CN115593137A

CN115593137A - Method for manufacturing handwriting identification piezoelectric pen based on three-dimensional force detection

Info

Publication number: CN115593137A
Application number: CN202211376028.6A
Authority: CN
Inventors: 朱睿健; 黄予; 陈馨颖; 张茂茹; 徐诺言; 王增梅
Original assignee: Nanjing Institute of Technology
Current assignee: Nanjing Institute of Technology
Priority date: 2022-11-04
Filing date: 2022-11-04
Publication date: 2023-01-13

Abstract

The invention provides a method for manufacturing a handwriting authentication piezoelectric pen based on three-dimensional force detection. Placing a piece of piezoelectric ceramic on a refill in the Z direction, placing two pieces of piezoelectric ceramic with opposite polarization directions on one end close to a refill in the X and Y directions, connecting leads oppositely, and filling resin at the top end of a ball pen for curing to fix the piezoelectric ceramic to prepare the piezoelectric pen; when writing, the wires in three directions are respectively connected with an ultra-large resistor in parallel, the change curve of the open-circuit voltage of the three piezoelectric ceramics along with time in the writing process is measured, and the change curve is converted into the characteristic of a force-time curve in the XYZ direction so as to identify the handwriting. The method can inhibit temperature fluctuation and integral vibration of the piezoelectric pen, and interference signals of pyroelectric, piezoelectric and measuring circuits caused by signal drift; the real open-circuit voltage is obtained by deducting the base line, and the three-dimensional force-time curve is obtained by integration, so that the extraction of force signals in the writing process is greatly enhanced, and the handwriting identification capability is high in accuracy.

Description

Method for manufacturing handwriting identification piezoelectric pen based on three-dimensional force detection

Technical Field

The invention belongs to the field of combination of B43K 29/00 writing instruments and other articles, and particularly relates to a piezoelectric pen preparation method based on three-dimensional force detection in a writing process of piezoelectric ceramics and a three-dimensional force signal analysis method in the writing process.

Background

The handwriting identification is a technology for identifying and recognizing the handwriting formed by writing activities, and plays an important role in identifying the authenticity of the document and detecting and judging the case. Most of the existing handwriting identification technologies are shooting identification by the size of handwriting, the layout interval of characters, the inclination, the continuity and the like, but a relatively large number of samples are generally needed to achieve a relatively high accuracy, and the handwriting which is subjected to targeted copying can hardly be identified in true or false, so that a technology which can not be counterfeited, is convenient and simple is urgently needed.

The shape of the handwriting is easy to imitate, but the force, the speed, the stroke order and the difficulty in restoration in the writing process are overcome, so that the method for identifying the handwriting by detecting the force change in the writing process while writing is an accurate handwriting identification method. At present, an inductance-based identification pen is provided, and an oscillating circuit and a planar sensor are arranged at the top end of a pen core, so that the distance between metal at the top end of the pen core and an inductor is changed due to pressure change during writing, the resonance frequency is changed, and the force change in the Z-axis direction during writing is detected; [ International Parallel & Distributed Processing symposium. IEEE Computer Society, 2001 ]. In addition, the study is also carried out to implant PZT piezoelectric ceramics in a pen and detect the pressure on the Z axis through the piezoelectric ceramics so as to prepare an identification electroprobe; [ International Conference on Document Analysis & recognition. IEEE Computer Society, 2001: 1045-1049].

Although some progress is made in these methods, it is difficult to detect the force change only in the Z direction, and it is difficult to perform more accurate detection, and it is difficult for the current piezoelectric pen signal processing method to directly respond to the force change; in the writing process, more information is the force characteristics in the XY direction when the pen is moved to incline, and no three-dimensional force detection product and force signal analysis technology exists in the three-dimensional writing process at present; moreover, the writing force signal is weak, and the noise signal is difficult to suppress and eliminate.

Disclosure of Invention

The invention provides a piezoelectric pen preparation and three-dimensional force signal analysis technology in the writing process based on three-dimensional force detection in the writing process of piezoelectric ceramics, and the method does not need complex structures and detection equipment, can eliminate the interference of a plurality of signals and has high accuracy of handwriting identification.

The invention adopts the following technical scheme: the method comprises the following steps of installing piezoelectric ceramics at the top end of a pen core along the vertical direction, the transverse direction and the longitudinal direction, leading out a lead, detecting open-circuit voltage output by the piezoelectric ceramics in the three directions in the writing process, processing open-circuit voltage signals, obtaining a force-time curve in the XYZ direction, and identifying handwriting, wherein the method comprises the following steps of:

step 1, taking five pieces of polarized piezoelectric ceramics, and connecting out a lead by soldering with silver paste and the like along the polarization direction;

step 2, shortening a refill of a common ball-point pen, sticking a piece of piezoelectric ceramic right above the top end of the refill, wherein the polarization direction is the axial direction of the refill and is used as the Z direction;

step 3, near the end close to the pen point, four small piezoelectric ceramics are pasted around the pen core in the directions of + X, -X, + Y and-Y by glue, the polarization directions are all towards or back to the pen core, so that the polarization directions of the two piezoelectric ceramics in the X direction and the Y direction are opposite, the connection modes of the leads in the X direction and the Y direction are the same, the leads led out from two faces close to one side of the pen core are connected together, the leads led out from two faces far away from the pen core are also connected together, when temperature fluctuation and the whole vibration of the piezoelectric pen are caused, voltage signals generated by the piezoelectric ceramics in the X direction and the Y direction, which are opposite in size and direction, are opposite to each other, and are offset, so that the pyroelectric and piezoelectric interference signals caused by the temperature fluctuation and the whole vibration of the piezoelectric pen can be inhibited by the two oppositely polarized piezoelectric ceramics;

and 3, filling the refill stuck with the piezoelectric ceramics into a ball pen, leading out the lead from an opening at the top end of the ball pen, and filling resin into the top end of the ball pen for curing so as to fix the piezoelectric ceramics.

And 4, writing on paper by using a ball pen, respectively connecting an ultra-large resistor in parallel between two leads connected with the piezoelectric ceramics in the XYZ direction so as to inhibit voltage signal drift, and simultaneously measuring the change curve of the open-circuit voltage output by the three piezoelectric ceramics along with time in the writing process.

Step 5, generating electric charge quantity Q and pressure P, stress area S and piezoelectric constant d after piezoelectric ceramics are stressed ₃₃ The following relationships exist:

（1）

the measured open-circuit voltage V has the following relationship with the resistance R:

（2）

therefore, the measured voltage is proportional to the stress change rate, so that the open-circuit voltage needs to be integrated to obtain the force change during writing, the measured open-circuit voltage has a part of noise signals, a baseline needs to be subtracted to obtain a signal from the force during writing, then integration is carried out to obtain a force-time curve, and the characteristics of the force-time curve in XYZ directions during writing of different people, including the shape of the curve, the time of the force change, the slope of the change, the height of the change and the like, are analyzed to identify handwriting.

Has the advantages that: the invention realizes the detection of three-dimensional force in the writing process through the structural design of the piezoelectric pen for the first time; through the arrangement of oppositely polarized ceramics, pyroelectric and piezoelectric interference signals caused by temperature fluctuation and integral vibration of the piezoelectric pen are inhibited; the voltage signal drift is inhibited by connecting a large resistor in parallel, the real open-circuit voltage is obtained by buckling a base line, and the three-dimensional force-time curve is obtained by integration, so that the extraction of the force signal in the writing process is greatly enhanced, and the handwriting identification capability is highly accurate.

Drawings

FIG. 1 is a schematic diagram of a three-dimensional piezoelectric pen;

FIG. 2 shows force-time curves in the Z direction for different people writing the letter A (a) X, (b) Y, and (c).

Detailed Description

The invention is further explained below with reference to examples and figures. The following examples are provided only for illustrating the present invention and are not intended to limit the scope of the invention.

Example (b):

step 1, taking five polarized piezoelectric ceramics with the size of 3 x 3mm, and connecting a lead out by using silver paste along the polarization direction;

step 2, truncating a refill of a common ball-point pen, sticking a piece of piezoelectric ceramic right above the top end of the refill, taking the polarization direction as the axial direction of the refill and the Z direction, and leading out leads on two axial surfaces;

step 3, adhering four pieces of piezoelectric ceramics in the + X, -X, + Y, -Y directions around the pen core at the end close to the pen tip by glue, leading out leads from two surfaces close to one side of the pen core and connecting the leads together, leading out leads from two surfaces far away from the pen core and connecting the leads together, and leading out two leads in the X and Y directions respectively;

and 3, filling the refill stuck with the piezoelectric ceramics into a ball pen, leading out the lead from the open holes at the top end and the side surface, filling resin at the top end of the ball pen for curing to fix the piezoelectric ceramics, wherein the attached figure 1 is a structural schematic diagram of the three-dimensional piezoelectric pen.

And 4, writing on paper by using a ball-point pen, respectively connecting 1G omega resistors in parallel between two leads connected with the piezoelectric ceramics in the XYZ direction so as to inhibit voltage signal drift, and simultaneously measuring a change curve of open-circuit voltage output by the three piezoelectric ceramics along with time in the writing process.

And 5, deducting the base line of the open-circuit voltage-time curve through origin and other software, integrating to obtain a force-time curve, wherein the shape of the curve, the time of force change, the change slope, the change height and the like are greatly different from each other according to the force-time curve graph obtained when the figure 2 is different from the human writing letters A, and the handwriting characteristics of different people can be accurately identified. And it can be seen that the force signals in the Z direction are small in difference, and conversely, the force signals in the XY direction are large in difference when different people write, which shows that the method for identifying handwriting by using three-dimensional force detection provided by the invention can extract more signals of force in writing, and the accuracy of handwriting identification is greatly improved.

Claims

1. A method for manufacturing a handwriting authentication piezoelectric pen based on three-dimensional force detection is characterized by comprising the following steps:

step 1, taking five pieces of polarized piezoelectric ceramics, and soldering and tapping out a lead wire by silver paste along the polarization direction;

step 2, sticking a piece of piezoelectric ceramic right above the top end of the ball-point pen refill, wherein the polarization direction is the axial direction of the refill and is taken as the Z direction;

step 3, adhering four pieces of piezoelectric ceramics in the + X, -X, + Y, -Y directions around the pen core by glue at the end close to the pen tip, wherein the polarization directions all face or back to the pen core, so that the polarization directions of the two pieces of piezoelectric ceramics in the X direction and the Y direction are opposite, the connecting modes of the leads in the X direction and the Y direction are the same, the leads led out from two faces close to one side of the pen core are connected together, and the leads are led out from two faces far away from the pen core and connected together;

step 4, filling the refill stuck with the piezoelectric ceramics into a ball-point pen, leading out a lead from an opening at the top end of the ball-point pen, and filling resin into the top end of the ball-point pen for curing so as to fix the piezoelectric ceramics;

and 5, writing by using a ball-point pen, respectively connecting an ultra-large resistor in parallel between two leads connected with the piezoelectric ceramics in the XYZ direction, simultaneously measuring the change curve of the open-circuit voltage output by the three piezoelectric ceramics along with time in the writing process, and analyzing the characteristics of the force-time curve in the XYZ direction in writing so as to identify the handwriting.

2. The method for manufacturing the piezoelectric pen for handwriting authentication based on three-dimensional force detection according to claim 1, wherein the method comprises the following steps: in step 5, after the open-circuit voltage is measured in parallel, a signal processing mode is a base line buckling mode, then a force-time curve is obtained through integration, and the shape characteristics of the curve including the shape of the curve, the time of force change, the slope of change, the height of change and the like are extracted to identify handwriting.