Camera systems are becoming more prevalent in automotive and other applications, such as vehicle cameras, security cameras, industrial automation systems, and in other applications and end-use systems. Operation of camera and lighting systems is facilitated by clean optical paths, which can be hindered by dirt, water or other debris, particularly in outdoor applications such as vehicle mounted camera systems, outdoor security camera systems, camera systems in industrial facilities, etc. In particular, camera or light source lenses may be subject to ambient weather conditions, dirt and debris, and other contaminants which can obstruct or interfere with optical transmission through the lens. Automatic lens cleaning systems (LCSs) have been developed for vehicle and security cameras to self-clean a lens or lens cover. Such systems may include air or water spray apparatus to wash a lens surface. Other lens cleaning systems electronically vibrate the lens to expel contaminants, water or other unwanted material from the lens cover to improve image quality or light transmission efficiency. In certain applications, the optical system and the lens cleaning apparatus may be subjected to mechanical stresses, thermal stresses and other adverse environmental conditions that can degrade the cleaning system components. For instance, a lens or lens cover may become cracked, a vibration transducer may fail, a seal structure may be compromised, an adhesive bond between the lens and a transducer may fail, or a number of other failures or degradation types may occur. In vehicle-based systems or other applications where a camera or light source cannot be conveniently accessed, it is desirable to maintain proper operation of the lens cleaning system to ensure continued optical transmission through a lens or lens cover.
Disclosed examples include lens cleaning systems, drivers and methods to detect faults or degradation in a lens cleaning system, including a controller to control a lens transducer drive signal frequency to vibrate the lens in a frequency range of interest and measure frequency response values according to driver feedback signals and to compare the measured frequency response values to baseline frequency response values for a healthy system. The controller determines the existence of a fault or degradation in the lens cleaning system according to dissimilarities between the measured frequency response values and the baseline frequency response values at multiple frequencies. The frequency response can be measured as an impedance response, admittance response or other frequency domain equivalent. In this disclosure, the impedance response will be used to convey the concepts related to this invention.
In accordance with certain aspects of the disclosure, a lens cleaning system and a lens cleaning system driver are provided. The driver includes an output that provides an oscillating drive signal to a transducer to vibrate a lens and a feedback circuit that receives transducer voltage and current feedback signals. The driver further includes a controller that controls the frequency of the drive signal to vibrate the lens at frequencies in a frequency range of interest and determines measured frequency response values according to the current and voltage feedback signals. The controller compares the measured frequency response values to baseline frequency response values for a healthy lens cleaning system in the frequency range of interest and selectively determines the existence of a lens cleaning system fault or degradation according to dissimilarities between the measured frequency response values and the baseline frequency response values. The driver in certain examples provides an indication of a fault or degradation type based on analysis of multiple ranges of interest. In certain implementations, the controller operates in a second mode to measure and store a baseline impedance profile including frequency response values measured for the healthy lens cleaning system across a wide range of frequencies that includes the frequency range of interest, and the controller identifies one or more frequency ranges of interest that include a pole or zero of the baseline impedance profile.
Methods are provided for detecting lens cleaning system faults or degradation, which include controlling a drive signal frequency to vibrate a lens at a plurality of frequencies in a frequency range of interest, as well as determining measured frequency response values individually corresponding to one of the frequencies in the frequency range of interest. The method further includes comparing the measured frequency response values to baseline frequency response values in the frequency range of interest for a healthy lens cleaning system and selectively determining lens cleaning system faults or degradation according to dissimilarities between the measured frequency response values and the baseline frequency response values.
In the drawings, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. In the following discussion and in the claims, the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are intended to be inclusive in a manner similar to the term “comprising”, and thus should be interpreted to mean “including, but not limited to . . . ” Also, the term “couple” or “couples” is intended to include indirect or direct electrical or mechanical connection or combinations thereof. For example, if a first device couples to or is coupled with a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via one or more intervening devices and connections.
Referring initially to
The lens 202 in one example is a “fisheye” lens having a curved outer surface as shown in
As best shown in
As shown in
The driver IC 100 further includes an amplifier 118 which amplifies the output signal VS to generate the oscillating drive signal VDRV. In this manner, the controller 130 provides the desired frequency Ft of the drive signal VDRV, and thereby controls the oscillatory frequency of the transducer 102 for cleaning the lens 202 and/or to implement calibration and fault/degradation detection functions as described herein. In one example, the amplifier 118 is a full H-bridge amplifier circuit with first and second outputs individually coupled with the transducer terminals 131a and 131b to provide the oscillating drive signal VDRV to the transducer 102. In the example of
In certain examples, the amplifier 118 can provide a single ended output through the first filter circuit 119a to the first output terminal 112, and the return current from the transducer 102 flows through the second filter circuit 119b to return to the second output of the amplifier 118. In the illustrated example, the amplifier 118 provides a differential output to the filters 119a, 119b. In this case, the individual filter circuits 119a and 119b each include a series inductor and a capacitor connected between the second inductor terminal and a common reference voltage (e.g., GND) to deliver the amplified signal to the transducer 102. In this manner, the amplifier 118 amplifies the signal generator output signal VS and delivers an oscillating drive signal VDRV to the transducer 102. The filter circuit 119 advantageously allows the use of a square wave output from the PWM signal generator 116 to provide a generally sinusoidal oscillating signal VDRV to vibrate the transducer 102 and the mechanically coupled lens 202.
The driver IC 100 also includes a feedback circuit with a current sensor or current transducer 120 that generates a current feedback signal IFB representing a current IDRV flowing in the transducer 102. The feedback circuitry also includes a differential amplifier 132 with inputs connected to the transducer output terminals 112 and 114, as well as an amplifier output that generates a voltage feedback signal VFB representing the transducer voltage. The feedback signals IFB and VFB are provided to the controller 130. In one example, the controller 130 includes analog-to-digital (A/D) converters 134 and 135 to convert the current and voltage feedback signals IFB and VFB to digital values. In one possible implementation, the controller 130, the amplifier 118 and the feedback circuitry are fabricated in a single integrated circuit 100. The driver 100 can be provided on a single printed circuit board (PCB) along with a camera 212 (or a light source) to provide a compact solution for various vehicle-based and/or security camera systems for lighting systems generally.
The driver IC 100 operates in a normal mode to selectively provide ultrasonic lens cleaning functions in conjunction with the associated transducer 102. The outer surface of the lens 202 in
The controller 130 also operates in a first mode (e.g., DETECT mode in
In the degradation/fault detection operation in the first mode, the controller 130 controls the frequency Ft of the drive signal VDRV to vibrate the lens 202 at a plurality of frequencies in a frequency range of interest. In one implementation, the controller 130 performs a frequency sweep for one or more predetermined frequency ranges of interest. The controller 130 digitally converts the feedback signals during the frequency sweep, obtains frequency spectrum phasor information 138 and 139, and divides these values 140 to obtain sweep frequency response values 142 corresponding to the frequencies in the range of interest. The controller 130 also implements a comparison function 144 that compares the measured frequency response values 142 to baseline frequency response values 152 associated with corresponding ones of the plurality of frequencies in a given frequency range of interest for a healthy lens cleaning system. The controller 130 uses the comparison to selectively determine the existence of a fault in the system or degradation in the lens cleaning system according to dissimilarities between the measured frequency response values 142 and the baseline frequency response values 152. The controller 130 does not need to perform a continuous sweep, and instead controls the lens transducer drive signal frequency Ft to vibrate the lens 202 at one or more frequencies included in a predetermined frequency range of interest and computes the corresponding frequency response values 142 according to the driver feedback signals VFB, IFB.
The controller 130 compares the measured frequency response values 142 to corresponding baseline frequency response values 152 for a healthy system. The controller 130 selectively determines the existence of a fault or degradation in the lens cleaning system according to dissimilarities between the measured frequency response values 142 and the baseline frequency response values 152. In certain implementations, the controller 130 compares the difference between the measured and baseline values 142, 152 with a threshold to make an initial determination of whether or not the system is healthy. If a fault or degradation is determined (e.g., the difference exceeds a first threshold), the amount of the difference can be used to distinguish between suspected faults and suspected degradation for example, using a second threshold comparison. The controller 130 in one example includes an output 146 that selectively provides a signal FAULT/DEGRADATION to a host system 148 in response to determination of the existence of a fault or degradation. This architecture facilitates appropriate remedial action by the host system. For example, in a vehicle-mounted driving assistance application, automated vehicle control systems that use a camera output for vehicle navigation, braking control, steering control, driver warnings, etc. can be automatically notified by the driver IC 100 that the lens cleaning system is degraded or faulty.
In one example, the controller 130 is further operable in a second mode (e.g., BASELINE mode in
In certain examples, the controller 130 determines one or more baseline profiles for each of a plurality of different transducer voltages, and stores these multiple baseline frequency response profiles in the memory of the lens cleaner system. In these examples, the controller 130 operates in the first (DETECT) mode for each of a plurality of different transducer voltages to drive the transducer 102 in order to vibrate the lens 202 at frequencies in a predetermined range of interest for the corresponding transducer voltage. In this case, the controller 130 determines measured frequency response values 142 that individually correspond to one of the plurality of frequencies in the predetermined frequency range of interest according to the current feedback signal IFB and the voltage feedback signal VFB. The controller 130 compares the measured frequency response values to the corresponding baseline frequency response values 152 in the predetermined frequency range of interest for the corresponding transducer voltage. The controller 130 selectively determines existence of a fault or degradation according to dissimilarities identified in the comparison. In this regard, the normal cleaning operation of the system can operate at certain transducer voltages tailored to removing contaminants from the lens 202, whereas the fault or degradation detection operations of the system may be performed at these voltages and/or at different (e.g., lower) voltages tailored to detecting the existence of one or more failures or faults in the system while potentially reducing power consumption. This architecture is particularly advantageous where the lens cleaning system operates from a battery power source 104 and is also advantageous in terms of reducing thermal stress on the transducer.
In certain implementations, moreover, the controller 130 selectively identifies a particular determined fault or degradation type according a specific frequency range of interest for which the dissimilarities indicate existence of the fault or degradation. In this manner, the driver 100 can selectively issue a FAULT/DEGRADATION signal to the host system 148 to initially indicate that there is degradation or a fault in the lens cleaning system, and also optionally identify the fault type according to particular dissimilarities. Such implementations facilitate providing advanced information to the host system 148 to indicate a particular fault or degradation type based on impedance response or more generally on frequency response. Such discernible types can include lens cracking or breaking, transducer cracking or depolarization, seal failure, glue failure, etc. The disclosed examples thus facilitate identification of when a failure has occurred in the lens cover system, as well as identification of failure type and the controller 130 and/or the host system 148 can provide appropriate corrective or remedial action. This design, in turn, facilitates improved readiness and availability of the lens cleaning system, by proactively identifying failure and allowing replacement of faulty or degrading system components so that system is operational at high availability.
Referring now to
Operation in the BASELINE mode begins at 302 in
The inventors have appreciated that faults and/or degradation of one or more components or aspects of the lens cleaning system can cause changes in the frequency spectrum of the impedance curve 402 and/or the phase spectrum curve 502. Disclosed systems and methods provide for automatically analyzing specific frequency ranges of interest 404 in order to ascertain the existence of one or more faults or degradation of the system. The disclosed examples, moreover, use the system components that are already present for cleaning purposes. The controller 130 in certain examples also implements calibration or “BASELINE” operation to characterize or calibrate the system with respect to a known or believed healthy system at 302 and 304. In one example at 304, the controller identifies one or more frequency ranges of interest that include a pole or zero of the baseline impedance profile that corresponds with an associated fault type or degradation type. In addition, as previously discussed, this characterization can be done at multiple operating voltages to establish baseline profiles for each operating voltage, and to identify one or more frequency ranges of interest for each baseline profile 150. In the example of
Continuing in
At 308 in
In another example, the controller 130 computes a sum of squares difference value based on the comparison, and selectively determines the existence of a fault or degradation in the lens cleaning system if the difference value exceeds a predetermined threshold. In certain examples, different thresholds can be used for different profiles and comparisons, with a specific threshold being used for each frequency range of interest, and for each operating transducer voltage. In one example, the controller 130 computes a root-mean-square (RMS) difference between the baseline and sweep frequency response values at the measured points, and compares this value with a corresponding threshold. If the controller 130 determines that all of the sweep profiles are similar to the corresponding baseline profiles (YES at 310), the process 300 returns to 306 as previously described.
The detection mode processing can be implemented at any suitable time in a normal operational implementation of a system. For example, a lens cleaning system may be instantiated or started according to a schedule established by the host system 148, such as periodic cleaning. The controller 130 in one example implements the fault/degradation detection operation at 306-310 is a prelude to actual cleaning. If the system is determined to be operational (e.g., no identified or determined faults or degradation), the controller 130 drives the transducer 102 in order to implement lens cleaning according to any suitable transducer drive parameters (e.g., voltage, frequency, duration, etc.) after the positive determination (YES at 310). The next time the lens cleaning system is actuated by the host system 148, the process is repeated.
If a threshold amount of dissimilarity is determined by the controller 130 in one or more of the frequency ranges 404 of interest (NO at 310), the process 300 continues at 312 where the controller 130 determines that a system fault or degradation exists. In certain examples, the controller 130 issues a system fault or degradation warning (e.g., provides the FAULT/DEGRADATION signal to the host system 148) at 313 in
The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.
Under 35 U.S.C. § 119, this application claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 62/415,554 that was filed on Nov. 1, 2016 and is entitled IMPEDANCE MONITORING TO DETECT FAILURES IN A LENS COVER SYSTEM, the entirety of which is incorporated by reference herein.
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