Piezoelectric material-based touchpad devices

Abstract

A piezoelectric material-based touchpad, comprising: a base structure; a plurality of support members secured in the base structure; a plurality of sensors; wherein each of the plurality of sensors is disposed on a different one of the plurality of support members, wherein each of the plurality of sensors comprises a piezoelectric material; an upper panel supported by the plurality of sensors; and a plurality of electrical insulation members; wherein each of the plurality of electrical insulation members is disposed on a different one of the plurality of sensors to insulate said sensor from the upper panel.

Description

PIEZOELECTRIC MATERIAL-BASED TOUCHPAD DEVICESRELATED APPLICATION

[0001] This application claims priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63 / 519,126 filed August 11, 2023, the contents of which are herein incorporated by reference.FIELD OF THE DISCLOSURETechnical field

[0002] The present disclosure generally relates to the field of touchpad devices and, more particularly, to piezoelectric material-based touchpad devices.BRIEF SUMMARY OF THE DISCLOSURE

[0003] In a preferred aspect, the present disclosure comprises a piezoelectric material-based touchpad, comprising: a base structure; a plurality of support members secured in the base structure; a plurality of sensors; wherein each of the plurality of sensors is disposed on a different one of the plurality of support members, wherein each of the plurality of sensors comprises a piezoelectric material; an upper panel supported by the plurality of sensors; and a plurality of electrical insulation members; wherein each of the plurality of electrical insulation members is disposed on a different one of the plurality of sensors to insulate said sensor from the upper panel.

[0004] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the piezoelectric material comprises lead zirconium titanate (PZT).

[0005] In yet another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the base structure defines a rectangle and wherein each of the support members is disposed at a corner of the rectangle.

[0006] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.

[0007] In a further preferred aspect of a piezoelectric material-based touchpad of the present disclosure, each of the plurality of sensors is part of a sensor structure comprising a layer of PZT material disposed between first and second layers of an electrically conductive material, wherein one or both of the first and second layers of a conductive material is connected to one or more wires for signal collection from the piezoelectric sensor.

[0008] In another preferred aspect, the piezoelectric material-based touchpad of the present disclosure further comprises a plurality of vibration dampening pads, wherein each one of the plurality of vibration dampening pads is disposed under a respective one of the plurality of support members.

[0009] In another preferred aspect, the present disclosure comprises a piezoelectric material-based touchpad, comprising: a base structure; a plurality of unimorph support members secured in the base structure; a plurality of unimorph sensors; wherein each of the plurality of unimorph sensors is disposed on a different one of the plurality of unimorph support members, wherein each of the plurality of unimorph sensors comprises a piezoelectric material bonded to a metal plate and one or more voltage collection electrodes attached to each unimorph sensor; and an upper panel supported by the plurality of unimorph sensors.

[0010] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the piezoelectric material comprises lead zirconium titanate (PZT).

[0011] In yet another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the metal plate comprises aluminum.

[0012] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the metal plate defines a first area and the piezoelectric material defines a second area and wherein the first area is larger than the second area.

[0013] In a further preferred aspect of a piezoelectric material-based touchpad of the present disclosure, a small gap about 0.05 inches wide is disposed between each unimorph sensor and each unimorph support structure.

[0014] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.

[0015] In yet another preferred aspect, the present disclosure comprises a piezoelectric material-based touchpad, comprising: a base structure; a plurality of vertically oriented support members secured to an outside surface of the base structure; wherein each of the support members has a pointed side edge; a plurality of sensors; wherein each of the plurality of sensors is disposed between a different one of the plurality of support members and a side of the base structure, wherein each of the plurality of sensors comprises a piezoelectric material and one or more voltage collection electrodes attached to each sensor; and an upper panel supported by the pointed side edge of each of the plurality of vertically oriented support members.

[0016] In another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the piezoelectric material comprises lead zirconium titanate (PZT).

[0017] In yet another preferred aspect of a piezoelectric material-based touchpad of the present disclosure, a gap is disposed between each of the plurality of sensors and the base structure.

[0018] In a further preferred aspect of a piezoelectric material-based touchpad of the present disclosure, the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.BRIEF DESCRIPTION OF THE DRAWINGS[000191 For the present disclosure to be easily understood and readily practiced, the present disclosure will now be described for purposes of illustration and not limitation in connection with the following figures, wherein:

[0020] FIG. 1 is a top perspective view of a preferred embodiment of a piezoelectric material-based touchpad device that uses a compression mode sensor;

[0021] FIG. 2 is a top perspective view of a base of a preferred embodiment of a piezoelectric material-based touchpad device that uses a compression mode sensor;

[0022] FIG. 3 is a cross-sectional view of a preferred sensor for a preferred embodiment of a piezoelectric material-based touchpad device that uses a compression mode sensor;

[0023] FIG. 4 is another top perspective view of a base of a preferred embodiment of a piezoelectric material-based touchpad device that uses a compression mode sensor;

[0024] FIG. 5 is a top perspective view of another preferred embodiment of a piezoelectric material-based touchpad device that uses a bending mode and utilizes transverse mode (d31) of piezoelectric ceramics;

[0025] FIG. 5A is a cross-sectional view of a unimorph support member of the piezoelectric material -based touchpad device of FIG. 5;

[0026] FIG. 6 shows perspective views of the components of the piezoelectric material-based touchpad device of FIG. 5;

[0027] FIG. 7 illustrates a preferred structure of each unimorph sensor of the piezoelectric material-based touchpad device of FIG. 5;

[0028] FIG. 8 illustrates a preferred structure of the piezoelectric material-based touchpad device of FIG. 5, wherein each comer of the upper panel is supported by and / or is connected to a point of one of the unimorph sensors;

[0029] FIG. 9 is a top perspective view of yet another preferred embodiment of a piezoelectric material-based touchpad device that employs a side compression mode, which uses transverse shear mode (d35) of piezoelectric ceramics;

[0030] FIG. 10 is an exploded view of the piezoelectric material-based touchpad device of FIG. 9;

[0031] FIG. 11 is a side view of a PZT sensor of the piezoelectric material-based touchpad device of FIG. 9;

[0032] FIG. 12 shows the round and square PZT sensors used in an Ansys simulation;

[0033] FIG. 13 shows an example of 4 different normal distributions with different levels of noise: 84 where [μ=0, σ2=0.2; 86 where μ=0, σ2=1.0; 88 where μ=0, σ2=5.0; and 89 where μ= -2, σ2=0.5;

[0034] FIG. 14 shows a preferred print head employing the FDM process comprising a base, a support material nozzle for dispensing support material, and a build material nozzle for dispensing build material;

[0035] FIG. 15 shows the force on a plane having width (W) and length (L) where the force is applied at a given point downward.DETAILED DESCRIPTION

[0036] The following descriptions are of exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims.

[0037] The present disclosure includes three different preferred embodiments of piezoelectric material-based touchpads using three distinct sensors comprising piezoelectric sensors, each of which uses a different mode of the piezoelectric material lead zirconium titanate (PZT), but any material with piezoelectricity properties can be used.

[0038] The first preferred embodiment preferably uses a compression mode sensor and utilizes the longitudinal mode (d33) of piezoelectric ceramics. This mode utilizes the mechanical stress applied along the z-direction of the PZT crystal.

[0039] The second preferred embodiment uses a bending mode and utilizes transverse mode (d31) of piezoelectric ceramics. This mode utilizes stress applied along the x-direction. The third preferred embodiment employs a side compression mode, which uses transverse shear mode (d35) of piezoelectric ceramics. This mode utilizes stress applied in the y-direction. Each structural design of the three preferred embodiments compresses the piezoelectric sensor in a different way. Among these designs, the longitudinal mode has the highest charge accumulation, as it is in the direction of d33. Among the three preferred embodiments, PZTs'' limitations, such as thermal transients, are not pronounced in the case of a touchpad device.

[0040] FIGS. 1-4 show a first preferred embodiment of a piezoelectric material-based touchpad device 10 that uses a compression mode sensor. The first step to materialize this design is to design the supporting base structure 12, shown in FIGS. 1-2. The base 12 is preferably square or rectangular in shape, with 5.2 inches in width and length. The wall 13 preferably is 0.1 inches thick. Preferably, there are four pillars or support members 14 in the corners of the structure 12. These four support members 14 contain the placeholder for piezoelectric sensors 16 which preferably comprise PZT, but any material with piezoelectricity properties can be used. The top layer or upper panel 20 is preferably an aluminum metal plate and is preferably 0.08 inches to 1.0 inch thick. The horizontal supporting structure 12 ensures that the pillars 14 do not move sideways when a force is applied from above. This can ensure the force is applied directly to the base 12 in a downward direction. When shifting sideways, the force would resolute into two different directions and decrease the accuracy of the position determination. Along the shielding wall 13, there is a cut-out 15 for a wire connection.

[0041] Preferably, as shown in FIG. 4, there are vibration dampening pads or bumper pads 30 added on the bottom of the pillars 14. Pads 30 can eliminate resonated vibration, such as vibration from the table or surface on which the piezoelectric material-based touchpad device 10 is supported, as well as the bouncing behavior of the sensor 16 when force is applied. Testing with pads 30 has shown that the loss of voltage output is negligible.

[0042] Preferably, upper panel 20 is 5 inches square and supporting structure 12 is 5.2 inches square with each pillar 14 being 0.1 inches taller than the rest supporting structure 12. Piezoelectric material-based touchpad device 10 is the simplest one among many configurations. But it has excellent electrical performance under pressure because PZT's electrical coupling effect is the most pounced in the d33 direction. Upper panel 20 preferably is made of aluminum which is preferred for its high tensile strength and low density among metals. However, Upper panel 20 can be made from any other material as long as the replacement material's tensile strength is not too weak to deform below the supporting structure 12. In other words, if the new material does not deform below the height of sensors 16 or destroy the sensors 16, it can substitute for aluminum. Possible replacement materials for upper panel 20 include steel, glass, titanium, etc.

[0043] FIG. 3 shows a side cross-sectional view of a preferred structure for the sensors 16 disposed atop a pillar or support member 14. As shown therein, a piezoelectric material 18, preferably PZT, is sandwiched between two layers of electrically conductive materials 24, 26 which are preferably copper films. The copper films 24, 26 are used to cover the top and bottom of the piezoelectric material 18. Preferably, copper films 24, 26 are extended horizontally to connect to wires 32 for signal collection (wires shown in FIG. 4).

[0044] In this first preferred embodiment of a piezoelectric material-based touchpad device 10, the preferred length of the side of each square of piezoelectric material 18 of sensor 16 is 0.43 inches with a thickness of piezoelectric material 18 preferably being 0.035 inches. Each copper layer 24, 26 has a preferred length of0.86 inches and a preferred thickness of 9 mils (0.009 inches) thick. More preferably, each copper layer 24, 26 is as thin as possible without being prone to tearing during use. If the PZT piezoelectric material 18 is thicker, it can provide a higher voltage output, but the risk of the PZT ceramic breaking will be higher as it will become more brittle.

[0045] In this first preferred embodiment of a piezoelectric material-based touchpad device 10, the charge will accumulate for deformation regardless of the force directions. Preferably, PZT films 18 are placed in orientation with a positive charge on top and a negative charge on the bottom. This is designed for the purpose of an easier assembly process.

[0046] Preferably, as shown in FIG. 3, each sensor 16 is covered by an electrical insulation material 22, such as translucent tape, that is larger than PZT film 18. This will act as an insulation layer to ensure the copper films 24, 26 do not leak charges to the aluminum upper panel 20. The translucent tape 22 is preferably rated to be 3mil (0.003 inches) thick and about 1 inch square. The aluminum upper panel 20 is preferably about 5 inches square and slightly smaller compared to the supporting structure 12.

[0047] FIGS. 5-8 show a second preferred embodiment of a piezoelectric material-based touchpad device 40 that uses a bending mode and utilizes transverse modeof piezoelectric ceramics. This preferred embodiment of piezoelectric material-based touchpad device 40 comprises four main components, including an upper panel 54, four unimorph support members 44, four unimorph piezoelectric (preferably PZT) sensors 46 and a structural support base 42. The supporting base 42 also includes two parts, which are the unimorph support members or pillars 44 and the square shielding 42A around the pillars. The square shielding 42A is included to prevent the pillars 44 from shifting sideways. The supporting base 42 ensures that the pillars 44 do not move sideways when a force is applied from above. This can ensure the force is applied directly to the base 42 in a downward direction. When sideway shifting occurs, the force would resolute into two different directions and decrease the accuracy of theposition determination. Along the shielding wall 43, there is a cut-out 45 for a wire connection. As shown in FIGS. 5 and 5A, a small gap 47 is preferably disposed between each pillar 44 and its respective unimorph piezoelectric sensor 46. This way, the pillar 44 does not provide additional support to its respective unimorph piezoelectric sensor 46 thereby avoiding damage to the sensor 46 when a force is applied. For a preferred embodiment where upper panel 54 is about 5 inches square and is about 0.08 inches to 1 inch thick, and the sensors 46 and / or upper panel 54 is / are built with aluminum, the gap 47 is preferably about 2 mm wide.

[0048] FIG. 7 illustrates the preferred structure of each unimorph sensor 46. Each unimorph sensor 46 preferably comprise two major parts, a metal plate 56 on top and piezoelectric ceramic material 58, preferably PZT, on the bottom. These two components are connected via an Epoxy binder. The dimension of the metal plate 56 should be slightly larger than the ceramics element 58. Prior to final assembly of unimorph sensor 46, the piezoelectric ceramic material 58 has silver electrodes attached on both sides to collect voltage information.

[0049] In this second preferred embodiment of a piezoelectric material- based touchpad device 40, PZT is chosen to be the piezoelectric ceramic material 58, and aluminum is chosen to be the metal plate 56. The dimensions of PZT film 58 are preferably 11mm x 25mm, and the dimensions of the metal plate 56 are preferably 11mm x 25.6mm. The plate 56 is a longer in length to protect the PZT films 58 when they deform. This aspect ratio is smaller compared to the common unimorph structure, but it should provide better longevity. Each corner 57 of upper panel 54, preferably aluminum, is supported by and / or is connected to a point 59 of one of the unimorph sensors 46 as shown in FIG. 8. In this second preferred embodiment of a piezoelectric material-based touchpad device 40, there are four points supporting the aluminum panel 54. But the present disclosure also contemplates expanding each such point to a relatively small surface for stable support. But the surface area should be sufficiently small, so it won't affect the loading force. This design has high sensitivity among PZT's configuration. The metal plate 56 will bend under small pressure and deform PZT material 58 withit. But it is very difficult to manufacture. Due to the brittleness PZT, its longevity is shorter compared to the other preferred embodiments of piezoelectric material- based touchpad devices of the present disclosure. Furthermore, the working condition this second preferred embodiment of a piezoelectric material-based touchpad device 40 is subject to vibrations that cannot be ignored, which makes it mathematically more complex to calculate the touching position. FIGS. 9 - 11 show a third preferred embodiment of a piezoelectric material-based touchpad device 60 that employs a side compression mode, which uses transverse shear mode (d35) of piezoelectric ceramics. This mode utilizes stress applied in the y- direction. FIG. 9 shows the assembled structure 60 comprising a base structure 62 made preferably from PLA plastic, a plurality of vertically oriented support members 64 secured to an outside surface of the base structure 62 wherein each of the support members 64 has a pointed side edge 66; a plurality of sensors 68 wherein each of the plurality of sensors 68 is disposed between a different one of the plurality of support members 64 and a side 63 of the base structure 62. Preferably, each of the plurality of sensors 68 comprises a piezoelectric material 70, preferably PZT, and one or more voltage collection electrodes attached to each sensor (not shown). An upper panel 74, preferably aluminum, of touchpad device 60 is preferably supported by the pointed side edge 66 of each of the plurality of vertically oriented support members 64.

[0050] As shown in FIG. 9, aluminum upper panel 74 extends beyond base structure 62 on two of its sides and is about 0.08 inches to 1 inch thick. The four corners 75 of the aluminum upper panel 74 are preferably connected to the pointed side edges 66 of vertically oriented support members 64. Preferably, the loading condition for touchpad device 60 is the same as compression mode. Preferably, the inside surfaces of support members 64 are attached to the outside and the top surfaces of the PZT films 70 of sensors 68 which are in turn attached to the supporting structure 62. Preferably, a gap 78 is disposed between each of the bottoms of each of the plurality of PZT films 70 and the base structure 62. This way, all force is exerted on the PZT films 70 of sensor 68. Each layer should beconnected via epoxy. The side view of one PZT sensor 68 is shown in FIG. 11. While the design of this third preferred embodiment of a piezoelectric material- based touchpad device 60 may be costly to produce, it does have the advantage of saving internal space.

[0051] The present disclosure is directed to the preferred embodiments described above for piezoelectric material-based touchpad devices as a human input system. After analysis of piezoelectric ceramics' theoretical performance under pressure, three designs were introduced: transverse mode, longitudinal mode, and transverse shear mode. These designs are capable of detecting the position and pressure of human touch. Among the three designs, the transverse mode has been assembled and tested. Compared to conventional capacitive and resistive touchpads, the piezoelectric touchpad uses four PZT films in different orientations for pressure. The prototype assembled shows it can work very well and achieve all its functionality, with an average error rate of 6.26% for position detection. Considering the PZT films' size standard deviation is 5.24%, this accuracy is acceptable.

[0052] With their unique characteristics, Piezoelectric touchpads of the present disclosure would be a better replacement for traditional touchpads or complementary touch sensors. With an analog-to-digital converter, touchpads provide more sensing points than capacitive touchpads. Since the voltage output is triggered by force, a touchpad can detect the force of any object touching it and provide rudimentary data regarding its form. Without etching, the sensor would be much cheaper than a traditional pressure sensor. Since the piezoelectric sensor does not rely on local deformation, it can use a material that has high tensile strength, which resistive touchpads cannot. This would greatly improve the utility of touchscreens today. Overall, it is proven that there is an excellent prospect for the piezoelectric material-based touchpad to function as a precision touchpad with low energy consumption.

[0053] Additional preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure include accuracy and force measureimprovement. Several weak points for detection can be further strengthened, such as improving the algorithm and the manufacturing process. The accuracy rate for both position and force is good, but not close to its limit. There are several ways to change the algorithm to improve the accuracy rate. The first aspect to consider is the PZT films' resistance characteristics under different frequencies. The resistance at lower frequencies is significantly different than at higher frequencies. A better algorithm could be developed if this aspect is considered. Furthermore, the sensor tends to vibrate when a force acts on it. This vibration will interfere with the electric outputs of a PZT touchpad. Rather than the bumper pads currently used, a touchpad using a better damper system preferably could improve the performance of the calculation. The PZT films used in preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure may be cut manually, but more preferably are cut on CNC machines to improve their performance. Lastly, the force loading condition is simplified in the preferred embodiments of piezoelectric material-based touchpad devices presented herein. A more complicated force loading condition with a summation of moments preferably could be implemented in the algorithm to improve the position accuracy further.

[0054] Multi-touch Function - While the preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure are only capable of doing signal point detection because they each only use four sensors, one on each corner. Preferably, additional sensors could be used to achieve multipoint detection. Preferably, a sensor array on the sides of each touchpad of the present disclosure can be set up for multitouch functions.

[0055] High Pressure Situation - As described above, the preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure incorporate PZT films. While such PZT films can stand touching by human hand, they may break under a high-pressure situation. Round piezoelectric films preferably could be used for compression mode for the high- pressure situation. A round film is preferred in a high-stress environment becauseit does not concentrate stress on the corner and therefore becomes much more stress tolerant. This is further demonstrated in the Ansys simulation shown below.

[0056] FIG. 12 shows the two types of PZT used in the simulation, square 80 and round 82. The dimension of the square PZT sensor 80 is 20mm x 2 mm, and the diameter of the round PZT sensor 82 is 20mm. The simulation is demonstrated with force applied to the top surface, and a bottom surface is used as fixed support.Table 7.1. Simulation Results

[0057] The Ansys simulation results show that while the area of the square sensor 80 is 27% larger than the round one 82, it still experiences slightly higher pressure when force is applied.

[0058] The preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure may also preferably include multifunctionality when paired with one or more additional forms of touch technology. For example, the piezoelectric material-based touchpad devices of the present disclosure preferably could be combined with a capacitive or resistive touchscreen to provide additional force and position information. The panel of the touchpad could also be changed to a transparent material.

[0059] Preferred Circuit Information for piezoelectric material-based touchpad devices of the present disclosure include Analog to Digital Converters. An Analog to Digital Converter (ADC) is a device that can convert analog signals to digital signals. As the input in piezoelectric material-based touchpad devices of the present disclosure is generated by piezoelectric material, the inputs are allanalog. The ADC, to process this signal, needs to focus on its voltage rather than current. Among many configurations of ADC, as long as the signal can be sampled, there is no preference for any specific ADC for use with the preferred embodiments of the piezoelectric material-based touchpad devices of the present disclosure.

[0060] Kalman Filter - As stated before, the piezoelectric material, especially small PZTs, are very sensitive. Which means they are vulnerable to electrical interference. This is a serious problem as it will create errors with position determination. This form of interference happens every second during the usage of the preferred embodiments of the piezoelectric material-based touchpad devices of the present disclosure. Because every such touchpad device is subject to interference on a different level, it presents a challenge to eliminate the effect of noise. Algorithmic-wise, it is possible to use only three sensors' data for point determination. The problem of how to integrate four sensors for better point determination also becomes a dilemma. A Kalman filter is preferably used to solve the above problems in the preferred embodiments of the piezoelectric material- based touchpad devices of the present disclosure. A Kalman filter is a mathematical algorithm introduced by Kalman Rudolf Emil, a very famous American mathematician and engineer. His theory is widely used in everyday uses, such as GPS for point determination. It is natural to assume the data with variance collected by each sensor follows under natural distribution. Different sensors are located in different locations and are subject to different interference levels. Therefore, a Kalman Filter can be applied.

[0061] FIG. 13 shows an example of 4 different normal distributions with different levels of noise: 84 where μ=0, σ2=0.2; 86 where μ=0, σ2=1.0; 88 where μ= 0, σ2=5.0; and 89 where μ= -2, σ2=0.5.

[0062] A typical Kalman filter equation is shown:

[0063] The above equation can be expressed as following equations for the use case of the present disclosure.

[0064] Where z, z1;z2are values, and a is standard deviation. The variance of the final value is smaller than both variances of the original data, which means the data is more accurate. In practice, to determine noise level, a series of mathematical algorithm should be performed automatically to determine the noise level and remove unusable data. (Unusable data comes from the non-linear region of PZT electric output.)

[0065] 3D Printing Introduction - 3D printing is another name for additive manufacturing, which is a digital manufacturing process of adding material layer by layer. It is a process to "take the information from a computer-aided design (CAD) file that is later converted to a stereolithography (STL) file." After the file is processed, it can use machines to additively build the designed structure. Presently the three most common polymer-based 3D printing processes are fused deposition modeling (FDM), selective laser sintering (SLS), and stereolithography (SLA). This form of manufacturing has the advantages of low cost, reduced construction waste, and the ability to manufacture complicated parts. It provides a low-cost option for rapid prototype manufacture.

[0066] The preferred 3D printer process of the present disclosure is FDM. It uses a thin plastic filament for the printer's printhead. It melts and extrudes the filament as the slicing file. FIG. 14 shows a preferred print head 90 employing the FDM process comprising a base 91, a support material nozzle 92 for dispensing support material 93, and a build material nozzle 94 for dispensing build material 95. The material used during the process most commonly are polycarbonate (PC), acrylonitrile butadiene styrene (ABS), polyphenylsulfone (PPSF), a mixture of PC-ABS and PC-ISO. While having many advantages, the preferred FDM process is not the only manufacturing process that can be used to make piezoelectric material-based touchpad devices of the present disclosure.

[0067] Fast Fourier Transform - One of the most common analytical math operations used daily is the Fourier transform. However, direct computation of discrete Fourier transform requires heavy computational calculation. Until the Fast Fourier Transform (FFT) algorithm is introduced, where it significantly reduces the required processing. Since then, it has been widely used in various applications like telecommunications, radar, and seismic processing. Mathematically, FFT is a faster algorithm for computing the DFT by reducing the number of computations needed. For instance, it can take 2 or 4 points DFT and generalize them to 8 / 16 / point.

[0068] The Force Loading on a Rectangular Plane Algorithm described below is a preferred algorithm used in the preferred embodiments of piezoelectric material-based touchpad devices of the present disclosure.

[0069] FIG. 15 shows the force on a plane 100 having width (W) and length (L) where the force is applied at the point 101 downward. Because they are only supported at four corners, it distributed to Fl, F2, F3, and F4. From equation 2-40, the following equation can be derived.

[0070] Since angle A and angle C share one side, the following relationship can be derived.

[0071] The force ratio equation can be derived.

[0072] The same principle could apply to Y axis.

[0073] Since the width (X) and length (Y) of the plane is known, the position of touchpoint projected on both diagonal axes can be derived.

[0074] Convert it to X and Y axis, the following equation can be derived.

[0075] In the foregoing Detailed Description, various features are grouped together in a single embodiment to streamline the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the disclosure require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.

Claims

What is claimed is:

1. A piezoelectric material-based touchpad, comprising: a base structure; a plurality of support members secured in the base structure; a plurality of sensors; wherein each of the plurality of sensors is disposed on a different one of the plurality of support members, wherein each of the plurality of sensors comprises a piezoelectric material; an upper panel supported by the plurality of sensors; and a plurality of electrical insulation members; wherein each of the plurality of electrical insulation members is disposed on a different one of the plurality of sensors to insulate said sensor from the upper panel.

2. The piezoelectric material-based touchpad of claim 1, wherein the piezoelectric material comprises lead zirconium titanate (PZT).

3. The piezoelectric material-based touchpad of claim 1, wherein the base structure defines a rectangle and wherein each of the support members is disposed at a corner of the rectangle.

4. The piezoelectric material-based touchpad of claim 1, wherein the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.

5. The piezoelectric material-based touchpad of claim 1, wherein each of the plurality of sensors is part of a sensor structure comprising a layer of PZT material disposed between first and second layers of an electrically conductive material, wherein one or both of the first and second layers of a conductive material is connected to one or more wires for signal collection from the piezoelectric sensor.

6. The piezoelectric material-based touchpad of claim 1, further comprising a plurality of vibration dampening pads, wherein each one of the plurality ofvibration dampening pads is disposed under a respective one of the plurality of support members.

7. A piezoelectric material-based touchpad, comprising: a base structure; a plurality of unimorph support members secured in the base structure; a plurality of unimorph sensors; wherein each of the plurality of unimorph sensors is disposed on a different one of the plurality of unimorph support members, wherein each of the plurality of unimorph sensors comprises a piezoelectric material bonded to a metal plate and one or more voltage collection electrodes attached to each unimorph sensor; and an upper panel supported by the plurality of unimorph sensors.

8. The piezoelectric material-based touchpad of claim 7, wherein the piezoelectric material comprises lead zirconium titanate (PZT).

9. The piezoelectric material-based touchpad of claim 7, wherein the metal plate comprises aluminum.

10. The piezoelectric material-based touchpad of claim 7, wherein the metal plate defines a first area and the piezoelectric material defines a second area and wherein the first area is larger than the second area.

11. The piezoelectric material-based touchpad of claim 7, wherein a small gap about 0.05 inches wide is disposed between each unimorph sensor and each unimorph support structure.

12. The piezoelectric material-based touchpad of claim 7, wherein the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.

13. A piezoelectric material-based touchpad, comprising: a base structure;a plurality of vertically oriented support members secured to an outside surface of the base structure; wherein each of the support members has a pointed side edge; a plurality of sensors; wherein each of the plurality of sensors is disposed between a different one of the plurality of support members and a side of the base structure, wherein each of the plurality of sensors comprises a piezoelectric material and one or more voltage collection electrodes attached to each sensor; and an upper panel supported by the pointed side edge of each of the plurality of vertically oriented support members.

14. The piezoelectric material-based touchpad of claim 13, wherein the piezoelectric material comprises lead zirconium titanate (PZT).

15. The piezoelectric material-based touchpad of claim 13, wherein a gap is disposed between each of the plurality of sensors and the base structure.

16. The piezoelectric material-based touchpad of claim 13, wherein the upper panel comprises one or more of aluminum, steel, glass and titanium and wherein the upper panel is about 0.08 inches to 1 inch thick.

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