Patent Publication Number: US-11045117-B2

Title: Systems and methods for determining axial orientation and location of a user&#39;s wrist

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 15/705,644, filed Sep. 15, 2017, and published on Mar. 22, 2018 as U.S. Patent Publication No. 2018-0078183 which claims the benefit under 35 USC 119(e) of U.S. Patent Application No. 62/398,338, filed Sep. 22, 2016, the contents of which are incorporated herein by reference in their entirety for all purposes. 
    
    
     FIELD OF THE DISCLOSURE 
     This relates to systems and method for determining axial orientation and location of a user&#39;s wrist. 
     BACKGROUND OF THE DISCLOSURE 
     Mobile electronic devices, such as mobile phones, smart phones, table computers, media players, and the like, have become quite popular. Many users carry a device almost everywhere they go and use their devices for a variety of purposes, including making and receiving phone calls, sending and receiving text messages and emails, navigation (e.g., using maps and/or a GPS receiver), purchasing items in a store (e.g., using contactless payment systems), and/or accessing the Internet (e.g., to look up information). 
     A user&#39;s mobile device may not always be readily accessible. For instance, when a mobile device receives a phone call, the device may be in a user&#39;s bag or pocket, and the user may be walking, driving, carrying something, or involved in other activity that can make it inconvenient or impossible for the user to reach into the bag or pocket to find the device. 
     A wearable device can assist with accessibility of information from the mobile device. In some examples, the user&#39;s movements can lead to frequent changes in the configuration and/or orientation of the wearable device relative to the user&#39;s wrist. In some instances, measurements regarding the user&#39;s mobility and functions can be skewed. 
     SUMMARY OF THE DISCLOSURE 
     This relates to systems and methods for determining the axial orientation and location of the user&#39;s wrist. The axial orientation and location can be determined using one or more sensors located on the strap, the device underbody, or both. For example, the strap (attached to the device underbody) can include a plurality of elastic sections and a plurality of rigid sections. Each elastic section can include one or more flex sensors. The flex sensors can be sensors configured to generate one or more signals indicative of the expansion or contractions of the user&#39;s wrist due to extension or tension, for example. In some examples, on or more electromyography (EMG) sensors can be included to measure the user&#39;s electrical signals, and the user&#39;s muscle activity can be determined. Measurements from the EMG sensors can be used in conjunction with one or more other sensor measurements, such as PPG sensor measurements, to determine one or more user characteristics. In some examples, a plurality of strain gauges (e.g., piezoelectric sensors) can be included to generate one or more signals indicative of any changes in shape, size, and/or physical properties of the user&#39;s wrist. In some examples, the device can include a plurality of capacitance sensors for increased granularity and/or sensitivity in measuring the amount of tension exerted by the user&#39;s wrist. The systems and methods disclosed can include analysis and feedback to a user regarding the user&#39;s performance (e.g., sports performance), noise reduction and/or cancellation, hydration detection for prolonged EMG sensor longevity, and user identification. 
     The wearable device can include a wristband or strap that can incorporate one or more sensors capable of determining the axial orientation of the user&#39;s wrist and/or capable of detecting changes in the position of the wearer&#39;s wrist. In some examples, the sensors can include 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented 
         FIG. 2  illustrates an exemplary wearable device communicating wirelessly with a host device according to examples of the disclosure. 
         FIG. 3  illustrates a block diagram of an exemplary wearable device according to examples of the disclosure. 
         FIG. 4A  illustrates a perspective view of an exemplary wearable device having a strap that can include a plurality of elastic sections and a plurality of rigid sections according to examples of the disclosure. 
         FIG. 4B  illustrates a perspective view of an exemplary wearable device having a strap including one or more electrodes embedded at least partially within one or more elastic sections according to examples of the disclosure. 
         FIG. 4C  illustrates a perspective view of an exemplary wearable device having a strap that can include strain gauge sensors according to examples of the disclosure. 
         FIG. 5  illustrates an exemplary method for providing analysis and feedback to a user regarding the user&#39;s sports performance according to examples of the disclosure. 
         FIG. 6  illustrates a perspective view of an exemplary wearable device having a strap that can include capacitive sensors according to examples of the disclosure. 
         FIG. 7A  illustrates a perspective view of an exemplary wearable device having a strap that can include capacitive and EMG sensors according to examples of the disclosure. 
         FIG. 7B  illustrates a perspective view of an exemplary wearable device having a strap that can include capacitive and sensors and a plurality of elastic sections 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. 
     This relates to systems and methods for determining the axial orientation and location of the user&#39;s wrist. The axial orientation and location can be determined using one or more sensors located on the strap, the device underbody, or both. For example, the strap (attached to the device underbody) can include a plurality of elastic sections and a plurality of rigid sections. Each elastic section can include one or more flex sensors. The flex sensors can be sensors configured to generate one or more signals indicative of the expansion or contractions of the user&#39;s wrist due to extension or tension, for example. In some examples, on or more electromyography (EMG) sensors can be included to measure the user&#39;s electrical signals, and the user&#39;s muscle activity can be determined. Measurements from the EMG sensors can be used in conjunction with one or more other sensor measurements, such as PPG sensor measurements, to determine one or more user characteristics. In some examples, a plurality of strain gauges (e.g., piezoelectric sensors) can be included to generate one or more signals indicative of any changes in shape, size, and/or physical properties of the user&#39;s wrist. In some examples, the device can include a plurality of capacitance sensors for increased granularity and/or sensitivity in measuring the amount of tension exerted by the user&#39;s wrist. The systems and methods disclosed can include analysis and feedback to a user regarding the user&#39;s performance (e.g., sports performance), noise reduction and/or cancellation, hydration detection for prolonged EMG sensor longevity, and user identification. 
       FIGS. 1A-1C  illustrate systems in which examples of the disclosure can be implemented.  FIG. 1A  illustrates an exemplary mobile telephone  136  that can include a touch screen  124 .  FIG. 1B  illustrates an exemplary media player  140  that can include a touch screen  126 .  FIG. 1C  illustrates an exemplary wearable device  144  that can include a touch screen  128  and can be attached to a user using a strap  146 . The systems of  FIGS. 1A-1C  can utilize the systems and methods for determining axial orientation of the user&#39;s wrist, as will be disclosed. 
       FIG. 2  illustrates an exemplary wearable device communicating wirelessly with a host device according to examples of the disclosure. Wearable device  200  can be a wristwatch-like device with face portion  204  connected to strap  206 . Face portion  204  can include, for example, a touchscreen display  205  that can be appropriately sized depending on where wearable device  200  is intended to be worn. The user can view information presented by wearable device  200  on touchscreen display  205  and can provide input to wearable device  200  by touching touchscreen display  205 . In some examples, touchscreen display  205  can occupy most or all of the front surface of face portion  204 . 
     Strap  206  (also referred to herein as a wristband or wrist strap) can be provided to allow device  200  to be removably worn (e.g., around the user&#39;s wrist) by the user. In some examples, strap  206  can include a flexible material (e.g., fabrics, flexible plastics, leather, chain links, or flexibly interleaved plates or links made of metal or other rigid materials) and can be connected to face portion  204  (e.g., by hinges, loops, or other suitable attachment devices or holders). In some examples, strap  206  can be made of two or more sections of a rigid material joined by clasp  208 . One or more hinges can be positioned at the junction of face  204  and proximal ends  212 A and  212 B of strap  206  and/or elsewhere along the lengths of strap  206  (e.g., to allow a user to put on and take off wearable device  200 ). Different portions of strap  206  can include different materials. For example, strap  206  can include flexible or expandable sections alternating with rigid sections. In some examples, strap  206  can include removable sections, allowing wearable device  200  to be resized to accommodate a particular user&#39;s wrist size. In some examples, strap  206  can include portions of a continuous strap member that runs behind or through face portion  204 . Face portion  204  can be detachable from strap  206 , permanently attached to strap  206 , or integrally formed with strap  206 . 
     In some examples, strap  206  can include clasp  208  that can facilitate with connection and disconnection of distal ends of strap  206 . In some examples, clasp  208  can include buckles, magnetic clasps, mechanical clasps, snap closures, etc. In some examples, wearable device  200  can be resized to accommodate a particular user&#39;s wrist size. Accordingly, device  200  can be secured to a user&#39;s person (e.g., around the user&#39;s wrist) by engaging clasp  208 . Clasp  208  can be subsequently disengaged to facilitate removal of device  200  from the user&#39;s person. 
     In some examples, strap  206  can be formed as a continuous band of an elastic material (including, for example, elastic fabrics, expandable metal links, or a combination of elastic and inelastic sections), allowing wearable device  200  to be put on and taken off by stretching a band formed by strap  206  connecting to face portion  204 . Thus, clasp  208  may not be required. 
     Strap  206  (including any clasp that may be present) can include one or more sensors that can allow wearable device  200  to determine whether the device is worn by the user at any given time. Wearable device can operate differently depending on whether the device is currently being worn or not. For example, wearable device  200  can inactivate various user interface and/or RF interface components when it is not being worn. In addition, in some examples, wearable device  200  can notify host device  202  when a user puts on or takes off wearable device  200 . Further, strap  206  can include sensors capable of detecting wrist articulations of a user. 
     Host device  202  can be any device that can communicate with wearable device  200 . Although host device  202  is illustrated in the figure as a smart phone, examples of the disclosure can include other devices, such as a tablet computer, a media player, any type of mobile device, a laptop or desktop computer, or the like. Other examples of host devices can include point-of-sale terminals, security systems, environmental control systems, and so on. Host device  202  can communicate wirelessly with wearable device  200  using, for example, protocols such as Bluetooth or Wi-Fi. In some examples, wearable device  200  can include electrical connector  210  that can be used to provide a wired connection to host device  202  and/or to other devices (e.g., by using suitable cables). For example, connector  210  can be used to connect to a power supply to charge an onboard battery of wearable device  200 . 
     In some examples, wearable device  200  and host device  202  can interoperate to enhance functionality available on host device  202 . For example, wearable device  200  and host device  202  can establish a pairing using a wireless communication technology, such as Bluetooth. While the devices are paired, host device  202  can send notifications of selected events (e.g., receiving a phone call, text message, or email message) to wearable device  200 , and wearable device  200  can present corresponding alerts to the user. Wearable device  200  can also provide an input interface via which a user can respond to an alert (e.g., to answer a phone call or reply to a text message). In some examples, wearable device  200  can also provide a user interface that can allow a user to initiate an action on host device  202 , such as unlocking host device  202  or turning on its display screen, placing a phone call, sending a text message, or controlling media playback operations of host device  202 . Techniques described herein can be adapted to allow a wide range of host device functions to be enhanced by providing an interface via wearable device  200 . 
     It will be appreciated that wearable device  200  and host device  202  are illustrative and that variations and modifications are possible. For example, wearable device  200  can be implemented in a variety of wearable articles, including a watch, a bracelet, or the like. In some examples, wearable device  200  can be operative regardless of whether host device  202  is in communication with wearable device  200 ; a separate host device may not be required. 
     Wearable device  200  can be implemented using electronic components disposed within face portion  204  and/or strap  206 .  FIG. 3  illustrates a block diagram of an exemplary wearable device according to examples of the disclosure. Wearable device  300  can include processing subsystem  302 , storage subsystem  304 , user interface  306 , RF interface  308 , connector interface  310 , power subsystem  312 , device sensors  314 , and strap sensors  316 . Wearable device  300  can also include other components (not explicitly shown) 
     Storage subsystem  304  can be implemented using, for example, magnetic storage media, flash memory, other semiconductor memory (e.g., DRAM, SRAM), or any other non-transitory storage medium, or a combination of media, and can include volatile and/or non-volatile media. In some examples, storage subsystem  304  can store media items such as audio files, video files, image or artwork files; information from a user&#39;s contacts (e.g., names, addresses, phone numbers, etc.); information about a user&#39;s scheduled appointments and events; notes; and/or other types of information. In some examples, storage subsystem  304  can also store one or more application programs (or apps)  334  to be executed by processing subsystem  302  (e.g., video game programs, personal information management programs, media playback programs, interface programs associated with particular host devices, and/or host device functionalities, etc.). 
     User interface  306  can include any combination of input and output devices. A user can operate input devices of user interface  306  to invoke the functionality of wearable device  300  and can view, hear, and/or otherwise experience output from wearable device  300  via output devices of user interface  306 . 
     Examples of output devices can include display  320 , speakers  322 , and haptic output generator  324 . Display  320  can be implemented using compact display technologies (e.g., liquid crystal display (LCD), light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), or the like). In some examples, display  320  can incorporate a flexible display element or curved-glass display element, allowing wearable device  300  to conform to a desired shape. One or more speakers  322  can be provided using small-form-factor speaker technologies, including any technology capable of converting electronic signals into audible sound waves. In some examples, speakers  322  can be used to produce tones (e.g., beeping or ringing) and can but need not be capable of reproducing sounds such as speech or music with any particular degree of fidelity. Haptic output generator  324  can be, for example, a device that can convert electronic signals into vibrations. In some examples, the vibrations can be strong enough to be felt by a user wearing wearable device  300 , but not so strong as to produce distinct sounds. 
     Examples of input devices can include microphone  326 , touch sensor  328 , and camera  329 . Microphone  326  can include any device that converts sound waves into electronic signals. In some examples, microphone  326  can be sufficiently sensitive to provide a representation of specific words spoken by a user. In some examples, microphone  326  can be usable to provide indications of general ambient sound levels without necessarily providing a high-quality electronic representation of specific sounds. 
     Touch sensor  328  can include, for example, a capacitive sensor array with the ability to localize contacts to a particular point(s) or region on the surface of the sensor. In some examples, touch sensor  328  can distinguish multiple simultaneous contacts. In some examples, touch sensor  328  can be overlaid over display  320  to provide a touchscreen interface (e.g., touchscreen interface  205  of  FIG. 2 ), and processing subsystem  302  can translate touch events (including taps and/or other gestures made with one or more contacts) into specific user inputs depending on what is currently displayed on display  320 . 
     Camera  329  can include, for example, a compact digital camera that includes an image sensor such as a CMOS sensor and optical components (e.g., lenses) arranged to focus an image onto the image sensor, along with control logic operable to use the imaging components to capture and store still and/or video images. Images can be stored, for example, in storage subsystem  304  and/or transmitted by wearable device  300  to other devices for storage. Depending on implementation, the optical components can provide fixed focal distance or variable focal distance. In some examples, with variable focal distance, autofocus can be provided. In some examples, camera  329  can be disposed along an edge of the face member (e.g., top edge of face portion  204  of  FIG. 2 ) and oriented to allow a user to capture images of nearby objects in the environment, such as a bar code or QR code. In some examples, camera  329  can be disposed on the front surface of face portion  204  (e.g., to capture images of the user). Any number of cameras can be provided, depending on the implementation. 
     In some examples, user interface  306  can provide output to and/or receive input from an auxiliary device, such as a headset. For example, audio jack  330  can connect via an audio cable (e.g., a standard 2.5-mm or 3.5-mm audio cable) to an auxiliary device. Audio jack  330  can include input and/or output paths. Accordingly, audio jack  330  can provide audio to and/or receive audio from the auxiliary device. In some examples, a wireless connection interface can be used to communicate with an auxiliary device. 
     Processing subsystem  302  can be implemented as one or more integrated circuits (e.g., one or more single-core or multi-core microprocessors or microcontrollers). In operation, processing system  302  can control the operation of wearable device  300 . In some examples, processing subsystem  302  can execute a variety of programs in response to program code and can maintain multiple concurrently executing programs or processes. At any given time, some or all of the program code to be executed can be stored in processing subsystem  302  and/or in storage media such as storage subsystem  304 . 
     Through suitable programming, processing subsystem  302  can provide various functionality for wearable device  300 . For example, processing subsystem  302  can execute an operating system (OS)  332  and various applications  334  such as a phone-interface application, a text-message-interface application, a media interface application, a fitness application, and/or other applications. In some examples, some or all of these application programs can interface with a host device, for example, by generating messages to be sent to the host device and/or by receiving and interpreting messages from the host device. In some examples, some or all of the application programs can operate locally to wearable device  300 . For example, if wearable device  300  has a local media library stored in storage subsystem  304 , a media interface application can provide a user interface to select and play locally stored media items. Processing subsystem  302  can also provide wrist-gesture-based control, for example, by executing gesture processing code  335  (which can be part of OS  323  or provided separately as desired). 
     RF (radio frequency) interface  308  can allow wearable device  300  to communicate wirelessly with various host devices. RF interface  308  can include RF transceiver components, such as an antenna and supporting circuitry, to enable data communication over a wireless medium (e.g., using Wi-Fi/IEEE 802.11 family standards), Bluetooth, or other protocols for wireless data communication. RF interface  308  can be implemented using a combination of hardware (e.g., driver circuits, antennas, modulators/demodulators, encoders/decoders, and other analog and/or digital signal processing circuits) and software components. In some examples, RF interface  308  can provide near-field communication (“NFC”) capability (e.g., implementing the ISO/IEC 18092 standards or the like). In some examples, NFC can support wireless data exchange between devices over a very short range (e.g., 20 cm or less). Multiple different wireless communication protocols and associated hardware can be incorporated into RF interface  308 . 
     Connector interface  310  can allow wearable device  300  to communicate with various host devices via a wired communication path, for example, using Universal Serial Bus (USB), universal asynchronous receiver/transmitter (UART), or other protocols for wired data communication. In some examples, connector interface  310  can provide a power port, allowing wearable device  300  to receive power, for example, to charge battery  340 . For example, connector interface  310  can include a connector such as a mini-USB connector or a custom connector, as well as supporting circuitry. In some examples, the connector can be a custom connector that can provide dedicated power and ground contacts, as well as digital data contacts that can be used to implement different communication technologies in parallel. For example, two pins can be assigned as USB data pins (D+ and D−) and two other pins can be assigned as serial transmit/receive pins (e.g., implementing a UART interface). The assignment of pins to particular communication technologies can be hardware or negotiated while the connection is being established. In some examples, the connector can also provide connections for audio and/or video signals, which can be transmitted to or from host device  302  in analog and/or digital formats. 
     In some examples, connector interface  310  and/or RF interface  308  can be used to support synchronization operations in which data can be transferred from a host device to wearable device  300  (or vice versa). For example, as described below, a user can customize certain information for wearable device  300  (e.g., settings related to wrist-gesture control). While user interface  306  can support data-entry operations, a user may find it more convenient to define customized information on a separate device (e.g., a tablet or smartphone) that can have a larger interface (e.g., including a real or virtual alphanumeric keyboard). The customized information can be transferred to wearable device via a synchronization operation. Synchronization operations can also be used to load and/or update other types of data in storage subsystem  304 , such as media items, application programs, personal data, and/or operating system programs. Synchronization operations can be performed in response to an explicit user request and/or automatically (e.g., when wearable device  200  resumes communication with a particular host device or in response to either device receiving an update to its copy of synchronized information). 
     Device sensors  314  can include various electronic, mechanical, electromechanical, optical, and/or other apparatus that can provide information related to external conditions around wearable device  300 . Sensors  314  can provide digital signals to processing subsystem  303 , for example, on a streaming basis or in response to polling by process subsystem  302  as desired. Any type and combination of device sensors can be used. For example, device sensors  314  can include accelerometer  342 , magnetometer  344 , gyroscopic sensor  346 , GPS (global positioning system) receiver  348 , optical sensors  362 , and barometric sensors  364 . One or more of device sensors  314  can provide information about the location and/or motion of wearable device  300 . For example, accelerometer  342  can sense acceleration (e.g., relative to freefall) along one or more axes, for example, using piezoelectric or other components in conjunction with associated electronics to produce a signal. Magnetometer  344  can sense an ambient magnetic field (e.g., Earth&#39;s magnetic field) and can generate a corresponding electrical signal, which can be interpreted as a compass direction. Gyroscopic sensor  346  can sense rotational motion in one or more directions, for example, using one or more micro-electro-mechanical systems (MEMS) gyroscopes and related control and sense circuitry. GPS receiver  348  can determine location based on signals received from GPS satellites. Optical sensors  362  can sense one or optical properties of light used, for examples, in determining photoplethsmyogram (PPG) information associated with the user. In some examples, optical sensors  362  can include ambient light sensors (ALS) to determine ambient light properties. Barometric sensors  364  can sense the atmospheric pressure to resolve vertical location information of the device. 
     Other sensors can also be included in addition to, or instead of, these examples. For example, a sound sensor can incorporate microphone  326  together with associated circuitry and/or program code to determine, for example, a decibel level of ambient sound. Temperature sensors, proximity sensors, ultrasound sensors, or the like can also be included. 
     Strap sensors  316  can include various electronic, mechanical, electromechanical, optical, or other devices that can provide information as to whether wearable device  300  is currently being worn, as well as information about forces that may be acting on the strap due to movement of the user&#39;s wrist. Examples of strap sensors  316  are described below. In some examples, signals from strap sensors  316  can be analyzed, for example, using gesture processing code  336  to identify wrist gestures based on the sensor signals. Such gestures can be used to control operations of wearable device  300 . 
     Power subsystem  312  can provide power and power management capabilities for wearable device  300 . For example, power subsystem  312  can include battery  340  (e.g., a rechargeable battery) and associated circuitry to distribute power from battery  340  to other components of wearable device  300  that can require electrical power. In some examples, power subsystem  312  can also include circuitry operable to charge battery  340 , for example, when connector interface  310  can be connected to a power source. In some examples, power subsystem can include a “wireless” charger, such as an inductive charger, to charge battery  340  without relying on connector interface  310 . In some examples, power subsystem  312  can also include other power sources (e.g., solar cell) in addition to, or instead of, battery  340 . 
     In some examples, power subsystem  312  can control power distribution to components within wearable device  300  to manage power consumption efficiently. For example, power subsystem  312  can automatically place device  300  into a “hibernation” (or sleep/inactive) state when strap sensors  316  or other sensors indicate that device  300  is not being worn by the user. The hibernation state can be designed to reduce power consumption. For example, user interface  306  (or components thereof), RF interface  308 , connector interface  310 , and/or device sensors  314  can be powered down (e.g., to a low-power state or turned off entirely), while strap sensors  316  can be powered up (either continuously or at intervals) to detect when a user puts on wearable device  300 . In some examples, while wearable device  300  is being worn, power subsystem  312  can turn display  320  and/or other components on or off depending on motion and/or orientation of wearable device  300  detected by device sensors  314 . For instance, if wearable device  300  can be designed to be worn on a user&#39;s wrist, power subsystem  312  can detect raising and rolling of the user&#39;s wrist, as is typically associated with looking at the face of a wristwatch based on information provided by accelerometer  342 . In response to this detected motion, power subsystem  312  can automatically turn display  320  and/or touch sensor  328  on. Similarly, power subsystem  312  can automatically turn display  320  and/or touch sensor  328  off in response to detecting that the user&#39;s wrist has returned to a neutral position (e.g., hanging down). As discussed below, in some examples, other sensors can be used to determine the axial orientation of the user&#39;s wrist for waking up (e.g., switching from an inactive state to an active state with higher power consumption) the wearable device or putting the device into a hibernation state. 
     Power subsystem  312  can also provide other power management capabilities, such as regulating power consumption of other components of wearable device  300  based on the source and amount of available power, monitoring and stored power in battery  340 , generating user alerts if the stored power drops below a minimum level, etc. 
     In some examples, control functions of power subsystem  312  can be implemented using programmable or controllable circuits operating in response to control signals generated by processing subsystem  302  in response to program code executing thereon, or as a separate microprocessor or microcontroller. 
     Examples of the disclosure can include variations and modifications to the block diagram illustrated in  FIG. 3 . For example, strap sensors  316  can be modified, and wearable device  300  can include a user-operable control (e.g., a button or switch) that the user can operate to provide input. Controls can also be provided, for example, to turn on or off display  320 , mute or unmute sounds from speakers  322 , etc. Wearable device  300  can include any types and combination of sensors, and in some examples, can include multiple sensors of a given type. 
     In some example, a user interface can include any combination of any or all of the components described above, as well as other components not expressly described. For example, the user interface can include just a touch screen, or a touchscreen and a speaker, or a touchscreen and a haptic device. Where the wearable device includes a RF interface, a connector interface can be omitted, and all communication between the wearable device and other devices can be conducted using wireless communication protocols. A wired power connection (e.g., for charging a battery of the wearable device) can be provided separately for any data connection. 
     Further, while the wearable device is described with reference to functional blocks, it is to be understood that these blocks are defined for convenience of description and are not intended to imply a particular physical arrangement of component parts. Further, the blocks need not correspond to physically distinct components. Blocks can be configured to perform various operations (e.g., by programming a processor or providing appropriate control circuitry), and various blocks might or might not be reconfigurable depending on how the initial configuration is obtained. Examples of the disclosure can be realized in a variety of apparatuses including electronic devices implemented using any combination of circuitry and software. Furthermore, examples of the disclosure are not limited to requiring every block illustrated in the figure to be implemented in a given wearable device. 
     A host device (e.g., host device  202  of  FIG. 2 ) can be implemented as an electronic device using blocks similar to those described above (e.g., processors, storage media, user interface devices, data communication interfaces, etc.) and/or other blocks or components. Any electronic device capable of communicating with a particular wearable device can act as a host device with respect to that wearable device. Communication between a host device and a wireless device can be implemented according to any communication protocol (or combination of protocols) that both devices can be programmed or otherwise configured to use. In some examples, such protocols (e.g., Bluetooth) can be used. In some examples, a custom message format and syntax (including, for example, a set of rules for interpreting particular bytes or sequences of bytes in a digital data transmission) can be defined, and messages can be transmitted using standard serial protocols (e.g., a virtual serial port defined in certain Bluetooth standards). 
     Examples of the disclosure can include systems and methods that can assist the user with determining and evaluating information related to the user&#39;s wrist. In some examples, the exemplary wearable device can be capable of measuring the amount of tension in the user&#39;s wrist.  FIG. 4A  illustrates a perspective view of an exemplary wearable device having a strap that can include a plurality of elastic sections and a plurality of rigid sections according to examples of the disclosure. Wearable device  400  can include face member  402  and strap  404 . Strap  404  can be connected to face member  402  using strap holders  406  and  408  disposed along top and bottom sides of face member  402 . In some examples, strap holders  406  and  408  can be expandable strap holders. 
     In some examples, strap  404  can include a plurality of elastic sections  405  interleaved with a plurality of rigid sections  407 . Each elastic section  405  can include one or more flex sensors (e.g., flex sensor  350  illustrated in  FIG. 3 ). The flex sensors can be sensors configured to expand when the user&#39;s wrist extends, for example. In some example, the flex sensors can be configured to contract when the user&#39;s wrist has more tension. The flex sensors can include an elastic material (e.g., elastic strap) or can include at least a partially embedded material. An electrical resistance can be measured across strap  404 , the flex sensors, elastic section(s), and/or the partially embedded material. When strap  404  expands, an increase in electrical resistance can be measured; when strap  404  contracts, a decrease in electrical resistance can be measured. 
     In some examples, elastic sections  405  can include one or more electrodes embedded at least partially within the elastic section, as illustrated in  FIG. 4B . Electrodes  438  can be configured as electromyography (EMG) sensors, which can sense muscle activity by measuring electrical activity. In some examples, electrodes  438  can be disposed on elastic section  405  such that an exposed surface of electrodes  438  can contact the user&#39;s wrist (e.g., contacting the inner side of strap  404 ). In this manner, one elastic section  405  can be coupled to multiple measurement types, such as strain and EMG signals. 
     Measurements from the EMG sensors can be used in conjunction with one or more other sensor measurements, such as PPG sensor measurements, to determine one or more user characteristics. For example, the device can be configured to determine the user&#39;s calorimetric expenditure using the determined muscle activity (related to the electrical activity measured using the EMG sensors) and the determined user&#39;s heart rate (related to the blood oxygen activity measured using the PPG sensors). 
     In some examples, strap  404  can include a plurality of strain gauges, as illustrated in  FIG. 4C . The plurality of strain gauges can include, for example, piezoelectric sensors  452 . Strap  404  can be secured around at least a portion of the user&#39;s wrist. When the user&#39;s wrist moves, one or more materials included in piezoelectric sensors  452  can change shape (e.g., deform) and/or any physical properties, and a signal (e.g., voltage) proportional to the change in shape can be generated. In some examples, each of the piezoelectric sensors  452  can be independently controlled, which can give the device capability of determining the location of the tension. 
     Coupled with the signals(s) indicative of the amount of tension, one or more strain “images” of the user&#39;s wrist can be generated. The strain image can be a two dimensional representation of the location and intensity of tension. The strain image (or information from the strain gauges) can be used at least in part to determine axial orientation of the wearable device on the user&#39;s wrist. For example, when a user grips his or her hand, the bottom side (e.g., palm side) of the user&#39;s wrist can experience larger movement due to the tendons undergoing movement and being located closer to the bottom side. One or more strain gauges that experience greater strain (e.g., higher measured voltage) can be associated with the location(s) of the user&#39;s tendon(s). From this association, the axial orientation of the device can be determined. 
     In some examples, the strain gauges can be coupled with one or more other types of sensors to provide analysis and user feedback.  FIG. 5  illustrates an exemplary method for providing analysis and feedback to a user regarding the user&#39;s performance according to examples of the disclosure. The device can determine the axial orientation on the user&#39;s wrist (step  552  of process  550 ). The user can grip an instrument. In some examples, the instrument can be a sports instrument (e.g., golf club, baseball bat, etc.)(step  554  of process  550 ). The strain gauges can be used to determine how tightly the user is gripping the sports instrument (step  556  of process  550 ). The user may then proceed to follow through with a specific sports motion (e.g., swinging the golf club or throwing a football) (step  558  of process  550 ). The motion sensors (e.g., accelerometer  342  or barometric sensors  364  of  FIG. 3 ) can measure the user&#39;s performance in terms of, for example, acceleration, trajectory of the sports instrument, etc. (step  560  of process  550 ). The device&#39;s controller can analyze the user&#39;s grip and performance by comparing the measured and determined information to ideal characteristics (e.g., stored in memory), for example (step  562  of process  550 ). From the comparison, the device can provide a simulation of the user&#39;s performance and/or feedback to the user on how to improve (step  564  of process  550 ). 
     Although  FIG. 5  illustrates an exemplary method for analysis of sports performance, examples of the disclosure can include analysis and feedback for any type of user motion including gross motion (e.g., the user brushing his or her hair) and fine motor motion (e.g., the user typing on a keyboard). In some examples, if the user is moving or stirring more than a predetermined amount or if the user&#39;s tension is greater than a predetermined amount, the strain gauges may be perturbed and measurements from the strain gauges may be inaccurate. One or more EMG sensors can be configured to measure the tension of the user&#39;s wrist. Additionally, although  FIG. 5  is discussed in the context of strain gauges used to determine the axial orientation, examples of the disclosure can include other types of sensors, such as capacitive sensors discussed below. 
     In some examples, the exemplary wearable device can be capable of measuring the amount of tension with increased granularity and/or sensitivity.  FIG. 6  illustrates a perspective view of an exemplary wearable device having a strap that can include capacitive sensors according to examples of the disclosure. Wearable device  600  can include face member  602  and strap  604 . Strap  604  can be connected to face member  602  using strap holders  606  and  608  disposed along top and bottom sides of face member  602 . 
     Strap  604  can include a plurality of capacitance sensors  618 . Plurality of capacitance sensors  618  can be located on the inner side (i.e., side facing the underbody of the wearable device body) of strap  604 . In some examples, plurality of capacitance sensors  618  can also be located at least partially on the outer side of strap  604 . Plurality of capacitance sensors  618  can be configured to sense one or more changes in capacitance due to, for example, the increased (or decreased) capacitive coupling as the user&#39;s wrist applies force to the electrodes. One or more capacitance “images” of the user&#39;s wrist can be generated. The capacitance image can be a two-dimensional representation of the location and/or intensity of applied force. In some examples, plurality of capacitance sensors  618  can include a grid (e.g., drive lines and sense lines arranged in rows and columns) of electrodes. 
     In some examples, strap holders  606  and  608  can include one or more electrical connections for transmitting signals from the one or more sensors (e.g., capacitance sensors  618 ) to the body (e.g., including face member  602 ) of the wearable device. In some examples, some of the capacitance sensors and/or other sensors (e.g., optical sensors) can be configured to couple (e.g., capacitively couple) to one or more sensors included in the body. A processor or controller can be configured utilize the coupling to transmit the signal(s) from the sensors included in strap  704  to the body of wearable device  600 . 
       FIG. 7A  illustrates an exemplary wearable device having a strap that can include EMG and capacitive sensors according to examples of the disclosure. Wearable device  700  can include face member  702  and strap  704 . Strap  704  can be connected to face member  702  using strap holders  706  and  708  disposed along top and bottom sides of face member  702 . In some examples, strap holders  706  and  708  can be expandable strap holders. 
     Strap  704  can also include EMG sensors  738  and/or capacitance sensors  718 . EMG sensors  738  can include one or more electrodes configured to measure electrical activity. One or more signals indicative of the measured electrical activity can be generated, and the user&#39;s muscle activity can be determined from the signal(s). An exposed surface of EMG sensors  738  can contact the user&#39;s wrist (e.g., contacting the inner side of strap  704 ). 
     Capacitance sensors  718  can also be located on the inner side (i.e., side facing the underbody of the wearable device body) of strap  704 . In some examples, plurality of capacitance sensors  718  can also be located at least partially on the outer side of strap  704 . Plurality of capacitance sensors  718  can be configured to sense one or more changes in capacitance due to, for example, the increased (or decreased) capacitive coupling as the user&#39;s wrist applies force to the electrodes. One or more capacitance “images” of the user&#39;s wrist can be generated. The capacitance image can be a two dimensional representation of the location and/or intensity of applied force. In some examples, plurality of capacitance sensors  718  can include a grid (e.g., drive lines and sense lines arranged in rows and columns) of electrodes. 
     In some examples, capacitance sensors  718  can be located on one side (e.g., top side) of strap  704 , and EMG sensors  738  can be located on the other side (e.g., bottom side) of strap  704 . Alternatively, capacitance sensors  718  can be interleaved with EMG sensors  738  (not shown). 
     In some examples, capacitance sensors  718  can be used for hydration (e.g., water and/or sweat) detection for prolonged EMG sensor longevity. When the capacitance sensors  718  detect the hydration, the device can disable or deactivate EMG sensors  738  to prevent from corrosion of the EMG sensors  738  when subject to hydration. The device can optionally inform the user of the hydration conditions and can ask the user to dry the EMG sensors  738 . When the capacitance sensors  718  detects a level of hydration less than a predetermined level, the controller or processor can allow activation of EMG sensors  738 . 
     In some examples, strap  704  can include a plurality of elastic sections, as illustrated in  FIG. 7B . Each elastic section  705  can include one or more flex sensors (e.g., flex sensor  350  illustrated in  FIG. 3 ). The flex sensors can be sensors configured to expand when the user&#39;s wrist extends, for example. In some example, the flex sensors can be configured to contract when the user&#39;s wrist has more tension. The flex sensors can include an elastic material (e.g., elastic strap) or can include at least a partially embedded material. An electrical resistance can be measured across strap  704 , the flex sensors, elastic section(s)  705 , and/or the partially embedded material. When strap  704  expands, an increase in electrical resistance can be measured; when strap  604  contracts, a decrease in electrical resistance can be measured. 
     In some examples, one or more of the elastic sections  705  can include one or more EMG sensors  738  disposed on or embedded at least partially within elastic sections  705 . In this manner, one elastic section  705  can be coupled to multiple measurement types, such as strain and EMG signals. Moreover, the information from the strain and/or EMG signals can be used in conjunction with information from one or more other sensors (e.g., capacitance sensors  718 , optical sensors  362  illustrated in  FIG. 3 , piezoelectric sensors  452  illustrated in  FIG. 4C , accelerometer  342  illustrated in  FIG. 3 , gyroscopic sensors  346  illustrated in  FIG. 3 , magnetometer  344  illustrated in  FIG. 3 , and/or barometric sensor  364  illustrated in  FIG. 3 ) included in the strap and/or watch body to determine one or more user characteristics. For example, wearable device  700  can be capable of generating one or more images of the user&#39;s wrist. The images can include information such as amount and/or location of the user&#39;s tension (e.g., grip), axial location of the device on the user&#39;s wrist, motion and/or rotation of the user&#39;s wrist wearable device, vertical location of the user&#39;s wrist, and/or muscle activity of the user. 
     Another exemplary use of the systems and methods disclosed herein can be for weight training. For example, the user can be performing a bicep curl. One or more motion sensors (e.g., accelerometer) can determining the timing of when the user can be performing the bicep curl. The motion sensors can associate the timing with the user&#39;s grip of the weights or dumbbells determined by the strain gauges (e.g., piezoelectric sensors). The timing of the bicep curl and user&#39;s grip can further be associated with the muscle activity determined by the EMG sensors. The timing of the bicep curl, the user&#39;s grip, and the muscle activity can optionally be associated with the user&#39;s heart rate determined by, for example, the PPG (e.g., optical sensors) sensors. The device can analyze the user&#39;s performance and can provide feedback and/or, for example, calorimetric data related to the user&#39;s weight lifting performance. For example, the device can inform the user that the user is over rotating his or her wrist during the exercise and/or is gripping the weights too tightly. 
     In addition to the one or more sensors disclosed above capable of determining location and performance of the user&#39;s wrist, the one or more sensors can give the wearable device capability of automatically self-calibrating the axial location and orientation. For example, instead of prompting the user, each time the wearable device is attached to their wrist, for information regarding which wrist (e.g., left or right) the strap of the wearable device is secured around, the wearable device can determine such information from the one or more sensors disclosed above. For example, a user&#39;s left arm (attached to the user&#39;s left wrist) can have certain ranges of motion that the user&#39;s right arm (attached to the user&#39;s right wrist) cannot due to the limited bending angles of each user&#39;s elbow joints). The wearable device can utilize information from the EMG sensors, barometric sensors, and/or gyroscopic sensors, to discern between the user&#39;s left wrist and right wrist by associating only certain ranges of motion with the user&#39;s left wrist and other ranges of motion with the user&#39;s right wrist. As another example, the wearable device can automatically detect whether the wearable device body is located on the palm side of the user&#39;s wrist using the flex, capacitance, and/or piezoelectric sensors based the location of the user&#39;s tendons. In some examples, the device can self-calibrate when the device is first attached to the user&#39;s wrist (e.g., detected using the optical and/or capacitance sensors), at certain predetermined intervals (e.g., every 30 minutes), and/or when one or more signal values change (e.g., by more than 10%). 
     Additionally or alternatively, the wearable device can use one or more sensors for noise reduction and/or cancellation. For example, adjacent EMG sensors  738  can experience the same amount of electrical activity from the user&#39;s muscles. If the signals from the adjacent EMG sensors  738  vary (e.g., a non-zero differential exists), then a processor or controller can utilize the information to subtract, scale, or execute an algorithmic function to reduce or cancel the noise. 
     Examples of the disclosure can also include systems and methods that can allow a user to control the wireless device and/or host device using movements and/or axial orientation of the wrist. For example, the wearable device can be in communication with a television. The wearable device can recognize one or more gestures and/or sequences that a user can perform as matching one or more predetermined gestures and/or sequences. The wearable device can execute and/or communicate a command associated with the predetermined gesture and/or sequence to commands (e.g., as a substitute for a remote control) to the television. 
     Examples of the disclosure can also include systems and methods that can be used for authenticating and/or identifying the user based on one or more properties of the user&#39;s wrist. Each user can have one or more wrist profiles (e.g., wrist size, tendon locations, wrist shape, etc.). When the user attaches the wearable device to the wrist, a processor or controller can match the wrist profile to a stored wrist profile. The stored wrist profile can be associated with the user and can be used to unlock (i.e., give the user access to full range of functions) the device. In some examples, the stored wrist profiles can be used for restoring calibration settings unique to the user and/or user preferences. 
     A strap for a wearable device is disclosed. The strap can comprise: an inner side and an outer side; a plurality of strap holders configured to attach to a first edge and a second edge of a wearable device body; and a plurality of capacitance sensors located on the inner side of the strap, the plurality of capacitance sensors configured to sense one or more change in capacitance due to one or more forces of a user&#39;s wrist causing one or more changes in capacitance coupling, the plurality of capacitance sensors configured to generate one or more capacitance signals indicative of the one or more changes in capacitance coupling. Additionally or alternatively, in some examples, the strap further comprises: a second plurality of capacitance sensors configured to capacitively couple to the plurality of capacitance sensors and located on the outer side of the strap. Additionally or alternatively, in some examples, the strap further comprises: a plurality of elastic sections, each elastic section including at least one flex sensor, wherein each flex sensor is configured to contract when the user&#39;s wrist has more tension and generate one or more signals indicative of the contraction; and a plurality of rigid sections, one or more of the plurality of elastic sections separated by one or more of the plurality of rigid sections. Additionally or alternatively, in some examples, the strap further comprises: a plurality of electromyography sensors configured to measure one or more electrical activities of the user&#39;s wrist. Additionally or alternatively, in some examples, the strap further comprises: a plurality of elastic sections, wherein the plurality of electromyography sensors are at least partially embedded in the plurality of elastic sections. Additionally or alternatively, in some examples, the plurality of electromyography sensors is interleaved with the plurality of capacitance sensors. Additionally or alternatively, in some examples, the strap further comprises: one or more piezoelectric sensors configured to measure one or more strains caused by the user&#39;s wrist. Additionally or alternatively, in some examples, the strap further comprises: one or more second capacitance sensors configured to capacitively couple to one or more sensors located in a body of a wearable device, wherein the logic is further configured to transmit the one or more capacitance signals to the body of the wearable device using the one or more second capacitance sensors. Additionally or alternatively, in some examples, the plurality of capacitance sensors is arranged as a grid of drive lines and sense lines. 
     A method of determining a performance of a wrist of a user is disclosed. The method can comprise: determining a tension of the wrist of the user using one or more strain gauges; determining a motion of the wrist using one or more of an accelerometer, gyroscopic sensors, and barometric sensors; and simulating the performance of the wrist using the determined tension and the determined motion. Additionally or alternatively, in some examples, the method further comprises: comparing the simulated performance to a stored one or more ideal performances; and providing the simulation and a performance analysis to the user. Additionally or alternatively, in some examples, the performance is associated with a sports performance and the tension of the wrist includes gripping a sports instrument. 
     A device is disclosed. The device can comprise: a device body including a top side, an underside, a first edge, and a second edge; a display located on the top side of the device body; a strap comprising: a plurality of strap holders configured to attach to the first and second edges of the device body; an inner side and an outer side; a plurality of strap holders configured to attach to a first edge and a second edge of a wearable device body; a plurality of capacitance sensors located on the inner side of the strap, the plurality of capacitance sensors configured to sense one or more change in capacitance due to one or more forces of a user&#39;s wrist causing one or more changes in capacitance coupling, the plurality of capacitance sensors configured to generate one or more capacitance signals indicative of the one or more changes in capacitance coupling; and logic configured to: receive the one or more capacitance signals, and generating one or more capacitance images of the user&#39;s wrist from the received on or more capacitance signals, the one or more capacitance images include a two-dimensional representation of location, intensity, or both of the one or more forces. Additionally or alternatively, in some examples, the device is capable of automatic self-calibration, wherein self-calibration includes one or more of determining an axial location and determining an axial orientation of the device body on the wrist of the user. 
     A method is disclosed. The method can comprise: determining one or more axial orientations of a device body on a wrist of a user, the determination comprising: activating one or more sensors to detect one or more tendons of the user, determining a location of the one or more sensors on the device body or on a strap attached to the device body, and associating the one or more axial orientations to the determination location; and determining one or more axial locations of the device body, the determination comprising: detecting a plurality of motions of the wrist of the user, comparing the detected plurality of motions to one or more stored ranges of motion, and associating the detected plurality of motions to the one or more axial locations. Additionally or alternatively, in some examples, the method further comprises: determining one or more of a shape and a size of the wrist of the user; comparing the determined one or more shape and size of the wrist of the user to one or more stored user profiles; and unlocking the device when the determined one or more shape and size of the wrist of the user match the one or more stored user profiles. Additionally or alternatively, in some examples, the method further comprises: restoring one or more of calibration settings and preferences unique to the user. Additionally or alternatively, in some examples, the determining the one or more axial orientations and the determining the one or more axial locations are automatic. Additionally or alternatively, in some examples, the method further comprises: detecting a coupling of the device body to the user, wherein the determining the one or more axial orientations and the determining the one or more axial locations are performed in response to the detected coupling. Additionally or alternatively, in some examples, the method further comprises: detecting a change in one or more of the one or more axial orientations and one or more axial locations, wherein the determining the one or more axial orientations and the determining the one or more axial locations are performed when an amount of the detected change is greater than a predetermined amount. 
     Although 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 various examples as defined by the appended claims.