WO/2005/060462 | VEHICLE COLLISION DAMAGE DISPLAY TECHNIQUE |
JPS57175905 | DEVICE FOR DETECTING SWINGING ANGLE OF SUSPENDING TOOL |
OPTOSENSING SRL (IT)
HPSYSTEM IT SRL (IT)
CLAIMS 1. A clinometric optical fiber sensor, comprising a plastic tube (3) and at least three optical fibers (53), said three optical fibers (53) being arranged along the longitudinal axis of the tube (3) in an equidistant arrangement one from the other, characterized in that: - A fourth fiber (53) it is inserted in the tube wall (3) but installed so as not to transmit deformations, and intended for the measurement of the temperature profile; and - a series of clinometric sensors (30) of the digital biaxial type it is arranged inside the tube (3) , each of said series of clinometric digital sensors being arranged at equally spaced intervals one with respect to the other, and said inclination sensors being equipped with electronic compass . 2. An apparatus (1) for the making of a clinometric optical fiber sensor which comprises a tube (3) of plastic material and optical fibers (53), characterized by comprising: - A main frame (10) supporting a continuously feeding unit (2) of a continuous tube (3) ; - A forming station (4), wherein during the feeding of the tube (3) are continuously performed at least three longitudinal grooves on the surface of said tube (3) and for the entire length of said tube (3) ; - A robotic station (5) for continuously applying at least three optical fibers (53) onto said surface of said tube (3), each fiber (53) being inserted in a respective groove during the feeding of the tube (3) ; - A sealing station (6) for sealing and / or fastening the optical fibers (53) inside of the respective grooves formed onto the surface of said tube (3) ; and - A second feeding station (7) for the feeding of said tube (3) so assembled. 3. The apparatus (1) for the making of a clinometric optical fiber sensor according to the preceding claim, wherein said grooves are obtained by mechanical removal or, alternatively, by thermal etching. 4. The apparatus (1) for the making of a clinometric optical fiber sensor according to claim 2 or 3, wherein the robotic station (5) comprises: - At least three coils (50), each coil (50) containing an optical fiber wound on it; - Conveying ducts for conveying each fiber (53) in a respective groove formed onto the surface of the tube (3); - A guide member (51) for the guiding of said optical fibers (53), the guide member (51) being arranged at the front of the fiber port from the respective coils (50), the guide member (51) having conical ports (52), each conical port (52) being associated with a respective conveying duct of a respective optical fiber (53) . 5. The apparatus (1) for the making of a clinometric optical fiber sensor according to claim 2 or 3 or 4, wherein said sealing station (6) performs a sealing of the grooves containing the optical fibers (53) by melting the material of the tube (3) or, alternatively, by means of epoxy resins. 6 . The apparatus (1) for the making of a clinometric optical fiber sensor according to any of the preceding claims 2-5, further comprising a verification system for the verification of the continuity of the optical fibers (53) during all the production steps, said verification system comprising: - A detection circuit inserted in each coil (50) and being connected to the respective fiber (53) wound on it; - A control unit or PLC (8) for the detection of alarm coming from said detection circuit in the case where failure is detected on the fiber (53) to which it is associated; - A laser emitter (9) connected at the free end of the fibers ( 53 ) ; the arrangement being such that the circuits contained inside of the coils (50) are connected to respective end parts of the fibers (53) to be installed, and detect the presence of the laser beam transmitted by the laser emitter (9) connected to the accessible free ends of the fibers (53), wherein if a fiber (53) it is interrupted the circuit detects the absence of the signal coming from the laser source (9) and transmits an alarm to the PLC control unit (8), which activates an audible alarm and indicates which of the fibers (53) it is interrupted. 7. A process for the making of an optical fiber clinometric sensor comprising a plastic tube (3) incorporating optical fiber sensors, characterized by the following steps: - providing a pipe (3) made of a plastic material; - continuously carry on at least three longitudinal grooves on the surface of said tube (3) and throughout the whole length of said tube (3) ; - positioning with a controlled tension at least three optical fibers (53) each into a respective groove along said tube (3) ; and sealing said grooves containing each an optical fibers ( 53 ) . 8. The process for the making of a optical fiber clinometric sensor according to the preceding claim, wherein said grooves are obtained by mechanical removal. 9. The process for the making of an optical fiber clinometric sensor according to claim 7, wherein said grooves are obtained by thermal engraving. 10. The method for the making of an optical fiber clinometric sensor according to any one of the preceding claims 7 to 9, wherein said tube (3) is made of PE . 11. The process for the making of an optical fiber clinometric sensor according to any of the preceding claims 7 to 10, wherein said sealing step of said grooves is performed by plastic fusion. 12. The process for the making of an optical fiber clinometric sensor according to any of the preceding claims 7 to 10, wherein said sealing step of said grooves performed by epoxy resins. |
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DESCRIPTION
The present invention relates to a clinometric tube optical fiber sensor type to be applied to the measurement of displacement of sloping fields.
The present invention also relates to the process for the making of such a clinometric sensor.
Prior art
As it is already known in the art, a probe clinometer (or clinometric probe) comprises a biaxial inclination sensor (i.e., potentiometric sensor, servo-accelerometric sensor, MEMS) assembled within a grooved tubular structure and provided of rolling supports, and such that the sensor is capable of sliding move inside the grooved tube (i.e. the so-called "clinometric tube"), the tube being previously cemented to a survey hole.
For the operation thereof, the sensor it is inserted into the clinometric tube and the measurement of a and β angles which are orthogonal one to each other (i.e., the angles formed by the axis of the probe relative to the vertical / axial direction of the tube) is carried on at established time intervals.
In this way and by a subsequent processing, both the local displacement at different highs where the measurement has been carried on, and the overall displacement of the field plan with respect to the bottom of the hole are determined .
According to another alternative application, it is possible to perform a "chain" series of clinometric measurements, i.e. measuring realized with a series of sensors positioned at predetermined space intervals.
Recently, optical fiber sensors have been used, which use the Brillouin principle for deformation measurements and are distributed along three or four parallel axes with respect to the vertical axis of the tube. All the above solutions still have some disadvantages. A first disadvantage is that traditional sensors when used in a manual mode, have limitations due both to the measurement accuracy and to the possibility of continuing to perform measurements if the tube deformation no longer allows the passage of the probe. Alternatively, sensor chains are produced, but this solution has very high costs and moreover the sensors can no longer be retrieved if the clinometric tube deformation exceeds certain thresholds.
On the other hand, optical fiber sensors are known to have gained in recent years an important role in various fields of application, such as in the field of structural monitoring or in the field of environmental monitoring (as described, for example, by J Dakin and B. Culshaw in "Optical Fiber Sensors", Artech House, Boston, 1997) . This success is largely due to the ability of these sensors to measure the physical magnitude of interest (temperature and / or deformation), with continuity and long distances. Further advantages lie in low cost and immunity to the electromagnetic interference of the optical fiber used as a sensitive item to the magnitude of interest.
According to this alternative construction of optical fiber clinometers, four optical fibers are applied on the outer wall of the clinometric tube. In this way, the deformations of the tube along four axes, coplanar and parallel to the vertical axis of the inclinometer tube can be measured. According to this alternative constructive embodiment, the mathematical reconstruction method uses the "Beam Theory according to Euler-Bernoulli" and involves the integration of the components of the bending moments, Mx(z) and My(z) (respectively, along the axis X and component along the y-axis in the general z-section) , whose modules are a function of the stress, as well as the Young module associated with the material in which the pipe is made, and the moment of inertia of the tube itself (which in turn depends on geometry) .
The limit of this system lies in the propagation of the error that increases from the initial reference point (bottom of the hole) .
Moreover, another disadvantage is that the installation of the optical fibers along the inclinometers is performed manually. This requires a great deal of effort, both in terms of the specialization profile of the operators and in the timing of laying the fibers on the pipes .
In addition, the manual installation of the fibers is subject to angular positioning errors of the fibers, which impede the quality of the displacement data obtained from deformation readings.
It is therefore the object of the present invention to solve the aforementioned disadvantages by providing a systematic process for the production of clinometers in which the automatic positioning of optical fiber sensors it is realized along a clinometric tube and wherein high precision, reliability and repeatability are guaranteed.
Another object of the present invention it is to provide an apparatus which is capable of carrying out the above process automatically.
A further object of the present invention it is to provide a clinometric sensor obtained according to the present process and apparatus.
Brief Description of the Invention
The present invention provides a process and an apparatus for the making of an integrated optical fiber- MEMS sensor, comprising the following steps:
- providing a PE tube;
- continuously performing four longitudinal grooves onto the surface of said PE tube and along the whole length of said tube, said grooves being obtained by mechanical removal or, alternatively, by thermal engraving,
- positioning four optical fiber with a controlled strain each in a respective groove along said PE pipe; and
- sealing said grooves containing said optical fibers by fusion of PE or, alternatively, by epoxy resins. By the present process and apparatus, clinometric tubes are obtained having a number of advantages with respect to the clinometric tubes of the state of the art.
A first advantage is given by the fact it can be provided a clinometric PE tube of any length and diameter, and which has four optical fibers integrally, three of which are dedicated to deformation measurements, while the fourth fiber it is dedicated to measuring the temperature profile .
Another advantage is that due to the performing of strain and displacement measurements with a high spatial resolution (up to 2 cm) , meaning that it is possible to make measurements every two centimetres along the axis of the tube .
A further advantage lies in that it is possible to provide PE clinometers wherein at the inner thereof be provided a chain of sensors to be used for the error correction due to the integration of bending moments.
Therefore, the present invention provides a process and an apparatus for the making of clinometer sensors according to the appended claims.
The invention also provides a clinometric sensor obtained according to the aforesaid process and apparatus.
Detailed description of the invention
A detailed description of a preferred embodiment of the process and apparatus of the present invention will now be provided, by way of a not limiting example, with reference to the annexed drawings, wherein:
Figure 1 it is a general perspective view of the apparatus for the making of clinometric sensor tubes according to the process of the present invention;
Figure 2 it is a detailed view of the apparatus of Figure 1 ;
Figure 3 it is a schematic general view of the apparatus for the positioning of optical fibers onto the clinometric sensor of the present invention;
Figure 4 schematically shows a part of a tube for the construction of a clinometer by the apparatus of the present invention; and
Figure 5 schematically illustrates a portion of the clinometric sensor tube according to the present invention.
Referring now to Figures 1, 2 and 3, the process of the present invention will be described.
According to the present invention, the process comprises the following main steps:
a) providing a PE pipe;
b) feeding said tube to a surface material removal station from the surface of said PE pipe;
c) continuously performing four longitudinal grooves onto the surface of said PE tube and for the entire length of said tube, said grooves being obtained by mechanical removal or alternatively by thermal engraving;
d) positioning four optical fibers with a controlled strain, each of which in a respective groove along said PE tube; and
e) sealing said grooves containing optical fibers by fusion of PE or alternately by epoxy resins.
Figure 1 schematically illustrates an apparatus for making of the above process.
According to the present invention there is provided an apparatus 1 comprising a main frame 10 which supports a feeding unit 2 of a continuous PE 3 pipe to a forming station 4.
In the forming station 4, four longitudinal grooves are formed on the surface of said PE pipe 3. To this end, said four longitudinal grooves onto the surface of said PE tube and for the entire length thereof are continuously obtained (i.e. during the advancement of the tube 3) . The grooves are obtained by mechanical removal or, alternatively, by thermal engraving.
Then, the so-formed tube 3 is fed to a robotized station 5 for the continuously applying of optical fibers at each groove obtained in the surface of the tube 3, i.e. each optical fiber it is fed and inserted into a respective groove during the advancement of the tube 3.
According to the apparatus of the present invention it is provided that the apparatus it is capable of positioning more than one optical fiber along the longitudinal axis of the tube 3 in a spaced manner one with respect to the other, i.e. 90° or 120° one form the other.
It is necessary to emphasize here that the feeding of optical fibers to the tube 3 represents the most delicate phase of the entire process for the making of the clinometric sensor. In fact, excessive tension applied to the optical fiber during its positioning onto the tube 3 could cause excessive stress to the former, limiting the measuring range (due to excessive pre-tension) and, in the worst case, causing the break thereof.
As a schematically shown in Figure 2, the robotized station 5 comprises four aluminum coils 50 rotating on a steel shaft by means of polymer bearings.
Each coil 50 contains an optical fiber winded therein. Each optical fiber fed out of the respective coils 50 are channelled into respective guide conduits to convey each fiber into the respective groove formed on the surface of the tube 3, each guide duct has a Teflon tube inserted therein in which the optical fiber runs (said guide conduits being not shown) .
In order to convey the optical fibers in the respective Teflon tubes inside the conduit, there is provided a guide member 51 mounted frontally at the optical fiber feeding port of the respective coil 50, the guide member 51 having a conical region 52 associated to each guide conduit. The conical regions 52 on the guide member 51 allow the conveying of each respective optical fiber and avoid abnormal frictions associated with the horizontal displacement of the fiber on the coil 50 during its unwinding .
The optical fiber is then guided to the point where it is inserted into the groove made on tube 3, without being exposed to any interference that could cause its breakage. It should be noted here that, thanks to the particular configuration shown above of the station 5 and its components, the following objectives are pursued:
1. The optical fiber is under no circumstances subject to bending radii too small that may damage it;
2. The optical fiber it is mechanically protected by the guide tubes; and
3. The optical fiber, thanks to the Teflon tube inserted inside the guide tubes, it is not subjected to excessive frictions that may damage it.
Referring now to Figure 1, after having assembled the optical fiber on the PE tube at the positioning station 5 it is provided that so assembled tube is conveyed to a sealing and / or fixation station 6, where the optical fiber is fixated within the grooves formed onto the surface of the tube 3 and render the former integral to the latter.
With this aim, it is contemplated that at the station 6, the sealing of the grooves containing the optical fibers it is performed by fusion of PE or, alternatively, by epoxy resins.
Then, the tube containing the optical fibers sealed thereon it is further conveyed to a second tube supply station 7 and to the next storage or cutting step (the latter being not illustrated in the figures) .
Referring now to Figure 3, it is schematically shown a particular function of the apparatus of the present invention .
According to the present invention, the apparatus 1 also has an optical fiber continuity check system 53 during the production phases. The guaranteeing of continuity of all the installed optical fibers 53 it is a key element in the quality control process during the production steps.
As a matter of facts, the breakage of an optical fiber 53 would compromise the operation of the whole measuring system.
Therefore, in each coil 50 it is inserted a circuit capable of detecting the continuity of the fiber 53 wound onto the former, and transmitting to a control unit 8 (PLC) an alarm in the event of an interruption it is detected.
The continuity monitoring system operates according to the following scheme:
First, a laser emitter 9 it is connected to the free end of the fibers 53 to be installed. Thus, the circuits inserted inside the coils 50 are connected to the respective ends of the fibers 53 to be installed and detect the presence of the laser beam transmitted by the emitter 9 connected to the free and accessible ends of the fibers 53 (starting point of the fastening process of fibers 53 on tube 3) .
In the event that a fiber 53 is interrupted, the circuit detects the absence of the laser source signal 9 and transmits an alarm (via ZigBee communication) to PLC control unit 8, the latter activating a sound alarm and indicates which of the three fibers 53 is interrupted.
With reference now to figure 4 it shows the final arrangement of the tube 3 and the fibers 53 contained therein.
The clinometric sensor is constituted by a PE tube 3 in which three optical fibers 53 are spaced 120° one from the other, welded to the body of the tube 3 and capable of transmitting the deformations/strains to which the tube 3 will be submitted once the latter it is operational on a ground .
A fourth optical fiber 53 it is inserted into the wall of the tube 3 but installed at a position so as not to transmit deformations. Therefore, this latter fiber 53 it is intended for measuring the temperature profile which will allow compensation of the measurements by thermal variations .
For the sake of purely non-limiting purposes, it is for example shown that according to an embodiment of the clinometric sensor of the present invention, the PE pipe 3 may typically have a diameter of 25 mm and a thickness of 2 mm. For its operation, it is expected to be inserted inside a monitored ground. A soil deformation in which the clinometric system is installed causes a deformation of the tube 3 and, hence, the compressions and elongations in the optical fibers 53 contained therein.
Therefore, the processing of the stress profiles measures along the optical fibers allows to establish in the three dimensions the deformation of the tube 3, that is to obtain a clinometric profile of the soil within which the system it is installed.
It is here shown that in order to carry out the measurements and obtain the tube deformation data 3, the mathematical reconstruction method using the Euler- Bernoulli beam theory it is applied in which the components of the bending moments are integrated, Mx(z) and My(z) (respectively, along the x-axis component along the y-axis in the generic z-section) , whose modules are a function of stress, as well as the Young module associated with the material in which it is realized the tube 3, and the moment of inertia of the tube itself (in turn dependent on the geometry) .
The problem of using this method of measurement it is the propagation of the error that increases with the distance from the reference point (the bottom of the hole) .
In order to solve the above problem and as illustrated in Figure 5, according to the present invention, a series of slant (slope) sensors 30 of the biaxial digital type are inserted inside the tube (at intervals of 10 meters each) , and which allow to clear the error and have further feedback as compared to the measurements made with each optical fiber 53.
The slant sensors 30 are also equipped with an electronic compass so as to allow a precise azimuth geographical reference of the resulting shift vector.