Patent Publication Number: US-2022236410-A1

Title: Lidar laser health diagnostic

Description:
INTRODUCTION 
     The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     The present disclosure relates to vehicles and more particularly to systems and methods for performing diagnostics on autonomous driving sensors. 
     Vehicles include one or more torque producing devices, such as an internal combustion engine and/or an electric motor. A passenger of a vehicle rides within a passenger cabin (or passenger compartment) of the vehicle. 
     Autonomous driving systems drive a vehicle completely independent of a human driver. For example, autonomous driving systems control the acceleration, brake, and steering systems of a vehicle independent of a driver. 
     Semiautonomous driving systems drive a vehicle partially independent of a human driver. For example, a semiautonomous driving system may control the steering system independent of a driver while relying on the driver to set a target speed for the semiautonomous driving system to achieve by controlling the acceleration and brake systems. 
     SUMMARY 
     A sensor diagnostic system includes a first sensor configured to receive a reflected signal that corresponds to a portion of a transmitted signal transmitted from a second sensor and reflected from a surface, a wavelength determination module configured to determine a first wavelength of the reflected signal that is indicative of a second wavelength of the transmitted signal, a wavelength shift detection module configured to determine a shift in at least one of the first wavelength and the second wavelength, and a sensor health analysis module configured to perform diagnostics on the second sensor based on the determined shift. 
     In other features, the second sensor is a light detection and ranging (LIDAR) sensor. 
     In other features, the sensor health analysis module is configured to determine a change in at least one operating characteristic of the LIDAR sensor based on the determined shift and perform the diagnostics on the LIDAR sensor based on the determined change in the at least one operating characteristic. 
     In other features, the at least one operating characteristic includes at least one of a die temperature, mode hopping, optical cavity stability, photon energy, pulse width, power and beam intensity, a shift in magnitude, a shift in phase, a shift in polarization. 
     In other features, the sensor health analysis module is configured to determine the change in the at least one operating characteristic of the LIDAR sensor based on a lookup table correlating the determined shift with the change in the at least one operating characteristic. 
     In other features, the sensor health analysis module is configured to perform the diagnostics of the LIDAR sensor based on a comparison between the change in the at least one operating characteristic and a threshold. 
     In other features, an autonomous module is configured to selectively control functions of a vehicle and, based on the diagnostics, one of discontinue controlling functions of the vehicle, disable the LIDAR sensor, and activate an indicator. 
     In other features, the wavelength shift detection module is configured to determine the shift based on a comparison between the at least one of the first wavelength and the second wavelength and a reference wavelength. 
     In other features, at least one of a spectrometer and a spectroradiometer is configured to determine the first wavelength of the reflected signal. 
     In other features, the sensor diagnostic system includes a liquid crystal metasurface. 
     In other features, the first sensor and the second sensor are arranged in a passenger cabin of a vehicle. 
     In other features, the first sensor and the second sensor are arranged within a same housing. 
     In other features, the first sensor and the second sensor are arranged in a passenger cabin of the vehicle. 
     A sensor diagnostic system for a vehicle includes a light detection and ranging (LIDAR) sensor that includes a transmitting portion and a receiving portion. The transmitting portion is configured to transmit a signal and the receiving portion is configured to receive, as a received signal, a first portion of the transmitted signal that is reflected from an object in an environment external to the vehicle. A reflected signal sensor is positioned to receive a reflected signal corresponding to a second portion of the transmitted signal that is reflected from a surface of vehicle. A sensor diagnostic module is configured to determine a first wavelength of the reflected signal, wherein the first wavelength is indicative of a second wavelength of the transmitted signal, determine a shift in at least one of the first wavelength and the second wavelength, and perform diagnostics on the LIDAR sensor based on the determined shift. 
     In other features, the sensor diagnostic module is configured to determine a change in at least one operating characteristic of the LIDAR sensor based on the determined shift and perform the diagnostics on the LIDAR sensor based on the determined change in the at least one operating characteristic. 
     In other features, the at least one operating characteristic includes at least one of a die temperature, mode hopping, optical cavity stability, photon energy, pulse width, power and beam intensity, a shift in magnitude, a shift in phase, a shift in polarization. 
     In other features, the sensor diagnostic module is configured to perform the diagnostics of the LIDAR sensor based on a comparison between the change in the at least one operating characteristic and a threshold. 
     In other features, an autonomous module is configured to selectively control functions of a vehicle and, based on the diagnostics, one of discontinue controlling functions of the vehicle, disable the LIDAR sensor, and activate an indicator. 
     In other features, the sensor diagnostic module is configured to determine the shift based on a comparison between the at least one of the first wavelength and the second wavelength and a reference wavelength. 
     A method of diagnosing a light detection and ranging (LIDAR) sensor of a vehicle includes transmitting a signal, from the LIDAR sensor, from a passenger cabin of the vehicle, receiving, as a received signal, a first portion of the transmitted signal that passes through a windshield of the vehicle and is reflected from an object in an environment external to the passenger cabin, receiving, using a reflected signal sensor arranged within the passenger cabin of the vehicle, a reflected signal corresponding to a second portion of the transmitted signal that is reflected from an interior surface within the passenger cabin without passing through the windshield, determining a first wavelength of the reflected signal that is indicative of a second wavelength of the transmitted signal, determining a shift in at least one of the first wavelength and the second wavelength, and performing diagnostics on the LIDAR sensor based on the determined shift. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an example vehicle system; 
         FIG. 2  is a functional block diagram of a vehicle including examples of external sensors and cameras; 
         FIG. 3  is a functional block diagram of an example sensor diagnostic system including a sensor diagnostic module; and 
         FIG. 4  illustrate steps of an example method of performing diagnostics on a sensor. 
     
    
    
     In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
     DETAILED DESCRIPTION 
     A vehicle may include one or more cameras and/or one or more sensors (i.e., combination transmitter/sensors) used for autonomous driving. For example, the sensors may include one or more light detection and ranging (LIDAR) sensors. Systems and methods according to the present disclosure are configured to perform diagnostics (e.g., an assessment of health/functionality) on the sensors. In one example, a sensor diagnostic module detects a wavelength shift of a laser transmitted and received by the sensor and diagnoses the sensor based on the wavelength shift. Various mechanisms may be implemented to measure or estimate the wavelength shift including, but not limited to, a spectrometer, a spectroradiometer, a metasurface (e.g. a liquid crystal (LC) metasurface) arranged to receive/reflect the laser, a prism, mirror, and/or Bragg grating element, etc. Although described with respect to vehicle implementations, the principles of the present disclosure may also be applied to non-vehicle implementations or implemented within any LASER module. 
     Referring now to  FIG. 1 , a functional block diagram of an example vehicle system  100  is presented. While a vehicle system for a hybrid vehicle is shown and will be described, the present disclosure is also applicable to non-hybrid vehicles, electric vehicles, fuel cell vehicles, and other types of vehicles. 
     An engine  102  may combust an air/fuel mixture to generate drive torque. An engine control module (ECM)  106  controls the engine  102 . For example, the ECM  106  may control actuation of engine actuators, such as a throttle valve, one or more spark plugs, one or more fuel injectors, valve actuators, camshaft phasers, an exhaust gas recirculation (EGR) valve, one or more boost devices, and other suitable engine actuators. 
     The engine  102  may output torque to a transmission  110 . A transmission control module (TCM)  114  controls operation of the transmission  110 . For example, the TCM  114  may control gear selection within the transmission  110  and one or more torque transfer devices (e.g., a torque converter, one or more clutches, etc.). 
     The vehicle system may include one or more electric motors. For example, an electric motor  118  may be implemented within the transmission  110  as shown in the example of  FIG. 1 . An electric motor can act as either a generator or as a motor at a given time. When acting as a generator, an electric motor converts mechanical energy into electrical energy. The electrical energy can be, for example, used to charge a battery  126  via a power control device (PCD)  130 . When acting as a motor, an electric motor generates torque that may be used, for example, to supplement or replace torque output by the engine  102 . While the example of one electric motor is provided, the vehicle may include zero or more than one electric motor. 
     A power inverter module (PIM)  134  may control the electric motor  118  and the PCD  130 . The PCD  130  applies (e.g., direct current) power from the battery  126  to the (e.g., alternating current) electric motor  118  based on signals from the PIM  134 , and the PCD  130  provides power output by the electric motor  118 , for example, to the battery  126 . The PIM  134  may be referred to as an inverter module in various implementations. 
     A steering control module  140  controls steering/turning of wheels of the vehicle, for example, based on driver turning of a steering wheel within the vehicle and/or steering commands from one or more vehicle control modules. A steering wheel angle sensor (SWA) monitors rotational position of the steering wheel and generates a SWA  142  based on the position of the steering wheel. As an example, the steering control module  140  may control vehicle steering via an EPS motor  144  based on the SWA  142 . However, the vehicle may include another type of steering system. 
     An electronic brake control module (EBCM)  150  may selectively control brakes  154  of the vehicle. Modules of the vehicle may share parameters via a controller area network (CAN)  162 . The CAN  162  may also be referred to as a car area network. For example, the CAN  162  may include one or more data buses. Various parameters may be made available by a given control module to other control modules via the CAN  162 . 
     The driver inputs may include, for example, an accelerator pedal position (APP)  166  which may be provided to the ECM  106 . A cruise control input  168  may also be input to the ECM  106  from a cruise control system. In various implementations, the cruise control system may include an adaptive cruise control system. A brake pedal position (BPP)  170  may be provided to the EBCM  150 . A position  174  of a park, reverse, neutral, drive lever (PRNDL) may be provided to the TCM  114 . An ignition state  176  may be provided to a body control module (BCM)  178 . For example, the ignition state  176  may be input by a driver via an ignition key, button, or switch. At a given time, the ignition state  176  may be one of off, accessory, run, or crank. 
     The vehicle system may include an infotainment module  180 . The infotainment module  180  controls what is displayed on a display  182 . The display  182  may be a touchscreen display in various implementations and transmit signals indicative of user input to the display  182  to the infotainment module  180 . The infotainment module  180  may additionally or alternatively receive signals indicative of user input from one or more other user input devices  184 , such as one or more switches, buttons, knobs, etc. 
     The infotainment module  180  may receive input from a plurality of external sensors and cameras, generally illustrated in  FIG. 1  by  186 . For example, the infotainment module  180  may display video, various views, and/or alerts on the display  182  via input from the external sensors and cameras  186 . The external sensors and cameras  186  may include sensors (e.g., LIDAR sensors) that capture images and video outside of (external to) the vehicle and various types of sensors measuring parameters outside of (external to) the vehicle. Input from the external sensors and cameras  186  may be used to control autonomous driving. 
     For example, an autonomous module  188  may be configured to control steering, acceleration and deceleration, and braking of the vehicle during autonomous driving of the vehicle. For example, the autonomous module  188  may detect features and objects around the vehicle based on input from the external cameras and sensors  186  and control steering, acceleration, and deceleration based on the features and objects, such as to avoid any objects detected. During autonomous driving, however, driver inputs (e.g., steering, braking, and/or acceleration inputs) may override input from the autonomous module  188 . The autonomous module  188  (and/or another module, such as the ECM  106 ) according to the present disclosure implements a sensor diagnostic module as described below in more detail. 
     The infotainment module  180  may also generate output via one or more other devices. For example, the infotainment module  180  may output sound via one or more speakers  190  of the vehicle. The vehicle may include one or more additional control modules that are not shown, such as a chassis control module, a battery pack control module, etc. The vehicle may omit one or more of the control modules shown and discussed. 
     A global positioning system (GPS) module  192  receives GPS data from a GPS system. A driver monitoring module  194  includes one or more devices configured to monitor one or more characteristics of a driver of the vehicle. For example, the driver monitoring module  194  may include one or more cameras configured to capture images of the driver and within a passenger cabin of the vehicle, for example, to determine a facial expression, one or more gestures, hand placement, and other driver information based on the images. 
     A V2X module  196  communicates with other vehicles via a vehicle to vehicle (V2V) communication protocol and/or with infrastructure via a vehicle to infrastructure (V2I) communication protocol. V2V communication and V2I communication can be more generally referred to as V2X communication. 
     Referring now to  FIG. 2 , a functional block diagram of a vehicle  200  including examples of external sensors and cameras (e.g., the external sensors and cameras  186  as described in  FIG. 1 ) is presented. The external sensors and cameras  186  include various cameras positioned to capture images and video outside of (external to) the vehicle  200  and various types of sensors measuring parameters outside of (external to) the vehicle  200 . For example, a forward facing camera  204  captures images and video of images within a predetermined field of view (FOV)  206  in front of the vehicle  200 . 
     A front camera  208  may also capture images and video within a predetermined FOV  210  in front of the vehicle  200 . The front camera  208  may capture images and video within a predetermined distance of the front of the vehicle  200  and may be located at the front of the vehicle  200  (e.g., in a front fascia, grille, or bumper). The forward facing camera  204  may be located more rearward, such as with a rear view mirror within a windshield of the vehicle  200 . The forward facing camera  204  may not be able to capture images and video of items within all of or at least a portion of the predetermined FOV of the front camera  208  and may capture images and video that is greater than the predetermined distance of the front of the vehicle  200 . In various implementations, only one of the forward facing camera  204  and the front camera  208  may be included. 
     A rear camera  212  captures images and video within a predetermined FOV  214  behind the vehicle  200 . The rear camera  212  may capture images and video within a predetermined distance behind the vehicle  200  and may be located at the rear of the vehicle  200 , such as near a rear license plate. A right camera  216  captures images and video within a predetermined FOV  218  to the right of the vehicle  200 . The right camera  216  may capture images and video within a predetermined distance to the right of the vehicle  200  and may be located, for example, under a right side rear view mirror. In various implementations, the right side rear view mirror may be omitted, and the right camera  216  may be located near where the right side rear view mirror would normally be located. A left camera  220  captures images and video within a predetermined FOV  222  to the left of the vehicle  200 . The left camera  220  may capture images and video within a predetermined distance to the left of the vehicle  200  and may be located, for example, under a left side rear view mirror. In various implementations, the left side rear view mirror may be omitted, and the left camera  220  may be located near where the left side rear view mirror would normally be located. While the example FOVs are shown for illustrative purposes, the FOVs may overlap, for example, for more accurate and/or inclusive stitching. 
     The external sensors and cameras  186  also include various other types of sensors, such as radar sensors, one or more LIDAR sensors  250 , etc. For example, the vehicle  200  may include one or more forward facing radar sensors, such as forward facing radar sensors  226  and  230 , one or more rearward facing radar sensors, such as rearward facing radar sensors  234  and  238 . The vehicle  200  may also include one or more right side radar sensors, such as right side radar sensor  242 , and one or more left side radar sensors, such as left side radar sensor  246 . The locations and fields of view of the cameras and radar sensors are provided as examples only and different locations and fields of view could be used. Radar sensors output radar signals around the vehicle  200 . Objects around the vehicle  200  can be detected based on input from the external sensors and cameras  186 . 
     One or more sensors may be located rearward of the windshield (e.g., within the passenger cabin of the vehicle  200 , such as the forward facing camera  204  as described above). In some examples, a LIDAR sensor including a LIDAR transmitter and sensor is located within the passenger cabin. Accordingly, a signal transmitted from the LIDAR sensor passes through the windshield, reflects off of objects in the environment external to the vehicle, and passes back through the windshield to be received by the LIDAR sensor. A portion of the transmitted signal is reflected from an interior surface of the windshield back into the passenger cabin. The sensor diagnostic module according to the present disclosure is configured to perform diagnostics on the transmitter of the LIDAR sensor based on the reflected signal as described below in more detail. 
     Referring now to  FIG. 3 , an example sensor diagnostic system  300  according to the present disclosure includes a sensor diagnostic module  304 . The sensor diagnostic module  304  is configured to perform diagnostics on a sensor (e.g., a LIDAR sensor)  308 . The sensor  308  is configured to transmit a signal (e.g., a laser signal)  312  from within an interior of a vehicle (e.g., the vehicle  200 ) through a windshield  316  of the vehicle  200 . For example, the sensor  308  is arranged in a passenger cabin of the vehicle  200 , such as on a ceiling of the passenger cabin, on or adjacent to a rearview mirror, on a dashboard, etc. 
     The signal  312  passes through the windshield  316  and is reflected from an object  320  in an environment around the vehicle  200  and is received by the sensor  308  as a received signal  324 . An autonomous module  328  may detect features and objects in the environment around the vehicle  200  based on input from the sensor  308 . For example, the received signal  324  indicates a distance between the vehicle  200  and the object  320  and the autonomous module  328  controls functions of the vehicle  200  accordingly as described above in more detail. 
     A portion of the signal  312  is reflected off of an interior surface of the windshield  316  (as a reflected signal  332 ) back into the interior of the vehicle  200 . One or more reflected signal sensors or receivers  336  are positioned to receive the reflected signal  332 . For example, the reflected signal sensor  336  is arranged in the passenger cabin of the vehicle  200  in a location corresponding to a known or predetermined trajectory of the reflected signal  332 , such as on a ceiling of the passenger cabin, on or adjacent to the rearview mirror, on the dashboard, etc. In some examples, the reflected signal sensor  336  is located adjacent to or integrated within the sensor  308  (e.g., integrated within a same housing as the sensor  308 ). The trajectory of the reflected signal  332  may be dependent upon the rake or angle of the windshield  316 , a material composition of the windshield  315 , etc. Accordingly, the trajectory of the reflected signal  332  and the location of the reflected signal sensor  336  may vary by vehicle. In some examples, the windshield  316  may include an embedded or attached reflecting module (not shown) positioned to receive and reflect the signal  312  at a predetermined trajectory (i.e., toward a desired position of the reflected signal sensor  336 ). 
     In some examples, a liquid crystal metasurface may be arranged to receive the signal  312  or the reflected signal  332 . For example, the liquid crystal metasurface may be arranged adjacent to or embedded within the windshield  316  and may be configured to receive the signal  312  and steer one or more of the reflected signals  332  in a desired direction. In other examples, the reflected signal sensor  336  may include a liquid crystal metasurface configured to receive the reflected signal  332 . In still other examples, the liquid crystal metasurface may be arranged elsewhere within the passenger cabin, within the sensor  308 , etc. 
     The sensor diagnostic module  304  is configured to perform diagnostics on the sensor  308  (e.g., a transmitter portion of the sensor  308 ) based on the reflected signal  332 . For example, the sensor diagnostic module  304  receives an output  340  of the reflected signal sensor  336  indicative of characteristics of the reflected signal  332 . The sensor diagnostic module  304  is configured to determine a wavelength of the reflected signal  332 , which is indicative of a wavelength of the signal  312  transmitted from the sensor  308 . The sensor diagnostic module  304  determines (diagnoses) a condition of the sensor  308  based on the determined wavelength of the reflected signal  332 . 
     For example, the sensor diagnostic module  304  includes a wavelength determination module  344  configured to determine the wavelength of the reflected signal  332  and, correspondingly, the wavelength of the signal  312  based on the output  340  of the reflected signal sensor  336 . For example, the reflected signal sensor  336  and the wavelength determination module  344  may correspond to components of a chip-scale spectrometer configured to receive the reflected signal  332 , measure the wavelength of the reflected signal  332 , and output a wavelength signal  348  indicating the measured wavelength. In another example, the reflected signal sensor  336  and/or the wavelength determination module  344  may include components including, but not limited to, a prism, a Bragg deflector or grating element, a beam combiner, fiber optic cables and couplings, etc. configured to receive the reflected signal  332 , measure the wavelength of the reflected signal  332 , and output the wavelength signal  348 . 
     In one example, the wavelength signal  348  may correspond to the wavelength of the reflected signal  332 . In another example, the wavelength determination module  344  determines the wavelength of the signal  312  based on the measured wavelength of the reflected signal  332  and the wavelength signal  348  corresponds to the wavelength of the signal  312 . 
     A wavelength shift detection module  352  receives the wavelength signal  348  and calculates a wavelength shift based on changes in the wavelength signal  348 . For example, the wavelength shift detection module  352  is configured to compare the wavelength signal  348  with a reference wavelength. The reference wavelength may correspond to a wavelength of the transmitted signal  312  during normal operation. The reference wavelength may be determined during manufacture, measured during calibration of the sensor  308 , determined over time during an operation period of the sensor  308 , etc. The wavelength shift detection module  352  outputs a wavelength shift signal  356  indicative of the calculated wavelength shift. 
     A sensor health analysis module  360  receives the wavelength shift signal  356  and is configured to perform diagnostics on the sensor  308  based on the wavelength shift signal  356 . The wavelength of the signal  312  (and, correspondingly, the wavelength shift indicated by the wavelength shift signal  356 ) is indicative of various operating characteristics of the sensor  308 , which may be further indicative of the health of the sensor  308 . 
     For example, the wavelength of the signal  312  may indicate operating characteristics of the sensor  308  including, but not limited to, a die temperature of the sensor  308 , mode hopping, optical cavity stability, photon energy, pulse width, power and beam intensity, and shifts in magnitude, phase, and/or polarization. In other words, the wavelength shift indicates a corresponding change in respective operating characteristics of the sensor  308 . Respective relationships between the wavelength shift and the changes in the operating characteristics of the sensor  308  may vary by laser type and in accordance with other operating or environmental characteristics (e.g., temperature). For example, die temperature may have a generally linear or piecewise linear relationship with the wavelength of the signal  312 . For example only, the sensor health analysis module  360  may determine the changes in the operating characteristics of the sensor  308  using a lookup table that correlates wavelength shift to changes in the respective operating characteristics, respective formulas or algorithms that use wavelength shift as an input to calculate the operating characteristics, models, etc. 
     The sensor health analysis module  360  is configured to selectively command and/or perform one or more remedial actions based on the wavelength shift and corresponding changes to the operating characteristics. For example, the sensor health analysis module  360  outputs a diagnostic result signal  364  requesting one or more remedial actions. For example only, the diagnostic result signal  364  may indicate that the wavelength shift and/or changes in one or more of the operating characteristics of the sensor  308  exceeds a respective threshold. 
     In some examples, the sensor health analysis module  360  may be configured to predict degradation and/or a remaining lifetime of the sensor  308 . For example, as the wavelength shift varies or increases over time, the sensor health analysis module  360  may predict (e.g., based on a rate of change of the wavelength) when the wavelength shift will reach a threshold indicating that the sensor  308  is no longer reliable. 
     The autonomous module  328  may receive the diagnostic result signal  364  and selectively perform remedial actions based on the diagnostic result signal  364 . The remedial actions include, but are not limited to, activating an indicator to inform a driver of the health of the sensor  308  (e.g., activing a check engine or other diagnostic light, displaying information on a display screen, etc.), deactivating the sensor  308 , disregarding inputs received from the sensor  308 , disabling autonomous driving functions, etc. 
       FIG. 4  is an example method  400  of performing diagnostics on a sensor  308  according to the principles of the present disclosure. At  404 , the method  400  transmits a signal from a sensor (e.g., transmits a laser from a LIDAR sensor, such as the signal  312  transmitted from the sensor  308 ). At  408 , the method  400  (e.g., the reflected signal sensor  336 ) receives a portion of the signal reflected from a surface, such as an interior surface of the windshield  316 . At  412 , the method  400  (e.g., respective components of the reflected signal sensor  336  and/or the wavelength determination module  344 ) determines and outputs a wavelength of the reflected signal and/or the wavelength of the transmitted signal. 
     At  416 , the method  400  (e.g., the wavelength shift detection module  352 ) determines and outputs a wavelength shift of the reflected signal and/or the transmitted signal. At  420 , the method  400  (e.g., the sensor health analysis module  360 ) performs diagnostics on the sensor  308  based on the wavelength shift. For example, the sensor health analysis module  360  determines changes in operating characteristics of the sensor  308  based on the wavelength shift and performs the diagnostics based on the changes in the operating characteristics. 
     At  424 , the method  400  (e.g., the sensor health analysis module  260 , the autonomous module  328 , etc.) determines whether to perform one or more remedial actions based on the diagnostics. For example, the method  400  determines whether one or more of the wavelength shift and the operating characteristics exceeds a respective threshold indicative of degraded performance (e.g., inaccurate sensing results). If true, the method  400  continues to  428 . If false, the method  400  continues to  404 . 
     At  428 , the method  400  (e.g., the sensor health analysis module  260 , the autonomous module  328 , etc.) selectively performs one or more remedial actions based on the diagnostics. The method  400  then continues to  404 . Accordingly, the method  400  may continuously (or, in some examples, periodically, conditionally, etc.) monitor the reflected signal  332  to diagnose the health of the sensor  308 . 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A. 
     In this application, including the definitions below, the term “module” or the term “controller” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
     The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules. 
     The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc). 
     The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer. 
     The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc. 
     The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.