Patent Publication Number: US-11047899-B2

Title: High frequency arc fault detection

Description:
BACKGROUND 
     The present disclosure relates to aircraft controllers and arc fault detection and, in particular, arc fault detection and protection for solid state power controller circuits and components on an aircraft. 
     Vehicles, such as aircraft, typically utilize one or more electronic control unit(s) (ECU) and/or Solid State Power Controllers (SSPC), various sensors, and actuators in various control applications to ensure inflight operation, provide for redundancy, and fail-operational capabilities. A primary function performed by an ECU in an aircraft application is engine and flight control, while a primary function of an SSPC is power control and distribution. The electronic control and power distribution systems, are generally interconnected by long distances of wiring routed through cable ways and provided behind various sealed wall and fuselage panels. Wiring in aircraft can be critical to proper operation and regular checks and maintenance are often essential to ensure that wires remain serviceable and in good repair. Damage to the wires can occur due to aging, accidental damage, vibration, chaffing or rubbing against mounts and other wires during flight, bending, getting wet, oily, contaminated, stamped on, or crushed, and the like. 
     However, over time and due to varied environmental conditions that wires and wire harnesses are subjected to can lead to, the wire insulation becoming more brittle and as a result, arc faults may occur. Arc faults may also be particularly difficult to detect and isolate as many arc faults may be intermittent. Moreover, in some instances, arc faults could lead to arcing, sparks and the like as possible ignition source for combustible materials. 
     Given the potential risks and concerns associated with arcing, and arc faults, various arc detection systems have therefore been developed. However arc fault detectors have been made for detecting series arcs (i.e., wire connection breaks) and for detecting parallel arcs (connections/shorts to ground). Previous arc fault detectors have been implemented by looking for changes in the load current or trying to correlate noise signals radiated or conducted from a particular load/wire. The accuracy and sensitivity of detection (especially for series arc fault detection), needs improvement, both to detect valid faults and to avoid nuisance detections and fault indications. 
     SUMMARY 
     According to one embodiment, disclosed herein is a method of identifying an arc fault in a wire operably connected between a controller and a load. The method includes operably connecting a sense wire to the wire supplied by the controller via the wire, measuring a first voltage on the wire at the load via the sense wire, measuring a second voltage on the wire at an output interface of the controller and measuring a current in the first wire. The method also includes identifying any differences between the voltage on the wire measured at the load and the second voltage on the wire measured at the output interface, ascertaining any anomalies in the current measured in the wire, and correlating the differences between the first voltage and the second voltage with any anomalies in the current to identify an arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include routing the first sense wire in parallel with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the first sense wire is a shield associated with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include routing the sense first wire with another wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the first sense wire is connected to the first wire in close proximity to the first load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include operably connecting a second sense wire to a second wire connected to a second load supplied by the controller via the second wire, measuring a third voltage on the second wire at the load via the second sense wire, measuring a fourth voltage on the second wire at a second output interface of the controller, and measuring a second current in the second wire. The method also further includes identifying any differences between the third voltage on the second wire measured at the load and the fourth voltage on the second wire measured at the second output interface, ascertaining any anomalies in the second current measured in the second wire, and correlating the differences between the third voltage and the fourth voltage with any anomalies in the second current to identify an arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the first load and the second load are the same. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include routing the first sense wire in parallel with the second wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include routing the second sense wire with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the second sense wire is connected to the second wire in close proximity to the second load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include a third wire and a third sense wire, wherein the load is a three phase load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the correlating further includes receiving a signal indicative of the envelope of the spectral content on the wire under test in a selected frequency range, receiving the signal indicative of current in the wire under test based on the measuring, applying a negative clipping function to the signal to form a positive envelope signal, and applying a derivative function to the positive envelope signal, the derivative function yielding a pulse signal indicative of changes in the positive envelope signal. If the pulse signal exceeds a first selected threshold, integrating the pulse signal to yield an accumulated pulse signal; otherwise set the accumulated pulse signal to zero. In addition, if the accumulated pulse signal exceeds a second threshold set a first flag as true indicating a selected amount of information indicative of an arc fault has been acquired. The method also includes counting the occurrences the first flag is set as true, if the count exceeds a selected third threshold, set a second flag indicating the that the spectral content as measured from the wire indicates a possible series arc fault. The method further includes filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, and accumulating instances when the measured current exhibits an interruption based on the pulses. If the accumulated instances when the measured current exhibits an interruption exceeds a fourth selected threshold a second flag indicating the that the spectral contend as measured from the wire indicates a possible series arc faults is set, then identify a series arc fault in the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the controller being further operable to execute a method of identifying an arc fault in a wire further comprising, if the accumulated pulse signal exceeds a fifth selected threshold and the count exceeds a selected sixth selected threshold, set a third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault, filtering the signal indicative of the current in the wire to formulate pulses associated with when the measured current exhibits an interruption. If the pulses exceed a seventh selected threshold, accumulating instances when the measured current exhibits an interruption based on the pulses, if the accumulated instances when the measured current exhibits an interruption exceeds an eighth selected threshold setting a fourth flag indicative of a current fault, if the third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault is set and the fourth flag indicating a sufficient current fault is set, identify a parallel arc fault for the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the receiving a signal indicative of the envelope of the spectral content on the wire under test in a selected frequency range is based on filtering the first voltage on the first wire with a bandpass filter having a selected pass band to select and retain spectral content, wherein the pass band frequency range in the range of about 10 MHz to about 40 MHz, amplifying the retained spectral content with a linear preamplifier, and identifying an envelope of the amplified retained spectral content by applying a logarithmic amplifier to the amplified retained spectral content, the envelope indicative of the RF energy content of the spectral content in the pass band. The controller includes a current sense function, the current sense function including measuring a first current in the first wire. The method also includes correlating changes in the first current with a characteristic of the amplified retained spectral content to identify an arc fault, wherein the characteristic includes a buffered envelope as a signal indicative of the amount of energy in the selected pass band frequency range. 
     Also described herein in another embodiment is system for identifying an arc fault in a wire. The system includes a controller operably connected to a first load via first wire; the controller configured to supply a current to the first load via the first wire, a first sense wire operably connected to the first wire, the first sense wire operably connected to the controller. The controller includes a voltage sense function and a current sensing function, the controller operable to execute a process to measure a first voltage on the first wire at the first load via the first sense wire, measure a second voltage on the first wire at a first output interface of the controller, and measure a first current in the first wire. The controller is also configured to identify any differences between the first voltage on the first wire measured at the first load and the second voltage on the first wire measure at the first output interface, ascertain any anomalies in the first current measured in the first wire, and correlate the differences between the first voltage and the second with any anomalies in the current to identify an arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first sense wire is routed in parallel with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first sense wire is a shield associated with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first sense wire is routed with another wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first sense wire is connected to the first wire in close proximity to the first load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a second sense wire operably connected to a second wire operably connected to a second load, the second wire supplied by the controller, the second sense wire in operable communication with the controller. The controller is also operable to execute a method to measure a third voltage on the second wire at the load via the second sense wire, measure a fourth voltage on the second wire at a second output interface of the controller, and measure a second current in the second wire. The controller is also operable to execute a method to identify any differences between the third voltage on the second wire measured at the load and the fourth voltage on the second wire measured at the second output interface, ascertain any anomalies in the second current measured in the second wire, and correlate the differences between the third voltage and the fourth voltage with any anomalies in the second current to identify an arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first load and the second load are the same. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include routing the first sense wire in parallel with the second wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include routing the second sense wire with the first wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the second sense wire is connected in close proximity to the second load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include a third wire and a third sense wire, wherein the load is a three phase load. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the correlating the differences between the first voltage and the second with any anomalies in the current to identify an arc fault in a wire further includes receiving a signal indicative of the envelope of the spectral content on the wire in a selected frequency range, receiving a signal indicative of current in the wire, applying a negative clipping function to the signal to form a positive envelope signal, and applying a derivative function to the positive envelope signal, the derivative function yielding a pulse signal indicative of changes in the positive envelope signal. The correlating the difference between the first voltage and the second also includes that if the pulse signal exceeds a first selected threshold, integrating the pulse signal to yield an accumulated pulse signal; otherwise set the accumulated pulse signal to zero, if the accumulated pulse signal exceeds a second threshold set a first flag as true indicating a selected amount of information indicative of an arc fault has been acquired, counting the occurrences when the first flag is set as true, and if the count exceeds a selected third threshold, set a second flag indicating the that the spectral content as measured from the wire indicates a possible series arc fault. The correlating the difference between the first voltage and the second also includes filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, accumulating instances when the measured current exhibits an interruption based on the pulses, and if the accumulated instances when the measured current exhibits an interruption exceeds a fourth selected threshold and the a second flag indicating the that the spectral contend as measured from the wire indicates a possible series arc faults is set, then identify a series arc fault in the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the controller further operable to execute a method of identifying an arc fault in a wire further including that if the accumulated pulse signal exceeds a fifth selected threshold and the count exceeds a selected sixth selected threshold, set a third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault, filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, if the pulses exceed a seventh selected threshold, accumulating instances when the measured current exhibits an interruption based on the pulses, if the accumulated instances when the measured current exhibits an interruption exceeds an eighth selected threshold setting a fourth flag indicative of a current fault, and if the third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault is set and the fourth flag indicating a sufficient current fault is set, identify a parallel arc fault for the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the controller receiving a signal indicative of the envelope of the spectral content on the wire in a selected frequency range further includes a voltage sense function configured to measure a voltage on the first wire, the controller operable to filter the first voltage on the first wire with a bandpass filter having a selected pass band frequency range to select and retain spectral content, amplify the retained spectral content with a linear preamplifier, identify an envelope of the amplified retained spectral content by applying a logarithmic amplifier to the amplified retained spectral content, the envelope indicative of the RF energy content of the spectral content in the pass band of the voltage on the first wire, a current sense function, the current sense function operable to measure a first current in the first wire, and correlating changes in the first current with a characteristic of the amplified retained spectral content to identify an arc fault, wherein the characteristic includes a buffered envelope as a signal indicative of the amount of energy in the selected passband frequency range. 
     Also described herein in yet another embodiment is a system for identifying an arc fault in a wire, the system comprising a controller operably connected to a first load via first wire; the controller configured to supply a current to the first load via the first wire, wherein the controller includes a voltage sense function configured to measure a voltage on the first wire, the controller operable to filter the first voltage on the first wire with a bandpass filter having a selected pass band frequency range to select and retain spectral content, amplify the retained spectral content with a linear preamplifier, and identify an envelope of the amplified retained spectral content by applying a logarithmic amplifier to the amplified retained spectral content, the envelope indicative of the RF energy content of the spectral content in the pass band of the voltage on the first wire. The controller also includes a current sense function, the current sense function operable to measure a first current in the first wire, correlating changes in the first current with a characteristic of the amplified retained spectral content to identify an arc fault, wherein the characteristic includes a buffered envelope as a signal indicative of the amount of energy in the selected passband frequency range. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include the controller operable to execute a method of identifying an arc fault in a wire comprising, receiving a signal indicative of the envelope of the spectral content on the wire in a selected frequency range, receiving a signal indicative of current in the wire, applying a negative clipping function to the signal to form a positive envelope signal and applying a derivative function to the positive envelope signal, the derivative function yielding a pulse signal indicative of changes in the positive envelope signal. If the pulse signal exceeds a first selected threshold, integrating the pulse signal to yield an accumulated pulse signal; otherwise set the accumulated pulse signal to zero, and if the accumulated pulse signal exceeds a second threshold set a first flag as true. The system further includes the controller executing a method also including counting the occurrences when the first flag is set as true, if the count exceeds a selected third threshold, set a second flag, filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, and accumulating instances when the measured current exhibits an interruption based on the pulses. If the accumulated instances when the measured current exhibits an interruption exceeds a fourth selected threshold and a second flag indicating the that the spectral contend as measured from the wire indicates a possible series arc faults is set, then identify a series arc fault in the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include the controller further operable to execute a method of identifying an arc fault in a wire further including that if the accumulated pulse signal exceeds a fifth selected threshold and the count exceeds a selected sixth selected threshold, set a third flag, filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, and if the pulses exceed a seventh selected threshold, accumulating instances when the measured current exhibits an interruption based on the pulses. The method further includes if the accumulated instances when the measured current exhibits an interruption exceeds an eighth selected threshold setting a fourth flag indicative of a current fault, and if the third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault is set and the fourth flag indicating a sufficient current fault is set, identify a parallel arc fault for the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include at least one of the first selected threshold, the second selected threshold, the third selected threshold, the fourth selected threshold, the fifth selected threshold, the sixth selected threshold, and the seventh selected threshold is based on empirical determination from test data and selected to improve the detection and reduce nuisance trips. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the pass band is in the range of at least one of: about 10 MHz to about 40 MHz; about 10 MHz to about 80 MHz; and about 10 MHz to about 150 MHz. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the negative clipping function clipping function captures only increases in RF energy and avoid reductions to the envelope signal when no noise is detected. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the first flag as true indicates a selected amount of information indicative of an arc fault has been acquired. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the second flag as true indicates that the spectral content as measured from the wire indicates a possible series arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the third flag as true indicates the that the spectral content as measured from the wire indicates a possible parallel arc fault. 
     Also described herein in yet another embodiment is a method for identifying an arc characteristic in a wire operably connected between a controller and a first load where the controller is configured to supply a current to the first load via the first wire and measure a voltage on the first wire, the controller configured to execute a method, the method including filtering the first voltage on the first wire with a bandpass filter having a selected pass band to select and retain spectral content, wherein the pass band frequency range in the range of about 10 MHz to about 40 MHz, amplifying the retained spectral content with a linear preamplifier, and identifying an envelope of the amplified retained spectral content by applying a logarithmic amplifier to the amplified retained spectral content, the envelope indicative of the RF energy content of the spectral content in the pass band. The method also includes a current sense function, the current sense function including measuring a first current in the first wire, and correlating changes in the first current with a characteristic of the amplified retained spectral content to identify an arc fault, wherein the characteristic includes a buffered envelope as a signal indicative of the amount of energy in the selected pass band frequency range. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the controller operable to execute a method of identifying an arc fault in a wire including receiving a signal indicative of the envelope of the spectral content on the wire in a selected frequency range, receiving a signal indicative of current in the wire, applying a negative clipping function to the signal to form a positive envelope signal, and applying a derivative function to the positive envelope signal, the derivative function yielding a pulse signal indicative of changes in the positive envelope signal. If the pulse signal exceeds a first selected threshold, integrating the pulse signal to yield an accumulated pulse signal; otherwise set the accumulated pulse signal to zero, if the accumulated pulse signal exceeds a second threshold set a first flag as true. In addition, the method also includes counting the occurrences when the first flag is set as true, if the count exceeds a selected third threshold, set a second flag as true, filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, accumulating instances when the measured current exhibits an interruption based on the pulses, and if the accumulated instances when the measured current exhibits an interruption exceeds a fourth selected threshold and the a second flag indicating the that the spectral contend as measured from the wire indicates a possible series arc faults is set, then identify a series arc fault in the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include the controller further operable to execute a method of identifying an arc fault in a wire further including that if the accumulated pulse signal exceeds a fifth selected threshold and the count exceeds a selected sixth selected threshold, set a third flag, filtering the signal indicative of the current in the wire to formulate a pulse associated with when the measured current exhibits an interruption, if the pulses exceed a seventh selected threshold, accumulating instances when the measured current exhibits an interruption based on the pulses, if the accumulated instances when the measured current exhibits an interruption exceeds an eighth selected threshold setting a fourth flag indicative of a current fault, if the third flag indicating the that the spectral content as measured from the wire indicates a possible parallel arc fault is set and the fourth flag indicating a sufficient current fault is set, identify a parallel arc fault for the wire. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that at least one of the first selected threshold, the second selected threshold, the third selected threshold, the fourth selected threshold, the fifth selected threshold, the sixth selected threshold, and the seventh selected threshold is based on empirical determination from test data and selected to improve the detection and reduce nuisance trips. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the pass band is in the range of at least one of: about 10 MHz to about 40 MHz; about 10 MHz to about 80 MHz; and about 10 MHz to about 150 MHz. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that the negative clipping function clipping function captures only increases in RF energy and avoid reductions to the envelope signal when no noise is detected. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the first flag as true indicates a selected amount of information indicative of an arc fault has been acquired. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the second flag as true indicates that the spectral content as measured from the wire indicates a possible series arc fault. 
     In addition to one or more of the features described above, or as an alternative, further embodiments of the method may include that setting the third flag as true indicates the that the spectral content as measured from the wire indicates a possible parallel arc fault. 
     Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the disclosure is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  depicts a simplified diagram of an aircraft with an electrical system including various controllers and aircraft wiring in accordance with an embodiment; 
         FIG. 2A  depicts a partial diagram of a SSPC system depicting a portion of a controller interfaced with a load including sense wires in accordance with an embodiment; 
         FIG. 2B  depicts a partial diagram of a SSPC system depicting a portion of a controller interfaced with a load including sense wires in accordance with an embodiment; 
         FIG. 2C  depicts a partial diagram of a SSPC system depicting a portion of a controller interfaced with a load including sense wires in accordance with an embodiment; 
         FIG. 2D  depicts a partial diagram of a SSPC system depicting a portion of a controller interfaced with a load including sense wires in accordance with an embodiment; 
         FIG. 2E  depicts a partial diagram of a SSPC system depicting a portion of a controller interfaced with a load including sense wires in accordance with an embodiment; 
         FIG. 3  depicts a simplified flowchart depicting the method of identifying an arc fault in a wire in accordance with an embodiment; 
         FIG. 4  depicts a partial diagram of a system for detecting an arc fault in a wire connected to a load in accordance with an embodiment; 
         FIG. 5A  depicts a simplified flowchart depicting the method of identifying an series arc fault in a wire in accordance with an embodiment; and 
         FIG. 5B  depicts a simplified flowchart depicting the method of identifying a parallel arc fault in a wire in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended. The following description is merely illustrative in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term controller refers to processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, an electronic processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable interfaces and components that provide the described functionality. 
     Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include an indirect “connection” and a direct “connection”. 
     In general, embodiments herein relate to an application of a method and system to identify series and parallel arc faults. Series and parallel arc faults generate a voltage across them that can be distinguished. The existence of an arc voltage is measured and used to validate the occurrence of an arc fault event. To facilitate this measurement, in an embodiment, a sense wire/connection independent of the wire carrying power to the load measures the arc voltage. The sense wire is routed out from the SSPC to the load in various ways but always referenced back to the output of the SSPC. The sense wire can be a separate wire running parallel to the wire under test, a separate wire running on a separate wire bundle and/or the shield of the wire under test, and the like. In an SSPC application, a load sense wire is monitored for arc events by measuring the voltage drop across it. A difference of potential can be measured from the point the wire reaches the load and referenced back to the output of the SSPC driving the load. 
     Advantageously, the described embodiments provide a clear indication through arc voltage detection and looking for current variations as to when a series arc fault or parallel arc fault is occurring. By routing the sense wire along an alternate path as indicated in this invention, additional protection of the fault detection is provided. 
     Referring to  FIG. 1 , an aircraft  10  is shown. Aircraft  10  includes one or more control systems shown generally as  12 . The control system  12  includes and interconnects with one or more controllers referred to generally as  16  and more specifically as  16   l ,  16   r  commonly located at or near each engine  14   l ,  14   r . Other controllers  16  such a Solid State Power Controller (SSPC)  16  are also be depicted in this instance as  16   a ,  16   b , and the like. 
     In the described embodiments, the reference numerals are annotated with an “l” or “r” to denote the left or right side of the aircraft  10  for the purpose of simplicity of description. Likewise, the annotation “a”, “b”, “n” is employed to simplify designation of a multiple enumeration of a component or element. 
     Each of the controllers  16  including engine controllers  16   r ,  16   l  and SSPC  16   a ,  16   b  are configured to receive various sensor signals from sensors referred to generally as  18  and individually as  18   a ,  18   b , . . .  18   n  all over the aircraft  10  and may also operate one or more actuators shown generally as  20 , and more specifically as  20   a ,  20   b ,  20   c , . . .  20   n  to control the operation of the engines  14   r ,  14   l , flight controls, (not shown), power systems, (not shown), and the like. The control system  12  may also be operably connected to various other components throughout the aircraft  10 , including, but not limited to other controllers  16 , control panels  24 , displays  26 , and the like. 
     With reference to  FIGS. 2A-2E , each depicting a partial block diagram of a portion of an SSPC controller  16  in accordance with one or more embodiments. 
       FIG. 2A  depicts a portion of the SSPC  16  with an arc voltage sense circuit  40 , current sense circuit  50  and a sense wire  30   a  operably connected thereto in accordance with an embodiment. In an embodiment, arc fault detection for the one or more controller(s)  16  is provided by various sense wires shown generally as  30 , and more specifically as  30   a ,  30   b ,  30   n  and independent arc voltage sense circuits  40  in the SSPC controller(s) e.g.  16  and current sense circuits denoted as  50  respectively, each integral with and connected to respective controllers  16 . In operation of an SSPC  16 , a given load denoted as  60   a  in this instance, is supplied with a power or a command signal on a selected wire  62   a , also denoted as wire under test. The SSPC  16  may include a switch or switching function as depicted by switch  64  that controls the application of the power or a command to the wire under test  62   a , which is connected to the load  60   a . The sense wire, in this instance sense wire  30   a  is operably connected to the wire under test  62   a  in close proximity to the load  60   a . The sense wire  30   a  is also operably connected to the arc sense circuit  40 . In this embodiment, the sense wire  30   a  may be a shield on the wire under test  62   a.    
     In another embodiment, as depicted in  FIG. 2B , the sense wire  30   b  may be a separate wire, routed essentially in parallel with the wire under test  62   a.    
     In an embodiment, while switch  64   b  is closed and the power or command is provided to the load  60   a , the arc sense circuit  40  monitors the voltage at the board interface output  66  of the SSPC  16  at the wire under test  62   a . The arc sense circuit  40  also monitors the voltage on the wire under test  62   a  at the load  60   a  via the sense wire  30   a . The arc sense circuit  40  compares these two voltages and any difference in voltage noted is identified as a potential arc fault. In addition, the SSPC  16  also includes a current sense circuit  50  for monitoring of the current supplied by the SSPC  16  to the load  60 . In an embodiment, the SSPC  16  monitors the current supplied to the load  60  as well. Current transients may be indicative of a fault. For example, increasing current transients may be indicative of a short circuit to ground or a short circuit to another circuit, while large decreasing current transients are indicative of breaks in the wire under test  62   a . By correlating the measured arc voltage measured differentials with the variations in the current to the load  60   a , a more robust detection of arc faults is provided. 
       FIG. 2C  depicts embodiment of a portion of the SSPC  16  with arc voltage sense circuit  40 , current sense circuit  50  and a sense wires  30   c  in accordance with another embodiment. Once again, in operation, of an SSPC  16 , a load  60   c  is supplied with a power or a command signal on a selected wire, (e.g., wire under test)  62   c  in this instance. In this embodiment, second load  60   d  is also supplied with a power or a command signal on a selected wire denoted  62   d , in this instance. That is, another power wire (and possibly a wire under test for another arc voltage sense circuit  40 ). The SSPC  16 , once again, may include switch or switching function  64   c , that controls the application of the power or a command to the wire under test  62   c  connected to the load  60   c . The sense wire, in this instance sense wire  30   c  is operably connected to the wire under test  62   c  in close proximity to the load  60   c  and to the arc sense circuit  40  as described herein. In this embodiment, the sense wire  30   c  is routed in close proximity to second power wire  62   d . In this manner, any fault likely to occur in the wire under test  62   c  is unlikely to also affect the sense wire  30   c  as it is routed in a harness with wire  62   d.    
     In this embodiment, once again while switch  64   c  is closed and the power or command is provided to the load  60   c , the arc sense circuit  40  monitors the voltage at the board interface output  66  of the SSPC  16  and on the wire under test  62   c  at the load  60   c  via the sense wire  30   c . The arc sense circuit  40  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50  monitors the current supplied by the SSPC  16  to the load  60  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   c , a more robust detection of arc faults is provided. 
       FIG. 2D  depicts another embodiment of a portion of the SSPC  16  for detecting arc faults. In this embodiment, the SSPC  16  includes arc voltage sense circuit(s)  40   e  and  40   f , current sense circuit(s)  50   e  and  50   f , and sense wire(s)  30   e  and  30   f  in accordance with another embodiment for a balanced load  60   e . In this embodiment, in operation, of an SSPC  16 , the load  60   e  is supplied with a power or a command signal on a selected wire, (e.g., wire under test)  62   e  and a second wire  62   f . That is, another power wire (and a second wire under test  62   f  for another arc voltage sense circuit denoted  40   f ). The SSPC  16 , once again, may include switch or switching function(s)  64   e , and  64   f  that control the application of the power or a command to the wire under test  62   e , and/or  62   f  respectively. A first sense wire, in this instance sense wire  30   e  is operably connected to the wire under test  62   e  in close proximity to the load  60   e  and to the arc sense circuit  40   e  as described herein. In this embodiment, the sense wire  30   e  is routed in close proximity to second power wire  62   f . In this manner, any fault likely to occur in the wire under test  62   e  is unlikely to also affect the sense wire  30   e  as it is routed in a harness with wire  62   f . Similarly, a second sense wire, in this instance sense wire  30   f  is operably connected to the wire under test  62   e  in close proximity to the load  60   e  and to the arc sense circuit  40   f  as described herein. In this embodiment, the sense wire  30   f  is routed in close proximity to first power wire i.e., wire under test  62   e . In this manner, any fault likely to occur in the wire under test  62   f  is unlikely to also affect the sense wire  30   f  as it is routed in a harness with wire  62   e.    
     In this embodiment, once again while switch  64   e  is closed and the power or command is provided to the load  60   e , the arc sense circuit  40   e  monitors the voltage at the board interface output  66   e  of the SSPC  16  at the wire under test  62   e . The arc sense circuit  40   e  also monitors the voltage on the wire under test  62   e  at the load  60   e  via the sense wire  30   e . The arc sense circuit  40  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50   e  monitors the current supplied by the SSPC  16  to the load  60   e  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   e , a more robust detection of arc faults is provided. Likewise, for the other half of the circuit, while switch  64   f  is closed and the power or command is provided to the load  60   e  via wire  64   f , the arc sense circuit  40   f  monitors the voltage at the board interface output  66   f  of the SSPC  16  at the wire under test  62   f . The arc sense circuit  40   f  also monitors the voltage on the wire under test  62   f  at the load  60   e  via the sense wire  30   f . The arc sense circuit  40   f  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50   f  monitors the current supplied by the SSPC  16  to the load  60   e  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   e , a more robust detection of arc faults is provided. 
       FIG. 2E  depicts another embodiment of a portion of the SSPC  16  for detecting arc faults for a three phase load. In this embodiment, the SSPC  16  includes arc voltage sense circuit(s)  40   g    40   h  and  40   i , current sense circuit(s)  50   g ,  50   h , and  50   i , and sense wire(s)  30   g ,  30   h , and  30   i  in accordance with another embodiment for a three phase load denoted  60   g . In this embodiment, in operation, of an SSPC  16 , the load  60   g  is supplied with a power or a command signal on a selected wire, (e.g., wire under test)  62   g , a second wire  62   h , and a third wire  62   i . That is, three wire(s) under test denoted  62   g ,  62   h , and  62   i  respectively for another arc voltage sense circuit denoted  40   g ,  40   h , and  40   i  respectively. The SSPC  16 , once again, may include switch or switching function(s)  64   g ,  64   h , and  64   i  that each respectively control the application of the power or a command to the wire(s) under test  62   g ,  62   h , and/or  62   i  respectively. 
     A first sense wire, in this instance sense wire  30   g  is operably connected to the wire under test  62   g  in close proximity to the load  60   e  and to the arc sense circuit  40   g  as described herein. In this embodiment, the sense wire  30   g  is routed in close proximity to a second power wire  62   h  as described in the other embodiments herein. In this manner, any fault likely to occur in the wire under test  62   g  is unlikely to also affect the sense wire  30   g  as it is routed in a harness with wire  62   h . Similarly, a second sense wire, in this instance sense wire  30   h  is operably connected to the wire under test  62   h  in close proximity to the load  60   e  and to the arc sense circuit  40   h  as described herein. In this embodiment, the sense wire  30   f  is routed in close proximity to a third power wire, i.e., wire under test  62   i . In this manner, any fault likely to occur in the wire under test  62   h  is unlikely to also affect the sense wire  30   h  as it is routed in a harness with wire  62   i.    
     Furthermore, in this embodiment, a third sense wire, in this instance sense wire  30   i  is operably connected to the wire under test  62   i  in close proximity to the load  60   e  and to the arc sense circuit  40   i  as described herein. In this embodiment, the sense wire  30   i  is routed in close proximity to the first power wire, i.e., wire under test  62   g . In this manner, any fault likely to occur in the wire under test  62   i  is unlikely to also affect the sense wire  30   i  as it is routed in a harness with wire  62   g . It should be appreciated that the sense wires could be the shields or separates sense wires associated with the wires under test  62   g ,  62   h ,  62   i  routed with the wires under test  62   g ,  62   h ,  62   i . In addition, it should also be appreciated that the sense wires  30   g ,  30   h ,  30   i  could also be routed the another of the threes wires under test  62   g ,  62   h , and  62   i . For example, instead of the sense wire  30   g  being routed with wire under test  62   h  as described herein, it could instead be routed with wire under test  62   i . Likewise for the sense wires  62   h  and  62   i  each could be routed with a different wire under test than identified above. 
     In this embodiment, once again while the switch  64   g  is closed and the power or command is provided to the load  60   e , the arc sense circuit  40   g  monitors the voltage at the board interface output  66   g  of the SSPC  16  at the wire under test  62   g . The arc sense circuit  40   g  also monitors the voltage on the wire under test  62   g  at the load  60   g  via the sense wire  30   g . The arc sense circuit  40   g  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50   g  monitors the current supplied by the SSPC  16  to the load  60   g  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   g , a more robust detection of arc faults is provided. Likewise, for the second part of the circuit, while switch  64   h  is closed and the power or command is provided to the load  60   e  via wire  62   h , the arc sense circuit  40   h  monitors the voltage at the controller  16  board interface output  66   h  of the SSPC  16  at the wire under test  62   h . The arc sense circuit  40   h  also monitors the voltage on the wire under test  62   h  at the load  60   g  via the sense wire  30   h . The arc sense circuit  40   h  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50   h  monitors the current supplied by the SSPC  16  to the load  60   g  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   g , a more robust detection of arc faults is provided. Finally, for the third part of the circuit, while switch  64   i  is closed and the power or command is provided to the load  60   e  via wire  62   i , the arc sense circuit  40   i  monitors the voltage at the board interface output  66   i  of the SSPC  16  at the wire under test  62   i . The arc sense circuit  40   h  also monitors the voltage on the wire under test  62   i  at the load  60   g  via the sense wire  30   i . The arc sense circuit  40   i  compares these two voltages and any difference in voltage noted is identified as a potential arc fault as described herein. In addition, the current sense circuit  50   i  monitors the current supplied by the SSPC  16  to the load  60   g  for current transients as described herein. Once again, by correlating the measured arc voltage measured differentials with the variations in the current to the load  60   g , a more robust detection of arc faults is provided. It should be appreciated that in a standard three-phase power application, switches  64   g ,  64   h , and  64   i  would, as a matter of practice and implementation be opened or closed simultaneously, though it need not necessarily be the case. 
       FIG. 3  depicts a flowchart of a method  200  of detecting arc faults in a control system with a controller  16  supplying power or a control system to a load  60  in accordance with an embodiment. The description on  FIG. 3  will refer, from time to time, to elements in  FIGS. 1 and 2 . Turning to the method  200 , the method  200  initiates at process block  205  where a sense wire  30  is operably connected to a wire under test  62  in close proximity to a load  60 . At process step  210  the method  200  continues with measuring a voltage on a wire under test  62  at the load  60  via the sense wire  30 . The method also includes measuring a voltage on the wire under test  62  at an interface output  66  to the controller  16  as depicted at process step  215 . In addition, the method  200  includes measuring a current supplied to the load  60  as depicted at process step  220 . The methods  200  continues with identifying differences between the voltage on the wire under test  62  measured at the load  60  and the voltage on the wire under test  62  measured at the output interface  66  as depicted at process step  225 . Furthermore, the method  200  also includes ascertaining any anomalies in the current measured in the wire under test  62  as depicted at process step  230 . Anomalies can include transients, large variations spikes and the like. At process step  235 , the method  200  concludes with correlating any differences in the measured voltages with any current anomalies ascertained to identify an arc fault. 
     It should be appreciated that while previous methods have worked satisfactorily for parallel arc fault detection (e.g., short to ground or another circuit), they and not very satisfactory for series arc fault detection. Advantageously the described embodiments improve on prior detection techniques by coupling the differential voltage tests of the arc voltage sense circuit  40  with the measured current variations from the current sense circuit  50 . Moreover, it should also be noted that the existing methods associated with detecting current variations work less effectively as the line voltage increases (for example for 270 VDC power vs 28 VDC power). Finally, by routing the sense wire  30   a  along an alternate path as indicated in selected embodiments, additional protection of the fault detection is provided. Any fault will be less likely to affect the power wire, e.g. the wire under test  62  and sense wire  30  at the same time. 
       FIG. 4  depicts a simplified block diagram of another system and process as part of controller  16  for detecting arc faults in accordance with an embodiment. In an embodiment, the voltage on the wire under test  62  is monitored by an arc fault sense circuit  40  as part of the controller  16 . In an embodiment, the voltage is monitored at the controller output interface  66  as described herein. 
     Series and parallel arcs faults have been found to create radio frequency (RF) noise over a wide spectral range of about 1 Mhz to 150 Mhz, but in particular in the range of 10 Mhz to about 40 Mhz. The described embodiments of an arc fault detection circuit  40  employ a filter  42  feeding a one stage preamplifier  44  that then is directed to an RF detector  46  and finally to an output buffer  48 . Then the output of this circuit is fed into the processor of the controller  16  for monitoring. In an embodiment, the filter  42  is an RF band pass filter with a band pass range of about 10 MHz to 40 MHz, although other ranges are possible. The range is selected to correspond with the spectral content exhibited by the arc fault conducted on the wire under test  62 . To facilitate monitoring and further processing the arc fault detection circuit  40  also includes a preamplifier  44  to amplify the filtered spectral content. In an embodiment, a standard RF amplifier may be employed provided it exhibits sufficient operational bandwidth and linearity. The preamplifier  44  may also contain a filter network to help select the appropriate frequency bands for monitoring. An RF Detector circuit  46  includes a standardized logarithmic amplifier  46  to further amplify the RF content gleaned from the measured voltage data from the wire under test  62  and glean additional information regarding the signal strength in the frequency range of interest. The logarithmic amplifiers exhibits an output that represents a many-decade high dynamic range of high-frequency input signal amplitudes by a relatively narrow output range signal, thereby correlating to the “energy” in the high frequency content of the information in band pass range. This information is then buffered by a buffer amplifier  48  and then provided to the microprocessor of the controller  16  for processing in accordance with one or more detections methods. 
     In the microprocessor additional software logic may be used to look for specific time domain characteristics of the arc such as length of time for detected noise and repeating patterns. The described embodiments provide a clear indication through RF detection as to when a series arc fault or parallel arc fault is occurring. In one embodiment, when the output of the detection circuit  40  exceeds a selected threshold, it is construed as the presence of an arc fault. In another embodiment, the output of the arc fault detection circuit  40  can be correlated with the detected transients from the current sense circuit  50  to identify the presence of an arc fault with improved accuracy and reliability when compared to existing techniques. It should also be noted that advantageously, the described embodiments do not depend on current droop on series arc faults and are more immune to the effects of higher voltages as it directly detects the signature noise from the arc itself. In addition, the detection circuit is small and low cost and readily implemented in a hardware preprocessing configuration. 
       FIG. 5A  depicts another flowchart of a method  500  of detecting arc faults in a control system with a controller  16  supplying power or control signals to a load  60  via a wire under test  62  in accordance with an embodiment. The description on  FIG. 5  will refer, from time to time, to elements in  FIGS. 1-4 . The various constants and filter time constants for both  FIGS. 5 a  and 5 b    are empirically derived experimentally by looking at the characteristics of captured test data for currents and RF energy and their waveforms. For example, the ‘integrate above threshold value’ is selected to ignore low level noise from the circuit and from A/D sampling. 
     The method  500  initiates with system and processes described with respect to  FIG. 4  and identifying the relevant RF content and current sensing. In this embodiment, the method  500  initiates at process block  505  with receiving, by the processor of the controller  16  signals indicative of relevant RF measurements and spectral content from the wire under test  62  (e.g. the output  49  of buffer amplifier  48  ( FIG. 4 )). Similarly, the process  500  also includes receiving a signal indicative of the current measurements from the current sensing circuit  50  ( FIG. 4 ) as described herein at process step  510 . At process step  515  the method  500  continues with a negative clipping function. The negative clipping function is configured to simplify further processing by limiting the sign of the spectral content envelope signals from the RF detector circuit  46  ( FIG. 4 ) to positive values. The negative clipping function captures only increases in RF energy and ensures avoiding inadvertently decaying the result of the following accumulation during times when no noise is detected, which, in turn, ensures that the accumulation integrator to have the right decay time constant. The method  500  continues at process step  520  with applying a filter derivative to identify changes in the RF content of the process voltage from the wire under test  62 . The derivative identifies the changes in the original spectral content and in particular, whether the frequency band of interest (10 Mhz to 50 Mhz) has had a significant positive change in amplitude. This feature captures the changing amplitude of noise that occurs during a typical arcing process and differentiates it from constant background noise. At process step  525 , the changes that are identified by the derivative function at process step  520  are integrated above a selected threshold. The integration establishes and accumulates difference pulses above an established selected threshold. The threshold defines a limit for circuit sampling DC noise at the A/D thus only detecting significant RF content changes in the integration. Continuing with  FIG. 5  and the method  500 , at process step  530 , the resulting pulses that exceed another selected threshold are evaluated, flagged and counted as shown at process step  535 . If the count of flags (pulses that exceeded the threshold) accumulates such that it exceeds another selected threshold, it is indicative of the spectral content from the RF detection  42  ( FIG. 4 ) as depicted at process step  540  meeting selected characteristics indicative of an arc fault. 
     Continuing with  FIG. 5A  and the current sense branch of the flow chart, the current in the wire under test  62  as measured by the current sense circuit  50  is received at block  510 . This measured current is received at process step  545 , which provides a high frequency filtering function that formulates a pulse for instances where the measured current exhibits partial dropouts. That is, in instances where measured transient breaks in the current delivered to the wire under test  62 . At process step  550  the pulses are integrated to establish pulses indicative of the instances of the current drop outs. Finally, turning to process block  555 , if the flag from process step  540  is set indicating the presence of the selected RF signature on the wire under test  62  exceeding the selected threshold, and the cumulative pulses from process block  550  exceed a selected threshold, indicating that the sensed current is indicative of a potential fault, then a series arc fault is indicated by process block  555 . 
     Turning to  FIG. 5B  and the description of the method  500  continues with the process steps for detecting parallel arc faults. The method  500  continues at process blocks  560  with receiving the integrated, accumulated pulses and the pulse count from process steps  525  and  535  respectively indicative of relevant RF measurements and spectral content from the wire under test  62 . If the value of the integrated, accumulated pulses exceeds a selected threshold and the pulse count from process step  535  exceeds another selected threshold, then a true flag is set indicating a potential arc fault condition has been detected. Meanwhile, at process step  570 , the current received from the current sense circuit  50  is differentiated and then subsequently integrated to accumulate all instances of current transients. Once again, as depicted at process step  575 , if the accumulated instances of current transients exceeds a selected threshold a true flag is set for the current tests. Finally, turning to process block  580  if the flag from process step  560  is set indicating the presence of the selected RF signature on the wire under test  62  exceeding the selected threshold, and the cumulative pulses from process block  575  exceed a selected threshold, indicating that the sensed current is indicative of a potential fault, then a parallel arc fault is indicated. 
     It should be appreciated that the methodologies described with respect to  FIGS. 5A and 5B  may readily be applied to the embodiments employing sense wires ad described herein. In those instances, the processing may be part of the correlation between the voltage measured in the sense wires and the current in the wire under test. Furthermore, it should further be appreciated that various embodiments as described herein may be combined in whole or in part with other embodiments to facilitate various implementations for detecting and identifying both series and parallel arc faults. It should also be appreciated, that each of the selected thresholds may be selected based on actual measurements of various arc configurations and selected to “optimize” the detection and minimize nuisance tripping based on false positive determinations. It should also be appreciated that in the described embodiments, this optimization is accomplished to center the results between the point where excess noise would be picked up and the point where the actual arc would not be detected. The various constants and filter time constants may empirically derived experimentally based on the characteristics of captured test data for measured voltages on the sense wires or wires under test as well as the currents and RF energy and their waveforms. For example, the ‘integrate above threshold value’ is selected to ignore low level noise from the circuit and from A/D sampling employed in the processing. In another example, the filter derivative time constant is selected to allow closely spaced RF pulses to be later counted together but to filter out pulses that are spaced widely apart. Likewise, the pulse detect is selected as a threshold to see adequate RF energy to consider it a true pulse. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. For the purposes of this disclosure, it is further understood that the terms “inboard” and “outboard” can be used interchangeably, unless context dictates otherwise. 
     The present embodiments may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure. 
     The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted, that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.