Communications – electrical: acoustic wave systems and devices – Testing – monitoring – or calibrating
Patent
1989-07-07
1991-08-13
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Testing, monitoring, or calibrating
25022724, 356 32, 73800, 385147, G01L 124, G02B 616
Patent
active
050401548
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to monitoring and measuring techniques, and, more particularly, it relates to methods of monitoring the state of an extended shell.
Extended shells monitored in accordance with the invention can be roofs of permanent structures, casings of machines, vehicles, aircraft and ships, the surfaces of dams of hydroelectric projects, the reflectors of aerials and radio telescopes, the faces and surfaces of mine workings, implantable artificial human organs.
BACKGROUND ART
There is known a method of monitoring the state of an extended cylindrical shell, e.g. a marine riser in offshore drilling (ARG-Telefunken, BRD. "Position Measuring System for Offshore Installations. System design and mathematical description", 1980, 10 pp.).
The known method includes the steps of selecting a sensitive element resposive to variation of the monitored parameter, e.g. the geometry of the surface of an extended shell, representative of the state of this shell, providing an extended line of transmission of wave energy carrying information on variation of the monitored parameter, matching the selected responsive element and extended line of transmission of wave energy, positioning the matched responsive element and extended line of transmission of wave energy in the zone of monitoring lengthwise of a specified running coordinate along which the monitored parameter is expected to vary, shaping and feeding to the input of the extended line of transmission of wave energy a time-modulated reference signal transformable in its propagation along this line in accordance with the variation of the monitored parameter representative of the state of the extended shell, measuring the parameters of the transformed reference signal at the output of the extended line of transmission of wave energy, and employing the measured parameters of the transformed reference signal for determining the mechanical characteristics of the state of the extended shell along the specified coordinate along which the monitored parameter varies. These basic steps of the method of AEG-Telefunken are specifically implemented, as follows.
In this known method, the monitores parameters representative of the state of an extended shell--a marine riser--are the angle of deviation of the axis of the marine riser from a vertical line and twist angles in the horizontal plane of the uppermost and lowermost parts of the riser. Hence, the selection of responsive elements is carried out by providing special-design sensors responding to variations of the above angles, i.e. inertia-type inclinometers and magnetic compasses. Then the extended line of transmission of wave energy is provided in the form of a shielded electric cable with a polyethylene protective sheath. The matching of the selected sensors and cable is effected by providing inductive coupling therebetween. The matched sensors and cable are secured on the surface of a marine riser lengthwise of its axis. To obtain sufficient data on the geometry of the longitudinal axis in the three-dimensional space, the sensors of deviation of the axis from the vertical line are arranged and secured along two orthogonal generatrices on the surface of the marine riser. Then the reference electric signal time-varying at a 400 Hz frequency is fed to the input of the cable. While propagating along the cable, the reference signal supplies the sensors with power through their inductive coupling and collects from them the information on the angles, but at a frequency substantially higher than the carrier frequency of 400 Hz. The parameters of the transformed reference electric signal are measured at the output of the cable, the information thus obtained is decoded, and the data on the angles of twist and deviation of the longitudinal axis of the riser from the vertical line are employed for determining the mechanical or physical characteristics of the state of the riser. The characteristics thus obtained define unambiguously the strained/deformed state of the marine riser and the relative positio
REFERENCES:
patent: 4459022 (1984-07-01), Morey
patent: 4654520 (1987-03-01), Griffiths
patent: 4927232 (1990-05-01), Griffiths
Elshansky Petr V.
Mikheev Sergei M.
Zemerov Valery N.
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