Cleaning for rotating sensors

Aspects of the disclosure relate to cleaning rotating sensors having a sensor housing with a sensor input surface. For instance, a first signal indicating that there is a contaminant on the sensor input surface may be received. In response to receiving the first signal, a second signal may be sent in order to cause one or more transducers to generate waves in order to attempt to remove the contaminant from the sensor input surface.

BACKGROUND

Various types of vehicles, such as cars, trucks, motorcycles, busses, boats, airplanes, helicopters, lawn mowers, recreational vehicles, amusement park vehicles, farm equipment, construction equipment, trams, golf carts, trains, trolleys, etc., may be equipped with various types of sensors in order to detect objects in the vehicle's environment. For example, vehicles, such as autonomous vehicles, may include such LIDAR, radar, sonar, camera, or other such imaging sensors that scan and record data from the vehicle's environment. Sensor data from one or more of these sensors may be used to detect objects and their respective characteristics (position, shape, heading, speed, etc.).

However, these vehicles are often subjected to environmental elements such as rain, snow, dirt, etc., which can cause a buildup of contaminants such as foreign object debris, including as water, dirt, etc., on these sensors. Typically, the sensors include a housing to protect the internal sensor components of the sensors from the contaminants, but over time, the housing itself may become dirty. As such, the functions of the sensor components may be impeded as signals transmitted and received by the internal sensor components are blocked by the contaminants.

BRIEF SUMMARY

One aspect of the disclosure provides a method for cleaning a sensor, the sensor including a rotating sensor housing with a sensor input surface. The method includes receiving, by one or more processors, a first signal indicating that there is a contaminant on the sensor input surface, and in response to receiving the first signal, sending, by the one or more processors, a second signal in order to cause one or more transducers to generate waves in order to attempt to remove the contaminant from the sensor input surface.

In one example, the first signal further indicates a location of the contaminant on the sensor input surface. In another example, the method also includes in response to receiving the second signal, sending a third signal to cause a liquid nozzle to provide a spray of liquid cleaning fluid on the sensor input surface. In this example, sending the third signal further causes an air nozzle to provide a puff of gas on the sensor input surface. In another example, the second signal further causes a liquid nozzle to provide a spray of liquid cleaning fluid on the sensor input surface. In this example, the method also includes sending a third signal to cause an air nozzle to provide a puff of gas on the sensor input surface. In another example, the first signal further indicates a type of the contaminant and wherein sending the second signal is further based on the type of contaminant. In this example, the method also includes, controlling a ratio of standing waves to traveling waves generated by the one or more transducers based on the type of contaminant. In addition, the method also includes initially, maximizing the ratio of standing waves to traveling waves to perform a cleaning function and thereafter minimizing the ratio of standing waves to traveling waves to perform a clearing function. In addition or alternatively, when the type of contaminant is water, the method further comprises, minimizing the ratio of standing waves to traveling waves to perform a clearing function. Alternatively, when the type of contaminant is other than water, the method further comprises, maximizing the ratio of standing waves to traveling waves to perform a cleaning function. In another example, the method also includes, generating the first signal based on impedance information from the one or more transducers.

Another aspect of the disclosure provides a system for cleaning a sensor. The sensor including a rotating sensor housing with a sensor input surface. The system includes one or more transducers and one or more processors. The one or more processors are configured to receive, by one or more processors, a first signal indicating that there is a contaminant on the sensor input surface, and in response to receiving the first signal, sending a second signal to cause the one or more transducers to generate waves in order to attempt to remove the contaminant from the sensor input surface.

In one example, the first signal further indicates a location of the contaminant on the sensor input surface. In another example, the one or more transducers include exactly three transducers. In another example, the one or more transducers include at least one pair of transducers. In this example, the at least one pair of transducers includes at least one higher frequency transducer and at least one lower frequency transducer. In another example, the one or more transducers include a convex shape. In another example, the one or more transducers include a concave shape. In another example, the first signal further indicates a type of the contaminant and wherein sending the second signal is further based on the type of contaminant, and the method further comprises, controlling a ratio of standing waves to traveling waves generated by the one or more transducers based on the type of contaminant.

DETAILED DESCRIPTION

Overview

The technology relates to an ultrasonic cleaning system for a rotating sensor mounted on a vehicle, such as an autonomous vehicle. The sensor may be a LIDAR, camera, radar, sonar or other sensor which includes a sensor housing which rotates relative to the vehicle. The sensor housing may house the internal components of the sensor and may include a sensor input surface through which signals may be sent and received. If the sensor input surface becomes partially or completely occluded by contaminants such as foreign object debris, including water, dirt, etc., the sensor's ability to detect and identify objects in the vehicle's environment may become degraded. Because detecting and identifying objects is a critical function for an autonomous vehicle, clearing such foreign object debris can also become critically important.

A sensor may be arranged or mounted at various locations on the vehicle. The sensor may include a housing310to protect internal sensor components360from by contaminants such as foreign object debris, including water, dirt, insects, and other contaminants. However, over time, the housing and other sensor components may collect contaminants. As such, the functions of internal sensor components may be impeded as signals transmitted and received by the internal sensor components may be blocked by the contaminants. To address this, contaminants may be cleared from the sensor by rotating the internal sensor components within the housing. In some instances, this rotation may enable one or more wipers to clear any contaminants on a sensor input surface of the sensor.

To provide cleaning and clearing functionality for the sensor, an ultrasonic cleaning system may be used. For instance, cleaning may refer to detaching contaminants from the sensor input surface which are chemically attached by causing cavitation through liquid over the sensor input surface. When an organic contaminant hits the sensor input surface, compounds may chemically bond to the surface making such compounds difficult to remove. With the ultrasonic cleaning system, liquid cleaning fluid may be added to the sensor input surface and ultrasonic waves may move the glass. This may occur with such speed that fluids, such as liquid cleaning fluid, may cavitate, resulting in a “cold boil” or a boiling caused by low pressure as opposed to high heat. This boiling action may actually result in a cleaning function or effect as vapor bubbles created by the cold boil collapse with great force “chipping” the contaminates from the sensor input surface. This action can be maximized by actively creating standing waves over the sensor input surface. The clearing function may refer to propelling droplets of precipitation which are not chemically bonded to the sensor input surface. This action can be maximized by actively creating traveling waves or increasing the number of traveling waves generated as compared to standing waves. Thus, by controlling a ratio of standing to traveling waves, the ultrasonic cleaning system can provide both cleaning and clearing functions, and thereby achieving a clear or nearly clear sensor input surface with little to no contaminants.

The ultrasonic cleaning system may include a liquid nozzle, an air nozzle420, one or more controllers, and one or more transducers. The liquid nozzle may be connected to a reservoir storing liquid cleaning fluid. A liquid pump may be configured to pump liquid cleaning fluid from the reservoir through a liquid valve, tubing, and out of the liquid nozzle in order to clean the sensor input surface. The liquid nozzle may be arranged at different locations around the sensor.

In all arrangements of the liquid nozzle, the rotation of the sensor housing may help to clear the liquid cleaning fluid from the sensor input surface. However, the rotation may not be enough to ensure that the liquid cleaning fluid is fully removed from the sensor input surface. As such, the air nozzle may generate a puff of fluid, such as air or another gas, in order to force the liquid cleaning fluid off of the sensor input surface. To do so, an air pump may be configured to pump air through an air valve, tubing, and out of the air nozzle in order to clean the sensor input surface.

The controllers may include one or more computing devices having one or more processors and memory. The controllers may be configured to receive, and act upon, various signals. For example, a controller may be configured to receive feedback from a position sensor indicating the position of the sensor. From this information as well as the rotation speed of the sensor housing, a controller may determine the current position, for example the current angular position, of the sensor input surface at any given point in time.

The controllers may also receive signals from the sensor and/or other computing devices of the vehicle indicating the current state of the sensor. In some aspects, a controller may use the current position of the sensor input surface to determine exactly when and how to activate the transducers in order to provide cleaning and/or clearing functions. In addition or alternatively, a controller may use the current position of the sensor input surface to determine exactly when to activate the liquid pump and the air pump as well as to open the air and liquid valves in order to both apply liquid cleaning fluid to the sensor input surface as well as to clear the cleaning fluid from the sensor input surface using a puff of gas.

The transducer may be arranged in any number of different configurations. Each configuration may be associated with different benefits and/or drawbacks and may be selected based upon where (e.g. geographically) a particular sensor is being used or for which function (cleaning or clearing) the ultrasonic cleaning system is to be optimized. For instance, pairs of transducers may be better able to generate standing wavers and thus may do a better job of creating a local pressure difference at different locations on the sensor input surface, thereby providing a better clearing function. In this regard, a single transducer (i.e. one of a plurality of transducers or only a single transducer), may be used to generate more traveling waves as compared to standing waves when attempting to provide a cleaning function. In addition, more than one transducer can be used for the cleaning and clearing functions using different activation timing.

The exact frequencies of the transducers used may be dependent upon the configuration and characteristics of the sensor input surface. For instance, the sensor input surface may be formed from glass. Some glass may work with many ranges of frequencies depending upon the acoustic properties of the glass including the longitudinal wave speed and shear wave speed. This combination of wave speeds will provide a different in and out of plane motion over the glass surface.

To affect the cleaning and/or clearing of the sensor input surface, a first signal may be received by one or more processors indicating that there is a contaminant on the sensor input surface. This first signal may be received from the sensor status system based on any number of different inputs including a degraded signal from the sensor, camera images of the sensor input surface, and/or feedback from the transistors. This feedback may also be used to determine a type of contamination on the sensor input surface.

In response to receiving the first signal, a second signal may be sent to cause a transducer to generate waves in order to attempt to remove the contaminant from the sensor input surface. In this regard, the ultrasonic cleaning system may activate the ultrasonic cleaning and/or clearing functions of the transducers. For instance, a controller may activate the transducers based on the type of contaminant to generate waves, for instance to increase or decrease the ratio of standing waves to traveling waves in order to promote clearing or cleaning. In some instances, in addition, the ultrasonic cleaning system may activate liquid nozzle and air nozzle (if used). In this regard, the liquid nozzle may provide a spray of liquid cleaning fluid to attempt to clean contaminants from the sensor input surface, and the air nozzle may provide a puff of gas to remove liquid cleaning fluid and/or contaminants from the sensor input surface.

In addition, once the liquid nozzle has generated the spray of liquid cleaning fluid, the controller may activate the transducers in order to generate traveling waves according to the clearing function (or decrease the ratio of standing waves to traveling waves). In this regard, individual transducers may be activated at different times in order to generate more traveling waves and thereby, in conjunction with the rotation of the sensor housing as well as the puff of gas generated by the air nozzle (if used), to cause the liquid solution, contaminants and other fluids to be removed from the sensor input surface. As a result, the sensor input surface may return to optimal (clean) or near optimal performance. This cleaning and clearing may be repeated as needed to reduce or keep the sensor input surface clear of contaminants.

The features described herein may provide for a useful and practical approach to cleaning rotating sensors. The combination of cleaning and clearing functionality of the ultrasonic cleaning features described herein may provide significant improvements over other systems without such features. Moreover, the use of ultrasonic cleaning may also reduce the amount of liquid cleaning solution needed to remove contaminants from a sensor input surface. In addition, the use of the impedance information to detect contaminants may obviate the need for additional devices, (e.g., a camera) to serve the same purpose and thereby save power and other resources on the vehicle. Other benefits may include potentially, better reliability of the ultrasonic cleaning system (due to fewer mechanical parts), lower cost (once having more integrated design and mass produced), smaller (as the transducers can be miniature), as well as a simplified construction with fewer maintenance requirements than other cleaning and clearing approaches with more hardware and more potential points of failure.

Example Systems

As shown inFIG.1, a vehicle100in accordance with one aspect of the disclosure includes various components. While certain aspects of the disclosure are particularly useful in connection with specific types of vehicles, the vehicle may be any type of vehicle including, but not limited to, cars, trucks, motorcycles, busses, recreational vehicles, etc. The vehicle may have one or more computing devices, such as computing device110containing one or more processors120, memory130and other components typically present in general purpose computing devices.

The data134may be retrieved, stored or modified by processor120in accordance with the instructions132. As an example, data134of memory130may store predefined scenarios. A given scenario may identify a set of scenario requirements including a type of object, a range of locations of the object relative to the vehicle, as well as other factors such as whether the autonomous vehicle is able to maneuver around the object, whether the object is using a turn signal, the condition of a traffic light relevant to the current location of the object, whether the object is approaching a stop sign, etc. The requirements may include discrete values, such as “right turn signal is on” or “in a right turn only lane”, or ranges of values such as “having a heading that is oriented at an angle that is 20 to 60 degrees offset from a current path of vehicle100.” In some examples, the predetermined scenarios may include similar information for multiple objects.

The one or more processor120may be any conventional processors, such as commercially available CPUs. Alternatively, the one or more processors may be a dedicated device such as an ASIC or other hardware-based processor. AlthoughFIG.1functionally illustrates the processor, memory, and other elements of computing device110as being within the same block, it will be understood by those of ordinary skill in the art that the processor, computing device, or memory may actually include multiple processors, computing devices, or memories that may or may not be stored within the same physical housing. As an example, internal electronic display152may be controlled by a dedicated computing device having its own processor or central processing unit (CPU), memory, etc. which may interface with the computing device110via a high-bandwidth or other network connection. In some examples, this computing device may be a user interface computing device which can communicate with a user's client device. Similarly, the memory may be a hard drive or other storage media located in a housing different from that of computing device110. Accordingly, references to a processor or computing device will be understood to include references to a collection of processors or computing devices or memories that may or may not operate in parallel.

Computing device110may all of the components normally used in connection with a computing device such as the processor and memory described above as well as a user input150(e.g., a mouse, keyboard, touch screen and/or microphone) and various electronic displays (e.g., a monitor having a screen or any other electrical device that is operable to display information). In this example, the vehicle includes an internal electronic display152as well as one or more speakers154to provide information or audio-visual experiences. In this regard, internal electronic display152may be located within a cabin of vehicle100and may be used by computing device110to provide information to passengers within the vehicle100. The vehicle may also include one or more wireless network connections156to facilitate communications with devices remote from the vehicle and/or between various systems of the vehicle.

In one example, computing device110may be an autonomous driving computing system incorporated into vehicle100. The autonomous driving computing system may be capable of communicating with various components and systems of the vehicle, for instance, wirelessly (via wireless network connections156) and/or a wired connection (such as a controller area network bus or other communication bus). For example, returning toFIG.1, computing device110may be in communication with various systems of vehicle100, such as deceleration system160(for controlling braking of the vehicle), acceleration system162(for controlling acceleration of the vehicle), steering system164(for controlling the orientation of the wheels and direction of the vehicle), signaling system166(for controlling turn signals), navigation system168(for navigating the vehicle to a location or around objects), positioning system170(for determining the position of the vehicle), perception system172(for detecting objects in the vehicle's environment), and power system174(for example, a battery and/or gas or diesel powered engine) in order to control the movement, speed, etc. of vehicle100in accordance with the instructions132of memory130in an autonomous driving mode which does not require or need continuous or periodic input from a passenger of the vehicle. The vehicle100may also include a ultrasonic cleaning system400and a sensor status system460discussed further below.

Again, although these systems are shown as external to computing device110, in actuality, these systems may also be incorporated into computing device110, again as an autonomous driving computing system for controlling vehicle100. In addition or alternatively, each of these systems may include one or more computing devices having processors and memory, configured the same as or similarly to processors120and memory130of computing devices110in order to enable the functionalities of these systems as described here.

The computing device110may control the direction and speed of the vehicle by controlling various components. By way of example, computing device110may navigate the vehicle to a destination location completely autonomously using data from the map information and navigation system168. Computing devices110may use the positioning system170to determine the vehicle's location and perception system172to detect and respond to objects when needed to reach the location safely. In order to do so, computing devices110may cause the vehicle to accelerate (e.g., by increasing fuel or other energy provided to the engine by acceleration system162), decelerate (e.g., by decreasing the fuel supplied to the engine, changing gears, and/or by applying brakes by deceleration system160), change direction (e.g., by turning the front or rear wheels of vehicle100by steering system164), and signal such changes (e.g., by lighting turn signals of signaling system166). Thus, the acceleration system162and deceleration system160may be a part of a drivetrain that includes various components between an engine of the vehicle and the wheels of the vehicle. Again, by controlling these systems, computing devices110may also control the drivetrain of the vehicle in order to maneuver the vehicle autonomously.

As an example, computing device110may interact with deceleration system160and acceleration system162in order to control the speed of the vehicle. Similarly, steering system164may be used by computing device110in order to control the direction of vehicle100. For example, if vehicle100is configured for use on a road, such as a car or truck, the steering system may include components to control the angle of wheels to turn the vehicle. Signaling system166may be used by computing device110in order to signal the vehicle's intent to other drivers or vehicles, for example, by lighting turn signals or brake lights when needed.

Navigation system168may be used by computing device110in order to determine and follow a route to a location. In this regard, the navigation system168and/or data134may store map information, e.g., highly detailed maps that computing devices110can use to navigate or control the vehicle100. As an example, these maps may identify the shape and elevation of roadways, lane markers, intersections, crosswalks, speed limits, traffic signal lights, buildings, signs, real time or historical traffic information, vegetation, or other such objects and information. The lane markers may include features such as solid or broken double or single lane lines, solid or broken lane lines, reflectors, etc. A given lane may be associated with left and right lane lines or other lane markers that define the boundary of the lane. Thus, most lanes may be bounded by a left edge of one lane line and a right edge of another lane line. As noted above, the map information may store known traffic or congestion information and/or and transit schedules (train, bus, etc.) from a particular pickup location at similar times in the past. This information may even be updated in real time by information received by the computing devices110.

As an example, the detailed map information may include one or more roadgraphs or graph networks of information such as roads, lanes, intersections, and the connections between these features. Each feature may be stored as graph data and may be associated with information such as a geographic location and whether or not it is linked to other related features, for example, a stop sign may be linked to a road and an intersection, etc. In some examples, the associated data may include grid-based indices of a roadgraph to allow for efficient lookup of certain roadgraph features.

The perception system172also includes one or more components for detecting objects external to the vehicle such as other vehicles, obstacles in the roadway, traffic signals, signs, trees, etc. For example, the perception system172may include one or more LIDAR sensors, sonar devices, radar units, cameras and/or any other detection devices that record data which may be processed by computing devices110. The sensors of the perception system may detect objects and their characteristics such as location, orientation, size, shape, type (for instance, vehicle, pedestrian, bicyclist, etc.), heading, speed, acceleration, rate of change of acceleration, deceleration, rate of change of deceleration, etc. The raw data from the sensors and/or the aforementioned characteristics can be quantified or arranged into a descriptive function, vector, and or bounding box and sent for further processing to the computing devices110periodically and continuously as it is generated by the perception system172.

For instance,FIG.2is an example external view of vehicle100. In this example, roof-top housing210and housings212,214may include a LIDAR sensor as well as various cameras and radar units. In addition, housing220located at the front end of vehicle100and housings230,232on the driver's and passenger's sides of the vehicle may each store a LIDAR sensor. For example, housing230is located in front of driver door250. Vehicle100also includes housings240,242for radar units and/or cameras also located on the roof of vehicle100. Additional radar units and cameras may be located at the front and rear ends of vehicle100and/or on other positions along the roof or roof-top housing210. In addition, Vehicle100also includes many features of a typical passenger vehicle such as doors250,252, wheels260,262, etc.

Example Sensor

FIG.3depicts an example view of a sensor300. The sensor may be arranged or mounted at various locations on the vehicle, including, for example, a top portion of the vehicle such as with housing210or at various other locations, such as the sides, front or rear of the vehicle. The sensor300may be incorporated into the aforementioned perception system and/or may be configured to receive commands from the computing devices110, for instance via a wired or wireless connection.

The sensor300may include a housing310to protect the internal sensor components360(shown in dashed-line inFIG.3as they are internal to the housing310) from contaminants such as foreign object debris, including water, dirt, insects, and other contaminants. However, over time, the housing and other sensor components may collect contaminants. As such, the functions of internal sensor components360may be impeded as signals transmitted and received by the internal sensor components may be blocked by the contaminants. To address this, contaminants may be cleared from the sensor300by rotating the internal sensor components360within the housing. This rotation may enable one or more wipers to clear any contaminants on a sensor input surface of the sensor.

The housing310may be configured in various shapes and sizes. As shown in the example ofFIG.3, the housing310may be configured such that it has a domed shaped top portion317with a side wall305, such that the housing is in the shape of a frustum. Although the sensor housing is shown in the shape of a frustum, the sensor housing may be configured in various shapes and sizes, such as spheres, cylinders, cuboids, cones, prisms, pyramids, cubes, etc., or any combination of such shapes. The sensor housing310may be comprised of materials such as plastic, glass, polycarbonate, polystyrene, acrylic, polyester, etc. For instance, the housing may be a metal or plastic housing and the internal sensor components360have a “window” or sensor input surface350that allows the sensor to transmit and/or receive signals.

The sensor input surface may be arranged on or in the sensor housing such that the internal sensor components may transmit and receive one or more signals through the sensor input surface. For instance, the side wall305of the sensor housing310may include a flat portion326in which sensor input surface350is incorporated to allow signals (not shown) from internal sensor components360to penetrate the sensor cover315, as further shown inFIG.3. As an example, if the sensor housing is approximately 277 millimeters in diameter, the sensor input surface may be approximately 142 millimeters wide. Although the sensor input surface350is shown as being circular inFIG.3, various other shapes may also be used for the sensor input surface. In addition, the sensor input surface may be incorporated onto non-flat surfaces of the housing.

In some instances the entire sensor housing310, or a large portion of the sensor housing310, may be penetrable by the signals transmitted and received by the internal sensor components, thereby allowing a large portion or the entire sensor housing310to function as a sensor input surface. Although the sensor input surface350is shown as being only a portion of the side wall305, in some instances the entire side wall305may be constructed as a sensor input surface. Further, multiple sensor input surfaces may be positioned on the sensor housing310. The sensor input surface350may be composed of the same, or different, material as the sensor housing310.

The sensor300and/or sensor housing310may be attached to a motor via a sensor shaft. For instance, as further shown inFIG.3, the sensor shaft330may include a first end332and a second end334. The first end332of a sensor shaft330may be attached to a motor320and the second end of the sensor shaft330may be connected to the sensor300and/or sensor cover315, such as at the base portion306of the sensor cover. In this regard, the first end of the sensor shaft330may be attached to the motor320via a belt, gear, chain, friction roller, etc. The motor320may rotate the sensor shaft330in the first direction335causing the entire sensor300and/or sensor housing310to also rotate in the first direction335. In some embodiments the sensor shaft330may only rotate the sensor housing310, and not the internal sensor components360of the sensor.

As another alternative, the internal sensor components and the housing may be configured to rotate independently of one another. In this regard, all or a portion of the housing310may be transparent (or transparent at least in the wavelengths of the signals to be received by the internal sensor components) in order to enable signals to pass through the housing and to reach the internal sensor components360. In addition, to enable independent rotation, a first motor may be configured to rotate the housing310and a second motor may be configured to rotate the internal sensor components. In this example, the housing may be rotated to enable cleaning while the internal sensor components may still function to capture signals and generate sensor data.

The sensor300, sensor housing310, and/or motor320may each be located internally or externally from a vehicle. AlthoughFIG.3shows the sensor300being attached to the motor320via a shaft330, the motor320may be integrated or otherwise directly connected to the sensor300and/or sensor housing310.

The internal sensor components360may transmit and receive one or more signals through the sensor input surface. In this regard, the internal sensor components may include one or more imaging sensors such as LIDAR, radar, sonar, camera, or other such imaging sensors positioned within the housing of the sensor. The sensor input surface may be a lens, mirror or other surface by which the signals can pass or are directed to other sensor components (e.g. a photodetector in the case of a camera) in order to generate sensor data.

Example Cleaning System

Turning toFIG.4, an ultrasonic cleaning system400may be configured to provide both cleaning (e.g. removal of contaminants) and clearing (e.g. removal of liquid) functions. For instance, cleaning may refer to detaching contaminants from the sensor input surface which are chemically attached by causing cavitation through liquid over the sensor input surface. When an organic contaminant hits the sensor input surface, compounds may chemically bond to the surface making such compounds difficult to remove. With the ultrasonic cleaning system400, liquid cleaning fluid may be added to the sensor input surface and ultrasonic waves may move the glass. This may occur with such speed that fluids, such as liquid cleaning fluid, may cavitate, resulting in a “cold boil” or a boiling caused by low pressure as opposed to high heat. This boiling action may actually result in a cleaning function or effect as vapor bubbles created by the cold boil collapse with great force “chipping” the contaminates from the sensor input surface. This action can be maximized by actively creating standing waves over the sensor input surface. The clearing function may refer to propelling droplets of precipitation which are not chemically bonded to the sensor input surface. This action can be maximized by actively creating traveling waves or increasing the number of traveling waves generated as compared to standing waves. Thus, by controlling a ratio of standing to traveling waves, the ultrasonic cleaning system can provide both cleaning and clearing functions, and thereby achieving a clear or nearly clear sensor input surface with little to no contaminants.

The ultrasonic cleaning system may include a liquid nozzle410. In some instances, the ultrasonic cleaning system may also include an air nozzle420. The liquid nozzle410may be connected to a reservoir412storing liquid cleaning fluid, including water, alcohol, or various other liquid cleaning fluids. Although depicted and described as a single nozzle, liquid nozzle410may actually represent two or more smaller nozzles directly adjacent to one another in order to provide a more directed stream of liquid cleaning fluid. A liquid pump414may be configured to pump liquid cleaning fluid from the reservoir through a liquid valve418, tubing416, and out of the liquid nozzle410in order to clean the sensor input surface. The tubing may be formed from any suitable materials such as plastic, silicone, metal, etc.

The liquid nozzle may be arranged at different locations around the sensor300.FIGS.5-7represent top-down views of the sensor300and depict direction of airflow and turbulence cause when vehicle100is moving in the forward direction (depicted inFIG.2) and the housing of the sensor is rotating in a clockwise direction. For instance, if optimizing for reducing the effects of the liquid cleaning fluid on the detection of objects in the forward-direction, the liquid nozzle410and air nozzle420may be arranged as depicted inFIG.5to maximize cleaning as the sensor input surface sweeps through the area depicted by arrow510during rotation. By positioning the liquid and air nozzles towards the rear of the vehicle (rather than the front), any liquid which is sprayed at the sensor housing and “misses” the sensor input surface350is located behind the vehicle, and therefore much less likely to be blown onto another sensor housing or some other portion of the vehicle. Moreover, this reduces the impact of the cleaning on the sensor data captured for the front of the vehicle where detecting objects may be most critical (e.g. emergency and other vehicles and other road users with which the vehicle could potentially collide are more likely to be located in front of the vehicle than behind). As another instance, if optimizing to reduce the effects of moving air and thereby reduce the power requirements for the liquid nozzle410, for instance caused (or necessitated) by the forward motion of the vehicle as represented by the depiction inFIG.6, on the spray of liquid cleaning fluid, the liquid nozzle410may be location in area710ofFIG.7.

In all arrangements of the liquid nozzle, the rotation of the sensor housing may help to clear the liquid cleaning fluid from the sensor input surface. However, the rotation may not be enough to ensure that the liquid cleaning fluid is removed as quickly as possible from the sensor input surface. As such, the air nozzle420may generate a puff of fluid, such as air or another gas, in order to force the liquid cleaning fluid off of the sensor input surface. In addition, the timing of a puff of gas from the air nozzle420may be determined by the controller440based on the type of contamination (if known). For instance, if the type of contaminant requires the liquid cleaning fluid to soak for some period of time and ultrasonic cleaning system400(really, the transducers452) to run longer, a puff of gas may be delayed by some number of rotations of the sensor housing. In addition, if the contaminant on the sensor is merely fine water droplets (e.g. mist), only a puff of gas may be needed (and used) to clear the sensor input surface.

An air pump422may be configured to pump air through an air valve428and tubing426, and out of the air nozzle in order to clean the sensor input surface. The tubing may be formed from any suitable materials such as plastic, silicone, metal, etc. While the exact locations may not be critical to cleaning, as noted below, the nozzles should be located at least half the maximum width of the spray from the nozzles or more or less apart. Using the example of a sensor housing that is approximately 277 millimeters in diameter and a sensor window that is approximately 142 millimeters wide, the angular distance between the nozzles relative to the sensor housing may be at least 80 degrees or more or less as shown inFIG.5.

In addition, the liquid and air nozzles may be arranged at different angles relative to the sensor housing. For instance, as shown inFIG.8, the liquid nozzle410may be arranged at 90 degrees relative to the sensor housing. Although multiple liquid nozzles are depicted inFIG.8, this merely demonstrates that one or more liquid nozzles can be located at any point around the sensor300. Alternatively, as shown inFIG.9, the liquid nozzle may be offset from the sensor housing at an angle Θ (in the direction of rotation). This angle may range between 60 and 90 degrees or more or less and may increase the effectiveness of a spray of liquid cleaning fluid. Similar configurations may be used for the air nozzle420in order to increase the effectiveness of a puff of gas.

A position sensor430may be arranged to detect the current angular position of the sensor and/or sensor housing relative to the vehicle. The position sensor may include any rotational position sensor, such as a Hall effect array or an encoder, that can be used to track the position of the motor320, housing310, and/or the internal sensor components360. In this regard, one or more processors, such as the one or more processors120or other similarly configured processors, may control the motor320based on feedback from the position sensor or another position sensor. In this regard, the position sensor may be configured to generate a signal indicating or identifying a location of one or more of the motor, housing, or the internal sensor components. The position sensor may be located at forward direction or position with respect to the vehicle (e.g. approximately 0 degrees), such that the position sensor detects each time a center of the sensor input surface rotates passes the position sensor.

Controllers440,450may include one or more computing devices having one or more processors and memory, configured the same or similarly to the computing devices110, processors120, and memory130. The controllers may be configured to receive, and act upon, various signals. For example, the controllers440,450may be configured to receive feedback from the position sensor indicating the position of the sensor. From this information as well as the rotation speed of the sensor housing (for example, 10 Hz or more or less), the controllers may determine the current position, for example the current angular position, of the sensor input surface350at any given point in time.

The controllers440,450may also receive signals from the sensor300and/or other computing devices of the vehicle indicating the current state of the sensor. For example, the controllers440,450may receive signals indicating that the sensor input surface350is occluded or dirty. This information may be generated by another system, for example a sensor status system460, configured to determine whether the sensor input surface350is dirty. As discussed further below, the sensor status system460may receive signals from the transducers452and use this information to determine whether there are any contaminants on the sensor input surface as discussed further below. In addition or alternatively, this system may capture images of the sensor input surface350and processes these images to determine whether there is any contaminants such as foreign object debris located on the sensor input surface350and if so, approximately where.

In response, the controller440may use the current position of the sensor input surface350to determine exactly when to activate the liquid pump414and the air pump422as well as to open the air and liquid valves in order to both apply liquid cleaning fluid to the sensor input surface as well as to clear the cleaning fluid from the sensor input surface350using a puff of gas. For example, by knowing the location of any given point on the sensor, the controller440may determine the relative position of the forward facing and rearward facing edges (relative to the direction of rotation) of the sensor input surface. In this regard, the controller is able to determine the exact location of the edges of the sensor input surface. Although controllers440,450are depicted and described herein as distinct controllers, a single controller could be used to drive both the nozzles and the transducers.

FIG.10represents side perspective views of the sensor300with different possible configurations for the transducers452arranged on the sensor input surface350. Each configuration may be associated with different benefits and/or drawbacks and may be selected based upon where (e.g. geographically) a particular sensor is being used or for which function (cleaning or clearing) the ultrasonic cleaning system400is to be optimized. For instance, pairs of transducers may be better able to generate traveling waves and thus may do a better job of creating a local pressure difference at different locations on the sensor input surface, thereby providing a better clearing function. In this regard, a single transducer (i.e. one of a plurality of transducers or only a single transducer), may be used to generate more standing waves as compared to traveling waves when attempting to provide a cleaning function. In addition, more than one transducer can be used for the cleaning and clearing functions using different activation timing.

The exact frequencies of the transducers used may be dependent upon the configuration and characteristics of the sensor input surface. For instance, the sensor input surface may be formed from glass, sapphire, plastics or other rigid materials. Some materials, such as glass, may work with many ranges of frequencies depending upon the acoustic properties of the material including the longitudinal wave speed and shear wave speed. This combination of wave speeds will provide a different in and out of plane motion over the glass surface.

Configuration1010includes 3 transducers arranged in around the sensor input surface. As compared to the other configurations, there are fewer transducers which reduces the number of channels. However, because the transducers are not paired, detection and identification of contaminants may be more complex than with the other configurations detected inFIG.10. In other words, detection and identification of contaminants may be better optimized when the transducers are arranged in pairs. In this regard, the configuration1010may require more complicated electronics to increase the width of the frequency bands of the transducers.

Configuration1020includes two pairs of transducers. This configuration may provide the flexibility of 4 channels as well as improved detection and identification of contaminants between paired transducers (paired across the sensor input surface rather than by adjacent transducers). This configuration also provides more efficient cleaning as compared to configuration1010as it may enable more actively controlled standing waves. In addition, the concave shape of the transducers of configuration1020, especially when paired with a second transducer, may result in wave patterns that increase the cleaning strength of a specific local area between the paired transducers.

Configuration1030also includes two pairs of transducers. This configuration may provide the flexibility of 4 channels as well as improved detection and identification of contaminants between paired transducers (paired across the sensor input surface rather than by adjacent transducers). This configuration also provides more efficient cleaning as compared to configuration1010as it may enable more actively controlled standing waves. Although both configurations may have similar functionality, the less-curved shape of the transducers of configuration1030may provide more coverage of the sensor input surface than the more-curved shape of the transducers of configuration1020. In this regard, using a pair of flat transducers (i.e. not concave or convex), may result in wave patterns that may provide a more uniform cleaning strength across the area between the transducers.

Configuration1040also includes two pairs of transducers. This configuration may provide the flexibility of 4 channels as well as improved detection and identification of contaminants between paired transducers (paired across the sensor input surface rather than by adjacent transducers). This configuration also provides more efficient cleaning as compared to configuration1010as it may enable more actively controlled standing waves. However, this configuration combines lower and higher frequency transducers. The lower frequency transducers which produce longer wavelengths being represented by the thicker shapes, and the higher frequency transducers which produce shorter wavelengths being represented by the thinner shapes. In this regard, each higher frequency transducer is paired with a lower frequency transducer. This combination may allow for improved clearing functions over configurations1010,1020,1030by also improving the ability of the transducers to generate traveling waves. For instance, certain frequencies of standing waves may be more effective at cleaning certain types and sizes of contaminants. So, multiple transducers which can operate to create waves of different frequencies may provide the ability to mix multiple frequencies and wavelengths which may potentially enable the ultrasonic cleaning system400to clean a greater number of different types and sizes of contaminants. The actual frequencies used may be verified by real world testing and simulations. In addition because the higher frequency transducers are arranged towards the bottom of the sensor input surface, this configuration may provide for better collection of smaller droplets into larger droplets which can be readily cleared by the lower frequency waves from the lower frequency transducers. In this regard, this configuration may provide better cleaning function than configurations1010,1020,1030.

Configuration1050also includes two pairs of transducers. This configuration may provide the flexibility of 4 channels as well as improved detection and identification of contaminants between paired transducers (paired across the sensor input surface rather than by adjacent transducers). This configuration also provides more efficient cleaning as compared to configuration1010as it may enable more actively controlled standing waves. However, this configuration combines lower and higher frequency transducers. The lower frequency transducers which produce longer wavelengths being represented by the thicker shapes, and the higher frequency transducers which produce shorter wavelengths being represented by the thinner shapes. In this regard, each higher frequency transducer is paired with another higher frequency transducer, and each lower frequency transducer is paired with another lower frequency transducer. This combination may allow for improved cleaning and clearing function over configurations1010,1020,1030for the reasons discussed above with regard to configuration1040(e.g. by improving the ability of the transducers to generate traveling waves and by enabling the generation of standing waves with two different wavelengths).

Configuration1060also includes two pairs of transducers. This configuration may provide the flexibility of 4 channels as well as improved detection and identification of contaminants between paired transducers (paired across the sensor input surface rather than by adjacent transducers). This configuration also provides more efficient cleaning as compared to configuration1010as it may enable more actively controlled standing waves. Although both configurations may have similar functionality, the convex shape of the transducers of configuration1060may provide more coverage of the sensor input surface than the concave shape of the transducers of configurations1010,1020,1030,1040,1050. This may also result in poorer performance for the cleaning function as compared to configurations1020and1030as it may be more difficult to produce standing waves and result in less power.

In order to improve the effectiveness of the cleaning, the contact angle of droplets hitting the sensor input surface can be manipulated. For instance, as depicted inFIG.11, a higher contact angle (e.g. greater than 90 degrees) may make it easier for droplets to run off of the sensor input surface, but may also make it more difficult to impart energy to the liquid cleaning fluid. In this regard, a lower contact angle (e.g. less than 90 degrees) may be preferable for the cleaning function, whereas a higher contact angle is preferable for the clearing function. A higher contact angle may be achieved by coatings, and specifically nano structures that are more hydrophobic coatings will keep drops from wetting (or spreading out) which may help with cleaning. At the same time, coatings that are more hydrophilic will result in a lower contact angle and cause wetting (or spreading out) which may help with clearing. However, once organic contaminants contact the sensor input surface, this may tend to reduce the contact angle and therefore aid in the cleaning function. In this regard, hydrophilic surfaces (and hydrophilic coatings on the sensor input surface) may be preferred over hydrophobic surfaces (and hydrophobic coatings on the sensor input surface) when both cleaning and clearing functions are desired.

Example Methods

FIG.12is an example flow diagram for cleaning a sensor having a rotating sensor housing including a sensor input surface which may be performed by one or more processors of a controller such as the processors of controllers440,450. At block1210, a first signal is received by one or more processors indicating that there is a contaminant on the sensor input surface. This first signal may be received from the sensor status system460based on any number of different inputs. As one example, if the sensor data generated by the sensor300becomes degraded, this may indicate that there is a contaminant on the sensor input surface350. In addition or alternatively, images from a camera arranged to capture images of the sensor input surface may be processed to determine that there is a contaminant on the sensor input surface350. In addition or alternatively, feedback from the transducers452may be processed to determine that there is a contaminant on the sensor input surface.

For instance, a very small signal, on the order of 1 mW can be used to measure impedance of the surface of the sensor input surface. The multi-channel configurations ofFIG.10may be used to detect approximately where the contaminant is located. For example, turning toFIG.13, transducer A may send a signal which, if the sensor input surface were clear, received by its paired transducer, transducer D. The sensor input surface would cause a certain amount of impedance on the signal received at transducer D. However, the contaminants1310may cause some of the signal to be reflected back to the transducer A, and may impede the signal, causing none or some of the signal to reach transducer D. Thus, the impedance, including the mode frequency, value of impedance, and the ratio or resistance and reactance would change. This change in the impedance may be used to determine that there is a contaminant in the sensor input surface. A similar effect may occur with each of the transducers B, C, D where a signal sent to a paired transducer may be reflected by the contaminant1310back to that respective transducer and/or impeded by the contaminant. In addition, the timing of the reflected signals received at transducers A, B, C, D may be used to determine the distribution (e.g. shape and location) of the contaminant1310.

In addition, impedance may also change with the type of the contamination. In this regard, statistical analysis and/or machine learning utilizing data generated by testing different types of contaminants may be used to categorize different types of contaminants based on expected changes in impedance values. This information may be used by the ultrasonic cleaning system400to estimate how much liquid cleaning fluid and power is needed to clean and clear the sensor input surface.

In this regard, based upon signals received from the transducers452, not only may the sensor status system460determine that the sensor input surface includes a contaminant, but also the location of the contaminant as well as possibly the type of contaminant. The sensor status system460may then send the aforementioned signal indicating that the sensor input surface has a contaminant to the processors120of the computing devices110.

Returning toFIG.12, at block1220, in response to receiving the first signal, a second signal is sent to cause a transducer to generate waves in order to attempt to remove the contaminant from the sensor input surface. In this regard, the ultrasonic cleaning system400may activate the ultrasonic cleaning and/or clearing functions of the transducers. For instance, the computing devices110may send a signal to the controller450in order to cause the controller to activate the transducers452. For example, if the contaminant is determined to be water, the controller may activate the transducers in order to generate traveling waves according to the clearing function (or decrease the ratio of standing waves to traveling waves). In this regard, individual transducers may be activated at different times in order to generate more traveling waves. In this regard, the controller450may attempt to minimize the ratio of standing waves to traveling waves to perform the clearing function.

As another example, if the contaminant is determined to be other than water (or a combination of water and other contaminants), the controller450may activate the transducers to generate standing waves (or increase the ratio of standing waves to traveling waves). In this regard, pairs of transducers may be activated together in order to generate more standing waves. In this regard, the controller may attempt to maximize the ratio of standing waves to traveling waves to perform a cleaning function.

In addition, the computing devices110may send a signal to the controller440in order to cause the controller to activate liquid nozzle and air nozzle (if used). For instance, the controller440may use the information about the location and type of contaminant to choose appropriate cleaning cycles. As noted above, the liquid nozzle may be configured to provide a spray of liquid, and the air nozzle being configured to provide a puff of gas. For instance, the controller440may receive a signal from computing devices110indicating that the sensor input surface350requires cleaning. As noted above, the liquid nozzle410may provide a spray of liquid cleaning fluid to attempt to clean contaminants from the sensor input surface350, and the air nozzle420may provide a puff of gas to remove liquid cleaning fluid and/or contaminants from the sensor input surface.

When to activate the liquid nozzle in order to provide the spray of liquid on the sensor input surface is determined based on the current position of the sensor. For example, the timing of the activation of the liquid pump414and the opening of the liquid valve418may be determined in order that the spray of liquid cleaning fluid from the liquid nozzle410is made as the sensor input surface350rotates passed the liquid nozzle in order to cause the liquid cleaning fluid to contact the sensor input surface without wasting the liquid cleaning fluid (i.e. rather than spraying on other portions of the sensor housing than the sensor input surface).

The timing of the activation of the air pump422and the opening of the air valve428may be determined in order that the puff of gas from the air nozzle420is made as the sensor input surface350rotates passed the air nozzle in order to cause the puff of gas to contact the sensor input surface (i.e. rather than puffing on other portions of the sensor housing than the sensor input surface).

The liquid nozzle may then be activated based on the determination of when to activate the liquid nozzle. In addition, the air nozzle may be based on the determination of when to activate the air nozzle. For example, the liquid valve418, air valve428, liquid pump414, and air pump422may be activated in order to cause a spray of liquid cleaning fluid to contact the sensor input surface350as the sensor input surface rotates passed the liquid nozzle410and to cause a puff of gas to contact the sensor input surface as the sensor input surface rotates passed the air nozzle420.

In addition, once the liquid nozzle410has generated the spray of liquid cleaning fluid, the controller450may activate the transducers in order to generate traveling waves according to the clearing function (or decrease the ratio of standing waves to traveling waves). In this regard, individual transducers may be activated at different times in order to generate more traveling waves or otherwise in order to minimize the ratio of standing waves to traveling waves to perform the clearing function. This, in conjunction with the rotation of the sensor housing as well as the puff of gas generated by the air nozzle (if used), may cause the liquid cleaning solution, contaminants and other fluids to be removed from the sensor input surface350. As a result, the sensor input surface350may return to optimal (clean) or near optimal performance.

This cleaning and clearing may be repeated as needed to reduce or keep the sensor input surface clear of contaminants. However, in some instances, if the sensor input surface is not clean for a predetermined amount of time, this may be used to change the behavior of other systems of the vehicle. For instance, the perception system172may degrade the fidelity of the data feed from that specific sensor (e.g. reduce a confidence value, etc.).

Alternatively, if the functions of controllers440and450are implemented in a single controller, a single signal from the computing devices110may cause that controller to both activate the transducers420as well as the liquid nozzle410and air nozzle420(if used) as in the examples described above.

As noted above, if the contaminant is identified as water, only the ultrasonic clearing function of the transducers may need to be utilized to clear the sensor input surface. In other words, the ultrasonic cleaning system400may minimize the ratio of standing waves to traveling waves to perform the clearing function when the contaminant is water. In such instances, a spray of liquid cleaning fluid from the liquid nozzle410may not be needed or used. As such, the liquid cleaning fluid can be preserved for use with contaminants other than water and therefore last longer. However, if used, the puff of air may still be used in order to increase the clearing function capabilities of the ultrasonic cleaning system400.

The features described herein may provide for a useful and practical approach to cleaning rotating sensors. The combination of cleaning and clearing functionality of the ultrasonic cleaning features described herein may provide significant improvements over other systems without such features. Moreover, the use of ultrasonic cleaning may also reduce the amount of liquid cleaning solution needed to remove contaminants from a sensor input surface. In addition, the use of the impedance information to detect contaminants may obviate the need for additional devices, (e.g., a camera) to serve the same purpose and thereby save power and other resources on the vehicle. Other benefits may include potentially, better reliability of the ultrasonic cleaning system (due to fewer mechanical parts), lower cost (once having more integrated design and mass produced), smaller (as the transducers can be miniature), as well as a simplified construction with fewer maintenance requirements than other cleaning and clearing approaches with more hardware and more potential points of failure.