Method for localizing remote devices, using acoustical and electromagnetic waves

• US 8,089,827 B2
• Filed: 11/28/2007
• Issued: 01/03/2012
• Est. Priority Date: 11/30/2006
• Status: Expired due to Fees

• Current Assignee: CAROTENUTO (50% INTEREST), RICCARDO
• Original Assignee: Giuseppe Cardinale Ciccotti, Riccardo Carotenuto
• Inventors: Carotenuto, Riccardo
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): Hulka, James
• Application Number:
  US12/514,847
• Publication Number:
  US 20100061186A1
• Time in Patent Office: 1,497 Days
• Field of Search: 367/118, 367/124, 367126-128, 367/98
• US Class Current: 367/128
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/30 Determining absolute distances from a plurality of spaced points of known location

Abstract

Localization of remote devices by: the emission of pulses from acoustic transmitters, whose wavefronts propagate in the space region occupied by the remote devices and finally reach them; the emission of radiofrequency pulses from each remote device at the time of detection of the wavefront by an on-board microphone; the acquisition, by a radio base, of the radiofrequency signals propagating from the remote devices, to evaluate the arrival time delays proportional to the distance between the i-th acoustic source and the j-th remote device; the formation of a reception vector for each emission by the i-th source, this vector having a maximum length M equal to the number of remote devices and consisting of the sequence of distances obtained as the product of the reception times and the estimated sound velocity. These steps are repeated for all acoustic sources, to form N+1 reception vectors, to calculate the position of the device by solving derived matrix equations.

Claims

1. A method for localization of M remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, through a) the emission of acoustical pulses and b) the emission of radiofrequency pulse from each remote device (3′

, 3″

, . . . 3^M), at the time of detection of said acoustical wave front by its on-board microphone, and c) the acquisition from a radio base (2) unit, of the radiofrequency signals and time delays which are proportional to the distance (d_ij) between the i-th acoustical source (4) and the remote j-th device (3);

comprising;

d—

for each emission from the i-th source, successive insertion of components in a reception vector (D_i), formed by the sequence of distances obtained from the product of the arrival time delays with an estimated sound velocity, said vector,

i—

in the absence of disturbances, having a maximum length M corresponding to the number of remote devices;

ii—

in presence of disturbances of an acoustical or electromagnetic kind, that could erroneously be interpreted as additional reception signals, being “

oversized”

according to the noise/disturbances, the number of evaluations being increased up to L₁·

L₂·

. . . L_N+1, with L_i>

M;

e—

repetition of the steps a, b, c, d for all N+1 acoustical sources, in order to form N+1 reception vectors;

f—

the calculation of the position X_j=(x_1j, x_2j, . . . x_Nj) of the j-th remote device, starting from the N+1 distances d_1j, d_2j, . . . d_N+1j, as the intersection point of N+1 spheres of radius d_ij centred at the positions (x_Si, y_Si, z_Si, where I=1, 2, . . . N+1), of the N+1 acoustical sources.

2. The method for localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within a 3-dimensional system according to claim 1, wherein after putting x_ij=x_j, x_2j=y_j, x_3j=z_j, one follows the following steps of matrix calculus;

a—

subtraction of the first equation from the other equations, in the system

3. The method for localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, according to claim 1, wherein an a priori distinction for each remote device j, of the N+1-ple (d_1j, d_2j, . . . d_N+1j) within the reception vectors (D₁, D₂, . . . D_N+1), occurs according to a search procedure that selects the possible candidates (d_1j, d_2j, . . . d_N+1j,) within the reception vectors (D₁, D₂, . . . D_N+1), in order to calculate the vector X_j by the equation X_j=A<sup>−

1</sup>B_j (4), said vector X_j being considered in equation (1) an admissible solution of the localization problem, provided that the obtained residue is zero, or less than a predetermined threshold taking account of the total noise affecting the calculation as a whole.

4. The method for localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, according to claim 1, wherein, in case the sources lie within a sphere of radius r_max so that the elements of each N+1-ple (d_1j, d_2j, . . . d_N+1j) do not differ from each other by more than 2r_max, the reduction of the computational work is obtained by a process comprising the following steps;

i—

extracting the first element from one of the vectors D_i;

ii—

extracting from the remaining vectors D_i, all elements that differ at most by 2r_max, and which therefore are possible candidates, the number of these elements slightly exceeding N+1 for reasonable choices of r_max;

iii—

calculating all combinations of the extracted elements, without exchanging the elements of different vectors, these combinations being used for calculating a set of X_j from equation (4);

iv.a—

if, via equation (4) one of said combinations gives a null or sufficiently small residue in equation (1), acquiring the first extracted element as a valid reception signal, and memorising the just obtained coordinate of the remote device while eliminating, from the respective vectors D_i, the N+1 elements which produce the vector X_j solution of equation (1);

iv.b—

if, none of the above combinations provides a valid result, invalidating the first element extracted from the vector, which represents a disturbance to be eliminated from that vector;

v—

after both of the above cases iv.a and iv.b, selecting again the first element of D_i and iterating the steps i, ii, iii, iv, until the elements of the vector are exhausted.

5. The method for localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, according to claim 1,

wherein all acoustic sources, tuned according to a single pulse emitting source, simultaneously emit their pulses which are possibly indistinguishable from each other in their signal behaviour, thereby using a single frequency of pulse repetition and establishing a wait regime bound to a single propagation time for the acoustical wavefronts in the space region of interest.

6. The method for localization of remote devices by their coordinates within an N-dimensional system, according to claim 4, wherein when using only one reception vector (D) for the search of the elements belonging to the j-th N+1-ple, one also takes account of the exchange of position within the N+1-ple, of the elements extracted from the vector D, in order to employ a procedure involving N+1 vectors D_i identical to each other, each one being a copy of the unique available vector D, the procedure comprising the following steps:

i—

extracting the first element from one of the vectors D_i;

ii—

extracting from the remaining vectors D_i all elements differing from each other at most by 2r_max and which therefore are possible candidates, the number of such elements slightly exceeding N+1 for reasonable choices of r_max;

iii—

calculation of all combinations of extracted elements without exchanging elements belonging to different vectors, these combinations being used for

calculating a set of X_j from equation (4);

iv.a—

if, in equation (1) one of these combinations, based on equation (4), produces a null or sufficiently small residue, the step of acquiring the first extracted element as valid reception signal, and thereafter the step of storing the just obtained coordinate of the remote device while eliminating from the respective vectors D_i the N+1 elements which produce the vector X_j solution of equation (1);

iv.b—

otherwise, if none of the above combinations provides a valid result, the step of invalidating the first element extracted from the vector, which represents a disturbance to be eliminated from that vector;

v—

after both of the above cases iv.a and iv.b, selecting again the first element of D_i and iterating the steps i, ii, iii, iv, until the elements of the vector are exhausted.

7. The method for localization of remote devices by their coordinates within an N-dimensional system, according to claim 1, wherein optimising the accuracy of the localization through the evaluation from time to time of the sound velocity along the (average) path from the sources to the single remote device, this being achieved by modifying equation (2) as follows:

8. An apparatus for the localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, comprising;

I—

a microphone that operates in an acoustical band of interest, used to detect a behaviour of the acoustical pressure field in a neighborhood of the microphone sensor and the arrival of emitted wavefronts;

II—

a signal processing circuit including an impedance adaptation circuit, an amplifier, an off-band noise rejection filter;

III—

a signal recognition circuit, used to identify the effective signal among all received sounds and including a threshold detecting circuit, or a circuit effecting a comparison through the cross-correlation with a sample signal, a circuit for estimating statistical indicators, neural networks, etc;

IV—

a RF transmitter with an adequate band, used to communicate the already occurred reception to a radio base unit;

V—

a controller, which manages the reception of the acoustic signal, the signal processing, and the transmission of the already occurred reception,

wherein a) an emission of acoustical pulses and b) the emission of radiofrequency pulse from each remote device (3′

, 3″

, . . . 3^M), at the time of detection of said acoustical wave front by the on-board microphone, and c) the acquisition from the radio base (2) unit, of the radiofrequency signals and time delays which are proportional to the distance (d_ij) between the i-th acoustical source (4) and the remote j-th device (3);

comprising;

d—

for each emission from the i-th source, successive insertion of components in a reception vector (D_i), formed by the sequence of distances obtained from the product of the arrival time delays with an estimated sound velocity, said vector,

i—

in the absence of disturbances, having a maximum length M corresponding to the number of remote devices;

ii—

in presence of disturbances of an acoustical or electromagnetic kind, that could erroneously be interpreted as additional reception signals, being “

oversized”

according to the noise/disturbances, the number of evaluations being increased up to L₁·

L₂·

. . . L_N+1, with L_i>

M;

e—

repetition of the steps a, b, c, d for all N+1 acoustical sources, in order to form N+1 reception vectors;

f—

the calculation of the position X_j=(x_1j, x_2j, . . . x_Nj) of the j-th remote device, starting from the N+1 distances d_1j, d_2j, . . . d_N+1j, as the intersection point of N+1 spheres of radius d_ij centred at the positions (x_Si, y_Si, z_Si, where I=1, 2, . . . N+1), of the N+1 acoustical sources.

9. An for the localization of remote devices (3′

, 3″

, . . . 3^M) by their coordinates within an N-dimensional system, comprising a radio base (2) that includes at least the following components;

a—

N+1 transmitters of acoustical pulses or ultrasound pulses, whose band is selected according to the localization accuracy requirements, to the maximum distance of the remote devices from the emitters, and to the noiselessness of the operations, wherein the position of the transmitters within the reference system is known in advance with a sufficient degree of accuracy;

b—

a radiofrequency receiver (2), suited to detect signals related to the positions of on board sensors and to the readings of on-board sensors emitted by the individual remote devices;

c—

a calculation system for computing the positions of the remote devices, starting from the difference between the acoustic pulse emission times and the reception time delays of the radiofrequency signal;

d—

an algorithm, carried out by the calculation system of the radio base, which is based on a matrix formulation of the position determination problem and is suited to determine the position of the remote devices within the given reference frame,

wherein a) an emission of acoustical pulses and b) the emission of a radiofrequency pulse from each remote device (3′

, 3″

, . . . 3^M), at the time of detection of said acoustical wave front by the on-board microphone, and c) the acquisition from the radio base (2) unit, of the radiofrequency signals and time delays which are proportional to the distance (d_ij) between the i-th acoustical source (4) and the remote j-th device (3);

comprising;

d—

for each emission from the i-th source, successive insertion of components in a reception vector (D_i), formed by the sequence of distances obtained from the product of the arrival time delays with an estimated sound velocity, said vector,

i—

in the absence of disturbances, having a maximum length M corresponding to the number of remote devices;

ii—

in presence of disturbances of an acoustical or electromagnetic kind, that could erroneously be interpreted as additional reception signals, being “

oversized”

according to the noise/disturbances, the number of evaluations being increased up to L₁·

L₂·

. . . L_N+1, with L_i>

M;

e—

repetition of the steps a, b, c, d for all N+1 acoustical sources, in order to form N+1 reception vectors;

f—

the calculation of the position X_j=(x_1j, x_2j, . . . x_Nj) of the j-th remote device, starting from the N+1 distances d_1j, d_2j, . . . d_N+1j, as the intersection point of N+1 spheres of radius d_ij centred at the positions (x_Si, y_Si, z_Si, where I=1, 2, . . . N+1), of the N+1 acoustical sources.