Patent Publication Number: US-11385632-B2

Title: Sensor fault detection and identification using residual failure pattern recognition

Description:
FIELD 
     The present disclosure relates to sensor fault detection and identification. In particular, the present disclosure relates to sensor fault detection and identification using residual failure pattern recognition. 
     BACKGROUND 
     Currently, aircraft pitot tubes are prone to measurement failure due to icing blockage, heavy water ingestion, volcanic ash blockage, etc. A common mode pneumatic event (CMPE) occurs when a majority of the pitot tubes on the airplane are blocked simultaneously. When a CMPE occurs, the display airspeed, which is displayed on the cockpit display, will be corrupted. In addition, the aircraft flight control system, which has a certain window of time of exposure to the corrupted airspeed, may cause the airplane to deviate from its optimal flight path. 
     In light of the foregoing, there is a need for an improved technology for sensor fault detection and identification of sensor measurement failures (e.g., airspeed, angle of attack, acceleration, etc.) on aircraft. 
     SUMMARY 
     The present disclosure relates to a method, system, and apparatus for sensor fault detection and identification using residual failure pattern recognition. In one or more embodiments, a method for sensor fault detection and identification for a vehicle comprises sensing, with sensors located on the vehicle, data. In one or more embodiments, the data comprises m number types of data. In at least one embodiment, m is an integer greater than two. The method further comprises performing, by at least one processor, majority voting on the data for each of the types of data to generate a single voted value for each of the types of data. Also, the method comprises generating, by at least one processor, for each of the types of data, estimated values by using at least some of the voted values. In some embodiments, m number of estimated values are generated by using n number of the voted values, where n is equal to m minus one. In addition, the method comprises generating, by at least one processor, residuals by comparing the estimated values to the voted values. Further, the method comprises analyzing, by at least one processor, a pattern of the residuals to determine which of the types of the data is erroneous to detect and identify a fault experienced by at least one of the sensors on the vehicle. 
     In one or more embodiments, the data comprises measurement data. In at least one embodiment, the sensors comprise at least two (2) of: a pitot tube, a pitot-static tube, a static port, a static tube, an angle of attack (AOA) resolver, or an accelerometer. In some embodiments, the types of data comprise at least three (3) of: total pressure, static pressure, angle of attack (AOA), or acceleration. 
     In at least one embodiment, the vehicle is an airborne vehicle, a terrestrial vehicle, or a marine vehicle. In some embodiments, the airborne vehicle is an airplane, an unmanned aerial vehicle (UAV), or a helicopter. 
     In one or more embodiments, the method further comprises removing, by at least one processor, known corruption effects from at least some of the data. In some embodiments, the known corruption effects are removed by at least one processor by utilizing dynamic pressure, Mach number, angle of attack (AOA), flap position, gear position, excess thrust, and/or ground effect terms. 
     In at least one embodiment, at least one processor generates the estimated values by utilizing at least one statistical filter. In some embodiments, at least one statistical filter is an extended Kalman filter (EKF). 
     In one or more embodiments, the method further comprises generating, by at least one processor, an alert signal indicating which of the types of data is erroneous and/or which type of the sensors are experiencing a failure. In some embodiments, the method further comprises generating a visual alert and/or an audible alert based on information contained in the alert signal. 
     In at least one embodiment, the method further comprises generating, by at least one processor, a synthetic data signal indicating to use synthetic data instead of erroneous sensed data. 
     In at least one embodiment, a system for sensor fault detection and identification for a vehicle comprises sensors, located on the vehicle, to sense data. In one or more embodiments, the data comprises m number types of data. In some embodiments, m is an integer greater than two. The system further comprises at least one processor configured to perform majority voting on the data for each of the types of data to generate a single voted value for each of the types of data; to generate for each of the types of data, m number of estimated values by using n number of the voted values, where n is equal to m minus one; to generate residuals by comparing the estimated values to the voted values; and to analyze a pattern of the residuals to determine which of the types of the data is erroneous to detect and identify a fault experienced by at least one of the sensors on the vehicle. 
     In one or more embodiments, at least one processor is further configured to remove known corruption effects from at least some of the data. In at least one embodiment, at least one processor is further configured to generate the estimated values by utilizing at least one statistical filter. In some embodiments, at least one statistical filter is an extended Kalman filter (EKF). In one or more embodiments, at least on processor is further configured to generate an alert signal indicating which of the types of data is erroneous and/or which type of the sensors are experiencing a failure. 
     In at least one embodiment, the system further comprises: at least one indicator light to generate a visual alert based on information contained in the alert signal, at least one display to display a visual display alert based on the information contained in the alert signal, and/or at least one speaker to generate an audio alert based on the information contained in the alert signal. 
     In one or more embodiments, at least one processor is further configured to generate a synthetic data signal indicating to use synthetic data instead of erroneous sensed data. 
     The features, functions, and advantages can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1A  is a diagram showing a vehicle (e.g., an airplane) that may be employed by the disclosed system for sensor fault detection and identification for a vehicle, where the vehicle is shown to comprise various different types of sensors, in accordance with at least one embodiment of the present disclosure. 
         FIG. 1B  is a diagram showing a vehicle (e.g., an airplane) that may be employed by the disclosed system for sensor fault detection and identification for a vehicle, where the vehicle is shown to comprise a plurality of units utilized for generating an alert, in accordance with at least one embodiment of the present disclosure. 
         FIG. 2A  is a diagram showing an exemplary pitot tube that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 2B  is a diagram showing an exemplary static tube that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 2C  is a diagram showing an exemplary pitot-static tube that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 3  is a block diagram showing the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 4  is a block diagram showing details of the functionality of the synthetic air data and common mode monitor (CMM) of  FIG. 3 , in accordance with at least one embodiment of the present disclosure. 
         FIG. 5  shows equations for generating the estimated values utilized by the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 6A  shows exemplary graphs illustrating the sensed data (i.e. measured data) and the corresponding real values (i.e. truth values) for four different types of sensor data, where none of the sensed data is erroneous, in accordance with at least one embodiment of the present disclosure. 
         FIG. 6B  shows exemplary graphs illustrating the estimated values (i.e. synthetic values) generated by the disclosed system for sensor fault detection and identification for a vehicle, where none of the sensed data is erroneous, in accordance with at least one embodiment of the present disclosure. 
         FIG. 7A  shows exemplary graphs illustrating the sensed data (i.e. measured data) and the corresponding real values (i.e. truth values) for four different types of sensor data, where one of the types of sensed data (i.e. total pressure (P T )) is erroneous, in accordance with at least one embodiment of the present disclosure. 
         FIG. 7B  shows exemplary graphs illustrating the estimated values (i.e. synthetic values) generated by the disclosed system for sensor fault detection and identification for a vehicle, where one of the types of sensed data (i.e. total pressure (P T )) is erroneous, in accordance with at least one embodiment of the present disclosure. 
         FIG. 8  shows equations for the fault detection logic utilized by the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 9  is a diagram showing how the residuals are generated by the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIG. 10  is a chart showing an exemplary expected pattern of residuals utilized by the disclosed system for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
         FIGS. 11A and 11B  together form a flow chart showing the disclosed method for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. 
     
    
    
     DESCRIPTION 
     The methods and apparatus disclosed herein provide an operative system for sensor fault detection and identification using residual failure pattern recognition. In one or more embodiments, the system of the present disclosure allows for sensor fault detection and identification by detecting erroneous sensor measurement data (e.g., total pressure, static pressure, angle of attack (AOA), and acceleration) produced by failed sensors (e.g., pitot tubes, static ports, AOA resolvers, and accelerometers) on the vehicle (e.g., aircraft). 
     In particular, the system of the present disclosure provides multi-sensor fault detection and identification by using a statistical filter (e.g., an extended Kalman filter (EKF)) architecture. Specifically, an array of statistical filters (e.g., extended Kalman filters (EKFs)) is utilized to compute different synthetic parameters (e.g., estimated values) for sensor health monitoring. In addition, the system leverages a pattern of residual characteristics (e.g., residuals) to identify which type of sensor (e.g., pitot tube, static port, AOA resolver, or accelerometer) failure has occurred on the vehicle in real-time. 
     The system of the present disclosure possesses a number of benefits. Firstly, the system has the ability to directly monitor the total pressure (P T ) and static pressure (P S ) sensor measurements by using the statistical filters&#39; (e.g., EKFs&#39;) synthetic total pressure (P T ) and static pressure (P S ). Secondly, the system is able to provide a timely sensor failure detection that allows for the aircraft flight control system to provide an accurate, reliable flight deck engine-indicating and crew-alert system (EICAS) warning message to the pilots about which failure in the system has occurred and to discourage the pilots from performing an aggressive airplane maneuver. And, thirdly, the system is able to provide an accurate sensor failure identification that allows for the aircraft flight control system to continue operation by switching over to use the synthetic version of the erroneous measurement. 
     In the following description, numerous details are set forth in order to provide a more thorough description of the system. It will be apparent, however, to one skilled in the art, that the disclosed system may be practiced without these specific details. In the other instances, well known features have not been described in detail, so as not to unnecessarily obscure the system. 
     Embodiments of the present disclosure may be described herein in terms of functional and/or logical components and various processing steps. It should be appreciated that such components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of the present disclosure may employ various integrated circuit components (e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like), which may carry out a variety of functions under the control of one or more processors, microprocessors, or other control devices. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with other components, and that the systems described herein are merely example embodiments of the present disclosure. 
     For the sake of brevity, conventional techniques and components related to sensors, and other functional aspects of the system (and the individual operating components of the systems) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in one or more embodiments of the present disclosure. 
     In various embodiments, the disclosed system for sensor fault detection and identification is employed in an airplane. It should be noted that the disclosed system for sensor fault detection and identification may be employed by other vehicles other than an airplane as disclosed herein. The following discussion is thus directed to airplanes without loss of generality. 
       FIG. 1A  is a diagram  100  showing a vehicle (e.g., an airplane)  110  that may be employed by the disclosed system for sensor fault detection and identification for a vehicle  110 , where the vehicle  110  is shown to comprise various different types of sensors, in accordance with at least one embodiment of the present disclosure. In this figure, the vehicle  110  is shown to be an airplane. However, in other embodiments, various different types of vehicles may be employed for the vehicle  110  of the disclosed system. In one or more embodiments, the disclosed system may employ an airborne vehicle, a terrestrial vehicle, or a marine vehicle for the vehicle  110 . In one or more embodiments, various different types of airborne vehicles may be employed for the vehicle  110  including, but not limited to, an airplane (as shown in  FIG. 1A ), an unmanned aerial vehicle (UAV), or a helicopter. 
     Also in this figure, the vehicle  110  is shown to comprise a number of different types of sensors. These sensors include pitot tubes  120 , a static port  130 , angle of attack (AOA) resolvers  140 , and an accelerometer  150 . It should be noted that the pitot tubes  120 , static port  130 , and AOA revolvers  140  are located on the surface of the vehicle (e.g., airplane)  110 , and the accelerometer  150  is located internal to the vehicle (e.g., airplane)  110 . These sensors sense different types of measurement data. For example, the pitot tubes  120  sense total pressure (P T ), the static port  130  senses static pressure (P S ), the AOA resolvers  140  sense AOA (α), and the accelerometer  150  senses acceleration (A N ). 
     In addition, it should be noted that, in one or more embodiments, the vehicle  110  may comprise more or less than the number of sensors as shown. For example, the vehicle  110  is shown to comprise three pitot tubes  120 . In other embodiments, the vehicle  110  may comprise more or less pitot tubes  120  than three pitot tubes  120  as is shown in  FIG. 1A . 
     Additionally, it should be noted that the vehicle  110  may comprise different types of sensors than the sensors as shown. As such, it should be understood that the types of sensors shown in  FIG. 1A  are merely example types of sensors that may be employed by the disclosed system. It follows that when utilizing different types of sensors, different types of sensor measurement data will be sensed. The disclosed system may operate utilizing different types of sensor measurement data than the types of sensor measurement data discussed herein. 
       FIG. 1B  is a diagram  160  showing a vehicle (e.g., an airplane)  110  that may be employed by the disclosed system for sensor fault detection and identification for a vehicle  110 , where the vehicle  110  is shown to comprise a plurality of units utilized for generating an alert, in accordance with at least one embodiment of the present disclosure. In this figure, the vehicle  110  is shown to additionally comprise a processor(s)  170  connected via wire  180  to a speaker  190 , a display  191 , and an indicator light  192 . The processor(s)  170  may be located within the electronics area (e.g., electronics bay) of the vehicle (e.g., airplane)  110 ; and the speaker  190 , display (e.g., a display screen)  191 , and indicator light  192  may be located within the driver&#39;s (e.g., pilot&#39;s) area (e.g., cockpit) of the vehicle  110 . 
     The vehicle  110  is also shown to additionally comprise a flight control system  195 . The flight control system  195  may be located within the electronics area (e.g., electronics bay) of the vehicle (e.g., airplane)  110 . The flight control system  195  is connected to the processor(s)  170  via wire  197 . 
     It should be noted that in other embodiments, the processor(s)  170  may be connected to the speaker  190 , the display  191 , and the indicator light  192  wirelessly. In addition, in other embodiments, the vehicle  110  may comprise more than one processor(s)  170 , more than one speaker  190 , more than one display  191 , and/or more than one indicator light  192  as is shown. Also, it should be noted that the sensors (e.g., pitot tubes  120 , a static port  130 , angle of attack (AOA) resolvers  140 , and an accelerometer  150 ) may be connected to the processor(s)  170  via wire and/or wirelessly. 
     During operation of the disclosed system, while the vehicle is operating, the processor(s)  170  receives data (e.g., sensor measurement data) from the different types of sensors (e.g., pitot tubes  120 , a static port  130 , angle of attack (AOA) resolvers  140 , and an accelerometer  150 ) on the vehicle  110 . The processor(s)  170  analyzes the data and determines whether one of the types of data (e.g., total pressure (P T ), static pressure (P S ), AOA (α), or the acceleration (A N )) measured is erroneous. If the processor(s)  170  determines that one of the types of data is erroneous, meaning the erroneous data&#39;s associated sensor has failed, the processor(s)  170  generates an alert signal to alert the driver (e.g., pilot) of the erroneous sensor measurement data and/or sensor failure. The alert signal indicates which type of data is erroneous (e.g., total pressure (P T ) measured data is erroneous) and/or indicates which type of the sensors is experiencing a failure (e.g., the pitot tubes  120  are experiencing a failure (e.g., from being blocked by icing)). 
     After the processor(s)  170  has generated an alert signal, the processor(s)  170  transmits the alert signal via wire  180  (or wirelessly) to the speaker  190 , the display  191 , and/or the indicator light  192 . In one or more embodiments, once the speaker  190  receives the alert signal, the speaker  190  will produce an audio alert, which may be an alarm tone and/or a verbal alert message describing the specific type of erroneous data and/or the specific type of sensor that has failed. In some embodiments, when the display  191  receives the alert signal, the display  191  will display to the driver (e.g., a pilot) a visual display alert, which may be a visual alert symbol, color, and/or a textual alert message describing the specific type of erroneous data and/or the specific type of sensor that has failed. In at least one embodiment, after the indicator light  192  receives the alert signal, the indicator light  192  will illuminate and/or change illumination color (e.g., change its color to red) to visually alert the driver (e.g., a pilot) of the vehicle  110 . 
     In addition, when the processor(s)  170  determines that one of the types of data is erroneous, meaning the erroneous data&#39;s associated sensor has failed, the processor(s)  170  generates a synthetic data signal indicating to use synthetic data instead of the erroneous sensed data. After the processor(s)  170  has generated the synthetic data signal, the processor(s)  170  transmits the synthetic data signal via wire  197  (or wirelessly) to the flight control system  195 . Once the flight control system  195  receives the synthetic data signal, the flight control system  195  will utilize the synthetic data instead of the erroneous sensed data for its flight computations. 
       FIG. 2A  is a diagram  200  showing an exemplary pitot tube  120  that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. In this figure, an example pitot tube  120  is shown. The pitot tube  120  in  FIG. 2A  is shown to have one opening on its end. Pitot pressure is obtained from the pitot tube  120 . The pitot pressure is a measure of ram air pressure (i.e. the air pressure created by vehicle motion or the air ramming into the tube), which under ideal conditions is equal to stagnation pressure (also referred to as total pressure (P T )). The pitot tube  120  may be employed by the disclosed system to obtain total pressure (P T ). 
     The pitot tube  120  is most often located on the wing or front section of an aircraft facing forward, where its opening is exposed to the relative wind. By situating the pitot tube  120  in such a location, the ram air pressure is more accurately measured since it will be less distorted by the aircraft&#39;s structure. When airspeed increases, the ram air pressure is increased, which can be translated by the airspeed indicator. 
       FIG. 2B  is a diagram  250  showing an exemplary static tube  210  that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. In this figure, an example static tube  210  is shown. The static tube  210  of  FIG. 2B  is shown to have two openings, which are located on the top side and bottom side of the static tube  210 . The static tube  210  obtains static pressure (P S ) similar to a static port  130  (refer to  FIG. 1A ). The static tube  210  and/or the static port  130  may be employed by the disclosed system to obtain static pressure (P S ). 
     A static port  130  (refer to  FIG. 1A ) is most often a flush-mounted hole on the fuselage of an aircraft, and is located where it can access the air flow in a relatively undisturbed area. Some aircraft may have a single static port, while others may have more than one. In situations where an aircraft has more than one static port  130 , there is usually one located on each side of the fuselage. With this positioning, an average pressure can be taken, which allows for more accurate readings in specific flight situations. An alternative static port  130  may be located inside the cabin of the aircraft as a backup for when the external static port(s)  130  are blocked. 
       FIG. 2C  is a diagram  230  showing an exemplary pitot-static tube  220  that may be employed for one of the sensors of the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. In this figure, an example pitot-static tube  220  is shown. The pitot-static tube  220  of  FIG. 2C  is shown to have three openings, which are located on the end of the pitot-static tube  220 , and on the top side and bottom side of the pitot-static tube  220 . A pitot-static tube  220  effectively integrates static ports into a pitot probe. It also incorporates a second coaxial tube (or tubes) with pressure sampling holes on the sides of the probe, outside the direct airflow, to measure the static pressure (P S ). When the aircraft climbs, the static pressure (P S ) will decrease. A pressure transducer  240  is used to measure the difference in total pressure (P T ) and static pressure (P S ). The pitot-static tube  220  may be employed by the disclosed system to obtain total pressure (P T ) and static pressure (P S ). 
       FIG. 3  is a block diagram  300  showing the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. In this figure, data (i.e. sensor measurements) sensed by the different types of sensors located on the vehicle are shown. In particular, total pressure (P T ) data  310   a  sensed by the pitot tubes  120 , static pressure (P S ) data  310   b  sensed by the static port  130 , angle of attack (AOA) (α) data  310   c  sensed by the AOA resolvers  140 , and acceleration (A N ) data  310   d  sensed by the accelerometer  150  are shown. 
     It should be noted that some of the sensed data comprises data sensed from multiple sensors. For example, the total pressure (P T ) data  310   a  comprises data sensed by three separate pitot tubes  120  located on the vehicle (e.g., airplane)  110 . In  FIG. 3 , three arrows are shown to be outputted from the total pressure (P T ) data  310   a  arrow to represent these three pieces of sensed data. 
     During operation, the sensed data for the total pressure (P T ) data  310   a , static pressure (P S ) data  310   b , and angle of attack (AOA) (α) data  310   c  are inputted into a static source error correction (SSEC) module  320 . It should be noted that the SSEC module  320  may be implemented within and/or executed by at least one processor  170  on the vehicle  110 . The SSEC module  320  performs source correction on the sensed data  310   a ,  310   b ,  310   c  by removing known corruption effects from the sensed data  310   a ,  310   b ,  310   c  to generate clean data measurements  325   a ,  325   b ,  325   c . The SSEC module  320  removes the known corruption effects from the sensed data  310   a ,  310   b ,  310   c  by utilizing other data measurements including, but not limited to, dynamic pressure, Mach number, angle of attack (ADA), flap position, gear position, excess thrust, and/or ground effect terms. 
     Once the known corruption effects from the sensed data  310   a ,  310   b ,  310   c  have been removed, the clean data measurements  325   a ,  325   b ,  325   c  are inputted into source selection fault detection (SSFD) modules  330   a ,  330   b ,  330   c . The SSFD modules  330   a ,  330   b ,  330   c  may be implemented within and/or executed by at least one processor  170  on the vehicle  110 . Each SSFD module  330   a ,  330   b ,  330   c  performs majority voting on the inputted clean data measurements  325   a ,  325   b ,  325   c  to generate a single voted value  350   a ,  350   b ,  350   c . For example, SSFD module  330   a  performs majority voting on three clean data measurements  325   a  to generate a single voted value  350   a.    
     Also, during operation, the acceleration (A N ) data  310   d  is inputted into a fault management module  340 . The fault management module  340  may be implemented within and/or executed by at least one processor  170  on the vehicle  110 . The fault management module  340  performs majority voting on the acceleration (A N ) data  310   d  to generate a single voted value  350   d.    
     It should be noted that, in one or more embodiments, various different types of majority voting algorithms (e.g., the Boyer-Moore majority voting algorithm) may be utilized by the SSFD modules  330   a ,  330   b ,  330   c  and the fault management module  340  to perform the majority voting. 
     After all of the single voted values  350   a ,  350   b ,  350   c ,  350   d  have been generated, the single voted values  350   a ,  350   b ,  350   c ,  350   d  are inputted into a synthetic air data and common mode monitor (CMM)  360 . The synthetic air data and CMM  360  may be implemented within and/or executed by at least one processor  170  on the vehicle  110 . The synthetic air data and CMM  360  utilizes the single voted values  350   a ,  350   b ,  350   c ,  350   d  to generate trusted values  370   a ,  370   b ,  370   c ,  370   d  to be used (e.g., to be used by the flight control system) for operation of the vehicle  110 . In particular, the synthetic air data and CMM  360  utilizes the single voted values  350   a ,  350   b ,  350   c ,  350   d  to generate a total pressure (P T ) trusted value  370   a , a total pressure (P S ) trusted value  370   b , an AOA trusted value  370   c , and an acceleration trusted value  370   d . Details of the operation of the synthetic air data and CMM  360  will be described in the description of  FIGS. 4, 5, 8, 9, and 10 . 
     Referring back to  FIG. 3 , after the trusted values  370   a ,  370   b ,  370   c ,  370   d  have been generated by the synthetic air data and CMM  360 , the trusted values  370   a ,  370   b ,  370   c ,  370   d  are inputted into an air data computations module  380 . The air data computations module  380  may be implemented within and/or executed by at least one processor  170  (which may be part of the flight control system) on the vehicle  110 . The air data computations module  380  may utilize the trusted values  370   a ,  370   b ,  370   c ,  370   d  for making calculations needed for the operation (e.g., flight) of the vehicle (e.g., airplane)  110 . 
       FIG. 4  is a block diagram  400  showing details of the functionality of the synthetic air data and common mode monitor (CMM)  360  of  FIG. 3 , in accordance with at least one embodiment of the present disclosure. In this figure, the single voted values  350   a ,  350   b ,  350   c ,  350   d  are inputted into the synthetic air data and CMM  360 . In particular, the voted value for total pressure (P T )  350   a , the voted value for static pressure (P S )  350   b , the voted value for AOA  350   c , and the voted value for acceleration  350   d  are inputted into the synthetic air data and CMM  360 . 
     After the synthetic air data and CMM  360  has received the single voted values  350   a ,  350   b ,  350   c ,  350   d , an estimator  410   a ,  410   b ,  410   c ,  410   d  for each of the types of data generates estimated values (e.g., synthetic values)  420   a ,  420   b ,  420   c ,  420   d  using some of the single voted values  350   a ,  350   b ,  350   c ,  350   d . In particular, each estimator  410   a ,  410   b ,  410   c ,  410   d , for a type of data uses the single voted values  350   a ,  350   b ,  350   c ,  350   d  for the other types of data to generate estimated values  420   a ,  420   b ,  420   c ,  420   d  for all of the types of data. 
     The estimators  410   a ,  410   b ,  410   c ,  410   d  use statistical filters to generate the estimated values  420   a ,  420   b ,  420   c ,  420   d . Various different types of statistical filters may be used by the estimators  410   a ,  410   b ,  410   c ,  410   d  to generate the estimated values  420   a ,  420   b ,  420   c ,  420   d  including, but not limited to, Kalman filters, extended Kalman filters (EKFs), unscented Kalman filters, frequency-weighted Kalman filters, fixed-lag smoothers, fixed-interval smoothers (e.g., Rauch-Tung-Striebel smoothers, modified Bryson-Frazier smoothers, and minimum-variance smoothers), Kalman-Bucy filters, and hybrid Kalman filters. 
     For example, estimator  1   410   a  for the total pressure (PT) data type, utilizes the voted value for static pressure (P S )  350   b , the voted value for AOA  350   c , and the voted value for acceleration  350   d  to generate the estimated values  420   a  (which include an estimated value for total pressure (PT), an estimated value for static pressure (P S ), an estimated value for AOA, and an estimated value for acceleration). Also, estimator  2   410   b  for the static pressure (P S ) data type, utilizes the voted value for total pressure (P T )  350   a , the voted value for AOA  350   c , and the voted value for acceleration  350   d  to generate the estimated values  420   b  (which include an estimated value for total pressure (PT), an estimated value for static pressure (P S ), an estimated value for AOA, and an estimated value for acceleration). In addition, estimator  3   410   c  for the AOA data type, utilizes the voted value for total pressure (P T )  350   a , the voted value for static pressure (P S )  350   b , and the voted value for acceleration  350   d  to generate the estimated values  420   c  (which include an estimated value for total pressure (P T ), an estimated value for static pressure (P S ), an estimated value for AOA, and an estimated value for acceleration). And, estimator  4   410   d  for the acceleration data type, utilizes the voted value for total pressure (P T )  350   a , the voted value for static pressure (P S )  350   b , and the voted value for AOA  350   c  to generate the estimated values  420   d  (which include an estimated value for total pressure (PT), an estimated value for static pressure (P S ), an estimated value for AOA, and an estimated value for acceleration). 
     After the estimators  410   a ,  410   b ,  410   c ,  410   d  have each generated estimated values  420   a ,  420   b ,  420   c ,  420   d , the estimated values  420   a ,  420   b ,  420   c ,  420   d  are inputted into a fault detection and isolation logic module  430 . The fault detection and isolation logic module  430  generates residuals (r 1 , r 2 , r 3 , r 4 ) by comparing the estimated values  420   a ,  420   b ,  420   c ,  420   d  to the voted values  350   a ,  350   b ,  350   c ,  350   d . Details of how the residuals are generated are described in the description of  FIG. 9 . After the residuals (r 1 , r 2 , r 3 , r 4 ) are generated, the fault detection and isolation logic module  430  analyzes a pattern of the residuals (r 1 , r 2 , r 3 , r 4 ) to determine which (if any) type of the data is erroneous. An exemplary fault detection logic (i.e. logic for detecting an erroneous type of data) is shown in  FIG. 8 , and an exemplary expected pattern of residuals is shown in  FIG. 10 . 
     After the fault detection and isolation logic module  430  has analyzed the pattern of residuals (r 1 , r 2 , r 3 , r 4 ), if the fault detection and isolation logic module  430  determines that there is no erroneous data, the fault detection and isolation logic module  430  will simply output the voted values  350   a ,  350   b ,  350   c ,  350   d  to be used for the trusted values  370   a ,  370   b ,  370   c ,  370   d  (e.g., total pressure (P T ) trusted value  370   a , total pressure (P S ) trusted value  370   b , AOA trusted value  370   c , and acceleration trusted value  370   d ). 
     However, if the fault detection and isolation logic module  430  determines that a type of data (e.g., total pressure (P T )) is erroneous, the fault detection and isolation logic module  430  will output the voted values  350   b ,  350   c ,  350   d  for the other types of data to be used for the trusted values  370   b ,  370   c ,  370   d  (e.g., total pressure (P S ) trusted value  370   b , AOA trusted value  370   c , and acceleration trusted value  370   d ) for those other types of data. And, the fault detection and isolation logic module  430  will output the estimated value (synthetic data)  420   a  generated by the data type&#39;s associated estimator (e.g., estimator  1 )  420   a  for that erroneous data type (e.g., total pressure (P T )) to be used for the trusted value  370   a  (e.g., total pressure (P T ) trusted value) for that erroneous data type. 
       FIG. 5  shows equations for generating the estimated values utilized by the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. For these equations, x is a vector representing the underlying state for the data types, and y is a vector representing the voted values  350   a ,  350   b ,  350   c ,  350   d  for the data types. Also, each ŷ is a vector representing the estimated values  420   a ,  420   b ,  420   c ,  420   d  generated by each of the estimators  410   a ,  410   b ,  410   c ,  410   d . In particular, for these equations, ŷ 1  is the estimated values generated by estimator  1   410   a , ŷ 2  is the estimated values generated by estimator  2   410   b , ŷ 3  is the estimated values generated by estimator  3   410   c , and ŷ 4  is the estimated values generated by estimator  4   410   d . Also, for these equations, f (e.g., f 1 , f 2 , f 3 , and f 4 ) represents the statistical filter (e.g., extended Kalman filter (EKF)) used to generate the estimated values  420   a ,  420   b ,  420   c ,  420   d . And, the variables (e.g., P T , P S , α, A N ) within the parenthesis represent the voted values  350   a ,  350   b ,  350   c ,  350   d  used to generate the estimated values  420   a ,  420   b ,  420   c ,  420   d.    
     For example, for estimator  1   410   a  (which is associated with the total pressure (P T ) data type), the voted value for static pressure (P S )  350   b , the voted value for AOA (α)  350   c , and the voted value for acceleration  350   d  are used by the statistical filter (f 1 ) (e.g., EKF) to generate the estimated values  420   a . As such, when there are m number of different data types sensed, each estimator  410   a ,  410   b ,  410   c ,  410   d  will use n number (which is equal to m minus 1 (n=m−1)) of voted values  350   a ,  350   b ,  350   c ,  350   d  to generate the estimated values  420   a ,  420   b ,  420   c ,  420   d.    
       FIG. 6A  shows exemplary graphs  600  illustrating the sensed data (i.e. measured data)  310   a ,  310   b ,  310   c ,  310   d  and the corresponding real values (i.e. truth values) for four different types of sensor data, where none of the sensed data  310   a ,  310   b ,  310   c ,  310   d  is erroneous, in accordance with at least one embodiment of the present disclosure. Each graph of this figure shows a different type of sensed data (e.g., total pressure (P T ), static pressure (P S ), AOA, and acceleration). As is shown in this figure, the sensed data (i.e. measured values)  310   a ,  310   b ,  310   c ,  310   d  closely follow the real values (i.e. truth values) for that data and, as such, no type of data is erroneous. 
       FIG. 6B  shows exemplary graphs  610  illustrating the estimated values (i.e. synthetic values)  420   a ,  420   b ,  420   c ,  420   d  generated by the disclosed system for sensor fault detection and identification for a vehicle  110 , where none of the sensed data  310   a ,  310   b ,  310   c ,  310   d  is erroneous, in accordance with at least one embodiment of the present disclosure. In this figure, each row of graphs illustrates the estimated values  420   a ,  420   b ,  420   c ,  420   d  generated by one of the estimators  410   a ,  410   b ,  410   c ,  410   d . For example, the first row of graphs shows the estimated values  420   a  generated by estimator  1   410   a , the second row of graphs shows the estimated values  420   b  generated by estimator  2   410   b , the third row of graphs shows the estimated values  420   c  generated by estimator  3   410   c , and the fourth row of graphs shows the estimated values  420   d  generated by estimator  4   410   d.    
     In  FIG. 6B , each of the sixteen graphs shows four lines of data, one of the middle lines of data of each graph is the generated estimated value  420   a ,  420   b ,  420   c ,  420   d  for the data type of the graph. The other middle lines of data of each graph are the sensed data (i.e. measured values)  310   a ,  310   b ,  310   c ,  310   d . The upper and lower lines of data of each graph denote an upper and lower threshold (T) for the estimated data (e.g., estimated values)  420   a ,  420   b ,  420   c ,  420   d  to lie within. 
       FIG. 7A  shows exemplary graphs illustrating the sensed data (i.e. measured data)  310   a ,  310   b ,  310   c ,  310   d  and the corresponding real values (i.e. truth values) for four different types of sensor data, where one of the types of sensed data (i.e. total pressure (P T ))  310   a  is erroneous, in accordance with at least one embodiment of the present disclosure. Each graph of this figure shows a different type of sensed data (e.g., total pressure (P T ), static pressure (P S ), AOA, and acceleration). As is shown in this figure, the sensed data (i.e. measured values) for static pressure (P S ), AOA, and acceleration  310   b ,  310   c ,  310   d , closely follow the real values (i.e. truth values) for that data. However, the sensed data (i.e. measured values) for total pressure (P T )  310   a  does not closely follow the real values (i.e. truth values) for that data type and, thus, the sensed data for total pressure (P T )  310   a  is erroneous. As such, it can be inferred that the pitot tubes  120 , which sense the total pressure (P T ), are experiencing a failure (e.g., a CMPE). 
       FIG. 7B  shows exemplary graphs illustrating the estimated values (i.e. synthetic values)  420   a ,  420   b ,  420   c ,  420   d  generated by the disclosed system for sensor fault detection and identification for a vehicle  110 , where one of the types of sensed data (i.e. total pressure (P T ))  310   a  is erroneous, in accordance with at least one embodiment of the present disclosure. In this figure, each row of graphs illustrates the estimated values  420   a ,  420   b ,  420   c ,  420   d  generated by one of the estimators  410   a ,  410   b ,  410   c ,  410   d . For example, the first row of graphs shows the estimated values  420   a  generated by estimator  1   410   a , the second row of graphs shows the estimated values  420   b  generated by estimator  2   410   b , the third row of graphs shows the estimated values  420   c  generated by estimator  3   410   c , and the fourth row of graphs shows the estimated values  420   d  generated by estimator  4   410   d.    
     In  FIG. 7B , each of the sixteen graphs shows four lines of data, one of the middle lines of data of each graph is the generated estimated value  420   a ,  420   b ,  420   c ,  420   d  for the data type of the graph. The other middle lines of data of each graph are the sensed data (i.e. measured values)  310   a ,  310   b ,  310   c ,  310   d . The upper and lower lines of data of each graph denote an upper and lower threshold (T) for the estimated value (e.g., estimated data)  420   a ,  420   b ,  420   c ,  420   d  to lie within. 
     In this figure, the graphs for the total pressure (P T ) data type (refer to the first column of graphs) exhibit that the sensed total pressure (P T )  310   a  lies outside of the lower threshold (T). It should be noted that since the sensed data for total pressure (P T )  310   a  is erroneous, the estimated value  420   a  generated by estimator  1   420   a  will be used as the trusted value for total pressure (P T )  470   a.    
       FIG. 8  shows equations for the fault detection logic utilized by the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. In this figure, the fault detection logic states that a sensed data type is erroneous (i.e. and the associated type of sensor has failed) if and only if (IFF): (1) the residuals produced from the estimator associated with that data type are small, and (2) the residuals produced from the estimators associated with the other data types are large. For example, the sensed data for total pressure (P T )  310   a  is erroneous (i.e. and the pitot tubes  120  have failed), if and only if: (1) the residuals (r 1 ) produced from estimator  1   410   a  are small (i.e. |r 1,Ps |&lt;T and |r 1,α |&lt;T and |r 2,AN |&lt;T), and the residuals produced from estimator  2   410   b , estimator  3   410   c , and estimator  4   410   d  are large (i.e. |r 2,PT |≥T and |r 3,PT |≥T and |r 4,PT |≥T). It should be noted that T represents a predetermined threshold. Also, it should be noted that, in one or more embodiments, the different threshold T values may be used for the different residuals. 
     Also, it should be noted that the residuals produced from estimator  1   410   a  are small because estimator  1   410   a  does not utilize the erroneous sensed data for total pressure (PT)  310   a  to generate its estimated values  420   a , which is used to calculate the residuals (r 1 ). And, the residuals produced from estimator  2   410   b , estimator  3   410   c , and estimator  4   410   d  are large because these estimators  410   b ,  410   c ,  410   d  utilize the erroneous sensed data for total pressure (P T )  310   a  to generate their estimated values  420   b ,  420   c ,  420   d , which are used to calculate the residuals (r 2 , r 3 , r 4 ). 
       FIG. 9  is a diagram  900  showing how the residuals are generated by the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. It should be noted that the example shown in this figure is using a total of three types of data (e.g., total pressure (P T ), static pressure (PS), and AOA). In this figure, each estimator (e.g., observer (OBS)  1 , OBS  2 , and OBS  3 )  910   a ,  910   b ,  910   c , is using voted values from two of the data types to generate estimated values for all three of the data types. 
     For example, the first estimator (OBS  1 )  910   a , which is associated with the total pressure (P T ) data type, utilizes static pressure (P S ) voted value (y 2 ) and AOA voted value (y 3 ) to generate (by using a statistical filter f 1 ) its estimated value ŷ 1 . Also, the second estimator (OBS  2 )  910   b , which is associated with the static pressure (P S ) data type, utilizes total pressure (P T ) voted value (y 1 ) and AOA voted value (y 3 ) to generate (by using a statistical filter f 2 ) its estimated value ŷ 2 . And, the third estimator (OBS  3 )  910   c , which is associated with the AOA data type, utilizes total pressure (P T ) voted value (y 1 ) and static pressure (P S ) voted value (y 2 ) to generate (by using a statistical filter f 3 ) its estimated value ŷ 3 . 
     After the estimated values ŷ 1 , ŷ 2 , ŷ 3  are generated by the estimators  910   a ,  910   b ,  910   c , the voted values y 1 , y 2 , y 3  are subtracted from their respective estimated values ŷ 1 , ŷ 2 , ŷ 3  to generate the residuals r 1 , r 2 , r 3 . As such, r 1  is equal to ŷ 1 -y 1 ; r 2  is equal to ŷ 2 -y 2 ; and r 3  is equal to ŷ 3 -y 3 . 
       FIG. 10  is a chart  1000  showing an exemplary expected pattern of residuals utilized by the disclosed system for sensor fault detection and identification for a vehicle  110 , in accordance with at least one embodiment of the present disclosure. Similar to  FIG. 9 , the example shown in this figure is using a total of three types of data (e.g., total pressure (P T ), static pressure (PS), and AOA). In this figure, the first three rows  1010  of the chart  1000  correspond to the first residual r 1 , the second three rows  1020  of the chart  1000  correspond to the second residual r 2 , and the last three rows  1030  of the chart  1000  correspond to the third residual r 3 . 
     The second column of the chart  1000  (f 1 =f 2 =f 3 =0) shows the expected pattern of residuals for when no type of data is erroneous. Since none of the data is erroneous, all of the residuals should be close to zero, as is shown in the second column. 
     The third column of the chart  1000  (f 1 ≠0, f 2 =0, f 3 =0) shows the expected pattern of residuals when the sensed data for the first data type (e.g., total pressure (P T )) is erroneous. The residuals r 2 , r 3  (refer to the rows of  1020  and  1030 ) for the second and third data types will not be close to zero because their associated estimated values ŷ 2 , ŷ 3  were generated using the voted value y 1  for the first data type (e.g., total pressure (P T )). 
     The fourth column of the chart  1000  (f 1 =0, f 2 ≠0, f 3 =0) shows the expected pattern of residuals when the sensed data for the second data type (e.g., static pressure (P S )) is erroneous. The residuals r 1 , r 3  (refer to the rows of  1010  and  1030 ) for the first and third data types will not be close to zero because their associated estimated values ŷ 1 , ŷ 3  were generated using the voted value y 2  for the second data type (e.g., static pressure (P S )). 
     The fifth column of the chart  1000  (f 1 =0, f 2 =0, f 3 ≠0) shows the expected pattern of residuals when the sensed data for the third data type (e.g., AOA) is erroneous. The residuals r 1 , r 2  (refer to the rows of  1010  and  1020 ) for the first and second data types will not be close to zero because their associated estimated values ŷ 1 , ŷ 2  were generated using the voted value y 3  for the third data type (e.g., AOA). 
       FIGS. 11A and 11B  together form a flow chart showing the disclosed method for sensor fault detection and identification for a vehicle, in accordance with at least one embodiment of the present disclosure. At the start  1110  of the method, sensors located on the vehicle sense data (e.g., measurement data)  1120 . In one or more embodiments, the data comprises m number types of data, and m is an integer greater than two. Then, at least one processor removes known corruption effects from at least some of the data  1130 . At least one processor then performed majority voting on the data for each of the types of data to generate a single voted value for each of the types of data  1140 . 
     Then, at least one processor generates, for each of the types of data, m number of estimated values by using n number of the voted values  1150 . In one or more embodiments, n is equal to m minus 1 (i.e. n=m−1). At least one processor then generates residuals by comparing the estimated values to the voted values  1160 . Then, at least one processor analyzes a pattern of the residuals to determine which of the types of the data is erroneous to detect and identify a fault experienced by at least one of the sensors on the vehicle  1170 . 
     Then, at least one processor generates an alert signal indicating which of the types of the data is erroneous and/or which type of the sensor are experiencing a failure  1180 . A visual alert (e.g., using an indicator light and/or a display) and/or an audible alert (e.g., using a speaker) is then generated based on information contained in the alert signal  1190 . Then, a synthetic data signal is generated that indicates to use synthetic data instead of erroneous sensed data  1195 . Then, the method ends  1197 . 
     Although particular embodiments have been shown and described, it should be understood that the above discussion is not intended to limit the scope of these embodiments. While embodiments and variations of the many aspects of the invention have been disclosed and described herein, such disclosure is provided for purposes of explanation and illustration only. Thus, various changes and modifications may be made without departing from the scope of the claims. 
     Where methods described above indicate certain events occurring in certain order, those of ordinary skill in the art having the benefit of this disclosure would recognize that the ordering may, be modified and that such modifications are in accordance with the variations of the present disclosure. Additionally, parts of methods may be performed concurrently in a parallel process when possible, as well as performed sequentially. In addition, more steps or less steps of the methods may be performed. 
     Accordingly, embodiments are intended to exemplify alternatives, modifications, and equivalents that may fall within the scope of the claims. 
     Although certain illustrative embodiments and methods have been disclosed herein, it can be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods can be made without departing from the true spirit and scope of this disclosure. Many other examples exist, each differing from others in matters of detail only. Accordingly, it is intended that this disclosure be limited only to the extent required by the appended claims and the rules and principles of applicable law.