Abstract:
A method for initializing a chain of non-initialized data collectors is disclosed. The chain of non-initialized data collectors are coupled to a controller. In a first step communication between the controller and each data collector in the chain of non-initialized collectors is disabled, except for an active non-initialized data collector, The active non-initialized collector is coupled to the controller and any remaining non-initialized data collectors. Next, the active non-initialized data collector is initialized by assigning an identification number to the active non-initialized data collectors. The active non-initialized collector becomes an initialized data collector. Then, communication is restored between the initialized data collector and a next active non-initialized data collector in the chain of non-initialized data collectors. The method repeats until all non-initialized data collectors are initialized.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates to the field of structural health management and more specifically to a method for sensor initialization in a structural health management system.  
       BACKGROUND  
       [0002]     Nondestructive testing is a procedure for determining the quality or characteristics of a structure without permanently altering the structure or the structure&#39;s properties. Examples include ultrasonic and radiographic inspection. In the avionics field, nondestructive evaluations of airplane components are done to insure the structural integrity of the airplane. In typical nondestructive testing schemes, a certified inspector performs one or more nondestructive tests at the aircraft. This process may be repeated at regular intervals to monitor the structural health of the aircraft.  
         [0003]     While this type of nondestructive testing scheme can be effective, it may have several potential drawbacks. First, the test typically needs to be conducted by trained inspectors, which can incur significant costs, including the potential loss of operational revenue, when having an inspector perform the tests on site. Second, to enable efficient analysis and repetitive comparison over time, a non-subjective decision process driven by inspection data, inspection method parameters, location, decision criteria, and material properties within the context of the structure being inspected may be required. Current inspection approaches may not preserve these components. Although each inspection can be analyzed individually, a collection of inspections may not be analyzed in toto.  
         [0004]     To resolve some of the drawbacks of current nondestructive schemes, other structural health management schemes have been developed. In one structural health management technique, ultrasonic transducers can be placed, for example, on the fuselage of the aircraft to be tested. The ultrasonic transducers are then coupled to an onboard testing computer. The testing computer can be used to run nondestructive tests when needed by using the installed ultrasonic transducers.  
         [0005]     The above-described system allows for nondestructive testing to be done without having an inspector bring equipment to the aircraft. Additionally, the automated inspection and determination of the state of the inspected material preserves accurate location data, as well as the associated data used to perform the inspection and make the determination. This allows multiple self-referential inspections of an area over an extended period of time, enabling correlation, trending and other sophisticated analysis of the inspection data across vehicles and over time.  
         [0006]     Sensor data collectors can be used to collect the data gathered by the sensors. However, when using sensors data collectors that are interconnected on the same data bus, unless the sensor data collectors have some type of identification, the sensor data collectors can not correctly respond to a controller or processor. What is needed is a method for sensor data collector initialization.  
       BRIEF SUMMARY  
       [0007]     In an exemplary embodiment of the present a method for initializing a chain of non-initialized data collectors is disclosed. The chain of non-initialized data collectors are coupled to a controller. In a first step communication between the controller and each data collector in the chain of non-initialized collectors is disabled, except for an active non-initialized data collector, The active non-initialized collector is coupled to the controller and any remaining non-initialized data collectors. Next, the active non-initialized data collector is initialized by assigning an identification number to the active non-initialized data collectors. The active non-initialized collector becomes an initialized data collector. Then, communication is restored between the initialized data collector and a next active non-initialized data collector in the chain of non-initialized data collectors. The method repeats until all non-initialized data collectors are initialized.  
         [0008]     In another exemplary embodiment, a data collection apparatus is disclosed. The apparatus comprises two or more serially connected data collectors coupled to a controller. Each data collector comprises a data input, a data output and a switch coupling the data input and data output. The switch is configured to isolate the data input from the data output. The controller is coupled to the data input of a first data collector of the two or more data collectors.  
         [0009]     In another embodiment, the controller is configured to send a request to open the switch of the first data collector processor. The request is sent to a processor in the first data collector. The processor is configured to send an open command to the switch of the first data collector. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:  
         [0011]      FIG. 1  illustrates an exemplary structural health monitoring system in accordance with the teachings of the present invention;  
         [0012]      FIG. 2  is a block diagram of a sensor data collector in accordance with the teachings of the present invention; and  
         [0013]      FIG. 3  is a flowchart of a method for initializing sensor data collectors in a structural health management system in accordance with the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0014]     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. While the invention is discussed in an avionics embodiment, the teachings of the present invention are applicable to many different fields of endeavor.  
         [0015]      FIG. 1  illustrates an exemplary structural health management system  100  in accordance with the teachings of the present invention. Structural health management system  100  includes a plurality of sensors  104  coupled to one or more sensor data collectors (SDCs)  106 . Each sensor  104  is mounted to a structure  102  to be tested. In the embodiment as shown in  FIG. 1 , each SDC is coupled to each other by a data bus  107  and a power line  105 . The SDCs  106  are coupled to a controller  109  via the data bus  107  and the power line  105 . The controller  109  couples to at least one structural health monitoring processor  108 . Various inputs and outputs can be provided to structural health monitoring processor  108 . For example, processor  108  can be coupled to various input/output devices including a display  110 , a keyboard  112  and the like.  
         [0016]     Sensor  104  can be an ultrasonic transducer that converts electrical signals into mechanical vibrations and mechanical vibrations into electrical signals. In this embodiment, sensor  104  converts electricity into mechanical vibrations that propagate waves in the structure  102  to which the sensor  104  is coupled through elastic deformation (known as elastic waves). The propagated waves interact with various features within the structure  102  such as flaws or defects. The sensor  104  can also receive transmitted and reflected waves and convert the mechanical vibrations caused by these waves into electrical signals. These electrical signals can then be analyzed to determine if there are any flaws or defects in the structure  102 .  
         [0017]     The amount of time it takes for a wave to travel between two sensed locations is known as the time-of-flight. In addition to the time-of-flight, signal amplitude, and signal energy of an elastic wave received by a sensor  104  can be used in models to predict the underlying damage state of the area traversed by the propagated elastic wave. Various features within the structure  102 , such as fatigue cracks or other structural flaws, can be identified and located based on these values obtained from data collected by sensor  104  and others.  
         [0018]     While many different designs for sensors  104  exist, in one embodiment, sensor  104  is a piezoelectric transducer. Piezoelectric transducers produce mechanical vibrations when an electric signal is applied and produce electrical signals when receiving mechanical vibrations. Typically, piezoelectric transducers use piezoelectric ceramics that can be engineered to produce different wave modes.  
         [0019]     Different types of waves induced by piezoelectric transducers can be used in nondestructive testing. In an embodiment of the present invention, the sensor  104  produces Lamb waves in structure  102 . Lamb waves propagate throughout the entire thickness of plate-like structures, such as the composite material used for the skin of an aircraft. Lamb waves are a form of guided elastic waves distinct from the bulk waves used in a traditional ultrasonic approach. Lamb waves traverse along the plate-like structures while exciting material throughout the plate&#39;s thickness. As a consequence, the use of Lamb waves allows for distributed sensors schemes to examine the composite plate-like structure over a given area without the need to scan the transducers over certain areas.  
         [0020]     SDCs  106 , in one embodiment of the present invention, collect data from the sensors  104  in the form of electrical signals and send the data to processor  108  for evaluation. In another embodiment, SDCs  106  collect data and can perform some analysis on the data prior to sending the data to the processor  108 . By providing multiple SDCs  106 , if one SDC  106  was to fail, or otherwise become inoperative, the entire structural health management system  100  would continue to operate. Additionally, in one embodiment, SDCs  106  accept multiple sensor inputs and provide a single high speed data output, resulting in a reduction in the amount of wiring required between the sensors  104  and the processor  108 . In one embodiment, SDCs  106  are arranged as a chain of serially coupled SDCs  106 .  
         [0021]     Processor  108  can receive data from the sensors  104 , either directly or via SDCs  106 . Processor  108  can also process the data to evaluate the structural health of the structure  102 . Processor  108  can also receive data from sensors  104  and perform damage assessment analysis. Processor  108  can be a commercial off the shelf processor and any components necessary to allow processor  108  to process data. Processor  108  can couple to input/output devices such as the display  110  and keyboard  112 .  
         [0022]     Controller  109  provides commands to the SDCs  106  indicating which sensors to fire. Controller  109  can issue commands to the SDC  106  to enable power or data communication to other SDCs  106 . In one embodiment, the functionality of controller  109  can be provided by processor  108 .  
         [0023]     In one embodiment of the present invention, one controller can be coupled to multiple SDCs  106 . For example, in a chain of SDCs  106 , a controller  109  can connect directly to a first SDC  106  in the chain of SDCs  106  with the other SDCs  106  coupled serially after the first SDC  106  in the chain. In one embodiment, the controller  109  can communicate with each of the SDCs  106  coupled to the controller  109  by using an identification number uniquely associated with each of the SDCs  106  in a group. The identification numbers can be assigned by the controller  109  to each of the SDCs  106  coupled to the controller  109 .  
         [0024]     Structure  102  can be any one of numerous types of material of interest to be tested. In one embodiment, structure  102  is a composite material used for the skin of an aircraft. In one exemplary embodiment, structure  102  is a plate-like composite material such as the material used to form modern aircraft skin.  
         [0025]     Prior to performing any analysis using sensors  104 , the SDC  106  is initialized so controller  109  can properly address the correct SDC  106  when needed. A method for initializing SDCs  106  is illustrated in conjunction with  FIGS. 2-3 .  
         [0026]     An exemplary SDC  106  is shown in  FIG. 2 . SDC  106  comprises a data input  201 , a data output  203 , a power input  205  and a power output  207 . Data bus  107  couples to the data input  201 , and exits the SDC  106  at data output  203 . Power line  105  couples to the power input  205  and exits the SDC  106  at the power output  207 .  
         [0027]     Internal to SDC  106 , an internal power line  213  couples to a SDC power supply  202 , which provides power to the other components internal to SDC  106 . SDC processor  204  receives data from data bus  107  over an internal data line  215 . An SDC memory  206  can be coupled to the SDC processor  204 . The power output  207  can be decoupled from the power line  105  via a power switch  208 . Also, data output  203  can be decoupled from data bus  107  via a data switch  210 .  
         [0028]     In one embodiment, power switch  208  is under control of SDC processor  204  via a power control line  209  and data switch  210  is under the control of SDC processor  204  via a data control line  211 . While the exemplary SDC  106  illustrated in  FIG. 2  includes both the power switch  208  and the data switch  210 , in one embodiment of the present invention only the power switch  208  or the data switch  210  need be provided.  
         [0029]     SDC processor  204  along with SDC memory  206 , typically under the command of controller  109 , controls the operation of SDC sensors  104 . SDC processor  204  can collect data for storage in SDC memory  206 , for local processing, or for forwarding to processor  108 .  
         [0030]     The power switch  208  allows each SDC  106  to disable or enable power to SDCs  106  that are coupled after the power output  207 . In one embodiment power switch  208  can be disabled using a command sent by SDC processor  204  via power control line  209 . Similarly, data switch  210  allows the SDC  106  to enable or disable communication over the data bus  107  to all SDCs  106  coupled after the data output  203  of the current SDC  106 . In one embodiment, data communication can be disabled to data output  203  by opening the data switch  210  using a command sent by SDC processor  204  via data command line  211 . When the power switch  208  in the SDC  106  is open, any downstream SDC  106  will not receive power. Similarly, if the data switch  210  is open, thus decoupling any downstream SDC  106  from the data output  203  of the SDC  106  having the open data switch  210 ; the downstream SDCs  106  will not be able to receive data. Typically the SDC processor  204  sends commands to the data switch  210  and the power switch  208  under the control of controller  109 .  
         [0031]      FIG. 3  is a flowchart illustrating an exemplary method for initiating a plurality of connected SDCs  106  coupled to the controller  109  in accordance with the teachings of the present invention. In step  302 , all SDCs  106  disable the power line  105  or data bus  107  connection to downstream SDCs  106 . This is done by opening either power switch  208  or data switch  210  in each SDC  106 . The switches can be opened upon a command from the system controller  109  as a default upon an initial powering up and/or a default following a reset of the system.  
         [0032]     Next, in step  304 , the controller takes a roll-call of the SDCs  106 . In a typical embodiment a roll call is sent as a query to the SDCs  106  to reply to the controller  109 . Initially, all but one of the SDCs  106  are unable to respond because the SDCs  106  either are not powered by power line  105  or are not linked over the data bus  107  (or, in one embodiment, neither powered over power line  105  nor linked over data bus  107 ). The only SDC  106  that can respond is the first SDC  106  coupled to the system controller  109 . Then, in step  306 , the first SDC  106  that is both powered and in communication with the system controller  109  in the chain responds to the roll call and the system controller  109  assigns the SDC  106  an identification number which is stored in SDC memory  206 . The identification number can be any symbology, including electronic representations thereof, that allows the controller  109  to uniquely identify the SDC  106 .  
         [0033]     Once the first SDC  106  receives an identification number, the system controller commands the SDC  106  to enable the power line  105  or data bus  107  of the newly initialized SDC  106  by closing power switch  208  or data switch  210 . Then, in step  308 , the system controller  109  again performs a roll-call. Any SDC  106  that has already been assigned an identification number does not reply. Of course, any SDC  106  that is not currently connected to the power line  105  or data bus  107  can not reply. Thus, only one SDC  106  can reply and that is the next SDC in line after the SDC  106  that has just been assigned an identification number. In step  310 , the SDC  106  replies and in step  312 , is assigned an identification number for storage in SDC memory  206 .  
         [0034]     Then, in step  314 , it is determined if there are any more SDCs  106  that have not been assigned an identification number. If there are more SDCs  106  to be assigned an identification number, the process repeats steps  308  to  314 . After all SDCs  106  have been assigned an identification number, the method ends at step  316 .  
         [0035]     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.