Controller, sensor and method for controlling transducer

Abstract

The invention relates to a controller, a sensor and a method for controlling a transducer. The sensors can incorporate ultrasonic cleaning device controllers and methods to maintain their exposed surfaces free of water, ice, and other adherends. An exemplary controller includes a driver configured to drive a transducer with a periodic waveform having voltage pulses and high impedance intervals repeating at a drive frequency. The controller may also include a receiver configured to measure a high impedance voltage of the transducer during the high impedance interval. The controller may also include control logic configured to adjust the drive frequency using the high impedance voltage to track a resonant frequency of the transducer. Some implementations enable tracking using diagnostic bursts with lower voltage pulse amplitudes and cleaning using cleaning bursts with higher voltage pulse amplitudes. A duty cycle attenuation may be employed to prevent voltage overshoot after each burst.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of Provisional U.S. Application 63 / 680,474, filed August 7, 2024, entitled “Ultrasonic Lens Cleaning Device”, by inventors Marek Hustava, Pavel Kostelnik, and Michal Navratil. The entire contents of the aforementioned application are incorporated herein by reference. Technical Field

[0003] This disclosure relates generally to sensor cleaning systems for vehicles. More specifically, this disclosure relates to systems and methods for controlling ultrasonic cleaning equipment to remove contaminants from the surfaces of camera lenses and other sensors in automotive applications. Background Technology

[0004] Modern vehicles are equipped with an astonishing number and variety of sensors to enable Advanced Driver Assistance Systems (ADAS) and autonomous driving capabilities. Cameras, radar, and lidar sensors are examples of such sensors that can be used to provide the environmental awareness required for such systems. However, the performance of these sensors is significantly reduced when their lenses or caps are blocked by water droplets, ice, snow, mud, or other contaminants. The reliability and safety of ADAS and autonomous driving systems depend on having unobstructed sensors.

[0005] Various sensor cleaning technologies have been developed, including mechanical wipers, high-pressure water / air / mist jets, and heating elements. However, these methods often have drawbacks, such as increased weight, high power consumption, or the need for additional components that may interfere with sensor operation. Ultrasonic cleaning devices (USCDs) have emerged as a promising solution, providing efficient cleaning with minimal additional components. However, existing USCD control systems may lack optimal efficiency, diagnostic capabilities, or adaptability to diverse environmental conditions. Summary of the Invention

[0006] Therefore, this document discloses exemplary controllers, methods, and sensors for cleaning surfaces using ultrasonic vibration. An exemplary controller includes a driver configured to drive a cleaning transducer using a periodic waveform having voltage pulses repeating at a drive frequency and high-impedance intervals. The controller may also include a receiver configured to measure a high-impedance voltage of the cleaning transducer during the high-impedance intervals. The controller may further include control logic configured to use the high-impedance voltage to adjust the drive frequency to track the resonant frequency of the cleaning transducer.

[0007] Another exemplary controller includes a driver configured to drive a cleaning transducer using a periodic waveform with voltage pulses. The exemplary controller also includes control logic that uses the periodic waveform to perform diagnostic operations to determine the resonant frequency of the cleaning transducer, and uses the periodic waveform to perform cleaning operations with voltage pulse amplitudes greater than those used for the diagnostic operations.

[0008] Another exemplary controller includes a driver configured to drive a cleaning transducer with a duty cycle having an initial value using a periodic waveform having voltage pulses and high impedance intervals. This exemplary controller also includes control logic configured to reduce the duty cycle of the periodic waveform to its pre-termination value before terminating the periodic waveform in a high impedance state.

[0009] The exemplary controller can execute the corresponding method and can be incorporated into an exemplary sensor having a lens surface exposed to the adhesive substance and a cleaning transducer configured to apply ultrasonic vibrations to the lens surface.

[0010] Each of the examples above can be used individually or in combination, and can include one or more of the following features in any suitable combination: 1. The voltage pulse may include a zero-voltage pulse and a non-zero-voltage pulse. 2. The controller can be configured to measure the low-impedance voltage of the cleaning transducer during a zero-voltage pulse. 3. The controller can determine whether the resonant frequency is greater than or less than the drive frequency based on the sign of the voltage difference between the high-impedance voltage and the low-impedance voltage. 4. The controller can be configured to adjust the drive frequency in steps not exceeding 20 Hz. 5. The resonant frequency may be the center frequency of the high Q peak dependent on the load of adhering material coupled to the lens surface of the cleaning transducer. 6. The controller can be configured to find the resonant frequency at startup or reset by scanning a predetermined frequency range to identify the resonant peak and performing cleaning operations to fine-tune the drive frequency. 7. The controller can be configured to perform periodic diagnostic operations to monitor the resonant frequency. 8. The controller can be configured to perform a de-icing operation if the resonant frequency exceeds a predetermined threshold. 9. The controller can be configured to perform a cleaning operation if the resonant frequency changes by more than a predetermined amount between diagnostic operations. 10. The diagnostic operation may have a non-zero voltage pulse with an amplitude reduced relative to the non-zero voltage pulse used for the cleaning operation. 11. The controller may include a variable voltage converter configured to provide a supply voltage for driving the cleaning transducer. 12. Control logic may be configured to temporarily raise the setpoint of the variable voltage converter while performing a cleaning operation. 13. The de-icing pulse amplitude is greater than the diagnostic pulse amplitude. 14. Control logic may be configured to temporarily raise the setpoint of the variable voltage converter while performing a de-icing operation. Attached Figure Description

[0011] Figure 1A This is an illustrative side view of a sensor equipped with an ultrasonic cleaning device (USCD).

[0012] Figure 1B This is a top view of an exemplary sensor.

[0013] Figure 2 This is an illustrative block diagram of a sensor equipped with a USCD.

[0014] Figure 3 This is a graph showing the displacement versus frequency of an exemplary USCD.

[0015] Figure 4 This is a graph showing the impedance versus frequency of an illustrative USCD at different temperatures.

[0016] Figure 5 This is a graph showing the impedance versus frequency of an exemplary USCD under different load conditions.

[0017] Figure 6 This is a timing diagram of an exemplary multi-state driver signal.

[0018] Figures 7A to 7C It is a graph showing different drive termination sequences.

[0019] Figure 8 It is a graph illustrating an exemplary automatic operation sequence.

[0020] Figure 9 This is a flowchart illustrating the USCD control method. Detailed Implementation

[0021] The accompanying drawings and the following description are not intended to limit this disclosure; rather, they provide a basis for those skilled in the art to understand all modifications, equivalents, and alternatives that fall within the scope of the claims.

[0022] Figure 1A and Figure 1BSide and top cross-sectional views of an exemplary camera with an integrated ultrasonic cleaning device (USCD) are shown. The camera includes a circuit board 102, which serves as a substrate for electronics and other components. The circuit board 102 may be, for example, a printed circuit board, an electronics packaging substrate, or a molded portion of a device housing on which the electronics are mounted. A housing 104 surrounds internal components and provides structural support. The housing 104 may include an aperture over which a lens 106 is mounted to focus an image onto the image sensing portion of the device's electronics. The upper surface of the lens 106 may be exposed to an external environment, which may include adhering substances (such as dust, dirt, water, ice, mud, snow, etc.) that can block or distort imaging light.

[0023] An integrated circuit 108 with an image sensor is mounted on a circuit board 102. The integrated circuit 108 may include a USCD controller and other control electronics for the camera. Adjacent to the integrated circuit 108 are one or more piezoelectric elements 110, which can generate vibrations for cleaning the lens 106.

[0024] The illustrated USCD includes one or more ribs or other support elements 112 that mechanically connect the piezoelectric element 110 to a support surface for the lens 106. This connection transmits ultrasonic vibrations from the piezoelectric element 110 to the lens 106 and its support surface, thereby providing mechanical energy to separate adhering material from the surface of the lens 106. This mechanical energy of the vibration can be further manipulated to melt, decompose, and / or disperse surface contaminants. Vibrating droplets 114 are displayed on the surface of the lens 106, representing moisture or debris that the device is designed to remove. Desired vibration frequencies may range from 20 kHz to 1 MHz, and drive signal power may range from 1 W to 100 W, or in some envisioned specific implementations from 5 W to 20 W. The USCD component includes a piezoelectric element 110, a rib 112, a support surface, and a lens 106. The piezoelectric element 110 can be configured to have a characteristic resonant frequency suitable for a desired application of the USCD, can be designed to provide a wide frequency response range, or can be provided with a support component that provides an adjustable resonant frequency or multiple available resonant frequencies.

[0025] The arrangement of components allows for a compact design, where the piezoelectric element 110 effectively transmits vibrations to the lens 106 for cleaning purposes, while the integrated circuit 108 controls the operation of the device. In other cases, the piezoelectric element 110 may be arranged in different locations within the device, or multiple piezoelectric elements may be used, depending on the specific requirements of the application. In at least some embodiments, additional discrete components are provided on the circuit board 102 to support the operation of the integrated circuit 108 and / or interface with the piezoelectric element 110.

[0026] Reference Figure 1B The diagram illustrates a top view of the circuit board 102. In some envisioned embodiments, the piezoelectric element 110 takes the form of a ring mounted on the circuit board 102. The piezoelectric element 110 may surround the integrated circuit 108.

[0027] In some cases, the circuit board 102 includes a protrusion 120 configured as an edge connector. The protrusion 120 may be printed with gold finger-like contacts and is configured to connect external wiring to the device's electronics. This arrangement allows for easy connection and disconnection of the device from external systems, such as wiring for receiving power and communicating with an external controller or host system. In other cases, the protrusion 120 may be replaced with other types of connectors or interfaces, depending on the specific requirements of the application.

[0028] Figure 2 A block diagram of an exemplary sensor equipped with a USCD is shown. The exemplary sensor includes a power management IC (PMIC) 202 that receives a 12V input and supplies a regulated 3.3V supply voltage to system components. A camera system-on-a-chip (CAM SOC) 204 performs the main sensor functions (e.g., image sensing and processing) and can communicate with the USCD via an I2C interface. The USCD is preferably implemented as a single-chip solution, for example, a transducer controller 206 having a piezoelectric element (PZ), a minimal number of discrete components (such as capacitors), and an optional quartz crystal (XTAL) for timing control.

[0029] The illustrated transducer controller 206 integrates various integrated circuit modules, including: a power supply module for distributing power to other controller components; an input / output (IO) module for receiving and providing digital signals via circuit board 102; a microcontroller unit (MCU) for implementing USCD control logic; a memory module (including, for example, RAM, ROM, EEPROM, OTP) for storing configuration parameter values, operating data, and firmware; an oscillator (OSC) module for clock generation with or without an external crystal; a DC-DC boost converter module 210 for generating selectable drive voltages; a voltage inverter 212; a four-state transducer driver 214; a programmable gain amplifier / attenuator (PGA) buffer 216; and an analog-to-digital converter (ADC).

[0030] Boost module 210 closes and opens a switch to alternately boost the current in inductor L and directs that current through a diode or transistor to increase the drive voltage +V on the first external capacitor. The ratio between the drive voltage +V and the 12V input voltage is determined by the duty cycle of the switch, allowing boost module 210 to control the drive voltage by changing the duty cycle setpoint. The boost module can use a first duty cycle setpoint with a value close to, for example, 0.95 to provide a 12.5V drive voltage for diagnostic operations. For cleaning or de-icing operations, the boost module can use a second duty cycle setpoint with a value close to, for example, 0.33 to provide a drive voltage of approximately 35V. Regardless of the drive voltage +V, voltage inverter 212 replicates the drive voltage to the second external capacitor, changing the sign to provide a negative drive voltage -V.

[0031] The multi-state transducer driver 214 includes: a first switch SW1 that selectively couples the drive terminal of the piezoelectric element PZ to a negative drive voltage -V; a second switch SW2 that selectively couples the drive terminal to ground; and a third switch SW3 that selectively couples the drive terminal to a positive supply voltage +V. If all three switches are open, the drive terminal remains in a high-impedance state. Therefore, the driver can provide four states: a high-impedance state, a positive voltage state, a negative voltage state, and a ground state. Unless otherwise stated, reference to the low-impedance state herein refers to the ground state.

[0032] Receiver 215 includes a buffer amplifier 216 to buffer the drive terminal voltage, thereby attenuating the voltage to avoid exceeding the input range of the ADC. This attenuation is preferably programmable to accommodate use with higher or lower drive voltages. The ADC senses the voltage V across the piezoelectric transducer. PZ The corresponding drive terminal voltage. Buffer 216 and ADC are merely an exemplary implementation of a receiver for sensing transducer voltage. Other digital and analog receiver implementations will also be suitable.

[0033] As an alternative to providing control logic using firmware configuration of a programmable MCU, the transducer controller 206 can be configured to operate the USCD using application-specific integrated circuit (ASIC)-based control logic circuitry with or without programmable parameters.

[0034] As a prelude to discussing preferred operations of the control logic, it should be noted here that existing techniques for resonant frequency tracking during transducer driving are ineffective or, at best, unreliable in many cases. The authors argue that these problems arise when the transducer configured for the desired operation exhibits multiple closely spaced resonant peaks. As an example, Figure 3A displacement versus frequency graph of an illustrative sensor equipped with a USCD is shown. The graph displays multiple resonance peaks, including a primary resonance 302 at approximately 485 kHz and a secondary resonance 304 at approximately 715 kHz. The secondary resonance, combined with a cluster of small resonances in the 490 kHz to 625 kHz range, prevents existing techniques from adaptively tracking the primary resonance when the transducer is driven. However, such tracking remains desirable.

[0035] Figure 4 This is a graph showing the impedance of an exemplary piezoelectric transducer with a resonant peak in the range of 23 kHz to 24 kHz. At room temperature (25°C), the peak is nominally at 23.6 kHz, but... Figure 4 As shown, the peak exhibits a significant shift with temperature, ranging from as high as 23.8 kHz at -40°C to as low as 23.3 kHz at 115°C. Assuming a full width at half maximum (FWHM) peak width of less than 0.06 kHz, these temperature shifts can effectively place the drive signal at the nominal resonant frequency well outside the current resonant frequency peak, rendering the USCD largely ineffective. To maximize performance and power efficiency, the control logic can adapt the drive signal frequency to track the resonant frequency peak during operation.

[0036] In addition to temperature dependence, the USCD is expected to be dependent on the sensor's load conditions. Figure 5 The impedance of an exemplary USCD transducer at 0°C is shown. The nominal resonant frequency peak of the clean, unloaded (UNL) transducer is at 23.69 kHz. When liquid water droplets (LIQ) adhere to the sensor surface, the transducer's resonant frequency peak shifts to approximately 23.62 kHz. Conversely, when a thin layer of ice (ICE) adheres to the sensor surface, the transducer's resonant frequency peak shifts to 23.81 kHz. The control logic can use this dependence to detect sensor load. Note that when the adhered material is atomized or otherwise dispersed, the resonant frequency peak will shift backward from the nominal value. To maximize performance and power efficiency, the control logic can accordingly adapt the frequency of the drive signal to track the resonant frequency peak during cleaning and de-icing operations.

[0037] Combination Figures 3 to 5It can be noted that the USCD can be designed to provide a narrow resonant peak, i.e., a resonance with a quality factor of quality (e.g., close to or greater than Q = 900). Such a narrow peak provides efficient conversion of drive energy to produce a relatively large surface displacement, which can provide more efficient cleaning operation. However, the result is a close correspondence between the desired peak frequency and the drive frequency, since the desired displacement can only be achieved within a small range of drive frequencies. Therefore, the control logic can be configured to adapt to the drive frequency in real time to track the resonant frequency peak as closely as possible, and those controllers using digital frequency control can be configured to use a small adaptation step size. Suitable step sizes can be 20 Hz or less, more preferably 10 Hz or less, or 5 Hz or less, or optimally about 3 Hz or less.

[0038] Figure 6 This is a timing diagram illustrating the operation of the multi-state driver 206. The first signal diagram shows the control signal for switch SW1, which is asserted to selectively couple the drive terminal to the negative drive voltage -V. The second signal diagram shows the control signal for switch SW2, which is asserted to selectively couple the drive terminal to ground. The third signal diagram shows the control signal for switch SW3, which is asserted to selectively couple the drive terminal to the positive drive voltage +V. When all three control signals are deasserted, the drive terminal is decoupled, i.e., the driver is in a high-impedance state.

[0039] The fourth signal diagram is the drive terminal voltage waveform V. PZ The waveform is periodic. Interval 602 corresponds to one cycle of this waveform. The illustrated intervals include two low-impedance intervals 604 and 614 corresponding to the assertion of the SW2 control signal. Intervals 604 and 614 are immediately followed by non-zero voltage pulse intervals 606 and 616. Interval 606 is a positive voltage pulse corresponding to the assertion of the SW3 control signal. Interval 616 is a negative voltage pulse corresponding to the assertion of the SW1 control signal. The non-zero voltage pulse intervals 606 and 616 are immediately followed by high-impedance intervals 608 and 618 corresponding to the release assertions of the three switch control signals.

[0040] A non-zero voltage pulse initiates the expansion and contraction of the piezoelectric element. The element acquires momentum that continues even after the non-zero voltage pulse has terminated, causing the transducer voltage to decay. If interval 602 perfectly matches the period of the resonant frequency peak, the momentum of the piezoelectric element (and the residual voltage at the drive terminals) converges to zero as the low-impedance intervals 604 and 614 begin. If interval 602 is too short, the low-impedance intervals 604 and 614 begin before the drive terminal voltage converges to zero. Conversely, if interval 602 is too long, the drive terminal voltage exhibits a sign change before the low-impedance interval begins. Therefore, the transducer voltage V is affected precisely during the high-impedance interval preceding the low-impedance interval. PZThe waveform measurement allows the control logic to determine whether period 602 is too long or too short, and thus whether the drive frequency is too low or too high. In practice, some baseline drift may occur over time, so it may be preferable to measure the transducer voltage waveform just before and after the start of the low-impedance interval, and to adapt the drive frequency based on the difference between the two measurements.

[0041] exist Figure 6 In this example, a transducer waveform measurement 620 is acquired near the end of the high-impedance interval 608, and a second measurement 622 is acquired near the middle of the low-impedance interval 614. The control logic determines the differential voltage Vdiff by subtracting the low-impedance voltage measurement 622 from the high-impedance voltage measurement. If the sign of the differential voltage Vdiff is positive, the control logic can adjust the drive frequency downwards. Conversely, if the sign of the differential voltage is negative, the control logic can adjust the drive frequency upwards. It should be noted that measurements 620 and 622 are acquired near the end of the positive half of the transducer voltage waveform. If acquired near the end of the negative half of the transducer voltage waveform, the sign of the differential voltage should be reversed, or equivalently, the differential voltage should be calculated by subtracting the high-impedance voltage measurement from the low-impedance voltage measurement. According to standard adaptive control techniques, multiple differential voltages can be accumulated and / or filtered over multiple cycles of the waveform to determine an adaptation signal indicating whether the drive frequency should be increased or decreased.

[0042] In combination Figures 8 to 9 Before discussing the optimal operation of the control logic, we first discuss how the transducer voltage waveform V can be optimized. PZ A burst of vibration is generated by supplying the drive terminals of the piezoelectric element. In the initial state, the transducer may be stationary, and the driver 206 remains in a high-impedance state. When cleaning operation is desired, the driver may supply a non-zero voltage pulse at an initial frequency, which is then adapted to match the resonant frequency peak of the transducer to maximize the displacement and energy transfer of any material adhering to the surface of the sensor. The transducer vibrates at the drive frequency. When the sequence of non-zero voltage pulses terminates, for example, when the driver 206 enters a high-impedance state, the residual vibration of the transducer can generate a sinusoidal voltage signal with a gradually decaying envelope.

[0043] As the transducer gradually dissipates the stored vibrational energy, the initial amplitude of the residual vibrational signal may far exceed the amplitude of the non-zero voltage pulse, especially at the high-Q resonance peak. This is Figure 7A The examples shown in the text. Figures 7A to 7C Each of these examples illustrates the termination of a 0.5s long waveform with a positive 35V pulse and a negative 35V pulse at a drive frequency close to 23.6kHz. Figure 7AIn this state, the driver 206 immediately transitions from a burst waveform to a high-impedance state. The residual vibration of the transducer generates a sinusoidal voltage that gradually decays to near zero at 0.6s before peaking at approximately 70V. Due to voltage stress, this voltage peak presents the potential to damage the driver transistor and / or shorten the device's lifespan.

[0044] Figure 7B A preferred termination method is shown, in which driver 206 transitions to a ground state at the end of the vibration burst waveform. This ground state can be maintained until sufficient residual vibration energy has been dissipated to keep the residual vibration signal below the amplitude of the non-zero voltage drive pulse. In this example, driver 206 maintains the ground state for 0.06 s before transitioning to a high-impedance state at 0.56 s. This technique avoids voltage stress on the driver transistor without prolonging the USDC's vibration due to the rapid energy dissipation level in the ground state.

[0045] Figure 7C An alternative termination method is shown, in which, at the end of the 0.5s burst waveform, the control logic begins to reduce the waveform duty cycle from approximately 0.4 to approximately 0.08 in a step-linear manner, and then transitions to a high-impedance state at 0.522s. The residual vibration signal is similar to... Figure 7B Attenuation in a manner that, but with more than Figure 7A The signal is a prolonged vibration. With Figure 7B Similarly, this avoids excessive voltage stress on the driving transistor.

[0046] Figure 8 An exemplary transducer waveform 800 is provided to offer an overview of the desired USCD operation. A boost voltage 801 is also shown, reflecting the dynamic supply voltage setpoints for the positive and negative drive voltages. Initially, the boost voltage 801 is set to a default level suitable for a non-zero voltage pulse used for diagnostic operation. The illustrated level is at 13V, but larger and smaller voltage levels are expected to be appropriate. The preferred default level will provide sufficient sensitivity for tracking the resonant frequency peak (and thus detecting any adhering material) while minimizing power consumption.

[0047] The transducer is initially stationary, and the driver 206 remains in a high-impedance state. Periodically, the control logic generates diagnostic vibration bursts and dynamically adapts the drive frequency to match the resonant frequency peak, thus enabling the control logic to track the resonant frequency peak and any changes thereto. The illustrated burst duration 802 is 200 ms, followed by a 25 ms interval during which the driver 206 transitions to ground (termination method 7B) and the associated residual vibration signal decays within 75 ms. Figure 8Assume termination method 7B is used after each diagnostic or cleaning burst. A delay interval 804 is provided after each diagnostic vibration burst. The illustrated delay interval 804 is approximately 1 second, but can be changed to minimize power consumption while still taking into account the maximum expected rate of change of the resonant frequency peak.

[0048] In this example, it is assumed that the control logic detects a significant change in the resonant frequency peak using a second diagnostic burst and initiates a cleaning operation accordingly. This cleaning operation begins with a change in the supply voltage setpoint, causing the boost voltage 801 to ramp up during interval 806. Once a sufficient supply voltage (e.g., 35V) is reached, the control logic performs the cleaning operation during interval 810.

[0049] The illustrated cleaning operation involves a 3.0s vibration burst waveform using a non-zero pulse amplitude of approximately 35V. The control logic adapts to the drive frequency to track the resonant frequency peak, thereby maximizing energy transfer to any adhered material even when the transducer load is reduced. The illustrative cleaning burst waveform may include a 7B termination cycle and may be followed by a residual vibration decay signal lasting less than 100ms. At the end of the cleaning burst waveform, the control logic can return the supply voltage setpoint to its default value, allowing the boost voltage 801 to gradually decrease back to its default level. After a driver cooling interval 812, shown here as approximately 1s, the control logic returns to generating periodic diagnostic bursts 814, 816. Diagnostic burst 814 is shown to be transmitted before the boost voltage 801 has fully returned to its default level, resulting in the use of an increased diagnostic pulse amplitude, but the control logic functions as before to track any changes in the resonant frequency peak.

[0050] Figure 9 This is a flowchart illustrating an exemplary method for implementing USCD functionality in a suitably equipped sensor, which can be achieved by control logic. The method begins at block 901, where power-on or reset triggers a scan of a predetermined frequency range (selected to cover all expected operating conditions) to identify strong resonant peaks. The scan can be “fast,” i.e., using a relatively large step size to enable rapid identification of high-amplitude resonant peaks. In the case of identifying multiple peaks, the peak with the largest amplitude can be selected. Envisioned step sizes include 25Hz, 35Hz, 50Hz, and 100Hz. In some specific implementations, the control logic employs an adaptive step size or a recursive search to narrower the search to peaks close to those previously identified. In block 902, the control logic sets the initial drive frequency to correspond to one of the resonant peaks.

[0051] In block 904, the control logic adjusts the supply voltage setpoint to prepare for a clean burst. For example, the supply voltage setpoint can be set to 35V to provide a clean burst waveform with a non-zero voltage pulse of approximately 35V amplitude. Once the desired supply voltage is reached, the control logic in block 906 begins supplying the clean burst waveform to the transducer. Note that in some implementations, the control logic can provide a gradually changing (rather than) clean burst waveform. Figure 6 The pulse shaping (as shown in the abrupt transition) minimizes the emission of potential electromagnetic interference (EMI) energy. In block 908, the control logic obtains a transducer voltage measurement during the high-impedance interval of the waveform, and preferably also during the associated low-impedance interval of the waveform. In block 910, the control logic adapts the drive frequency of the clean burst waveform. As previously discussed, the frequency can be adapted based on the high-impedance voltage measurement or based on the difference between the high-impedance voltage measurement and the low-impedance voltage measurement. This adaptation allows for fine-tuning of the drive frequency to better match the resonant peak frequency.

[0052] In block 912, the control logic determines whether the cleaning burst should be terminated. Various criteria can be used for this determination. For example, the control logic can employ a timer or a loop counter to limit the cleaning burst to a fixed duration. Alternatively, the control logic can determine whether the resonant frequency has converged to a stable or predetermined value indicating a clean, dry transducer surface free of adhering material. The control logic loops through blocks 906-912 until burst termination is required. Since the expected rate of convergence to the resonant peak is much faster than any frequency drift at that peak, blocks 908 and 910 do not need to be executed for every drive pulse in a given burst, but can instead be executed intermittently, for example, during one pulse of each of a predefined number of pulses.

[0053] Once the control logic decides to terminate the cleaning burst, in block 914, the control logic can be combined as previously described. Figure 7B or Figure 7C The burst is terminated as described. Once the burst termination is complete, the control logic stops driving the transducer (e.g., sets the driver to a high-impedance state) and sets the supply voltage setpoint in block 916 to a default value suitable for diagnosing the burst. For example, the supply voltage setpoint could be set to 13V to provide a diagnostic burst waveform with a non-zero voltage pulse of approximately 12V amplitude.

[0054] In block 918, the control logic holds the driver in a high-impedance state until sufficient time has elapsed before sending the diagnostic burst. Once sufficient time has elapsed, the control logic begins supplying the diagnostic burst waveform to the transducer in block 920. As previously mentioned, some implementations of the control logic may provide pulse shaping to minimize EMI emissions. In block 922, the control logic obtains a transducer voltage measurement during the high-impedance interval of the waveform, and preferably also during the associated low-impedance interval of the waveform. In block 924, the control logic adapts to the drive frequency of the diagnostic burst waveform. In block 926, the control logic determines whether the diagnostic burst should be terminated. For example, the control logic may employ a timer or a loop counter to limit the diagnostic burst to a fixed duration. The control logic loops through blocks 920-926 until burst termination is required. In some implementations, blocks 922 and 924 are executed intermittently.

[0055] Once the control logic decides to terminate the diagnostic burst, in block 928, the control logic can use the previously described termination method (such as...) Figure 7B or Figure 7C The burst is terminated using a termination method. Once termination is complete, the control logic stops driving the transducer (e.g., sets the driver to a high-impedance state).

[0056] In block 930, the control logic evaluates the current value of the drive frequency and compares it with a predetermined threshold f indicating the presence of ice on the exposed surface of the transducer. ICE A comparison is made. If the drive frequency does not exceed a threshold, then in box 932, the control logic determines whether the current value of the drive frequency has changed by more than a threshold amount relative to a previous drive frequency value. The previous drive frequency value could be, for example, the adaptation frequency at the end of the most recent cleaning burst. Alternatively, the previous value could be the drive frequency at the end of the previous burst (whether diagnostic or cleaning). If the change does not exceed the threshold, the control logic returns to box 918. If the change exceeds the threshold, the control logic returns to box 904 to perform the cleaning operation.

[0057] Return to box 930, if the drive frequency exceeds f ICEIf the threshold is reached, the control logic transitions to block 934 to adjust the supply voltage setpoint in preparation for the de-icing burst. For example, the supply voltage setpoint may be set to 35V to provide a de-icing burst waveform with a non-zero voltage pulse of approximately 35V amplitude. In some implementations, the supply voltage for de-icing operations may be higher than that for cleaning operations, and the burst duration may be longer. Once the desired supply voltage is reached, the control logic in block 935 can perform a rapid scan to identify resonant peaks within a predetermined frequency range suitable for the de-icing operation. The control logic sets the drive frequency to correspond to the resonant peak. If multiple peaks are identified, the control logic can select the peak with the largest amplitude. The control logic in block 936 begins supplying the de-icing burst waveform to the transducer. In block 938, the control logic obtains a transducer voltage measurement during the high-impedance interval of the waveform, and preferably also during the associated low-impedance interval of the waveform. In block 940, the control logic adapts the drive frequency of the de-icing burst waveform.

[0058] In block 942, the control logic determines whether the de-icing burst should be terminated. Various criteria can be used for this determination. For example, the control logic can use a timer or a loop counter to limit the de-icing burst to a fixed duration. Alternatively, the control logic can determine whether the resonant frequency has converged to a stable or predetermined value indicating a clean, dry transducer surface free of adhering material. The control logic loops through blocks 936-942 until burst termination is required. In some implementations, blocks 938 and 940 can be executed intermittently to improve efficiency.

[0059] Once the control logic decides to terminate the de-icing burst, in block 944, the control logic can employ an appropriate termination method (such as combining...). Figure 7B and Figure 7C The burst is terminated using the described termination method. Once the burst termination is complete, the control logic stops driving the transducer (e.g., sets the driver to a high-impedance state) and returns to block 904.

[0060] Although for illustrative purposes, Figure 9 The described operations are shown in sequential order, but these operations can actually be reordered and / or performed concurrently. While the above disclosure has focused on automotive applications, the principles described herein can be applied to other situations requiring sensor surface or lens cleaning, such as security cameras, industrial inspection systems, or medical imaging equipment.

Claims

1. A controller, the controller comprising: A driver configured to drive a transducer using a periodic waveform having voltage pulses repeating at a driving frequency and high impedance intervals. A receiver configured to measure the high impedance voltage of the transducer during the high impedance interval; and Control logic configured to use the high impedance voltage to adjust the drive frequency to track the resonant frequency of the transducer.

2. The controller of claim 1, wherein the voltage pulse includes a zero-voltage pulse and a non-zero-voltage pulse, wherein the receiver is configured to measure the low-impedance voltage of the transducer during the zero-voltage pulse, and wherein the control logic determines whether the resonant frequency is greater than or less than the drive frequency based on the sign of the voltage difference between the high-impedance voltage and the low-impedance voltage.

3. The controller of claim 2, wherein the control logic is configured to adjust the drive frequency in steps not exceeding 20 Hz.

4. The controller according to claim 2, wherein the resonant frequency is determined by the center frequency of the high Q peak of the adhesive material load coupled to the lens surface of the transducer.

5. The controller of claim 2, wherein the control logic is configured to find the resonant frequency at startup or reset by scanning a predetermined frequency range to find the resonant peak and performing an initial cleaning operation to fine-tune the drive frequency.

6. The controller of claim 5, wherein the control logic is configured to perform periodic diagnostic operations to monitor the resonant frequency.

7. The controller of claim 6, wherein the control logic is configured to perform a de-icing operation when the resonant frequency exceeds a predetermined threshold.

8. The controller of claim 6, wherein the control logic is configured to perform a cleaning operation if the resonant frequency changes by more than a predetermined amount between diagnostic operations.

9. The controller of claim 6, wherein the diagnostic operation has a non-zero voltage pulse with an amplitude reduced relative to the non-zero voltage pulse used for cleaning operation.

10. A method for controlling a transducer, the method comprising: A transducer is driven using a periodic waveform having voltage pulses that repeat at a driving frequency and high impedance intervals, and the transducer is configured to apply ultrasonic vibrations to the lens surface. The resonant frequency of the transducer is determined to be greater than or less than the driving frequency based on the high impedance voltage of the transducer during the high impedance interval. as well as The driving frequency is adjusted during the driving process to track the resonant frequency.

11. The method of claim 10, wherein the voltage pulse includes a zero-voltage pulse and a non-zero-voltage pulse, and wherein the method further comprises: The low impedance voltage of the transducer was measured during the zero-voltage pulse, and The determination of whether the resonant frequency of the transducer is greater than or less than the drive frequency is based on the sign of the voltage difference between the high impedance voltage and the low impedance voltage.

12. The method of claim 11, further comprising finding the resonant frequency at startup or reset by scanning a predetermined frequency range to find a resonant peak and performing an initial cleaning operation to fine-tune the drive frequency.

13. The method of claim 11, further comprising: Perform periodic diagnostic operations to monitor the resonant frequency; De-icing is performed when the resonant frequency exceeds a predetermined threshold. as well as A cleaning operation is performed if the resonant frequency changes by more than a predetermined amount between diagnostic operations.

14. The method of claim 13, wherein the diagnostic operation has a non-zero voltage pulse with an amplitude reduced relative to the amplitude of the non-zero voltage pulse used for the cleaning operation.

15. A sensor, the sensor comprising: Lens surface, the lens surface being configured to be exposed to an adhesive substance; A transducer configured to apply ultrasonic vibrations to the lens surface; and The controller is configured to perform a cleaning operation through the following steps: The transducer is driven using a periodic waveform, which has voltage pulses repeating at a driving frequency and high impedance intervals. The resonant frequency of the transducer is determined to be greater than or less than the driving frequency based on the high impedance voltage of the transducer during the high impedance interval. as well as The driving frequency is adjusted during the driving process to track the resonant frequency.

16. The sensor of claim 15, wherein the voltage pulse includes a zero-voltage pulse and a non-zero-voltage pulse, wherein the controller is configured to measure the low-impedance voltage of the transducer during the zero-voltage pulse, and wherein the controller determines whether the resonant frequency is greater than or less than the drive frequency based on the sign of the voltage difference between the high-impedance voltage and the low-impedance voltage.

17. The sensor of claim 16, wherein the controller is configured to optimize operation by: Finding the resonant frequency at startup or reset, the finding includes: Scan a predetermined frequency range to find the resonance peak; And perform initial cleaning operations to fine-tune the drive frequency; Perform periodic diagnostic operations to monitor the resonant frequency; De-icing is performed when the resonant frequency exceeds a predetermined threshold. as well as The cleaning operation is performed if the resonant frequency changes by more than a predetermined amount between diagnostic operations.

18. The sensor of claim 17, wherein the diagnostic operation has a non-zero voltage pulse with an amplitude reduced relative to the amplitude of the non-zero voltage pulse used for the cleaning operation.

19. The sensor of claim 15, wherein the controller is configured to perform the adjustment of the drive frequency using a step size not exceeding 20 Hz.

20. The sensor of claim 15, wherein the resonant frequency is the center frequency of the high Q peak dependent on the adhesive material load on the lens surface.

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