Method and kinematic calibration system for measuring displacements and vibrations of objects/structures

Patent metadata

Field	Value
Publication number	US-10006988-B2
Application number	US-201514693984-A
Country	US
Kind code	B2
Filing date	Apr 23, 2015
Priority date	Apr 24, 2014
Publication date	Jun 26, 2018
Grant date	Jun 26, 2018

Abstract

A method and system are described for measuring displacements and vibrations of an object/structure. The method includes transmission of at least one radar wave by a single radar device positioned at a predefined distance from a receiver device applied on the object/structure, reception, by the radar device, of a complex signal consisting of the sum of the signal reflected from said receiver device and of one or more interfering signals generated by one or more corresponding targets substantially stationary and substantially positioned at the same distance from the radar device, separation of the interfering signals from the reflected signal. The separation includes calibration by induction, for a pre-determined period of time, of a vibrational motion having a known frequency and duration in the receiver device, which consequently operates as a calibration device, for obtaining an estimated value of the interfering signals.

First claim

The invention claimed is:

1. A method for measuring, at a processor of a radar device (Q), displacements and vibrations of an object/structure (P), the method comprising:
transmitting at least one radar wave by the radar device (Q) placed at a predefined distance (R) from a receiver device on the object/structure (P);
receiving, by the radar device (Q), a complex signal (s(t)) consisting of a sum of a signal reflected from said receiver device and of one or more interfering signals (I) generated by one or more corresponding targets (I 1 , I 2 ) substantially stationary and substantially positioned at the same distance (R) from said radar device (Q); and
separating, at the radar device (Q), the one or more interfering signals (I) from said reflected signal, the separating including calibrating based on
inducting, for a pre-determined period of time, a vibrational motion having a known frequency and duration in the receiver device, which consequently operates as a calibration device, for obtaining an estimated value of said one or more interfering signals (I),
subtracting the estimated value of said one or more interfering signals (I) from the complex signal (s(t)), in order to eliminate said one or more interfering signals (I); and
obtaining an entity of the displacement of the object/structure (P) on the basis of the calibrated reflected signal.

2. The method according to claim 1 , wherein a value of the displacement of the object/structure (P) is calculated on the basis of a variation, as a function of time, of the distance (R LOS (t)) between the radar device (Q) and the object/structure (P).

3. The method according to claim 2 , wherein the distance (R LOS (t)), as a function of time, between the radar device (Q) and the object/structure (P) is equal to:

R
LOS

⁡

(
t
)

=

φ
⁡

(
t
)

4
⁢
π

⁢
λ

wherein φ is the phase of the received signal, after demodulation, and λ is a length of the radar wave.

4. The method according to claim 3 , wherein the phase φ is periodically measured, with repetitions of transmissions, in correspondence with the times t n equal to:

t
n

=

2
⁢
R

c

+
nT

wherein R is the distance of the object/structure (P) from the radar device (Q), c is an electromagnetic propagation rate, T is a repetition period of the radar signal and n is an integer index.

5. The method according to claim 4 , wherein the measurement of the phase φ allows the variation in the distance (R LOS (t)), as a function of time, between the radar device (Q) and the object/structure (P) to be known for multiple time intervals of the repetition period T.

6. The method according to claim 1 , wherein the calibrating is periodically repeated in order to update the estimated value of said one or more interfering signals (I) with respect to possible changes in interference.

7. The method according to claim 6 , wherein estimating a vibration of the object/structure is performed following a temporary interruption of the vibrational motion induced in the receiver or calibration device.

8. The method according to claim 1 , wherein the vibrational motion is a sinusoidal motion.

9. A system for measuring displacements and vibrations of an object/structure (P), the system comprising:
at least one receiver or calibration device on the object/structure (P); and
at least one radar device (Q) positioned at a predefined distance (R) from the at least one receiver or calibration device, the radar device (Q) including a processor configured to
transmit at least one radar wave to said at least one receiver or calibration device,
receive, by the radar device (Q), a complex signal (s(t)) consisting of a sum of a signal reflected from said receiver device and of one or more interfering signals (I) generated by one or more corresponding targets (I 1 , I 2 ) substantially stationary and substantially positioned at the same distance (R) from said radar device (Q), and
separate, at the radar device (Q), the one or more interfering signals (I) from said reflected signal,
wherein preforming the separation, the processor is further configured to
induct, for a pre-determined period of time, a vibrational motion having a known frequency and duration in the receiver device, which consequently operates as a calibration device, for obtaining an estimated value of said one or more interfering signals (I),
subtract the estimated value of said one or more interfering signals (I) from the complex signal (s(t)), in order to eliminate said one or more interfering signals (I), and
obtain an entity of displacement of the object/structure (P) on the basis of the calibrated reflected signal,

wherein said at least one receiver or calibration device comprises
a reflector element visible to the radar device (Q);
an anchor configured to integrally connect said at least one receiver or calibration device with the object/structure (P); and
a vibration mechanism which allows said receiver or calibration device to be moved with its own motion with respect to the object/structure (P).

10. The system according to claim 9 , wherein the vibration mechanism is equipped with an electric motor fed by a battery and with a cam, and is capable of generating a vibrational motion of a sinusoidal type.

Assignees

• Eni Spa

Inventors

• Giunta Giuseppe
• Monti-Guarnieri Andrea

Classifications

• G01S7/354

  Extracting wanted echo-signals (Doppler systems G01S13/50) · CPC title

• G01H9/00

  Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means · CPC title

• G01S7/4052

  by simulation of echoes · CPC title

• G01S13/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01S13/08

  Systems for measuring distance only (indirect measurement G01S13/46) · CPC title