Tactile adaptive duty cycle

Abstract

Various techniques of operating a linear resonant actuator (LRA) are disclosed. In some aspects, a method for operating an LRA includes generating an LRA control signal having a period, the period having an active portion and a high-Z portion according to a duty cycle; detecting, during the high-Z portion of the period, a back electromotive force (BEMF) over-threshold voltage time and a zero-crossing voltage time; calculating a period; calculating a BEMF measurement window; calculating a target duty cycle based on the period, the BEMF measurement window, and a margin time; and adjusting the duty cycle of the LRA control signal toward the target duty cycle.

Description

[0001] Cross-reference to related applications

[0002] This patent application claims the benefit of U.S. non-provisional application No. 17 / 031771 entitled “HAPTICS ADAPTIVE DUTY CYCLE”, filed on September 24, 2020, which has been assigned to the assignee of this patent and whose entire contents are expressly incorporated herein by reference. Technical Field

[0003] The various aspects of this disclosure generally relate to tactile sensation, and more specifically to the control of linear resonant actuators. Background Technology

[0004] Haptic feedback refers to the use of technologies that sense touch and motion, such as the study or use of tactile sensation and the application of touch sensing as a method of interacting with computers and electronic devices. For example, some game controllers use eccentric rotating mass (ERM) vibration motors to generate vibrations or sounds, for instance, to indicate in virtual racing games that a player has gone off the road, or in first-person shooter games that a player has been hit. However, for smartphones and handheld devices, there is a desire to reduce device size, while ERMs are relatively large. ERMs also have other drawbacks: rotating masses take time to start or stop, making it difficult to use ERMs to provide the desired “crisp” haptic feedback (with very short vibration start and stop times), such as the sensory illusion of pressing a physical button on a device without physical buttons. Therefore, mobile devices and other consumer electronics have largely shifted from using ERMs to using linear resonant actuators (LRAs) for haptic feedback.

[0005] An LRA (Low-Range Electric Resonator) is an electric motor that provides tactile feedback through vibration. An LRA is similar to a cone loudspeaker (but without a cone): a coil drives a spring-loaded magnetic mass to move back and forth, producing vibrations. Like a loudspeaker, the input to an LRA is a sine wave, which "drives" the mass to vibrate. The amplitude of the vibration (the displacement of the mass) can be influenced by the peak-to-peak input voltage of the sine wave. Unlike an ERM (Electronic Resonance Motor), where the input voltage controls the vibration frequency, an LRA has an inherent resonant frequency, and its performance and efficiency significantly decrease when driven at a frequency different from its resonant frequency.

[0006] One drawback of LRAs is that the LRA mass-spring system lacks a mechanical damper, thus requiring a "brake" to quickly stop the mass's vibrations. Typically, the brake applies the same sinusoidal input as the drive, but with the opposite polarity. Another disadvantage of LRAs is that the resonant frequency changes with the aging of the device (e.g., due to the spring losing its elasticity) and the temperature of the device (e.g., due to the thermal expansion and contraction of metal components). Therefore, continuous evaluation of the LRA's resonant frequency is necessary. One technique for evaluating the LRA's resonant frequency is to measure the reverse electromotive force (EMF).

[0007] Anti-EMF (BEMF) is an EMF generated by the rotation of a coil within a magnetic field. For ERM devices, anti-EMF acts opposite to the voltage applied to rotate the motor, thus reducing the current flowing through the motor coils. For LRA devices, BEMF appears as an alternating current (AC) signal. One method to measure BEMF in an LRA is to set the input drive signal to a high-impedance (high-Z) mode and measure the BEMF voltage across the input pin. More specifically, to sense the LRA's resonant frequency, the driver is forced into a high-impedance mode, and the BEMF voltage is monitored to detect when the BEMF changes polarity. Therefore, the typical drive signal for an LRA is a sine wave, which includes an active portion that drives or brakes the LRA and a high-Z portion during which BEMF can be measured.

[0008] Figure 1 The figure shows the typical drive signals used for LRA. Figure 1 (a) shows a quarter-wave drive (QWD) in which the LRA is driven for half the time of each half-cycle, delivering only about half of the possible power to the load. Figure 1 The conventional method shown in (a) has drawbacks, including that the longer the control signal remains in the high Z-mode, the less drive or braking power can be applied to the LRA. This limits the rate at which the LRA can achieve full vibration, and also limits the maximum force of full vibration. Figure 1 (b) illustrates an improvement to the QWD method, namely a three-quarters drive waveform, where only 1 / 8 of each half-cycle is in high-Z mode. While this increases the power available to the LRA compared to the QWD method, it still limits the power that can be delivered to the LRA, and the LRA is more susceptible to auto-resonance issues. If the control signal remains in high-Z mode for too short a duration, there is a risk that if the LRA resonant frequency changes abruptly, the BEMF polarity change will not be observable during the excessively short high-Z mode window, leading to incorrect resonant frequency information and degradation of drive or braking performance. Summary of the Invention

[0009] The following presents a brief summary of the invention with respect to one or more aspects disclosed herein. Therefore, the following summary should not be considered a broad overview of all contemplated aspects, nor should it be regarded as identifying key or decisive elements regarding all contemplated aspects, or as depicting the scope associated with any particular aspect. Thus, the sole purpose of the following summary is to present, in a simplified form, certain concepts related to one or more aspects of the mechanisms disclosed herein, prior to the detailed description presented below.

[0010] According to various aspects disclosed herein, at least one aspect includes a method for dynamically adapting the drive duty cycle of a linear resonant actuator (LRA) control signal. The method includes generating an LRA control signal with a period, the period having an active portion and a high-Z portion depending on the duty cycle. The method further includes detecting the back electromotive force (BEMF) over-threshold voltage time and the BEMF zero-crossing voltage time during the high-Z portion of the period. The method further includes calculating the period. The method further includes calculating a BEMF measurement window. The method further includes calculating a target duty cycle. The method further includes adjusting the duty cycle of the LRA control signal toward the target duty cycle.

[0011] According to various aspects disclosed herein, at least one aspect includes an apparatus for dynamically adapting the drive duty cycle of a linear resonant actuator (LRA) control signal. The apparatus includes a memory and at least one processor communicatively coupled to the memory. The at least one processor is configured to: generate an LRA control signal having a periodicity, the period having an active portion and a high-Z portion depending on the duty cycle; detect BEMF over-threshold voltage time and BEMF zero-crossing voltage time during the high-Z portion of the period; calculate the period; calculate the BEMF measurement window; calculate a target duty cycle; and adjust the duty cycle of the LRA control signal toward the target duty cycle.

[0012] According to various aspects disclosed herein, at least one aspect includes an apparatus for dynamically adapting the drive duty cycle of a linear resonant actuator (LRA) control signal. The apparatus includes components for generating an LRA control signal having a periodicity, the period having an active portion and a high-Z portion depending on the duty cycle. The apparatus also includes components for detecting the BEMF over-threshold voltage time and zero-crossing voltage time during the high-Z portion of the period. The apparatus further includes components for calculating the period. The apparatus also includes components for calculating a BEMF measurement window. The apparatus further includes components for calculating a target duty cycle. The apparatus further includes components for adjusting the duty cycle of the LRA control signal toward the target duty cycle.

[0013] According to various aspects disclosed herein, at least one aspect includes a non-transitory computer-readable medium storing computer-executable instructions. The non-transitory computer-readable medium storing computer-executable instructions includes at least one instruction instructing a device to generate an LRA control signal having a period, the period having an active portion and a high Z portion according to a duty cycle, and at least one instruction instructing the device to detect BEMF over-threshold voltage time and zero-crossing voltage time during the high Z portion of the period. The non-transitory computer-readable medium storing computer-executable instructions also includes at least one instruction instructing the device to calculate the period, at least one instruction instructing the device to calculate the BEMF measurement window, at least one instruction instructing the device to calculate a target duty cycle, and at least one instruction instructing the device to adjust the duty cycle toward the target duty cycle.

[0014] Other objects and advantages associated with the aspects disclosed herein will be apparent to those skilled in the art based on the accompanying drawings and detailed description. Attached Figure Description

[0015] The accompanying drawings are provided to aid in the description of one or more aspects of the disclosed subject matter, and are intended to be illustrative only and not limiting:

[0016] Figure 1 The figure shows the conventional drive signal used for a linear resonant actuator (LRA).

[0017] Figure 2 It is a curve of the output voltage based on the LRA control signals from various aspects.

[0018] Figure 3 The various parts of the LRA control signal are shown in more detail according to some aspects.

[0019] Figure 4 It is an example LRA control signal with a dynamically adjusted duty cycle based on some aspects.

[0020] Figure 5 The figure illustrates some measurements included in a method for dynamically calculating the drive duty cycle of the LRA control signal, based on several aspects.

[0021] Figure 6 This is a block diagram illustrating an exemplary device for dynamically adapting the drive duty cycle of an LRA control signal according to some aspects.

[0022] Figure 7 The figure illustrates an exemplary method for dynamically adapting the drive duty cycle of the LRA control signal based on several factors. Detailed Implementation

[0023] Various aspects of this disclosure are provided in conjunction with the accompanying drawings, which are provided for illustrative purposes, in the following description. Alternative aspects may be contemplated without departing from the scope of this disclosure. Furthermore, well-known elements of this disclosure may not be described in detail or may be omitted so as not to obscure the relevant details of this disclosure.

[0024] The terms “exemplary” and “example” as used herein mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” or “example” should not be construed as preferred or superior to other aspects. Similarly, the term “aspects of this disclosure” does not require that all aspects of this disclosure include the features, advantages, or modes of operation discussed.

[0025] Those skilled in the art will understand that any of a variety of different techniques and skills can be used to represent the information and signals described below. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description below can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof, depending in part on the specific application, in part on the desired design, and in part on the appropriate technology, etc.

[0026] Furthermore, many aspects are described based on sequences of actions performed by elements of, for example, computing devices. It will be appreciated that the various actions described herein can be performed by specific circuitry (e.g., application-specific integrated circuits (ASICs)), program instructions executed by one or more processors, or a combination of both. Moreover, the sequences of actions described herein can be considered entirely embodied in any form of non-transitory computer-readable storage medium storing a corresponding set of computer instructions that, when executed, will cause or instruct the associated processor of the device to perform the functionality described herein. Therefore, various aspects of this disclosure can be embodied in several different forms, all of which are contemplated within the scope of the claimed subject matter. Furthermore, for each aspect described herein, the corresponding form of any such aspect can be described herein as, for example, "logically configured" to perform the described actions.

[0027] To overcome the technical limitations of conventional methods for driving and braking linear resonant actuators (LRAs), this paper presents a method and system for dynamically adapting the drive duty cycle of an LRA.

[0028] Figure 2 This is a graph of the output voltage of the LRA control signal according to various aspects of this disclosure. Figure 2In the middle, the high Z time decreases for each half-cycle, for example, t0 > t1 > t2 > t4, which results in a corresponding increase in the drive duty cycle. This maximizes the power that can be applied to the LRA during drive and braking operations, allowing the LRA to quickly reach full amplitude and return to rest. This capability enables the LRA to provide a crisp response, for example, simulating the need for a button press on a device without mechanical buttons.

[0029] Figure 3 The portions of the LRA control signals according to various aspects of this disclosure are shown in more detail. Figure 3 (a) shows half a cycle of the control signal (which is a sine wave in this example) before the duty cycle is adjusted according to various aspects of this disclosure. The control signal waveform includes an active portion 300 and a high-Z portion 302. During the high-Z portion 302 of the waveform, the BEMF voltage 304 can be detected. Note that in Figure 3 As shown in the following figures, the BEMF voltage 304 does not scale with the drive waveform.

[0030] The time from when the BEMF voltage 304 crosses the first voltage threshold 306 until the BEMF voltage changes polarity (i.e., crosses the zero voltage threshold 308) is... Figure 3 The time Twindow is shown in the diagram. Twindow is the time during which the LRA driver must be in high Z mode to detect zero crossings and determine the current resonant frequency of the LRA. Tmargin is the time required for the voltage driver to transition from the active state to the high Z state, and may include additional time to accommodate possible variations in Twindow (e.g., due to changes in the LRA's operating temperature). Tmargin is the additional time the voltage driver spends unnecessarily in the high Z state. Twindow can vary depending on the LRA's operating conditions, but the time it takes for the driver to transition from the active state to the high Z state is relatively stable. Therefore, in some aspects, Tmargin is considered a constant value. In some aspects, the value of Tmargin can be programmed.

[0031] Figure 3 (b) illustrates half a cycle of the control signal after duty cycle adjustment according to various aspects of this disclosure. Figure 3 In this process, the duty cycle of the control signal is adjusted to eliminate Textra, which provides an additional drive time of 310. In this way, maximum power can be supplied to the LRA to drive and brake vibrations.

[0032] In some respects, the amount of control signal duty cycle that can be changed with each adjustment is limited. In other respects, the parameter DRV_DUTY_STEP defines the maximum amount of control signal duty cycle that can be adjusted per half-cycle or per other time period.

[0033] In some aspects, a wide high-Z portion 302 in the initial cycle is valuable for discovering and tracking resonant frequencies. However, as the energy in the LRA increases, for example, the BEMF amplitude increases during the driving pattern, the required high-Z time decreases. The LRA accelerates more rapidly with increasing duty cycle. In some aspects, the duty cycle is dynamically adjusted by calculating the high-Z time required for half a cycle as equal to the Twindow time measured in the preceding half-cycle plus a fixed Tmargin time.

[0034] exist Figure 3 In this context, the concept is described as eliminating Textra. Similarly, this same concept can be described as dividing the time between the start of the high Z portion and its zero-crossing into two parts (Tmargin and Twindow), and changing the duty cycle until Tmargin reaches its minimum allowable value, such as... Figure 4 As shown.

[0035] Figure 4 It is an example LRA control signal with a dynamically adjusted duty cycle based on some aspects. Figure 4 The control signal waveforms during drive operation 400 and braking operation 402 are shown. During drive operation 400, the control signal is considered a drive signal or a signal for driving, while during braking operation 402, the control signal is considered a braking signal or a signal for braking. The control signal drives the LRA to begin its vibration, then brakes the LRA to stop its vibration, after which the generation of the LRA control signal ceases. In some aspects, the drive signal will have a first polarity, while the braking signal will have a second polarity. Typically, the braking signal will have the opposite polarity to the drive signal; for example, the braking signal is 180 degrees out of phase with the drive signal.

[0036] During drive operation 400, the control signal voltage is at its maximum amplitude 404, and the duty cycle is adjusted such that the duration of the high Z portion 302 of half a cycle is equal to the target (e.g., minimum) value of Twindow plus Tmargin. This maximizes the duration of the active portion 300 and thus maximizes the drive power of the control signal. During drive operation 400, one objective is to increase the BEMF amplitude and therefore reduce the Twindow.

[0037] During braking operation 402, the control signal will change polarity, thus braking the LRA's vibration. During braking operation 402, the goal is to reduce BEMF and therefore increase Twindow, but the braking amplitude should be continuously adjusted to obtain a specific target BEMF reduction factor in each half-cycle, so that this factor decreases as BEMF approaches zero. This is in Figure 4As shown, the control signal is reduced to a lower amplitude 406 to achieve specific attenuation of the BEMF, and the Twindow is increased by a specific factor compared to the previous Twindow. If the braking is very severe and the amplitude is not reduced, the vibration intensity may actually increase again due to so-called overbraking.

[0038] In some respects, the equation for braking amplitude is:

[0039]

[0040] in:

[0041] ·B cal It is the braking amplitude used during the forced response portion of the calibration sequence;

[0042] ·Twindow nat It is the Twindow[n] measured during the natural response portion of the calibration sequence;

[0043] ·Twindow cal It is the Twindow[n] measured during the forced response portion of the calibration sequence;

[0044] ·R nat The natural BEMF reduction factor calculated during calibration:

[0045]

[0046] R cal The forced BEMF reduction factor is calculated during calibration:

[0047]

[0048] R set It is the expected BEMF reduction factor:

[0049]

[0050] In some aspects, the reduction factor R set It is programmable.

[0051] In some respects, the high Z time (Thiz) of half a braking cycle can be calculated as:

[0052] Thiz[n] = Twindow[n] + Tmargin

[0053] in:

[0054]

[0055] Figure 5 The diagram illustrates some measurements included in the method for calculating the drive duty cycle, based on several aspects. For example... Figure 5 As can be seen, T_lra is the natural resonant period of the LRA, and DRV_PER is the duration of the driver in active mode. For example... Figure 4 As shown, Twindow is the time it takes for the BEMF voltage to rise from the measurement threshold voltage to the zero-crossing voltage, and during this period, the LRA driver must be in high Z mode to detect the zero-crossing and determine the current resonant frequency of the LRA. Figure 5 In this context, the duration from the end of one Twindow cycle to the start of the next Twindow cycle is T_wind_rise.

[0056] In some respects, the initial drive period (e.g., the drive period initially used when starting drive operation) is calculated as a fixed percentage of half the last measured natural resonance period:

[0057]

[0058] DRIVE_DUTY is a default or saved parameter. This equation is used when Twindow has not yet been measured and therefore T_wind_rise is unknown.

[0059] Once T_lra and Twindow are measured and T_wind_rise is calculated, the target drive period ADPT_DRV_PER can be calculated as reducing T_wind_rise by Tmargin. In some respects, Tmargin is defined as a specified percentage of half the current resonant period of the LRA:

[0060]

[0061] Here, TWIND_MARGIN / 100 represents the specified percentage. In some aspects, different TWIND_MARGIN values ​​can be defined for drive and braking operations; for example, separate parameters DRV_TWIND_MARGIN and BRK_TWIND_MARGIN can be used, and they can be configured independently.

[0062] In some aspects, limits are imposed on how quickly the current drive cycle's DRV_PER can be changed to the target drive cycle's ADPT_DRV_PER during drive operations. For example, in some aspects, DRV_PER changes are allowed to be no more than a certain percentage of a maximum value equal to half a cycle:

[0063]

[0064] DRIVE_DUTY_STEP / 100 defines the maximum percentage change allowed in each calculation. In some aspects, a separate BRAKE_DUTY_STEP may also be used to define the maximum percentage change allowed in each calculation during braking operations.

[0065] The table below illustrates the possible values ​​for the parameters DRV_DUTY_STEP, DRV_TWIND_MARGIN, and BRK_TWIN_MARGIN, depending on several factors.

[0066] Table 1

[0067]

[0068] Figure 6 This is a block diagram illustrating an exemplary device 600 for dynamically adapting the drive duty cycle of the LRA602 according to some aspects. Figure 6 In this device 600 (which may include haptic driver circuitry), a digital controller 604 or other processor circuitry is included. In some aspects, the digital controller 604 receives amplitude information from a pattern source 606 and frequency information from a clock generator 608, and outputs signals to control a driver and power stage 610, which generate a pair of control signals (VSWP and VSWM) driving the LRA 602. The device 600 includes a BEMF detection circuit 612 that generates information 614, other information, or a combination thereof, relating to the phase (Φ) and amplitude (A) of the detected BEMF input across the two ends of the LRA 602. This information 614 is used by the digital controller 604 to dynamically adjust the amplitude, period, and duty cycle of the LRA control signals VSWP and VSWM according to the techniques described herein. In some aspects, a duty cycle calculation function, module, or circuitry 616 can perform any of the calculations described herein. For example, BEMF information can be used to determine the values ​​of Twindow, T_lra, and T_wind_rise as described above. In some aspects, device 600 may include memory 618 communicatively coupled to digital controller 604 for storing computer instructions, parameters, variables, etc. Figure 6 The specific components and connections shown are illustrative and not limiting.

[0069] The methods and systems described herein offer several technical solutions to the technical problems associated with conventional methods and systems for controlling LRAs. For example, dynamically adjusting the duty cycle of the active portion of the control signal according to the aspects disclosed herein achieves an increase in drive cycle (up to 100% compared to conventional QWD and up to 33% compared to conventional 3 / 8 drive), resulting in faster acceleration and a higher G-force being applied to the LRA compared to conventional methods for the same drive pattern. Moreover, by reducing the chance of missing the BEMF zero-crossing event, the techniques described herein avoid the self-resonance error conventionally experienced by conventional methods during drive and braking operations.

[0070] Figure 7 The figure illustrates an exemplary method 700 for operating an LRA according to some aspects of this disclosure. Figure 7 The following variables were used:

[0071] • T_PERIOD is the assumed period of the LRA resonance frequency;

[0072] • T_DUTY_CYCLE is the portion of the cycle during which the driver is in an active state (the rest of the cycle is in a high-Z state).

[0073] • T_WINDOW is a measurement of the time taken for BEMF to return to zero from the threshold voltage;

[0074] • T_MARGIN is the time the driver circuit uses to transition from the active state to the high Z state, and may also include additional time to adapt to changes caused by operating conditions, etc.

[0075] • TARGET_DUTY_CYCLE is the calculated ideal T_DUTY_CYCLE;

[0076] • INITIAL_PERIOD is the initial value of T_PERIOD;

[0077] • INITIAL_DUTY_CYCLE is the initial value of T_DUTY_CYCLE, for example, it is used before T_WINDOW is measured.

[0078] exist Figure 7In method 700, the process begins by activating the LRA control signal, for example, initiating the drive operation, and setting some parameters to initial values. At 702, T_PERIOD is set to the initial period (INITIAL_PERIOD), T_DUTY_CYCLE is set to the initial duty cycle (INITIAL_DUTY_CYCLE), and the LRA is driven, for example, the driver begins outputting control signals to the LRA input terminals. In some aspects, T_DUTY_CYCLE is set to a conservative value, for example, a value that provides a long high Z state so as not to accidentally miss the BEMF zero-crossing.

[0079] At 704, the BEMF overthreshold voltage and zero crossing are detected.

[0080] At position 706, for example, T_PERIOD is calculated based on the zero-crossing time of BEMF. In some respects, the calculated T_PERIOD may differ slightly from the initial T_PERIOD, for example, due to changes in temperature or other operating conditions caused by LRA aging. In such cases, the calculated T_PERIOD replaces the previously used value.

[0081] At 708, for example, T_WINDOW is calculated based on the BEMF over-threshold voltage time and the BEMF zero-crossing voltage time. In some aspects:

[0082] T_WINDOW = (BEMF zero-crossing time) – (BEMF threshold voltage crossing time)

[0083] At 710, the calculated values ​​of T_PERIOD and T_WINDOW are used to calculate TARGET_DUTY_CYCLE. In some aspects, TARGET_DUTY_CYCLE is calculated as a percentage:

[0084] (T_PERIOD / 2–T_WINDOW–T_MARGIN) / (T_PERIOD / 2)

[0085] Or it can be calculated as a duration:

[0086] (T_PERIOD / 2–T_WINDOW–T_MARGIN)

[0087] T_MARGIN can be a fixed value, a programmable value, or a dynamically calculated value.

[0088] At 712, T_DUTY_CYCLE is adjusted towards TARGET_DUTY_CYCLE. In some respects, T_DUTY_CYCLE can be set to TARGET_DUTY_CYCLE. However, in other respects, the amount by which T_DUTY_CYCLE can change during any adjustment can be limited to the maximum step size (STEP_SIZE), which can be defined as the duration or a percentage of T_PERIOD. In these respects, the following equation can be used:

[0089] DELTA_DUTY_CYCLE=T_DUTY_CYCLE–TARGET_DUTY_CYCLE

[0090] T_DUTY_CYCLE=T_DUTY-CYCLE–MAX(DELTA_DUTY_CYCLE,STEP_SIZE)

[0091] STEP_SIZE represents the duration.

[0092] At 714, for example during braking, the drive signal amplitude can be selectively adjusted. During driving, the control signal amplitude is typically set to its maximum value, but in some aspects, a ramp-up or other type of amplitude modulation of the control signal amplitude may be available when needed.

[0093] At point 716, if a driving or braking operation is in progress, the process begins to repeat at point 704. This continues until the driving or braking operation is completed. If the driving or braking operation has been completed, the process proceeds to point 718.

[0094] At 718, for example, under the assumption that the recently calculated T_PERIOT will continue to reflect the natural resonance of the LRA in the future, the current value of T_PERIOD can optionally be stored as a new INITIAL_PERIOD.

[0095] Those skilled in the art will understand that information and signals can be represented using any of a variety of different techniques and skills. For example, data, instructions, commands, information, signals, bits, symbols, and chips referenced throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0096] Furthermore, those skilled in the art will appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the aspects disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps have been described above in general terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the system as a whole. Skilled artisans can implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as departing from the scope of this disclosure.

[0097] The various illustrative logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein can be implemented or executed using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic designed to perform the functions described herein, discrete hardware components, or any combination thereof. The general-purpose processor can be a microprocessor, but in alternative embodiments, the processor can be any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors integrated with a DSP core, or any other such configuration.

[0098] The methods, sequences, and / or algorithms described in conjunction with the aspects disclosed herein can be implemented directly in hardware, as a software module executed by a processor, or a combination of both. The software module can reside in random access memory (RAM), flash memory, read-only memory (ROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal (e.g., a user equipment (UE)). Alternatively, the processor and storage medium can reside as discrete components in the user terminal.

[0099] In one or more exemplary aspects, the described functionality can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, these functions can be stored or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, with communication media including any medium that facilitates the transfer of a computer program from one place to another. Storage media can be any available medium accessible to a computer. By way of example and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Furthermore, any connection is properly referred to as a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then that coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of a medium. As used herein, disks and optical discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0100] While the foregoing disclosure illustrates illustrative aspects of this disclosure, it should be noted that various changes and modifications may be made thereto without departing from the scope of this disclosure as defined by the appended claims. The functions, steps, and / or actions of the method claims according to the examples of the disclosure described herein need not be performed in any particular order. Furthermore, although elements of this disclosure may be described or claimed in the singular, plural forms are contemplated unless explicitly limited to the singular.

Claims

1. A method for dynamically adapting the drive duty cycle of a linear resonant actuator (LRA) control signal, the method comprising: A periodic LRA control signal is generated, the period having an active portion and a high Z portion according to the duty cycle, wherein the LRA is driven or braked during the active portion of the period, and the LRA is set to high impedance during the high Z portion of the period to allow measurement of back electromotive force (BEMF). During the high Z portion of the cycle, the BEMF over-threshold voltage time and the BEMF zero-crossing voltage time are detected, wherein the BEMF over-threshold voltage time is the time during which the BEMF voltage crosses the BEMF threshold voltage before the BEMF voltage changes polarity; The period is calculated based on the zero-crossing voltage time of the BEMF; The BEMF measurement window is calculated based on the BEMF over-threshold voltage time and the BEMF zero-crossing voltage time. Calculate the target duty cycle, which is a function of the period, the BEMF measurement window, and the margin time; and The duty cycle of the LRA control signal is adjusted toward the target duty cycle.

2. The method according to claim 1, further comprising: Adjust the signal amplitude of the LRA control signal.

3. The method according to claim 1, further comprising: The method is repeated while the LRA control signal is continuously generated.

4. The method according to claim 1, further comprising: Before generating the LRA control signal, the period is set to the initial period, and the duty cycle is set to the initial duty cycle.

5. The method according to claim 4, further comprising: After generating the LRA control signal, the current value of the period is stored as the initial period.

6. The method according to claim 1, wherein, The period = 2 × ((BEMF zero-crossing voltage time of half a cycle) – (start time of the active part of the half cycle)).

7. The method according to claim 1, wherein, The target duty cycle = (cycle / 2 – BEMF measurement window – margin time).

8. The method according to claim 1, wherein, The target duty cycle = (cycle / 2 – BEMF measurement window – margin time) / (cycle / 2).

9. The method according to claim 1, wherein, Adjusting the duty cycle toward the target duty cycle includes setting the duty cycle to be equal to the target duty cycle.

10. The method according to claim 1, wherein, Adjusting the duty cycle toward the target duty cycle includes adjusting the duty cycle toward the target duty cycle by no more than the maximum step size.

11. The method according to claim 1, wherein, When the LRA control signal is a drive signal, the LRA control signal has a first polarity, and when the LRA control signal is a braking signal, the LRA control signal has a second polarity different from the first polarity.

12. The method according to claim 11, wherein, The second polarity is the opposite polarity of the first polarity.

13. An apparatus for dynamically adapting the drive duty cycle of a linear resonant actuator (LRA) control signal, the apparatus comprising: At least one memory, the at least one memory including instructions; as well as At least one processor is configured to execute the instructions to cause the device to: A periodic LRA control signal is generated, the period having an active portion and a high Z portion according to the duty cycle, wherein the LRA is driven or braked during the active portion of the period, and the LRA is set to high impedance during the high Z portion of the period to allow measurement of back electromotive force (BEMF). During the high Z portion of the cycle, the BEMF over-threshold voltage time and the BEMF zero-crossing voltage time are detected, wherein the BEMF over-threshold voltage time is the time during which the BEMF voltage crosses the BEMF threshold voltage before the BEMF voltage changes polarity; The period is calculated based on the zero-crossing voltage time of the BEMF; The BEMF measurement window is calculated based on the BEMF over-threshold voltage time and the BEMF zero-crossing voltage time. Calculate the target duty cycle, which is a function of the period, the BEMF measurement window, and the margin time; and The duty cycle of the LRA control signal is adjusted toward the target duty cycle.

14. The apparatus according to claim 13, wherein, The at least one processor is further configured to cause the device to adjust the amplitude of the LRA control signal.

15. The apparatus according to claim 13, wherein, The at least one processor is further configured to cause the device to repeatedly generate, detect, calculate, and adjust the LRA control signal while continuously generating the LRA control signal.

16. The apparatus according to claim 13, wherein, The at least one processor is further configured such that the device sets the period to an initial period and the duty cycle to an initial duty cycle before generating the LRA control signal.

17. The apparatus according to claim 16, wherein, The at least one processor is further configured such that, after generating the LRA control signal, the device stores the current value of the period as the initial period.

18. The apparatus according to claim 13, wherein, The period = 2 × ((BEMF zero-crossing voltage time of half a cycle) – (start time of the active part of the half cycle)).

19. The apparatus according to claim 13, wherein, The target duty cycle = (cycle / 2 – BEMF measurement window – margin time).

20. The apparatus according to claim 13, wherein, The target duty cycle = (cycle / 2 – BEMF measurement window – margin time) / (cycle / 2).

21. The apparatus according to claim 13, wherein, Adjusting the duty cycle toward the target duty cycle includes setting the duty cycle to be equal to the target duty cycle.

22. The apparatus according to claim 13, wherein, Adjusting the duty cycle toward the target duty cycle includes adjusting the duty cycle toward the target duty cycle by no more than the maximum step size.

23. The apparatus according to claim 13, wherein, When the LRA control signal is a drive signal, the LRA control signal has a first polarity, and when the LRA control signal is a braking signal, the LRA control signal has a second polarity different from the first polarity.

24. The apparatus according to claim 23, wherein, The second polarity is the opposite polarity of the first polarity.

25. An apparatus for operating a linear resonant actuator (LRA), the apparatus comprising: Components for performing the method according to any one of claims 1-12.

26. A non-transitory computer-readable medium storing computer-executable instructions, which, when executed, cause a means for operating a linear resonant actuator (LRA) to perform the method according to any one of claims 1-12.

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