PATENT DOCUMENT

Publication Number: US-10936092-B1
Application Number: US-201815879346-A
Country: US
Kind Code: B1

Title: Force-sensing structures for an electronic device

Abstract:
Embodiments are directed to a force sensor used within an electronic device, such as a stylus, watch, laptop, or other electronic device. A force sensor may be positioned, for example, within a stylus body. The force sensor may include an input structure constrained within a housing by a compliant member. The input structure may extend at least partially out of the stylus body and be configured to receive a force input. One or more sensors of the force sensor may detect a value of a displacement of the input structure caused by the force input. A processing unit may determine a value of the force input using a spring characteristic of the compliant member and the detected value of displacement.

Claims:
What is claimed is: 
     
       1. An input device, comprising:
 an enclosure defining an interior volume; and 
 a force sensor at least partially positioned within the interior volume and comprising:
 a housing coupled to the enclosure, wherein the housing defines a first groove; 
 an input structure extending through the housing and out of the enclosure, the input structure configured to receive a force input, wherein the input structure defines a second groove aligned with the first groove; 
 a compliant member coupled to and extending radially between an inner surface of the housing and an outer surface of the input structure, the compliant member being elastically moveable in response to movement of the input structure relative to the housing, wherein the compliant member is constrained within the housing by the first groove and the second groove; and 
 a sensor positioned within the housing and configured to detect a value of a displacement of the input structure caused by the force input. 
 
 
     
     
       2. The input device of  claim 1 , wherein:
 the enclosure is a stylus body; 
 the input structure is a shaft extending along a longitudinal axis of the stylus body; 
 the displacement is one or both of an axial movement or tilt of the input structure relative to the housing; 
 the compliant member is an O-ring encircling the shaft within the housing and having a spring characteristic that controls deformation of the O-ring; 
 the sensor comprises an electrode positioned at an end of the shaft, within the housing, and is configured to output a signal corresponding to the value of the displacement; and 
 the input device further comprises a processing unit configured to determine a value of the force input using both the spring characteristic and the signal. 
 
     
     
       3. The input device of  claim 2 , wherein:
 the force input results from contact between a tip of the shaft and another electronic device; and 
 the input structure is configured to depict a graphical output that is responsive to the value of the force input as determined by the processing unit. 
 
     
     
       4. The input device of  claim 1 , wherein:
 the compliant member is a first compliant member contacting the housing and the input structure; and 
 the force sensor further comprises a second compliant member contacting the housing and the input structure. 
 
     
     
       5. The input device of  claim 4 , wherein:
 the first compliant member is separated from the second compliant member by an offset distance; and 
 the offset distance at least partially determines at least one of a radial stiffness or an axial stiffness of the input structure. 
 
     
     
       6. The input device of  claim 1 , wherein:
 the compliant member impedes the displacement of the input structure according to a spring characteristic; and 
 the input device is configured to transmit a signal to another electronic device, the signal derived from the value of the displacement and the spring characteristic of the compliant member. 
 
     
     
       7. The input device of  claim 6 , wherein the spring characteristic varies based on at least one of:
 a width of the compliant member; 
 a shape of the compliant member; 
 a material of the compliant member; or 
 a position of the compliant member relative to the input structure. 
 
     
     
       8. An input device, comprising:
 a force sensor, comprising:
 a housing, wherein the housing defines a first groove and a second groove; 
 an input structure at least partially surrounded by the housing and configured to receive a force input, wherein the input structure defines:
 a third groove aligned with the first groove; and 
 a fourth groove aligned with the second groove; 
 
 a first compliant member encircling the input structure within the housing, the first compliant member being coupled to a radially inner surface of the housing and a radially outer surface of the input structure, wherein the first compliant member is constrained within the housing by the first groove and the third groove; 
 a second compliant member encircling the input structure within the housing, the second compliant member being coupled to the radially inner surface of the housing and the radially outer surface of the input structure, the second compliant member being axially displaced from the first compliant member, wherein the first compliant member and the second compliant member are configured to deform in response to the force input, thereby controlling a movement of the input structure relative to the housing, wherein the second compliant member is constrained within the housing by the second groove and the fourth groove; and 
 a sensor configured to detect the movement of the input structure; and 
 
 a processing unit configured to determine a value of the force input from the movement of the input structure. 
 
     
     
       9. The input device of  claim 8 , wherein:
 the input structure is configured to tilt within the housing; 
 the sensor is configured to detect the tilt; and 
 the processing unit is further configured to determine a direction of the force input using the tilt. 
 
     
     
       10. The input device of  claim 8 , wherein:
 the sensor comprises a pair of electrodes, the pair of electrodes positioned within the housing and separated from one another; 
 the movement of the input structure changes a capacitance between the pair of electrodes; and 
 the sensor is configured to generate an output based on a change in the capacitance. 
 
     
     
       11. The input device of  claim 10 , wherein a first electrode of the pair of electrodes is positioned on the input structure, such that the first electrode moves with the input structure relative to a second electrode of the pair of electrodes. 
     
     
       12. The input device of  claim 11 , wherein:
 the input structure is a shaft having a longitudinal axis; 
 the input structure rotates about the longitudinal axis; and 
 the first electrode is a trackable element positioned on the shaft. 
 
     
     
       13. The input device of  claim 10 , wherein:
 the pair of electrodes are positioned on opposite sides of the housing; and 
 the input structure is positioned at least partially between the pair of electrodes. 
 
     
     
       14. The input device of  claim 8 , further comprising an enclosure; wherein
 the force sensor is at least partially within the enclosure; and 
 the force sensor is attached to the enclosure. 
 
     
     
       15. An input device, comprising:
 an enclosure defining an exterior surface; 
 an input structure at least partially extending into the enclosure and configured to move axially along a longitudinal axis of the input device and tilt relative to the longitudinal axis in response to a force input; 
 a compliant member connected to the input structure and configured to deform in response to the force input; and 
 a sensor configured to detect both movement along the longitudinal axis and tilt of the input structure relative to the longitudinal axis, wherein: 
 the input device is configured to transmit a signal to another electronic device that is derived from a value of at least one of the movement along the longitudinal axis or the tilt and an estimated deformation of the compliant member. 
 
     
     
       16. The input device of  claim 15 , wherein the signal indicates at least one of a value or a direction of the force input. 
     
     
       17. The input device of  claim 15 , wherein:
 the input device further comprises a housing positioned within the enclosure and at least partially surrounding the compliant member and the input structure; and 
 the compliant member is constrained by the housing. 
 
     
     
       18. The input device of  claim 17 , wherein the compliant member is an overmolded component positioned in an annulus between the housing and the input structure. 
     
     
       19. The input device of  claim 15 , wherein:
 the exterior surface is substantially cylindrical and surrounded by both the input structure and the compliant member; and 
 the exterior surface is configured to be grasped by a user.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/464,836, filed on Feb. 28, 2017 and titled “Force-Sensing Structures For An Input Device,” which is incorporated by reference as if fully disclosed herein. 
    
    
     FIELD 
     The described embodiments relate generally to force sensors for an input device. More specifically, the present disclosure is directed to estimating a force input based on movement of an input structure. 
     BACKGROUND 
     In computing systems, a force sensor may be employed to receive input from a user. Many traditional force sensors use a strain gauge to measure force based on a strain within a metal beam or bracket resulting from a force input, which may limit the accuracy and precision of the sensor. Non-symmetries in the metal beam, manufacturing tolerances, and/or off-axis deformations may impermissibly affect force measurements using such sensors, thereby limiting the functionality of the sensor to control an interconnected electronic device. 
     SUMMARY 
     One embodiment takes the form of an input device, comprising: an enclosure defining an interior volume; a force sensor at least partially positioned within the interior volume and comprising: a housing coupled to the enclosure; an input structure extending through the housing and out of the enclosure, the input structure configured to receive a force input; a compliant member coupled to the housing and the input structure; and a sensor positioned within the housing and configured to detect a value of a displacement of the input structure caused by the force input. 
     Another embodiment takes the form of an input device, comprising: a force sensor, comprising: a housing; an input structure at least partially surrounded by the housing and configured to receive a force input; a compliant member encircling the input structure within the housing and configured to deform in response to the force input, thereby controlling a movement of the input structure relative to the housing; and a sensor configured to detect the movement of the input structure; and a processing unit configured to determine a value of the force input from the movement of the input structure. 
     Yet another embodiment takes the form of an input device, comprising: an enclosure defining an exterior surface; an input structure at least partially extending into the enclosure and configured to move axially and tilt relative to the enclosure in response to a force input; a compliant member connected to the input structure and configured to deform in response to the force input; and a sensor configured to detect both axial movement and tilt of the input structure, wherein: the input device is configured to transmit a signal to another electronic device that is derived from a value of at least one of the axial movement or the tilt and an estimated deformation of the compliant member. 
     In addition to the example aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like elements. 
         FIG. 1  depicts a sample electronic device held by a user; 
         FIG. 2  depicts a stylus contacting an electronic device; 
         FIG. 3  depicts a stylus contacting a surface of an electronic device and showing force vectors exerted by the stylus on the surface; 
         FIG. 4  depicts one embodiment of a sample stylus; 
         FIG. 5A  depicts a simplified cutaway view of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 5B  depicts a simplified cutaway view of the stylus of  FIG. 4  in a second position, taken along line A-A of  FIG. 4 ; 
         FIG. 6A  depicts a cross-sectional view of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 6B  depicts an enlarged view of the force sensor of  FIG. 6A , taken at detail 1-1 of  FIG. 6A ; 
         FIG. 7A  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 7B  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 7C  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4  having offset elastic O-rings, taken along line A-A of  FIG. 4 ; 
         FIG. 8A  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 8B  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 8C  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 9A  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 9B  depicts a cross-sectional view of another embodiment of the stylus of  FIG. 4 , taken along line A-A of  FIG. 4 ; 
         FIG. 10A  depicts a simplified cutaway view of a sensor configuration of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 10B  depicts a simplified cutaway view of the sensor configuration of  FIG. 10A  in a second position, taken along line A-A of  FIG. 4 ; 
         FIG. 11A  depicts a simplified cutaway view of another sensor configuration of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 11B  depicts a simplified cutaway view of the sensor configuration of  FIG. 11A  in a second position, taken along line A-A of  FIG. 4 ; 
         FIG. 12A  depicts a simplified cutaway view of another sensor configuration of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 12B  depicts a simplified cutaway view of the sensor configuration of  FIG. 12A  in a second position, taken along line A-A of  FIG. 4 ; 
         FIG. 13A  depicts a simplified cutaway view of another sensor configuration of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 13B  depicts a simplified cutaway view of the sensor configuration of  FIG. 13A  in a second position, taken along line A-A of  FIG. 4 ; 
         FIG. 14A  depicts a simplified cutaway view of another sensor configuration of the stylus of  FIG. 4  in a first position, taken along line A-A of  FIG. 4 ; 
         FIG. 14B  depicts a simplified cutaway view of the sensor configuration of  FIG. 14A  in a second position, taken along line A-A of the stylus of  FIG. 4 ; 
         FIG. 15A  depicts a sample electronic device having a force sensor; 
         FIG. 15B  depicts a cross-sectional view of the electronic device of  FIG. 15A , taken along line B-B of  FIG. 15A ; 
         FIG. 16A  depicts another sample electronic device having a force sensor; 
         FIG. 16B  depicts a cross-sectional view of the electronic device of  FIG. 16A , taken along line C-C of  FIG. 16A ; and 
         FIG. 17  illustrates a functional block diagram of a system including an input device and an interconnected electronic device. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented therebetween, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     The description that follows includes sample systems, methods, and apparatuses that embody various elements of the present disclosure. However, it should be understood that the described disclosure may be practiced in a variety of forms in addition to those described herein. 
     The present disclosure describes systems, devices, and techniques related to force sensors for an input device. A force sensor may be used with any appropriate input device that is configured to receive user input, including, but not limited to, portable computing devices, wearable devices, phones, or the like. The force sensor may form, or be a component of, an input structure of the input device, such as a stylus, keyboard, trackpad, touch screen, three-dimensional input systems (e.g., virtual or augmented reality input systems), or other corresponding input structure. The force sensor may be used to detect a force input of an associated input structure, including detecting a value such as duration, magnitude, and/or direction, of the force input. A processing unit of the electronic device may use the detected force input to control a function of the electronic device. 
     In one embodiment, the force sensor is configured to detect a force input by measuring a displacement of one or more components/input structures of the force sensor. For example, the force sensor may include a mass, driver, or other appropriate input structure configured to receive a force input from a user. The input structure may be at least partially positioned within an opening of a sleeve, shaft, casing, or other housing structure of the electronic device. A deformable component, including a compliant member, tuning member, or other elastic structure may separate and be coupled with the input structure and the housing within the opening. This may control the input structure&#39;s movement relative to the housing in response to the force input. 
     The compliant member may contact, abut, or otherwise couple with both the input structure and the housing. For example, the compliant member may be received by or engaged along a surface of the input structure and sidewalls of the housing within the opening. As such, the housing may constrain an outer portion of the compliant member, while the input structure constrains an inner portion of the compliant member. The compliant member may deform (e.g., locally elongate, compress, or the like) between the housing and the input structure as the input structure moves within the opening of the housing in response to the force input. As such, the force required to move the input structure may be at least partially dependent on (or vary with) the force required to deform the compliant member over a range of distances. In this regard, the compliant member may be used within the force sensor to at least partially control or impede movement of the input structure, such as axial movement along a longitudinal axis of the housing. Movement of the input structure may thus be indicative of a force input exerted on the input structure (e.g., including a duration, magnitude and/or direction of the force input, due to the engagement of the input structure with the compliant member). 
     The force sensor may therefore measure movement of the input structure to detect, estimate, correlate or otherwise determine the force input exerted on the input structure, and analyze the characteristics related thereto. For example, the force sensor may include, or be integrated or coupled with, a sensor configured to measure displacement. The sensor may be a displacement sensor that measures axial movement (axial translation) and/or rotational movement of the input structure. The displacement sensor may also be configured to measure off-axis translation of the input structure (e.g., a tilt or angular offset of the input structure produced by an off-axis force), according to the embodiments described herein. 
     A processing unit (which may take the form of, or include, control logic circuitry) integrated within, or coupled to, the force sensor may estimate the force input received at the input structure using the detected motion or displacement of the input structure and a characteristic of the compliant member. For example, the compliant member may operate according to a spring characteristic, which may control the amount the compliant member generally deforms in response to a force input (e.g., due to physical characteristics of the compliant member). The spring characteristic may correspond generally to the spring constant “k” as represented in the Hooke&#39;s law equation: F=kx. The relationship between the displacement of the complaint member and the force input may thus be represented by a force-displacement curve, which depicts a force required to displace or deform the complaint member by a set amount. As described herein, the input structure may be constrained within the opening of the housing by the compliant member. As such, the compliant member may deform in response to movements (including axial movement, tilt, rotational movements, and so on) of the input structure, and thus the movements of the input structure may be measured to estimate a state of deformation of the compliant member. As the state of deformation of the compliant member is indicative of a predefined or expected force exerted on the compliant member, movements of the input structure may be used to determine forces acting on the compliant member. In turn, the force required to deform the compliant member may correspond to the force required to move the input structure over a range of predefined distances (e.g., due to the input structure being partially constrained by the input structure). Accordingly, the force sensor may use the estimate force acting on the compliant member to estimate forces acting on the input structure, for example, including a value such as a magnitude, duration, and/or direction, of a force input acting on the input structure, as described herein. 
     As described in greater detail below, the compliant member may be a tunable member that is constructed based on various material and geometric parameters. These parameters may allow the compliant member to exhibit certain predetermined properties or characteristics, including any or all of stiffness, elasticity, durability, and/or other similar or related properties. Accordingly, the spring characteristic of the compliant member may be determined by the construction of the compliant member. For example, the spring characteristic may be based on, at least in part, a characteristic of the compliant member, including: a width of the compliant member, a shape of the compliant member, a material of the compliant member, or a position of the compliant member along the input structure. The processing unit may thus have the particular characteristics of the compliant member to determine the force input exerted on the input structure. 
     To illustrate, the physical characteristics of the compliant member may influence or otherwise control a value (e.g., magnitude, duration, and/or direction) of movement of the input structure caused by the force input. For example, the magnitude and/or direction of the movement of the input structure may be proportional (or otherwise correlated or dependent upon) one or more of the physical characteristics of the compliant member. Such a relationship may be due to the constraint or engagement of the compliant member along the input structure and the housing, at least in some embodiments. Accordingly, the processing unit may determine a value (e.g., magnitude, duration, and/or direction) of a force input and by reference to a predefined force-displacement behavior of the input structure as determined or controlled by the compliant member. In turn, the processing unit may use the determined value (such as magnitude, direction, and/or duration) and/or other characteristic of the force input to control a function of an electronic device, as described herein. 
     The foregoing force sensor, force-sensitive assembly, or the like may be used in a variety of applications. As one example embodiment, the force sensor may be a component of a stylus (e.g., a marking tool, smart pen, smart brush, and/or other hand-held input device). The stylus may be used to control or manipulate an interconnected electronic device, such as a portable computing device or tablet. For example, a user may manipulate the stylus relative to an input surface of the interconnected electronic device to convey information to the electronic device, such as, but not limited to, writing, sketching, scrolling, gaming, selecting user interface elements, moving user interface elements, and so on. The force exerted by the stylus on the input surface of the electronic device may augment or provide additional information to the electronic device. As one example, when used for writing, a width of a line generated on the input surface may be dependent on the force exerted by the stylus. A graphical output of the input structure of the interconnected electronic device may therefore be manipulated in response to one or both of the determined magnitude or determined direction of the force input, both of which (together or separately) are example values of the force input. 
     In this regard, the force sensor, force-sensitive assembly, or the like described herein may be used within the stylus to detect one or more characteristics of a force exerted by the stylus on the input surface. For example, the input structure described herein may be a mass, driver, or tip at least partially extending from an enclosure that defines a body of the stylus. The enclosure may define, or be coupled with, a housing that surrounds a portion of the input structure. In operation, a user may press the input structure against the input surface of the electronic device, thereby generating a force input that causes the input structure to move relative to the body. 
     As described above, a compliant member may be positioned between the mass and the enclosure and configured to control the movement of the input structure caused by the force input. In a particular embodiment, the compliant member may be a set of O-rings encircling the input structure. The set of O-rings (or other elastic structure) may be silicone or other elastically deformable material. Each may be coupled to or engaged with the input structure and a housing positioned within an interior volume defined by the enclosure. A groove, notch, cut, or other engagement feature may be formed into one or both of the housing and/or the input structure and may receive a corresponding one of the set of O-rings. This may constrain an inner diameter of an O-ring at the input structure and an outer diameter of the O-ring at the housing. As such, movement of the input structure due to the force input may deform the O-rings between the housing and the input structure, and thereby control a range of motion exhibited by the input structure in response to a force input. For example, one or more mechanical or material properties of the O-rings may determine a magnitude of force required to deform the O-rings, which in turn, due to the constrained boundaries of the O-rings, may determine an amount of force required to displace the input structure over a range of distances. 
     The set of O-rings may be arranged along the mass in a variety of manners in order to control one or more characteristics of movement of the input structure resulting from the force input. For example, the set of O-rings may be a pair of two O-rings spaced apart on the input structure according to a predetermined separation distance. The axial and/or radial stiffness of the input structure may at least partially depend on the magnitude of the predetermined separation distance. Accordingly, the pair of O-rings may be positioned closer to, or further apart from, one another in order to control an axial and/or radial stiffness of the mass. In other cases, the set of O-rings may include three, four, or more O-rings arranged in various positions along the input structure, including configurations in which some of the set of O-rings abut one another, while others of the set of O-rings are spaced apart from the abutting O-rings, as may be appropriate for a given application. 
     It will be appreciated that various other compliant members, including compliant members of various materials, shapes, and/or sizes, may be used with the present invention, as described herein. For example, the compliant member may be a deformable or elastic structure, such as a cylinder or sleeve, encompassing a portion of the mass that is positioned within the stylus body. The deformable elastic structure may be a silicone insert that is molded or formed into a gap between the mass and the housing, for example, such as via an overmolding process. As such, substantially analogous to the set of O-rings, the deformable elastic structure may be constrained by the housing and the input structure (e.g., due to engagement with respective surfaces of each) and control movement of the mass resulting from the force input. In other cases, the compliant member may include one or both of the O-rings and the insert molded silicone elastic structure, as described herein. For example, a pair of O-rings may be positioned around, and spaced apart on, the mass, and the insert molded silicone elastic structure may be formed around the mass between the spaced apart O-rings. 
     The stylus may include various sensors that are configured to measure movement of the mass. The sensor may be any appropriate sensor that can measure one or more of axial translation, rotation, and/or off-axis translation or tilt of the mass, including a magnetic or Hall Effect sensor, a capacitive-based sensor, an optical sensor, or the like. In this regard, broadly, the sensor may be configured to measure a magnitude of a displacement of the input structure as the input structure moves relative to the stylus body. This may be accomplished in a variety of manners based on the displacement sensor used. As one illustration, the displacement sensor may be a capacitive-based sensor that measures a change in capacitance between two electrodes to determine a displacement or separation between the electrodes; the set of electrodes is one example of a sensor. As such, each of the stylus body and the mass may have one of such electrodes, and the sensor may determine a displacement of the mass as the capacitance between the electrodes varies based on movements of the mass. Additionally or alternatively, each of the electrodes may be positioned on opposing internal surfaces of the body (e.g., positioned on either side of the input structure) and the sensor may determine displacement of the mass as the capacitance between the electrodes varies based on movement of the mass (e.g., the mass may alter a dielectric characteristic between the electrodes as the mass moves). 
     In other embodiments, different sensors and techniques are contemplated and described in greater detail below. As one example, the sensor may be an optical sensor or encoder. The input structure may be coupled with, or define, various trackable elements (e.g., indicia, grooves, and so on) and the stylus may include an optical reader that measures the radial displacement or rotation of the mass using the trackable elements. The compliant member may also constrain or otherwise control radial displacement of the input structure. In this regard, the measured radial displacement may be used to measure a force input associated with the radial displacement of the mass according to the techniques described herein. 
     In some cases, the sensor may measure a magnitude of a displacement of multiple discrete portions of the mass as the mass moves relative to the stylus body. This may allow the force sensor to determine an orientation or direction of the force input (e.g., including estimating a magnitude of off-axis force received at the input structure). For example, an off-axis force received at the input structure may cause a distinct or different displacement at each of the multiple discrete portions of the input structure, because the off-axis force may tilt or angularly displace the input structure within the stylus body. By measuring the displacement at three or more of such portions, a processing element coupled with the stylus may approximate a force vector received at the input structure that causes the resulting tilt or angular displacement of the input structure. In other configurations, other sensors are contemplated to measure the tilt or off-axis force received at the input structure. The tilt of the input structure may be used to provide additional input to an electronic device using the stylus. 
     In other embodiments, the force sensor, force-sensitive assembly, or the like may be used as a component of a wearable electronic device, such as a watch. As one example, the input structure of the force sensor described herein may be defined by a crown connected with a mass or coupling extending into a watch body. A compliant member or other elastically deformable component may be positioned between the input structure and the watch body and configured to control or impede movement of the crown resulting from a user input. In this manner, a processing unit of the watch, analogous to that described above, may determine various characteristics of the force input using a detected displacement of the mass and various predetermined characteristics (e.g., such as elasticity) of the tuning member. 
     Accordingly, the input structure may be used to receive rotational and translational input from a user to control a function of the watch. The input structure extending into the watch body may be translatable and/or rotatable according to a or spring characteristic of the compliant members engaged with, and positioned between, the input structure and watch body. This may allow a processing unit (or other processing element) of the watch to detect, estimate, or otherwise determine a force associated with, or responsible for, a translational and/or rotational movement of the input structure. In turn, the processing unit may control a function of the watch based on an estimated value, such as magnitude, direction, duration, and/or type (e.g., translation or rotational) of the force input. For example, the processing unit may alter a display of the watch in a first manner based on detecting a predetermined value of a force input causing translational movement of the input structure and alter the display in a second manner based on determining a predetermined magnitude of a force input causing rotational movement of the input structure. 
     In another embodiment, the force sensor, force-sensitive assembly, or the like may be used as an input structure (for example, a button, key, switch, or the like) of an electronic device. The input structure of an electronic device may be configured to control an electronic device at least in part on a force input received from a user. In this regard, the input structure of the force sensor described above may be a key cap or other input surface. Such a key cap may be positioned above a substantially rigid substrate or housing. A compliant member may be positioned between the key cap and the housing, and configured to deform in response to a force input received at the key cap. In one embodiment, the compliant member may couple with the key cap around an outer periphery of the key cap and define a through portion. 
     In this regard, the compliant member may control or impede displacement of the key cap caused by the force input. A processing unit of the electronic device, analogous to that described above, may therefore measure a characteristic of the received force input (e.g., including a value, such as magnitude, duration, and/or direction of the force input) using a measured displacement of the key cap and a characteristic of the compliant member. The electronic device may include various sensors to measure the displacement of the key cap, including magnetic, optical, capacitive-based sensors, and so on. In some cases, this may allow the electronic device to employ an input structure, such as a keyboard, that may be substantially free of mechanically actuated switch mechanisms. 
     It will be appreciated that the force sensor, force-sensitive assembly, or the like described herein may be used with various other electronic devices. Without limitation, this may include substantially stationary electronic devices (e.g., including desktop computers, kiosks, terminals, or the like), portable or wearable electronic devices (e.g., including laptops, tablets, watches, glasses, rings, or the like), health monitoring devices, and/or other electronic devices. In this regard, the force sensor described herein may include any appropriate embodiment, configuration, or operation of an input structure. For example, the input structure may be substantially any structure configured to move at least partially based on a characteristic of a compliant or elastic structure connected therewith. This may allow a force sensor to measure a characteristic of a corresponding force input using the movement of the given input structure. 
     Reference will now be made to the accompanying drawings, which assist in illustrating various features of the present disclosure. The following description is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the inventive aspects to the forms disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present inventive aspects. 
       FIG. 1  depicts an electronic device  100  held by a user  104 . The electronic device  100  may include or be used with a force sensor, such as the force sensors generally discussed above and described in greater detail below. Electronic device  100  is illustrated as a tablet computing device, but it should be appreciated that any suitable electronic device may be used in or with various embodiments, including a mobile phone, wearable computing device (such as a watch, glasses, jewelry, a band, or the like), a laptop or other portable computer, a display, a touch-sensitive surface, and so on. For purposes of illustration,  FIG. 1  depicts the electronic device  100  as including an enclosure  108 , a touch-sensitive surface  112 , and one or more input/output members  116 . It should be noted that the electronic device  100  may also include various other components, such as one or more ports (e.g., a charging port, a data transfer portion, or the like), communications elements, additional input/output members (including buttons, and so on). As such, the discussion of any electronic device, such as electronic device  100 , is meant to be illustrative only and not limiting to the particular device discussed or illustrated. 
       FIG. 2  depicts the electronic device  100  with an input device  120  contacting the touch-sensitive surface  112 . The input device  120  may be used to provide input to the electronic device  100 , for example, through interaction with the touch-sensitive surface  112 . As such, a user may manipulate an orientation and position of the input device  120  relative to the touch-sensitive surface  112  to convey information to the electronic device  100  such as, but not limited to, writing, sketching, scrolling, gaming, selecting user interface elements, moving user interface elements, and so on. The input device  120  may therefore be configured to be grasped or held by a user for manipulation relative to the touch-sensitive surface  112 . The touch-sensitive surface  112  may be a multi-touch display screen or a non-display input surface (e.g., such as a trackpad or drawing tablet) as may be appropriate for a given application. 
     The input device  120  may convey information to the electronic device  100 , and the input device  120  may provide an output, at least partially based on the force exerted on the touch-sensitive surface  112 . As one example, a width of a line generated on the touch-sensitive surface  112  may be dependent upon a magnitude or relative degree of force exerted by the input device  120  on the touch-sensitive surface  112 . In such example, as the user  104  presses the input device  120  into the touch-sensitive surface  112  with greater force, the touch-sensitive surface  112  may depict a wider line. Correspondingly, under a lesser force, the touch-sensitive surface  112  may depict a narrower line. In this regard, as described herein, the input device  120  may include a force sensor that is configured to measure force applied to the input device  120  (e.g., such as that generated by the user  104  pressing the input device  120  against the touch-sensitive surface  112 ) in order to provide information to the electronic device  100  regarding the applied force. 
     The input device  120  may also convey information to the electronic device  100 , and the input device  120  may provide an output, at least partially based on a direction or orientation of force exerted on the touch-sensitive surface  112  by the input device  120 . For example, a width of a line generated on the touch-sensitive surface  112  may be dependent upon the angle at which the user  104  holds the input device  120 . As one possibility, as the user  104  raises the input device  120  to a perpendicular orientation with respect to the electronic device  100 , the touch sensitive-surface  112  may depict a narrower line. Correspondingly, as the angle of the input device  120  decreases with respect to the electronic device  100 , the touch-sensitive surface  112  may depict a thicker line. In this regard, as described herein, the input device  120  may include a force sensor that is configured to measure the orientation or direction of force applied to the input device  120  in order to provide information to the electronic device  100  regarding applied force. It should be appreciated that these are examples of how magnitude and direction/orientation of an applied force may be used to convey information and/or provide an output, and are not intended as limitations. 
       FIG. 3  depicts the input device  120  contacting the touch-sensitive surface  112 . The input device  120  is shown positioned at an angle θ from an axis  114 , which is perpendicular to the touch-sensitive surface  112 . In certain embodiments, the input device  120  may detect force (Fn) exerted axially with respect to a tip  122  of the input device  120  (e.g., along vector Fn), parallel to a longitudinal axis of the input device  120 . However, as shown in  FIG. 3 , additional force components (Ft and Fs) may also be exerted on the tip  122 . In this regard, the tip  122  may be a contact region of the input device  120  that is used to receive a force input. According to embodiments described herein, the input device  120  may include a force sensor that is configured to measure each of the force components exerted on the input device  120 , and/or the overall force Fn. As explained in greater detail below with respect to  FIGS. 5A-6B , the force sensor of the input device  120  may measure the respective force components using detected movements of the tip  122  (axial movement, tilt, rotation movement, and so on) and a characteristic of a compliant member coupled with the tip  122  and an internal surface of the input device  120 . Further, a rotational angle ϕ may also be measured using the force sensor described herein. As one example, the three-dimensional force vectors Fn, Ft, and Fs determined by the force sensor may be used to measure the rotational angle ϕ. 
       FIG. 4  generally shows the input device  120  having a long, narrow, or elongated body or enclosure  124  coupled to the tip  122  (although the exact shape of the stylus may widely vary). The enclosure  124  may extend along a longitudinal direction defining a stylus body or other structure having an exterior surface that is configured for manipulation by a user as a writing implement. For example, the exterior surface of the enclosure  124  may be a hoop, shell, or other substantially cylindrical structure that may be gripped by a user in order to use the input device  120  as a writing instrument. The tip  122  may be configured to move relative to the enclosure  124  in response to a force input F; such motion is allowed or facilitated by deformation of a compliant member as discussed below in more detail with respect to  FIGS. 5A-5B . The force input F may be exerted on the tip  122  in response to the user  104  pressing the input device  120  against the touch-sensitive surface  112 , as depicted with respect to  FIG. 2 . 
       FIG. 5A  is a simplified cutaway view of the input device  120  of  FIG. 4 , taken along line A-A of  FIG. 4  and through the housing to expose an input structure  152 . As shown, the input device  120  includes a force sensor  150  or other force-sensitive assembly configured to measure or estimate a force input. The force sensor  150  may measure a force input received at the tip  122  (not shown in  FIG. 5 ) to provide input to an interconnected electronic device (e.g., electronic device  100  of  FIG. 1 ). In particular, the force sensor  150  may measure force input received at the tip  122  by detecting movements of the input structure  152 . The movement may be an axial movement, such as substantially along a longitudinal axis of the enclosure  124 . Additionally or alternatively, the movement may be a tilt, in which the input structure  152  moves at least partially off axis from the longitudinal axis. As described in greater detail below, a force required to move the input structure  152  may depend upon characteristics of a compliant member engaged with the input structure  152  within the force sensor  150 . This may allow the input structure  152  to move according to a predefined force-displacement curve when impacted by a force input. The force sensor  150  may thus estimate a force exerted on the tip  122  using measured movement of the input structure  152  and the physical characteristics of the compliant member. 
     In this regard, the force sensor  150  may include the input structure  152 . The input structure  152  may be a shaft, driver, mass, beam or other component connected, or integrally formed with, the tip  122 . For example, the input structure  152  may be an end portion of the tip  122  that extends into the enclosure  124 . The input structure  152  may be a substantially rigid component that moves correspondingly with movement of the tip  122  that results from force received at the tip  122 . For example, the input structure  152  may extend out and move relative to the enclosure  124 . 
     The input structure  152  may be positioned within an interior volume of the enclosure  124  and configured to move relative thereto. The force sensor  150  may include a sleeve, shaft, casing, or other structure that defines an opening within the interior volume of the enclosure  124  that is configured to receive the input structure  152 , for example, such as housing  154  depicted in  FIG. 5A . As such, as shown in  FIG. 5A , the input structure  152  may extend through (or partially through) the opening of the housing  154  and away from the enclosure  124 . The housing  154  may be coupled with, or an integrally formed component of, the enclosure  124 . The housing  154  may be a relatively stationary or fixed component within the interior volume of the enclosure  124 . This may control the input structure&#39;s  152  movement relative to the housing  154  and/or the enclosure  124 . 
     The force sensor  150  may also include a deformable component coupled to the input structure  152  and the housing  154  and/or enclosure  124 . As shown in  FIG. 5A , the force sensor  150  may include a compliant member  156  positioned or otherwise interposed between the input structure  152  and the housing  154 , thereby defining an annulus between the housing  154  and the compliant member  156 . The compliant member  156  may be any structure that elastically deforms (e.g., locally elongates or compresses) in response to an applied force. In this regard, the compliant member  156  may be constructed at least partially from a silicone or silicone-based material; however, in other embodiments, other materials are contemplated. 
     The compliant member  156  may be connected to the input structure  152  and the housing  154  and/or enclosure  124  such that the compliant member  156  is affixed or otherwise constrained by the input structure  152  and the housing  154  and/or enclosure  124 . As such, movement of the input structure  152  resulting from the force received at the tip  122  may cause the compliant member  156  to deform between the input structure  152  and the housing  154  and/or enclosure  124 . This may cause the compliant member  156  to allow, impede, resist, or otherwise control movement of the input structure  152  relative to the housing  154  and/or enclosure  124 , according to one or more physical characteristics of the compliant member  156 . For example, the physical characteristics of the compliant member  156  may define the amount of force required to deform the compliant member  156  over a range of distances. Due in part to the coupling of the compliant member  156  with the input structure  152  and the housing  154 , an amount of force required to move the input structure  152  relative to the housing  152  and/or enclosure  124  may be the same as, or correspond or correlate with, the amount of force required to deform the compliant member  156 . This may allow the force sensor  150  to measure a displacement of the input structure  152  to determine a force input received by the input device  120 . For example, due to the predetermined characteristics of the compliant member  156 , the force sensor  150  may estimate a value (e.g., magnitude and/or direction) of a force input that would produce a resulting displacement of the input structure  152 . 
     To facilitate the foregoing, the force sensor  150  may include, or be coupled with, a sensor  170 . As described in greater detail below, the sensor  170  may be any of a variety of sensors that are configured to detect movement or translation of an object, including, but not limited to, magnetic or hall effect sensors, optical sensors, capacitive-based sensors, resistive sensors, or the like. As shown in  FIG. 5A , the sensor  170  may include first and second electrodes  172   a ,  172   b  (which collectively form the sensor  170 ) positioned within the interior volume of the enclosure  124  and about the input structure  152 . In one embodiment, the first and second electrodes  172   a ,  172   b  may be electrodes of a capacitive-based sensor positioned along an interior surface  125  of the enclosure  124  and the input structure  152 , respectively. The first and second electrodes  172   a ,  172   b  may be communicatively coupled to one another such that, as the input structure  152  moves, a capacitance between the first and second electrodes  172   a ,  172   b  may change. This change in capacitance may be indicative of a distance D separating the first and second electrodes  172   a ,  172   b , and therefore may be used to measure axial movement of the input structure  152  relative to the housing  154  and/or enclosure  124 . Put another way, as the input structure  152  moves axially in response to an input force F, the distance D shrinks. If the input force F ceases, the distance D returns to its default value. It should be appreciated that the input structure  152  may extend further along or into the enclosure  124  than is illustrated in  FIGS. 5A and 5B , in certain embodiments. Thus, the sensor  170  may be located at substantially any point along the shaft of the input device  120 . 
     In turn, a processing unit (not shown in  FIG. 5A ) integrated with, or coupled to, the force sensor  150  may use the measured movement of the input structure  152  to estimate a force input received along the tip  122 . In particular, the processing unit may use information relating to the physical characteristics of the compliant member  156  to correlate or associate the detected movement of the input structure  152  with an expected force input received by the input structure  152 . For example, the processing unit may use a value of the distance D measured by the sensor  170  to determine a value or magnitude of deformation of the compliant member  156  (e.g., due to the compliant member  156  being constrained by the input structure  152  and the housing  154  as the input structure  152  moves). In turn, the processing element may estimate a force exerted on the compliant member  156  that resulted in the particular magnitude of deformation of the compliant member  156  (e.g., due to the physical characteristics of the compliant member  156  defining an amount of force required to deform the compliant member  156 ). The processing element may use the force associated with the deformation of the compliant member  156  to estimate a magnitude or direction of force being exerted on the input structure  152 . For example, the compliant member  156  may be one of a set of compliant members and the processing element may use a force associated with the deformation of each of the compliant members to determine a three-dimensional force vector being exerted on the input structure  152 . 
     The input structure  152  is shown in  FIG. 5A  in a first or neutral position. In this regard, the distance D shown in  FIG. 5A  may correspond to a distance between the input structure  152  and the interior surface  125  of the enclosure  124  in a state in which no force, or a negligible amount of force, is being exerted on the input structure  152 . As such, the compliant member  156  depicted in  FIG. 5A  may be substantially undeformed. 
       FIG. 5B  is a simplified cutaway view of the input device  120  of  FIG. 4 , taken along line A-A of  FIG. 4  in a fashion similar to  FIG. 5A . In  FIG. 5B , the input structure  152  is shown in a second or force-loaded position (e.g., a position in which force input F is being exerted on the tip  122 , for example, along a z-axis). In the second position, the input structure  152  may be closer to the interior surface  125  than in the first position (e.g., the distance D depicted in  FIG. 5A  may be greater than a distance D′ depicted in  FIG. 5B ). The movement of the input structure  152  may cause the compliant member  156  depicted in  FIG. 5B  to be substantially deformed according to a spring characteristic. As described above and depicted in  FIG. 5B , the state of deformation of the compliant member  156  may be indicative of a force exerted on the input structure  152 . A processing unit coupled with the force sensor  150  may therefore estimate the force exerted on the input structure  152  by measuring the distance D′ (which corresponds or otherwise relates to the deformation of the compliant member  156 ). 
     The magnitude of the deformation of the compliant member  156  may be at least partially dependent on the physical characteristics (e.g., elasticity, size, shape, or the like) of the compliant member  156 . In this regard, the compliant member  156  may be a tunable member that is selectively constructible to achieve a particular relationship between the amount of force required to deform the compliant member  156  over a range of distances and thereby forming the predefined force-displacement curve. The processing unit may therefore be configured to identify the amount of force required to deform the compliant member  156  based on the predetermined physical characteristics of the compliant member  156 . This may also allow the force sensor  150  to employ various different compliant members based on a desired feedback or response of the input structure  152  to a force input. For example, a compliant member  156  may be used in the force sensor  150  having a higher or lower degree of elasticity depending on a desired sensitivity of the force sensor. 
       FIG. 6A  is a cross-sectional view of the input device  120  of  FIG. 4 , taken along line A-A of  FIG. 4 .  FIG. 6A  depicts a sample embodiment of the force sensor  150  described with respect to  FIGS. 5A and 5B . As shown, the force sensor  150  includes the input structure  152 , the housing  154 , and the compliant member  158   a.    
     In the embodiment of  FIG. 6A , the compliant member  158   a  may take the form of one or more O-rings. The O-ring(s)  158   a  (or other elastic structure) may be positioned around the input structure  152  and may be coupled with each of the input structure  152  and the housing  154 . The input structure  152  and the housing  154  include an engagement surface that receives or connects to a portion of the O-ring(s)  158   a . This may cause the O-ring(s)  158   a  to be constrained by the input structure  152  and the housing  154 . In particular, the input structure  152  may include an engagement surface that constrains an inner diameter of the O-ring(s)  158   a , and the housing  154  may include an engagement surface that constrains an outer diameter of the O-ring(s)  158   a . The constraint of the O-ring(s)  158   a  at the engagement surfaces of the input structure  152  and the housing  154  may cause the O-ring(s)  158   a  to deform in response to movement of the input structure  152 . In turn, the movement of the input structure  152  may be allowed, impeded or otherwise controlled by physical characteristics of the O-ring(s)  158   a  (e.g., the input structure  152  may move over a range of predefined distances based on the force required to deform the O-ring(s)  158   a  over a corresponding distance). 
     In the embodiment of  FIG. 6A , the input structure  152  and the housing  154  may include grooves  160 . The grooves  160  may be notches, cuts, debossed features, or other structures formed into, or coupled with, surfaces of the input structure  152  and the housing  154 . A corresponding pair of the grooves  160  may be configured to receive one of the O-rings  158   a . For example, a first groove  160   a  formed into the surface of the housing  154  may receive a portion of one of the O-rings  158   a , and a second groove  160   b  formed into the surface of the input structure  152  may receive another portion of the O-rings  158   a  opposite the first groove  160   a  on the housing  154 . Accordingly, the first and second grooves  160   a ,  160   b  may be aligned within the opening in order to receive a particular one of the O-rings  158   a . Multiple other O-rings  158  may be engaged with other corresponding pairs of grooves  160  in an analogous manner. The receipt by the respective grooves  160  may constrain the O-rings  158   a  between the input structure  152  and the housing  154  and/or the enclosure  124 , as described above. 
     The constraint of the O-rings  158   a  between the input structure  152  and the housing  154  may substantially control or set the amount of force required to move the input structure  152 . To illustrate, the first and second grooves  160   a ,  160   b  may maintain engagement with the O-rings  158   a  during movement of the input structure  152 . For example, the O-rings  158   a  may be continually received by or coupled with the first and second grooves  160   a ,  160   b  during movement of the input structure  152 . As such, the O-rings  158   a  may be deformed between the input structure  152  and the housing  154  and/or the enclosure  124  in response to movement of the input structure  152 . Movement of the input structure  152  thus occurs in response to a force sufficient to deform the O-rings  158   a.    
     As shown in  FIG. 6A , the O-rings  158   a  may be spaced apart or separated along the input structure  152  by an offset distance  190 . The offset distance  190  may control an axial and/or radial stiffness of the input structure  152 . As one possibility, the offset distance  190  may control a magnitude of force required to the input structure  152  longitudinally from a base or concentric position within the opening defined by the housing  154 . In the embodiment of  FIG. 6A , the offset distance  190  may correspond to a relatively wide separation of the O-rings  158   a  along the input structure  152 . This may correspond to each of the O-rings  158   a  being positioned on, or proximal to, opposing ends of the housing  154 . In other embodiments, other separation distances and configurations are possible and described in greater detail below with respect to  FIGS. 7A-7C . 
       FIG. 6B  depicts detail 1-1 of  FIG. 6A  of the force sensor  150 . As shown in the non-limiting example of  FIG. 6B , the force sensor  150  is shown in a state in which one of the O-rings  158   a  is received by the first and second grooves  160   a ,  160   b . The first and second grooves  160   a ,  160   b  depicted in  FIG. 6B  may each receive a portion of one of the O-rings  158   a , such as O-ring  158   a  depicted in  FIG. 6B . For example, an outer diameter portion  159   a  of the O-ring  158   a  may be received by the first groove  160   a  formed into the housing  154  and an inner diameter portion  159   b  of the O-ring  158   a  may be received by the second groove  160   b  formed into the input structure  152 . As such, the first groove  160   a  into the housing  154  may constrain the outer diameter portion  159   a , while the second groove  160   b  formed into the input structure  152  may constrain the inner diameter portion  159   b . The constraint or engagement of the outer and inner diameter portions  159   a ,  159   b  may be maintained while the input structure  152  translates relative to the housing  154 . Accordingly, movement of the input structure  152  deforms the O-rings  158  between the first and second grooves  160   a ,  160   b . This, in turn, causes the force required to move the input structure  152  to at least partially depend on the force required to deform the O-rings  158 . Put another way, the O-rings control the input structure&#39;s movement relative to the enclosure and/or housing and also determine an amount of force required for such movement. It should be appreciated that the force necessary to move the input structure  152  relative to the housing  154  and/or enclosure  124  may vary with a distance moved. 
       FIGS. 7A-7C  depict cross-sectional views of alternate embodiments of the force sensor  150  of  FIGS. 6A and 6B , taken along line A-A of  FIG. 4 . In particular,  FIGS. 7A-7C  illustrate cross-sectional views of alternative embodiments of the O-rings  158 . For example, the O-rings  158  may be separated by distinct separation distances that may be configured to control an axial and/or radial stiffness of the input structure  152 , as shown in  FIGS. 7A-7C . 
     As illustrated in the embodiment of  FIG. 7A , the offset distance  190  between the O-rings  158  (or similar elastic structure) may correspond to a relatively moderate separation of the O-rings  158  along the input structure  152 . This may result in one of the O-rings  158  being positioned along, or proximal to, a middle region of the housing  154 , while another of the O-rings  158  is positioned along, or proximal to, an end region of the housing  154 . This may cause the input structure  152  to have an axial and/or radial stiffness that is distinct from the axial and/or radial stiffness of the input structure  152  depicted with respect to  FIG. 6A . For example, the input structure  152  depicted in  FIG. 7A  may have a lesser or greater axial and/or radial stiffness than the mass depicted with respect to  FIG. 6A . 
     As illustrated in the embodiment of  FIG. 7B , the offset distance  190  between the O-rings  158  may correspond to a relatively narrow separation of the O-rings  158  along the input structure  152 . This may result in two of the O-rings  158  being positioned along, or proximal to, an end region of the housing  154 . This may cause the input structure  152  to have an axial and/or radial stiffness that is distinct from the axial and/or radial stiffness of the input structure  152  depicted with respect to  FIG. 6A . For example, the input structure  152  depicted in  FIG. 7B  may have a lesser or greater axial and/or radial stiffness than the input structure  152  depicted with respect to  FIG. 6A . 
     As illustrated in the embodiment of  FIG. 7C , the O-rings  158  may include three, four, or more individual O-rings. In the configuration of  FIG. 7C , two of the O-rings  158  may be positioned along, or proximal to, an end region of the housing  154 , while a third of the O-rings  158  may be positioned along, or proximal to, an end region of the housing  154 . This may cause the input structure  152  to have an axial and/or radial stiffness that is distinct from the axial and/or radial stiffness of the input structure  152  depicted with respect to  FIG. 6A . For example, the input structure  152  depicted in  FIG. 7C  may have a lesser or greater axial and/or radial stiffness than the input structure  152  depicted with respect to  FIG. 6A . 
     Additionally or alternatively, the inclusion of additional O-rings in the embodiment of  FIGS. 7A-7C  may also alter the relationship between the amount of force required to move the input structure  152  over a range of distances. For example, the inclusion of additional O-rings may increase the amount of force required to move the input structure  152  as each additional O-ring may impede movement of the input structure  152 . Analogously, the abutment of two or more of the O-rings  158  may also contribute to altering the amount of force required to move the input structure  152 . In this manner, the force sensor  150  may include any appropriate amount or configuration of O-rings to control the amount of force required to move the input structure  152  relative to the housing  154  and/or the enclosure  124 . 
       FIGS. 8A-8C  illustrate various views of components of a force sensor  850  or other force-sensitive assembly, according to one or more embodiments of the present disclosure. The force sensor  850  shown and described with respect to  FIGS. 8A and 8B  may be substantially analogous to the force sensor  150  described above with respect to  FIGS. 1-7C . For example, the force sensor  850  may measure movement of an input structure, mass, driver, or the like in order to estimate a force input received along the input structure. In this regard, analogous to the components described in relation to the embodiments of  FIGS. 1-7C , the force sensor  850  may include: input structure  852 ; housing  854 ; and O-rings  858 . The O-rings  858  may be a deformable structure, compliant member, tuning member, elastic structure, or the like that deforms in response to translation of the input structure  852  relative to the housing  854  and/or enclosure  824 . 
     Notwithstanding the foregoing similarities, the force sensor  850  may include alternative embodiments of engagement surfaces that are configured to couple the O-rings  858  to the input structure  852  and the housing  854 . For example, the force sensor  850  may include various features or structures that constrain the O-rings  858  (or other compliant member) between the input structure  852  and the housing  854  and/or enclosure  824 , including, but not limited to, collars, brackets, projections, or the like positioned within an interior volume defined by the enclosure  824 . 
     As illustrated in the embodiment of  FIG. 8A , the O-rings  858  may be constrained between the input structure  852  and a bracket, projection, or other engagement structure coupled to, or integrally formed with, the housing  854 . In particular, the input structure  852  may include end portions  860  that define a reduced thickness region of the input structure  852 . The end portions  860  may be formed along opposing ends of the input structure  852 . The O-rings  858  may be positioned along the end portions  860 . When positioned along the end portions  860 , the O-rings  858  may have an outer diameter that is greater than a diameter of input structure  852 . This may allow the O-rings  858  to separate the input structure  852  from the housing  854  and/or enclosure  824  when the input structure  852  is positioned within the enclosure  824 . 
     An engagement structure  862  may be coupled with the housing  854  and/or the enclosure  824  within an interior volume defined by the enclosure  824 . As shown in  FIG. 8A , the engagement structure  862  may be a cylindrical collar, washer, or other structure that is positionable within the internal volume defined by the enclosure  824 . In an installed configuration, the engagement structure  862  may encircle the end portions  860  of the input structure  852 . This may allow the input structure  852  to be positioned within the housing  854  such that the O-rings  858  abut the engagement structure  862 . Accordingly, the O-rings  858  may be constrained by the engagement structure  862  and the end portions  860  of the input structure  852 . 
     As such, analogous to the embodiments described above, a processing element coupled with the force sensor  850  may estimate a force received along the input structure  852  by measuring displacement of the input structure  852 . For example, the O-rings  858  may deform in response to movement of the input structure  852 ; and the force required to deform the O-rings  858  may define or control a force required to move the input structure  852  over a corresponding range of distances. The O-rings  858  may define or control the force required to move the input structure  852  due to the O-rings  858  being constrained by the input structure  852  and the housing  854  and/or the enclosure  824 . 
     As illustrated in the embodiment of  FIG. 8B , the O-rings  858  may be constrained between a tapered portion of the input structure  852  and a correspondingly tapered portion of a bracket, projection, or other engagement structure coupled to, or integrally formed with, the housing  854  and/or the enclosure  824 . In the embodiment of  FIG. 8B , the input structure  852  may have end portions  860  that are tapered or conical. The O-rings  858  may be positioned around the end portions  860 . 
     An engagement structure  862  may be coupled with the housing  854  and/or the enclosure  824  and extend into an interior volume defined by the enclosure  824 . For example, the engagement structure  862  may be a pin or lug inserted into the interior volume defined by the enclosure  824 . The engagement structure  862  may have a tapered surface that matches a contour of the tapered surface defined by the end portions  860  of the input structure  852 . This may allow the tapered surface of the end portions  860  to be received by the tapered surface of the engagement structure  862 . 
     In an installed configuration, the O-rings  858  may be coupled with the end portions  860  and the engagement structure  862 . In particular, the O-rings  858  may be engaged with the tapered surface of the end portions  860  while being engaged with the tapered surface of the engagement structure  862 . In some cases, one or both of the engagement structure  862  and the end portions  860  may include or define a notch, cut, groove, or the like configured to receive the O-rings  858 . As shown in  FIG. 8B , notches  859  are formed into both the engagement structure  862  and the end portions  860  to constrain the O-rings  858  between the engagement structure  862  and the end portions  860 . 
     As such, analogous to the embodiments described above, a processing unit coupled with the force sensor  850  may determine a force exerted on the input structure  852  by measuring displacement of the input structure  852 . For example, the O-rings  858  may deform in response to movement of the input structure  852 ; and the force required to deform the O-rings  858  may define or control a force required to move the input structure  852  over a corresponding range of distances. The O-rings  858  may define or control the force required to move the input structure  852  due to the O-rings  858  being constrained by the input structure  852  and the housing  854  and/or the enclosure  824 . 
     As illustrated in the embodiment of  FIG. 8C , the O-rings  858  may be constrained between angled or tapered surfaces of the input structure  852  and the housing  854  and/or the enclosure  824 . For example, the input structure  852  may include end portions  860  that define an angled surface  898 . The O-rings  858  may be positioned around the input structure  852  such that the O-rings  858  contact or otherwise abut the angled surface  898 . Correspondingly, the housing  854  may define an angled surface  899  that may match a contour of the angled surface  898 . The input structure  852  may be positioned within an interior volume defined by the enclosure  824  such that the O-rings  858  contact or otherwise abut the angled surface  898  and the angled surface  899 . Accordingly, one portion of the O-rings  858  may be constrained at the angled surface  898  while another portion of the O-rings  858  may be constrained at the angled surface  899 , as the input structure  852  moves relative to the housing  854  and/or the enclosure  824 . 
     The slope, or other geometric characteristics of each of the angled surface  898  and the angled surface  899 , may be altered to control an amount of force required to move the input structure  852 . Additionally or alternatively, the slope may be altered to adjust the axial stiffness of the input structure  852  relative to the radial stiffness of the input structure  852 . As one example, as the slope of one or both of the angled surface  898  and/or the angled surface  899  increases, the axial stiffness of the input structure  852  relative to the radial stiffness of the input structure  852  may increase or decrease. 
     In some cases, the input structure  852  may be defined by first and second mass portions  852   a ,  852   b . The first and second mass portions  852   a ,  852   b  may be joined or coupled to one another via threaded connection  853 . For example, the second mass portion  852   b  may include a threaded fitting that is received by a correspondingly threaded receiving portion of the first mass portion  852   a . The first and second mass portions  852   a ,  852   b  may be coupled via the threaded connection  853  at a position within an internal volume defined by the enclosure  824 . Such assembly and connection may allow the end portions  860  of the input structure  852  to extend beyond, or be larger than, a diameter or other cross-dimension of the internal volume that is defined by the housing  854 . 
       FIGS. 9A and 9B  illustrate various views of components of a force sensor  950  or other force-sensitive assembly, according to one or more embodiments of the present disclosure. The force sensor  950  shown and described with respect to  FIGS. 9A and 9B  may be substantially analogous to the force sensor  150  described above with respect to  FIGS. 1-7C . For example, the force sensor  950  may measure movement of an input structure in order to estimate a force input exerted on the input structure. In this regard, analogous to the components described in relation to the embodiments of  FIGS. 1-7C , the force sensor  950  may include: input structure  952 ; and housing  954 . 
     Notwithstanding the foregoing similarities, the force sensor  950  may include a molded shell  980 . As illustrated in the embodiment of  FIG. 9A , the molded shell  980  may be molded or formed between the input structure  952  and the housing  954  and/or the enclosure  924 . As such, the molded shell  980  may be an overmolded component of the force sensor  950 . The molded shell  980  may be constructed from silicone or other appropriate elastically deformable material; however, in other embodiments, other materials are contemplated. In one embodiment, the molded shell  980  may be formed by injecting a liquid or melted material into an opening or gap between the input structure  952  and the housing  954  and/or the enclosure  924 . The liquid or melted material may subsequently cool within the gap and form the molded shell  980 . This may cause the molded shell  980  to contact, engage, or otherwise substantially be constrained by surfaces of the input structure  952  and the housing  954  and/or the enclosure  924 . 
     The input structure  952  may be configured to move relative to the housing  954  and/or the enclosure  924  in response to a force input. Analogous to the compliant members  156  described above with respect to  FIGS. 5A and 5B , the molded shell  980  may be configured to control the force required to move the input structure  952  over a range of distances, for example, due in part to the molded shell  980  being constrained by the input structure  952  and the housing  954  and/or the enclosure  924 . This may allow a processing element coupled with the force sensor  950  to determine a force exerted on the input structure  952  by measuring displacement of the input structure  952 . For example, the molded shell  980  may deform in response to movement of the input structure  952 ; and the force required to deform the molded shell  980  may define or control a force required to move the input structure  952  over a corresponding range of distances. 
     As illustrated in the embodiment of  FIG. 9B , the force sensor  950  may further include O-rings or other elastic structures  982 . Substantially analogous to the O-rings  158  described above with respect to  FIGS. 6A-7C , the elastic structures  982  may be configured to control the force required to move the input structure  952  over a range of distances, for example, due in part to the elastic structures  982  being constrained by the input structure  952  and the housing  954  and/or the enclosure  924 . As shown in  FIG. 9B , the elastic structures  982  may be positioned between the input structure  952  and the housing  954  at opposing ends of the molded shell  980 . Accordingly, both the elastic structures  982  and the molded shell  980  may operate to control the force required to move the input structure  952 , according to the embodiment of  FIG. 9B . 
     In the embodiment of  FIG. 9B , the force sensor  950  may include one or more assemblies or structures to bias the elastic structures  982  and/or the molded shell  980  into a state of compression. This may allow the elastic structures  982  and/or the molded shell  980  to be in a state of compression, or pre-loaded, prior to the receipt of a force input by the input structure  952 . This may be desirable in order to tune or otherwise modify an amount of force required to move the input structure  952 . For example, the amount of force required to move the mass over a range of distances may be different when the elastic structures  982  and/or molded shell  980  are in a compressed versus uncompressed state. Additionally or alternatively, compressing the elastic structures  982  and/or the molded shell  980  may modify an axial and/or radial stiffness of the input structure  952 . For example, the compression may increase or decrease the amount of force required to move the input structure  952  from a concentric position within the interior volume defined by the enclosure  924 . 
     To facilitate the foregoing, the input structure  952  may include a threaded portion  953 . The threaded portion  953  may be configured to receive a compression nut  986 . In one embodiment, a collar  984 , or other substantially rigid object, may be placed around the input structure  952  at the threaded portion  953 . The compression nut  986  may be adjusted on the threaded portion  953  in order to advance the collar  984  along a longitudinal axis of the input structure  952  (e.g., in a direction toward the elastic structures  982  and/or the molded shell  980 ). This may cause the elastic structures  982  and/or the molded shell  980  to compress between the collar  984  and an opposing end region  988  of the input structure  952 . 
     It will be appreciated that, in other embodiments, other configurations or orientations of the molded shell  980  and the elastic structures  982  are contemplated and within the scope of the present disclosure. For example, the molded shell  980  and/or the elastic structures  982  may be engaged with, or constrained by, surfaces of the input structure  952 , the housing  954 , and/or the enclosure  924  having different geometries. Possible geometries include convex, concave, symmetrical, and/or irregular shapes, among other combinations. Additionally or alternatively, the molded shell  980  and the elastic structures  982  need not be constructed from the same elastically deformable material. In some cases, it may be desirable to construct the molded shell  980  and the elastic structures  982  from materials having distinct properties, such as distinct elasticities, as may be appropriate for a given application. 
       FIGS. 10A-14B  illustrate various cutaway views of the input device  120 , taken along line A-A of  FIG. 4  and through the enclosure  124  to expose a force sensor  1050  or other appropriate force-sensitive assembly, according to one or more embodiments of the present disclosure. The force sensor  1050  shown and described with respect to  FIGS. 10A-14B  may be substantially analogous to the force sensor  150  described above with respect to  FIGS. 1-7C . For example, the force sensor  1050  may measure movement of an input structure in order to determine a force input exerted on the input structure. In this regard, analogous to the components described in relation to the embodiments of  FIGS. 1-7C , the force sensor  1050  may include: input structure  1052 ; housing  1054 ; and compliant member  1056 . The compliant member  1056  is omitted from  FIGS. 10A-14B  for purposes of clarity; however, it will be appreciated that the compliant member  1056  is positioned between, and constrained by, the input structure  1052  and the housing  1054  and/or the enclosure  124  and is deformable in response to movement of the input structure  1052 . In some embodiments, the housing  1054  is part of (e.g., integrally formed with) the enclosure  124  while in others it may be a separate piece, for example positioned within an interior volume defined by the enclosure  124 . 
     Notwithstanding the foregoing,  FIGS. 10A-14B  present alternate embodiments of a sensor  1070 . For example, the sensor  1070  depicted with respect to  FIGS. 10A-14B  may be configured to measure movement of the input structure  1052  using different sensors, techniques and/or structures, including techniques used to measure axial translation, rotation, and/or off-axis forces exerted on the input structure  1052 . It will be appreciated that in some cases multiple different embodiments of the foregoing sensing techniques may be used in any appropriate combination. In this regard, a force sensor of the present invention may include multiple numbers of the sensor  1070  described with respect to  FIGS. 10A-14B  to measure forces exerted on the input structure  1052 . For example, the sensor  1070  may include one or more of, or all of, a capacitive-based sensor, a magnetic sensor, and/or an optical sensor arranged in one or more of the configurations described with respect to  FIGS. 10A-14B . As such, any discussion of the sensor  1070  as being a capacitive-based sensor, a magnetic sensor, and/or an optical sensor is for purposes of illustration only. 
     As illustrated in the embodiment of  FIGS. 10A and 10B , the sensor  1070  may be configured to measure axial movement of the input structure  1052  (for example, along a z-axis of the input device  120  in response to an input force F) using first electrode  1072   a  and second electrode  1072   b . The second electrode  1072   b  may be a single electrode or a set of electrodes. As shown, the first electrode  1072   a  may be positioned along, or formed with, a surface of the housing  1054  and the second electrode  1072   b  may be positioned along, or formed with, a surface of the input structure  1052 . For example, the second electrode  1072   b  may be positioned along a side surface of the input structure  1052 . In one instance, the first and second electrodes  1072   a ,  1072   b  may be electrodes of a capacitive-based motion sensor. As the input structure  1052  moves, a capacitance between the first and at least one of the first or second electrodes  1072   a ,  1072   b  may change. This change in capacitance(s) may be indicative of a distance D that the input structure  1052  travels relative to, for example, the housing  1054  and/or the enclosure  124 . In other cases, the first and second electrodes  1072   a ,  1072   b  may be components of a magnetic or optical sensor that measures movement of the input structure  1052  based on a measured change in a magnetic characteristic or optical pattern, respectively. 
     By way of illustration,  FIG. 10A  depicts the input structure  1052  in a first position relative to the housing  1054  and  FIG. 10B  depicts the input structure  1052  in a second position relative to the housing  1054 . In this regard, the sensor  1070  may be configured to measure the motion of the input structure  1052  between the first and second positions. In particular, the sensor  1070  may measure a capacitance between the first and second electrodes  1072   a ,  1072   b  as the input structure  1052  moves between the first and second positions depicted in  FIGS. 10A and 10B , respectively. The capacitance measured between the first and second electrodes  1072   a ,  1072   b  may be different based on the input structure  1052  being in the first or second position. Accordingly, the sensor  1070  may measure the capacitance between the first and second electrodes  1072   a ,  1072   b  as being different when the input structure  1052  is in the second position. This capacitance may, in turn, be associated with a distance D′ that the input structure  1052  travels relative to, for example, the interior surface  125  of the enclosure. 
     As illustrated in the embodiment of  FIGS. 11A and 11B , the sensor  1070  may be configured to measure axial movement of the input structure  1052  using first and second electrodes  1072   a ,  1072   b  (for example, along a z-axis of the input device  120  in response to an input force F). As shown, the first and second electrodes  1072   a ,  1072   b  may be positioned along, or formed with, a surface of the housing  1054 . The first and second electrodes  1072   a ,  1072  may be positioned along the housing  1054  such that the input structure  1052  is positioned between the first and second electrodes  1072   a ,  1072   b . In one instance, the first and second electrodes  1072   a ,  1072   b  may be electrodes of a capacitive-based motion sensor. As the input structure  1052  moves, a capacitance between the first and second electrodes  1072   a ,  1072   b  may change. For example, the input structure  1052  may alter or disrupt a dielectric characteristic and/or other signal between the first and second electrodes  1072   a ,  1072   b . This disruption may cause a change in capacitance that may be indicative of a distance D that the input structure  1052  travels relative to, for example, the interior surface  125  of the enclosure  124 . As in the embodiments of  FIGS. 10A and 10B , the first and second electrodes  1072   a ,  1072   b  may be replaced by optical sensors, magnetic sensors, and so on. 
     By way of illustration,  FIG. 11A  depicts the input structure  1052  in a first position relative to the housing  1054  and  FIG. 11B  depicts the input structure  1052  in a second position relative to the housing  1054 . In this regard, the sensor  1070  may be configured to measure motion of the input structure  1052  between the first and second positions. In particular, the sensor  1070  may measure a capacitance between the first and second electrodes  1072   a ,  1072   b  as the input structure  1052  moves between the first and second positions depicted in  FIGS. 11A and 11B , respectively. The capacitance measured between the first and second electrodes  1072   a ,  1072   b  may be different based on the input structure  1052  being in the first or second position. Accordingly, the sensor  1070  may measure the capacitance between the first and second electrodes  1072   a ,  1072   b  as being different when the input structure  1052  is in the second position. This capacitance may, in turn, be associated with a distance D′ that the mass travels relative to, for example, the interior surface of the enclosure  124 . 
     As illustrated in the embodiment of  FIGS. 12A and 12B , the sensor  1070  may be configured to measure tilt or off-axis forces exerted on the input structure  1052  using the first and second electrodes  1072   a ,  1072   b  (for example, along one or more of a z-axis, y-axis, or x-axis of the input device  120  in response to an input force F). As shown, the first and second electrodes  1072   a ,  1072   b  may be positioned within the force sensor  1050  in a manner substantially analogous to that depicted in  FIGS. 11A and 11B . For example, the first and second electrodes  1072   a ,  1072   b  may be positioned along the housing  1054  such that the input structure  1052  is positioned between the first and second electrodes  1072   a ,  1072   b.    
     In one instance, the first and second electrodes  1072   a ,  1072   b  may be electrodes of a capacitive-based motion sensor. As the input structure  1052  moves, a capacitance between the first and second electrodes  1072   a ,  1072   b  may change. For example, the input structure  1052  may alter a dielectric characteristic between the first and second electrodes  1072   a ,  1072   b  that causes the change in capacitance. This change in capacitance may be indicative of an angular position θ between the input structure  1052  and the housing  1054  and/or the enclosure  124 . For example, the input structure  1052  may alter the capacitance measured between the first and second electrodes  1072   a ,  1072   b  based on the volume or extent of the input structure  1052  that is positioned between the first and second electrodes  1072   a ,  1072   b . This measurement of the capacitance between the first and second electrodes  1072   a ,  1072   b  may be used in conjunction with a measurement of the distance of the input structure  1052  from a reference point on the enclosure  124  (such as the interior surface  125 ) to estimate the tilt or orientation of the input structure  1052 . Stated differently, at a predefined distance from the interior surface  125 , the capacitance measured between the electrodes  1072   a ,  1072   b  may vary as a function of the angular offset θ. As in the embodiments of  FIGS. 10A and 10B , the electrodes  1072   a ,  1072   b  may be replaced by optical sensors, magnetic sensors, and so on. 
     By way of illustration,  FIG. 12A  depicts the input structure  1052  in a first position relative to the housing  1054  and  FIG. 12B  depicts the input structure  1052  in a second position relative to the housing  1054 . The first position of the input structure  1052  may have an angular position θ that is distinct from an angular position θ′ of the second position of the input structure  1052 . Each of the first and second positions of the input structure  1052  may be at a known distance D that is separating the input structure  1052  from the enclosure  124 . In this regard, the sensor  1070  may be configured to measure motion of the input structure  1052  between the first and second positions. In particular, the sensor  1070  may measure a capacitance between the first and second electrodes  1072   a ,  1072   b  as the input structure  1052  moves or tilts between the first and second positions (e.g., movement corresponding to an alteration of a magnitude of the angular position). The capacitance measured between the first and second electrodes  1072   a ,  1072   b  may be different based on the input structure  1052  being in the first or second position (e.g., because a different volume or amount of the input structure  1052  is positioned between the first and second electrodes  1072   a ,  1072   b ). Accordingly, the sensor  1070  may measure the capacitance between the first and second electrodes  1072   a ,  1072   b  as being different when the input structure  1052  is in the second position. This capacitance may, in turn, be associated with the angular offset θ′ of the input structure  1052  in the second position. 
     In the embodiment of  FIGS. 13A and 13B , the sensor  1070  may be configured to measure the tilt or off-axis force received at the input structure  1052  using the measured change in capacitance described above (for example, along one or more of a z-axis, y-axis, or x-axis of the input device  120  in response to an input force F). For example, as illustrated, the second electrode  1072   b , may be one of a group of second electrodes  1072   b  positioned on an end surface of the input structure  1052 . Each of the group of second electrodes  1072   a  may be positioned on a discrete portion of the input structure  1052 . The sensor  1070  may be configured to measure the respective change in capacitance between the first electrode  1072   a  and each of the group of second electrodes  1072   b . The respective change in capacitance between the first electrode  1072   a  and each of the group of second electrodes  1072   b  may correspond to a distance separating the first electrodes  1072   a  from each of the respective ones of the group of second electrodes  1072   b . These distances may be used by sensor  1070  to determine a three-dimensional orientation of the input structure  1052  (e.g., due to knowing at least the linear distance between the first electrode  1072   a  and three discrete regions on the input structure  1052 ). As in the embodiments of  FIGS. 10A and 10B , the electrodes  1072   a ,  1072   b  may be replaced by optical sensors, magnetic sensors, and so on. 
     The force sensor  1050  may use the detected three-dimensional orientation of the input structure  1052  (as measured by the sensor  1070 ) to determine a three-dimensional force vector being exerted on the input structure  1052 . For example, the compliant member may deform in three-dimensional space in response to a known or expected three-dimensional force vector. This may be based on the predetermined physical characteristics of the compliant member. As such, analogous to the techniques described above with respect to the force sensor  150  in  FIG. 5 , the force sensor  1050  may estimate a three-dimensional force vector received at the input structure  1052  that causes the resulting three-dimensional orientation of the input structure  1052  (e.g., based on the known or predefined force-displacement behavior of the compliant member that is constrained between the input structure  1052  and the housing  1054 ). 
     By way of illustration,  FIG. 13A  depicts the input structure  1052  in a first position relative to the housing  1054  and  FIG. 13B  depicts the input structure  1052  in a second position relative to the housing  1054 . A capacitance measured between each of the first electrode  1072   a  and the group of second electrodes  1072   b  may be different at the first position of the input structure  1052  (illustrated in  FIG. 13A ) than at the second position of the input structure  1052  (illustrated in  FIG. 13B ). This change in orientation may be associated with a change in an angular position of the input structure  1052  within the force sensor  1050 , for example, such as a change or alteration of a magnitude of an angular position θ′ that is defined between a longitudinal axis of the input structure  1052  and a longitudinal axis of an interior volume defined by the input structure  1052 . 
     As illustrated in the embodiment of  FIGS. 14A and 14B , the sensor  1070  may be configured to measure rotation of the input structure  1052  using the first and second electrodes  1072   a ,  1072   b . The rotation may be about a longitudinal axis of the input structure  1052  (e.g., such as a z-axis of the input structure  1052 ). As shown, the first electrode  1072   a  may be positioned on a portion of the housing  1054  and the second electrode  1072   b  may be a group of second electrodes  1072   b  positioned about or on a cylindrical surface of the input structure  1052 . Substantially analogous to the first and second electrodes  1072   a ,  1072   b  described above with respect to  FIGS. 5A and 5B , the first and second electrodes  1072   a ,  1072   b  may be electrodes of a capacitive-based sensor. In this regard, the sensor  1070  may detect a change in capacitance between the first electrodes  1072   a  and each of the group of second electrodes  1072   b  in order to determine rotational movement R of the input structure  1052  (e.g., about a longitudinal axis). As one possibility, the group of second electrodes  1072   b  may be spaced apart on the surface of the input structure  1052  such that as the input structure  1052  rotates, a capacitance measured generally between the first electrode  1072   a  and the group of second electrodes  1072   b  is momentarily changed or disrupted (e.g., as may occur when a gap or spacing between electrodes of the group of second electrodes  1072   b  substantially faces the first electrodes  1072   a ). In turn, the rate at which the capacitance changes may be correlated to the axial movement of the input structure  1052 . As in the embodiments of  FIGS. 10A and 10B , the first and second electrodes  1072   a ,  1072   b  may be replaced by optical sensors, magnetic sensors, and so on. 
     By way of illustration,  FIG. 14A  depicts the input structure  1052  in a first rotational position relative to the housing  1054  and  FIG. 14B  depicts the input structure  1052  in a second rotational position relative to the housing  1054 . A capacitance measured between each of the first electrode  1072   a  and each of the group of second electrodes  1072   b  may be different at the first position of the input structure  1052  (illustrated in  FIG. 14A ) than at the second position of the input structure  1052  (illustrated in  FIG. 14B ). This change or difference in capacitance may, in turn, be associated with the rotational movement R that the input structure  1052  travels relative to the housing  1054 . It should be appreciated that some embodiments may permit the enclosure  124  to rotate while the mass is stationary. 
       FIG. 15A  depicts an example electronic device  1500 . The electronic device  1500  may include a force sensor  1550  (not shown in  FIG. 15A ), such as the force sensors or force-sensitive assemblies discussed above and described in greater detail below. In this regard, the force sensor  1550  may be substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7B . As described with respect to  FIGS. 1 and 7B , the force sensor  1550  may be used in a variety of manners within the electronic device  1500 . For example, the force sensor  1550  may be configured to detect a force input at a button, crown, and/or other input surface of the electronic device  1500 . 
     As a non-limiting example, as shown in  FIG. 15A , the electronic device  1500  may be a wearable electronic device, such as a watch. However, it is understood that electronic device  1500  may be any suitable wearable electronic device that operates with the force sensor  1550 . Other examples of other wearable electronic devices may include watches of other configurations, glasses, rings, health monitoring devices (including pedometers, heart rate monitors, or the like), and other electronic devices. For purposes of illustration,  FIG. 15A  depicts the electronic device  1500  as including an enclosure  1512  (e.g., which may define a watch body); a display  1514 ; one or more input/output members  1516 ; a crown  1518 ; and a band  1520 . It should be noted that the electronic device  1500  may also include various other components, such as one or more ports (e.g., charging port, data transfer port, or the like), additional input/output buttons, and so on. As such, the discussion of any electronic device, such as electronic device  1500 , is meant as illustrative only. 
       FIG. 15B  is a cross-sectional view of the electronic device of  FIG. 15A , taken along line B-B of  FIG. 15A . As illustrated, the electronic device  1500  includes the enclosure  1512 , crown  1518 , and the force sensor  1550 . The force sensor  1550  may be substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7C . For example, the force sensor  1550  may measure movement of an input structure in order to estimate a force input exerted on the input structure. In this regard, analogous to the components described in relation to the embodiments of  FIGS. 1-7C , the force sensor  1550  may include: input structure  1552 ; housing  1554 ; O-rings  1558 ; grooves  1560 ; sensor  1570 ; and first and second electrodes  1572   a ,  1572   b.    
     Notwithstanding the foregoing similarities, the force sensor  1550  may be integrated with the crown  1518  and/or other input structure of the electronic device  1500 . For example, the input structure  1552  may be coupled to, or integrally formed with, the crown  1518 . The crown  1518  may be a rotatable and translatable input member of the electronic device  1500 . Rotational and translational forces received along the crown  1518  for such input may cause the input structure  1552  to correspondingly rotate and/or move. In this regard, substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7C , a processing unit of the electronic device  1500  may determine a force associated with the translational and/or rotational input received at the crown  1518  based on movements of the input structure  1552 . For example, the force sensor  1550  may estimate the forces associated with the input exerted on the crown  1518  based on the movements of the input structure  1552  and one or more characteristics of the O-rings  1558  or other compliant member constrained between the input structure  1552  and the housing  1554 . 
     The processing unit of the electronic device  1500  may use the force associated with the rotational and/or translational input to control a function of the electronic device. For example, the display  1514  (depicted in  FIG. 15A ) may include a graphical output that is responsive in a first manner based on detecting a predetermined magnitude of a force input causing translation movement of the input structure  1552 . Further, the graphical output depicted at the display  1514  may be responsive in a second manner based on determining a predetermined magnitude of a force input causing rotational movement of the input structure  1552 . In some cases, the processing unit may control a time-keeping function of the electronic device  1500  using the determined force associated with the rotational and/or translational input received at the crown  1518 . 
       FIG. 16A  depicts an example electronic device  1600  having a keyboard assembly  1608 . Each key of the keyboard assembly  1608  may include a “stack up” of layered components that cooperate to trigger a switch event in response to a force input. The keyboard assembly  1608  may include, or be defined by, a force sensor  1650  (not shown in  16 A), such as the force sensors, force-sensitive assemblies, or the like discussed above and described in greater detail below. In this regard, the force sensor  1650  may be substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7C . As described with respect to  FIGS. 1-7C , the force sensor  1650  may be used in a variety of manners within the electronic device  1600 . For example, the force sensor  1650  may be configured to detect a force input at an input surface of the electronic device  1600 . 
     As a non-limiting example, as shown in  FIG. 16A , the electronic device  1600  may be a laptop computer. However, it is understood that electronic device  1600  may be any suitable device that operates with the keyboard assembly  1608  (or any other suitable device). Other examples of electronic devices may include wearable devices (including watches, glasses, rings, or the like), health monitoring devices (including pedometers, heart rate monitors, or the like), and other electronic devices. For purposes of illustration,  FIG. 16A  depicts the electronic device  1600  as including the keyboard assembly  1608 , an enclosure  1614 , a display  1616 , and one or more input/output members  1620 . It should be noted that the electronic device  1600  may also include various other components, such as one or more ports (e.g., a charging port, a data transfer port, or the like), communications elements, additional input/output members (including buttons), and so on. As such, the discussion of any computing device, such as electronic device  1600 , is meant as illustrative only. 
     The keyboard assembly  1608  may be positioned within the enclosure  1614 . In a non-limiting example shown in  FIG. 16A , the keyboard assembly  1608  may include a set of key caps  1610 . The set of key caps  1610  may partially protrude from the enclosure  1614  and each key cap of the set of key caps  1610  may be substantially surrounded by the enclosure  1614 . The set of key caps  1610  may be configured to receive a force input. The force input may depress a particular one of the set of key caps  1610  to trigger one or more switch events that may control the electronic device  1600 . As depicted, the keyboard assembly  1608  may be positioned within the electronic device  1600 . In an alternative embodiment, the keyboard assembly  1608  may be a distinct, standalone component in electronic communication with the electronic device  1600  via a wireless or hardwired connection. 
       FIG. 16B  is a simplified cross-sectional view of the electronic device keyboard assembly  1608  of  FIG. 16A , taken along C-C of  FIG. 16A . As illustrated, the keyboard assembly  1608  may include, or be defined by, the force sensor  1650 . The force sensor  1650  may be substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7C . For example, the force sensor  1650  may measure movement of an input structure in order to determine a force input exerted on the input structure. In this regard, analogous to the components described in relation to the embodiments of  FIGS. 1-7C , the force sensor  1650  may include: input structure  1652 ; substrate  1654 ; compliant member  1656 ; sensor  1670 ; and first and second electrodes  1672   a ,  1672   b.    
     Notwithstanding the foregoing similarities, the force sensor  1650  may be integrated within the keyboard assembly  1608  (or other portion of the device&#39;s body) to detect force input received along the set of key caps  1610 . For example, the input structure  1652  may be coupled to, or integrally formed with, the key cap  1610  depicted in  FIG. 16A . The key cap  1610  may be configured to receive a force input in order to control a function of the electronic device  1600 . In this regard, substantially analogous to the force sensor  150  described with respect to  FIGS. 1-7C , a processing element of the electronic device  1600  may determine a force associated with the input received at the key cap  1610  based on movements of the input structure  1652 . For example, the force sensor  1650  may determine the forces associated with the input exerted on the key cap  1610  based on the movements of the input structure  1652  and one or more characteristics of the compliant member  1656  or other elastic structure that is constrained between the input structure  1652  and the substrate  1654 . In turn, the processing element of the electronic device  1600  may use the determined force associated with the input at the key cap  1610  to control a function of the electronic device  1600 . 
       FIG. 17  presents an illustrative computing system  1700  in which electronic device  100  is interconnected with input device  120 . The schematic representation in  FIG. 17  may correspond to the electronic device  100  and the input device  120  depicted in  FIGS. 1-14B , described above. However,  FIG. 17  may also more generally represent other types of devices and configurations that may be used to receive a user input signal from an input device in accordance with the embodiments described herein. In this regard, the computing system  1700  may include any appropriate hardware (e.g., computing devices, data centers, switches), software (e.g., applications, system programs, engines), network components (e.g., communication paths, interfaces, routers) and the like (not necessarily shown in the interest of clarity) for use in facilitating any appropriate operations disclosed herein. 
     Generally, the input device  120  may be configured to receive a force input along an input structure and generate a corresponding user input signal based on the received input. The user input signal may correspond to a predetermined function executable by the electronic device  100 . In this regard, the electronic device  100  and input device  120  may be interconnected via operative link  1704 . Operative link  1704  may be configured for electrical power and/or data transfer between the electronic device  100  and the input device  120 . In this manner, input device  120  may be configured to control the electronic device  100 . For example, the user input signal generated by the input device  120  may be transmitted to the electronic device  100  via operative link  1704 . Operative link  1704  may also be used to transfer one or more signals from the electronic device  100  to the input device  120  (e.g., a signal indicative of a magnitude and/or a direction of a force input received along an input structure of the input device  120 ). In some cases, operative link  1704  may be a wireless connection; in other instances, operative link  1704  may be a hardwired connection. 
     As shown in  FIG. 17 , the electronic device  100  may include a processing unit or element  1708   a  operatively connected to computer memory  1712  and computer-readable media  1716 . The processing unit  1708   a  may be operatively connected to the memory  1712  and computer-readable media  1716  components via an electronic bus or bridge (e.g., such as system bus  1710 ). The processing unit  1708   a  may include one or more computer processors or microcontrollers that are configured to perform operations in response to computer-readable instructions. The processing element  1708   a  may be a central processing unit of the electronic device  100 . Additionally or alternatively, the processing unit  1708   a  may be other processors within the device including application specific integrated chips (ASIC) and other microcontroller devices. 
     The memory  1712  may include a variety of types of non-transitory computer-readable storage media, including, for example, read access memory (RAM), read-only memory (ROM), erasable programmable memory (e.g., EPROM and EEPROM), or flash memory. The memory  1712  is configured to store computer-readable instructions, sensor values, and other persistent software elements. Computer-readable media  1716  may also include a variety of types of non-transitory computer-readable storage media including, for example, a hard-drive storage device, a solid-state storage device, a portable magnetic storage device, or other similar device. The computer-readable media  1716  may also be configured to store computer-readable instructions, sensor values, and other persistent software elements. 
     In this example, the processing unit  1708   a  is operable to read computer-readable instructions stored on the memory  1712  and/or computer-readable media  1716 . The computer-readable instructions may adapt the processing unit  1708   a  to perform the operations or functions described above with respect to  FIGS. 2-16B . The computer-readable instructions may be provided as a computer-program product, software application, or the like. It should be appreciated that the processing unit  1708   a  may be located in an electronic device associated with the stylus, rather than the stylus itself. In such embodiments, data may be transmitted from the stylus to and from the electronic device, such that the processing unit in the electronic device may operatively control the stylus. 
     As shown in  FIG. 17 , the electronic device  100  may also include a display  1718 . The display  1718  may include a liquid-crystal display (LCD), organic light emitting diode (OLED) display, light emitting diode (LED) display, or the like. If the display  1718  is an LCD, the display may also include a backlight component that can be controlled to provide variable levels of display brightness. If the display  1718  is an OLED or LED type display, the brightness of the display  1718  may be controlled by modifying the electrical signals that are provided to display elements. 
     The electronic device  100  may also include a battery  1724  that is configured to provide electrical power to the components of the electronic device  100 . The battery  1724  may include one or more power storage cells that are linked together to provide an internal supply of electrical power. In this regard, the battery  1724  may be a component of a power source  1728  (e.g., including a charging system or other circuitry that supplies electrical power to components of the electronic device  100 ). The battery  1724  may be operatively coupled to power management circuitry that is configured to provide appropriate voltage and power levels for individual components or groups of components within the electronic device  100 . The battery  1724 , via power management circuitry, may be configured to receive power from an external source, such as an AC power outlet or interconnected computing device. The battery  1724  may store received power so that the electronic device  100  may operate without connection to an external power source for an extended period of time, which may range from several hours to several days. 
     The electronic device  100  may also include one or more sensors  1740  that may be used to detect a touch and/or force input, environmental condition, orientation, position, or some other aspect of the electronic device  100 . Example sensors  1740  that may be included in the electronic device  100  may include, without limitation, one or more accelerometers, gyrometers, inclinometers, goniometers, or magnetometers. The sensors  1740  may also include one or more proximity sensors, such as a magnetic hall-effect sensor, inductive sensor, capacitive sensor, continuity sensor, or the like. 
     The sensors  1740  may also be broadly defined to include wireless positioning devices including, without limitation, global positioning system (GPS) circuitry, Wi-Fi circuitry, cellular communication circuitry, and the like. The electronic device  100  may also include one or more optical sensors including, without limitation, photodetectors, photosensors, image sensors, infrared sensors, or the like. In one example, the sensor  1740  may be an image sensor that detects a degree to which an ambient image matches a stored image. As such, the sensor  1740  may be used to identify a user of the electronic device  100 . The sensors  1740  may also include one or more acoustic elements, such as a microphone used alone or in combination with a speaker element. The sensors  1740  may also include a temperature sensor, barometer, pressure sensor, altimeter, moisture sensor or other similar environmental sensor. The sensors  1740  may also include a light sensor that detects an ambient light condition of the electronic device  100 . 
     The sensor  1740 , either alone or in combination, may generally be a motion sensor that is configured to determine an orientation, position, and/or movement of the electronic device  100 . For example, the sensor  1740  may include one or more motion sensors including, for example, one or more accelerometers, gyrometers, magnetometers, optical sensors, or the like to detect motion. The sensors  1740  may also be configured to determine one or more environmental conditions, such as temperature, air pressure, humidity, and so on. The sensors  1740 , either alone or in combination with other input, may be configured to estimate a property of a supporting surface including, without limitation, a material property, surface property, friction property, or the like. 
     The electronic device  100  may also include a camera  1732  that is configured to capture a digital image or other optical data. The camera  1732  may include a charge-coupled device, complementary metal oxide (CMOS) device, or other device configured to convert light into electrical signals. The camera  1732  may also include one or more light sources, such as a strobe, flash, or other light-emitting device. As discussed above, the camera  1732  may be generally categorized as a sensor for detecting optical conditions and/or objects in the proximity of the electronic device  100 . However, the camera  1732  may also be used to create photorealistic images that may be stored in an electronic format, such as JPG, GIF, TIFF, PNG, raw image file, or other similar file types. 
     The electronic device  100  may also include a communication port  1744  that is configured to transmit and/or receive signals or electrical communication from an external or separate device. The communication port  1744  may be configured to couple to an external device via a cable, adaptor, or other type of electrical connector. In some embodiments, the communication port  1744  may be used to couple the electronic device  100  with a computing device and/or other appropriate accessories configured to send and/or receive electrical signals. The communication port  1744  may be configured to receive identifying information from an external accessory, which may be used to determine a mounting or support configuration. For example, the communication port  1744  may be used to determine that the electronic device  100  is coupled to a mounting accessory, such as a particular type of stand or support structure. 
     As described above with respect to  FIGS. 1-7C , the input device  120  may generally employ various components and systems to facilitate receiving a force input and generating a corresponding user input signal. As shown, and with reference to  FIGS. 1-7C , the input device  120  may include the force sensor  150  and the sensor  170 . The input device  120  may also include a processing unit  1708   b . The processing unit  1708   b  may be coupled with the force sensor  150  and configured in a manner substantially analogous to that of the processing unit  1708   a  of the electronic device  100 . For example, the processing unit  1708   a  may include one or more computer processors or microcontrollers that are configured to perform operations in response to computer-readable instructions. The processing unit  1708   b  may also be used to generate a user input signal in response to a force input detected by the force sensor  150 . 
     As described above, the input device  120  may be configured to estimate a magnitude or direction of a force input received along an input structure. For example, the input structure may be constrained within an opening or interior volume by a compliant member. The compliant member may be coupled along the input structure such that the compliant member operates to control movements of the input structure. The sensor  170  may detect movements of the input structure. One or both of the processing units  1708   a ,  1708   b  may estimate a force input received at the input structure using the detected motion or displacement of the input structure and a characteristic of the compliant member, as described herein. In some cases, the processing unit  1708  may use the estimated force input to generate a user input signal used to control a function of the electronic device  100 . 
     Other examples and implementations are within the scope and spirit of the disclosure and appended claims. For example, features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or” as used in a list of items prefaced by “at least one of” indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Further, the term “exemplary” does not mean that the described example is preferred or better than other examples. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20180124
Publication Date: 20210302
Grant Date: 20210302
Priority Date: 20170228
Inventors: BAUGH, BRENTON A.
WONG, WINGSHAN
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/169", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1684", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/163", "inventive": false, "first": false, "tree": "[]"}, {"code": "G04G21/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04G21/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0346", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/03545", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0346", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0383", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 74683167