WO2008135846A1 - Procédé de localisation et de suivi de sources élastiques dans des supports minces - Google Patents

Procédé de localisation et de suivi de sources élastiques dans des supports minces Download PDF

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Publication number
WO2008135846A1
WO2008135846A1 PCT/IB2008/001104 IB2008001104W WO2008135846A1 WO 2008135846 A1 WO2008135846 A1 WO 2008135846A1 IB 2008001104 W IB2008001104 W IB 2008001104W WO 2008135846 A1 WO2008135846 A1 WO 2008135846A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
determining
sensors
panel
source
Prior art date
Application number
PCT/IB2008/001104
Other languages
English (en)
Inventor
Augusto Sarti
Stefano Tubaro
Diego Rovetta
Gabriele Scarparo
Original Assignee
Politecnico Di Milano
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from ITBG20070029 external-priority patent/ITBG20070029A1/it
Priority claimed from ITBG20070030 external-priority patent/ITBG20070030A1/it
Priority claimed from ITBG20070028 external-priority patent/ITBG20070028A1/it
Application filed by Politecnico Di Milano filed Critical Politecnico Di Milano
Publication of WO2008135846A1 publication Critical patent/WO2008135846A1/fr

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Classifications

    • 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
    • G06F3/0433—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using propagating acoustic waves in which the acoustic waves are either generated by a movable member and propagated within a surface layer or propagated within a surface layer and captured by a movable member

Definitions

  • the present invention relates to a method for locating and tracking elastic sources (for example tactile interactions) within thin media, such as a panel.
  • It also relates to a method for locating and tracking the contact of an object such as a pencil, a finger, a fingernail, a brush or a screwdriver, on a panel such as a screen, a shop window, a board surface, or the casing of a household domestic appliance.
  • an object such as a pencil, a finger, a fingernail, a brush or a screwdriver
  • LTM location template matching
  • the interaction point is found by comparing the measured value with the data bank containing responses corresponding to known positions on the panel, previously acquired during set-up.
  • This method is independent of the panel properties (material, shape, etc.) and the elastic wave propagation model. It requires at least one receiving sensor.
  • the set-up requires considerable time to acquire all the responses, particularly for large-surface panels, and to achieve accurate solutions.
  • this location technique is very sensitive to the environmental states (temperature, humidity, etc.). In addition it cannot solve the problem of tracking continuous interactions.
  • TDOA time delay of arrival
  • This method assumes that the elastic wave propagation velocity within the panels is constant. Consequently, from an evaluation of this velocity and the arrival time of signals acquired from different sensors, the interaction position can be calculated by effecting different triangulation procedures. The most common is the hyperbola intersection point procedure.
  • the limitation to this method is that it doles not consider the wavefront dispersion phenomena within the thin media. In this respect, within the thin media, the wave phase velocity varies with frequency, and the wavefront may not be recognizable, even of the wave has travelled only a short distance from the interaction point. The estimate of delay in the wave arrival time and the interaction point position may be inexact. In addition, even this method cannot solve the problem of tracking a continuous interaction.
  • An object of the present invention is to provide a method for locating and tracking elastic sources (for example tactile interactions) within thin media, which is simple and accurate.
  • a method for locating an elastic source on a panel comprising at least four vibrational sensors, each of which receives a vibrational signal generated by said elastic source on said panel, and each of which sends a corresponding electrical signal to a processor, comprising the steps of: determining the elastic properties of the panel; determining the corresponding dispersion curve; determining the relative distances ( ⁇ dw) between said at least four vibrational sensors and the position (x ⁇ , VT) of said elastic source; said position (XT, YT) of said elastic source being determined using the Tarantola iterative technique for non-linear inverse problems. Further characteristics of the invention are described in the dependent claims. For evaluating the position of elastic sources on a board, the method proposes to use the dispersion phenomenon as a useful information source rather than a source of disturbance.
  • the method is effective on any arbitrary surface provided it is uniform and not excessively thick.
  • the method is based on the joint analysis of the signals acquired by an assembly of 4 or more vibrational sensors. It is a passive method and hence does not require the injection of signals of any type into the panel. It is able to locate and correctly track a continuous elastic source. It is able to function on any panel (a shop window, a board surface, the casing of a household electrical appliance, a screen - LCD or CRT) provided this satisfies the following requirements.
  • a material structure which is homogeneous or semi-homogeneous (homogeneous in layers).
  • Figure 1 shows schematically an embodiment of a system for locating and tracking elastic sources within thin media, in accordance with the present invention
  • Figure 2 shows schematically a system for estimating the elastic properties of the panel
  • Figure 3 shows schematically an embodiment of a system for determining the elastic properties of the panel, in accordance with the present invention.
  • a system for locating and tracking elastic sources within thin media comprises a panel (or board) 10, and a series of vibrational sensors 11 , which are four in number in the example.
  • the sensors 11 are connected to an acquisition card 12, which possibly feeds power to the sensors 11.
  • the acquisition card 12 is connected to a computer 13.
  • a screwdriver 14 schematically represented, traces on the panel 10 a line 15, which is displayed at 16 on the computer 13.
  • the panel 10 is homogeneous or semi- homogeneous, isotropic or semi-anisotropic and is relatively thin.
  • two common materials satisfying these requirements are plexiglass (PLX) panels and medium density fibre (MDF) panels. These latter are a composite wood product, made from machined wood residual fibres glued together with resin, heated and pressed. Both have a high attenuation coefficient in the high frequency range.
  • the panel dimensions are 150 x 100 x 0.5 cm.
  • the sensors used to acquire the signals transmitted into the panel are preferably piezoelectric. For example those of type BlM 771 were used, these being accelerometers marketed by Knowles Acoustics.
  • the signal must preferably be filtered by a low pass filter, with a cut- off frequency for example between 5 and 8 kHz, to compensate the undesirable effects of non-linearity.
  • the acquisition card 12 receives the signals originating from the sensors 11 and powers them. It filters the signals and transfers them to an audio acquisition card of a computer 13.
  • the elastic properties of the medium must be known, for example the P-wave and S-wave velocities v ⁇ and v ⁇ .
  • Other quantities can be used which, as in the case of compressional and transverse velocities, are uniquely representative of the panel elastic parameters, for example Young's modulus and the Poisson coefficient, or Lame parameters, etc.
  • the calculation is done only for the a,, mode, as the sensors used, usually positioned on the panel surface, sense the. elastic displacements along the z axis, the elastic displacement component of the so mode normal to the panel being negligible at the frequencies concerned, and for these panel dimensions.
  • a transducer T converts the electrical energy into mechanical energy, which propagates through a thin panel by means of elastic waves.
  • Different implementations of the phase velocity can then be used to evaluate the panel elastic properties (for example, v ⁇ and V ⁇ ).
  • the transducer T generates a series of pulses at different frequencies, for example from 1500 Hz to 8000Hz in 250Hz steps. For each frequency the difference between the theoretical phase velocity v a C ai and measured phase velocity v a . Ob s is measured.
  • the optimum values for the P-wave and S-wave velocities can be
  • the residue R d can be minimized by an exhaustive search technique, seeing the low computation cost, or by any other known minimization technique. However the minimization problem can be poorly conditioned and require further constraints.
  • the Poisson coefficient value v can be fed in, if known.
  • phase velocity v a can be calculated at different frequencies.
  • the passive method is based on subdividing the spectrum of acquired signals induced by an elastic source into bands. At the central frequency of each band a calculation is made of the phase constant of the signals acquired by sensors (at least two) situated in known positions. An evaluation of the panel elastic properties is then made by the procedure described for the active method. A further passive method will now be described for determining the elastic properties of the panel 10. This method is more exact and robust than those previously described as it does not involve the difficulty of parameter optimization. It is based on an exhaustive search of the best adaptation between the dispersion curves for the test material and an assembly of dispersion curves stored in a data bank and obtained by simulation. This procedure also gives an evaluation of the type of material under examination.
  • the elastic source induces propagation of Lamb waves within the panel, the signal of which is acquired by the four sensors.
  • the source is preferably positioned in line with two sensors at an equal distance from them. This can facilitate operations, by averaging the value of the signals received and hence increase the signal/noise ratio.
  • a search is made to find which curve gives the best residue between a received reference signal and a calculated signal propagating with the phase velocities stored in the data bank.
  • a pair of sensors is used, of which one is taken as the reference sensor, for example the sensors R ⁇ 3 and R X4 , of which this latter is the reference sensor.
  • the relative distance is determined between the sensors Rx 3 and R X4 , knowing the position T of the elastic source: the signal S 3 propagates inversely from the sensor R ⁇ 3 to the point T and then directly towards the sensor R x4 , using one of the dispersion curves stored in the data bank, by means of the following equation, in which the frequency domain signals are considered:
  • S 3 (f) is the Fourier transform of the signal acquired at the sensor
  • Rx3, ⁇ 043 04 ⁇ - d3 ⁇ , with 03 ⁇ and 04 ⁇ being respectively the distances between the sensors R ⁇ 3 and R x4 from the position of the point T, v a (f) is phase velocity of the Lamb anti-symmetric mode, of order 0, and SU(O is tne Fourier transform of the calculated signal.
  • the residue between the signal S 4 received at the sensor R X 4 and the calculated signal s' 4 is determined, for example by the following equation:
  • S 4n is the discrete Fourier anti-transform of the signal SU(O- S 4 n is the discrete signal received by the sensor R x4 .
  • R d is a parameter which depends on v a.
  • the residue calculation can be likewise performed by representing the frequency domain signals (Parseval theorem).
  • the setting procedure can be repeated several times, a different sensor pair being considered each time.
  • the partial results can then be considered jointly (for example averaged) to increase the precision of the overall estimation of the elastic properties of the panel under examination.
  • a Lamb wave source for example a tactile interaction
  • the signals acquired by the two sensors R X 4 and R x i being S 4 and si, their distances from the elastic source being d 4 ⁇ and di ⁇ respectively.
  • the difference between the distance of the source from the sensor R x4 (d 4 ⁇ ) and the distance of the source from the sensor R x i (dn ) is known as the relative distance of the sensors R x4 and R x i, and is equal to:
  • S4n is the discrete signal received by the sensor R x4 .
  • Rd is a parameter which depends on ⁇ d4i.
  • the residue can be likewise calculated by representing the frequency domain signals (Parseval theorem).
  • ⁇ d4i having the minimum value being chosen.
  • the aforesaid procedure is effected at 1 mm steps to achieve a precision of 1mm.
  • the distances drr are definind as:
  • Ad ' A 4-3> ds 4FT — d h ⁇
  • the direct model is not linear and the solution can be determined with good accuracy using an iterative inversion procedure such as the Tarantola technique for non-linear inverse problems.
  • the following procedure was used to find the solution:
  • a priori model has a mean rrtpr and the covariance matrix CM
  • dobs is the vector of the observed data
  • C d is the covariance matrix of the measurement uncertainties and the modelling errors
  • GK is the Jacobean matrix
  • m* and mj ⁇ +1 are the vectors of the model estimated at the iterations K and K+1.
  • M 2 and 27 is the required solution accuracy.
  • the average number of iterations required to obtain an accurate solution is about four. With four sensors available, the location procedure can be repeated four times, considering a different reference sensor for each of them. The partial results can then be considered jointly (for example, averaged) to increase the accuracy of the overall estimation of the source position.
  • a continuous elastic source on the panel can also be tracked by iteratively applying the previously described inversion technique. From an initial source position (evaluated by the described method or by another, such as the TDOA, as high accuracy is not required for estimating the initial source position) the immediately subsequent position of the source is evaluated by effecting non-linear inversion of the relative distances between the sensors (at least three).
  • the procedure for tracking the continuous elastic source is the following:

Abstract

L'invention concerne un procédé de localisation d'une source élastique située sur un panneau. Le procédé comporte au moins quatre détecteurs de vibration, dont chacun reçoit un signal de vibration généré par la source électrique située sur le panneau et envoie un signal électrique correspondant à un processeur. Le procédé consiste à déterminer les propriétés élastiques du panneau; déterminer la courbe de dispersion correspondante; déterminer les distances relatives (Δdki) entre les quatre détecteurs de vibration ou plus; la position (XT, YT) de la source élastique étant déterminée par la technique itérative de Tarantola pour des problèmes inverses non linéaires.
PCT/IB2008/001104 2007-05-08 2008-05-05 Procédé de localisation et de suivi de sources élastiques dans des supports minces WO2008135846A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
ITBG2007A000028 2007-05-08
ITBG2007A000030 2007-05-08
ITBG20070029 ITBG20070029A1 (it) 2007-05-08 2007-05-08 Metodo per la determinazione delle distanze relative tra sensori vibrazionali posti su un pannello.
ITBG2007A000029 2007-05-08
ITBG20070030 ITBG20070030A1 (it) 2007-05-08 2007-05-08 Metodo per la localizzazione e l'inseguimento di sorgenti elastiche in mezzi sottili.
ITBG20070028 ITBG20070028A1 (it) 2007-05-08 2007-05-08 Metodo per la determinazione delle proprieta' elastiche di un pannello tramite una sorgente elastica e due o piu' sensori vibrazionali.

Publications (1)

Publication Number Publication Date
WO2008135846A1 true WO2008135846A1 (fr) 2008-11-13

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2956554A1 (fr) * 2010-02-17 2011-08-19 Commissariat Energie Atomique Transducteur piezoelectrique, dispositif de transduction piezoelectrique, panneau interactif et levier de commande
TWI621053B (zh) * 2013-03-15 2018-04-11 艾羅觸控解決方案公司 使用觸敏藍姆波之聲波觸控設備及方法
CN113465723A (zh) * 2021-06-07 2021-10-01 湖南北斗微芯数据科技有限公司 一种振动源检测方法、存储介质及振动检测装置、系统

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003005292A1 (fr) * 2001-07-04 2003-01-16 New Transducers Limited Dispositif sensible au contact
US20050146511A1 (en) * 2003-12-31 2005-07-07 Hill Nicholas P. Touch sensitive device employing impulse reconstruction
US20060055403A1 (en) * 2004-04-30 2006-03-16 Schlumberger Technology Corporation Method for determining characteristics of earth formations

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003005292A1 (fr) * 2001-07-04 2003-01-16 New Transducers Limited Dispositif sensible au contact
US20050146511A1 (en) * 2003-12-31 2005-07-07 Hill Nicholas P. Touch sensitive device employing impulse reconstruction
US20060055403A1 (en) * 2004-04-30 2006-03-16 Schlumberger Technology Corporation Method for determining characteristics of earth formations

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
G. DE SANCTIS, D. ROVETTA, A. SARTI, G. SCARPARO, S. TUBARO: "LOCALIZATION OF TACTILE INTERACTIONS THROUGH TDOA ANALYSIS: GEOMETRIC VS. INVERSION-BASED METHOD", 4 September 2006 (2006-09-04) - 8 September 2006 (2006-09-08), European Signal Processing Conference, Florence, Italy, XP002497303, Retrieved from the Internet <URL:http://www.eurasip.org/Proceedings/Eusipco/Eusipco2006/papers/1568982376.pdf> [retrieved on 20080925] *
TARANTOLA, ALBERT: "Inverse Problem Theory and Methods for Model Parameter Estimation", 2005, SOCIETY FOR INDUSTRIAL AND APPLIED MATHEMATICS, PHILADELPHIA, ISBN: 0-89871-572-5, XP002497259, 1 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2956554A1 (fr) * 2010-02-17 2011-08-19 Commissariat Energie Atomique Transducteur piezoelectrique, dispositif de transduction piezoelectrique, panneau interactif et levier de commande
WO2011101569A1 (fr) 2010-02-17 2011-08-25 Commissariat à l'énergie atomique et aux énergies alternatives Panneau interactif comportant des dispositifs de transduction piezoelectrique
CN102762964A (zh) * 2010-02-17 2012-10-31 原子能及能源替代委员会 包括压电换能装置的交互面板
US8513859B2 (en) 2010-02-17 2013-08-20 Commissariat A L'energie Atomique Et Aux Energies Alternatives Interactive panel comprising a substrate and at least two piezoelectric transduction devices
TWI621053B (zh) * 2013-03-15 2018-04-11 艾羅觸控解決方案公司 使用觸敏藍姆波之聲波觸控設備及方法
US10678380B2 (en) 2013-03-15 2020-06-09 Elo Touch Solutions, Inc. Acoustic touch apparatus and method using touch sensitive Lamb waves
CN113465723A (zh) * 2021-06-07 2021-10-01 湖南北斗微芯数据科技有限公司 一种振动源检测方法、存储介质及振动检测装置、系统

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