PATENT DOCUMENT

Publication Number: US-10032550-B1
Application Number: US-201715474638-A
Country: US
Kind Code: B1

Title: Moving-coil haptic actuator for electronic devices

Abstract:
A haptic actuator features magnets coupled to an enclosure and a movable mass with a conduction loop coupled to the enclosure via one or more movement elastic members. One or more conduction elastic members may be used to transmit signals to the conduction loop to cause the movable mass to move bilinearly relative to the enclosure and the magnets. The magnets may consist of a Halbach array to direct magnetic flux toward the conduction loop and away from other device components. Ferrofluid may be included between one or more of the magnets and the conduction loop to act as a damper in the system to improve haptic feedback. Closed loop control, such as back EMF, capacitive sensing, and magnetic sensing, may be included to improve system response.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a device casing; 
 a display coupled to the device casing; 
 an actuator coupled to the device casing and for providing haptic feedback through the device casing, the actuator comprising:
 an enclosure that forms an interior volume; 
 a magnet attached to the enclosure, the magnet configured to generate a first magnetic field in the interior volume; 
 a movable mass disposed in the interior volume, the movable mass configured to oscillate within the interior volume along a longitudinal axis of the enclosure; 
 a conduction loop affixed to the movable mass and operative to generate a second magnetic field in response to an electromagnetic signal; 
 a movement elastic member disposed between the movable mass and the enclosure and configured to exert a force on the movable mass, the force varying with a position of the movable mass; and 
 a conduction elastic member coupled to the enclosure and the conduction loop, the conduction elastic member configured to convey the electromagnetic signal; and 
 
 a controller coupled to the conduction loop by the conduction elastic member and configured to initiate the electromagnetic signal to the conduction loop. 
 
     
     
       2. The electronic device of  claim 1 , wherein:
 the magnet is a first magnet; 
 the movement elastic member is a first movement elastic member; 
 the conduction elastic member is a first conduction elastic member; and 
 the actuator further comprises:
 a second magnet attached to the enclosure, the movable mass located between the first magnet and the second magnet, the second magnet configured to generate a third magnetic field in the interior volume; 
 a second conduction elastic member coupled to the enclosure and the conduction loop; 
 a first contact attached to the enclosure and the first conduction elastic member, the first contact configured to constrain an end of the first conduction elastic member; 
 a second contact attached to the enclosure and the second conduction elastic member, the second contact configured to constrain an end of the second conduction elastic member; 
 a second movement elastic member disposed between the movable mass and the enclosure; further wherein:
 the first movement elastic member is a first flexure spring connected to a first connection location of the movable mass, the first connection location offset from the longitudinal axis in a first direction; 
 the second movement elastic member is a second flexure spring connected to a second connection location of the movable mass, the second connection location offset from the longitudinal axis in a second direction, the second direction different from the first direction; 
 the first conduction elastic member is a first beehive spring connected to a third connection location of the movable mass, the third connection location offset from the longitudinal axis; 
 the second conduction elastic member is a second beehive spring connected to a fourth connection location of the movable mass, the fourth connection location offset from the longitudinal axis; 
 the conduction loop comprises two rounded rectangular coils; and 
 the first and second conduction elastic members expand and contract as the movable mass moves. 
 
 
 
     
     
       3. The electronic device of  claim 1 , wherein the magnet comprises a Halbach array. 
     
     
       4. The electronic device of  claim 1 , wherein the movable mass comprises a first portion disposed within a second portion, the first portion thinner than a second portion. 
     
     
       5. The electronic device of  claim 1 , wherein the movement elastic member has a spring force between 0.5 and 3 N/mm. 
     
     
       6. The electronic device of  claim 5 , wherein the conduction elastic member has a spring force between 0.001-0.01 N/mm. 
     
     
       7. The electronic device of  claim 1 , wherein the actuator further comprises a ferrofluid disposed between the first magnet and the movable mass. 
     
     
       8. An actuator for providing haptic feedback in an electronic device, the actuator comprising:
 an enclosure defining a first side and a second side opposite the first side; 
 a first magnet coupled to the first side of the enclosure; 
 a second magnet coupled to the second side of the enclosure; 
 a movable mass disposed between the first and second magnets; 
 a conduction loop connected to the movable mass; 
 a first movement elastic member attached to the enclosure and to a first connection location of the movable mass; 
 a second movement elastic member attached to the enclosure and to a second connection location of the movable mass; and 
 a conduction elastic member physically coupled to the enclosure and to the movable mass, the conduction elastic member electrically coupled to the conduction loop. 
 
     
     
       9. The actuator of  claim 8 , wherein the first and second movement elastic members comprise at least one of a flexure spring, a leaf spring, or a coil spring. 
     
     
       10. The actuator of  claim 8 , wherein a reaction force of the movement elastic member is between 100 and 1000 times greater than a spring force of the conduction elastic member. 
     
     
       11. The actuator of  claim 8 , wherein a density of the movable mass is greater than 15 grams per cubic centimeter. 
     
     
       12. The actuator of  claim 8 , wherein:
 the conduction elastic member is a first conduction elastic member; and 
 the actuator further comprises:
 a second conduction elastic member coupled to the enclosure and the movable mass; wherein 
 the second conduction elastic member is electrically coupled to the conduction loop. 
 
 
     
     
       13. The actuator of  claim 12 , wherein:
 the enclosure has a longitudinal axis; 
 the first connection location is offset from the longitudinal axis in a first direction; and 
 the second connection location is offset from the longitudinal axis in a second direction, the second direction different from the first direction. 
 
     
     
       14. The actuator of  claim 13 , wherein:
 the first conduction elastic member is connected to a third connection location of the movable mass, the third connection location offset from the longitudinal axis in a third direction, the third direction different from the first direction; and 
 the second conduction elastic member is connected to a fourth connection location of the movable mass, the fourth connection location offset from the longitudinal axis in a fourth direction, the fourth direction different from the second direction. 
 
     
     
       15. The actuator of  claim 8 , wherein the conduction elastic member is one of a flexure spring, a leaf spring, or a coil spring. 
     
     
       16. A method for operating an actuator to provide haptic output to an electronic device, the method comprising:
 transmitting a drive signal to a conduction loop of the actuator, thereby causing the conduction loop and a movable body within the actuator to oscillate; 
 receiving, at a controller, feedback data indicating a position of the movable body within an enclosure of the actuator; 
 generating, by the controller and based on the feedback data, a signal for providing a haptic output via the actuator; 
 transmitting the signal to the conduction loop; 
 receiving second feedback data indicating a second position of the movable body; and 
 verifying, with the second feedback data, that the haptic output matches a desired haptic output. 
 
     
     
       17. The method of  claim 16 , wherein verifying that the haptic output matches the desired haptic output using the second feedback data comprises comparing at least one of a determined position, a determined velocity, or a determined acceleration with one or more expected values. 
     
     
       18. The method of  claim 16 , wherein the drive signal generates, by the conduction loop, a magnetic field that interacts with one or more additional magnetic fields, thereby causing the movable body within the actuator to oscillate. 
     
     
       19. The method of  claim 16 , wherein the second position of the movable body indicates unwanted motion of the movable body. 
     
     
       20. The method of  claim 19 , further comprising:
 generating a corrective signal to mitigate the unwanted motion of the movable body; and 
 transmitting the signal to the conduction loop.

Description:
FIELD 
     Embodiments described herein relate to electronic devices, and in particular, to electronic devices that incorporate a haptic feedback system to provide haptic output to a user. 
     BACKGROUND 
     An electronic device can include a mechanical actuator to generate tactile sensations for a user, generally referred to as “haptic output.” Mechanical output from the actuator can inform the user of a specific mode, operation, or state of the electronic device, or for any other suitable purpose. Such actuators, together with associated electronic circuitry, can be referred to as “haptic output components.” 
     Some haptic output components are linear actuators that include an enclosure, a conductive coil coupled to the enclosure, and a movable mass that includes a magnet that is operable to move relative to the enclosure and the coil when a current is applied to the coil. This contributes to undesirable magnetic interference between the moving magnets and other components of the electronic device. 
     SUMMARY 
     Certain embodiments described herein relate to, include, or take the form of an electronic device including: a device casing, a display coupled to the device casing, an actuator, and a controller. The actuator is coupled to the device casing and provides haptic feedback at the electronic device. The actuator includes an enclosure that forms an interior volume. A magnet is attached to the enclosure and may be configured to generate a first magnetic field in the interior volume. A movable mass is disposed in the interior volume of the enclosure. The movable mass is configured to oscillate within the interior volume along a longitudinal axis of the enclosure. The actuator further includes a conduction loop affixed to the movable mass and operative to generate a second magnetic field responsive to an electrical current. The actuator further includes a movement elastic member between the movable mass and the enclosure. The movement elastic member is configured to exert a force which varies with a position of the movable mass. The actuator further includes a conduction elastic member coupled to the enclosure and the conduction loop and configured to convey an electromagnetic signal. The controller is coupled to the conduction loop by the conduction elastic member and is configured to send the electromagnetic signal to the conduction loop. 
     Other embodiments described generally reference an actuator for providing haptic feedback in an electronic device. The actuator includes an enclosure defining a first side and a second side opposite the first side, a first magnet coupled to the first side of the enclosure, a second magnet coupled to the second side of the enclosure opposite the first side, a movable mass disposed between the first and second magnets, and a conduction loop connected to the movable mass. The actuator further includes a first movement elastic member attached to the enclosure and a first connection location of the movable mass and a second movement elastic member attached to the enclosure and a second connection location of the movable mass. The actuator further includes a conduction elastic member coupled to the enclosure and the movable mass. The conduction elastic member is electrically coupled to the conduction loop. 
     Still further embodiments described herein generally reference a method for operating a controller for an actuator for providing haptic feedback to an electronic device including the operations of transmitting a drive signal to a conduction loop of an actuator that causes a movable body within the actuator to oscillate, receiving feedback data indicating a position of a movable body within the actuator, generating a signal for providing a haptic output based on the feedback data, transmitting the signal to the conduction loop, receiving second feedback data indicating a second position of the movable body, and verifying that the haptic output matches a desired haptic output using the second feedback data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to representative embodiments illustrated in the accompanying figures. It should be understood that the following descriptions are not intended to limit this disclosure to one preferred embodiment. To the contrary, the disclosure provided herein is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the described embodiments, and as defined by the appended claims. 
         FIG. 1  illustrates an example electronic device that may incorporate a haptic feedback system according to one or more embodiments presented herein. 
         FIG. 2  is a simplified system diagram depicting selected components of a haptic feedback system according to one example embodiment. 
         FIG. 3A  depicts an example haptic actuator, such as described herein. 
         FIG. 3B  is a cross-section of the haptic actuator of  FIG. 3A , taken through section line A-A of  FIG. 3A . 
         FIG. 3C  is a cross-section of the haptic actuator of  FIG. 3A , taken through section line B-B of  FIG. 3B . 
         FIG. 4A  depicts a second example haptic actuator, such as described herein. 
         FIG. 4B  is a cross-section of the haptic actuator of  FIG. 4A , taken through section line C-C of  FIG. 4A . 
         FIG. 4C  is a cross-section of the haptic actuator of  FIG. 4A , taken through section line D-D of  FIG. 4B . 
         FIGS. 5A-5H  depict example configurations for magnet arrays in haptic actuators, such as those described herein. 
         FIGS. 6A-6C  depict an example configuration for capacitive sensors within a haptic actuator, such as described herein. 
         FIGS. 7A-7C  depict example configurations for magnetic sensors within a haptic actuator such as those described herein. 
         FIGS. 8A-8C  are cross-sections similar showing portions of example haptic actuators, such as those described herein. 
         FIG. 9  is a simplified flow chart depicting example operations of a haptic feedback system, such as described herein. 
     
    
    
     The use of the same or similar reference numerals in different figures indicates similar, related, or identical items. 
     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 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the claims. 
     The embodiments disclosed herein are directed to a haptic feedback system for use as part of an electronic device. An electronic device transmits a signal to a user in the form of a haptic output (e.g., a tactile output). Examples include a smart watch that vibrates at a scheduled time, a cell phone that vibrates for an incoming call, a tablet or other touch-sensitive computing device that provides feedback in response to a sensed touch, a track pad that provides haptic feedback to confirm an input, and many others. A haptic feedback system, as described herein, includes one or more haptic actuators for providing a haptic output, a controller for controlling operations of the haptic actuator, and/or one or more feedback sensors for enabling closed loop control of the haptic actuator. 
     A haptic actuator generates a haptic output. Haptic actuators often include a support mechanism (e.g., a housing or an enclosure) attached to an electronic device, for example within a device housing, device casing, or device enclosure, and a linear actuator that moves a mass in varying directions; changes in momentum of the mass are transmitted through the support mechanism to the electronic device. In particular, linear actuators work by moving a mass in one or both directions substantially along a single line or axis. 
     The linear actuators described herein operate to produce a haptic output by moving a mass bilinearly, that is, in both directions along a single line. Such bilinear motion may be termed “linear motion” and objects exhibiting such bilinear motion will be said to be moving “linearly.” Through conservation of momentum, changes in the direction of motion of the mass are transferred to support mechanisms of the mass. When the support mechanisms are connected to an electronic device, either directly or through intermediate components such as a housing or enclosure for the actuator, the changed momentum of the mass is transferred to the electronic device and so produces a haptic output. 
     Some forms of linear actuators are configured to have one or more current carrying coils of wires that are stationary within a housing. In those forms, a movable mass may include one or more magnets, either permanent magnets or electromagnets. Electrical current (e.g., alternating current, electromagnetic signals, drive signals, and the like) induced in the current carrying coils generates magnetic fields that in turn exert electromagnetic forces on the magnets of the movable mass. As used herein, an “electromagnetic force” denotes an electric force, a magnetic force, or a combination thereof. 
     In contrast, some linear actuators described herein include stationary magnetic masses (e.g., permanent magnets, electromagnets, and the like) attached to a housing of the linear actuator. In some embodiments, the housing defines an interior volume. A dynamic body (e.g., movable mass, movable body) within the interior volume of the housing is attached to one or more conduction loops (e.g., electromagnetic coils, electrically conductive coils, wire loops, other electrically conductive materials, and the like). Electrical currents (e.g., alternating current, electromagnetic signals, drive signals, and the like) induced in the conduction loops result in a Lorentz force that can cause the conduction coils to move, thereby causing the attached movable mass to move. The motion of the movable body is constrained and controlled by various mechanisms within the actuator, including springs, elastic members, and the like, as discussed in more detail below. As a result, the movable body oscillates within the interior volume along a longitudinal axis of the housing. 
     Further, magnetic fields generated by the stationary magnets can be oriented to pass into a housing made of a ferritic material. Typically, but not necessarily, a ferritic material has a high magnetic permeability. When the stationary magnets are arranged in a linear array and adjacent magnets of the array have alternating polarities, the magnetic flux from the permanent magnets may be mostly confined to the housing and to shield components outside the haptic actuator from magnetic fields. An example arrangement of stationary magnets is a Halbach array. Further, a ferritic housing can shield the internal components of the haptic actuator from electromagnetic fields originating outside the haptic actuator. 
     When the movable mass is made, at least in part, of a ferritic material, the magnetic fields produced by the magnets or magnetic masses can then be channeled into the interior volume and so reduce fringing effects of the magnetic fields. This can increase the strength of the magnetic fields that contribute to the Lorentz force, and so produce a stronger haptic output from less electrical current. In one embodiment, the movable mass has a relatively thin middle portion and thicker outside portions. This helps to minimize the thickness of the actuator as a whole by providing space above and below the middle portion for placement of the magnets. Further, the thicker outside portions increase the weight of the movable mass which allows for a stronger haptic output by the actuator. 
     The movable mass may be attached to the actuator housing or enclosure by one or more elastic members to facilitate movement (e.g., oscillation) of the mass within the enclosure (herein “movement elastic members”). Example movement elastic members include springs (herein “motion springs”), gels, elastomers, and the like. In one embodiment, the motion springs are flexure springs. 
     The movable mass, the conduction loop, or both may be electrically coupled to the enclosure to facilitate transmission of electrical current, such as electromagnetic signals and drive signals, to the conduction loop. In one embodiment, the movable mass is electrically coupled to the enclosure by one or more elastic members to maintain the electrical connection between the enclosure and the conduction loop even when the movable mass is moving within the enclosure (herein, “conduction elastic members”). The conduction elastic member may be a spring (herein, “contact springs”), a gel, an elastomer, or the like. This can create or facilitate a reliable connection between the enclosure and the movable mass over thousands, millions, or more cycles of movement of the movable mass. In one embodiment, the reaction force (e.g., spring force) of the movement elastic member is much greater than the reaction force of the conduction elastic member, such that the conduction elastic member does not materially influence the dynamics of the movable mass. 
     The movable mass and the magnetic masses (e.g., magnets) may be separated by a medium that allows relative motion of each. In one embodiment, this medium is air. In another embodiment, this medium is a fluid, which can act as a damper to help control the oscillation of the movable mass. Additionally, some combination of air and fluid may be used, for example fluid on one side of the movable mass and air on another side. The fluid may be a ferrofluid, a magnetized fluid, or similar. In embodiments where a ferrofluid is disposed between the movable mass and one or more of the magnets, the ferrofluid may direct magnetic flux toward the movable mass to increase the efficiency of the haptic actuator by requiring a smaller input signal amplitude to achieve the same electrical current in the conduction loop. The ferrofluid also has the advantage of being held in place by magnetic forces from the magnet, and thus does not require additional structure or mechanisms for containment, which allows for less overall complexity, weight, and volume of the haptic actuator. 
     In one embodiment, the haptic feedback system includes a controller electrically coupled to the haptic actuator to control operation of the haptic actuator. The controller can include, or can be communicably coupled to, circuitry and/or logic components, such as a processor. The circuitry can perform or coordinate some or all of the operations of the controller including, but not limited to: providing a signal to a haptic actuator to generate an output; receiving a feedback signal from a haptic actuator; generating signals based on feedback; and so on. 
     The controller can be implemented as any electronic device or component capable of processing, receiving, or transmitting data or instructions in an analog and/or digital domain. For example, the controller can be a processor such as a microprocessor, a central processing unit, an application-specific integrated circuit, a field-programmable gate array, a digital signal processor, an analog circuit, a digital circuit, or combination of such devices. The processor may be a single-thread or multi-thread processor. The processor may be a single-core or multi-core processor. 
     Accordingly, as described herein, the phrase “controller” refers to a hardware-implemented data processing device or circuit physically structured to execute specific transformations of data including data operations represented as code and/or instructions included in a program that can be stored within and accessed from an integrated or separate memory. The term or phrase is meant to encompass a single processor or processing unit, multiple processors, multiple processing units, analog or digital circuits, or other suitably configured computing element or combination of elements. 
     In one embodiment, the haptic feedback system includes one or more feedback sensors electrically coupled to the haptic actuator, the controller, or both. Feedback signals are provided to the controller to facilitate closed-loop control to maintain desired haptic output. 
     The feedback sensors can include magnetic, mechanical, and/or electrical sensors for determining characteristics of haptic actuator components, including proximity, position, displacement, velocity, acceleration, force, and the like. For example, sensors may be used to determine the position, velocity, or acceleration of the movable mass within the enclosure of the haptic actuator. Example feedback sensors include capacitive sensors and Hall Effect sensors. A capacitive sensor varies its output voltage based on changes in capacitance, which can be used to determine the aforementioned characteristics of haptic actuator components. A Hall Effect sensor varies its output voltage based on changes in magnetic field, which can be used to determine the aforementioned characteristics of haptic actuator components. 
     In one embodiment, closed loop control is implemented by determining the counter-electromotive force or back electromotive force (herein, “back-EMF”), or the voltage generated by the motion of the movable mass within the enclosure, which can be used to determine the position of the movable mass at a given time. 
     Detailed embodiments of these general considerations will now be disclosed in relation to the accompanying figures. 
       FIG. 1  illustrates an example electronic device  100  that may incorporate a haptic feedback system according to one or more embodiments presented herein. The electronic device  100  includes a device casing  102 , a display  104 , and a user input button  106 . The device casing  102  retains, supports, and/or encloses various components of the electronic device  100 , such as a display  104 . The display  104  may include a stack of multiple layers (e.g., a display stack) including, for example, and in no particular order: an organic light emitting diode layer, a touch input layer, a force input layer, and so on. Other embodiments can implement the display  104  in a different manner, such as with liquid crystal display technology, electronic ink technology, quantum dot technology, and so on. 
     The electronic device  100  can also include a processor, memory, power supply and/or battery, network connections, sensors, input/output ports, acoustic elements, haptic elements, digital and/or analog circuits for performing and/or coordinating tasks of the electronic device  100 , and so on. For simplicity of illustration, the electronic device  100  is depicted in  FIG. 1A  without many of these elements, each of which may be included, partially and/or entirely, within the device casing  102  and may be operationally or functionally associated with, or coupled to, the display  104  and/or the user input button  106 . Output of the display  104  may vary with operation of the device, receipt of information by the device, input received from an input mechanism (such as button  106 ), output (such as may be generated by a haptic actuator as described herein), and so on. 
     Furthermore, although illustrated as a cellular phone, the electronic device  100  can be another electronic device that is either stationary or portable, taking a larger or smaller form factor than illustrated. For example, in certain embodiments (and as noted above), the electronic device  100  can be a laptop computer, a tablet computer, a wearable device, a health monitoring device, a home or building automation device, a home or building appliance, a craft or vehicle entertainment, control, and/or information system, a navigation device, and so on. 
       FIG. 2  is a simplified system diagram depicting selected components of a haptic feedback system  200  according to one example embodiment. In this example, the haptic feedback system  200  includes a controller  210 , an actuator  220 , and a feedback sensor  230 . 
     In various embodiments, the controller  210  receives instructions to drive the actuator  220  to generate a haptic output from one or more components of the electronic device. The controller  210  provides a drive signal to drive the actuator  220 . Typically, the drive signal is a voltage signal that corresponds to a particular haptic output that can be generated by the actuator  220 . 
     The controller  210  receives feedback signals from the feedback sensor  230  to facilitate closed-loop feedback to achieve a desired haptic output. In many cases, the circuitry of the controller can include one or more signal processing stages which can include, but may not be limited to, amplifying stages, filtering stages, multiplexing stages, digital-to-analog conversion stages, analog-to-digital conversion stages, comparison stages, feedback stages, charge amplification stages, and so on. The controller  210  may be integrated with components of the electronic device, including, for example, the processor, memory, power supply, and so on. 
     The actuator  220  produces a haptic output based on electrical current (e.g., in the form of drive signals, electromagnetic signals, and the like) received from the controller  210 . The actuator  220  may be a linear actuator (such as a linear resonance actuator) that produces a haptic output by linear motion of a mass. The actuator  220  includes an enclosure or housing, one or more magnetic masses (e.g., magnets), and a movable mass that includes a conduction loop (e.g., a wire loop, wound coil, and the like). 
     The feedback sensor  230  provides feedback signals to the controller  210 . Feedback signals can be used by the controller  210  to determine characteristics of the actuator  220  to facilitate closed-loop control to produce a desired haptic output. Characteristics include the position and/or velocity of the movable mass within the enclosure. As an example, consider a situation in which the desired haptic output is consistent with linear motion of the movable mass (i.e., motion along an axis in an x-direction only). The controller  210  may determine from feedback data received by the feedback sensor  230  that there is motion in the y- and/or z-direction that is not consistent with the desired haptic output. In one embodiment, the controller  210  compares expected values for the feedback data to the received feedback data. As a result of this determination the controller  210  may adjust the drive signal (e.g., generate a corrective signal) to correct the unwanted motion and achieve the desired haptic output. 
     The feedback sensor  230  may include one or more sensors, such as capacitive sensors for measuring changes in capacitance of components of the actuator  220 , and/or Hall Effect sensors for measuring changes in a magnetic field of the actuator  220 . The feedback sensor  230  may consist of multiple sensors at different locations within and around the actuator  220 . The feedback sensor  230  may be integrated with the controller  210 , for example as a circuit, processor, algorithm, or the like (e.g., a back electromotive force sensor) configured to determine a back-EMF of the actuator  220 , or the voltage generated by the motion of the movable mass within the enclosure, which can be used to determine the position of the movable mass at a given time. 
     In some embodiments, the haptic feedback system  200  does not include feedback sensors  230 . In this embodiment, the controller  210  and the actuator  220  operate in open-loop mode, as opposed to closed-loop or feedback control mode. In this embodiment, the controller  210  generates a desired signal or waveform to produce a haptic output, and the actuator  220  produces the haptic output in response to receiving the desired waveform from the controller. 
     The actuator  220 , the feedback sensor  230 , and the components and structure of each are discussed in more detail below with respect to  FIGS. 3A-8D . 
       FIG. 3A  depicts an example construction of a haptic actuator  300 , such as described herein. The haptic actuator  300  includes an enclosure  301 . In various embodiments, the enclosure  301  is a substantially rectangular housing comprised of a durable material (e.g., stainless steel, titanium, aluminum or other suitable metals, ceramic, certain polymers, and the like). The enclosure  301  may consist of multiple parts, such as a base and a crust, which fit together to form an interior volume within the enclosure. The enclosure  301  may include one or more openings, for example for power delivery components. The enclosure  301  may further include attachment mechanisms for attaching or otherwise integrating the enclosure into the electronic device  100 , for example within the device casing  102 . Further, the enclosure  301  may include various components that are not pictured in the figures, including electrical transmission components such as flex cables for transmitting signals within the enclosure. The enclosure  301  may further include motion control components, such as stoppers, bump guards, and the like. The motion control components may be used to protect components of the actuator  300  from damage based on the motion within the actuator. 
       FIG. 3B  is a cross-section of the haptic actuator  300 , taken through section line A-A of  FIG. 3A . The haptic actuator  300  includes a dynamic body  310 , a conduction loop  320 , movement elastic members  330 A-B, conduction elastic members  340 A-B, and one or more magnets (not pictured in  FIG. 3B ).  FIG. 3C  is a cross-section of the haptic actuator  300 , taken through section line B-B of  FIG. 3B .  FIG. 3C  illustrates magnets  350 A-B. 
     The dynamic body  310  is disposed in the interior volume of the enclosure  301  and mechanically coupled to the enclosure  301  by movement elastic members  330 , and electrically coupled to the enclosure  301  by conduction elastic members  340 . The dynamic body  310  may be made of a high-density material (e.g., greater than 15 grams per cubic centimeter) to maximize the momentum of the mass and thus the strength of the haptic feedback during motion of the actuator. In one embodiment, the dynamic body  310  is made of tungsten. 
     The conduction loop  320  is coupled (e.g., affixed) to the dynamic body  310  and is electrically coupled to the conduction elastic members  340 . The conduction loop  320  may be made of any suitable conductive material that can be energized by an electrical current (e.g., a drive signal or other electromagnetic signal), thereby generating a Lorentz force to cause the dynamic body to move along the longitudinal axis of the enclosure  301  (e.g., the left-to-right and right-to-left directions in  FIG. 3B ). In one embodiment, the conduction loop  320  is a substantially round loop made of round wire (e.g., copper wire). In another embodiment, as illustrated in  FIG. 3B , the conduction loop  320  is an electromagnetic coil that has a rounded-rectangular shape and is made of square or rectangular wire. The conduction loop  320  may extend near or beyond the border of the dynamic body  310 . This maximizes the Lorentz force by increasing the strength of the magnetic field generated by the conduction loop  320 . 
     The movement elastic members  330  are elastic members that allow movement of the dynamic body  310  relative to the enclosure  301  and the magnets  350  along a longitudinal axis of the enclosure  301 . In the example of  FIG. 3B , two movement elastic members  330 A-B are shown, but more or fewer movement elastic members may be used in various embodiments. The movement elastic members  330  may be springs, gels, elastomers, or the like made of any suitable elastic material. In one embodiment, the movement elastic members  330  are metal springs (e.g., flexure springs, leaf springs, coil springs, and the like) with a high strength-to-weight ratio such as stainless steel. The movement elastic members  330 A-B may be positioned on opposite sides of the longitudinal axis of the enclosure  301  from one another, as illustrated in  FIG. 3B . This minimizes movement of the dynamic body  310  in directions other than along the longitudinal axis. For example, the movement elastic members  330  may be connected to or otherwise constrained by the dynamic body  310  at connection locations (e.g., connection points, connection areas) as shown in  FIG. 3B . The connection location of movement elastic member  330 A may be offset from the longitudinal axis in one direction, and the connection location of the movement elastic member  330 B may be offset from the longitudinal axis in another direction. 
     The conduction elastic members  340  are elastic members that allow for electrical current (e.g., drive signals, electromagnetic signals, and the like) to be transmitted to the conduction loop  320  while the dynamic body  310  is stationary and during movement. As the dynamic body  310  moves within the enclosure  301 , the conduction elastic members  340  maintain an electrical connection with both the enclosure  301  and the conduction loop  320 . The conduction elastic members  340  may be made of any suitable elastic and conductive material, such as a spring, a doped gel, an elastomer, and the like. In various embodiments, the conduction elastic members  340  are springs (e.g., flexure springs, leaf springs, coil springs, and the like) with relatively high electrical conductivity and yield strength (e.g., Cu-2Ag wire, Cu-4Ag wire, and the like). The conductivity allows for proper transmission of electrical current, including electromagnetic signals, to the conduction loop  320 , and the high yield strength allows the conduction elastic members  340  to maintain elasticity over thousands, millions, or more compression and stretching events. The conduction elastic members  340  change shape (e.g., expand and contract, deflect, and the like) as the dynamic body  310  moves within the interior volume of the enclosure, thereby maintaining the electrical connection between the conduction loop  320  and the controller. Similar to the movement elastic members  330 , the conduction elastic members  340 A-B may be positioned on opposite sides of the longitudinal axis of the enclosure  301  from one another, as illustrated in  FIG. 3B . For example, the conduction elastic members  340  may be connected to or otherwise constrained by the dynamic body  310  at connection locations (e.g., connection points, connection areas) as shown in  FIG. 3B . The connection location of conduction elastic member  340 A may be offset from the longitudinal axis in one direction, and the connection location of the conduction elastic member  340 B may be offset from the longitudinal axis in another direction. As shown in  FIG. 3B , the conduction elastic members  340  may be positioned relative to the movement elastic members  330  such that the elastic members on the same side of the dynamic body  310  (e.g., movement elastic member  330 A and conduction elastic member  340 A) are located on opposite sides of the longitudinal axis. For example, the movement elastic member  330 A may be offset from the longitudinal axis in one direction and the conduction elastic member  340 A may be offset from the longitudinal axis in another direction. 
     In one embodiment, the reaction force (e.g., spring force) of the movement elastic members  330  is significantly greater than the reaction force of the conduction elastic members  340 . For example, the reaction force of the movement elastic members  330  may be approximately 0.5-3 N/mm, and the reaction force of the conduction elastic members  340  may be approximately 0.001-0.01 N/mm. As a result, the effect of the conduction elastic members  340  on the movement of the dynamic body  310  is negligible compared to the effect of the movement elastic members  330 . 
     The magnets  350  are coupled to the enclosure  301  and generate a magnetic field within the interior volume of the enclosure  301 . The magnetic field results in a Lorentz force on the conduction loops  320  that causes the dynamic body  310  to move within the interior volume of the enclosure  301 . The magnets  350  may be any suitable magnetic mass, such as permanent magnets, electromagnets, or the like. In various embodiments, the magnets  350  are arranged in planar arrays in which adjacent magnets have alternating polarities. This causes the magnetic flux to be augmented on one side and reduced on another, and can be used to confine the magnetic flux within the interior volume of the enclosure  301  to avoid interactions with other components of the electronic device. Example magnetic arrays are discussed in more detail below with respect to  FIGS. 5A-F . 
     In operation, the actuator  300  receives an input signal (e.g., a drive signal, electromagnetic signal, or other electrical current) from a controller of the electronic device and generates a haptic output. The controller is electrically coupled to the conduction elastic members  340 , for example by a flex cable partially or entirely within the enclosure  301 . The conduction elastic members  340  convey the input signal to the conduction loop  320 . The signal energizes the conduction loop  320 , which generates a magnetic field. The interaction of this magnetic field with the magnets  350  causes a force on the conduction loop  320 , and thereby the dynamic body  310 , along an x-axis or longitudinal axis (left-to-right with reference to  FIGS. 3B and 3C ). This force causes the dynamic body  310  to move along the longitudinal axis (“linear motion”). The movement elastic members  330  constrain the movement of the dynamic body  310  by imparting a reaction force (e.g., spring force) on the dynamic body  310 . This causes the dynamic body  310  to oscillate along the longitudinal axis within the enclosure  301 . The movement of the dynamic body  310  within the enclosure  301  results in a haptic output that can be felt by a user of the electronic device. 
     Movement of the dynamic body  310  in directions other than along the longitudinal axis is possible, but in general not desired. This is because such movement results in wasted energy, thereby reducing the efficiency of the actuator  300 . Additionally, such movement can cause the dynamic body  310  to contact the enclosure  301  and other components of the actuator  300 , resulting in damage, unwanted noise, interference with haptic outputs, and the like. Various aspects of the actuator  300  constrain movement in the y-direction (top-to-bottom with reference to  FIG. 3B ), the z-direction (top-to-bottom with reference to  FIG. 3C ), or some combination of the x-, y-, and z-directions (e.g., twisting or rolling). Movement in the y- and z-directions, including translation, twisting, and rolling, is constrained by the presence of the movement elastic members on opposite sides of the longitudinal axis of the dynamic body  310 . Movement in the y-direction is additionally constrained by the relative positions of the movement elastic members  330 A and  330 B, for example diagonally across from one another as illustrated in  FIG. 3B . This positioning generally minimizes y-direction movement, including situations in which the dynamic body  310  contacts the enclosure  301 . Movement in the z-direction may be constrained by a viscous fluid damper between the dynamic body  310  and one or more of the magnets  350 , as discussed in more detail below with respect to  FIGS. 4A-4C . Additionally, physical mechanisms may constrain the movement of the dynamic body  310  in any direction. For example, stops made of an elastic material (e.g., rubber, silicone, and the like) may be placed within the enclosure to constrain movement. In another embodiment, the enclosure  301  may include one or more shafts (not pictured) that constrain the movement of the dynamic body  310 . For example, the dynamic body  310  may be disposed around a shaft that causes the dynamic body  310  to move in the x-direction. Alternatively or additionally, one or more shafts within the enclosure  301  may guide or restrict the motion of the dynamic body  310 . 
       FIG. 4A  depicts a second example construction of a haptic actuator, such as described herein. The haptic actuator  400  of  FIG. 4A  includes an enclosure  401  that defines an interior volume.  FIG. 4B  is a cross-section of the haptic actuator  400 , taken through section line C-C of  FIG. 4A . The haptic actuator  400  includes a movable body  410  (similar to the dynamic body  310  of  FIGS. 3A-3C ), electromagnetic coils  420 A-B, motion springs  430 A-B, contact springs  440 A-B, and one or more magnets (not pictured in  FIG. 4B ).  FIG. 4C  is a cross-section of the haptic actuator  400 , taken through section line D-D of  FIG. 4B .  FIG. 4C  illustrates magnets  450 A-B. 
     The haptic actuator  400  is similar to the haptic actuator  300  discussed above with respect to  FIGS. 3A-3C . In addition to the features and characteristics of the haptic actuator  300 , the haptic actuator  400  includes various additions and variations. The electromagnetic coils  420 A-B are rounded rectangular coils that are made of rectangular or square wire of any suitable conductive material (e.g., copper, nickel, gold, and the like). As used herein, the term “rounded rectangular” or “rounded rectangle” refers to a shape with straight sides and rounded corners. The rectangular coils and rectangular wire of the electromagnetic coils  420  allow for more material to fit in a smaller space, thereby helping to minimize the size of the actuator  400 . The electromagnetic coils  420  may be oriented within the enclosure  401  parallel to the magnets  450 A-B. 
     The movable body  410  includes an inner portion that is relatively thin compared to outer portions, as illustrated in  FIG. 4C . The inner portion is relatively thin so that it may be positioned between the magnets  450  while minimizing the thickness of the actuator  400 . The outer portions are thicker to add weight to the movable body  410 , the movement of which creates a stronger haptic output. 
     The motion springs  430  are flexure springs and are positioned in opposite orientations to minimize non-linear motion of the movable body  410 . The flexure springs have a general wishbone shape and flex during compression and stretching. Flexure springs provide several advantages for the actuator  400 . First, flexure springs have a high spring constant for a relatively small distance between the ends of the spring. This allows the springs to take up less space within the enclosure  401 , and in particular along the actuation axis, as illustrated in  FIG. 4B , thereby helping to minimize the size of the actuator  400 . Further, the flexure springs help to minimize the non-linear motion of the movable body  410  because they are relatively rigid in the y- and z-directions. As discussed above with respect to  FIGS. 3A-3C , minimizing non-linear motion is advantageous for the efficiency and operation of the actuator  400 . 
     The contact springs  440  are coiled wire springs with a “beehive” shape (i.e., the center of the spring is wider than the ends). This concentrates the peak stress at the center of the coil and away from the connections (e.g., solder joints) with the enclosure  401 . As a result, potential failures along the connections are mitigated, leading to increased lifespan and reliability of the actuator  400 . In one embodiment, the diameter of the spring is small (e.g., approximately 50 micrometers) to minimize the spiral spring torsion force applied to the mass by the contact springs  440 . This minimizes the unwanted movement of the movable body  410  discussed above. Similarly, each of the two contact springs  440 A and  440 B may have opposing coil directions to offset the spiral spring tension force. The contact springs  440  are constructed from a material with high conductivity for providing signals to the electromagnetic coils  420 , and high yield strength to avoid failure of the springs as a result of fatigue. Example materials include copper-silver wire (e.g., CU-2Ag or CU-4Ag), annealed or rolled HA copper foil, TPC wire, C7024-XSH foil, NKC388-USH strip, C7035-XV foil, NKT322-ESH strip, C1990-GSH foil, BF 158 strip or foil, electroformed Co—P, and Cu-0.3% Sn. 
     The contact springs  440  are connected to the enclosure by contacts  445 A and  445 B. The contacts  445  additionally constrain the movement of the contact springs  440  by opposing the spring force of the contact springs. In one embodiment, as illustrated in  FIG. 4B , a contact  445  constrains the movement of a contact spring  440  by constraining an end of the contact spring. In various embodiments, the contacts  445  are rigid members that are electrically connected to the controller, for example by flex cables or the like. 
     The haptic actuator  400  additionally includes fluid  460  that acts as a damper to help control the movement of the movable body  410 . In one embodiment, the fluid  460  is a magnetized fluid or ferrofluid. In this embodiment, the fluid  460  may direct magnetic flux toward the movable body  410  to increase the efficiency of the haptic actuator  400  by requiring a smaller input signal amplitude to achieve the same electrical current in the electromagnetic coils  420 . The ferrofluid also has the advantage of being held in place by magnetic forces from the magnet, and thus does not require additional structure or mechanisms for containment, which allows for less overall complexity, weight, and volume of the haptic actuator  400 . The fluid  460  dampens linear movement of the movable body  410  to improve the control of the linear movement. For example, the fluid  460  allows faster attenuation of oscillation, which makes possible shorter haptic output events that are more noticeable to users. Further, the fluid  460  may dampen movement in the y- and z-directions as discussed above with respect to  FIGS. 3A-3C , which improves the function and reliability of the actuator  400 . 
       FIGS. 5A-5F  depict example configurations for magnet arrays in haptic actuators, such as those described herein.  FIG. 5A  depicts a top view of an example Halbach array  510 A.  FIG. 5A  includes magnets  515 A-E, which have differing magnetic field directions as illustrated by the indicators.  FIG. 5B  depicts a side view of the Halbach array of  FIG. 5A .  FIG. 5B  also depicts the differing magnetic field directions of the adjacent magnets. The result of the arrangement of the magnets in  FIGS. 5A and 5B  is a decreased magnetic flux on the top of the array, and an increased magnetic flux on the bottom of the array. A similar array may be used as the magnets described herein to direct magnetic flux toward the conduction loops or electromagnetic coils of the haptic actuator. 
       FIG. 5C  depicts a top view of a second example Halbach array  510 C. The Halbach array  510 C is similar to the Halbach array  510 A. The Halbach array of  FIG. 5C  includes different sized magnets, such as magnets  515 F and  515 G. This has an advantage of saving space, thereby reducing the overall size of the actuator. The Halbach array  510 C includes additional magnets, such as  516 A and  516 B on the sides of the magnets  515  to further augment the magnetic flux. The Halbach array  510 C additionally includes spacers  520  to further direct the magnetic field. In one embodiment, the spacers are a non-ferrous material (e.g., aluminum). In another embodiment, the spacers are magnetic. 
       FIG. 5D  depicts a top view of a third example Halbach array  510 D. The Halbach array  510 D is similar to the Halbach array  510 C, but the smaller magnets  515  (such as  515 H and  515 I) extend between the magnets  516 , so spacers are not needed. This has the advantage of reducing the complexity and number of components of the Halbach array  510 D as compared to, for example, the Halbach array  510 C. 
       FIG. 5E  depicts a top view of a fourth example Halbach array  510 E. The Halbach array  510 E is similar to the Halbach arrays  510 C and  510 D, and includes magnets  515 , such as  515 J and  515 K, and magnets  516 , such as magnets  516 E and  516 F. The Halbach array  510 E additionally includes magnets  517 A and B, which are loop magnets which have magnetic fields in the direction away from the center of the loop. The loop magnets  517  function similarly to the separate magnets  515  and  516 , but this configuration has the advantage of reducing the number of components of the Halbach array compared to arrays  510 C and  510 D. 
       FIG. 5F  depicts a side view of a fifth example Halbach array  510 F. The Halbach array  510 F includes magnets  518 A-E with alternating magnetic field directions similar to magnets  515 A-E of  FIG. 5B . Magnets  518 A-E have triangular cross-sections, which further increases the augmentation effect on the magnetic flux compared to arrays  510 A-E.  FIG. 5G  depicts a side view of a sixth example Halbach array  510 G. The Halbach array  510 G includes magnets  519 A-E with alternating magnetic field directions similar to magnets  515 A-E of  FIG. 5B . Magnets  519 A-E have trapezoidal cross-sections, which, similar to array  510 F, further increases the augmentation effect on the magnetic flux compared to arrays  510 A-E.  FIG. 5H  depicts a side view of a sixth example Halbach array  510 H. The Halbach array  510 H includes magnets  520 A-E with alternating magnetic field directions similar to magnets  515 A-E of  FIG. 5B . Magnets  520 A-E have trapezoidal or triangular cross-sections similar to the magnets of arrays  510 F and  510 G. Similar to arrays  510 F and  510 G, the cross-section shapes further increase the augmentation effect on the magnetic flux compared to arrays  510 A-E. The magnets described above with respect to  FIGS. 5A-5H  may be any suitable magnetic mass, such as electromagnets, permanent magnets, temporary magnets, and the like. 
       FIGS. 6A-6C  depict an example configuration of capacitive sensors within a haptic actuator, such as described herein. In the example of  FIGS. 6A-6C , movable body  620  moves within enclosure  600  from a first position ( FIG. 6A ) to a second position ( FIG. 6B ) to a third position ( FIG. 6C ). The first position may be, for example, a neutral position of the movable body  620  prior to a signal being provided to generate a haptic output or a position during movement (e.g., oscillation) of the movable body  620 . The second position is a leftward position during movement of the movable body  620 . The third position is a rightward position during movement of the movable body  620 . Capacitive sensors  610 A-B and  615 A-B detect changes in capacitance based on the position or motion of the movable body  620 , which can be used to determine a relative position of the movable body  620  within the enclosure. In various embodiments, the movable body  620  acts as a capacitive plate, the motion of which results in changes in the sensed capacitance by the capacitive sensors  610  and  615 . In the example of  FIGS. 6A-6C , four capacitive sensors  610 ,  615  are employed, but in other embodiments, more or fewer sensors may be employed 
     Capacitive sensors  610  are configured to measure the position of the movable body  620  in the z-direction (into and out of the page with reference to  FIGS. 6A-6C ). During motion of the movable body  620 , the movable body continuously covers capacitive sensors  610 . As a result, the x-position (left and right with reference to  FIGS. 6A-6C ) of the movable body does not affect the capacitance detected by the capacitive sensors  610 . Accordingly, any changes in capacitance detected by the capacitive sensors  610  can be attributed to changes in the z-position of the movable body  620 . Additionally, because there are two capacitive sensors  610 A and  610 B for measuring the z-position, differences in the readings can be used to determine roll (e.g., the top edge in  FIG. 6A  is higher or lower than the bottom edge), pitch (e.g., the left edge in  FIG. 6A  is higher or lower than the right edge), and combinations thereof. This information can be relayed to the controller to adjust the signals sent to the actuator to mitigate non-linear movement. 
     Capacitive sensors  615  are configured to measure (e.g., determine) the position of the movable body  620  in the x-direction (left and right with reference to  FIGS. 6A-6C ). During motion of the movable body  620 , the border of the movable body moves over the capacitive sensors  615 . As a result, the x-position of the movable body  620  changes the capacitance detected by sensors  615 . Accordingly, changes in capacitance can be attributed to changes in the x-position of the movable body  620 . In various embodiments, the z-position changes measured by sensors  610  can be factored into the measurements by the sensors  615  to more accurately determine the x-position of the movable body  620 . Similar to above, differences in the readings between the two capacitive sensors  615 A and  615 B can be used to determine pitch, roll and combinations thereof. 
     For example, the measured capacitance of each of the four capacitive sensors  610  will be different between  FIGS. 6A and 6B  based on the position of the movable body  620 . Using four capacitive sensors  610  allows for determination of the position of the movable body in the x-direction (left to right in  FIG. 6A ), movement in the y- and z-directions, as well as “roll” (i.e., deviation from the plane) of the movable body  620 . 
       FIGS. 7A-7C  depict an example configuration of magnetic sensors within a haptic actuator such as those described herein. In the example of  FIGS. 7A-7C , movable mass  720  moves within an enclosure from a first position ( FIG. 7A ) to a second position ( FIG. 7B ) to a third position ( FIG. 7C ). The first position may be, for example, a neutral position of the movable mass  720  prior to a signal being provided to generate a haptic output or a position during movement (e.g., oscillation) of the movable mass  720 . The second position is a rightward position during compression of a spring  730  during oscillation of the movable mass  720 . The third position is a leftward position during compression of a spring  730  during oscillation of the movable mass  720 . 
     Magnets  740 ,  741  are coupled to the movable mass  720  such that they move with the movable mass. The magnets  740  may be permanent magnets, electromagnets, or the like. In the example of  FIGS. 7A-7C , two magnets  740  are shown, but more or fewer magnets may be used. The magnets  740 ,  741  may be attached to and/or protrude (partially or entirely) from an edge of the movable mass  720  as illustrated by magnets  740 A,  741 A in  FIG. 7A . The magnets  740 ,  741  may also be attached to or otherwise disposed within the movable mass  720  such that the surface of the magnets is flush with the surface of the movable mass  720 , as illustrated by magnets  740 B,  741 B in  FIG. 7B . The magnets  740  may be dipole magnets oriented opposite each other to create differing magnetic fields that can be detected by the Hall Effect sensors  750 . For example, with reference to  FIGS. 7A-7C , magnet  740 A may be oriented with a north pole facing down while magnet  740 B may be oriented with a south pole facing down such that the magnetic flux around each is different and capable of detection and differentiation. 
     Hall Effect sensors  750 ,  751  are coupled to a surface of a wall  702  within the enclosure of the haptic actuator such that the movable mass  720  and the magnets  740  move relative to the sensors  750 . The Hall Effect sensors  750  detect changes in magnetic flux caused by movement of the magnets  740 . These detected changes can be used to determine the position of the movable mass  720 . In one embodiment, as shown in  FIGS. 7A-7C , sensor  750  is located under the magnet  740  such that the magnet  740  is always above the sensor  750 , even during motion of the movable mass  720 . In this configuration, the sensor  750  primarily detects the magnetic flux of the magnet  740  and the effects of the magnet  741  are negligible. Accordingly, the motion of the movable mass  720  in the x-direction (left to right with reference to  FIGS. 7A-7C ) does not materially affect the magnetic flux detected by the sensor  750 . As a result, changes in magnetic flux detected by the sensor  750  can be attributed to changes in the z-position (up and down with reference to  FIGS. 7A-7C ) of the movable mass  720 . In contrast, as shown in  FIGS. 7A-7C , the sensor  751  is positioned such that it may be under magnet  740 , magnet  741 , or both depending on the x-position of the movable mass  720 . Because the magnets  740 ,  741  have different magnetic flux than one another, the flux detected by the sensor  751  can be used to determine the x-position of the movable mass  720 . In various embodiments, the z-position determined by the sensor  750  may be used to adjust the reading by the sensor  751  for a more accurate determination of the x-position. 
     Referring to  FIG. 7A , sensors  750 ,  751  may be attached to and/or protrude (partially or entirely) from a surface of the enclosure wall  702 A as illustrated by sensors  750 A,  751 A. Referring to  FIG. 7B , sensors  750 ,  751  may be attached to or otherwise disposed within the enclosure wall  702 B such that the surface of each sensor is flush with the surface of the enclosure wall  702 B, as illustrated by sensors  750 B,  751 B. Referring to  FIG. 7C , sensors  750 ,  751  may be disposed within a recessed area of the enclosure wall  702 C as illustrated by sensors  750 C,  751 C. 
     In the example of  FIGS. 7A-7C , Hall Effect sensors are used to measure changes in the magnetic field. In various embodiments, different types of sensors may be used in place of the sensors discussed above, including anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) sensors, and tunneling magnetoresistance (TMR) sensors. 
       FIG. 8A-8C  are cross-sections similar showing portions of example haptic actuators, such as those described herein.  FIG. 8A  is a cross-section of a first example haptic actuator  800 A. The haptic actuator  800 A includes an enclosure  801 A, a dynamic body  810 A, a conduction coil  820 A, a motion spring  830 A, a contact spring  840 A, and an electrical contact  845 A. The haptic actuator  800 A is similar in form and function to the haptic actuator  400  of  FIGS. 4A-C , but the haptic actuator  800 A has one motion spring  830 A and one contact spring  840 A instead of two.  FIG. 8B  is a cross-section of a second example haptic actuator  800 B. The haptic actuator  800 B includes a movement elastic member  830 B, which is a flexure spring that is attached at a bottom edge of the dynamic body  810 B. The attachment of the flexure spring to various surfaces of dynamic body  810 B is envisioned. Additionally, the conduction elastic member  840 B is a c-shaped elastic member such as a leaf spring. Various forms of elastic members and combinations thereof for the movement elastic members and the conduction elastic members are envisioned. Further, as illustrated in  FIGS. 8A-8C , the conduction elastic member  840 B may be attached to the contact  845 B at various locations.  FIG. 8C  is a cross-section of a second example haptic actuator  800 C. The haptic actuator  800 C includes a motion spring  830 C, which is a c-shaped spring such as a leaf spring that is attached at a bottom edge of the dynamic body  810 C. Additionally, the contact spring  840 C is a c-shaped elastic member such as a leaf spring. 
       FIG. 9  is a simplified flow chart depicting example operations of a haptic feedback system, such as described herein. The method  900  includes operation  910  in which a controller receives an instruction to provide haptic feedback, for example using a haptic actuator of an electronic device. Next, at operation  920 , the controller sends a signal to an actuator (e.g., a haptic actuator) that causes the actuator to output haptic feedback. Then, at operation  930 , the controller receives feedback from a feedback sensor associated with the actuator, which may be used to facilitate closed-loop control of the actuator. 
     As noted above, many embodiments described herein reference a haptic feedback system operated in conjunction with a portable electronic device. It may be appreciated, however, that this is merely one example; other configurations, implementations, and constructions are contemplated in view of the various principles and methods of operation—and reasonable alternatives thereto—described in reference to the embodiments described above. 
     For example, without limitation, a haptic feedback system can be additionally or alternatively associated with: a display surface, a housing or enclosure surface, a planar surface, a curved surface, an electrically conductive surface, an electrically insulating surface, a rigid surface, a flexible surface, a key cap surface, a trackpad surface, a display surface, and so on. The interface surface can be a front surface, a back surface, a sidewall surface, or any suitable surface of an electronic device or electronic device accessory. Typically, the interface surface of a multimode force interface is an exterior surface of the associated portable electronic device but this may not be required. 
     Further, although many embodiments reference a haptic feedback system in a portable electronic device (such as a cell phone or tablet computer) it may be appreciated that a haptic feedback system can be incorporated into any suitable electronic device, system, or accessory including but not limited to: portable electronic devices (e.g., battery-powered, wirelessly-powered devices, tethered devices, and so on); stationary electronic devices; control devices (e.g., home automation devices, industrial automation devices, aeronautical or terrestrial vehicle control devices, and so on); personal computing devices (e.g., cellular devices, tablet devices, laptop devices, desktop devices, and so on); wearable devices (e.g., implanted devices, wrist-worn devices, eyeglass devices, and so on); accessory devices (e.g., protective covers such as keyboard covers for tablet computers, stylus input devices, charging devices, and so on); and so on. 
     Although specific electronic devices are shown in the figures and described herein, the haptic actuators described herein may be used with various electronic devices, mechanical devices, electromechanical devices and so on. Examples of such include, but are not limited to, mobile phones, personal digital assistants, time keeping devices, health monitoring devices, wearable electronic devices, input devices (e.g., a stylus, trackpads, buttons, switches, and so on), a desktop computer, electronic glasses, steering wheels, dashboards, bands for a wearable electronic device, and so on. Although various electronic devices are mentioned, the haptic actuators and linear actuators disclosed herein may also be used in conjunction with other products and combined with various materials. 
     One may appreciate that although many embodiments are disclosed above, that the operations and steps presented with respect to methods and techniques described herein are meant as exemplary and accordingly are not exhaustive. One may further appreciate that alternate step order or fewer or additional operations may be required or desired for particular embodiments. 
     Although the disclosure above is described in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the some embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but is instead defined by the claims herein presented.

Metadata:
Filing Date: 20170330
Publication Date: 20180724
Grant Date: 20180724
Priority Date: 20170330
Inventors: ZHANG, ZHIPENG
KOCH, RICHARD H.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01F7/066", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/064", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/1646", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F7/1646", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F2007/185", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0017", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/0205", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/1646", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F2007/185", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01F7/064", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F7/066", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 62874108