Patent Application
20130091939
Scour is a process in which a fluid erodes material supporting a structure away from that structure. When scour occurs near a bridge, the associated erosion can cause that bridge to collapse. More particularly, bridge scour is an erosion process in which the current of a river erodes soil deposits around the foundation (piers, abutments, etc.) of a river-crossing bridge. Of course, scour can occur in many bodies of water and near other structures. For instance, bodies of salt water can give rise to scour around piers, walls, levees, etc. More specifically, with bridge scour, portions of the bridge foundation interact with the flow of the river thereby creating eddies and other phenomenon (for instance localized impingement of high speed water on portions of the riverbed) which lead to the erosion. Bridge scour (as well as other forms of scour) is therefore often characterized by the formation of scour holes, dunes, etc. around the bridge foundation.
Scour is a world-wide issue of growing concern. For instance, in the United States, scour-related erosion causes more bridge collapses than any other condition. As of 1997, more than 10,000 bridges out of the 460,000 over-water bridges in the United States were scour critical and 132,000 were scour susceptible. By 2005, however, approximately 26,000 bridges had become scour critical and more than 190,000 bridges had become scour susceptible. With the recent spate of floods, it is likely that even more bridges have become scour critical, potentially resulting in failure of some of these bridges.
The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an extensive overview of the disclosed subject matter, and is not intended to identify key/critical elements or to delineate the scope of such subject matter. A purpose of the summary is to present some concepts in a simplified form as a prelude to the more detailed disclosure that is presented later.
Generally, this document describes embodiments of sensors, systems, and related methods which can help tackle challenges associated with monitoring and mitigating erosion in general and scour more particularly. More specifically, one embodiment provides a system for measuring the erosion around bridges caused by scour. These systems can include sensors designed to mimic naturally occurring rocks. This configuration of the sensors enables users to drop the sensors into a river thereby mitigating the scour in some cases.
Generally, embodiments provide systems which work on the following principals (among others):
Embodiments also provide integrated scour monitoring and mitigation systems. These systems can measure the motion of the sensors as the sensors move about under the influence of liquid in which they are submerged. In some embodiments, the motion of individual sensors is measured whereas in other embodiments the motion of a group of sensors is measured. Whether individual sensors are tracked, or groups of sensors are tracked, the mobility of the sensors can indicate the scour susceptibility/criticality of various monitored structures.
Systems of some embodiments can include a group of such sensors (and other types of sensors if desired), each with an embedded magnetic device in wireless communication with a measurement instrument (such as a magnetometer). These sensors can also possess densities sufficient to cause them to sink in, yet be moved by, flowing water in a manner similar to naturally occurring rocks (or other filler material). Systems of such embodiments can be used to monitor, prevent, and mitigate riverbed scour-related conditions near bridge foundations. In some embodiments, a user places the sensors near the foundation of a bridge before, after, or even during a scour event. When floods or other scour-inducing events occur, the river current typically moves (or at least re-orients) some of the sensors. As a result of the movement and/or reorientation of the sensors, the three dimensional magnetic field caused by the group of sensors measurably changes. Hence one can observe changes in the magnetic fields during flood conditions, as they indicate movement of sensors, or one can, using many field measurement points reconstruct the location of sensors, without waiting for changes. Changes in the location or orientation of the sensors can be related to characteristics of the scour associated with the bridge foundation. For instance, the as-sensed changes in the magnetic field can be related to the time-varying depth, width, and locations of voids and accumulations of material in or on the riverbed.
Some embodiments provide systems which include a sensor and a signal generator with a combined density equal to or greater than that of water. Optionally, the sensor can be a magnet, resonator, or accelerometer. Moreover, the sensors can be adapted to be placed in regions potentially subject to scour and to sense scour-related conditions. The signal generator of some sensors generates a wireless signal conveying data regarding the as-sensed scour-related. In some embodiments the sensor is the signal generator while a receiver for the wireless signal can include an antenna, a magnetometer, or an ultrasonic sensor. In some embodiments, the housing is conic and the magnetic object is offset from the center of gravity of the coupled sensor, signal generator and housing.
In methods implemented in conjunction with various embodiments, sensors can be placed near existing bridges shortly before (for instance, about one day before) a predicted flood or other scour-inducing event. Since sensors of various embodiments can be dropped into place (or otherwise positioned) and their movements and orientations tracked, such techniques can allow real-time and cost-effective monitoring of scour. Thus, systems of various embodiments can facilitate evaluation of the scour-related condition of bridge foundations and can enable damage reduction, mitigation, prevention, etc. Sensors of various embodiment and/or other types of scour sensors can be applied to many structures (for instance, sea-crossing bridges, levees, pipes undersea cables, etc.) with results similar to those disclosed above. Should scour be detected, sensors and other filler material (artificial objects, naturally occurring rocks, etc.) can be placed near a scour critical (or other) structure to stabilize it based on real-time, reliable, and robust data obtained from various sensors.
Yet other embodiments provide methods of monitoring and/or mitigating scour. In some of these methods, at least one sensor with a density about equal to or greater than water (for instance densities between about 1.2 g/cm̂3 and about 5.3. g/cm̂3) is placed in water at a location where the water is expected to flow and (potentially) cause scour. The sensor includes an object which alters the magnetic field in its vicinity in response to a change in a scour-related condition at about the location of the sensor. Additionally, such methods include allowing a scour-related change to occur at or near the sensor and allowing the sensor to cause a wireless signal to propagate through the water to convey data regarding the scour-related condition.
In some methods the sensor can include a signal generator in communication with the sensor to cause (or transmit) the wireless signal. The signal generator can be a passive magnet, an actively powered magnet, a magnetic resonator, an accelerometer or a combination thereof with, or without, other types of instruments. If desired, the object can be the signal generator. Moreover, in methods of some embodiments, the wireless signal is received and the data conveyed thereby is correlated to determine the scour-related condition.
Some embodiments provide methods for measuring erosion. For instance, some of these methods include placing a sensor (having an associated sensor identifier) in a region through which earthen material is expected to move. These methods also include sensing a condition related to the movement of the earthen material with the sensor and receiving a first wireless signal conveying a sensor identifier associated with a second sensor. Moreover, these methods also include generating a second signal conveying the first sensor identifier and the second sensor identifier and locating the first sensor using the second signal. In some cases, the second signal is wireless too and it can be used to locate the second sensor. Furthermore, locating of the second sensor can include using an identifier/distance pair associated with the second and first sensors which was conveyed by the second signal. Note that sensors of embodiments can “sense” their own location by producing a signal (magnetic, magneto-inductive, acoustic, etc. which identifies their location when triangulated or otherwise determined).
Still other embodiments provide systems for measuring erosion wherein the systems each include at least a first sensor. The first sensor is adapted to be placed in a region through which earthen material is expected to move as the erosion occurs and to sense a condition related to that movement. For instance, the position of the sensor can be that condition. In addition, the sensor has an identifier associated with it. In operation, the sensor receives a first wireless signal from another sensor wherein that signal conveys a second identifier associated with the other sensor. The first sensor also includes a signal generator that generates a second signal conveying the identifiers of both sensors (if available).
Moreover, in some embodiments, the second signal is also a wireless signal and the system includes the second sensor. The first sensor can be mounted on a structure with a bracket or it can be so dense (or heavy) that it is unlikely to be moved during erosion events. If desired, the sensor can determine the signal strength of the signal that it receives from the other sensor and can convey an indication of that signal strength in the first wireless signal. Furthermore, some sensors include accelerometers, roll sensors, tilt sensors, yaw sensors, magnetometers, etc. and the first wireless signal can be an acoustic or magneto-inductive signal.
Other embodiments provide methods for measuring erosion. Such methods include placing a first sensor (having a sensor identifier) in a region through which earthen material is expected to move. A condition related to the movement of the earthen material is detected using the first sensor. For instance, the sensed condition can be the location of the first sensor. These methods also include receiving a first wireless signal (using the first sensor) conveying a sensor identification associated with a second sensor and generating a second signal conveying the first and the second identifiers.
If desired, the second signal can also be wireless. The signal strength of the first signal as it is received can be determined and (if desired) the second signal can also convey an indication of that received signal strength. Furthermore, some methods include sensing the acceleration of the first sensor.
To the accomplishment of the foregoing and related ends, certain illustrative aspects are described herein in connection with the following description and the associated figures. These aspects are indicative of various ways in which the disclosed subject matter may be practiced, all of which are intended to be within the scope of the disclosed subject matter. Other advantages and novel and non-obvious features may become apparent from the following detailed description when considered in conjunction with the figures.
The detailed description is written with reference to accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items.
This document discloses techniques and technologies for monitoring erosion related conditions. More particularly, this document discloses techniques and technologies for integrated monitoring and mitigation of hydraulic scour associated with bridge foundations and other structures (for instance levees).
For the illustrated situation, scour has occurred close enough to shore that a truck can deliver the filler material 104 and sensors 106 to the scour site. If the scour had occurred further from shore or at some other location inaccessible to a truck, then a crane, barge, or other device could be used to deliver the filler material 104 and sensors 106 to the site. Moreover, users can drop additional sensors 106 into the water at the region 108 of interest as is shown in
These users have also deployed a pair of antennas 116 to receive wireless magnetic signals 118 from the sensors 106. In addition, in this case, the users have deployed a magnetometer 120 to sense the magnetic field 122 associated with the passive sensors 106B. As disclosed further herein, though, other communication methods can be employed. For instance, the sensors 106 can use ultrasonic communication, can back scatter RF signals using resonators at the same frequency or at the frequencies of the resonators (positioned in various receiving devices located on shore or elsewhere). From the data gathered by the antennas 116 and the magnetometer 120, the users can derive information related to the location and dimensions of various scour-related voids and formations near the bridge.
Bridge collapses due to scour often occur rapidly, sometimes within hours or days from the onset of scour critical conditions.
Furthermore, while a number of approaches exist for measuring scour-related conditions, previously available approaches suffer from certain disadvantages.
Embodiments disclosed herein can be successfully applied to structures before, after, and even during scour-inducing events. Thus, knowledge of scour-related conditions can be obtained during all periods pertinent to the monitored structures. More particularly, scour sensors can be placed in regions 108 where scour is likely even during a time when scour susceptible and scour critical conditions might arise (for instance, during a flood). Various embodiments disclosed herein can therefore provide interested users with real-time information pertinent to understanding and evaluating changes that occur during such events (in addition to before-and-after comparisons of scour-related conditions).
More specifically, systems of some embodiments include rock-like objects or concrete blocks with 1) embedded passive or active electronics, 2) a physically separate monitoring station or receiver, and 3) a wireless communication link there between so that related parameters (the locations of the sensors, the density of a group of sensors, their proximity to neighboring sensors, the acoustic noise or vibration level in the river, etc.) can be determined under strong flooding (or other) conditions. The information derived there from can enable scour evaluations and mitigation in real time. Embodiments disclosed herein include passive sensor embodiments and active sensor embodiments as illustrated by
Real-Time Scour Mounitoring with Passive Sensors Group Dispersion Methods
Some passive sensor 106B embodiments involve creating a constant magnetic field 122 about each of (or some of) a group of passive sensors 106B. As disclosed further herein, the constant (with respect to the sensors 106) magnetic fields 122 can be used for locating them as a group (passive sensor group dispersion) or individually. Magnetometers 120 can be used to measure the intensity of the combined magnetic fields 122 from the Earth, the passive sensors 106B, and the ferromagnetic parts around a bridge foundation or other structures.
In some passive embodiments, each passive sensor 106B includes a magnet 124 embedded in a housing 126 (see
Various methods can be used to increase the magnetic fields 122 of passive sensors 106B. For instance, instead of using one passive sensor 106B, a group of passive sensors 106B can be placed near a bridge. Since the group will function like a large multi-pole magnet 124 (with the resulting magnetic field 122 reflecting contributions from each of the individual passive sensors 106B), the resulting magnetic field 122 can be used to detect the location of the group of passive sensors 106B. In addition, or in the alternative, the magnets 124 of a group of passive sensors 106B can be allowed to align themselves with the surrounding magnetic field by fixing the magnets 124 after the passive sensors 106B have been put in place. Not only might the alignment increase the magnetic field but it might also create a magnetic field which reflects the uniform orientation of the magnets.
Another way to align these magnets 124 is to insert the magnets 124 into holes in the sensor housings. The holes can be shaped to correspond to the shapes of the magnets 124 while leaving gaps between the magnets 124 and the housings 126. These gaps can be filled with an epoxy or some other material that will eventually set within a selected time (such as 10-30 minutes) thereby fixing the magnets 124 in the housing. The resulting passive sensors 106B can be sealed and placed in the water at desired locations while the gap-filler material begins setting as shown in
In another embodiment, the magnets 124 align themselves with the surrounding magnetic field (often the Earth's magnetic field) as follows. In the current embodiment, the magnets 126 do not have an offset between their centers of gravity of the magnets 124 and the geometric centers of the sensors 106. Instead, the magnets 124 remain free to rotate in accordance with the surrounding magnetic field until the gap-filler material sets. Thus, once the magnets 126 are inserted into the sensors 106 and the sensors 106 settle, the magnets 126 rotate to align themselves with the surrounding magnetic field. Since the surrounding magnetic field will generally be that of the Earth, the individual magnets 126 will align with the Earth's magnetic field. Further, since all of the magnets 126 are aligned with a common reference (the Earth's magnetic field), they can all be aligned with each other if desired. Such sensors 106 can find application in situations where the sensors 106 near a particular structure are, or will be, dispersed from one another.
In the alternative, or in addition, steel blocks can be embedded into some passive sensors 106B to concentrate or focus pre-existing magnetic fields in their vicinity. Since the steel blocks cause no magnetic field of their own, it is likely that such sensors 106 can be used without orienting the steel blocks. Thus, in various embodiments, the magnets 124 of the sensors 106 can be aligned with each other thereby providing a magnetic field 122 reflecting that uniform alignment and which is stronger than it would be were the sensors 106 were not aligned.
Sensors of some embodiments include magnets 124 which are configured to always point up to facilitate locating such sensors. More particularly, since the dipole moment orientations of the magnets are known (or can be measured) prior to placing such sensors in an area of interest, these sensors can be more readily located than those in which the magnet might rotate with the sensor. To create a sensor 124 of the current embodiment, the magnet can be allowed to rotate within an asymmetric sensor body so that the south pole always point up.
Whether the passive sensors 106B are aligned or not, an instrument such as a magnetometer 120 can measure the resulting magnetic field 122 produced by the in-situ sensors 106 and changes to the same. For instance, when three-dimensional scour-related data is desired, several (for instance, three or more) magnetometers 120 can be used to enable real-time evaluation of bridge scour (in terms of the maximum depths of scour-induced holes as well as other riverbed changes) by an evaluation of the positions of the sensors. In some cases, this evaluation process can use an inverse transformation to identify the presence and location of a group of sensors 106 from the measured magnetic field data. Thus, the passive sensors 106B sense (by their presence in the resulting riverbed formations) the scour related erosion of the riverbed. The tracking of the passive sensors 106B can be performed continuously (providing real-time scour information if desired) or on a selected schedule. Moreover, the locations of the passive sensors 106B as a group can be tracked to provide scour-related information.
At times it might be found desirable to add passive sensors 106B to a particular location. For instance, should some of the passive sensors 106B move away from the bridge, more sensors 106 can be added to the site. Indeed, in some cases, it might be useful to have about 10% to about 30% of the filler material 104 at a particular location be sensors 106 as shown in
Even so, during a scour-inducing event, the passive sensors 106B (and other objects and materials) in the water will likely be washed away or re-oriented. As a result, the combined magnetic field 122 (and/or the topology thereof) of the passive sensors 106B group will change in a corresponding fashion. Indeed, whereas a group of deployed sensors 106 will have an initial magnetic field 122 reflecting their originally deployed orientation (in line with the surrounding magnetic field, having an orientation of its internal DC magnetic field 122 parallel to the gravity-oriented magnetic field 122, etc.), a group of sensors 106 disturbed by a scour event will likely exhibit a changed magnetic field 122. In many cases, the signature of the magnetic field 122 of the passive sensors 106B will be randomized as compared to the original signature. As noted elsewhere herein, these changes can be measured. Thus, the data obtained from such sensors 106 can signify the onset and level, or degree, of bridge scour. In other words, the randomization of the magnetic field alone indicates that erosion has occurred. Further measurement and analysis of the magnetic field can determine the extent of that erosion.
Initial tests of a passive system 100 were recently conducted at the Missouri University of Science and Technology (hereinafter “Missouri S&T). The experimental passive system 100 included magnets emulating the sensing unit of passive sensors 106B. In these tests, three groups of magnetic objects were tested at Missouri S&T and include a 6 cm magnet cube, 0.75 cm×15 cm×75 cm steel plates, and 15 cm-long #8 steel bars. Each of these magnetic objects was pulled in one direction and its position was detected with a model number G858 Geometrics magnetometer 120 (available from the Oyo Corporation USA in San Jose, Calif.). Plots 702A and 702B (of
The size, shape, and magnetic strength of the magnets in passive systems 100 can be optimized and calibrated in field applications on bridges and on other structures. Passive systems 100 can be used where measuring the location of a group of sensors 106 and a relatively simple system are desired. However, as disclosed herein, passive systems 100 can be used where measuring the location of individual sensors 106 is desired and/or in more complex situations.
Real-Time Monitoring with Active Sensor Positioning Methods
Several methods of measuring scour using active sensors 106A employing magneto-inductive communication are also disclosed herein. In some active embodiments, active sensors 106A include resonators 128 (see
Some active embodiments involve enabling magneto-inductive communications between active sensors 106A and a receiver. These communications can be used to identify and locate individual active sensors 106A at frequencies less than 10 MHz in some embodiments. However, higher communication frequencies are within the scope of the disclosure. In some embodiments communication methods such as magneto-inductive or sound-based methods can be used to query active sensors 106A regarding various scour-related conditions.
As with the passive sensors 106B disclosed herein, these active sensors 106A can be configured to have densities, shapes, sizes, etc. selected to mimic naturally occurring rocks (or other filler materials 104). Thus, active sensors 106A can be configured to respond to flowing water in a manner similar to that of naturally occurring rocks.
As illustrated in
The system of the current embodiment can use two communication methods although the disclosure is not limited to these communication methods. For one communication method, some sensors 906A use active magneto-inductive communication links and contain a battery and timer and possibly a receiver to wake up the system. Thus, these particular sensors 906 can happen to transmit information at select times (for instance, every hour). However, the active communications of these sensors 906 could occur via ultrasonic or other types of transmitters. For the other communication method of the current embodiment, some sensors 906B use passive magneto-inductive communication via RF (radio frequency) signals. A transmitter (with a signal strength selected to provide communications between the transmitter and the sensors 906) transmits a signal to the sensors 906. These sensors 906 detect the transmitted signal and send it back to the transmitter (or receiver thereof). These sensors 906 can send the signal back to the transmitter by passive scattering, rectification, activation of an active circuit therein, etc. The active circuits of such sensors 906 can be similar to those found in RFID (radio frequency identification) tags.
In another embodiment, each sensor 106 includes a magneto-inductively powered rectifier. In such embodiments each sensor 106 detects an external signal and rectifies it to power a transmitter circuit that sends (on another frequency) a code for identifying that sensor 106. In addition to the code, these sensors 106 of the current embodiment can send information related to their physical orientations as measured by built-in accelerometers. Some of these built-in accelerometers can be configured to detect the Earth's gravitational field and to compare the orientation of the active sensors 106A (in which it is located) to that field. Further, if desired, the magnetic field of the earth can be measured to remove ambiguity in the determination of the system's orientation that might occur if only the gravitational field of the earth is used. The resulting information can be transmitted and used to measure how much these active sensors 106A have moved or otherwise been reoriented.
In yet another embodiment, some or all of the sensors 106 include a battery and a timer. Some of these timers can draw power from the batteries and can trigger transmission bursts at selected times. As a wristwatch can run on a small battery for three years or longer, a sensor 106 with a timer operating on a battery can last for decades. Since each transmission burst can be of relatively short duration (less than 1 second), the integrated energy consumption will be low in spite of the occasionally increased current draw associated with these transmission bursts. Moreover, the underwater environment where such sensors 106 are expected to typically reside in operation is favorable for batteries (temperatures in such locations varies slowly and over a limited range) thus enabling long battery lives. Nonetheless, active sensors 106A of the current embodiment can be configured to minimize the energy consumption from self discharge and from standby circuits to extend the battery life of some active sensors 106A. It is expected that a battery life of 10 years is achievable for at least some active sensors 106A.
Active sensors 106A (see
The latter variant can be applied to automatically alert an engineer-in-charge (or other users) to evolving scour-related information through an Internet or telephony connection or other telecommunication techniques. Such active sensors 106A could transmit a variety of information related to scour including the distance to other sensors 106 from itself and/or acoustic noise at its location.
Preliminary simulations regarding the signal-to-noise ratio show the possibility of communications through water and between active sensors 106A and receivers at frequencies below 1 MHz (although communication at higher frequencies is also included in the scope of the disclosure). In a non-optimized scenario, communication between an active sensor 106 at a depth of 2 m in fresh water was achieved with a receiver using two 0.5 m×0.5 m antennas 116. One antenna 116 of this system 100 was placed 5 m to the left and the other antenna 116 was placed 5 m to the right of the sensors 106. Performance of other systems 100 can be improved by using larger antennas 116, more turns, higher power, and/or various signal processing techniques. Alternatively, the antenna(s) 116 may be installed around a bridge pier 110 close to the potential scour region 108 to minimize the communication distance.
As disclosed herein, different types of sensors 106 (with passive structures inside, with semi-active structures inside, and with batteries or other active components inside) are provided in this disclosure. The ability to communicate with those sensors 106, to locate the sensors 106, and the complexity and life spans of the systems 100 can be factors to consider in selecting a system 100 for scour measurement and/or mitigation applications.
The size of the antennas 116, the number of antennas 116 and their position relative to the potential scour region 108 can influence the ability to communicate with and locate various types of sensors 106. If the antennas 116 are embedded into piers 110 (for bridges under construction or those being retrofitted), they can be close to the sensors, thus improving the communication with, and the localization, of such sensors 106.
Signal processing is another way to improve the quality of the information received from the sensors. There are many ways to process signals and extract information even from weak or conflicting signals. Any of these and other techniques can be employed to improve the recovery of the information transmitted from (or otherwise provided by) sensors 106 in a given system 100.
If a magneto-inductive communication is considered, the salinity (and therefore conductivity) of the water can influence the ability to communicate magneto-inductively with, and to locate, sensors 106 deployed in such environments. Typically, lower communications frequencies allow for better communication through salt water. Moreover, systems 100 of some embodiments can use magneto-inductive, sonic, ultrasonic, electromagnetic, and other methods of communicating scour-related information to the receiver. Thus it is possible that different system 100 designs can be optimized for different situations based on tradeoffs between antenna size, antenna positioning, communications frequency(s), power, reliability, etc.
Recently, some electromagnetic simulations were conducted at Missouri S&T to evaluate the feasibility of active sensor positioning. The results indicate that it is possible to reconstruct the paths of individual sensors 106 during the scour process. Doing so can entail integrating the signals from one or more accelerometers on the sensors 106 of interest. In addition, or in the alternative, the overall movement of a particular sensor 106 or groups of sensors 106 can be monitored with active systems 100.
Sensors 106, systems 100, and their wireless sensing networks of various embodiments provide non-limiting advantages over technologies heretofore available. First, the architecture of sensors 106 (such as the magnetic sensors of various embodiments) and their wireless sensing networks can be relatively simple. They can be easy to install and the data acquired there from can be easy to process. One pertinent measurement principle used in such embodiments is based on classical magnetic field theory. In some embodiments an inverse transform is performed to identify the presence of sensors 106 from measured magnetic field data. Systems 100 of many embodiments require minimal (or no) professional services to install and operate in practical applications. Moreover, systems 100 can be installed at the time of foundation construction, when scour monitoring is desired, during scour events, and/or during scour mitigation efforts.
Second, sensors 106 can be durable and applicable to environments with high water velocities, debris 114 or ice entrained in a current. With the protection offered from the bodies or housings 126 of some sensors 106, the embedded devices can survive various harsh environments and can be operational throughout the life span of an engineering structure (for instance, bridges or offshore platforms).
Third, sensors 106 can be multi-functional. More particularly, systems 100 can combine the scour monitoring and scour protection/mitigation into one integrated implementation. Systems 100 of embodiments can be applied to the bottom of the bodies of water formed from soil, rocks, sand, other materials, or various combinations thereof thereby extending the application range of systems 100 beyond that of previously available technologies.
Fourth, systems 100 can be small, portable, and easy to deploy. For instance, a group of sensors 106 and a magnetometer 120 (or other receiver) can be configured to fit in a back pack which can be carried to a place near, or at, a potential scour site. The magnetometer 120 can be deployed and the sensors 106 dropped or otherwise placed in a region 108 of interest. The initial magnetic field 122 and changes thereto can be measured with the magnetometer 120 with data analysis occurring at the same (or some other) time. Nonetheless, the deployment of systems 100 of the current embodiment can take only a few moments or less.
Next, such systems 100 as those disclosed herein can be inexpensive. According to the Hydrologic Engineering Center (HEC), the instrument costs of various scour monitoring technologies are approximately: $2000 for physical probes, $15,000 for a portable sonar survey grade system, $5,000-$15,000 for a fixed sonar, $7,500-10,000 for a sounding rod, $5,000-10,000 for a magnetic sliding collar, $3,000 for a float-out system or $500/float-out, $10,000 for traditional land survey, and $5,000 and $20,000 for Global Position System (GPS) of sub-meter and centimeter accuracy, respectively. See Lagasse, P. F., Richardson, E. V., and Schall, J. D., “Instrumentation for Monitoring Scour at Bridge Piers and Abutments,” NCHRP Report 396, Transportation Research Board, National Research Council, National Academy Press, Washington, D.C., 1997, p. 109. In comparison with these previously available technologies, a system of twenty sensors 106 of some embodiments might cost as little as $1,000.
Thus, embodiments provide solutions to the largest cause of bridge collapses in the United States due at least in part to their ease of use, low or non-existent maintenance considerations, cost effectiveness, and/or other considerations. Moreover, sensors 106 of various system themselves can be used to mitigate scour conditions since they can be configured to have pertinent characteristics (for instance, density) similar to those of naturally occurring rocks and/or other objects sometimes used to mitigate scour-related conditions. Another advantage provided by embodiments is that some systems 100 can be placed on and/or near existing bridges whereas previously available systems 100 and/or methods need special installations on the bridge and/or under the water.
In some cases the erosion could be scour or other types of erosion such as the displacement caused by a landslide (wherein the structure might be a retaining wall, highway, tunnel opening, etc.). Moreover, the structure (and its environs) has been instrumented with an erosion monitoring system 1000 which happens to include a receiver 1016 and one or more sensors 1006 (either active, passive, or a combination thereof). In the current embodiment, the sensor 1006 was buried in the earthen material 1030 (soil, sand, gravel, stones, sediment, clay, regolith, and/or the like.) during the construction, repair, or retrofit of the structure 1010. More specifically, the sensor 1006 was placed directly under the receiver 1016 at some generally vertical distance z1 therefrom. Prior to its placement, the properties of the sensor 1006 were chosen so that the sensor 1006 happens to be heavier than the earthen material 1030, the water, and other materials likely to be present in the environs of the instrumented structure.
As a result, as earthen material 1030 erodes from under the sensor 1006, the sensor 1006 will sink in a generally vertical fashion. Since the magnitude of the signal received by the receiver 1016 from the sensor 1006 depends on the distance between the two devices, the signal strength provides a more or less direct measurement of the distance z1 and, hence, the extent of the erosion present at the location of the sensor 1006. The receiver 1016 can be queried to obtain the distance z1 (or signal strength) by any available method such as by querying it with a magneto-inductive signal or an acoustic signal. The former being useful when the receiver 1016 is located in the air and the latter being useful when the receiver is located in water. Although, other signaling schemes could be employed.
Thus, each sensor 1106 will at some time likely become exposed to the forces causing the erosion and roll or tilt accordingly as the erosion reaches its depth. As a result, sensors 1106 equipped with tilt/roll/yaw sensor(s) and placed in accordance with
As
Each of the sensors 1206 includes an internal receiver with which it listens for signals (be they magneto-inductive, sonic, etc.) from the other sensors 1206 and measures the received strength thereof. Since the sensors 1206 can be configured to transmit their identifiers in the signals, each of the sensors 1206A can identify the other sensors 1206B and the distances d1 thereto (by correlating the received signal strengths with those distances d1). Furthermore, each sensor 1206A can transmit a signal to the base station 1208 conveying its identifier, and the identifier/distance pairs associated with the other sensors as measured by it. The sensors 1206 of the current embodiment also transmit their own identifier and the identifier/received-signal-strength pairs. Of course, for each signal received, each sensor 1206 can associate a distance d1 (or received signal strength) with the identifier conveyed by the signal thereby forming another identifier/distance pair.
For its part, the base station 1208 can be configured to receive the signals from the sensors 1206 conveying the identifier/distance pairs which they developed. Moreover, the base station 1208 can re-transmit this information to the network device 1216. The base station 1208 (or network device 1216) can use this information to locate the sensors 1206 which are in communication with each other and/or the base station 1208. In other words, the base station 1208 can use the collection of identifier/distance pairs to form and solve a system of simultaneous equations for the locations of the sensors 1206 (relative to the base station 1208). These systems of equations can make use of a priori knowledge of the antenna patterns and/or transmission strengths of the sensors 106. Note also, that the base station 1208 can measure the received signal strengths of the signals reaching it from each of the sensors 1206 to provide another set of identifier/distance d2 pairs associated with the sensors 1206 which it can sense. Here, distance d2 happens to be the distance between a sensor 1206 and the base station 1208. In addition, note that some of the sensors 1206 can be too far from the base station 1208 to effectively communicate with it. However, these relatively distant sensors 1206 can still participate in the system 1200 by communicating indirectly through another of the sensors 1206 acting as an intermediary in the network.
Note that the base station 1208 can be configured to remain in a fixed location even during erosion inducing events such as landslides, floods, etc. For instance, the system 1200 can include a bracket 1218 attached to the base station 1208 and coupled to the structure 1210. In the alternative, or in addition, the base stations 1208 can be dense or heavy enough that, given expected conditions, the erosion inducing event(s) would be unlikely to move it.
Another aspect of system 1200 is that it allows users to calibrate network devices 1216 for local/instantaneous conditions. In other words, upon setting up a new network device 1216 (or at other times) the user can measure the received signal strength from the base station 1208 using the network device 1216 (or a magnetometer) and, given the known distance z2, calibrate the network device 1216 for current conditions.
System 1200 can include only one network device 1216 thereby simplifying the “on-bridge” (or other structure) portion of the system 1200. More specifically, if a portable system 1200 is sought, a one-network-device system 1200 can be used since the single network device 1216, base station 1208, and collection of sensors 1206 can be carried more easily than the corresponding components of a multi-receiver system.
In some embodiments most, if not all of the processing is performed in the network device 1216. In other words, the sensors receive signals from each other, determine the received signal strengths and pair that information with the corresponding sensor identifiers. The sensors 1206 transmit the received signal strength/identifier pairs to the base station 1208. The base station 1208 determines the received signal strengths from each of the other sensors 1206 and appends the resulting information to the other received signal strength/identifier pairs. The base station 1208 forwards the compiled information to the network device 1216 which then solves for the location of the sensors 1206.
Moreover, it might be worth noting that system 1200 acts much like an ad hoc network with the sensors 1206 communicating among themselves and/or with the base station 1208. Thus, even if a particular sensor(s) 1206 malfunctions, the system 1200 will continue to operate with, at worst, one set of identifier/distance pairs missing.
Of course, as erosion moves the sensor 1306, the new or changing location of the sensor 1306 can be obtained by triangulation. By selecting the locations of the network devices 1316 relative to the location (and/or expected location) of the sensor 1306 to provide resolution in all three dimensions, the location of the sensor 1306 can be determined in all three dimensions. It is noted here that the improved spatial resolution available with increasing inter-receiver spacing can be balanced against the greater signal strength at decreasing sensor-to-receiver distances. Indeed, systems 1300 of some embodiments include 4 or more network devices 1316 with at least one being vertically offset from the others. Moreover, at least one network device 1316 can be place on either side of the sensor 1306 as seen looking along the direction in which the sensor 1306 is expected to move. Furthermore, some network devices 1316 can be placed upstream and some downstream from the location and/or expected location(s) of the sensor 1306. For instance, one or more network devices 1316 can be placed on a structure 1310 for which erosion data is sought.
It might be worth noting at this juncture that both the Earth's (or environmental) magnetic field and the coil's magnetic field (when energized) orient the magnet 1408 of the current embodiment. Thus, if the environmental magnetic field is known or can be measured, then the field coupling pattern of the magnet 1408 can be determined mathematically thereby facilitating detection of the sensor 1406 and determination of its orientation and location (using either magnitude or phase techniques or a combination thereof).
Moreover, if desired, various sensors 1406 could include pressure sensors 1416 to aid in determining the depth at which the sensors resides. Thus, when the sensors 1406 are placed in water the water pressures sensed by the pressure sensors 1416 give an indication of the depths of the sensors 1406. Sensors 1406 of such embodiments can find use in water and/or in water-saturated earthen materials. Moreover, some sensors 1406 couple the pressure sensor 1416 to a sealed tube 1418 which has a flexible diaphragm at the end flush with the surface of the sensor 1406. Thus, the pressure sensor 1416 communicates with the ambient environment while being protected from the environment (particularly water) and need not itself be waterproof. Moreover, the rest of the sensor 1406 can be sealed and/or filled with some inert liquid to make the sensor 1406 more waterproof than might otherwise be the case.
With continued reference to
With continuing reference to
Thus, when it is desired for the base station 1508 to either power a sensor 1506 via a magneto-inductive signal or to communicate with a sensor(s) 1506, the processor 1522 sends a signal to the driver 1531 indicative of which output device to use. Depending on whether the processor 1522 has selected the acoustic transducer 1532 or the antenna 1534, or both, the driver 1531 routes the modulated signal to the selected output device. Note that it has been found that for both acoustic and magneto-inductive transmissions the driver 1531 can drive the selected output device(s) at the same frequency. In some embodiments, the driving frequency is 125 kHz+/−5 kHz. In other embodiments, the driving frequency is 250 kHz. At or near these frequencies both communication methods work sufficiently well for many applications. However, it is expected that frequencies as low as 5 kHz can be used with success in certain situations. The selected output device 1532 or 1534, of course, drives the modulated signal out into the environment.
Still with reference to
Additionally, the sensors 1506 of the current embodiment can include a processor 1550 and a memory 1560. The processor 1550 can execute various programs, codes, algorithms, etc. for operating the sensor 1506. Of course, the memory 1560 can provide storage capabilities for such algorithms, codes, programs, etc. and for data generated or used in the course of sensor 1506 operations.
In addition, sensor 1506 of the current embodiment includes a variety of transducers. For instance, sensor 1506 can include roll, tilt, and yaw sensors 1566, 1568, and 1570 respectively. In the alternative, or in addition, the sensor 150 can include an accelerometer 1576 or other device to sense acceleration (or movement) along one or more translational or rotational axes. The sensors can also include a magnetometer and/or pressure sensor 1572 and/or 1574 as desired. Note that integrating the roll, tilt, yaw, and acceleration signals from sensors 1566, 1568, 1570, and 1576 allows one to reconstruct the path that a sensor has taken through floodwaters. Indeed, the feasibility of this capability has been demonstrated by Missouri S&T using computer simulations.
A prototypical system 1500 was recently constructed at Missouri S&T. In the prototypical system a Microchip PIC16LF1823 (available from Microchip Technology Inc. of Chandler, Ariz.) served as the processor 1550 of the sensor 1506. In part, it was chosen for its low power abilities. Communications between the various components of a prototype sensor were implemented using a Phillips I2C compatible bus. Moreover, the driver 1538 was implemented using the EUSART (Universal Asynchronous Receiver Transmitter) capabilities of the processor described above. Successful sensor-to-receiver communication tests were conducted at both 125 and 250 kHz in air, fresh water, and salt water using a loop antenna network device 1510 which measured less than a meter in diameter for the network device 1510.
With reference now to
At reference 1604 various sensors 106 (see
If passive sensors 106B (are to be used and if it is desired to fix the orientation of the magnets therein), then at reference 1606 that can be accomplished. For instance, the magnets can be placed in the sensors and an RTV (room temperature vulcanizing material or some other curable material) can be poured in around them. This action will allow the magnets to orient themselves in a vertical direction if desired. The RTV can then be cured thereby fixing the orientation of the magnets in the sensors 106B.
The receivers can also be set up near the region where the sensors 106 are to be placed as illustrated at reference 1610. Of course the sensors 106 could be placed first. But often, the receivers will be set up first for reasons which will become clear. For instance, with the receivers set up, the sensors 106 can be calibrated one at a time (or in groups) while they are more readily accessible to the users. In some situations, one sensor 106 will be brought near the receiver and the receiver's response noted. Then, the sensor 106 can be moved away from the receiver by some select distance and the response again noted. Thus, it will be known how the sensor 106 and receiver combination respond to changes in their relative locations. The process can be repeated for each of the sensor 106 and receiver combinations. In addition, or in the alternative, a group of sensors 106 (particularly passive sensors 106B) can be calibrated by moving the sensors 106 away from/toward the receiver. Moreover, should it be desired, the passive sensors 106B can be selectively re-oriented and/or scattered to emulate the randomization that might occur during erosion. See reference 1612.
At some point, the sensors 106 can be placed in the region of interest. For instance, if a new structure is being built, the sensors 106 can be buried near the structure, left on the surface, or pre-positioned elsewhere at select locations. More particularly, sensors 106 can be placed away from the structure and/or in the region as desired. The locations of the sensors 106 can be recorded (by, for instance, photographing the scene) if desired. See reference 1614. Of course, sensors 106 could be placed near or retrofitted onto existing structures.
At reference 1618 some or all of the sensors can be activated. For instance, magneto-inductive power can be broadcast to the sensors 106 by the receiver to activate/power them. In the alternative, or in addition, an activation signal can be sent to those sensors 106 configured to remain in a low power state until receiving a signal indicating that some other power state is desired. As a result, various sensors 106 will become active (for instance, some passive sensors 106B might begin back scattering the magneto-inductive signals generated by the receiver). Of course, some active sensors 106A can be activated before they are placed in the environment.
If sensors 1506 which are capable of forming a network among themselves have been activated, it is possible that they will begin forming a network at about this time. For instance, a particular sensor 1506 might recognize a signal coming from a receiver and establish communications therewith. See reference 1622. Moreover, another sensor 1506 might begin broadcasting identifier/distance pairs which the other sensors 1506 then begin to receive.
As the system continues to operate, the various sensors 1506 can continue transmitting identifier/distance pairs as illustrated by reference 1628. Of course, the sensors 1506 can continue to transmit the other readings which they are configured to gather. For instance, indications of their roll, tilt, yaw, acceleration, etc. can be transmitted along with (or separately from) the identifier/distance pairs.
The base station 1508 (and/or network device 1510) can gather the various identifier/distance pairs (and other information). At some time, the base station 1508 can assemble the identifier/distance information into a list and transmit that list to the network device 1510. From that information, the network device 1510 can determine the locations of the various sensors 106 by solving a set of simultaneous equations which models the locations of the sensors 106. See reference 1630. Moreover, having located the sensors 106, the network device 1510 can determine how much erosion has occurred as illustrated at reference 1632. As a result, users can mitigate the erosion if desired by, for instance, placing filler material and or sensors 106 in the region. See reference 1634.
Thus, a number of embodiments have been provided for measuring erosion and related phenomenon such as scour. For instance, some embodiments provide passive DC magnetic techniques and technologies wherein measurements are performed by measuring the generally DC field in the vicinity of a group of sensors.
Other embodiments provide techniques and technologies wherein the magnets of the sensors are aligned with each other (sometimes vertically) and then fixed in orientation. In such cases the orientations of the magnets can be fixed by a process involving the curing of an RTV, glue, or other material. The sensors are then placed with the orientations of the as-placed magnets in alignment with each other. If conditions re-orient the sensors the alignment of the group of magnets will be lessened and the total magnetic field associated with the group of the sensors will decrease accordingly. Thus, changes in the magnetic field of such systems can be correlated with the extent of erosion in the vicinity of the sensors.
Some embodiments provide active DC magnetic sensors within which the magnets can be remotely re-oriented to create a measureable change in their magnetic fields (relative to the environmental magnetic field) when desired. Moreover, in some embodiments, the sensors include magneto-inductive circuitry for receiving power from an external source.
Still other embodiments provide active sensors with tilt sensors, roll sensors, accelerometers, pressure sensors, and sensors for detecting conditions related to erosion (such as the movement or position and/or orientation of the sensor itself). Some sensors include a magnetometer for sensing (and reporting) the magnetic field in the vicinity of the sensors. Sensors of various embodiments can also be configured to sense and report various internal conditions such as their battery status.
In addition, or in the alternative, some embodiments provide sensors which can communicate with one another and can form a network amongst themselves. Sensors of the current embodiment measure the received signal strength of the signals from the other sensors and (in cooperation with a master sensor, receiver, etc.) determine the relative locations of the sensors in the network.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
This application is a continuation in part of U.S. patent application Ser. No. 13/104,682 entitled “Sensors For Integrated Monitoring and Mitigation of Scour,” filed on May 10, 2011 by Dr. Genda Chen et al., the entirety of which is incorporated herein as if set forth in full and which claims priority to U.S. Provisional Patent Application No. 61/333,046, filed on May 10, 2010, entitled “Sensors For Integrated Monitoring And Mitigation Of Scour,” by Dr. Genda Chen et al. the entirety of which is also incorporated herein as if set forth in full.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13104682 | May 2011 | US |
| Child | 13693139 | US |
