#39;s physical presence in that virtual environment. One type of VR technology is augmented reality (AR) technology, where the user&#39;s real environment can be supplemented with computer-generated objects or content. Another type of VR technology is mixed reality (MR) technology, where the user&#39;s real environment and the virtual environment can be blended together. 
     VR/AR/MR technology can be simulated using one or more electronic devices. One electronic device can be a VR headset, where the user can use the VR headset to see the simulated virtual environment. As the user moves his or her head to look around, a display included in the headset can update to reflect the user&#39;s head movement. The VR headset can be worn on the user&#39;s head while the user is interacting with the VR system and can be removed from the user&#39;s head at other instances. In some examples, it may beneficial for the VR headset to be able to detect when a head-worn device (e.g., headset, eyeglasses, headphones, etc.) is being removed from the user&#39;s head, is being placed on the user&#39;s head, or both. 
     This disclosure relates to an angular detection system included in a device such as headphones or a headset. The angular detection system can include a magnet and a plurality of sensors, one of which can be located on a rotating component and the other can be located on a stationary component. The magnet can generate a plurality of magnetic flux lines. The plurality of sensors can be located and spatially separated along the motion path of the magnet for detecting the magnetic flux lines. The strength of the magnetic flux lines sensed by a given sensor can be used to determine the location of the magnet along its motion path. The plurality of sensors can generate one or more signals, such as voltage signals, which can be indicative of the strength of the sensed magnetic field lines. Based on the strength of the magnetic flux lines, the location of the magnet, or both, the system can determine the angle of rotation of the device. The relationship between the voltage signal(s) and the angle of rotation may be determined by a polynomial function or a look-up table, which may be stored in memory. 
     Representative applications of methods and apparatus according to the present disclosure are described in this section. These examples are being provided solely to add context and aid in the understanding of the described examples. It will thus be apparent to one skilled in the art that the described examples may be practiced without some or all of the specific details. In other instances, well-known process steps have been described in detail in order to avoid unnecessarily obscuring the described examples. Other applications are possible, such that the following examples should not be taken as limiting. 
       FIG. 1  illustrates an exemplary headphone or headset system according to examples of the disclosure. The system  100  includes a headset  102 . The headset  102  can be configured to receive audio data and convert the audio data into sound. The headset  102  can be a variety of shapes and sizes, can be made from a variety of materials, and can include a variety of features. In some examples, the headset  102  can include, for example, a head-fitting band  101 , such as one used for listening to the audio associated with music, a video, a gaming system, a VR system, or the like. The headset  102  can include earpieces  104 , and the band  101  can connect the earpieces  104 . The earpieces  104  can be an interface between the user&#39;s ear(s) and the headset  102 . In some examples, the earpieces  104  can include one or several features configured to generate sound such as, e.g., one or several speakers. Examples of the disclosure can include a headphone that excludes a display. 
     In some examples, the system  100  can include a cable  106  that can, for example, include features that allow for simultaneously providing power, such as electricity, and audio data to the headset  102 . The cable  106  can be a variety of shapes and sizes, a variety of cable types, and can be made from a variety of materials. The cable  106  can connect to the headset  102  via a connector  108 . The connector  108  can be a variety of shapes and sizes and can be a variety of different connector types. In some examples, the connector  108  can receive power and/or audio data that can be used to control sound generated by the headset  102 . In some examples, the connector  108  can include features for receiving power to charge the headset  102  and features for receiving audio data to control sound generated by the headset  102 . In some examples, the connector  108  can be, e.g., a USB connector, a SATA connector, or any other desired connector. 
     The system  100  can also include one or more components to which the headset  102  communicates with. The one or more components can be, for example, a user device  112 . The user device  112  can be a source of audio data, video data, or the like, where the data can control the operation of the headset  102  and/or the source of power for the headset  102 . In some examples, the user device  112  can be an electronic device such as a portable electronic device. Exemplary electronic devices include, but are not limited to, a computer, a tablet, a cell phone, a television, a smart phone, a PDA, a radio, a gaming console, or any other electronic device usable to consume media. 
     In some examples, the user device  112  can connect to cable  106  via a connector  110 . The connector  110  can be a variety of shapes and sizes and can be a variety of different connector types. In some examples, the connector  110  can transmit power and/or audio data that can be used to control sound generated by the headset  102 . In some examples, the connector  110  can include features for transmitting power to power the headset  102  and/or for transmitting audio data to control sound generated by headset  102 . In some examples, the connector  110  can be, e.g., a USB connector, a SATA connector, or any other desired connector. In some examples, the connector  110  can include a first portion that is located on the user device  112  such as, e.g., a connector receptacle or a connector insert, and a mating second portion that is located on the cable  106 . 
     In some examples, the headset  102  may be configured for wireless communication of audio data, video data, or both. The headset  102  may include a transceiver, such as an antenna (not shown). The antenna can be located such that all or portions of the antenna are external to the headset  102 . The antenna can be configured to receive information, such as, video data, from the user device  112 . The user device  112  may also include a wireless transmitter (not shown), which can also include an antenna. The wireless communication between the headset  102  and the user device  112  can be performed according to any type of communication protocol or standard including, but not limited to, Bluetooth, WiFi (WLAN), NFC, or the like. 
     In some examples, the headset  102  can also include an angular detection system  120 . The angular detection system  120  can be configured to detect an angle of rotation of a component, such as a cup, located in the headset  102 . The angular detection system  120  can be configured to detect when the headset is being removed from the user&#39;s head, is being placed on the user&#39;s head, or both. That is, the angular detection system  120  can be configured to detect different states of the headset  102 . The angular detection system  120  can be configured to generate one or more signals indicative of its state. The one or more signals can be transmitted to a controller (not shown). The controller can receive the one or more signals and can perform one or more actions in response to the signals. Exemplary actions can include, but are not limited to, turning one or more components (e.g., the entire headset  102 , the entire system  100 , etc.) on or off, determining the size of the user&#39;s head, etc. In some examples, the signal(s) can be transmitted via connector  108  and connector  110  to the user device  112 . In other instances, the signal(s) can be transmitted via wireless communication, and the headset may not attach to the user device  112  via the cable  106 , the connector  108 , or the connector  110 . Yet in other instances, the controller can be located in the headset  102 , and can control one or more components for turning the headset on or off. 
     Overview of the Angular Detection System 
       FIG. 2A  illustrates a perspective view, and  FIG. 2B  illustrates a block diagram of an exemplary angular detection system according to examples of the disclosure. The angular detection system  220  can include one or more components and/or one or more functions that are correspondingly similar to the angular detection system  120 . The angular detection system  220  can include a magnet  230  and a flex board  240 . The magnet  230  can be located (e.g., attached) on a rotating component such as a roll-bar  232 , and the flex board  240  can be located (e.g., attached) on a stationary component such as a frame  242 . In some instances, the frame  242  can be a portion of an entire frame of the headset. The stationary component can be a first component that does not move relative to a second component that may rotate. In some examples, the flex board  240  can be located on the roll-bar  232 , and the magnet  230  can be located on the frame  242  (not shown). 
     The magnet  230  can be a permanent magnet that stores the magnetic energy at the time of manufacturing and is retained for a long (e.g., almost infinite) amount of time, for example. The magnet  230  can be attached to the roll-bar  232  and can have a center of rotation  234 . The center of rotation  234  can be a fixed point where the magnet  230  moves along a certain motion path  236 . In some examples, a screw (not explicitly labeled) can be located at the same location as the center of rotation  234 . The screw can attach the roll-bar  232  to the frame  242  and can rotate as the roll-bar  232  rotates. As the screw rotates, the magnet  230  can move along the motion path  236 . In some instances, the motion path  236  can be an arc. The movement of the roll-bar  232  may be limited to rotating along the motion path  236  of the magnet  230 , in some examples. 
     The flex board  240  can include one or more components such as one or more sensors  244 , circuitry  246 , routing traces  245 , and a connector  249 . The one or more sensors  244  can be any type of magnetic-field sensor. Exemplary sensors include, but are not limited to, Hall effect sensors, anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) sensors, and tunnel magnetoresistance (TMR) sensors. The type of sensor  244  included in the flex board  240  can be based on one or more factors such as the power consumption of the sensors, signal-to-noise ratio, cost, size (e.g., footprint), and the like. In some examples, the sensors  244  can include at least two sensors of different types. 
     The sensors  244  can be located on the flex board  240  and can be placed along the motion path  236  of the magnet  230 . In some examples, the sensors  244  may be placed within the sensing range of the motion path  236 . The sensors  244  may be spaced apart with any separation distance between adjacent sensors. The separation distance(s) may be based on one or more factors such as the targeted dynamic range of angular detection, the number of sensors, the targeted sensing sensitivity for a given angle of rotation, and the like. The separation distance can refer to the arc length between the centers of adjacent sensors. In some instances, the system may include at least three sensors  244  with each pair of adjacent sensors having the same separation distance as other pairs. In other instances, the separation distances may differ. As one example, the system can include three sensors, where the first sensor can be placed at a reference point along the motion path (e.g., zero degrees), the second sensor can be placed at 10 degrees counter-clockwise from the reference point, and the third sensor can be placed at 20 degrees counter-clockwise from the reference point. 
     One or more routing traces  245  can be used to connect the sensors  244  to a power supply (not shown). The power supply can provide a current to the sensors  244  (discussed below). The routing traces  245  can also be used to route the signals generated by the sensors  244  (discussed below) to a controller, which can analyze the signals. The controller can be included in the circuitry  246  or can be located on a separate board, such as printed circuit board (PCB)  248 . The flex board  240  can also include a connector  249  for connecting to the PCB  248 . 
     Although the figure illustrates the system including a single magnet and three sensors, examples of the disclosure can include any number of magnets and any number of sensors. Additionally or alternatively, the location and orientation of the magnet and the sensors may differ from the exact configuration as shown in the figures. 
     Exemplary Operation of the Angular Detection System 
       FIG. 3A  illustrates an exemplary flow of operation of the angular detection system, and  FIG. 3B  illustrates an exemplary simplified block diagram according to examples of the disclosure. A magnet  330  can be located at a certain location relative to the band (e.g., band  101  illustrated in  FIG. 1 ) of the headset (e.g., headset  102  illustrated in  FIG. 1 ) (step  352  of process  350 ). The magnet  330  can generate magnetic flux lines  327  that travel perpendicular to its surfaces  329 . A given magnetic flux line  327  can travel a certain distance from the surfaces of the magnet  330 . The strength of the magnetic field can be based on the spacing between the magnetic flux lines  327 , so it may be greater near the top and bottom surfaces  329  of the magnet  330  than along the side surfaces  335 . 
     The magnet  330  can be attached to a roll-bar (e.g., roll-bar  232  illustrated in  FIG. 2A ) and can move along a motion path (e.g., motion path  236  illustrated in  FIG. 2B ) by an amount related to the amount of rotation of the roll-bar (step  354  of process  350 ). The location of the magnet  330  along the motion path can be determined by the one or more signals generated by the one or more sensors  344 , as discussed below. For example, the roll-bar may rotate in response to the user putting the headset on his or her head, which may cause the magnet  330  to change location. 
     The sensors  344  can be configured to sense the magnetic flux lines. The sensors  334  can be connected to a power supply  347 . The power supply  347  can provide a current (e.g., a constant current) to the sensors  344 , where the current can cause the sensors  344  to sense the magnetic flux lines (step  356  of process  350 ). The sensors  344  can generate one or more signals indicative of the strength of the magnetic flux lines it senses (step  358  of process  350 ). When a given sensor  344  is not located in the path of the magnetic flux lines, the sensor  344  may generate a signal (e.g., equal to zero or the noise level) that indicates that no magnetic flux lines are sensed. For example, sensor  334 A may generate a non-zero signal due to being located in the path of the magnetic field lines, whereas sensor  334 B may not. 
     A controller may receive the one or more signals (step  360  of process  350 ). The controller may determine from the signals where the magnet  330  is along its motion path based on the magnetic field strength (step  362  of process  350 ), as discussed in detail below. In some instances, the controller can determine the angle of rotation based on the signals, where the location along the motion path can be related to the angular motion, and the magnetic field strength information can be included in the signals. 
     The magnet  330  and the sensors  344  can include one or more components and/or one or more functions that are correspondingly similar to the magnet  240  and sensors  244 , respectively. 
     Detection of the Angle of Rotation 
       FIG. 4  illustrates a schematic diagram of exemplary circuitry for detecting the angle of rotation according to examples of the disclosure. Circuitry  446  can include a low-dropout voltage regulator (LDO)  446 -A, a plurality of sensors  444 , a multiplexer (MUX)  446 -B, a programmable gain amplifier (PGA)  446 -C, an analog-to-digital converter (ADC)  446 -D, a digital signal processor (DSP)  446 -E, and memory  446 -F. Circuitry  446  and sensors  444  can include one or more components and/or one or more functions that are correspondingly similar to circuitry  246 , sensors  244 , and sensors  344 , respectively. 
     The LDO  446 -A can be a power supply configured to apply a voltage to the inputs of the plurality of sensors  444 . The sensors  444  can sense the magnetic flux lines generated by the magnet and can generate voltage signals. The MUX  446 -B can be configured to route the signals generated by the sensors  444  to the input of the PGA  446 -C. The PGA  446 -C can apply a gain factor to the signals, as discussed below. The output from PGA  446 -C can be input into the ADC  446 -D, which can convert the signals from the sensors  444  into digital form. The digital signals from the ADC  446 -D can be input into the DSP  446 -E. 
     The DSP  446 -E can adjust the digital signals to account for system offset/gain mismatch. The DSP  446 -E can also convert the digital signal, which may be a voltage signal, to a corresponding angle of rotation. The relationship between the voltage signal and the angle of rotation may be determined by a polynomial function or a look-up table, which may be stored in memory  446 -F. 
     Scan Management 
     The system can include a scan management function.  FIG. 5A  illustrates a process flow for an exemplary scan management function, and  FIG. 5B  illustrates a corresponding timing diagram, according to examples of the disclosure. The scan management function can be implemented using one or more components included in circuitry. The circuitry can be included in the flex board (e.g., flex board  240  illustrated in  FIG. 2B ) and/or another board, such as PCB  248  illustrated in  FIG. 2B . For example, an external microcontroller or an ADC chip can implement the scan management function. 
     The scan management function can include a plurality of scans. A scan can last for a certain amount of time  590 . In some instances, during a scan, a LDO (e.g., LDO  446 -A illustrated in  FIG. 4 ) can be configured to apply a voltage, such as a fixed voltage, to a plurality of sensors (e.g., sensors  444  illustrated in  FIG. 4 ) (step  552  of process  550 ). The beginning of a scan can be indicated by SCAN_EN at time  580  as shown in  FIG. 5B . The system can wait a pre-determined amount of time for the output signals from the sensors to settle (step  554  of process  550 ). A multiplexer (e.g., MUX  446 -B illustrated in  FIG. 4 ) can then connect the output signals from a first sensor to a PGA (e.g., PGA  446 -C illustrated in  FIG. 4 ) (step  556  of process  550 ). The connection from the first sensor can be indicated by the MUX_CONTROL signal being equal to MUX 1 _EN as shown in  FIG. 5B . The system can select a calibrated gain factor from memory (e.g., memory  446 -F illustrated in  FIG. 4 ) (step  558  of process  550 ). The system can wait a pre-determined amount of time for the output signal from the PGA to settle (step  560  of process  550 ) and can send the output signal to an ADC (e.g., ADC  446 -D illustrated in  FIG. 4 ) once the wait time has elapsed (step  562  of process  550 ; time  582  in  FIG. 5B ). The ADC can be enabled as indicated by the signal ADC_CONTROL indicated in  FIG. 5B . The ADC can convert the analog signal that it has received to a digital signal (step  564  of process  550 ). Optionally, the system may average the signal with one or more other signals (step  566  of process  550 ). Averaging the signals may reduce the impact of noise, such as quantization noise or high frequency noise. 
     In some examples, an offset voltage can be subtracted from the digital signal (step  568  of process  550 ). The offset voltage can be determined using an offset calibration procedure, which can determine the offset voltage introduced by each sensor. In some instances, the offset voltage for a given sensor may differ from that of other sensors. Exemplary offset voltages can include, but are not limited to, ±5 mV and +10 mV. In some examples, one or more offset voltages can be stored in memory (e.g., memory  446 -F illustrated in  FIG. 4 ). 
     The system may apply a gain correction value to convert the output signal from the sensors from units representative of magnetic flux to units representative of an electrical signal (step  570  of process  550 ). In some examples, one or more gain correction values can be stored in memory (e.g., memory  446 -F illustrated in  FIG. 4 ). 
     The system can then connect the output signals from the next sensor to the PGA (as indicated by signals MUX 2 _EN, MUX 3 _EN, etc. in  FIG. 5B ), as steps  556  to  570  can be repeated until all the sensor outputs are converted into digital signals (step  572  and step  574  of process  550 ). For example, a second sensor can be connected at time  584 , and a third sensor can be connected at time  586 , as shown in  FIG. 5B . Once some (e.g., all) of the sensor outputs have been converted, the system can determine the angle of rotation (step  576  of process  550 ). 
       FIG. 6  illustrates exemplary signals output from the sensors as a function of angle of rotation according to examples in the disclosure. As the roll-bar changes its angle of rotation, the intensity of the magnetic flux measured by a given sensor changes. For example, as shown in the figure, when the roll-bar is at degree 611 (e.g., zero degrees), the first sensor senses the maximum amount of magnetic flux (shown by signal  621 ), the second sensor senses a small amount (e.g., less than 20 mT) of magnetic flux (shown by signal  623 ), and the third sensor does not sense any magnetic flux (shown by signal  625 ). As the roll-bar changes its angle of rotation to degree 613 (e.g., five degrees), the magnetic flux sensed by the first sensor decreases. At the same time, the magnetic flux sensed by the second sensor increases, and there is no effect on the third sensor. 
     In some instances, the intensity of at least two (e.g., each) of the sensors may vary, and the magnet may be located closest to the sensor with the highest intensity relative to the other sensors. A given sensor can be associated with one or more unique angle of rotation values. The system can compare the intensity of the sensors and determine which sensor the magnet is closest to based on the comparison. Based on the sensor that the magnet is closest to, the system can determine the angle of rotation of the device. 
     Then, as the roll-bar changes its angle of rotation to degree 615 (e.g., 10 degrees), the magnetic flux sensed by the first sensor decreases further to zero, indicating that magnetic field lines from the magnet attached to the roll-bar may be located outside of the sensing range of the first sensor. The magnetic flux sensed by the second sensor increases and reaches a maximum, which may indicate that the center of the second sensor and the magnet may be aligned. Additionally, the third sensor begins to sense the magnetic field lines. 
     Changing from the angle of rotation of the roll-bar from degree 615 to degree 617, the magnetic flux sensed by the second sensor decreases, the magnetic flux sensed by the third sensor increases, and the first sensor is unaffected. When the roll-bar reaches degree 619 (e.g., 20 degrees), only the third sensor senses the magnetic field lines. 
     By using multiple sensors, the dynamic range of the system can be increased. For example, a system having a single sensor can have a sensing range of 0-5 degrees, while a system having three sensors can have a sensing range of 0-20 degrees. In some examples, the signals from the different sensors can be readout individually. The magnitude of one or some (e.g., all) of the signals can be used to determine the angle of rotation of the roll-bar. Additionally or alternatively, the relative relationship between the signals can be used to determine the direction of rotation and/or the angle of rotation. 
     In some examples, a given sensor can be used (e.g., dedicated) for angular detection within a pre-assigned range. In some instances, the pre-assigned ranges for the sensors may not overlap with one another. For example, the first sensor can be used to detect a rotation of up to four degrees, the second sensor can be used to detect a rotation between four degrees to 14 degrees, and the third sensor can be used to detect a rotation between 14 degrees to 24 degrees. 
     In some instances, the system can be configured to determine the angle of rotation based on a threshold magnetic flux value. For example, the threshold magnetic flux value can be equal to threshold  631 , which can be pre-determined. In some examples, the threshold  631  can be based on one or more factors such as electronic noise. 
     If the system determines that the signal  625  is greater than or equal to the threshold  631 , then the system can determine that the angle of rotation falls within a certain range (e.g., is greater than or equal to 14 degrees) associated with the threshold. Additionally or alternatively, the system can determine the range of angle of rotation based on one or more relative differences between the signals. For example, if signal  621  and signal  623  are simultaneously lower than signal  623 , the system can determine that the angle of rotation is greater than or equal to 14 degrees. 
     In some examples, the system can determine the angle of rotation based on a combined transfer function.  FIG. 7  illustrates an exemplary combined output voltage according to examples of the disclosure. One or more gain values can be applied to the outputs from the sensors. The applied gain values can be such that the combined transfer curve has a monotonic response of magnetic flux over angle. For example, the signal  721  can be multiplied by one, the signal  723  can be multiplied by two, and the signal  725  can be multiplied by three. The combination of the signal  721 , signal  723 , and signal  725  can result in the signal  733 . As shown in the figure, the monotonic response of signal  733  can be from degree 711 to degree 719. 
     In some examples, the applied gain values can be such that the combined transfer curve also has a certain slope. The pre-determined slope can depend on one or more factors such as the accuracy of the measurement, the electrical noise sources, etc. Exemplary electrical noise sources include, but are not limited to, quantization noise of the ADC, power supply noise observed by the sensor, and the thermal drift of the sensor. 
     Overview of the Components in an Exemplary Headset 
       FIG. 8  illustrates a block diagram of the hardware and software components included in an exemplary headset according to examples of the disclosure. Headset  802  can optionally include a control circuit  846 , which can include a processor, for example. The processor can provide instructions to and can receive information from the other components of the headset  802 . The processor can act according to stored instructions, where stored instructions can be located in memory, associated with the processor, and/or in other components of the headset  802 . The processor can make decisions in accordance with the stored instructions. 
     In some examples, the stored instructions directing the operation of the processor may be implemented by hardware, software, scripting languages, firmware, middleware, microcode, hardware description languages, and/or a combination thereof. When implemented in software, firmware, middleware, scripting language, and/or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as a storage medium. A code segment or machine-executable instruction may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a script, a class, or any combination of instructions, data structures, and/or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc. 
     The headset  802  can optionally include a memory  804 . The memory  804  may represent one or more memories for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, optical storage mediums, flash memory device, and/or other machine readable mediums for storing information. In some examples, the memory  804  may be implemented within the processor or external to the processor. In some examples, the memory  804  can be any type of long term, short term, volatile, nonvolatile, or other storage medium and is not to be limited to any particular type of memory or number of memories, or type of media upon which memory is stored. In some examples, memory  804  can include one or both volatile and nonvolatile memory, for example. In one specific example, the memory  804  can include a volatile portion such as RAM memory, and a nonvolatile portion such as flash memory. 
     The headset  802  can include a buffer, also referred to herein as a data buffer. The buffer can be configured to temporarily store data that is being received by the headset  802 . In some examples, the buffer can be implemented in the memory  804 , can be implemented in software stored in memory, or can be implemented in the control circuit  846 . In some examples, the buffer can receive data, including audio data and/or video data from a wired communicator  808  and/or wireless communicator  810 , and can provide this data to the control circuit  846 . 
     The headset  802  can optionally include energy storage  806 . The energy storage  806  can store energy such as, for example, electrical energy that can power the headset  802 . The energy storage  806  can be any feature or combination of features capable of storing a desired amount of energy. In some examples, the energy storage  806  can be one or several batteries, rechargeable batteries, capacitors, or the like. The energy storage  806  can have any desired capacity. In some examples, the energy storage  806  can have a capacity so as to enable operation of the headset  802  using power from energy storage  806  for duration of at least 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 10 hours, 20 hours, 50 hours, or any other or intermediate length of time. 
     The headset  802  can optionally include the wired communicator  808 . In some examples, the wired communicator  808  can include a connector and/or any other hardware or software component used in receiving power and/or data, including audio data, via the connector. 
     The headset  802  can optionally include a wireless communicator  810 , which can be, for example, a wireless receiver. The wireless communicator  810  can, in some examples, include an antenna and software or hardware components used to control and/or operate the antenna. The wireless communicator  810  can receive data, which can include, for example, audio data from a user device and can provide this data to other components of the headset  802  including, for example, the control circuit  846 . 
     The headset  802  can optionally include a generator  812 . In some examples, the generator  812  can be configured to generate sound, video, or both. The generator  812  can include a speaker, a display, and the like. 
     In some examples, the components of the headset  802  can be in communication with and/or electrically connected via a circuit board  814 . While depicted in the example of  FIG. 8  as a circuit board  814 , the components of the headset  802  can be connected via any desired features or components including, for example, one or several wires, one or several light guides, or the like. 
     An angular detection system is disclosed. The angular detection system can comprise: a stationary component; a rotating component, wherein the rotating component is capable of rotating relative to the stationary component; a magnet located on the rotating component, where the magnet generates a plurality of magnetic flux lines; a plurality of sensors located on the stationary component, where the plurality of sensors is placed along a motion path of the magnet, wherein the plurality of sensors is configured to sense the plurality of magnetic flux lines and generate one or more signals indicative of the sensed plurality of magnetic flux lines; and logic configured to determine an angle of rotation of the angular detection system based on the one or more signals. Additionally or alternatively, in some examples, the magnet is a permanent magnet. Additionally or alternatively, in some examples, the angular detection system further comprises: a screw for attaching the magnet to the rotating component, wherein the screw rotates as the rotating component rotates. Additionally or alternatively, in some examples, the rotating component is a roll-bar included in a headset. Additionally or alternatively, in some examples, the stationary component is a portion of a frame included in a headset. Additionally or alternatively, in some examples, the plurality of sensors includes one or more of Hall effect sensors, anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) sensors, and tunnel magnetoresistance (TMR) sensors. Additionally or alternatively, in some examples, the plurality of sensors includes at least two different types of sensors. Additionally or alternatively, in some examples, separation distances between pairs of adjacent sensors of the plurality of sensors are the same. Additionally or alternatively, in some examples, a first sensor of the plurality of sensors is located at a reference point along the motion path, a second sensor of the plurality of sensors is located 10 degrees counter-clockwise from the reference point, and a third sensor of the plurality of sensors is located 20 degrees counter-clockwise from the reference point. Additionally or alternatively, in some examples, the angular detection system further comprising: a flex board located on the stationary component, the flex board including: the plurality of sensors, and one or more routing traces that connect the plurality of sensors to a power supply. Additionally or alternatively, in some examples, the angular detection system is capable of sensing an angle of rotation of the system of up to 20 degrees. Additionally or alternatively, in some examples, each of the plurality of sensors is associated with a unique pre-assigned range. 
     A method for detecting an angle of rotation of a head-worn device is disclosed. The method can comprise: generating a plurality of magnetic flux lines from a magnet; rotating the magnet to a location along a motion path; sensing the plurality of magnetic flux lines using a plurality of sensors; for each of the plurality of sensors, generating a signal indicative of a strength of the sensed plurality of magnetic flux lines; and determining the angle of rotation based on the signals from the plurality of sensors. Additionally or alternatively, in some examples, the method further comprises: determining the location of the magnet by determining for at least one of the plurality of sensors that the at least one of the plurality of sensors is not located in a path of the plurality of magnetic flux lines when the respective signal is equal to zero. Additionally or alternatively, in some examples, the determination of the angle of rotation includes: comparing intensities of the signals of the plurality of sensors, associating the location of the magnet to one of the plurality of sensors based on the comparison, and determining the angle of rotation based on the association. Additionally or alternatively, in some examples, the determination of the angle of rotation includes: determining whether an intensity of at least one signal generated by at least one of the plurality of sensors is greater than or equal to a threshold value; and in accordance with the determination that the intensity is greater than or equal to the threshold value, determining that the angle of rotation is within a range associated with the threshold value. Additionally or alternatively, in some examples, the method further comprising: combining the signals generated by the plurality of sensors using a transfer function, wherein the determination of the angle of rotation is based on the combined signals. 
     A headset is disclosed. The headset may comprise: a frame; a roll-bar; an angular detection system including: a magnet located on one of the frame or roll-bar, where the magnet generates a plurality of magnetic flux lines; a plurality of sensors located on the other of the frame or the roll-bar, where the plurality of sensors is placed along a motion path of the magnet, wherein the plurality of sensors is configured to sense the plurality of magnetic flux lines and generate one or more signals indicative of the sensed plurality of magnetic flux lines; and logic configured to determine an angle of rotation of the angular detection system based on the one or more signals. Additionally or alternatively, in some examples, the headset is included in a virtual reality system. Additionally or alternatively, in some examples, the headset is headphones that exclude a display. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20180928
Publication Date: 20200211
Grant Date: 20200211
Priority Date: 20180928
Inventors: BHATTACHARYYA, MANOJ K.
BLOOM, DANIEL RAY
ANANTHARAMAN, RAJESH
Assignee: APPLE INC
CPC Classifications: [{"code": "G01D5/145", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/091", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/072", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0023", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01R33/098", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/011", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/145", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/093", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/096", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/038", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/093", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/011", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/098", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/145", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/038", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/096", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01R33/0094", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01R33/0005", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 69410772