Patent Description:
<CIT> describes a piezoelectric laminate composite which enables the deflection generated to provide greater work energy. The composites are fabricated as piezoelectric bender-elements having a mechanical bias or radius of curvature. More specifically, the composite fabrication method of the present invention uses pressure and temperature to bond and anneal a plurality of layers of composite materials including a thin strip of piezoelectric material into piezoelectric bender-elements. In one example, the piezoelectric laminate composite comprises thin layers of a plastic piezoelectric material, such as a film of polyvinylidene fluoride (PVDF), and thin layers of a piezoelectric material having a high Young's modulus, such as ceramic lead zirconate titanate (PZT).

<CIT> describes a localized multimodal haptic system which includes one or more electromechanical polymer (EMP) transducers, each including an EMP layer, such as an electrostrictive polymer active layer. In some applications the EMP transducer may perform an actuator function or a sensor function, or both. The EMP polymer layer has a first surface and a second surface on which one or more electrodes are provided. The EMP layer of the EMP actuator may be <NUM> microns thick or less. The EMP transducers may provide local haptic response to a local a stimulus. In one application, a touch sensor may be associated with each EMP transducer, such that the haptic event at the touch sensor may be responded to by activating only the associated EMP transducer. Furthermore, the EMP transducer may act as its own touch sensor. A variety of haptic responses may be made available. The EMP transducers may be used in various other applications, such as providing complex surface morphology and audio speakers.

The development of artificial haptics faces the challenge of accurately conveying perception to a user. This may include artificial stimuli, artificial sensory feedback, artificial sensation, etc. By using a single haptic actuator, the user experience is limited by the properties of the actuator. For example, piezo-electric polymers, such as polyvinylidene fluoride (PVDF) can provide a wide-band of actuation, but may be limited in actuation output force. Conversely, piezo-electric ceramics, such as lead zirconate titanate (PZT), can generate a strong actuation force, but may not be well-suited for subtle information delivery due to the nature of its mechanical rigidity. Linear resonant actuators (LRA) may have fast response times, but may be limited by a narrow band of actuation frequencies. Eccentric rotating mass vibration motors (ERM) are DC controlled, and thus mainly suitable for continuous output applications. Further, ERMs may have limited long-term durability due to a susceptibility to wear. Voice coil haptic actuators are generally bulky, and thus not well-suited for wearable applications.

This challenge may be exemplified in various fields. For example, virtual reality (VR) and artificial reality (AR) applications may provide wearable devices that offer the user tactile feedback, haptics, proprioception, etc. in order to generate a more immersive environment. Also, soft robotics applications may be tasked with automating the handling and grasping of soft or fragile objects. Both applications may involve the application of delicate forces via actuation and also receiving feedback as to what is the object being grasped and how hard the object is being grasped. VR and AR applications further may involve providing textural simulation to the user to generate the sensation of grasping a virtual object, while soft robotics may involve identifying small intricate features on a surface to identify and dictate how much force can safely be applied to an object.

Accordingly, examples are disclosed of piezo-electric polymers and piezoelectric ceramics combined into a single device, thereby saving valuable space and delivering a variety of experiences within a single electronic package. This may provide for actuation within a wide output frequency band (e.g., <NUM> to <NUM>), and be tunable to two separate frequency ranges that are independent of each other. For wearable devices, softness may be maintained against a user's skin via a piezo-electric polymer stack while providing the requisite compliance to address a variety of unique haptic experiences and to enhance simulated touch and sensation. For soft robotics applications, the combined device may allow feedback at the point of contact to modulate the force applied to an object, thereby allowing more sensitive and reactive grasping methods. In addition to wearable and soft robotic devices, numerous other platforms may benefit from the ability to deliver multiple haptic experiences, such as hand-held, computing, industrial, medical, and automotive, to more closely replicate the multitude of receptors that resides within the human touch experience. Such multiple tactile haptic interfaces may be incorporated into automotive controllers, flight controllers, drone controllers, marine controllers, surgical controllers, gaming controllers, and other user interfaces.

<FIG> schematically shows an example wearable device <NUM> that includes sensors and actuators. Wearable device <NUM> takes the form of a glove comprising a plurality of combined haptic actuators <NUM> and controller <NUM>. In other examples, a wearable device may take the form of a sleeve worn around an arm, a leg, and/or another body part, a sock, a headband, etc. Combined haptic actuators <NUM> are shown positioned in locations corresponding to fingertips and joints of the thumb, forefinger, and middle finger, but may be positioned at any suitable locations, (e.g., knuckles) in other examples. As described in more detail with regard to <FIG>, each combined haptic actuator <NUM> may have a user-adjacent side (e.g., proximal to and/or interfacing with the user's skin) and a user-distal side, opposite the user-adjacent side. In some examples, wearable device <NUM> may include additional sensors (e.g., flex sensors, pressure sensors, touch sensors, inertial measurement sensors) and/or actuators (e.g. motion-restricting devices such as electrostatic clutches).

Controller <NUM> may be configured to control the application of voltages to combined haptic actuators <NUM>. Application of voltages may be performed via controller <NUM> in response to signals received by the various sensors of wearable device <NUM>. As described in more detail below with regard to <FIG> and <FIG>, combined haptic actuators <NUM> may both provide a signal to controller <NUM> and receive a signal from controller <NUM>. The signals provided by controller <NUM> may be based at least in part on the signals received from combined haptic actuators <NUM> and/or signals received from other sensors of wearable device <NUM>.

In some examples, wearable device <NUM> may be communicatively coupled to one or more computing devices, such as a head-mounted display system configured to present an augmented or virtual reality environment to a user. Wearable device <NUM> may be configured to further augment such an augmented, mixed, or virtual reality experience by providing a physical sensation responsive to user interaction with virtual imagery. Actuation of combined haptic actuators <NUM> may be used to generate related sensations of touch, texture, impact, etc..

<FIG> schematically shows an example haptic feedback system <NUM>. Haptic feedback system <NUM> includes a first haptic actuator <NUM> coupled to a controller <NUM> via a first set <NUM> of two or more electrodes. Haptic feedback system <NUM> further includes a second haptic actuator <NUM> coupled to controller <NUM> via a second set <NUM> of two or more electrodes.

The first haptic actuator <NUM> is physically coupled to second haptic actuator <NUM> in a stack <NUM> arrangement. First haptic actuator <NUM> and second haptic actuator <NUM> are coupled together via adhesive layer <NUM>.

The second haptic actuator <NUM> comprises a more rigid material than first haptic actuator <NUM>. The first haptic actuator <NUM> is a piezoelectric polymer, such as PVDF, while second haptic actuator <NUM> is a piezoelectric ceramic material, such as PZT. As such, first haptic actuator <NUM> may be positioned on a user-adjacent side <NUM> of stack <NUM>. Second haptic actuator <NUM> may be considered to be positioned on a user-distal side of stack <NUM>, opposite user adjacent side <NUM>.

First haptic actuator <NUM> may be fabricated from any suitable soft polymer, such as PVDF, acrylates, silicones, etc. In contrast, second haptic actuator <NUM> may be fabricated from any suitable piezoelectric ceramic material, such as PZT (lead zirconium titanite), KNN (potassium sodium niobite), BNT (barium neodymium titanite), BNN (barium sodium niobite), BST (barium strontium titanite), BT (barium titanite), BZT (barium zirconium titanite), etc..

In such an example, the elastic modulus for first haptic actuator <NUM> may be significantly different than for second haptic actuator <NUM>. As such, they may experience significant displacement relative to one another upon actuation. Accordingly, adhesive layer <NUM> is selected from a material or materials that mitigate relative displacement of the two actuators due to elastic modulus mismatch. According to the claimed invention, adhesive layer <NUM> comprises a soft silicone adhesive. In this way, adhesive layer <NUM> may stretch differently on both faces without breaking down, thus helping to prevent delamination between the two actuators. In this manner, adhesive layer <NUM> maintains the physical alignment between the two actuators so that the haptic output spatial relationship between the two actuators does not shift.

Each of first haptic actuator <NUM> and second haptic actuator <NUM> may comprise a multi-layer structure. For example, first haptic actuator <NUM> is shown with three conductors <NUM> sandwiched in between four layers of piezoelectric polymer material <NUM>. Second haptic actuator <NUM> is shown with one conductor <NUM> sandwiched in between two adjacent layers of piezoelectric ceramic material <NUM>. However, the number of conductor layers and piezoelectric layers depicted is shown merely for example, and more or fewer layers may be used. Conductors <NUM> and <NUM> may be fabricated from any suitable material(s), such as copper, silver, carbon, etc. As one example, for first haptic actuator <NUM>, flexible silver electrodes may be screen printed between layers of PVDF. Additionally or alternatively, sputtering or other deposition methods may be used to deposit conductive electrodes onto piezoelectric polymer films. For second haptic actuator <NUM>, each conductor <NUM> may fill the entire space between the piezoelectric ceramic layers <NUM>. For example, copper conductors may be formed via electroless plating between layers <NUM>.

First set of electrodes <NUM> and second set of electrodes <NUM> are each shown as having a pair of electrodes. However, more electrodes may be used for each set, or the sets may have one or more shared electrodes. As shown, in some examples, each set of electrodes is configured to bi-directionally carry information (e.g., to and from controller <NUM>). Controller <NUM> is configured to provide a first drive signal to first haptic actuator <NUM> via first set of electrodes <NUM>, and to provide a second drive signal, different from the first drive signal, to second haptic actuator <NUM> via second set of electrodes <NUM>. Controller <NUM> is further configured to receive a first feedback signal from first haptic actuator <NUM> via first set of electrodes <NUM>, and to receive a second feedback signal, from second haptic actuator <NUM> via second set of electrodes <NUM>.

The feedback signals may be derived from deformation at the haptic actuators. Based on piezoelectric physics, when force is applied to each haptic actuator structure by touching, tapping, etc., charge will be generated and transported to the coupled electrode set. By sensing the amount of charges flowing across the two electrodes, the value of force may be accurately detected. Based on the deformation differences in the materials, second haptic actuator may give highly attenuated feedback, while the first haptic actuator may give lower attenuated, longer wavelength feedback.

As such, the controller may be used to both receive and output voltages. For example, each electrode may trace to a universal i/o pin at controller <NUM> via an A/D converter. Controller <NUM> may read a voltage at that pin (feedback signal) and/or provide a drive signal via the pin.

The first drive signal and second drive signal may comprise different voltages, frequencies, and/or waveform shapes such that different information is delivered to the first and second haptic actuators, thus creating different types of haptic output. As an example, first haptic actuator <NUM> may be used to generate continuously modulated vibration. In such an example, the first drive signal may comprise a generally sinusoidal waveform with a frequency ranging from <NUM> to <NUM>, although other waveforms and frequencies may be used. The relatively larger bending deformation of the second haptic actuator <NUM> may be used to generate a "burst" experience, such as a kick, sudden knocking, etc. In such an example the second drive signal may comprise a pulse waveform within a frequency range of <NUM> to <NUM>. Selective triggers determined at controller <NUM> may thus give either subtle or very strong feedback. The amplitudes of the first and second drive signals may vary based on the materials included in the first and second haptic actuators. The specific frequencies used may be based on the natural resonance frequencies of the respective haptic actuators.

Haptic feedback system <NUM> may thus help to provide a spectrum of possible feedback at a position in a wearable device (e.g., based on a broad range of deformation), and by actuating a broader palate of features to represent a texture or virtual contact. The feedback signals may be used in part to generate control signals for other devices within the wearable device (e.g., electrostatic clutches). Additionally, it is noted that PZT actuators may be utilized over a range of <NUM>-100V, depending on the number of PZT layers. Likewise, PVDF actuators may be utilized within a range of <NUM>-300V, and thereby may provide relatively lower operating voltages than other piezoelectric materials.

The haptic feedback system described with regard to <FIG> may enable one or more control methods. As an example, <FIG> depicts a flow chart for a method <NUM> of operating a haptic feedback system. Method <NUM> may be executed by one or more controllers, such as controller <NUM>, and may be executed in the context of a wearable device, such as wearable device <NUM>.

At <NUM>, method <NUM> includes receiving, via a first set of electrodes, a first feedback signal indicating a force at a first haptic actuator within a stack. For example, as a force is applied on first haptic actuator <NUM>, electrical charges are generated across first set of electrodes <NUM>. The electrical signal is sent to controller <NUM>.

At <NUM>, method <NUM> includes receiving, via a second set of electrodes, a second feedback signal indicating a force at a second haptic actuator within the stack. For example, as a force is applied on second haptic actuator <NUM>, electrical charges are generated across second set of electrodes <NUM>. The electrical signal is sent to controller <NUM>.

At <NUM>, method <NUM> includes determining a first drive signal and a second drive signal, different from the first drive signal, based on the first feedback signal and the second feedback signal. For example, controller <NUM> may determine a first force based on the first feedback signal and a second force based on the second feedback signal. Based at least in part on the first and second determined forces, the controller may generate first and second drive signals to be applied to the first and second haptic actuators within the stack. The frequency, force, and waveform pattern of the first and second drive signals may be different and may be generated independently. However, in some examples, one or more of the first and second drive signals may be generated based on one or both the first and second feedback signals.

At <NUM>, method <NUM> includes providing the first drive signal to the first haptic actuator via the first set of two or more electrodes, and providing the second drive signal to the second haptic actuator via the second set of two or more electrodes. The first and second drive signals may serve to actuate (e.g., deform) the first and second haptic actuators, respectively, thereby generating haptic output to a force applying object contacting the stack. For example, forces may be determined at a knuckle position in a wearable device with a glove form, and a response provided at the same location based on the determined forces. The first and second drive signals may be updated continuously, periodically, or based on a threshold change in perceived force.

In another example, a combined haptic actuator maybe implemented for real-world scenarios wherein feedback and output control are desired at the same point of contact. For example, combined haptic actuators may be embedded in furniture or auto interiors. As an example, a massage chair may have a plurality of combined haptic actuators embedded below an upholstered surface. The position of the user may be detected via the force applied to the haptic actuators. The actuation signal applied to those actuators may then be adjusted based on the position of the user.

As described above, soft robotic applications may also benefit from the implementation of combined haptic actuators. Human fingers have hundreds of nerve endings just below the surface of the skin. Some are used for detecting sensation, others for applying force via muscle contractions. Combining both functions into one device may provide for similar capabilities in a soft robotic device, thereby allowing for feedback generation and suitable responsive force application in real time.

<FIG> schematically shows an example soft robotics device <NUM>. Soft robotics device is shown in the form of a claw that may be used for touching, grasping, or otherwise manipulating physical objects. Soft robotics device <NUM> is depicted as having three grasping claws, 402a, 402b, and 402c. Each grasping claw may be independently moved, extended, and brought together via a plurality of joints. This movement may be controlled by signals provided by controller <NUM>. Controller <NUM> may be a part of haptic feedback system <NUM>.

Movement of grasping claws 402a, 402b, and 402c may provide a basis for gross adjustments to the conformation of soft robotics device <NUM> in manipulating an object. Fine adjustments may be triggered by haptic feedback system <NUM>, which also includes haptic actuators 408a, 408b, and 408c. Haptic actuators 408a, 408b, and 408c may serve as robotic fingertips which can operate to both sense and apply force on an object. Although depicted as having one haptic actuator per grasping claw, other examples may include two or more haptic actuators per grasping claw.

<FIG> schematically depict another example haptic feedback system <NUM> which is outside the scope of the claimed invention. Haptic feedback system includes a first haptic actuator <NUM> and a second haptic actuator <NUM> that is coupled to first haptic actuator <NUM>. In this example, first haptic actuator may be a piezoelectric polymer (e.g., PVDF, silicon film), while second haptic actuator <NUM> may be a piezoelectric ceramic (e.g., PZT). First haptic actuator <NUM> is coupled to controller <NUM> via a first set of two or more electrodes <NUM>, while second haptic actuator <NUM> is coupled to controller <NUM> via a second set of two or more electrodes <NUM>.

In this example, a rigid substrate <NUM> is coupled to an outer region of first haptic actuator <NUM>. Rigid substrate <NUM> may be a thin disc manufactured from metal, ceramic, a rigid polymer (e.g., ABS), or other suitable material. A rigid cap <NUM> is coupled to an inner region of first haptic actuator <NUM>. Rigid cap <NUM> may be manufactured from the same, or a similar material as rigid substrate <NUM>. Second haptic actuator <NUM> is shown coupled to first haptic actuator <NUM> via rigid cap <NUM>. A compressible member <NUM> is depicted as being coupled between rigid substrate <NUM> and rigid cap <NUM>. Although depicted as a spring, compressible member <NUM> may be formed from any other suitable material, such as a compressible foam or other resilient, compressible material.

Control signals from controller <NUM> may be used to actuate first haptic actuator <NUM>. As shown in <FIG>, actuation of first haptic actuator <NUM> will cause the piezoelectric polymer to soften, and thus to elongate. Accordingly, compressible member <NUM> will expand, driving rigid cap <NUM> away from rigid substrate <NUM>. Depending on the spring constant of compressible member <NUM>, a high or low force may be generated. Providing a rigid substrate <NUM> may allow this force to be provided in one direction (away from the substrate).

As such, haptic feedback system <NUM> may provide for a control loop where force is sensed and then adjusted. Controller <NUM> may be configured to receive a first deformation signal from second haptic actuator <NUM> via the second set of two or more electrodes <NUM>, and to provide a first drive signal to first haptic actuator <NUM> via first set of two or more electrodes <NUM>. The first drive signal may be based at least in part on the first deformation signal. In this way, second haptic actuator <NUM> may sense a pressure, and a drive signal sent to first haptic actuator <NUM> may modulate this pressure, by either elongating, retracting, or maintaining the position of compressible member <NUM> via actuation of first haptic actuator <NUM>.

In soft robotics systems, such as system <NUM>, where multiple combined actuators are applied, the deformation signals from one or more additional actuators may be used to generate respective drive signals. In some examples, a second drive signal may be applied to second haptic actuator <NUM>. This second drive signal may be based on one or more deformation signals. In some examples, first haptic actuator <NUM> may also provide a deformation signal to controller <NUM>, though this signal may be much smaller (e.g. orders of magnitude) than those generated by second haptic actuator <NUM>. In non-wearable systems, higher input voltages may be used to drive first haptic actuator <NUM>. Thus a more robust material such as silicon film, which may utilize an input voltage of -<NUM>-2000V may be preferred over PVDF.

This visual representation may take the form of a graphical user interface (GET).

Claim 1:
An electronic device, comprising:
a haptic feedback system (<NUM>), comprising
a first haptic actuator (<NUM>) comprising a piezoelectric polymer:
a second haptic actuator (<NUM>) comprising a piezoelectric ceramic:
a soft silicone adhesive layer (<NUM>) between the first haptic actuator and the second haptic actuator, configured to mitigate displacement of the first haptic actuator and the second haptic actuator relative to one another due to elastic modulus mismatch between the first haptic actuator and the second haptic actuator; and
a controller (<NUM>) connected to the first haptic actuator by a first set of two or more electrodes (<NUM>) and to the second haptic actuator by a second set of two or more electrodes (<NUM>), the controller configured to provide a first drive signal to the first haptic actuator via the first set of electrodes, and to provide a second drive signal, different from the first drive signal to the second haptic actuator via the second set of electrodes, wherein the first haptic actuator, the soft silicone adhesive layer, and the second haptic actuator are arranged as a stack.