Method for locating an impact on a surface and device for implementing such a method

• US 7,649,807 B2
• Filed: 08/10/2005
• Issued: 01/19/2010
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Sensitive Object
• Inventors: Ing, Ros Kiri
• Primary Examiner(s): PIHULIC, DANIEL T
• Application Number:
  US11/573,513
• Publication Number:
  US 20090116339A1
• Time in Patent Office: 1,623 Days
• Field of Search: 367/118, 367/125, 345/156, 345/157, 345/158, 345/173, 345/177
• US Class Current: 367/118
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

Method for locating an impact on a surface (9), in which acoustic sensors (6) pick up acoustic signals s_ki (t) generated by the impact and the impact is located by calculating, for a number of reference points of index j, a validation parameter representative of a function: PROD_kjⁱ₁ⁱ₂^{. . . i}_2P(ω)=φS_ki1(ω) φR_ji1(ω)*φS_ki2(ω)*φR_ji2(ω) . . . φS_ki2p(ω)*φR_ji2p(ω) where: φS_ki(ω) and φR_ji(ω)* are complex phases of S_ki(ω) and of R_ji(ω), for i=i₁, i₂, . . . , i_2p, indices denoting sensors, S_ki(ω) and R_ji(ω) being the Fourier transform of s_ki(t) and r_ji(t), r_ji(t) being a reference signal corresponding to the sensor i for an impact at the reference point j, p being a non-zero integer no greater than N_SENS/2.

Claims

1. Method for locating an impact on a surface belonging to an object provided with at least N_SENS acoustic sensors, N_SENS being a natural integer at least equal to 2, said method being implemented by a central processing unit linked to said acoustic sensors and in which method:

the sensors are made to pick up respectively N_SENS signals S_ki(t) from acoustic waves generated in the object by said impact,

i being an index between 1 and N_SENS which denotes the corresponding sensor, where k is the area where the impact occurred

there is calculated, for each reference point of index j, at least one validation parameter representative of at least one intercorrelation of complex phases representative of said picked up signals S_ki(t) and of reference signals r_ji(t), each reference signal r_ji(t) corresponding to the signal that would be received by the sensor i in case of impact at a reference point j out of N_REF reference points belonging to said surface, N_REF being a natural integer at least equal to 1 and j being an index between 1 and N_REF, and

the impact is located by determining at least one reference point as close as possible to the point of impact, by applying at least one validation criterion to the validation parameter, characterized in that said validation parameter is representative of at least one intercorrelation;

PROD_kjⁱ₁ⁱ₂ⁱ_2p(ω

)=φ

S_ki1(ω

)φ

R_ji1(ω

)*φ

S_ki2(ω

)*φ

R_ji2(ω

) . . . φ

S_ki2p(ω

)*φ

R_ji2p(ω

)

where;

φ

S_ki(ω

) is the complex phase of S_ki(ω

), for i=i₁, i₂, . . . , i_2p

φ

R_ji(ω

) is the complex phase of R_ji(ω

), for i=i₁, i₂, . . . , i_2p

* denotes the conjugate operator, applied to φ

S_ki(ω

) for i=i_2m and to φ

R_ji(ω

) for i=i_2m-1, m being an integer between 1 and p;

S_ki(ω

) is the Fourier transform of S_ki(t),

R_ji(ω

) is the Fourier transform of r_ji(t),

p is a non-zero natural integer less than or equal to N_SENS/2,

i₁, i₂, . . . i_2p are 2p indices denoting 2p sensors, each between 1 and N_SENS.

2. Method according to claim 1, in which the reference signals are predetermined theoretically.

3. Method according to claim 2, in which the reference signals are used with said object without training phase.

4. Method according to claim 1, wherein the reference signals are previously learned on a reference device identical to said object, then are used with said object without training phase.

5. Method according to claim 1, including a step for calculating the intercorrelation PROD_kjⁱ₁ⁱ₂ⁱ_2p(ω

), then a step for the inverse Fourier transform of this intercorrelation to obtain a time function prod_kjⁱ₁ⁱ₂ⁱ_2p(t), from which said validation parameter is then calculated.

6. Method according to claim 5, in which the intercorrelation PROD_kjⁱ₁ⁱ₂ⁱ_2p(ω

) is standardized before proceeding with the inverse Fourier transform.

7. Method according to claim 5, in which, for each reference point j, a resemblance function V_kj(t) is calculated, chosen from:

prod_kjⁱ₁ⁱ₂ⁱ₂p(t), and

a linear combination of a number of functions prod_kjⁱ₁ⁱ₂ⁱ_2p(t) corresponding to a number of subsets of 2p sensors out of N_SENS.

8. Method according to claim 7, in which N_SENS is an even number and V_kj(t) is proportional to prod_kjⁱ₁ⁱ₂ⁱ_2p(t), where p=N_SENS/2.

9. Method according to claim 8, in which N_SENS=2 and V_kj(t) is proportional to prod_kj¹²(t).

10. Method according to claim 7, in which N_SENS=3 and, for each reference point j, a resemblance function V_kj(t) is calculated, chosen from:

−

V_kj(t)=a3·

[prod_kj¹²(t)+prod_kj²³(t)], and

V_kj(t)=b3·

{prod_kj¹²(t)+prod_kj²³(t)+prod_kj¹³(t)}, a3 and b3 being constants.

11. Method according to claim 10, in which a3=½

and b3=⅓

.

12. Method according to claim 7, in which N_SENS=4 and, for each reference point j, a resemblance function V_kj(t) is calculated, chosen from:

V_kj(t)=a4·

prod_kj¹²³⁴(t),

V_kj(t)=b4·

[prod_kj¹²(t)+prod_kj³⁴(t)],

V_kj(t)=c4·

[prod_kj¹²(t)+prod_kj²³(t)+prod_kj³⁴(t)+prod_kj¹⁴(t)],

a4, b4 and c4 being constants.

13. Method according to claim 12, in which a4=1, b4=½

and c4=¼

.

14. Method according claim 7, in which the validation parameter is chosen from:

15. Method according to claim 14, in which only V_kj(t) is calculated for the time t=0 roughly corresponding to the impact, as being the real part of PROD_kjⁱ₁ⁱ₂ⁱ_2p(ω

), and MAXIMUM_0j is used as validation parameter.

16. Method according to claim 14, in which at least one validation criterion is used, chosen from the following criteria:

CONTRAST_1j>

THRESHOLD₁, with THRESHOLD₁>

1,

CONTRAST_1j>

THRESHOLD₁ and

MAXIMUM_0j/MAXIMUM_ij^NOISE>

THRESHOLD₂, where

THRESHOLD₂>

1 and MAXIMUM_1j^NOISE corresponds to the parameter MAXIMUM_1J of the signals processed previously and not having resulted in validation,

MAXIMUM_0j>

THRESHOLD₃, with THRESHOLD₃>

0 and

MAXIMUM_0j/MAXIMUM_0j^NOISE>

THRESHOLD₄ with THRESHOLD₄>

1, where MAXIMUM_0j^NOISE corresponds to the parameter MAXIMUM_0j of the signals processed previously and not having resulted in validation,

MAXIMUM_0j/Average (MAXIMUM_0j^NOISE)>

THRESHOLD₅, with THRESHOLD₅>

1,

ENERGY/ENERGY^NOISE>

THRESHOLD₆, where THRESHOLD₆>

1 and ENERGY^NOISE corresponds to the parameter ENERGY of the signals processed previously and not having resulted in validation.

17. Device specially adapted to implement a method according to claim 1, this device comprising:

an object provided with at least N_SENS acoustic sensors, N_SENS being a natural integer at least equal to 2, to pick up respectively N_SENS signals s_ki(t) from acoustic waves generated in the object by an impact on a surface belonging to said object, i being an index between 1 and N_SENS which denotes the corresponding sensor,

a central processing unit linked to said acoustic sensors and able to

calculate, for each reference point of index j, at least one validation parameter representative of at least one intercorrelation of complex phases representative of said picked up signals S_ki(t) and of reference signals r_ji(t), each reference signal r_ji(t) corresponding to the signal that would be received by the sensor i in case of impact at a reference point j out of N_REF reference points belonging to said surface, N_REF being a natural integer at least equal to 1 and j being an index between 1 and N_REF, and

locate the impact by determining at least one reference point as close as possible to the point of impact, by applying at least one validation criterion to the validation parameter, characterized in that said validation parameter is representative of at least one intercorrelation;

PROD_kjⁱ₁ⁱ₂ⁱ_2p(ω

)=φ

S_ki1(ω

)φ

R_ji1(ω

)*φ

S_ki2(ω

)*φ

R_ji2(ω

) . . . φ

S_ki2p(ω

)*φ

R_ji2p(ω

)

where;

φ

S_ki(ω

) is the complex phase of S_ki(ω

), for i=i₁, i₂, . . . , i_2p,

φ

R_ji(ω

) is the complex phase of R_ji(ω

), for i=i₁, i₂, . . . , i_2p,

* denotes the conjugate operator, applied to φ

S_ki(ω

) for i=i_2m and to φ

R_ji(ω

) for i=i_2m-1, m being an integer between 1 and p;

S_ki(ω

) is the Fourier transform of S_ki(t),

R_ji(ω

) is the Fourier transform of r_ji(t),

p is a non-zero natural integer less than or equal to N_SENS/2,

i₁, i₂, . . . i_2p are 2p indices denoting 2p sensors, each between 1 and N_SENS.