Patent Publication Number: US-2023161413-A1

Title: Integrated haptic system

Description:
RELATED APPLICATION 
     The present disclosure claims priority to U.S. Provisional Patent Application Ser. No. 62/503,163, filed May 8, 2017, and U.S. Provisional Patent Application Ser. No. 62/540,921, filed Aug. 3, 2017, both of which are incorporated by reference herein in their entirety. 
    
    
     FIELD OF DISCLOSURE 
     The present disclosure relates in general to electronic devices with user interfaces, (e.g., mobile devices, game controllers, instrument panels, etc.), and more particularly, an integrated haptic system for use in a system for mechanical button replacement in a mobile device, for use in haptic feedback for capacitive sensors, and/or other suitable applications. 
     BACKGROUND 
     Linear resonant actuators (LRAs) and other vibrational actuators (e.g., rotational actuators, vibrating motors, etc.) are increasingly being used in mobile devices (e.g., mobile phones, personal digital assistants, video game controllers, etc.) to generate vibrational feedback for user interaction with such devices. Typically, a force/pressure sensor detects user interaction with the device (e.g., a finger press on a virtual button of the device) and in response thereto, the linear resonant actuator vibrates to provide feedback to the user. For example, a linear resonant actuator may vibrate in response to force to mimic to the user the feel of a mechanical button click. 
     One disadvantage of existing haptic systems is that existing approaches to processing of signals of a force sensor and generating of a haptic response thereto often have longer than desired latency, such that the haptic response may be significantly delayed from the user&#39;s interaction with the force sensor. Thus, in applications in which a haptic system is used for mechanical button replacement, capacitive sensor feedback, or other application, and the haptic response may not effectively mimic the feel of a mechanical button click. Accordingly, systems and methods that minimize latency between a user&#39;s interaction with a force sensor and a haptic response to the interaction are desired. 
     In addition, to create appropriate and pleasant haptic feelings for a user, a signal driving a linear resonant actuator may need to be carefully designed and generated. In mechanical button replacement application, a desirable haptic response may be one in which the vibrational impulse generated by the linear resonant actuator should be strong enough to give a user prominent notification as a response to his/her finger pressing and/or releasing, and the vibrational impulse should be short, fast, and clean from resonance tails to provide a user a “sharp” and “crisp” feeling. Optionally, different control algorithms and stimulus may be applied to a linear resonant actuator, to alter the performance to provide alternate tactile feedback—possibly denoting certain user modes in the device—giving more “soft” and “resonant” tactile responses. 
     SUMMARY 
     In accordance with the teachings of the present disclosure, the disadvantages and problems associated with haptic feedback in a mobile device may be reduced or eliminated. 
     In accordance with embodiments of the present disclosure, an integrated haptic system may include a digital signal processor and an amplifier communicatively coupled to the digital signal processor and integrated with the digital signal processor into the integrated haptic system. The digital signal processor may be configured to receive an input signal indicative of a force applied to a force sensor and generate a haptic playback signal responsive to the input signal. The amplifier may be configured to amplify the haptic playback signal and drive a vibrational actuator communicatively coupled to the amplifier with the haptic playback signal as amplified by the amplifier. 
     In accordance with these and other embodiments of the present disclosure, a method may include receiving, by a digital signal processor, an input signal indicative of a force applied to a force sensor. The method may also include generating, by the digital signal processor, a haptic playback signal responsive to the input signal. The method may further include driving, with an amplifier communicatively coupled to the digital signal processor and integrated with the digital signal processor into an integrated haptic system, the haptic playback signal as amplified by the amplifier. 
     In accordance with these and other embodiments of the present disclosure, an article of manufacture may include a non-transitory computer-readable medium computer-executable instructions carried on the computer-readable medium, the instructions readable by a processor, the instructions, when read and executed, for causing the processor to receive an input signal indicative of a force applied to a force sensor and generate a haptic playback signal responsive to the input signal, such that an amplifier communicatively coupled to the processor and integrated with the digital signal processor into an integrated haptic system, amplifies and drives the haptic playback signal. 
     Technical advantages of the present disclosure may be readily apparent to one having ordinary skill in the art from the figures, description and claims included herein. The objects and advantages of the embodiments will be realized and achieved at least by the elements, features, and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are examples and explanatory and are not restrictive of the claims set forth in this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG.  1    illustrates a block diagram of selected components of an example mobile device, in accordance with embodiments of the present disclosure; 
         FIG.  2    illustrates a block diagram of selected components of an example integrated haptic system, in accordance with embodiments of the present disclosure; 
         FIG.  3    illustrates a block diagram of selected components of an example processing system for use in the integrated haptic system of  FIG.  2   , in accordance with embodiments of the present disclosure; 
         FIG.  4    illustrates a block diagram of selected components of another example integrated haptic system, in accordance with embodiments of the present disclosure; 
         FIG.  5    illustrates a graph showing example waveforms of haptic driving signals that may be generated, in accordance with embodiments of the present disclosure; 
         FIG.  6    illustrates a graph depicting an example transfer function of displacement of linear resonant actuator as a function of frequency at a voltage level equal to a maximum static excursion occurring at low frequencies, in accordance with embodiments of the present disclosure; 
         FIG.  7    illustrates a graph depicting an example transfer function of acceleration of linear resonant actuator as a function of frequency and a maximum acceleration at maximum excursion, in accordance with embodiments of the present disclosure; 
         FIG.  8    illustrates a block diagram of selected components of another example integrated haptic system, in accordance with embodiments of the present disclosure; 
         FIG.  9    illustrates a block diagram of selected components of another example integrated haptic system, in accordance with embodiments of the present disclosure; 
         FIG.  10    illustrates a block diagram of selected components of another example integrated haptic system, in accordance with embodiments of the present disclosure; and 
         FIG.  11    illustrates a block diagram of selected components of another example integrated haptic system, in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a block diagram of selected components of an example mobile device  102 , in accordance with embodiments of the present disclosure. As shown in  FIG.  1   , mobile device  102  may comprise an enclosure  101 , a controller  103 , a memory  104 , a force sensor  105 , a microphone  106 , a linear resonant actuator  107 , a radio transmitter/receiver  108 , a speaker  110 , and an integrated haptic system  112 . 
     Enclosure  101  may comprise any suitable housing, casing, or other enclosure for housing the various components of mobile device  102 . Enclosure  101  may be constructed from plastic, metal, and/or any other suitable materials. In addition, enclosure  101  may be adapted (e.g., sized and shaped) such that mobile device  102  is readily transported on a person of a user of mobile device  102 . Accordingly, mobile device  102  may include but is not limited to a smart phone, a tablet computing device, a handheld computing device, a personal digital assistant, a notebook computer, a video game controller, or any other device that may be readily transported on a person of a user of mobile device  102 . 
     Controller  103  may be housed within enclosure  101  and may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data, and may include, without limitation a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and/or execute program instructions and/or process data. In some embodiments, controller  103  interprets and/or executes program instructions and/or processes data stored in memory  104  and/or other computer-readable media accessible to controller  103 . 
     Memory  104  may be housed within enclosure  101 , may be communicatively coupled to controller  103 , and may include any system, device, or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). Memory  104  may include random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), a Personal Computer Memory Card International Association (PCMCIA) card, flash memory, magnetic storage, opto-magnetic storage, or any suitable selection and/or array of volatile or non-volatile memory that retains data after power to mobile device  102  is turned off. 
     Microphone  106  may be housed at least partially within enclosure  101 , may be communicatively coupled to controller  103 , and may comprise any system, device, or apparatus configured to convert sound incident at microphone  106  to an electrical signal that may be processed by controller  103 , wherein such sound is converted to an electrical signal using a diaphragm or membrane having an electrical capacitance that varies as based on sonic vibrations received at the diaphragm or membrane. Microphone  106  may include an electrostatic microphone, a condenser microphone, an electret microphone, a microelectromechanical systems (MEMS) microphone, or any other suitable capacitive microphone. 
     Radio transmitter/receiver  108  may be housed within enclosure  101 , may be communicatively coupled to controller  103 , and may include any system, device, or apparatus configured to, with the aid of an antenna, generate and transmit radio-frequency signals as well as receive radio-frequency signals and convert the information carried by such received signals into a form usable by controller  103 . Radio transmitter/receiver  108  may be configured to transmit and/or receive various types of radio-frequency signals, including without limitation, cellular communications (e.g., 2G, 3G, 4G, LTE, etc.), short-range wireless communications (e.g., BLUETOOTH), commercial radio signals, television signals, satellite radio signals (e.g., GPS), Wireless Fidelity, etc. 
     A speaker  110  may be housed at least partially within enclosure  101  or may be external to enclosure  101 , may be communicatively coupled to controller  103 , and may comprise any system, device, or apparatus configured to produce sound in response to electrical audio signal input. In some embodiments, a speaker may comprise a dynamic loudspeaker, which employs a lightweight diaphragm mechanically coupled to a rigid frame via a flexible suspension that constrains a voice coil to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it a variable electromagnet. The coil and the driver&#39;s magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical signal coming from the amplifier. 
     Force sensor  105  may be housed within enclosure  101 , and may include any suitable system, device, or apparatus for sensing a force, a pressure, or a touch (e.g., an interaction with a human finger) and generating an electrical or electronic signal in response to such force, pressure, or touch. In some embodiments, such electrical or electronic signal may be a function of a magnitude of the force, pressure, or touch applied to the force sensor. In these and other embodiments, such electronic or electrical signal may comprise a general purpose input/output signal (GPIO) associated with an input signal to which haptic feedback is given (e.g., a capacitive touch screen sensor or other capacitive sensor to which haptic feedback is provided). For purposes of clarity and exposition in this disclosure, the term “force” as used herein may refer not only to force, but to physical quantities indicative of force or analogous to force, such as, but not limited to, pressure and touch. 
     Linear resonant actuator  107  may be housed within enclosure  101 , and may include any suitable system, device, or apparatus for producing an oscillating mechanical force across a single axis. For example, in some embodiments, linear resonant actuator  107  may rely on an alternating current voltage to drive a voice coil pressed against a moving mass connected to a spring. When the voice coil is driven at the resonant frequency of the spring, linear resonant actuator  107  may vibrate with a perceptible force. Thus, linear resonant actuator  107  may be useful in haptic applications within a specific frequency range. While, for the purposes of clarity and exposition, this disclosure is described in relation to the use of linear resonant actuator  107 , it is understood that any other type or types of vibrational actuators (e.g., eccentric rotating mass actuators) may be used in lieu of or in addition to linear resonant actuator  107 . In addition, it is also understood that actuators arranged to produce an oscillating mechanical force across multiple axes may be used in lieu of or in addition to linear resonant actuator  107 . As described elsewhere in this disclosure, a linear resonant actuator  107 , based on a signal received from integrated haptic system  112 , may render haptic feedback to a user of mobile device  102  for at least one of mechanical button replacement and capacitive sensor feedback. 
     Integrated haptic system  112  may be housed within enclosure  101 , may be communicatively coupled to force sensor  105  and linear resonant actuator  107 , and may include any system, device, or apparatus configured to receive a signal from force sensor  105  indicative of a force applied to mobile device  102  (e.g., a force applied by a human finger to a virtual button of mobile device  102 ) and generate an electronic signal for driving linear resonant actuator  107  in response to the force applied to mobile device  102 . Detail of an example integrated haptic system in accordance with embodiments of the present disclosure is depicted in  FIG.  2   . 
     Although specific example components are depicted above in  FIG.  1    as being integral to mobile device  102  (e.g., controller  103 , memory  104 , force sensor  105 , microphone  106 , radio transmitter/receiver  108 , speakers(s)  110 ), a mobile device  102  in accordance with this disclosure may comprise one or more components not specifically enumerated above. For example, although  FIG.  1    depicts certain user interface components, mobile device  102  may include one or more other user interface components in addition to those depicted in  FIG.  1    (including but not limited to a keypad, a touch screen, and a display), thus allowing a user to interact with and/or otherwise manipulate mobile device  102  and its associated components. 
       FIG.  2    illustrates a block diagram of selected components of an example integrated haptic system  112 A, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 A may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  2   , integrated haptic system  112 A may include a digital signal processor (DSP)  202 , a memory  204 , and an amplifier  206 . 
     DSP  202  may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data. In some embodiments, DSP  202  may interpret and/or execute program instructions and/or process data stored in memory  204  and/or other computer-readable media accessible to DSP  202 . 
     Memory  204  may be communicatively coupled to DSP  202 , and may include any system, device, or apparatus configured to retain program instructions and/or data for a period of time (e.g., computer-readable media). Memory  204  may include random access memory (RAM), electrically erasable programmable read-only memory (EEPROM), a Personal Computer Memory Card International Association (PCMCIA) card, flash memory, magnetic storage, opto-magnetic storage, or any suitable selection and/or array of volatile or non-volatile memory that retains data after power to mobile device  102  is turned off. 
     Amplifier  206  may be electrically coupled to DSP  202  and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT . For example, amplifier  206  may use electric power from a power supply (not explicitly shown) to increase the amplitude of a signal. Amplifier  206  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     In operation, memory  204  may store one or more haptic playback waveforms. In some embodiments, each of the one or more haptic playback waveforms may define a haptic response a(t) as a desired acceleration of a linear resonant actuator (e.g., linear resonant actuator  107 ) as a function of time. DSP  202  may be configured to receive a force signal V SENSE  from force sensor  105  indicative of force applied to force sensor  105 . Either in response to receipt of force signal V SENSE  indicating a sensed force or independently of such receipt, DSP  202  may retrieve a haptic playback waveform from memory  204  and process such haptic playback waveform to determine a processed haptic playback signal V IN . In embodiments in which amplifier  206  is a Class D amplifier, processed haptic playback signal V IN  may comprise a pulse-width modulated signal. In response to receipt of force signal V SENSE  indicating a sensed force, DSP  202  may cause processed haptic playback signal V IN  to be output to amplifier  206 , and amplifier  206  may amplify processed haptic playback signal V IN  to generate a haptic output signal V OUT  for driving linear resonant actuator  107 . Detail of an example processing system implemented by DSP  202  is depicted in  FIG.  3   . 
     In some embodiments, integrated haptic system  112 A may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. By providing integrated haptic system  112 A as part of a single monolithic integrated circuit, latencies between various interfaces and system components of integrated haptic system  112 A may be reduced or eliminated. 
     As shown in  FIG.  3   , DSP  202  may receive diagnostic inputs from which processing system  300  may monitor and adjust operation of amplifier  206  in response thereto. For example, as discussed below with respect to  FIG.  3   , DSP  202  may receive measurements from linear resonant actuator  107  to estimate the vibrational transfer function of linear resonant actuator  107 . However, in some embodiments, DSP  202  may receive and monitor one or more other diagnostic inputs, and DSP  202  may control operation of amplifier  206  in response thereto. For example, in some embodiments, DSP  202  may monitor a current level associated with linear resonant actuator  107  and/or a voltage level associated with linear resonant actuator  107 . From such measurements, DSP  202  may be able to infer or calculate a status (e.g., status of motion) of linear resonant actuator  107 . For example, from a monitored voltage and current, DSP  202  may be able to employ a mathematical model of linear resonant actuator  107  to estimate a displacement, velocity, and/or acceleration of linear resonant actuator  107 . As another example, DSP  202  may inject a high-frequency signal into linear resonant actuator  107  and infer an inductance of linear resonant actuator  107  based on the current and/or voltage responses of linear resonant actuator  107  to the injected signal. From the inductance, DSP  202  may be able to estimate a displacement of linear resonant actuator  107 . Based on determined status information (e.g., displacement, velocity, and/or acceleration), DSP  202  may control processed haptic playback signal V IN  for any suitable purpose, including protecting linear resonant actuator  107  from over-excursion that could lead to damage to linear resonant actuator  107  or other components of mobile device  102 . As yet another example, one or more diagnostic inputs may be monitored to determine an operational drift of linear resonant actuator  107 , and DSP  202  may control amplifier  206  and/or processed haptic playback signal V IN  in order to account for the operational drift. As a further example, one or more diagnostic inputs may be monitored to determine temperature effects of linear resonant actuator  107  (e.g., thermally induced changes in the performance of linear resonant actuator  107 ), and DSP  202  may control amplifier  206  and/or processed haptic playback signal V IN  in order to account for the temperature effects. 
       FIG.  3    illustrates a block diagram of selected components of an example processing system  300  implemented by DSP  202 , in accordance with embodiments of the present disclosure. As shown in  FIG.  3   , processing system  300  may include vibrational pulse processing  302 , regulated inversion  304 , click-driving pulse processing  306 , a comparator  308 , and vibrational transfer function estimation  310 . In operation, vibrational pulse processing  302  may receive a haptic playback waveform a(t) (or relevant parameters of such a waveform such as frequency and duration) and process such waveform to generate an intermediate signal a 1 (t). Processing performed by vibrational pulse processing  302  may include, without limitation, filtering (e.g., band-pass filtering) for frequency bands of interest, equalization of haptic playback waveform a(t) to obtain a desired spectral shape, and/or temporal truncation or extrapolation of haptic playback waveform a(t). By adjusting or tuning the temporal duration and frequency envelope of haptic playback waveform a(t), various haptic feelings as perceived by a user and/or audibility of the haptic response may be achieved. 
     Regulated inversion  304  may apply an inverse transfer function ITF to intermediate signal a 1 (t), either in the frequency domain or equivalently in the time domain through inverse filtering. Such inverse transfer function ITF may be generated from vibrational transfer function estimation  310  based on actual vibrational measurements of linear resonant actuator  107  and/or model parameters of linear resonant actuator  107 . Inverse transfer function ITF may be the inverse of a transfer function that correlates output voltage signal V OUT  to actual acceleration of linear resonant actuator  107 . By applying inverse transfer function ITF to intermediate signal a 1 (t), regulated inversion  304  may generate an inverted vibration signal V INT  in order to apply inversion to specific target vibrational click pulses to obtain an approximation of certain desired haptic click signals to drive the vibrational actuators for the generation of haptic clicks. In embodiments in which inverse transfer function ITF is calculated based on measurements of linear resonant actuator  107 , processing system  300  may implement a closed-loop feedback system for generating output signal V OUT , such that processing system  300  may track vibrational characteristics of linear resonant actuator  107  over the lifetime of linear resonant actuator  107  to enable more accurate control of the haptic response generated by integrated haptic system  112 A. 
     In some embodiments, processing system  300  may not employ an adaptive inverse transfer function ITF, and instead apply a fixed inverse transfer function ITF. In yet other embodiments, the haptic playback waveforms a(t) stored in memory  204  may already include waveforms already adjusted by a fixed inverse transfer function ITF, in which case processing system  300  may not include blocks  302  and  304 , and haptic playback waveforms a(t) may be fed directly to click-driving pulse processing block  306 . 
     Click-driving pulse processing  306  may receive inverted vibration signal V INT  and control resonant tail suppression of inverted vibration signal V INT  in order to generate processed haptic playback signal V IN . Processing performed by click-driving pulse processing  306  may include, without limitation, truncation of inverted vibration signal V INT , minimum phase component extraction for inverted vibration signal V INT , and/or filtering to control audibility of haptic playback signal V IN . 
     Comparator  308  may compare a digitized version of force signal V SENSE  to a signal threshold V TH  related to a threshold force, and responsive to force signal V SENSE  exceeding signal threshold V TH , may enable haptic playback signal V IN  to be communicated to amplifier  206 , such that amplifier  206  may amplify haptic playback signal V IN  to generate output signal V OUT . 
     Although  FIG.  3    depicts comparator  308  as a simple analog comparator, in some embodiments, comparator  308  may include more detailed logic and/or comparison than shown in  FIG.  3   , with the enable signal ENABLE output by comparator  308  depending on one or more factors, parameters, and/or measurements in addition to or in lieu of comparison to a threshold force level. 
     In addition, although  FIG.  3    depicts enable signal ENABLE being communicated to click-driving pulse processing  306  and selectively enabling/disabling haptic playback signal V IN , in other embodiments, ENABLE signal ENABLE may be communicated to another component of processing system  300  (e.g., vibrational pulse processing  302 ) in order to enable, disable, or otherwise condition an output of such other component. 
       FIG.  4    illustrates a block diagram of selected components of an example integrated haptic system  112 B, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 B may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  4   , integrated haptic system  112 B may include a digital signal processor (DSP)  402 , an amplifier  406 , an analog-to-digital converter (ADC)  408 , and an ADC  410 . 
     DSP  402  may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data. In some embodiments, DSP  402  may interpret and/or execute program instructions and/or process data stored in a memory and/or other computer-readable media accessible to DSP  402 . As shown in  FIG.  4   , DSP  402  may implement a prototype tonal signal generator  414 , nonlinear shaping block  416 , a smoothing block  418 , and a velocity estimator  420 . 
     Prototype tonal signal generator  414  may be configured to generate a tonal driving signal a(t) at or near a resonance frequency f 0  of linear resonant actuator  107 , and monitors an estimated velocity signal VEL generated by velocity estimator  420  to determine an occurrence of a predefined threshold level for estimated velocity signal VEL or for an occurrence of a peak of estimated velocity signal VEL. At the occurrence of the predefined threshold level or peak, prototype tonal signal generator  414  may then cause a change of polarity of driving signal a(t), which in turn may cause a moving mass of linear resonant actuator  107  to experience a sudden change in velocity, creating a large acceleration in linear resonant actuator  107 , resulting in a sharp haptic feeling. Driving signal a(t) generated by prototype tonal signal generator  414  may be followed by nonlinear shaping block  416  that shapes the waveform driving signal a(t) for a more efficient utilization of a driving voltage, and may be further smoothed by smoothing block  418  to generate input voltage V IN . 
     Velocity estimator  420  may be configured to, based on a measured voltage V MON  of linear resonant actuator  107 , a measured current I MON  of linear resonant actuator  107 , and known characteristics of linear resonant actuator  107  (e.g., modeling of a velocity of linear resonant actuator  107  as a function of voltage and current of linear resonant actuator  107 ), calculate an estimated velocity VEL of linear resonant actuator  107 . In some embodiments, one or more other measurements or characteristics associated with linear resonant actuator  107  (e.g., inductance) may be used in addition to or in lieu of a measured voltage and measured current in order to calculate estimated velocity VEL. 
     Amplifier  406  may be electrically coupled to DSP  402  and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT  For example, amplifier  406  may use electric power from a power supply (e.g., a boost power supply, not explicitly shown) to increase the amplitude of a signal. Amplifier  406  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     ADC  408  may comprise any suitable system, device, or apparatus configured to convert an analog current associated with linear resonant actuator  107  into a digitally equivalent measured current signal I MON . Similarly, ADC  410  may comprise any suitable system, device, or apparatus configured to convert an analog voltage across sense resistor  412  (having a voltage indicative of an analog current associated with linear resonant actuator  107 ) into a digitally equivalent measured voltage signal V MON . 
     In some embodiments, integrated haptic system  112 B may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. 
       FIG.  5    illustrates a graph depicting example waveforms of haptic driving signals that may be generated, in accordance with embodiments of the present disclosure. For example, as shown in  FIG.  5   , prototype tonal signal generator  414  may generate a tonal acceleration signal a(t) which begins at resonant frequency f 0  and ends at a higher frequency with an average frequency f 1  shown in  FIG.  5   . Such average frequency f 1  may be chosen to be a frequency of tone that achieved a maximum acceleration level that avoids clipping of output voltage V OUT . To illustrate, the maximum achievable vibration of linear resonant actuator  107 , in terms of acceleration, may be restricted. As an example, linear resonant actuator  107  may be subject to an excursion limit, which defines a maximum displacement (e.g., in both a positive and negative direction) that a moving mass of linear resonant actuator  107  may displace without contacting non-moving parts of a device including linear resonant actuator  107  or otherwise causing audible buzzing and/or rattling distortions. 
       FIG.  6    illustrates a graph depicting an example transfer function of displacement of linear resonant actuator  107  as a function of frequency (x(f)) at a voltage level equal to a maximum static excursion x MAX  occurring at low frequencies, in accordance with embodiments of the present disclosure. It is apparent from the graph of  FIG.  6    that linear resonant actuator  107  may not be able to tolerate such a voltage level, because at resonance frequency f 0 , the excursion x(f) it generates will be over static excursion limit x MAX  and therefore cause clipping. In that sense, static excursion limit x MAX  may be considered the “clipping-free” excursion limit. 
       FIG.  7    illustrates a graph depicting an example transfer function of acceleration of linear resonant actuator  107  as a function of frequency (a(f)) and a maximum acceleration a MAX  at maximum excursion x MAX , in accordance with embodiments of the present disclosure. In many respects,  FIG.  7    is a translation of  FIG.  6    from the displacement domain to the acceleration domain. From  FIG.  7   , it is seen that, below a certain frequency f 1 , the maximum acceleration level linear resonant actuator  107  may generate may be restricted by the clipping-free excursion limit, and not by a voltage of amplifier  406 . This means that below the certain frequency f 1 , linear resonant actuator  107  needs to be driven at an attenuated voltage level. On the other hand, for such a maximum voltage level that nearly reaches a maximum excursion limit x MAX  without clipping, the maximum achievable clipping-free acceleration level a MAX  is achievable not at a resonance frequency f 0 , but at a chosen frequency f 1 , which is above resonance. 
     Such chosen frequency f 1  may provide a good choice of initialization for the design of haptic clicks and for the timing (e.g., a passage of time T1, as shown in  FIG.  3   ) of the change in polarity of the acceleration signal a(t) to achieve an acceleration peak. However, in addition to the specific example of a very short pulse described above, other examples of waveforms with longer cycles may be used, as well as other logics to determine a passage of time T1 (e.g., time T1) for changing polarity of the acceleration signal a(t), the effect of which is to force the moving mass to rapidly change velocity and generate a large acceleration peak. The larger the change rate of velocity, the higher the acceleration peak linear resonant actuator  107  may create. 
       FIG.  8    illustrates a block diagram of selected components of another example integrated haptic system  112 C, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 C may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  8   , integrated haptic system  112 C may include a detector  808  and an amplifier  806 . 
     Detector  808  may include any system, device, or apparatus configured to detect a signal (e.g., V SENSE ) indicative of a force. In some embodiments, such signal may be a signal generated by a force sensor. In other embodiments, such signal may comprise a GPIO signal indicative of a force applied to a force sensor. In some embodiments, detector  808  may simply detect whether GPIO signal is asserted or deasserted. In other embodiments, signal V SENSE  may indicate a magnitude of force applied and may apply logic (e.g., analog-to-digital conversion where signal V SENSE  is analog, comparison to a threshold force level, and/or logic associated with other measurements or parameters). In any event, responsive to signal V SENSE  indicating a requisite force, detector  808  may enable amplifier  806  (e.g., by enabling its power supply or power supply boost mode) such that amplifier  806  may amplify haptic playback signal V IN  (which may be generated by a component internal to or external to integrated haptic system  112 C) to generate output signal V OUT . Accordingly, amplifier  806  may be maintained in a low-power or inactive state until a requisite input signal is received by integrated haptic system  112 C, at which amplifier may be powered up or effectively switched on. Allowing for amplifier  806  to be kept in a low-power or inactive state until a requisite input is received may result in a considerable reduction in power consumption of a circuit, and enable “always-on” functionality for a device incorporating integrated haptic system  112 C. 
     In alternative embodiments, detector  808  may be configured to, responsive to a requisite signal V SENSE , enable haptic playback signal V IN  to be communicated to amplifier  806 , such that amplifier  806  may amplify haptic playback signal V IN  to generate output signal V OUT . 
     In some embodiments, all or a portion of detector  808  may be implemented by a DSP. 
     Amplifier  806  may be electrically coupled to detector  808  and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT . For example, amplifier  806  may use electric power from a power supply (not explicitly shown) to increase the amplitude of a signal. Amplifier  806  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     In some embodiments, integrated haptic system  112 C may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. 
       FIG.  9    illustrates a block diagram of selected components of an example integrated haptic system  112 D, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 D may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  9   , integrated haptic system  112 D may include a digital signal processor (DSP)  902 , an amplifier  906 , and an applications processor interface  908 . 
     DSP  902  may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data. In some embodiments, DSP  902  may interpret and/or execute program instructions and/or process data stored in a memory and/or other computer-readable media accessible to DSP  902 . 
     Amplifier  906  may be electrically coupled to DSP  902  and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT . For example, amplifier  906  may use electric power from a power supply (not explicitly shown) to increase the amplitude of a signal. Amplifier  906  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     Applications processor interface  908  may be communicatively coupled to DSP  902  and an applications processor (e.g., controller  103  of  FIG.  1   ) external to integrated haptic system  112 D. Accordingly, applications processor interface  908  may enable communication between integrated haptic system  112 D and an application executing on an applications processor. 
     In some embodiments, integrated haptic system  112 D may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. 
     In operation, DSP  902  may be configured to receive a force signal V SENSE  from force sensor  105  indicative of force applied to force sensor  105 . In response to receipt of force signal V SENSE  indicating a sensed force, DSP  902  may generate a haptic playback signal V IN  and communicate haptic playback signal V IN  to amplifier  906 . In addition, in response to the receipt of force signal V SENSE  indicating a sensed force, DSP  902  may communicate an activity notification to an appropriate applications processor via applications processor interface  908 . DSP  902  may further be configured to receive communications from an applications processor via applications processor interface  908  and generate (in addition to and in lieu of generation responsive to receipt of force signal V SENSE ) haptic playback signal V IN  and communicate haptic playback signal V IN  to amplifier  906 . 
     As the output for an initial haptic feedback response can be generated by the integrated haptic system  112 D, integrated haptic system  112 D may be configured to provide a low-latency response time for the generation of immediate haptic feedback. Subsequent to the initial feedback being generated, the control of additional haptic feedback signals may be determined by a separate applications processor arranged to interface with integrated haptic system  112 D. By offloading the control of subsequent haptic driver signals to a separate applications processor, integrated haptic system  112 D may be optimized for low-power, low-latency performance, to generate the initial haptic feedback response. The initial output signal V OUT  may be provided at a relatively low resolution, resulting in the generation of a relatively simplified haptic feedback response. For example, the initial output signal V OUT  may be provided as a globalized feedback response. Subsequent to the initial response, the applications processor may be used to generate more detailed haptic feedback outputs, for example providing for localized haptic feedback responses, which may require increased processing resources when compared with the relatively straightforward generation of a globalized haptic feedback response. 
     As another example, in an effort to minimize the power consumption of mobile device  102  for always-on operation, the integrated haptic system  112 D may be configured to monitor a single input from a single force-sensing transducer (e.g., force sensor  105 ) to detect a user input. However, once an initial user input has been detected, the power and resources of an applications processor may be used to provide more detailed signal analysis and response. The applications processor may be configured to receive input signals from multiple force-sensing transducers, and/or to generate output signals for multiple haptic transducers. 
       FIG.  10    illustrates a block diagram of selected components of an example integrated haptic system  112 E, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 E may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  10   , integrated haptic system  112 E may include a digital signal processor (DSP)  1002 , an amplifier  1006 , and a signal combiner  1008 . 
     DSP  1002  may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data. In some embodiments, DSP  1002  may interpret and/or execute program instructions and/or process data stored in a memory and/or other computer-readable media accessible to DSP  1002 . 
     Amplifier  1006  may be electrically coupled to DSP  1002  (e.g., via signal combiner  1008 ) and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT . For example, amplifier  1006  may use electric power from a power supply (not explicitly shown) to increase the amplitude of a signal Amplifier  1006  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     Signal combiner  1008  may be interfaced between DSP  1002  and amplifier  1006  and may comprise any system, device, or apparatus configured to combine a signal generated by DSP  1002  and a vibration alert signal received from a component external to integrated haptic system  112 E. 
     In some embodiments, integrated haptic system  112 E may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. 
     In operation, DSP  1002  may be configured to receive a force signal V SENSE  from force sensor  105  indicative of force applied to force sensor  105 . In response to receipt of force signal V SENSE  indicating a sensed force, DSP  1002  may generate an intermediate haptic playback signal V INT . Signal combiner  1008  may receive intermediate haptic playback signal V INT  and mix intermediate haptic playback signal V INT  with another signal (e.g., the vibration alert signal) received by integrated haptic system  112 E to generate a haptic playback signal V IN  and communicate haptic playback signal V IN  to amplifier  1006 . Accordingly, a haptic signal generated responsive to a force (e.g., intermediate haptic playback signal V INT ) may be mixed with a further signal (e.g., the vibration alert signal), to provide a composite signal (e.g., haptic playback signal V IN ) for linear resonant actuator  107 . For example, the signal to generate a pure haptic feedback response may be mixed with a signal used to generate a vibratory notification or alert, for example as notification of an incoming call or message. Such mixing would allow for a user to determine that an alert has been received at the same time as feeling a haptic feedback response. As shown in  FIG.  10   , signal combiner  1008  may perform mixing on an input signal used as input to the amplifier  1006 . However, in other embodiments, a signal combiner may perform mixing on an output signal for driving linear resonant actuator  107 . 
       FIG.  11    illustrates a block diagram of selected components of an example integrated haptic system  112 F, in accordance with embodiments of the present disclosure. In some embodiments, integrated haptic system  112 F may be used to implement integrated haptic system  112  of  FIG.  1   . As shown in  FIG.  11   , integrated haptic system  112 F may include a digital signal processor (DSP)  1102 , a detector  1104 , an amplifier  1106 , a sampling control  1108 , and a sensor bias generator  1112 . 
     DSP  1102  may include any system, device, or apparatus configured to interpret and/or execute program instructions and/or process data. In some embodiments, DSP  1102  may interpret and/or execute program instructions and/or process data stored in a memory and/or other computer-readable media accessible to DSP  1102 . 
     Detector  1104  may include any system, device, or apparatus configured to detect a signal (e.g., V SENSE ) indicative of a force. In some embodiments, such signal may be a signal generated by a force sensor. In other embodiments, such signal may comprise a GPIO signal indicative of a force applied to a force sensor. In some embodiments, detector  1104  may simply detect whether GPIO signal is asserted or deasserted. In other embodiments, signal V SENSE  may indicate a magnitude of force applied and may apply logic (e.g., analog-to-digital conversion where signal V SENSE  is analog, comparison to a threshold force level, and/or logic associated with other measurements or parameters). In any event, responsive to signal V SENSE  indicating a requisite force, detector  1104  may communicate one or more signals to DSP  1102  indicative of signal V SENSE  In some embodiments, all or a portion of detector  1104  may be implemented by DSP  1102 . 
     Amplifier  1106  may be electrically coupled to DSP  1102  and may comprise any suitable electronic system, device, or apparatus configured to increase the power of an input signal V IN  (e.g., a time-varying voltage or current) to generate an output signal V OUT . For example, amplifier  1106  may use electric power from a power supply (not explicitly shown) to increase the amplitude of a signal. Amplifier  1106  may include any suitable amplifier class, including without limitation, a Class-D amplifier. 
     Sampling control  1108  may be communicatively coupled to DSP  1102  and may comprise any suitable electronic system, device, or apparatus configured to selectively enable force sensor  105  and/or components of integrated haptic system  112 F, as described in greater detail below. 
     Sensor bias  1112  may be communicatively coupled to sampling control  1108  and may comprise any suitable electronic system, device, or apparatus configured to generate an electric bias (e.g., bias voltage or bias current) for force sensor  105 , as described in greater detail below. 
     In some embodiments, integrated haptic system  112 F may be formed on a single integrated circuit, thus enabling lower latency than existing approaches to haptic feedback control. 
     In operation, DSP  1102 /detector  1104  may be configured to receive a force signal V SENSE  from force sensor  105  indicative of force applied to force sensor  105 . In response to receipt of force signal V SENSE  indicating a sensed force, DSP  1102  may generate a haptic playback signal V IN  and communicate haptic playback signal V IN  to amplifier  1106 , which is amplified by amplifier  1106  to generate output voltage V OUT . 
     In addition, DSP  1102  may be configured to receive one or more timer signals (either from timing signals generated within integrated haptic system  112 F or external to integrated haptic system  112 F) and based thereon, generate signals to sampling control  1108 . In turn, sampling control  1108  may selectively enable and disable one or more components of an input path of integrated haptic system  112 F, including without limitation detector  1104 , force sensor  105 , a data interface of integrated haptic system  112 F, a switch matrix of integrated haptic system  112 F, an input amplifier of integrated haptic system  112 F, and/or an analog-to-digital converter of integrated haptic system  112 F. As shown in  FIG.  11   , sampling control  1108  may selectively enable and disable force sensor  105  by controlling an electrical bias for force sensor  105  generated by sensor bias  1112 . As a result, DSP  1102  and sampling control  1108  may duty cycle durations of time in which force sensor  105 , detector  1104 , and/or other components of integrated haptic system  112 F are active, potentially reducing power consumption of a system comprising integrated haptic system  112 F. 
     Although the foregoing figures and descriptions thereof address integrated haptic systems  112 A- 112 F as being representative of particular embodiments, is it understood that all or a portion of one or more of integrated haptic systems  112 A- 112 F may be combined with all or a portion of another of integrated haptic systems  112 A- 112 F, as suitable. 
     In addition, in many of the figures above, a DSP is shown generating a haptic playback signal V IN  which may be amplified by an amplifier to generate an output voltage V OUT . For purposes of clarity and exposition, digital-to-analog conversion of signals in the output signal path of integrated haptic systems  112 A- 112 F have been omitted from the drawings, but it is understood that digital-to-analog converters may be present in integrated haptic systems  112 A- 112 F to perform any necessary conversions from a digital domain to an analog domain. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. 
     All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present inventions have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.