A tactile perception method and device based on fingerprint-like structure and piezoelectric sensing

Abstract

The present invention discloses a tactile perception method and device based on a fingerprint-like structure and piezoelectric sensing. The method utilizes a piezoelectric tactile finger to identify the position and direction angle of different sliding contacts. The method includes the following steps: setting a parameter group; obtaining each area divided by each channel; collecting raw data from each channel after starting the sliding experiment to obtain sliding data for each channel; calculating the time point when each channel first generates a signal, and displaying the relationship between contact occurrences in each channel area according to the order of the time points, thereby obtaining the position of the sliding contact and the direction angle of the sliding direction. The piezoelectric tactile finger includes a sensor array using a fingerprint-like curve structure. The sensor array is composed of piezoelectric thin films arranged in a multi-layer circular segmented curve layout and a vertical protrusion layout. The present invention utilizes the fingerprint-like curve structure to achieve tactile perception with omnidirectional sensitivity, enabling omnidirectional angle recognition and sensing of different positions.

Description

Technical Field

[0001] The present invention relates to the field of tactile sensing technology, and in particular to a tactile sensing method and device based on a fingerprint-like structure and piezoelectric sensing. Background Art

[0002] Tactile sensing is a key technology in the current development of robotics, and tactile sensing in robotic hands plays a crucial role in robotic grasping and human-machine interaction. The human hand is one of the most sensitive parts of the human body, and the fingertips, as the most frequently used part of the hand, are a prime candidate for robotic biomimetic design. Numerous previous studies have demonstrated that the fingerprint structure of the fingertips is a key factor in improving tactile sensitivity. Fingerprint structure primarily consists of the papillary ridges and curled structures on the surface of the fingertip skin. Therefore, designing robotic fingers that mimic the fingertip structure can significantly enhance the tactile sensitivity of robotic hands.

[0003] Currently, there are many principles of tactile sensing, including piezoresistive, piezoelectric, optical, and magnetic. Among them, piezoelectric only responds to dynamic signals and has a fast response speed. This characteristic of piezoelectric sensors is very suitable for dynamic interaction between robot hands and touched objects. The current structural layout of piezoelectric sensors is often laid out in a thin film matrix on the surface of the robot finger. This layout has the following disadvantages:

[0004] 1) Spatial resolution is limited by the length and width of the thin film unit, which places high demands on the process;

[0005] 2) The tiling method determines that the sensor is more sensitive to normal pressure and insensitive to tactile stimulation of tangential sliding;

[0006] 3) The linear matrix layout means that the sensor does not have the same sensitivity in all directions, but only has a high sensitivity in the direction perpendicular to the linear film unit.

[0007] Therefore, how to design a new structural layout is an urgent problem to be solved for piezoelectric sensors on robot fingers, so as to achieve the functions of high-resolution position perception under normal pressure and omnidirectional angle perception under tangential sliding.

[0008] Therefore, those skilled in the art are committed to developing a tactile perception method and device based on a fingerprint-like structure and piezoelectric sensing to overcome the problems existing in the prior art. Summary of the Invention

[0009] In view of the above-mentioned defects of the prior art, the technical problems to be solved by the present invention are: the fingerprint-like structure layout currently used is often used to amplify the contact signal, and does not take into account the use of the fingerprint curve layout in the direction of omnidirectional sensing sensitivity; the current sensing layout method that refers to the fingerprint curve layout often uses the entire layout as a sensing unit, and there is no segmented design for sensing, resulting in a unit of the fingerprint curve layout being unable to achieve recognition of multiple directions and angles; and the current layout of the piezoelectric film is often flat, which is insensitive to tangential slip, and the spatial resolution of position sensing is limited by the length and width of the film, which has high process requirements.

[0010] To achieve the above objectives, the present invention provides a tactile perception method based on a fingerprint-like structure and piezoelectric sensing, which uses a piezoelectric tactile finger to identify the position and direction angle of different sliding contacts. The method includes the following steps:

[0011] Step 1: Set the parameter group;

[0012] Step 2: Obtain each area divided by each channel;

[0013] Step 3: After starting the slip experiment, collect the raw data of each channel to obtain the slip data of each channel;

[0014] Step 4: Calculate the time point when each channel first generates a signal, and display the relationship between the contact of each channel area according to the order of the time points, thereby obtaining the position of the sliding contact and the direction angle of the sliding direction;

[0015] The piezoelectric tactile finger includes a sensor array with a fingerprint-like curve structure. The sensor array is composed of a piezoelectric film in a multi-layer circular segmented curve layout and a vertical protrusion layout.

[0016] Furthermore, the piezoelectric film is concentrically arranged in multiple layers from the inside to the outside, and each layer is evenly arranged at equal intervals around the circumference.

[0017] Furthermore, the piezoelectric films in different layers are arranged in a staggered manner.

[0018] Furthermore, the parameter group in step 1 includes the total number of layers m, the number of evenly distributed arcs per layer N={n1,n2,...,n m}、The angle difference between the circumferences of each layer is α i- 、The initial deflection angle of each layer A0={α 10 ,α 20 ,...,α m0}、The radius of each circle is R={r1,r2,...,r m}.

[0019] Furthermore, the formula for each region divided by each channel in step 2 is expressed as Γ ij ={r i ,θ ij}, where each channel occupies an angle range θ ij =[α i0 +α i+ ×(j-1)+α i- ×(j-1),α i0 +α i+ ×j+α i- ×(j-1)], the angular range occupied by each channel Where i represents the i-th layer of circumference, j represents the j-th arc of each layer of circumference; the coordinates of the center position of the area are: γ ij =(r i ,α ij ), where the center position angle After starting the slip experiment, collect the original data of each channel to obtain the slip data of each channel Among them, i represents the i-th layer of circumference, and j represents the j-th arc of each layer of circumference.

[0020] Furthermore, the slip data formula of each channel in step 3 is expressed as Among them, i represents the i-th layer of circumference, and j represents the j-th arc of each layer of circumference.

[0021] Furthermore, the step 4 specifically includes the following steps:

[0022] Step 4.1, get d ij (t) The time when the signal is first generated ij0 ;

[0023] Step 4.2: Get the time when D(t) first generates a signal T0 = {t ij0};

[0024] Step 4.3: Display the region intersection in the order of T0.

[0025] The present invention also provides a tactile perception device based on a fingerprint-like structure and piezoelectric sensing, including a piezoelectric tactile finger, the piezoelectric tactile finger including a tactile finger base, a sensor array and a signal acquisition circuit, the tactile finger base is a 3D-printed finger-like shape, and a groove is opened at the fingertip to fix the sensor array, the sensor array includes a piezoelectric film and cylindrical silicone, the piezoelectric film is inserted into the cylindrical silicone, wherein the arrangement of the piezoelectric film is based on a fingerprint-like curve structure, according to a multi-layer circular segmented curve layout and a vertical protrusion layout, the signal acquisition circuit includes a multi-channel circuit board, and is connected and fixed to the tactile finger base, and the piezoelectric film is connected to each channel of the circuit board through a wire.

[0026] Furthermore, the piezoelectric film is concentrically arranged in multiple layers from the inside to the outside, and each layer is evenly arranged at equal intervals around the circumference.

[0027] Furthermore, the piezoelectric films in different layers are arranged in a staggered manner.

[0028] The beneficial effects of the present invention are:

[0029] 1. This invention utilizes a fingerprint-like curved structure to achieve omnidirectional tactile perception. The piezoelectric film is designed as a curved layout, with normal vectors in different directions at different locations. Applying a load in the direction of the normal vector maximizes sensitivity. Thus, a single piezoelectric unit achieves tangential omnidirectional angular sensitivity.

[0030] 2. Based on the segmented fingerprint arrangement, the present invention employs a segmented curve layout of the piezoelectric film to identify the direction and angle of tactile stimulation. Arranging multiple piezoelectric units in a segmented curve pattern can form multiple sensing sources. Thus, using multiple curved piezoelectric sensing sources, different direction angles can be decoded, achieving omnidirectional angle recognition.

[0031] 3. Based on the arrangement of fingerprint nipple ridges, the present invention arranges the piezoelectric film in a vertical pattern, enhancing the sensitivity of tangential slip detection. Simultaneously, it can improve the spatial resolution during normal pressure, allowing detection of different locations. By simulating the structure of fingerprint nipple ridges, the piezoelectric film is arranged in a vertical pattern of micro-protrusions. This improves the sensitivity of tangential slip detection, while also improving the spatial resolution during normal pressure, allowing detection of different locations.

[0032] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A preferred embodiment of the present invention is a curve layout method inspired by the curled structure of a fingerprint on a human fingertip;

[0034] Figure 2 A tactile finger with a fingerprint-like structural layout is a preferred embodiment of the present invention;

[0035] Figure 3 The sensitivity of the arc layout and the straight line layout to tactile stimulation at different direction angles in a preferred embodiment of the present invention;

[0036] Figure 4 This is a direction perception experiment and source data based on single-row cylinder tactile stimulation in a preferred embodiment of the present invention;

[0037] Figure 5 This is a fingerprint-like tactile finger direction and position perception process of a preferred embodiment of the present invention.

[0038] Among them, 1- piezoelectric film, 2- cylindrical silicone, 3- long screw, 4- tactile finger base, 5- circuit board, 6- limiting stud, 7- nut, 8- piezoelectric tactile finger. DETAILED DESCRIPTION

[0039] The following describes preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0040] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0041] To address the deficiencies in the existing technology, this application innovatively proposes a piezoelectric tactile device based on a fingerprint-like structure layout. The advantages of the fingerprint-like structure mainly include omnidirectional tactile perception, recognition of stimuli at different angles, and high sensitivity to tangential slip. In order to achieve high tactile sensitivity, this application adopts a bionic design approach. Inspired by the fingerprint structure layout of the fingertip, according to the fingerprint curling structure and the nipple-shaped ridge structure, a circular segmented curve layout and a vertical protrusion layout are obtained, such as Figure 1 shown.

[0042] The piezoelectric tactile finger 8, with a fingerprint-like structure, consists of three modules: a tactile finger base 4, a sensor array, and a signal acquisition circuit. The tactile finger base 4 is 3D-printed to mimic a finger, with a groove at the fingertip to secure the sensor array and two through-holes at the bottom for securement. The sensor array is composed of a piezoelectric film 1 and a cylindrical silicone rubber 2. The piezoelectric film 1 is inserted into the cylindrical silicone 2 and solidified within the mold. The piezoelectric film 1 is arranged in a fingerprint-like curled structure, consisting of four circles, with 6, 4, 4, and 2 films per circle, respectively, from the outside to the inside. The piezoelectric film 1 is arranged to achieve a certain curvature to achieve omnidirectional tactile perception. Furthermore, the piezoelectric film 1 is arranged in a segmented, curved pattern, based on the segmented fingerprint layout, to identify the direction and angle of tactile stimulation. Furthermore, the piezoelectric film 1 is arranged in a vertical, raised pattern. The signal acquisition circuit consists of two 8-channel circuit boards 5, which are connected and fixed to the tactile finger base 4 through long screws 3, limit studs 6, and nuts 7. Signal acquisition can be achieved by connecting the wires on both sides of the piezoelectric film 1 to each channel of the circuit board 5. The relative relationship between the three modules is as follows: Figure 2 shown.

[0043] At present, the layout of piezoelectric films is often flat, which is relatively insensitive to tangential slip, and the spatial resolution of position sensing is limited by the length and width of the film. Compared with the traditional flat layout, the advantage of a vertical layout of piezoelectric film is that it is more likely to deform under external force, so it has higher sensitivity. When laid flat, the film is not sensitive enough to tangential forces. Placing the film vertically can make it more sensitive to tangential slip. Designing the piezoelectric film into a circular layout takes advantage of the fact that the normal vectors of the fingerprint-like curve structure are different at different angles, and applying a load in the direction of the normal vector can achieve maximum sensitivity. This ensures high sensitivity in all directions. Figure 3 The figure shows the signal strength of piezoelectric films of equal length in response to forces in different directions when arranged in a vertical straight layout and a vertical curved layout. It can be seen that the vertical curved layout has a larger signal response to stimuli in different directions, indicating that it has omnidirectional sensitivity. The vertical straight layout is most sensitive to stimuli in the normal direction, with signals in other directions gradually weakening.

[0044] The angle recognition of the sensor array composed of piezoelectric films is based on a multi-layer segmented design. The piezoelectric films are evenly spaced at equal intervals around the circumference. According to the collected signal strength, after data processing, it can distinguish between slips in different directions. The sensor array consists of 4 layers, and different layers of piezoelectric films are staggered to ensure overall omnidirectional sensitivity. In this embodiment, we use a row of cylindrical protrusions to stimulate the tactile sensation and perform tangential sliding on the piezoelectric tactile finger at different positions and different direction angles, such as Figure 4(a) As shown. The contact position is controlled by the moving directions X and Y, and the direction angle is controlled by β. The piezoelectric film with 16 channels arranged in a circular segment at the fingertip is as follows. Figure 4 (b) As shown. From the inside to the outside, they are the 1st, 2nd, 3rd, and 4th layers. Each section of the film is numbered starting from the positive direction of the X axis. For example, for the 2nd layer, the numbers are 2-1, 2-2, 2-3, and 2-4. Figure 4 (b) In the sliding direction of the above figure, 16 channels of raw piezoelectric signals are obtained, which vary in signal intensity and the time when the signal first occurs.

[0045] The piezoelectric tactile finger is used to identify the position and direction angle of different sliding contacts, such as Figure 5 At the beginning, the parameter group needs to be set, including the total number of layers m, the number of arcs uniformly distributed on each layer N = {n1, n2, ..., n m}、The angle difference between the circumferences of each layer is α i- 、The initial deflection angle of each layer A0={α 10 ,α 20 ,…,α m0}、The radius of each circle is R={r1,r2,…,r m Then, each channel is divided into regions according to the parameter group. Get each region divided by each channel: Γ ij ={r i ,θ ij}, where each channel occupies an angle range θ ij =[α i0 +α i+ ×(j-1)+α i- ×(j-1),α i0 +α i+ ×j+α i- ×(j-1)], the angular range occupied by each channel The center coordinates of the region are: γ ij =(r i ,α ij ), where the center position angle After starting the slip experiment, collect the original data of each channel to obtain the slip data of each channel Where i represents the i-th layer of circumference, and j represents the j-th arc of each layer of circumference. Calculate the time point when each channel first generates a signal, and display the relationship between the contact of each channel area according to the order of the time points: Get d ij (t) The time when the signal is first generated ij0 ; Get the time when D(t) first generates a signal T0={t ij0}; Display the region intersection in the order of T0. From this, the position of the sliding contact and the direction angle of the sliding direction are obtained.

[0046] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A tactile perception method based on fingerprint-like structure and piezoelectric sensing, characterized in that: A piezoelectric tactile finger is used to identify the position and direction angle of different sliding contacts. The piezoelectric tactile finger includes a sensor array with a fingerprint-like curve structure. The sensor array is composed of a piezoelectric film arranged in a multi-layer circular segmented curve layout and a vertical protrusion layout. The method includes the following steps: Step 1: Set the parameter group; The parameter group in step 1 includes the total number of layers , Number of evenly distributed arcs per layer , the angle difference between the circles in each layer , initial deflection angle of each layer , the radius corresponding to each layer of the circle ; Step 2: Connect the piezoelectric film to each channel of the circuit board through a wire to obtain each area divided by each channel of the circuit board; The formula for each area divided by each channel in step 2 is expressed as , where each channel occupies the angle range , the angle range occupied by each channel in, Indicates the Layer circumference, Indicates the circumference of each layer arc; the coordinates of the center of the area are: , where the center position angle ; Step 3: After starting the slip experiment, collect the raw data of each channel to obtain the slip data of each channel; Step 4: Calculate the time point when each channel generates a signal for the first time, and display the contact relationship between each channel area according to the order of the time points, thereby obtaining the position of the sliding contact and the direction angle of the sliding direction.

2. The tactile perception method based on fingerprint-like structure and piezoelectric sensing according to claim 1, characterized in that: The piezoelectric films are arranged concentrically in multiple layers from the inside to the outside, and each layer is evenly arranged at equal intervals around the circumference.

3. The tactile perception method based on fingerprint-like structure and piezoelectric sensing according to claim 2, characterized in that: The piezoelectric films in different layers are arranged in a staggered manner.

4. The tactile perception method based on fingerprint-like structure and piezoelectric sensing according to claim 3, characterized in that: The slip data formula of each channel in step 3 is expressed as ,in, Indicates the Layer circumference, Indicates the circumference of each layer An arc.

5. The tactile perception method based on fingerprint-like structure and piezoelectric sensing according to claim 4, characterized in that: The step 4 specifically includes the following steps: Step 4.1, obtain Time when the signal was first generated ; Step 4.2, obtain Time when the signal was first generated ; Step 4.3, follow The order of before and after shows the intersection of areas.

6. A tactile sensing device based on a fingerprint-like structure and piezoelectric sensing, characterized in that: It includes a piezoelectric tactile finger, which includes a tactile finger base, a sensor array and a signal acquisition circuit. The tactile finger base is a 3D-printed finger-like shape, with a groove at the fingertip to fix the sensor array. The sensor array includes a piezoelectric film and cylindrical silicone. The piezoelectric film is inserted into the cylindrical silicone. The arrangement of the piezoelectric film is based on a fingerprint-like curve structure, according to a multi-layer circular segmented curve layout and a vertical protrusion layout. The signal acquisition circuit includes a multi-channel circuit board and is connected and fixed to the tactile finger base. The piezoelectric film is connected to each channel of the circuit board through a wire.

7. The tactile sensing device based on a fingerprint-like structure and piezoelectric sensing as claimed in claim 6, characterized in that: The piezoelectric films are arranged concentrically in multiple layers from the inside to the outside, and each layer is evenly arranged at equal intervals around the circumference.

8. The tactile sensing device based on a fingerprint-like structure and piezoelectric sensing as claimed in claim 7, characterized in that: The piezoelectric films in different layers are arranged in a staggered manner.

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