CN107422883B - A kind of electronic whiteboard double-pen writing method based on ultrasound - Google Patents

A kind of electronic whiteboard double-pen writing method based on ultrasound Download PDF

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CN107422883B
CN107422883B CN201710678439.3A CN201710678439A CN107422883B CN 107422883 B CN107422883 B CN 107422883B CN 201710678439 A CN201710678439 A CN 201710678439A CN 107422883 B CN107422883 B CN 107422883B
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pen
ultrasonic
working
area
time
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CN107422883A (en
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燕学智
王海云
孙晓颖
陈建
武秋爽
温艳鑫
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Jilin University
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Jilin University
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/033—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor
    • G06F3/0354—Pointing devices displaced or positioned by the user, e.g. mice, trackballs, pens or joysticks; Accessories therefor with detection of 2D relative movements between the device, or an operating part thereof, and a plane or surface, e.g. 2D mice, trackballs, pens or pucks
    • G06F3/03545—Pens or stylus
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/043—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using propagating acoustic waves

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Human Computer Interaction (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Position Input By Displaying (AREA)

Abstract

The present invention provides a kind of electronic whiteboard double-pen writing method based on ultrasound, belongs to ultrasonic pen Writing method.Including two ultrasonic pens, electronic whiteboards, two ultrasonic pens include that can issue the infrared infrared transmitter of phase co-wavelength and can issue the ultrasonic transmitter of identical frequency ultrasonic wave, it can receive the infrared signal of another ultrasonic pen sending, simultaneously to judge whether another ultrasonic pen be in running order；The present invention judges the working condition and the band of position of two pens using time-multiplexed principle, realize that two pens alternately write work, the time reference of pen is bifurcated as area first with the different pulse widths of infrared signal, the infrared signal issued by receiving another one-pen, judge whether it is in working condition, the work-based logic timing of oneself is realized then in conjunction with the band of position instruction that wireless transmission obtains, pen tip start-up operation is pressed, double-pen writing can be applied to interactive electronic teaching, interaction meeting, training etc..

Description

Electronic whiteboard double-pen writing method based on ultrasonic waves
Technical Field
The invention relates to an ultrasonic pen writing method, in particular to an ultrasonic-based electronic whiteboard double-pen writing method taking infrared signals as time bases, which can realize time-sharing writing of two pens on an electronic whiteboard, and thus can be better applied to functions of interactive electronic teaching, interactive conferences, training and the like.
Background
With the rise and development of virtual reality technology, people have more and more experience requirements on human-computer interaction products. The interactive electronic whiteboard is a relatively new product, and is evolved from a common electronic whiteboard, the earliest electronic whiteboard can only perform some simple operations (copy electronic whiteboard) similar to copying, the interactive electronic whiteboard can perform computer communication, the electronic whiteboard is connected with a PC, the contents on the PC can be displayed on the electronic whiteboard, an ultrasonic pen can replace a mouse to operate, and the arbitrary operations of files, including file compiling, annotation and the like, are realized.
The interactive electronic whiteboard appearing in the market at present adopts single-pen writing, and the electronic whiteboard generally adopts two cameras in order to realize the double-pen writing function, realizes double-pen writing from hardware, or adopts the mode that a wave trap circuit and a digital filter are combined through the frequency division multiplexing of infrared signals and ultrasonic signals, and realizes the differentiation of a plurality of targets. There are some descriptions about the function of double-pen writing.
The Chinese patent ' a method for realizing double-pen writing based on an electronic whiteboard ' (application number 201210338872.X) ' provides a method for realizing double-pen writing based on an electronic whiteboard, the states of corresponding handwriting pens are respectively detected by two cameras, an image acquisition module acquires image data of each camera, the image data is stored in an SDRAM chip through an image storage module, meanwhile, light spot coordinates left by the handwriting pens are obtained by calculation through an image processing module, and the coordinates of the light spots are displayed through a PC to realize the double-pen writing. However, this method requires a specific camera to position the stylus, which is costly and greatly influenced by the surrounding environment. The Chinese patent 'multi-target three-dimensional ultrasonic positioning system' (201320612723.8) proposes a multi-target three-dimensional ultrasonic positioning system, which takes infrared signals as a reference, realizes multi-target distinguishing through frequency division multiplexing of the infrared signals and ultrasonic signals, and separates out ultrasonic positioning signals of different targets by adopting a mode of combining a wave trap circuit and a digital filter. However, this method cannot be distinguished in the case where two ultrasonic pens transmit ultrasonic signals with the same waveform and frequency. Chinese patent "the electromagnetic induction display device that a plurality of pens write simultaneously" (201420151401.2) has proposed the electromagnetic induction display device that a plurality of pens write simultaneously, the utility model discloses a receiving coil receives the electromagnetic wave frequency signal back that different electromagnetic pens sent respectively, and electromagnetic signal is behind analog switch, analog frequency-selecting amplifier circuit and AD converting circuit, becomes digital signal with electromagnetic signal conversion, sends for the treater, handles, and behind the writing handwriting of the different electromagnetic pens of calculation method processing among the prior art of treater adoption, will write the orbit signal and pass to the projector through the computer, realizes the purpose that a plurality of pens write. However, this method must be operated using a dedicated electronic pen, and electromagnetic waves have a certain radiation to the human body.
Disclosure of Invention
The invention provides an ultrasonic-based electronic whiteboard double-pen writing method, which judges the working states and position areas of two pens by utilizing the time division multiplexing principle to realize the alternate writing work of the two pens.
The technical scheme adopted by the invention is as follows: the electronic whiteboard comprises two signal receivers and a smooth writing plane, the signal receivers are used for receiving infrared signals and ultrasonic signals which are transmitted by the two ultrasonic pens, the two ultrasonic pens comprise infrared transmitters capable of transmitting infrared with the same wavelength and ultrasonic transmitters capable of transmitting ultrasonic waves with the same frequency, and can receive infrared signals transmitted by the other ultrasonic pen and position information acquired by wireless transmission, the two ultrasonic pens are master and slave, namely, each pen can be used as a master pen and a slave pen; the double-pen writing method comprises the following steps:
1) when any ultrasonic pen or two ultrasonic pens start to work, periodically transmitting ultrasonic signals and infrared signals, and calculating the distance from a pen-falling point of the ultrasonic pen to the two signal receivers by the electronic whiteboard;
2) calculating the position of the ultrasonic pen falling point on the electronic whiteboard according to the distance acquired in the step 1);
3) judging a working area of the ultrasonic pen by using the obtained position of the pen-falling point of the ultrasonic pen, generating a position area state instruction, wherein the area refers to a writing area and an edge area, and transmitting the obtained position area state instruction to the ultrasonic pen by wireless transmission;
(1) when the position area state instruction is '0', the ultrasonic pen works in the writing area, the working period of the ultrasonic pen is unchanged and is T1；
(2) When the position area state instruction is '1', the ultrasonic pen works in the edge area, at the moment, the work period needs to be recalculated, and the work period is changed into T2；
The work area of the ultrasonic pen is judged by utilizing the position of the obtained pen point of the ultrasonic pen, and when the two pens work simultaneously, four conditions can appear in the work area where the two pens are located:
① the master pen works '0' in the writing area and the slave pen works '0' in the writing area;
② the master pen works '1' in the writing area and the slave pen works '0' in the border area;
③ the master pen works '0' in the border area and the slave pen works '1' in the writing area;
④ the master pen works '1' in the border area and the slave pen works '1' in the border area;
when the situation ① occurs, both ultrasonic pens are working in the writing area, and the average writing time of both ultrasonic pens in the period isWriting can be completed in a working period, and the working period of the two pens is not changed;
when the situation ② occurs, if the main pen is working in the writing area for a time period ofThe slave pen works in the edge area, and the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the farthest ultrasonic receiving end for the required time t1＝L1C, the total time required for transmitting the extracted information to the PC computer to calculate handwriting is m, and the total time is more thanSo that the working period is required to be prolonged from the pen to T2The simultaneous delay is changed intoThe pulse period of the master pen is changed to T so that the master pen does not generate signal conflict with the slave pen during stable writing2The simultaneous delay is changed into
When the situation ③ occurs, if the main pen works in the edge area, the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the far-distance ultrasonic receiving end, the required time is m, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the total required time is more thanSo that the slave ultrasonic pen needs time delayThen the infrared pulse of the user is transmitted, and the total work period is prolonged to T2The pulse period of the slave pen is also changed to T2The simultaneous delay is changed into
When the situation ④ occurs, both pens are in the border area, and the time period is changed to T2The effective infrared pulse of (2) and the simultaneous delay are changed into half of the period
4) When the ultrasonic pen is ready to work, whether the other pen is in a working state or not is judged by detecting whether the other pen emits infrared rays or not;
(1) if the other pen does not work, the ultrasonic pen which starts to work at the moment is taken as a main pen, and the main pen in the current working period immediately starts to work by pressing a pen point according to a position area state instruction of the ultrasonic pen obtained by wireless transmission:
(2) if the other pen is in a working state, the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, the working period and the delay time length of the current two pens are determined by the position area state instructions of the two ultrasonic pens acquired by wireless transmission, and the complete infrared pulse of the master pen is detected after the slave pen t and then delayedOrAfter the pen point is pressed down to start working, i.e. from the time of preparing the pen to start working when the pen point is pressed downOr
The time from the preparation of the pen to the start of the pen when the pen point is pressed downOrThe calculation method is as follows:
when two pens work in a writing area simultaneously and are ready to start working in a pen period, the method for calculating the total time duration is as follows:
1) when the slave pen is ready to start working in the second half period of the main pen, a complete and effective infrared pulse is detected after t,so that the slave pen is delayed after detecting the effective infrared pulseThe pen point is pressed down to start emitting its own infrared pulse, so that the time from the preparation of the pen to the pressing of the pen point to emit its own infrared pulsetu1Is the pulse width;
2) when the slave pen is just ready to start working when the master pen emits infrared pulses, the slave pen is immediately delayedThen pressing the pen point to start emitting its own infrared signalFor emitting infrared pulses from the time when the pen is ready to operate to the time when the pen tip is pressedt＝tu1；
3) When the slave pen is ready to start working when the master pen has just started to emit an infrared pulse, at which time the leading edge pulse of the master pen is missed, the pulse is considered invalid, the slave pen continues to detect until a complete infrared pulse is detected, so te (T ∈)1,T1+tu1) Is delayed againThen pressing down the pen point to start emitting its own infrared pulse, and detecting from the time of pen preparation to emit its own infrared pulse
4) When the slave pen is just ready for work at the falling edge of the infrared pulse emitted by the master pen, the incomplete infrared pulse is judged in the absence of the rising edge of the infrared pulse, and the pulse is considered to be invalid at the moment, so the pen continues to detect until the complete effective infrared pulse is detected, and at T, T1Detecting complete infrared pulse and delayingPressing the pen point to send out its own infrared pulse
5) When the slave pen is ready to start working in the first half cycle of the master pen, a complete valid infrared pulse is detected after t,re-delayingThe pen point is pressed to emit its own infrared pulse, so that it can be used for starting to emit its own infrared pulse after the pen is started to prepare and the complete and effective infrared pulse is detected
When one or both of the two pens are working in the border area, the working period is changed to T2The corresponding delay is changed into
The ultrasonic signals transmitted by the two ultrasonic pens in the step 1) are ultrasonic waves with the same waveform and the fKHz frequency, and in order to distinguish the two ultrasonic pens, the infrared signals transmitted by the two ultrasonic pens have the T-shaped period1The pulse widths are tu1、tu2The size of the electronic white plate is a smooth surface of a x b.
The method for calculating the distance from the ultrasonic pen point to the two signal receivers in the step 1) comprises the following steps:
wherein,the ultrasonic waves respectively sent by the ultrasonic pen at the pen-falling point S (x, y) reach a signal receiver R on the electronic whiteboard1、R2Time of (SR)1、SR2The distances from the pen point to the two receivers are respectively, the distance between the two receivers is L, and c is the propagation speed of the ultrasonic wave.
4. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the method for calculating the position of the ultrasonic pen on the electronic whiteboard in the step 2) is as follows:
wherein, the coordinates of the pen point on the electronic whiteboard are S (x, y), and the receiver R1Has the coordinates of (0,0) and R2Is (L,0) while the distance of the two receivers is known to be L.
The method for calculating the working area of the ultrasonic pen in the step 3) comprises the following steps:
1) the work period of the ultrasonic pen on the electronic whiteboard is T1The receiving end removes noise after receiving the ultrasonic pulse, then amplifies and extracts the time delay signal, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the two ultrasonic pens are at T1When the ultrasonic pens work simultaneously, the average working time of each ultrasonic pen isSo that the time for the ultrasonic pen to transmit the ultrasonic pulse to the two receiving ends to completely receive the ultrasonic signal isI.e. the farthest signal distance received by any receiving end isSo that it can be determined whether the receiver is configured with any one of the receiving endsThe area working in the circle with the radius is a writing area, and the area state instruction is marked as '0';
2) on the electronic whiteboard, the other areas except the writing area are edge areas, that isThe zone status command is now marked as '1'.
In the invention, when the position area state command in step 3) is '1', the ultrasonic pen works in the edge area, and the calculation method for recalculating the working period in which the ultrasonic pen can complete writing in a short time is as follows:
1) when the ultrasonic pen works in the edge area, the distance from the pen-falling point of the ultrasonic pen to any receiving end isSo that the time required for the ultrasonic wave to be received by the ultrasonic wave receiving terminalS1The farthest distance S from the position of the ultrasonic pen point to the farthest receiving end1≥L1Time required for the ultrasonic wave to be received by the farthest receiving end: t is tS＝S1/c；
2) The total time required for transmitting the extracted information to a PC (personal computer) for calculating handwriting is m, and the total time is more than m + t1Is less than m + tsAnd is andthe time for completing writing in the period of the two pens is prolonged toAt this time, the total work period is prolonged to T2。
The step 4) of determining whether another pen is in a working state by detecting whether another pen emits infrared signals means that when the ultrasonic pen detects infrared signals of other pens, it indicates that the other pens are working, and if no infrared signals are detected, it indicates that no other pens are working.
If the other pen is in a working state in the step 4), the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, and after the complete infrared pulse of the master pen is detected after the slave pen t, the time is delayedOrThen, the pen point is pressed down to start working, specifically: when both pens are working in the writing area, the time delay from penRear working, when any one or both of the two ultrasonic pens works in the edge area, delaying the time from the penAnd then starts working.
The invention has the advantages that the working state and the position area of the two pens are judged by utilizing the time division multiplexing principle to realize the alternate writing work of the two pens in the working period, firstly, different pulse widths of infrared signals are used as the time reference for distinguishing the two pens, whether the two pens are in the working state is judged by receiving the infrared signal sent by the other pen, then, the self working logic time sequence is realized by combining the position area state instruction obtained by wireless transmission, and the pen point is pressed to start working. The double-pen writing can be used for interactive electronic teaching, interactive meetings, training and the like.
Drawings
Fig. 1 is a schematic structural diagram of an electronic whiteboard of the present invention;
FIG. 2 is a schematic diagram of the structure of the ultrasonic pen of the present invention;
FIG. 3 is a schematic diagram of the positioning of an ultrasonic electronic whiteboard of the present invention;
FIG. 4 is a schematic view of the working area of an ultrasonic pen of the present invention;
FIG. 5 is a timing diagram illustrating the encoding of the effective IR pulses emitted from the pen according to the present invention;
FIG. 5A is a timing diagram of the invention from the time the pen is ready to begin operation in area ①;
FIG. 5B is a timing diagram of the invention from the time the pen is ready to begin operation in area ②;
FIG. 5C is a timing diagram of the invention from the time the pen is ready to begin operation in area ③;
FIG. 5D is a timing diagram of the invention from the time the pen is ready to begin operation in area ④;
FIG. 5E is a timing diagram of the invention from the time the pen is ready to begin operation in area ⑤;
FIG. 6 is a flow chart of the dual pen writing process of the present invention.
Detailed Description
The electronic whiteboard comprises two signal receivers and a smooth writing plane, the signal receivers are used for receiving infrared signals and ultrasonic signals which are transmitted by the two ultrasonic pens, the two ultrasonic pens comprise infrared transmitters capable of transmitting infrared with the same wavelength and ultrasonic transmitters capable of transmitting ultrasonic waves with the same frequency, and can receive infrared signals transmitted by the other ultrasonic pen and position information acquired by wireless transmission, the two ultrasonic pens are master and slave, namely, each pen can be used as a master pen and a slave pen; the double-pen writing method comprises the following steps:
1) when any ultrasonic pen or two ultrasonic pens start to work, periodically transmitting ultrasonic signals and infrared signals, and calculating the distance from a pen-falling point of the ultrasonic pen to the two signal receivers by the electronic whiteboard;
2) calculating the position of the ultrasonic pen falling point on the electronic whiteboard according to the distance acquired in the step 1);
3) judging a working area of the ultrasonic pen by using the obtained position of the pen-falling point of the ultrasonic pen, generating a position area state instruction, wherein the area refers to a writing area and an edge area, and transmitting the obtained position area state instruction to the ultrasonic pen by wireless transmission;
(1) when the position area state instruction is '0', the ultrasonic pen works in the writing area, the working period of the ultrasonic pen is unchanged and is T1；
(2) When the position area state instruction is '1', the ultrasonic pen works in the edge area, at the moment, the work period needs to be recalculated, and the work period is changed into T2；
The work area of the ultrasonic pen is judged by utilizing the position of the obtained pen point of the ultrasonic pen, and when the two pens work simultaneously, four conditions can appear in the work area where the two pens are located:
① the master pen works '0' in the writing area and the slave pen works '0' in the writing area;
② the master pen works '1' in the writing area and the slave pen works '0' in the border area;
③ the master pen works '0' in the border area and the slave pen works '1' in the writing area;
④ the master pen works '1' in the border area and the slave pen works '1' in the border area;
when the situation ① occurs, both ultrasonic pens are working in the writing area, and the average writing time of both ultrasonic pens in the period isWriting can be completed in a working period, and the working period of the two pens is not changed;
when the situation ② occurs, if the main pen is working in the writing area for a time period ofThe slave pen works in the edge area, and the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the farthest ultrasonic receiving end for the required time t1＝L1C, the total time required for transmitting the extracted information to the PC computer to calculate handwriting is m, and the total time is more thanSo that the working period is required to be prolonged from the pen to T2The simultaneous delay is changed intoThe pulse period of the master pen is changed to T so that the master pen does not generate signal conflict with the slave pen during stable writing2The simultaneous delay is changed into
When the situation ③ occurs, if the main pen works in the edge area, the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the far-distance ultrasonic receiving end, the required time is m, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the total required time is more thanSo that the slave ultrasonic pen needs time delayThen the infrared pulse of the user is transmitted, and the total work period is prolonged toT2The pulse period of the slave pen is also changed to T2The simultaneous delay is changed into
When the situation ④ occurs, both pens are in the border area, and the time period is changed to T2The effective infrared pulse of (2) and the simultaneous delay are changed into half of the period
4) When the ultrasonic pen is ready to work, whether the other pen is in a working state or not is judged by detecting whether the other pen emits infrared rays or not;
(1) if the other pen does not work, the ultrasonic pen which starts to work at the moment is taken as a main pen, and the main pen in the current working period immediately starts to work by pressing a pen point according to a position area state instruction of the ultrasonic pen obtained by wireless transmission:
(2) if the other pen is in a working state, the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, the working period and the delay time length of the current two pens are determined by the position area state instructions of the two ultrasonic pens acquired by wireless transmission, and the complete infrared pulse of the master pen is detected after the slave pen t and then delayedOrAfter the pen point is pressed down to start working, i.e. from the time of preparing the pen to start working when the pen point is pressed downOr
The slave pen guideFrom the start of the operation to the start of the operation by pressing the pen pointOrThe calculation method is as follows:
when two pens work in a writing area simultaneously and are ready to start working in a pen period, the method for calculating the total time duration is as follows:
1) when the slave pen is ready to start working in the second half period of the main pen, a complete and effective infrared pulse is detected after t,so that the slave pen is delayed after detecting the effective infrared pulseThe pen point is pressed down to start emitting its own infrared pulse, so that the time from the preparation of the pen to the pressing of the pen point to emit its own infrared pulsetu1Is the pulse width;
2) when the slave pen is just ready to start working when the master pen emits infrared pulses, the slave pen is immediately delayedThe pen point is pressed down to emit its own infrared signal, so that the time from the time when the pen is ready to start working to the time when the pen point is pressed down to emit its own infrared pulset＝tu1；
3) When the slave pen just starts to emit infrared pulses at the master penAnd (4) starting to work, missing the rising edge pulse of the main pen at the moment, considering the pulse as invalid, and continuing to detect the secondary pen until detecting a complete infrared pulse, so T e (T e)1,T1+tu1) Is delayed againThen pressing down the pen point to start emitting its own infrared pulse, and detecting from the time of pen preparation to emit its own infrared pulse
4) When the slave pen is just ready for work at the falling edge of the infrared pulse emitted by the master pen, the incomplete infrared pulse is judged in the absence of the rising edge of the infrared pulse, and the pulse is considered to be invalid at the moment, so the pen continues to detect until the complete effective infrared pulse is detected, and at T, T1Detecting complete infrared pulse and delayingPressing the pen point to send out its own infrared pulse
5) When the slave pen is ready to start working in the first half cycle of the master pen, a complete valid infrared pulse is detected after t,re-delayingThe pen point is pressed to emit its own infrared pulse, so that it can be used for starting to emit its own infrared pulse after the pen is started to prepare and the complete and effective infrared pulse is detected
When one or both of the two pens are working in the border area, the working period is changed to T2The corresponding delay is changed into
The ultrasonic signals transmitted by the two ultrasonic pens in the step 1) are ultrasonic waves with the same waveform and the fKHz frequency, and in order to distinguish the two ultrasonic pens, the infrared signals transmitted by the two ultrasonic pens have the T-shaped period1The pulse widths are tu1、tu2The size of the electronic white plate is a smooth surface of a x b.
The method for calculating the distance from the ultrasonic pen point to the two signal receivers in the step 1) comprises the following steps:
wherein,the ultrasonic waves respectively sent by the ultrasonic pen at the pen-falling point S (x, y) reach a signal receiver R on the electronic whiteboard1、R2Time of (SR)1、SR2The distances from the pen point to the two receivers are respectively, the distance between the two receivers is L, and c is the propagation speed of the ultrasonic wave.
4. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the method for calculating the position of the ultrasonic pen on the electronic whiteboard in the step 2) is as follows:
wherein, the coordinates of the pen point on the electronic whiteboard are S (x, y), and the receiver R1Has the coordinates of (0,0) and R2Is (L,0) while the distance of the two receivers is known to be L.
The method for calculating the working area of the ultrasonic pen in the step 3) comprises the following steps:
1) the work period of the ultrasonic pen on the electronic whiteboard is T1The receiving end removes noise after receiving the ultrasonic pulse, then amplifies and extracts the time delay signal, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the two ultrasonic pens are at T1When the ultrasonic pens work simultaneously, the average working time of each ultrasonic pen isSo that the time for the ultrasonic pen to transmit the ultrasonic pulse to the two receiving ends to completely receive the ultrasonic signal isI.e. the farthest signal distance received by any receiving end isSo that it can be determined whether the receiver is configured with any one of the receiving endsThe area working in the circle with the radius is a writing area, and the area state instruction is marked as '0';
2) on the electronic whiteboard, the other areas except the writing area are edge areas, that isThe zone status command is now marked as '1'.
In the invention, when the position area state command in step 3) is '1', the ultrasonic pen works in the edge area, and the calculation method for recalculating the working period in which the ultrasonic pen can complete writing in a short time is as follows:
1) when the ultrasonic pen works in the edge area, the distance from the pen-falling point of the ultrasonic pen to any receiving end isSo that the time required for the ultrasonic wave to be received by the ultrasonic wave receiving terminalS1The farthest distance S from the position of the ultrasonic pen point to the farthest receiving end1≥L1Time required for the ultrasonic wave to be received by the farthest receiving end: t is tS＝S1/c；
2) The total time required for transmitting the extracted information to a PC (personal computer) for calculating handwriting is m, and the total time is more than m + t1Is less than m + tsAnd is andthe time for completing writing in the period of the two pens is prolonged toAt this time, the total work period is prolonged to T2。
The step 4) of determining whether another pen is in a working state by detecting whether another pen emits infrared signals means that when the ultrasonic pen detects infrared signals of other pens, it indicates that the other pens are working, and if no infrared signals are detected, it indicates that no other pens are working.
If the other pen is in a working state in the step 4), the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, and after the complete infrared pulse of the master pen is detected after the slave pen t, the time is delayedOrThen, the pen point is pressed down to start working, specifically: when both pens are working in the writing area, the time delay from penRear working, when any one or both of the two ultrasonic pens works in the edge area, delaying the time from the penAnd then starts working.
The invention will be described in further detail below with reference to the accompanying drawings and specific examples in order to provide those skilled in the art with a better understanding of the invention.
1. Fig. 1 and fig. 2 are schematic diagrams of an electronic whiteboard with an ultrasonic pen according to an application of the present invention, which includes an electronic whiteboard 100 and an empty mouse pen 200, where the electronic whiteboard 100 mainly includes a whiteboard 101, 2 signal receivers one 102 and two signal receivers 103, and the signal receivers mainly receive ultrasonic signals and infrared signals; the ultrasonic pen 200 mainly comprises a pen point 201, a PVDF ultrasonic film 202, an infrared transmitting tube 203, a key 204, an infrared receiving tube 206, a microprocessor [205, and the like; referring to fig. 3 and 300, when a button 204 of an ultrasonic pen is triggered on a writing plane 301, a PVDF ultrasonic film 202 and an infrared transmitting tube 203 transmit ultrasonic signals and infrared signals to signal generators 303 and 304, the infrared signals are used as time bases for distinguishing the two pens, the ultrasonic pen is positioned by an ultrasonic positioning technology, and then position coordinates S (x, y)302 of the ultrasonic pen are obtainedThe frequency of ultrasonic signals emitted by the sound pen is 40KHz, and the period of infrared signals emitted by the sound pen is T116ms, the pulses are tu1＝176us、tu2The size of the whiteboard is a smooth surface of 2m × 1.2m, 180 us.
The distance calculation method from the ultrasonic pen point to the two ultrasonic receivers is as follows:
wherein,the ultrasonic waves respectively sent by the ultrasonic pen at the pen-falling point S (x, y) reach a signal receiver R on the electronic whiteboard1、R2Time of (SR)1、SR2The distances from the pen-down point to the two receivers are respectively L and c;
the position calculation method of the ultrasonic pen on the electronic whiteboard is as follows:
wherein, the coordinates of the pen point on the electronic whiteboard are S (x, y), and the receiver R1Has the coordinates of (0,0) and R2Is (L,0), while the distance of the two receivers is known to be L;
2. referring to fig. 4, fig. 4 is a schematic diagram 400 of a working area of an ultrasonic pen, when a button 204 of the ultrasonic pen is triggered, the PVDF ultrasonic film 202 and the infrared transmitting tube 203 respectively transmit an ultrasonic signal and an infrared signal, and the signal transmitting end 403 receives the ultrasonic signal and the infrared signal transmitted by the ultrasonic pen, the specific calculation method of the working area of the ultrasonic pen is as follows:
1) the work period of the ultrasonic pen on the electronic whiteboard is T1The receiving end 403 removes noise after receiving the ultrasonic pulse, then amplifies and extracts the time delay signal, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the two ultrasonic pens are at T1When the ultrasonic pens work simultaneously, the average working time of each ultrasonic pen isSo that the time taken for the ultrasonic pen to transmit the ultrasonic pulse until the ultrasonic signal is completely received by the two receiving ends 403 isI.e., the farthest signal distance 404 received by either receiver isSo that it can be determined whether the receiver is configured with any one of the receiving endsThe area that works in a circle of radius is the writing area [402]At this time, the region instruction is recorded as '0'
2) On the electronic whiteboard, the area other than the writing area is the edge area [401 ]]I.e. byThe area command is marked as '1';
when the ultrasonic pen works in the edge area, the calculation method for recalculating the working period that the ultrasonic pen can complete writing is as follows:
1) ultrasonic pen is onWhen the edge area works, the distance from the position of the pen-falling point of the ultrasonic pen to any receiving end isSo that the time required for the ultrasonic wave to be received by the ultrasonic wave receiving terminalS is the farthest distance from the position of the pen falling point of the ultrasonic pen to the farthest receiving end, and S is the farthest distance from the pen falling point of the ultrasonic pen to the farthest receiving end1≥L1Time required for the ultrasonic wave to be received by the farthest receiving end: t is tS＝S1/c；
2) The total time required for transmitting the extracted information to a PC (personal computer) for handwriting calculation is m, and the total time is more than c + t1Is less thanThe time for completing writing in the period of the two pens is prolonged toAt this time, the total work period is prolonged to T2In practical cases, we actually measure c as 4ms t1>4ms，tS＝8.79ms，S1＝1.63m，T2＝18ms，L＝0.16m，c＝340m/s；
When two pens work simultaneously, four conditions can appear in the working area where the two pens are located:
1) the master pen works '0' in the writing area 402, and the slave pen works '0' in the writing area 402;
2) the master pen works '1' in the writing area 402 and the slave pen works '0' in the border area 401;
3) the master pen works '0' in the border area 401 and the slave pen works '1' in the writing area 402;
4) the master pen works '1' in the border area 401, and the slave pen works '1' in the border area 401;
in case 1), both the two ultrasonic pens work in the writing area 402, and the average writing time of both the two ultrasonic pens in the period is 8ms, so that writing can be completed in the working period, and the working periods of both the two ultrasonic pens do not change;
in case 2), if the working time of the main pen in the writing area 402 is 8ms, the slave pen works in the edge area 401, and the ultrasonic pulse emitted by the ultrasonic pen in the edge area 401 is received by the farthest ultrasonic receiving end for the required time t1＝L1/c>4ms, the total time required for transmitting the extracted information to a PC (personal computer) to calculate handwriting is 4ms, and the total required time is more than 8ms, so that the working period of the slave pen needs to be prolonged to 18ms, the delay is changed to 9ms, the pulse period of the master pen is also changed to 18ms, and the delay is changed to 9ms in order that the master pen and the slave pen do not generate signal collision during stable writing;
the situation 3) is that if the main pen works in the edge area 401, the ultrasonic pulse sent by the ultrasonic pen in the edge area 401 is received by the far-away ultrasonic receiving end, and the required time t is1＝L1The total time for transmitting the extracted information to a PC (personal computer) to calculate handwriting is 4ms, and the total time is more than 8ms, so that the ultrasonic pen starts to transmit own infrared pulse after delaying for 9ms, the total working period is prolonged to 18ms, the pulse period of the ultrasonic pen is changed to 18ms, and the delay is changed to 9 ms;
in case 4), both pens are in the border area 401, at this time the time period is changed to 18ms of effective infrared pulses, and the delay is changed to one half of the period of 9 ms;
fig. 5 is a timing chart 500 of the active ir pulse code transmitted by the master pen, in which the slave pen starts to operate in the areas 501, 502, 503, 504, 505, the period of the master pen operation is 16ms, that is, the time of the slave pen operation can occur at any time of the 16ms, and fig. 5A, 5B, 5C, 5D, and 5E are all the cases of the time of the slave pen operation in one period.
Fig. 5A is a timing chart 501 when the pen preparation start time appears in the area ①, the pen preparation start operation is performed at the second half cycle 5010 of the cycle, a complete effective infrared pulse is detected after tms, and t ∈ (176us,8ms +176us), so that the pen presses the pen tip 5011 with a delay of 8ms after detecting the effective infrared pulse, and starts emitting its own infrared pulse, so that the time t +8ms is from the preparation start operation to the pen tip start operation.
Fig. 5B is a timing chart when the pen preparation start timing appears in the region ②, since the preparation start timing 5020 is immediately after the main pen emits the infrared pulse, and the pen tip 5021 is pressed by 8ms from the time immediately after the pen starts emitting the infrared signal of its own, t +8ms, t is 176us, from the time when the pen starts to operate from the preparation start to the time when the pen tip starts to operate.
Fig. 5C is a timing chart 503 when the time point when the pen is ready to start operating appears in the region ③, the time point when the pen is ready to start operating 5030 just when the main pen emits the infrared pulse just misses the rising edge of the main pen, the pulse is considered invalid at this time, the pen continues to detect until the complete infrared pulse is detected, so t ∈ (16ms,16+176us), the pen tip 5031 is pressed after a delay of 8ms to start emitting its own infrared pulse, and the time t +8ms is taken from the time when the pen is ready to start operating to the time when it emits its own infrared pulse.
Fig. 5D is a timing chart 504 when the pen preparation start timing appears in the region ④, the pen preparation start timing 5040 is when the pen preparation start timing is immediately after the main pen emits the falling edge of the infrared pulse, the pen is judged to be an incomplete infrared pulse in the absence of the rising edge of the infrared pulse, and the pulse is considered to be invalid at this time, so the pen continues to detect until the complete valid infrared pulse is detected, the complete infrared pulse is detected at t 16ms, and the pen tip 5041 is pressed down after a delay of 8ms to emit its own infrared pulse, which takes t +8 ms.
Fig. 5E shows the timing diagram 505 when the pen is ready to start working in the region ⑤, the pen is ready to start working 5050 in the first half cycle of the main pen working, and a full valid ir pulse is detected after tms, te (8+176us,16ms), so that pressing the pen tip 5051 after the full valid ir pulse is detected in the second pen starts emitting its ir pulse for t +8 ms.
Fig. 6 is a flow chart 600 of double-pen writing, which is implemented by initializing 602 an ultrasonic pen to be operated, detecting whether infrared exists around 603, determining whether infrared is emitted by a main pen or an interference signal 604 if infrared is detected, setting an infrared flag bit emitted by the main pen to 1 if infrared is emitted by the main pen, starting a timer 605, determining an upper limit (16ms or 18ms) of accumulated timing of the timer according to a position of a pen-down point of the main pen and the auxiliary pen, pressing a pen point 606 of the auxiliary pen, calculating a delay time and delaying 608 in case 607 the main pen is operated, emitting ultrasonic waves and infrared rays 609, and continuing to detect infrared; if no other pen is working after the pen point is pressed down, the timer is clear 0610 and infrared detection is continued.
The foregoing description is directed to particular embodiments, and other variations and modifications may be made to the described embodiments in order to achieve more operation or convenient writing, in the course of practical implementation. As such, these descriptions should be construed as merely illustrative of various principles and not a limitation thereof.

Claims (8)

1. An electronic whiteboard double-pen writing method based on ultrasonic waves is characterized in that: the electronic whiteboard comprises two signal receivers and a smooth writing plane, the signal receivers are used for receiving infrared signals and ultrasonic signals which are transmitted by the two ultrasonic pens, the two ultrasonic pens comprise infrared transmitters capable of transmitting infrared with the same wavelength and ultrasonic transmitters capable of transmitting ultrasonic waves with the same frequency, and can receive infrared signals transmitted by the other ultrasonic pen and position information acquired by wireless transmission, the two ultrasonic pens are master and slave, namely, each pen can be used as a master pen and a slave pen; the double-pen writing method comprises the following steps:
1) when any ultrasonic pen or two ultrasonic pens start to work, periodically transmitting ultrasonic signals and infrared signals, and calculating the distance from a pen-falling point of the ultrasonic pen to the two signal receivers by the electronic whiteboard;
2) calculating the position of the ultrasonic pen falling point on the electronic whiteboard according to the distance acquired in the step 1);
3) judging a working area of the ultrasonic pen by using the obtained position of the pen-falling point of the ultrasonic pen, generating a position area state instruction, wherein the area refers to a writing area and an edge area, and transmitting the obtained position area state instruction to the ultrasonic pen by wireless transmission;
(1) when the position area state instruction is '0', the ultrasonic pen works in the writing area, the working period of the ultrasonic pen is unchanged and is T1；
(2) When the position area state instruction is '1', the ultrasonic pen works in the edge area, at the moment, the work period needs to be recalculated, and the work period is changed into T2；
The work area of the ultrasonic pen is judged by utilizing the position of the obtained pen point of the ultrasonic pen, and when the two pens work simultaneously, four conditions can appear in the work area where the two pens are located:
① the master pen works '0' in the writing area and the slave pen works '0' in the writing area;
② the master pen works '1' in the writing area and the slave pen works '0' in the border area;
③ the master pen works '0' in the border area and the slave pen works '1' in the writing area;
④ the master pen works '1' in the border area and the slave pen works '1' in the border area;
when the situation ① occurs, both ultrasonic pens are working in the writing area, and the average writing time of both ultrasonic pens in the period isWriting can be completed in a working period, and the working period of the two pens is not changed;
when the situation ② occurs, if the main pen is working in the writing area for a time period ofThe slave pen works in the edge area, and the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the farthest ultrasonic receiving end for the required time t1＝L1/c，L1The distance from the position of the ultrasonic pen point to any receiving end, c is the propagation speed of the ultrasonic wave, the total time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the total time is more thanSo that the working period is required to be prolonged from the pen to T2The simultaneous delay is changed intoThe pulse period of the master pen is changed to T so that the master pen does not generate signal conflict with the slave pen during stable writing2The simultaneous delay is changed into
When the situation ③ occurs, if the main pen works in the edge area, the ultrasonic pulse sent by the ultrasonic pen in the edge area is received by the far-distance ultrasonic receiving end, and the required time t1＝L1C, the total time required for transmitting the extracted information to the PC computer to calculate handwriting is m, and the total time is more thanSo that the slave ultrasonic pen needs time delayStarting to emit from behindThe infrared pulse is generated, and the total work period is prolonged to T2The pulse period of the slave pen is also changed to T2The simultaneous delay is changed into
When the situation ④ occurs, both pens are in the border area, and the time period is changed to T2The effective infrared pulse of (2) and the simultaneous delay are changed into half of the period
4) When the ultrasonic pen is ready to work, whether the other pen is in a working state or not is judged by detecting whether the other pen emits infrared rays or not;
(1) if the other pen does not work, the ultrasonic pen which starts to work at the moment is taken as a main pen, and the main pen in the current working period immediately starts to work by pressing a pen point according to a position area state instruction of the ultrasonic pen obtained by wireless transmission:
(2) if the other pen is in a working state, the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, the working period and the delay time length of the current two pens are determined by the position area state instructions of the two ultrasonic pens acquired by wireless transmission, and the complete infrared pulse of the master pen is detected after the slave pen t and then delayedOrAfter the pen point is pressed down to start working, i.e. from the time of preparing the pen to start working when the pen point is pressed downOr
The above-mentionedFrom the time of preparation of the pen to the time of starting operation by pressing down the pen tipOrThe calculation method is as follows:
when two pens work in a writing area simultaneously and are ready to start working in a pen period, the method for calculating the total time duration is as follows:
1) when the slave pen is ready to start working in the second half period of the main pen, a complete and effective infrared pulse is detected after t,so that the slave pen is delayed after detecting the effective infrared pulseThe pen point is pressed down to start emitting its own infrared pulse, so that the time from the preparation of the pen to the pressing of the pen point to emit its own infrared pulsetu1Is the pulse width;
2) when the slave pen is just ready to start working when the master pen emits infrared pulses, the slave pen is immediately delayedThe pen point is pressed down to emit its own infrared signal, so that the time from the time when the pen is ready to start working to the time when the pen point is pressed down to emit its own infrared pulset＝tu1；
3) When the slave pen just starts to emit infrared pulses at the master penReady to begin working, at which time the leading edge pulse of the master pen is missed, the pulse is considered invalid, the slave pen continues to detect until a complete infrared pulse is detected, so T e (T e)1,T1+tu1) Is delayed againThen pressing down the pen point to start emitting its own infrared pulse, and detecting from the time of pen preparation to emit its own infrared pulse
4) When the slave pen is just ready for work at the falling edge of the infrared pulse emitted by the master pen, the incomplete infrared pulse is judged in the absence of the rising edge of the infrared pulse, and the pulse is considered to be invalid at the moment, so the pen continues to detect until the complete effective infrared pulse is detected, and at T, T1Detecting complete infrared pulse and delayingPressing the pen point to send out its own infrared pulse
5) When the slave pen is ready to start working in the first half cycle of the master pen, a complete valid infrared pulse is detected after t,re-delayingThe pen point is pressed to emit its own infrared pulse, so that it can be used for starting to emit its own infrared pulse after the pen is started to prepare and the complete and effective infrared pulse is detected
When one or both of the two pens are working in the border area, the working period is changed to T2The corresponding delay is changed into
2. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the ultrasonic signals transmitted by the two ultrasonic pens in the step 1) are ultrasonic waves with the same wave form and fKHz frequency, and in order to distinguish the two ultrasonic pens, the infrared signals transmitted by the two ultrasonic pens have T periods1The pulse widths are tu1、tu2The size of the electronic white plate is a smooth surface of a x b.
3. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the method for calculating the distance from the ultrasonic pen point to the two signal receivers in the step 1) is as follows:
wherein,the ultrasonic waves respectively sent by the ultrasonic pen at the pen-falling point S (x, y) reach a signal receiver R on the electronic whiteboard1、R2Time of (SR)1、SR2Respectively the distance from the pen point to the two receivers, the distance between the two receivers is L, and c is superThe speed of sound wave propagation.
4. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the method for calculating the position of the ultrasonic pen on the electronic whiteboard in the step 2) is as follows:
wherein, the coordinates of the pen point on the electronic whiteboard are S (x, y), and the receiver R1Has the coordinates of (0,0) and R2Is (L,0) while the distance of the two receivers is known to be L.
5. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the method for calculating the working area of the ultrasonic pen in the step 3) comprises the following steps:
1) the work period of the ultrasonic pen on the electronic whiteboard is T1The receiving end removes noise after receiving the ultrasonic pulse, then amplifies and extracts the time delay signal, the time required for transmitting the extracted information to the PC to calculate the handwriting is m, and the two ultrasonic pens are at T1When the ultrasonic pens work simultaneously, the average working time of each ultrasonic pen isSo that the time for the ultrasonic pen to transmit the ultrasonic pulse to the two receiving ends to completely receive the ultrasonic signal isI.e. the farthest signal distance received by any receiving end isSo that it can be determined whether the receiver is configured with any one of the receiving endsThe area working in the circle with the radius is a writing area, and the area state instruction is marked as '0';
2) on the electronic whiteboard, the other areas except the writing area are edge areas, that isThe zone status command is now marked as '1'.
6. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: when the command for setting the state of the position area in step 3) is '1', the ultrasonic pen works in the edge area, and the calculation method for recalculating the working period in which the ultrasonic pen can complete writing in a short time is as follows:
1) when the ultrasonic pen works in the edge area, the distance from the pen-falling point of the ultrasonic pen to any receiving end isSo that the time required for the ultrasonic wave to be received by the ultrasonic wave receiving terminalS1The farthest distance S from the position of the ultrasonic pen point to the farthest receiving end1≥L1Time required for the ultrasonic wave to be received by the farthest receiving end: t is tS＝S1/c；
2) The total time required for transmitting the extracted information to a PC (personal computer) for calculating handwriting is m, and the total time is more than m + t1Is less than m + tsAnd is andthe time for completing writing in the period of the two pens is prolonged toAt this time, the total work period is prolonged to T2。
7. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: the step 4) of determining whether the other pen is in the working state by detecting whether the other pen emits infrared light means that when the ultrasonic pen detects infrared signals of the other pen, it indicates that the other pen is working, and if the infrared signal is not detected, it indicates that no other pen is working.
8. The ultrasonic-based electronic whiteboard double-pen writing method according to claim 1, characterized in that: if the other pen is in a working state in the step 4), the other pen is a master pen, the ultrasonic pen which starts working is a slave pen, and after the complete infrared pulse of the master pen is detected after the slave pen t, the time is delayedOrThen, the pen point is pressed down to start working, specifically: when both pens are working in the writing area, the time delay from penRear working, when any one or both of the two ultrasonic pens works in the edge area, delaying the time from the penAnd then starts working.
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