Haptics audible noise reduction

Abstract

Innovative techniques for designing and generating haptic waveforms are presented. The presented techniques reduce or eliminate audible noise generated by a haptic actuator during operation. A haptic controller can construct a voltage waveform at a resonant frequency of a haptic actuator and generate a corresponding control signal. Instead of abruptly entering a high impedance state from a drive state, the voltage waveform can include a ramp-down portion in which the voltage is continuously but rapidly ramped down such that the current flowing within the actuator is ramped down before entering the high impedance state. In this way, audible noise can be reduced or even eliminated.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to systems, devices, and methods for driving haptic actuators, and in particular to systems, devices, and methods of driving haptic actuators (e.g., linear resonant actuators (LRAs)) such that audible noise from the haptic actuators is reduced or even completely eliminated. BACKGROUND

[0002] Haptic (vibro-pattern) experiences on platforms (e.g., mobile devices such as smartphones) are increasing. From one perspective, haptics can be seen as stimulating touch and motion, e.g., by reproducing the sensations when interacting with physical objects. When providing haptic feedback, i.e., when a haptic actuator (such as an LRA) is operating, unintended audible noise from the haptic actuator can impair the user experience.

[0003] Accordingly, there is a need for systems, devices, and methods (including the methods, systems, and devices provided herein) that overcome the deficiencies of conventional haptic actuators. SUMMARY

[0004] The following presents a simplified summary of one or more aspects and / or examples associated with the devices and methods disclosed herein. As such, the following summary should not be considered an extensive overview of all contemplated aspects and / or examples, nor be considered to identify key or critical elements of all contemplated aspects and / or examples, or to delineate the scope of any

[0005] An example device is disclosed. The device can include a haptic controller configured to formulate a voltage waveform at a resonant frequency of a haptic actuator and configured to generate a control signal corresponding to the voltage waveform. The voltage waveform can include at least one half-cycle divided into a drive portion, a ramp-down portion, and a high impedance (high-Z) portion. During the drive portion, the voltage waveform can be a wave at the resonant frequency. A voltage of the voltage waveform at a termination of the drive portion can be a termination drive voltage. During the ramp-down portion, the voltage of the voltage waveform can change from the termination drive voltage to a termination ramp-down voltage. An amplitude of the termination drive voltage (termination drive voltage amplitude) can be greater than an amplitude of the termination ramp-down voltage (termination ramp-down voltage amplitude). A mag(dv / dt) at the termination of the drive portion can be less than a mag(dv / dt) at a start of the ramp-down portion. The mag(dv / dt) can represent an amplitude of a change in the voltage of the voltage waveform over time. The device can also include a haptic driver configured to drive the haptic actuator with the voltage waveform based on the control signal. The haptic driver can also be configured to be disabled during the high-Z portion.

[0006] An example method is disclosed. The method can include formulating a voltage waveform at a resonant frequency of a haptic actuator. The voltage waveform can include at least one half-cycle divided into a drive portion, a ramp-down portion, and a high impedance (high-Z) portion. During the drive portion, the voltage waveform can be a wave at the resonant frequency. A voltage of the voltage waveform at a termination of the drive portion can be a termination drive voltage. During the ramp-down portion, the voltage of the voltage waveform can change from the termination drive voltage to a termination ramp-down voltage. An amplitude of the termination drive voltage (termination drive voltage amplitude) can be greater than an amplitude of the termination ramp-down voltage (termination ramp-down voltage amplitude). A mag(dv / dt) at the termination of the drive portion can be less than a mag(dv / dt) at a start of the ramp-down portion. The mag(dv / dt) can represent an amplitude of a change in the voltage of the voltage waveform over time. The method can also include generating a control signal corresponding to the voltage waveform. The method can also include driving the haptic actuator with the voltage waveform using a haptic driver based on the control signal. The haptic driver can be disabled during the high-Z portion.

[0007] An example device is disclosed. The device can include means for composing a voltage waveform at a resonant frequency of a haptic actuator. The voltage waveform can include at least one half-cycle divided into a drive portion, a ramp-down portion, and a high-impedance (high-Z) portion. During the drive portion, the voltage waveform can be a wave at the resonant frequency. A voltage of the voltage waveform at a termination of the drive portion can be a termination drive voltage. During the ramp-down portion, the voltage of the voltage waveform can change from the termination drive voltage to a termination ramp-down voltage. An amplitude of the termination drive voltage (termination drive voltage amplitude) can be greater than an amplitude of the termination ramp-down voltage (termination ramp-down voltage amplitude). A mag(dv / dt) at the termination of the drive portion can be less than a mag(dv / dt) at a beginning of the ramp-down portion. The mag(dv / dt) can represent an amplitude of a change in the voltage of the voltage waveform over time. The device can also include means for generating a control signal corresponding to the voltage waveform. The device can also include means for driving the haptic actuator with the voltage waveform based on the control signal. During the high-Z portion, the means for driving can be disabled.

[0008] An example non-transitory computer-readable medium storing computer-executable instructions for a device is disclosed. The computer-executable instructions can include one or more instructions for instructing the device to compose a voltage waveform at a resonant frequency of a haptic actuator. The voltage waveform can include at least one half-cycle divided into a drive portion, a ramp-down portion, and a high-impedance (high-Z) portion. During the drive portion, the voltage waveform can be a wave at the resonant frequency. A voltage of the voltage waveform at a termination of the drive portion can be a termination drive voltage. During the ramp-down portion, the voltage of the voltage waveform can change from the termination drive voltage to a termination ramp-down voltage. An amplitude of the termination drive voltage (termination drive voltage amplitude) can be greater than an amplitude of the termination ramp-down voltage (termination ramp-down voltage amplitude). A mag(dv / dt) at the termination of the drive portion can be less than a mag(dv / dt) at a beginning of the ramp-down portion. The mag(dv / dt) can represent an amplitude of a change in the voltage of the voltage waveform over time. The computer-executable instructions can include one or more instructions for instructing the device to generate a control signal corresponding to the voltage waveform. The computer-executable instructions can include one or more instructions for instructing the device to drive the haptic actuator with the voltage waveform using a haptic driver based on the control signal. During the high-Z portion, the haptic driver can be disabled.

[0009] Other features and advantages associated with the various devices and methods disclosed herein will be apparent from the following drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0010] Aspects of the disclosure, together with its many attendant advantages, will become better understood by reference to the following detailed description, taken in conjunction with the accompanying drawings, which are presented solely for illustration and are not intended as a definition of the limits of the disclosure.

[0011] Figure 1 Circuit representations of a haptic driver and a linear resonant actuator are illustrated.

[0012] Figure 2 An example of a regular voltage waveform applied across a linear resonant actuator is illustrated.

[0013] Figure 3A The state of a haptic driver and a linear resonant actuator just before entering a high impedance state is illustrated.

[0014] Figure 3B The state of an example haptic driver and linear resonant actuator immediately after entering a high impedance state is illustrated.

[0015] Figure 4A A regular implementation of a voltage waveform with a high impedance is illustrated.

[0016] Figure 4B An implementation of a voltage waveform with a ramp down in addition to a high impedance according to one or more aspects of the disclosure is illustrated.

[0017] Figure 5A And Figure 5B A more detailed view of an implementation of a voltage waveform according to one or more aspects of the disclosure is illustrated.

[0018] Figure 6 An example architecture of a device or system configured to generate a voltage waveform according to one or more aspects of the disclosure is illustrated.

[0019] Figure 7 A flowchart of an example method of generating a haptic waveform according to one or more aspects of the disclosure is illustrated.

[0020] Figure 8 A simplified block diagram of several sample aspects of a device configured to generate a haptic waveform according to one or more aspects of the disclosure is illustrated.

[0021] Figure 9 Various electronic devices that can utilize one or more aspects of the disclosure are illustrated.

[0022] Other objects and advantages associated with aspects disclosed herein will be apparent to those skilled in the art based on the accompanying drawings and detailed description. To the extent that certain details are presented in a certain manner, it is not intended to limit the application thereto. The dimensions of the depicted features in the accompanying drawings can be arbitrarily expanded or reduced for the sake of clarity. In accordance with convention, certain drawings can be simplified for the sake of clarity. Thus, the drawings can not depict all components of a particular apparatus or method. Further, like reference numerals designate like features throughout the specification and drawings. DETAILED DESCRIPTION

[0023] Aspects of the disclosure are illustrated by way of example in the following description and associated drawings. Alternative aspects or embodiments can be devised without departing from the scope of the present teachings. Additionally, well-known elements of the illustrative embodiments described herein can not be described in detail or will be omitted so as not to obscure the relevant details of the disclosure.

[0024] In some described example implementations, instances are identified in which various component structures and portions of operation can be taken from known conventional techniques and then arranged in accordance with one or more example embodiments. In such instances, internal details of known conventional component structures and / or portions of operation can be omitted to help avoid potential obscuring of the concepts illustrated in the illustrative embodiments disclosed herein.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0026] Haptic feedback generation can be used in mobile phones, wearable devices, virtual reality, gaming, Internet of Things (IoT), etc. Figure 1A circuit representation of an example haptic driver and LRA is illustrated. The haptic driver can include four transistors M1, M2, M3, and M4 connected in the form of an H-bridge. The positive side of transistors M1 and M3 are connected to a supply voltage Vdd (illustrated as 10V), and the negative side of transistors M2 and M4 are connected to Vss (illustrated as ground or 0V). The LRA includes a coil connected across the OUT P node and OUT M node of the H-bridge (see dashed rectangle). The coil of the LRA is modeled as an inductor L in series with a resistor R. An example inductance of the inductor L can be in the range of 150-200µH, and an example resistance of the resistor R can be about 8Ω.

[0027] A sinusoidal voltage waveform can be imposed across the coil by pulse width modulation (PWM) of the transistors M1-M4. For purposes of description, the polarity of the voltage across the coil will be considered positive when OUT P is at a higher voltage than OUT M, and negative when OUT P is at a lower voltage than OUT M. The transistors are modulated in pairs, with M1 and M4 making up a first pair, and M2 and M3 making up a second pair. The modulation is such that at most one pair of transistors is on at a given time. When the first pair of transistors (M1, M4) is on, the voltage polarity between OUT P and OUT M is positive. When the second pair of transistors (M2, M3) is on, the voltage polarity between OUT P and OUT M is negative.

[0028] It should be noted that the voltage polarity here is according to the average low frequency voltage, i.e., on the order of the resonance frequency of the LRA (e.g., tens to hundreds of hertz). The PWM is typically operated at a very high frequency (e.g., 600 kHz) with respect to the LRA. Instantaneously, there can be instances of OUT P < OUT M in the PWM operation, but the low frequency waveform (the waveform of the LRA) is still positive (OUT P > OUT M). In short, whether the voltage is considered positive or negative will be from the perspective of the low frequency wave, unless otherwise explicitly indicated.

[0029] As indicated, the PWM occurs at a very fast rate (e.g., 600K per second). This is fast enough that the current flowing within the coil and the voltage across the coil do not change instantaneously with each pulse. Rather, the voltage across the LRA coil and the current flowing in the LRA coil can represent an average voltage and current. Then, to generate the positive polarity portion of the sinusoidal waveform (OUT P voltage greater than OUT M voltage), the first pair of transistors (M1, M4) is pulse width modulated and the second pair of transistors is turned off (i.e., disabled). To generate the negative polarity portion of the sinusoidal waveform (OUT P voltage less than OUT M voltage), the second pair (M2, M3) is pulse width modulated and the first pair (M1, M4) is turned off.

[0030] When a positive voltage is applied across the LRA coil, current flows through the coil in one direction (e.g., clockwise), which in turn applies a mechanical force to the mass (e.g., permanent magnet) in one direction (e.g., left) within the coil. When a negative voltage is applied, current flows through the coil in the opposite direction (e.g., counterclockwise), which in turn applies a mechanical force to the mass in the opposite direction (e.g., right). By moving the mass back and forth, the LRA can be made to vibrate.

[0031] As indicated above, audible noise from haptic actuators such as LRAs can impact a user’s ability to have a good experience. Haptic actuators such as LRAs are high Q systems that exhibit higher levels of acceleration when driven at or near their mechanical resonance frequency (e.g., the resonance frequency of the mass). By driving the LRA at its resonance frequency, maximum vibration can be achieved.

[0032] To achieve high levels of acceleration, the LRA is driven at the resonance frequency with closed loop feedback. Note that the actual resonance frequency of a particular LRA can vary from its specified or expected resonance frequency, even slightly. Moreover, the resonance frequency of an LRA can change over time. For example, as an LRA ages, the spring stiffness of the LRA can decrease, or the magnetic properties of the mass can change. Moreover, the resonance frequency can change due to environmental conditions. For example, elevated temperatures can also affect the spring stiffness and / or magnetic properties, causing the resonance frequency to change.

[0033] Accordingly, it is desirable to determine the actual resonance frequency, which can be done by monitoring the behavior of the LRA when driven. One way to determine the actual resonance frequency of an LRA is by having an auto-resonant frequency drive haptic driver drive the LRA for about 50% to 90% of a period of the expected or intended resonance frequency (e.g., as specified in a spec sheet). The haptic driver is then disabled (i.e., go to high impedance (Z)), and the back electromotive force (back EMF, BEMF) is monitored to determine when the BEMF changes polarity (i.e., crosses zero voltage).

[0034] This is illustrated in Figure 2 , which illustrates a voltage waveform across an example LRA when driven by a haptic driver. In Figure 2 , the voltage waveform is shown as a function of time. The voltage waveform is sinusoidal, and the zero voltage crossing occurs at the resonance frequency of the LRA. The haptic driver is then disabled, and the BEMF is monitored to determine when the BEMF changes polarity (i.e., crosses zero voltage). The time between zero voltage crossings is the period of the BEMF. The frequency of the BEMF is the reciprocal of the period of the BEMF. The resonance frequency of the LRA is the frequency of the BEMF. Figure 2In particular, the haptic driver applies a voltage across the coil of the LRA to accelerate or decelerate the mass. When accelerating (decelerating), the haptic driver applies a voltage such that the resulting current generates a force that reinforces (opposes) the current motion of the mass of the LRA. For example, it can be assumed that a positive voltage across the coil of the LRA generates a force to the mass in a left direction, and a negative voltage generates a force in a right direction. If the mass is currently moving to the left, a positive (negative) voltage can be applied to accelerate (decelerate) the mass. If the mass is currently moving to the right, a negative (positive) voltage can be applied to accelerate (decelerate) the mass.

[0035] In Figure 2 The voltage waveform (represented by the solid sinusoidal curve) applied across the LRA is generated by the modulation (e.g., PWM) of transistors M1-M4. The voltage waveform (or voltage curve) above the zero line can be generated by modulating transistors M1, M4 when transistors M2, M3 are disabled. The voltage waveform below the zero line can be generated by modulating transistors M2, M3 when transistors M1, M4 are disabled.

[0036] As Figure 2 As seen in the above, the haptic driver can be in one of two modes: a drive mode and a high impedance (high-Z) mode. The haptic driver is in the drive mode at some portion of a cycle (e.g., a half-cycle) of the expected or intended resonant frequency (“drive portion”), and in the high impedance mode for the remainder of the cycle (“high-Z portion”). During the drive portion, the haptic driver drives the LRA or otherwise applies a voltage across the LRA. During the high-Z portion, the haptic driver enters a high impedance state.

[0037] For example, it can be assumed that the intended resonant frequency of the LRA (e.g., as provided in a specification sheet) is 50 Hz, which means that one intended full cycle of the voltage waveform is 20 milliseconds (ms), and an intended half-cycle is 10 ms. It can also be assumed that the drive portion is 70% of the intended half-cycle, and the high-Z portion is 30% of the half-cycle. Then for one half-cycle (i.e., 10 ms), the haptic driver applies a positive portion of the waveform across the LRA for 7 ms, and is in a high impedance state for 3 ms.

[0038] The high impedance (high-Z) state is characterized by turning off all four transistors, i.e., transistors M1, M2, M3, M4 are all disabled. In theory, if all transistors are disabled, no voltage is applied because the connections to Vdd and Vss are disabled. However, the mass of the LRA (i.e., the permanent magnet) continues to move through the coil due to its mechanical momentum. This movement through the coil generates a BEMF, which is monitored to determine when it changes polarity, i.e., when it crosses the zero line. The time between the "zero start" of the applied LRA voltage and the "zero crossing" of the BEMF represents half a cycle of the resonant frequency of the mechanical system of the LRA. Alternatively, the time between successive zero crossings of the BEMF can represent half a cycle. Thus, the BEMF can be used to determine or update the resonant frequency.

[0039] The updated resonant frequency can be used for further driving and monitoring. For example, the updated resonant frequency can be used to update the length of the next half cycle. The haptic driver then applies the negative portion of the waveform for 70% of the updated half cycle, and then enters the high impedance state for the remaining 30% of the updated half cycle. During the high-Z portion of the updated half cycle, the BEMF can be monitored to further update the resonant frequency. The operations of applying the voltage waveform and monitoring the BEMF to correct the resonant frequency can be performed continuously.

[0040] The driving and monitoring can also be performed during deceleration of the mass. In Figure 2 In the middle, it can be assumed that the last two half cycles represent the haptic driver driving the LRA to counter the motion of the LRA mass. That is, a voltage is applied across the LRA coil for a portion of a half cycle, this time to counter the motion of the LRA mass. The haptic driver then enters the high impedance state for the remaining time of the half cycle during which the BEMF is observed.

[0041] As indicated, for automatic resonant frequency driving, the haptic driver applies a waveform voltage across the LRA coil for a driving portion of a half cycle, and then enters the high impedance state for the remaining high-Z portion to monitor the BEMF. Figure 3A and Figure 3B To explain how audible noise is generated when the haptic driver enters the high impedance state. Figure 3A The state of the haptic driver and LRA circuit at the end of the driving portion (just before entering the high impedance state) is illustrated, and Figure 3B The state of the same circuit at the beginning of the high-Z portion (just after entering the high impedance state) is illustrated.

[0042] In Figure 3AIn this scenario, it can be assumed that transistors M1 and M4 are modulated before entering the high-impedance state, such that the voltage across the LRA is approximately 30% to 40% of the peak amplitude of the sinusoidal voltage waveform. Assuming Vdd = 10V and Vss = ground, the instantaneous voltage across the LRA coil is approximately +10V. The current flowing through the coil will be related to the time-averaged voltage applied across the coil. With a time-averaged differential voltage of 6V and an LRA impedance of 8Ω, an average current of 375mA will flow through the LRA. Within the LRA coil, the current flows from the OUT_P node side to the OUT_M node side. The current is supplied from the supply voltage Vdd through M1 and grounded through M4.

[0043] like Figure 3B As seen, the haptic actuator enters a high-impedance state, in which all transistors (i.e., transistors M1, M2, M3, and M4) are turned off. Even though the haptic actuator has entered a high-impedance state, current continues to flow through the LRA coil. The LRA coil windings form an inductor, and the voltage and current relationship through the inductor can be represented as... Therefore, at the moment the haptic actuator becomes high impedance, current still flows through the inductor in the same direction (from the OUT_P node side to the OUT_M node side), but the voltage across LRA is reversed. This indicates that current is being pulled from ground through the body diode of transistor M2, which pulls the OUT_P node to a voltage below ground (e.g., -0.7V). Current is also pushed to the OUT_M node, which charges and continues to rise in voltage until it is clamped by the body diode of transistor M3, meaning that the voltage at the OUT_M node rises above the supply voltage Vdd (e.g., +10.7V). As a result, the amplitude of the instantaneous voltage between OUT_P and OUT_M becomes greater than the supply voltage (11.7V > Vdd - Vss). Therefore, a significant electric field is applied through the coil, and a large braking force is applied to the mass, causing the mass to slow down rapidly. This, in turn, leads to the generation of unwanted audible noise.

[0044] This phenomenon can be summarized as follows. When the haptic actuator is suddenly disabled, the current in the LRA coil continues to flow in the same direction. If the haptic actuator is in a high-impedance state (all transistors are disabled), the voltage across the coil reverses rapidly and becomes limited by the drive supply voltage (e.g., Vdd-Vss) and the body diode of the transistor. The resulting voltage resists / counters the motion of the permanent magnet in the LRA, which causes the mass to suddenly slow down (decelerate). This sudden decrease in the mass's velocity can lead to audible noise (e.g., when the mass strikes the LRA housing). The velocity reduction can be detected by measuring the LRA acceleration; a large dv / dt can cause acceleration spikes.

[0045] In other words, large impedance can cause the mass to slow down, which is undesirable. The action of suddenly entering a high impedance state (turning off the transistor) causes the residual DC current to be rectified and release energy in the coil, resulting in a negative acceleration force on the mass, thereby causing the mass to slow down (very quickly), which results in the appearance of audible noise. A direct correlation has been observed between audible noise and disturbances in LRA acceleration.

[0046] Before proceeding further, note the following. In the discussion below, an LRA can be used as an example of a haptic actuator. However, it should be kept in mind that the discussion can apply to other types of haptic actuators (e.g., eccentric rotating mass (ERM), piezoelectric bender, etc.).

[0047] To address the problems of existing ways of driving haptic actuators, it is proposed to provide systems, apparatuses, and / or methods for a haptic driver to enter a high impedance state to monitor BEMF while minimizing or even eliminating disturbances to mechanical motion of an actuator mass. In one aspect, a transition mode (also referred to as a “ramp down” mode) is provided to the haptic driver in addition to a drive mode and a high Z mode.

[0048] This is illustrated in Figure 4A and Figure 4B In Figure 4A , a conventional implementation of a drive waveform with a high impedance is shown. In this conventional implementation, the haptic driver drives an actuator (e.g., an LRA) such that a voltage in the form of a sine wave (denoted as “actuator voltage”) is applied across the actuator coil during a drive portion of a half cycle. The haptic driver then suddenly enters a high impedance state and remains in the high impedance state during a high Z portion, i.e., for the remaining portion of the half cycle. During the high Z portion, BEMF is observed to determine the actual half cycle and, thus, the resonant frequency of the actuator. But as noted, this sudden entry into a high impedance state can cause audible noise to be generated.

[0049] One way to minimize or even eliminate noise generation is to incorporate a “ramp down” portion between the drive portion and the high Z portion of the half cycle. That is, the half cycle can be divided into a drive portion, a ramp down portion, and a high Z portion. This is illustrated in Figure 4BThe middle example is illustrated. As before, during the drive portion, the haptic driver can be controlled to drive the haptic actuator such that a voltage waveform (denoted as "actuator voltage (drive)") is applied to the haptic actuator. The voltage waveform can be a sinusoidal waveform. As an example, the drive portion can be at least 50% of a half cycle (e.g., about 50% to 90% of a half cycle). The drive portion can be followed by a ramp down portion (described below). Thereafter, for the remaining high-Z portion of the half cycle, the haptic controller can control the haptic driver to enter a high impedance state in which all transistors are disabled and the BEMF is observed to determine the actual half cycle. In an aspect, the half cycles and / or cycles of the LRA can be calculated in each and every half cycle (e.g., from one zero crossing to the next). Generally, one or more zero crossings of the BEMF can be used to calculate the resonant frequency (e.g., by determining the half cycles of each zero crossing, by determining the full cycles of every other zero crossing, etc.).

[0050] During the ramp down portion, the haptic controller can control the haptic driver to cause the voltage applied across the actuator coil (denoted as "actuator voltage (ramp down)") to continuously but quickly ramp down such that the current flowing through the coil quickly drops to zero, or at least to a value less than some threshold current value, before entering the high impedance state. The threshold current value can be a current value in which any opposing mechanical forces due to residual current do not result in audible noise generation, or any noise generated is less than some threshold noise level.

[0051] Figure 4B The middle example is illustrated. As before, during the drive portion, the haptic driver can be controlled to drive the haptic actuator such that a voltage waveform (denoted as "actuator voltage (drive)") is applied to the haptic actuator. The voltage waveform can be a sinusoidal waveform. As an example, the drive portion can be at least 50% of a half cycle (e.g., about 50% to 90% of a half cycle). The drive portion can be followed by a ramp down portion (described below). Thereafter, for the remaining high-Z portion of the half cycle, the haptic controller can control the haptic driver to enter a high impedance state in which all transistors are disabled and the BEMF is observed to determine the actual half cycle. In an aspect, the half cycles and / or cycles of the LRA can be calculated in each and every half cycle (e.g., from one zero crossing to the next). Generally, one or more zero crossings of the BEMF can be used to calculate the resonant frequency (e.g., by determining the half cycles of each zero crossing, by determining the full cycles of every other zero crossing, etc.). Figure 4B The concepts illustrated and described can also apply. Thus, with respect to Figure 4B The voltages and currents discussed can be generalized to refer to the amplitudes of the voltages and currents. For example, the ramp down of the actuator voltage can be generalized to ramp down the amplitude of the actuator voltage. Similarly, the detected BEMF can be generalized to detect the amplitude of the BEMF voltage. Thus, unless explicitly indicated otherwise, the discussion of voltages and currents should be taken to apply to the amplitudes of the voltages and currents. Note that the BEMF and the drive voltage can not be in proportion. For example, the drive voltage can be a few volts (e.g., up to 11 V), but the BEMF can typically be very small (e.g., less than 100 mV or as low as a few mV).

[0052] As mentioned, during the ramp-down portion, the haptic driver can be controlled to ramp down the applied actuator voltage as fast as possible but in a continuous manner, rather than abruptly entering a high impedance state. Thus, instead of abruptly entering a high-Z state, in combination with the transition portion, the haptic driver can smoothly enter a high-Z state. During the ramp-down portion, the transistors (such as Ml, M2, M3, M4) can be modulated such that a ramp-down voltage is applied across the actuator coil in a smooth manner. The actuator voltage during the ramp-down can be brought to some minimum threshold voltage, such as zero. In some cases, the minimum threshold voltage can even be below zero (i.e., change polarity).

[0053] One way to visualize the difference between the voltage curve of the drive portion and the ramp-down portion can be as follows. In the drive portion, the voltage curve can generally follow a sinusoidal wave curve. However, during the ramp-down portion, at least at the beginning of the ramp-down portion relative to the termination of the drive portion, the voltage curve can be steeper than the sinusoidal wave. That is, the magnitude of dv / dt at the beginning of the ramp-down portion can be greater than the magnitude of dv / dt at the termination of the drive portion.

[0054] Figure 5A And Figure 5B Examples of the shape of the voltage ramp-down are illustrated. Before proceeding further, the BEMF is illustrated as linear. This is done to simplify the illustration. Generally, the BEMF is non-linear, depending on the characteristics of the LRA (e.g., displacement, coil area, etc.). However, the concepts discussed, such as the window crossing and zero crossing, are still applicable.

[0055] In Figure 5A And Figure 5B The view of the ramp-down portion is zoomed in to better illustrate the shape of the voltage curve during this portion. The voltage of the voltage waveform at the termination of the drive portion is labeled as the termination drive voltage. During the ramp-down portion, the voltage of the voltage waveform can ramp down from the termination drive voltage to a termination ramp-down voltage. In one aspect, the ramp-down of the actuator voltage can be exponential, i.e., very fast at the beginning of the ramp-down portion and slowly approaching the termination ramp-down voltage (e.g., zero) at the termination of the ramp-down portion, as illustrated in Figure 5A In another aspect, the ramp-down can be linear with respect to the minimum threshold voltage at the termination of the ramp-down portion, as illustrated in Figure 5B

[0056] Alternatively, for one or both of the exponential ramp-down and linear ramp-down, the voltage applied across the actuator can be programmed to be reversed (act as a brake) to quickly reduce the actuator current. That is, the polarity of the termination ramp-down voltage can be opposite to the polarity of the termination drive voltage. These alternatives are illustrated in Figure 5A and​Figure 5B is shown, where the substitute actuator voltage is shown as a dotted line curve. In an aspect, within the ramp down portion, a delay, referred to as a "brake delay," can be added between the completion of the actuator voltage ramp down and the start of the high impedance portion. That is, the voltage can reach the end ramp down voltage and then remain at the end ramp down voltage during this brake delay. It should be noted that when the end ramp down voltage is zero, the brake delay can be implemented.

[0057] In an aspect, the ramp down can be implemented by changing the duty cycle of the PWM (e.g., 600 kHz) such that the average voltage (actuator voltage) is reduced to a certain voltage level (e.g., end ramp down voltage) and the average current (current flowing in the actuator) is also reduced to a certain current level (e.g., zero). That is, by ramping down the voltage during the ramp down portion, the residual current flowing through the coil can be significantly reduced, such as even to zero. Thus, when the haptic driver enters the high impedance state, the generated noise can be significantly reduced or even completely eliminated.

[0058] The duration of the ramp down portion can depend on one or more considerations or factors. The following are some factors that can be considered in determining the duration of the ramp down portion (not necessarily exhaustive): energy input to the actuator, smooth / continuous ramp down completion, and BEMF window. With respect to the energy input to the actuator, it is generally desirable to maximize the energy input to the actuator to enhance performance. This means that the drive portion should be as long as possible, which in turn means that the ramp down portion should be as short as possible.

[0059] With respect to the smooth / continuous ramp down completion, the inductance of the actuator can limit the speed at which the voltage across the actuator can change. That is, there can be a max (dv / dt), and the speed of the ramp down should take this max (dv / dt) into account. In short, the ramp down portion should be long enough to complete the ramping down of the applied voltage to the desired minimum threshold voltage (e.g., ramping down to zero for polarity change plus brake delay, etc.). A longer ramp down portion can allow for a smoother ramp down voltage curve.

[0060] With respect to the BEMF, in an aspect, it can be desirable to determine the amount of energy currently present in the actuator. For example, when the vibration of the actuator is to be stopped, the energy information can be used to determine the amount of braking force, and the amount of time for braking can be determined. The BEMF window can be used to determine the amount of energy present in the actuator. In Figure 4B , Figure 5A and Figure 5BIn particular, the BEMF window is defined as the voltage region between zero and some voltage level above zero. Since the BEMF window shown in these figures is in magnitude, the actual BEMF window can be the region above and below the zero line. The time between the BEMF crossing the BEMF window (labeled "window crossing") and the zero crossing can be used to quantify the amount of energy present in the actuator.

[0061] If the BEMF window is utilized, the high-Z portion should be long enough so that when the haptic driver enters the high-Z state, the BEMF is outside the BEMF window. This can determine a minimum duration of the high-Z portion, which in turn can affect the length of the drive portion and / or the ramp-down portion accordingly.

[0062] Note that the BEMF window is not necessary if determining the energy of the actuator is not required or if there are alternative ways of determining the energy. In such cases, the zero crossing can be detected to determine the half-cycle. There is no need to implement the BEMF window crossing. Thus, the high-Z portion can be relatively short, which means the drive portion and / or the ramp-down portion can be made longer.

[0063] Taking into account one or more of such factors, the duration of the ramp-down portion can typically be in the range of 10 ps to 100 ps. However, depending on the situation, the ramp-down portion can be outside the general range (e.g., shorter than 10 ps or longer than 100 ps).

[0064] Figure 6 An example architecture of an apparatus or system 600 configured to generate a haptic waveform is illustrated in accordance with one or more aspects of the present disclosure. The apparatus 600 can be a mobile device such as a smartphone. As seen, the apparatus 300 can include a haptic actuator 610, a haptic driver 620, a feedback sensor 630, a haptic controller 640, and a memory 650.

[0065] The haptic actuator 610 can be a two-terminal device that is driven by a differential analog drive signal output by the haptic driver 620. The drive signal can be used to drive the haptic actuator 610. The haptic actuator 610 (e.g., LRA, ERM, piezoelectric bender, etc.) can be configured to vibrate based on the drive signal from the haptic controller 640.

[0066] The haptic driver 620 can be configured to generate the drive signal (i.e., generate a voltage waveform) based on a control signal received from the haptic controller 640 and provide the drive signal to the haptic actuator 610.

[0067] The feedback sensor 630 can be configured to take one or more feedback (e.g., BEMF) measurements and provide feedback to the haptic controller 640. The feedback can be information about the measurements, such as sensed BEMF. For example, the feedback can include voltage levels of sensed BEMF. Alternatively or additionally, the feedback can include zero-crossing and / or window-crossing indications and / or crossings of any other threshold voltage levels of BEMF.

[0068] The haptic controller 640 can include an application processor 642 and a digital signal processor (DSP) 644. The DSP 644 can be configured to track and update parameters of the haptic actuator based on feedback from the haptic driver 620, including resonant frequency, cycle length, half-cycle length, etc. The DSP 644 can also be configured to calculate or otherwise determine zero-crossings and / or window-crossings and / or crossings of any other threshold voltage levels of BEMF based on BEMF voltage levels included in the feedback, and / or receive such information when included in the feedback.

[0069] The application processor 642 can be configured to calculate or otherwise determine drive portions, ramp-down portions, and high-Z portions of each half-cycle (as updated by the DSP 644). The application processor 642 can also be configured to calculate or otherwise construct voltage waveforms to be applied to the haptic actuator 610 by the haptic driver 620 during the drive portions and ramp-down portions of the half-cycles. The application processor 642 and / or the DSP 644 can be configured to provide control signals to the haptic driver 620 in accordance with the drive portions, ramp-down portions, high-Z portions, and voltage waveforms.

[0070] Each of the haptic driver 620, the feedback sensor 630, and the haptic controller 640 (including one or both of the application processor 642 and the DSP 644) can be implemented as hardware or as a combination of hardware and software (e.g., stored in the memory 650). In an aspect, the application processor 642 and / or the DSP 644 can be implemented in a single integrated circuit (IC), such as in an integrated mobile device processor. Alternatively, the DSP 644 and the memory 650 (e.g., an embedded memory) and the haptic driver 620 can be integrated into one IC, while the application processor 642 can be separate and interact with the memory 650.

[0071] Figure 7 A flow diagram of an example method 700 of generating a voltage waveform for a haptic actuator is illustrated in accordance with one or more aspects of the present disclosure. The illustrated method 700 can be performed by any of the devices and / or systems 600 described above. In an aspect, the memory 650 can be an example of a non-transitory computer-readable medium storing executable instructions for a system and / or device to perform the method 700.

[0072] In block 710, the device can construct a voltage waveform at a resonant frequency of the haptic actuator. The voltage waveform can include one or more half cycles. At least one half cycle can be divided into a drive portion, a ramp down portion, and a high impedance (high Z) portion. During the drive portion, the voltage waveform can be a wave at the resonant frequency. The voltage of the voltage waveform at the termination of the drive portion can be referred to as a termination drive voltage. During the ramp down portion, the voltage of the voltage waveform can change from the termination drive voltage to a termination ramp down voltage. The amplitude of the termination drive voltage (termination drive voltage amplitude) can be greater than the amplitude of the termination ramp down voltage (termination ramp down voltage amplitude). The mag(dv / dt) at the termination of the drive portion can be less than the mag(dv / dt) at the beginning of the ramp down portion. The mag(dv / dt) can represent the magnitude of the change in voltage of the voltage waveform over time. During the high Z portion, the haptic driver 620 can be disabled. In an aspect, an application processor (e.g., application processor 642) and / or a DSP (e.g., DSP 644) can be configured to perform block 710.

[0073] In block 720, the device can generate a control signal corresponding to the voltage waveform. In an aspect, an application processor (e.g., application processor 642) and / or a DSP (e.g., DSP 644) can be configured to perform block 720.

[0074] In block 730, the device can drive the haptic controller with the voltage waveform based on the control signal. In an aspect, a haptic driver (e.g., haptic driver 620) can be configured to perform block 730.

[0075] In block 740, the device can make one or more feedback measurements of the haptic actuator 610 during the high Z portion. In an aspect, a feedback sensor (e.g., feedback sensor 630) can be configured to perform block 740. An example of the feedback sensor can be a BEMF sensor configured to make one or more measurements of the BEMF induced in the haptic actuator 610 during the high Z portion.

[0076] In block 750, the device can update the resonant frequency of the haptic actuator 610 based on the one or more feedback measurements. For example, if the feedback measurements are BEMF measurements, the device can update the frequency of the haptic actuator based on a zero start (i.e., the beginning of the drive portion where the voltage of the voltage waveform is zero volts) and a zero crossing (i.e., the voltage at the termination of the high Z portion where the BEMF crosses zero volts). In an aspect, an application processor (e.g., application processor 642) and / or a DSP (e.g., DSP 644) can be configured to perform block 750.

[0077] As mentioned above, the haptic controller 640 (application processor 642 and / or DSP 644) can be configured to determine the amount of energy present in the haptic actuator 610 based on one or more BEMF measurements. The energy determination can be used to generate a voltage waveform to decelerate the haptic actuator 610.

[0078] It should be pointed out that it is not Figure 7 All the boxes shown need to be executed; that is, some boxes may be optional. Furthermore, for Figure 7 Numerical references to boxes in this document should not be interpreted as requiring that these boxes be executed in a specific order, unless otherwise explicitly indicated. In fact, some boxes can be executed concurrently.

[0079] Figure 8 An example device 800 is illustrated, represented as a series of related functional modules connected by a common bus. Each of the modules may be implemented in hardware or as a combination of hardware and software. For example, these modules may perform... Figure 7 Method 700, and can be used as Figure 6 The system / device 600 can be implemented in any combination of modules. The module for constructing the voltage waveform 810 at the resonant frequency of the haptic actuator may correspond at least in some respects to an application processor (e.g., application processor 642), a DSP (e.g., DSP 644), and / or a memory (e.g., memory 650). The module for generating control signals corresponding to the voltage waveform 820 may correspond at least in some respects to an application processor (e.g., application processor 642), a DSP (e.g., DSP 644), and / or a memory (e.g., memory 650). The module for driving the haptic actuator 830 may correspond at least in some respects to a haptic driver (e.g., haptic driver 620) and / or a memory (e.g., memory 650). The module 840 for performing feedback measurements may correspond at least in some respects to a feedback sensor (e.g., feedback sensor 630) and / or a memory (e.g., memory 650). The module used to update the resonant frequency of the haptic actuator 850 may correspond at least in some respects to an application processor (e.g., application processor 642), a DSP (e.g., DSP 644), and / or a memory (e.g., memory 650).

[0080] Figure 9 Various electronic devices that can be integrated with any of the foregoing systems / devices according to various aspects of this disclosure are illustrated. For example, mobile phone device 902, laptop computer device 904, and terminal device 906 may include a haptic waveform generation system / device 900. Figure 9The devices 902, 904, 906 illustrated in the middle are merely exemplary. Other electronic devices can also include, but are not limited to, a group of devices (e.g., electronic devices) including: a mobile device, a hand-held personal communication systems (PCS) unit, a portable data unit such as a personal digital assistant, a Global Positioning System (GPS) enabled device, a navigation device, a set-top box, a music player, a video player, an entertainment unit, a fixed location data unit such as meter reading equipment, a communications device, a smartphone, a tablet computer, a computer, a wearable device, a server, a router, an electronic device implemented in a motor vehicle (e.g., an autonomous vehicle), an Internet of Things (IoT) device, or any other device that stores or retrieves data or computer instructions, or any combination thereof.

[0081] Specific implementation examples are described in the following numbered clauses:

[0082] Clause 1 : A device comprising: a haptic controller configured to construct a voltage waveform at a resonant frequency of a haptic actuator, and configured to generate a control signal corresponding to the voltage waveform, wherein the voltage waveform comprises at least one half-cycle divided into a drive portion, a ramp-down portion, and a high impedance (high-Z) portion, wherein during the drive portion, the voltage waveform is a wave at the resonant frequency, a voltage of the voltage waveform at an end of the drive portion is a termination drive voltage, and wherein during the ramp-down portion, the voltage of the voltage waveform changes from the termination drive voltage to a termination ramp-down voltage, a magnitude of the termination drive voltage (termination drive voltage magnitude) is greater than a magnitude of the termination ramp-down voltage (termination ramp-down voltage magnitude), and a mag(dv / dt) at the end of the drive portion is less than a mag(dv / dt) at a start of the ramp-down portion, the mag(dv / dt) representing a magnitude of a change in the voltage of the voltage waveform over time; and a haptic driver configured to drive the haptic actuator with the voltage waveform based on the control signal, and configured to be disabled during the high-Z portion.

[0083] Clause 2: The device of clause 1, wherein the haptic actuator is a linear resonant actuator.

[0084] Clause 3: The device of any of clauses 1-2, wherein the voltage waveform is a sine wave during the drive portion.

[0085] Clause 4: The device of any of clauses 1-3, wherein the amplitude of the voltage of the voltage waveform exponentially ramps from the termination drive voltage amplitude to the termination ramp-down voltage amplitude during the ramp-down portion.

[0086] Clause 5: The device of any of clauses 1-4, wherein the amplitude of the voltage of the voltage waveform linearly ramps from the termination drive voltage amplitude to the termination ramp-down voltage amplitude during the ramp-down portion.

[0087] Clause 6: The device of any of clauses 1-5, wherein the termination ramp-down voltage is zero.

[0088] Clause 7: The device of any of clauses 1-5, wherein the termination ramp-down voltage is of opposite polarity to the termination drive voltage.

[0089] Clause 8: The device of any of clauses 1-7, wherein the ramp-down portion includes a braking delay at a termination portion of the ramp-down portion, a termination of the braking delay being a termination of the ramp-down portion, and wherein the voltage of the voltage waveform reaches the termination ramp-down voltage at a start of the braking delay and remains at the termination ramp-down voltage during the braking delay.

[0090] Clause 9: The device of any of clauses 1-8, a feedback sensor configured to take one or more feedback measurements of the haptic actuator during the high-Z portion, wherein the haptic controller is configured to update the resonant frequency of the haptic actuator based on the one or more feedback measurements.

[0091] Clause 10: The device of clause 9, wherein the feedback sensor is a back electromotive force (BEMF) sensor configured to take one or more measurements of the BEMF induced in the haptic actuator, and wherein the haptic controller is configured to update the resonant frequency based on a zero crossing and a zero start, the zero crossing being a termination of the BEMF crossing zero volts in the high-Z portion, and the zero start being a start of the voltage of the voltage waveform being zero volts in the drive portion.

[0092] Clause 11: The device of clause 10, wherein the haptic controller is configured to determine an amount of energy present in the haptic actuator based on the one or more BEMF measurements.

[0093] Clause 12: The device of any of clauses 9-11, wherein for one or more future half cycles, the haptic controller is configured to constitute the voltage waveform at the updated resonant frequency.

[0094] Clause 13: The device of any of clauses 1-12, wherein the drive portion is at least 50% of the half cycle.

[0095] Clause 14: The device of any of clauses 1-13, the ramp down portion ranges substantially from 10 ps to 100 ps.

[0096] Clause 15: The device of any of clauses 1-14, wherein the device is incorporated into a unit selected from the group consisting of a music player, a video player, an entertainment unit, a navigation device, a communications device, a mobile device, a mobile phone, a smart phone, a personal digital assistant, a fixed location terminal, a tablet computer, a computer, a wearable device, an Internet of Things (IoT) device, a laptop computer, a server, and a device in an automotive vehicle.

[0097] Clause 16: A method comprising: constituting a voltage waveform at a resonant frequency of a haptic actuator, wherein the voltage waveform comprises at least one half cycle divided into a drive portion, a ramp down portion, and a high impedance (high Z) portion, wherein during the drive portion, the voltage waveform is a wave at the resonant frequency, a voltage of the voltage waveform at a termination of the drive portion is a termination drive voltage, and wherein during the ramp down portion, the voltage of the voltage waveform changes from the termination drive voltage to a termination ramp down voltage, a magnitude of the termination drive voltage (termination drive voltage magnitude) is greater than a magnitude of the termination ramp down voltage (termination ramp down voltage magnitude), and a mag(dv / dt) at the termination of the drive portion is less than a mag(dv / dt) at a beginning of the ramp down portion, the mag(dv / dt) representing a magnitude of a change in the voltage of the voltage waveform over time; generating a control signal corresponding to the voltage waveform; and driving, using a haptic driver, the haptic actuator with the voltage waveform based on the control signal, wherein during the high Z portion, the haptic driver is disabled.

[0098] Clause 17: The method of clause 16, wherein the haptic actuator is a linear resonant actuator.

[0099] Clause 18: The method of any of clauses 16-17, wherein the voltage waveform is a sinusoidal wave during the drive portion.

[0100] Clause 19: The method of any of clauses 16-18, wherein during the ramp-down portion, the amplitude of the voltage of the voltage waveform exponentially ramps down from the termination drive voltage amplitude to the termination ramp-down voltage amplitude.

[0101] Clause 20: The method of any of clauses 16-19, wherein during the ramp-down portion, the amplitude of the voltage of the voltage waveform linearly ramps down from the termination drive voltage amplitude to the termination ramp-down voltage amplitude.

[0102] Clause 21 : The method of any of clauses 16-20, wherein the termination ramp-down voltage is zero.

[0103] Clause 22: The method of any of clauses 16-20, wherein the termination ramp-down voltage is of opposite polarity to the termination drive voltage.

[0104] Clause 23: The method of any of clauses 16-22, wherein the ramp-down portion includes a braking delay at a termination portion of the ramp-down portion, a termination of the braking delay is a termination of the ramp-down portion, and wherein the voltage of the voltage waveform reaches the termination ramp-down voltage at a start of the braking delay and remains at the termination ramp-down voltage during the braking delay.

[0105] Clause 24: The method of any of clauses 16-23, taking one or more feedback measurements of the haptic actuator during the high-Z portion; and updating the resonant frequency of the haptic actuator based on the one or more feedback measurements.

[0106] Clause 25: The method of clause 24, wherein taking the one or more feedback measurements includes taking one or more measurements of a back electromotive force (BEMF) induced in the haptic actuator, and wherein updating the resonant frequency includes updating the resonant frequency of the haptic actuator based on a zero crossing and a zero crossing, the zero crossing being a start of the drive portion where the voltage of the voltage waveform is zero volts, and the zero crossing being a termination of the high-Z portion where the BEMF crosses zero volts.

[0107] Clause 26: The method of clause 25, the method further comprising determining an amount of energy present in the haptic actuator based on the one or more BEMF measurements.

[0108] Clause 27: The method of any of clauses 24-26, wherein for one or more future half cycles, the voltage waveform is constructed at the updated resonant frequency.

[0109] Clause 28: The method of any of clauses 16-27, wherein the drive portion is at least 50% of the half-cycle.

[0110] Clause 29: The method of any of clauses 16-28, wherein the ramp down portion ranges substantially from 10 ps to 100 ps.

[0111] Clause 30: An apparatus comprising at least one means for performing a method in accordance with any of clauses 16-29.

[0112] Clause 31 : An apparatus comprising a memory and a processor communicatively connected to the memory, the processor configured to perform a method in accordance with any of clauses 16-29.

[0113] Clause 32: A non-transitory computer-readable medium storing code and instructions, the code for an apparatus comprising a memory and a processor communicatively connected to the memory, the instructions stored in the memory and executable by the processor to cause the apparatus to perform a method in accordance with any of clauses 16-29.

[0114] As used herein, the terms "user equipment" (or "UE"), "user device," "user terminal," "client device," "communication device," "wireless device," "wireless communication device," "handheld device," "mobile device," "mobile terminal," "mobile station," "handset," "access terminal," "subscriber device," "subscriber terminal," "subscriber station," "terminal," and variants thereof can interchangeably refer to any suitable mobile or stationary device that can receive wireless communication and / or navigation signals. These terms encompass music players, video players, entertainment units, navigation devices, communication devices, smartphones, personal digital assistants, fixed location terminals, tablet computers, computers, wearable devices, laptop computers, servers, onboard devices in motor vehicles, and / or other types of portable electronic devices that are typically carried by a person and / or have communication capabilities (e.g., wireless, cellular, infrared, short-range wireless radio, etc.). These terms are also intended to include devices that communicate with another device that can receive wireless communication and / or navigation signals such as through a short-range wireless, infrared, wired connection, or other connection, regardless of whether satellite signal reception, assistance data reception, and / or position-related processing occurs at the device or at the other device. Additionally, these terms are intended to include all devices, including wireless and wired communication devices, that are enabled to communicate via a radio access network (RAN), with a core network, and with external networks such as the Internet, and with other devices, including UE. Of course, other mechanisms of connecting to the core network and / or the Internet are also possible for UE, such as over wired access networks, wireless local area network (WLAN) (e.g., based on IEEE 802.11, etc.), and so on. The UE can be embodied by any of a number of types of devices including but not limited to printed circuitry (PC) cards, compact flash devices, external or internal modems, wireless or wireline phones, smartphones, tablet devices, tracking devices, asset tags, and so on. A communication link through which the UE can send signals to a RAN is called an uplink channel (e.g., a reverse traffic channel, a reverse control channel, an access channel, and so on). A communication link through which a RAN can send signals to a UE is called a downlink or forward link channel (e.g., a paging channel, a control channel, a broadcast channel, a forward traffic channel, and so on). As used herein, the term "traffic channel" (TCH) can refer to an uplink / reverse traffic channel or a downlink / forward traffic channel.

[0115] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Likewise, the term “examples” does not mean all examples have to accomplish the particular feature or functionality described. Also, the various features and / or structures of the devices described herein can be combined in any combination.

[0116] It should be noted that the terms “connected,” “coupled,” or any variant thereof, mean any connection or coupling, either direct or indirect, between elements, and can encompass the presence of an intermediate element between two elements that are “connected” or “coupled” together via the intermediate element, unless the connection is expressly disclosed to be a direct connection.

[0117] Any reference to an element herein using a designation such as “first,” “second,” and so forth does not limit the quantity or order of those elements. Rather, these designations are used as a convenient method of distinguishing between two or more elements and / or instances of an element. Also, unless otherwise specified, a set of elements can comprise one or more elements.

[0118] Those skilled in the art will understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0119] Nothing in this application is intended to be dedicated to the public regardless of whether these components, acts, features, benefits, advantages, or equivalents are claimed in the claims.

[0120] In the detailed description above, various features are grouped together in examples. This manner of disclosure should not be used to argue that the claimed examples have more features than the claims expressly recite. Rather, inventive subject matter might be used to realize at least one, or a particular, conjunction of features. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, where each claim can stand on its own as a separate example. Though each claim following the detailed description can stand on its own as a separate example, to the extent that an

[0121] It should also be noted that the methods, systems and devices disclosed in the description or claims can be implemented by a device comprising means for performing the respective actions and / or functionalities of the disclosed methods.

[0122] Further, in some examples, a single action can be subdivided into or contain one or more sub-actions. Such sub-actions can be contained in and can be part of the disclosure of the individual action.

[0123] While the foregoing disclosure shows illustrative examples of the disclosure, it should be noted that various changes and modifications could be made therein without departing from the scope of the disclosure as defined by the appended claims. The functions and / or actions of the methods according to the examples of the disclosure described herein need not be performed in any particular order. Furthermore, notwithstanding be described with or illustrated in a particular arrangement, it should be understood that elements might be used in other arrangements without departing from a spirit or scope of the examples disclosed herein. Also, it will be appreciated that several elements of the disclosure might be interchanged with one another without departing from the scope of the disclosure.

Claims

1. An apparatus comprising: A haptic controller is configured to form a voltage waveform with the resonant frequency of a haptic actuator and to generate a control signal corresponding to the voltage waveform, wherein the voltage waveform includes at least one half-cycle, the at least one half-cycle being divided into a drive portion, a ramp-down portion, and a high-impedance portion, wherein during the drive portion, the voltage waveform is a wave at the resonant frequency, the voltage of the voltage waveform at the end of the drive portion is a termination drive voltage, and wherein during the ramp-down portion, the voltage of the voltage waveform changes from the termination drive voltage to a termination ramp-down voltage, the amplitude of the termination drive voltage being greater than the amplitude of the termination ramp-down voltage, and the mag(dv / dt) at the end of the drive portion being less than the mag(dv / dt) at the beginning of the ramp-down portion, the mag(dv / dt) representing the magnitude of the change in the voltage of the voltage waveform over time; and A tactile driver configured to drive the tactile actuator using the voltage waveform based on the control signal, and configured to be disabled during the high-impedance portion.

2. The device according to claim 1, wherein the tactile actuator is a linear resonant actuator.

3. The device according to claim 1, wherein the voltage waveform is a sine wave during the drive section.

4. The device of claim 1, wherein during the ramp-down portion, the amplitude of the voltage waveform ramps down exponentially from the amplitude of the termination drive voltage to the amplitude of the termination ramp-down voltage.

5. The device of claim 1, wherein during the ramp-down portion, the amplitude of the voltage waveform linearly ramps down from the amplitude of the termination drive voltage to the amplitude of the termination ramp-down voltage.

6. The device of claim 1, wherein the termination ramp descent voltage is zero.

7. The device of claim 1, wherein the polarity of the termination ramp-down voltage is opposite to the polarity of the termination drive voltage.

8. The device according to claim 1, The slope descent portion includes a braking delay at the end of the slope descent portion, the braking delay terminating at the end of the slope descent portion. The voltage of the voltage waveform reaches the termination ramp-down voltage at the start of the braking delay and remains at the termination ramp-down voltage during the braking delay.

9. The device according to claim 1, further comprising: A feedback sensor, configured to perform one or more feedback measurements on the tactile actuator during the high-impedance portion. The haptic controller is configured to update the resonant frequency of the haptic actuator based on the one or more feedback measurements.

10. The device according to claim 9, The feedback sensor is a back electromotive force (BEMF) sensor configured to perform one or more measurements on the BEMF sensed in the tactile actuator, and the tactile controller is configured to update the resonant frequency based on one or more zero crossings, each zero crossing being the termination of the BEMF across zero volts in the high-impedance portion.

11. The device of claim 10, wherein the haptic controller is configured to determine the amount of energy present in the haptic actuator based on one or more measurements of the BEMF.

12. The device of claim 9, wherein for one or more future half-cycles, the haptic controller is configured to form the voltage waveform at the updated resonant frequency.

13. The device of claim 1, wherein the drive portion is at least 50% of the half-cycle.

14. The device of claim 1, wherein the range of the slope descent portion is substantially from 10 μs to 100 μs.

15. The device of claim 1, wherein the device is incorporated into an apparatus selected from the group consisting of: music players, video players, entertainment units, navigation devices, communication devices, mobile devices, mobile phones, smartphones, personal digital assistants, fixed-location terminals, tablet computers, computers, wearable devices, Internet of Things (IoT) devices, laptop computers, servers, and devices in motor vehicles.

16. A method comprising: A voltage waveform is constructed using the resonant frequency of the haptic actuator, wherein the voltage waveform includes at least one half-cycle, the at least one half-cycle being divided into a driving portion, a ramp-down portion, and a high-impedance portion, wherein during the driving portion, the voltage waveform is a wave at the resonant frequency, the voltage of the voltage waveform at the end of the driving portion is a termination driving voltage, and wherein during the ramp-down portion, the voltage of the voltage waveform changes from the termination driving voltage to a termination ramp-down voltage, the amplitude of the termination driving voltage is greater than the amplitude of the termination ramp-down voltage, and the mag(dv / dt) at the end of the driving portion is less than the mag(dv / dt) at the beginning of the ramp-down portion, wherein mag(dv / dt) represents the magnitude of the change in the voltage of the voltage waveform over time; Generate a control signal corresponding to the voltage waveform; as well as The tactile driver is used to drive the tactile actuator using the voltage waveform based on the control signal, wherein the tactile driver is disabled during the high impedance portion.

17. The method of claim 16, wherein the haptic actuator is a linear resonant actuator.

18. The method of claim 16, wherein the voltage waveform is a sine wave during the driving portion.

19. The method of claim 16, wherein during the ramp-down portion, the amplitude of the voltage waveform ramps down exponentially from the amplitude of the termination drive voltage to the amplitude of the termination ramp-down voltage.

20. The method of claim 16, wherein during the ramp-down portion, the amplitude of the voltage waveform linearly ramps down from the amplitude of the termination drive voltage to the amplitude of the termination ramp-down voltage.

21. The method of claim 16, wherein the termination ramp descent voltage is zero.

22. The method of claim 16, wherein the polarity of the terminating ramp-down voltage is opposite to the polarity of the terminating drive voltage.

23. The method according to claim 16, The slope descent portion includes a braking delay at the end of the slope descent portion, the braking delay terminating at the end of the slope descent portion. The voltage of the voltage waveform reaches the termination ramp-down voltage at the start of the braking delay and remains at the termination ramp-down voltage during the braking delay.

24. The method according to claim 16, further comprising: One or more feedback measurements are performed on the haptic actuator during the high-impedance portion, and The resonant frequency of the haptic actuator is updated based on the one or more feedback measurements.

25. The method according to claim 24, Performing the one or more feedback measurements includes performing one or more measurements of the back electromotive force (BEMF) induced in the haptic actuator, and Updating the resonant frequency includes updating the resonant frequency of the haptic actuator based on one or more zero crossovers, each zero crossover being the termination point of the BEMF crossing zero volts in the high-impedance portion.

26. The method of claim 24, wherein for one or more future half-cycles, the voltage waveform is constructed with the updated resonant frequency.

27. The method of claim 16, wherein the driving portion is at least 50% of the half-cycle.

28. The method of claim 16, wherein the slope descent portion ranges substantially from 10 μs to 100 μs.

29. An apparatus comprising: A component for constructing a voltage waveform at the resonant frequency of a haptic actuator, wherein the voltage waveform includes at least one half-cycle, the at least one half-cycle being divided into a drive portion, a ramp-down portion, and a high-impedance portion, wherein during the drive portion, the voltage waveform is a wave at the resonant frequency, the voltage of the voltage waveform at the end of the drive portion is a termination drive voltage, and wherein during the ramp-down portion, the voltage of the voltage waveform changes from the termination drive voltage to a termination ramp-down voltage, the amplitude of the termination drive voltage being greater than the amplitude of the termination ramp-down voltage, and the mag(dv / dt) at the end of the drive portion being less than the mag(dv / dt) at the beginning of the ramp-down portion, the mag(dv / dt) representing the magnitude of the change in the voltage of the voltage waveform over time; A component used to generate a control signal corresponding to the voltage waveform; and A component for driving the haptic actuator with the voltage waveform based on the control signal, wherein the component for driving is disabled during the high impedance portion.

30. A non-transitory computer-readable medium storing computer-executable instructions for a device, the computer-executable instructions comprising: One or more instructions for instructing the device to form a voltage waveform at the resonant frequency of the haptic actuator, wherein the voltage waveform includes at least one half-cycle, the at least one half-cycle being divided into a drive portion, a ramp-down portion, and a high-impedance portion, wherein during the drive portion, the voltage waveform is a wave at the resonant frequency, the voltage of the voltage waveform at the end of the drive portion is a termination drive voltage, and wherein during the ramp-down portion, the voltage of the voltage waveform changes from the termination drive voltage to a termination ramp-down voltage, the amplitude of the termination drive voltage being greater than the amplitude of the termination ramp-down voltage, and the mag(dv / dt) at the end of the drive portion being less than the mag(dv / dt) at the beginning of the ramp-down portion, the mag(dv / dt) representing the magnitude of the change in the voltage of the voltage waveform over time; One or more instructions are used to instruct the device to generate a control signal corresponding to the voltage waveform; and One or more instructions are used to instruct the device to use a haptic driver to drive the haptic actuator with the voltage waveform based on the control signal, wherein the haptic driver is disabled during the high impedance portion.

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