Hybrid sensor head for surface inspection and method of use
A hybrid sensor head ( 12 ) for inspecting a surface includes a casing ( 28 ) supporting at least one pair of pulse transceivers emitting respective pulses through a medium at different propagation speeds toward the surface and for receiving therefrom respective reflected pulses. The transceivers ( 50, 57 ) in each pair are configured to emit respective pulses to a common location of the surface and are mutually displaced such that a respective round-trip propagation distance for each pair of pulses differs by a known amount. At least two measurements are obtained from each pair of sensors at different times allowing computation of range and velocity for each transceiver.
1. A hybrid sensor head for determining range or propagation speed of a pulse from a sensor to a surface through an intervening medium without requiring knowledge of material properties of the medium, the sensor head comprising:
a casing supporting at least one pair of pulse transceivers, each transceiver having a respective first sensor (A) and second sensor (B) for respectively emitting pulses through the medium at respective propagation speeds v A and v B toward said surface and for receiving therefrom respective reflected pulses, the respective transceiver in each pair being configured to emit pulses to a common location of the surface and being mutually displaced by a known offset (h) measured in a direction of propagation of said pulses,
at least one motor configured to rotate the transceivers about a common axis of rotation during propagation of the transceivers along the surface so as to direct said pulses radially to the axis of rotation to successive points along the surface,
at least one positioning sensor for determining an instantaneous location in space of the respective transceiver in each pair,
at least one processor coupled to the at least one positioning sensor, and to the respective transceivers in each pair, the at least one processor being configured to:
(a) control the transceivers in each pair to direct pulses toward successive points along the surface and receive therefrom respective reflected pulses; and
(b) measure respective propagation times for at least two pulses from each transceiver to travel to the surface and back to the respective transceiver;
characterized in that:
the at least one processor is configured to:
(c) use respective propagation times of the at least two pulses from each transceiver directed to a respective common location of the surface at different times to compute either or both of:
i) a range traversed by each pulse, as follows:
r
A
1
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
(
t
A
1
t
B
2
-
t
A
1
t
B
1
)
h
r
B
1
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
(
t
A
2
t
B
2
-
t
A
1
t
B
1
)
h
ii) a respective propagation speed of each pulse through the medium as follows:
v
A
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
2
(
t
B
2
-
t
B
1
)
h
v
B
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
2
(
t
A
2
-
t
A
1
)
h
where:
r A1 and r A2 are the ranges for sensor A at sampling times 1 and 2 , respectively;
r B1 and r B2 are the corresponding ranges for sensor B;
t A1 , t A2 t B1 , and t B2 are the round-trip travel times for the pulses from the respective sensors at the respective times; and
the two ranges and respective round trip propagation times measured by each sensor are different, i.e., r A1 ≠r A2 and r B1 ≠r B2 and t A1 ≠t A2 and t B1 ≠t B2 .
2. The sensor according to claim 1 , wherein each pair of pulse transceivers includes an ultrasonic transceiver and an impulse radar transceiver.
3. The sensor according to claim 1 , where the at least one processor is further configured to:
(d) correlate the propagation velocity for each pulse with respective functions relating material properties of the medium to the velocity to determine which material property best fits the measured propagation velocity.
4. The sensor according to claim 3 , where the at least one processor is further configured to:
(e) detect surface defects based on deviations in measured material properties of the medium as the sensor head is moved relative to the surface; and
(f) identify a location of said defects based on an associated measurement from the positioning sensor.
5. The sensor head according to claim 1 , further including at least one coupler at an end of the sensor head for coupling the sensor head to a robot.
6. The sensor head according to claim 4 , wherein the coupler is configured to feed electric power and control signals to components in the sensor head.
7. The sensor head according to claim 5 , wherein the coupler is configured for retrofitting to an off-the-shelf robot either directly or via a suitable adapter.
8. The sensor head according to claim 1 , including a camera supported by a central rod at a forward end of the sensor head.
9. The sensor head according to claim 8 , wherein the at least one motor inside the casing is configured to rotate the casing around the rod while maintaining the rod rotationally stationary.
10. The sensor head according to claim 7 , wherein the at least one microcontroller is programmed to rotate the at least one motor at a speed that varies in accordance with an advance speed of the sensor head through the pipeline in order to ensure that the ultrasonic and RF signals scan a complete inner circumference of the pipeline as the sensor head progresses along the pipeline.
11. A pipeline inspection system comprising a robot coupled via coupler to the sensor head according to claim 1 .
12. The pipeline inspection system according to claim 11 , wherein the coupler is configured to feed electric power and control signals from the robot to components in the sensor head.
13. The pipeline inspection system according to claim 11 , being configured to rotate the sensor head at a speed that varies in accordance with an advance speed of the robot through a pipeline in order to ensure that the ultrasonic and RF signals scan a complete inner circumference of the pipeline as the sensor head progresses along the pipeline.
14. A computer program product comprising a non-transitory computer-readable memory storing program code instructions, which when run on a computer processor are responsive to data relating to measurements of respective propagation times of at least two pulses from each of a pair of transceivers, respective pulses from each transceiver being directed to a respective common location of a surface through an intervening medium, said program code instructions being configured to use respective propagation times of the at least two pulses from each transceiver to compute either or both of:
i) a range traversed by each pulse, as follows:
r
A
1
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
(
t
A
1
t
B
2
-
t
A
1
t
B
1
)
h
r
B
1
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
(
t
A
2
t
B
2
-
t
A
1
t
B
1
)
h
ii) a respective propagation speed of each pulse through the medium as follows:
v
A
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
2
(
t
B
2
-
t
B
1
)
h
v
B
=
1
t
A
1
t
B
2
-
t
A
2
t
B
1
2
(
t
A
2
-
t
A
1
)
h
where:
h is a known offset between the respective transceivers in each pair as measured in a direction of propagation of said pulses;
r A1 and r A2 are the ranges for sensor A at sampling times 1 and 2 , respectively;
r B1 and r B2 are the corresponding ranges for sensor B;
t A1 , t A2 t B1 , and t B2 are the round-trip travel times for the pulses from the respective sensors at the respective times; and
the two ranges and respective round trip propagation times measured by each sensor are different, i.e., r A1 ≠r A2 and r B1 ≠r B2 and t A1 ≠t A2 and t B1 ≠t B2 .