Patent Publication Number: US-2023159004-A1

Title: Electronic device to detect contamination, melt ice and remove water

Description:
INTRODUCTION 
     The subject disclosure relates to a Lidar system or camera system used in a vehicle and, in particular, to a system and method for cleaning a window of the Lidar/camera system. 
     Autonomous vehicles use various detection systems for determining the location of objects in its environment. An exemplary system is a Lidar (Light Detection and Ranging) system, in which a laser beam is transmitted into the environment and a reflection of the laser beam off of objects in the environment is received and recorded. The Lidar system generally is housed in a protective housing having an optical element such as a transparent window through which the laser beam and its reflection can pass. This window can accumulate water or fluid on it under certain conditions, such as during rainy weather. The accumulation of fluid can affect the laser beam and therefore impair the accuracy of the Lidar system. When the vehicle is travelling at high speeds, this impairment can affect the performance of the vehicle. Accordingly, it is desirable to provide a system and method for cleaning the fluid from the window as quickly as possible. 
     SUMMARY 
     In one exemplary embodiment, a method of moving a fluid along a window is disclosed. A first electrode disposed on a first side of the window is activated to draw the fluid to a first location on a second side of the window opposite the first electrode. The first electrode is deactivated, and a second electrode disposed on the first side of the window is activated to draw the fluid to a second location on the second side of the window opposite the second electrode. 
     In addition to one or more of the features described herein, the first electrode and the second electrode are disposed in a first electrode layer located at a first distance from the first side. A third electrode and a fourth electrode disposed in a second electrode layer located at a second distance from the first side of the window. The method further includes performing an electrode activation sequence that activates the first electrode, the second electrode, the third electrode and the fourth electrode in sequence to move the fluid at the first location opposite the first electrode to a destination location opposite the fourth electrode. The method further includes repeating the activation sequence when the fluid is at the destination location to draw the fluid away from the destination location. The first electrode and the second electrode can be are arranged in a line along a selected direction or can form a spiral. The method further includes performing at least one of measuring an impedance when at least the first electrode is activated to determine the presence of ice and activating at least the first electrode to melt the ice. 
     In another exemplary embodiment, a window of a Lidar system is disclosed. The window includes a first electrode disposed on a first side of an outermost layer of the window, a second electrode disposed on the first side of the outermost layer, and a processor. The processor is configured to activate the first electrode to draw a fluid to a first location on a second side of the outermost layer opposite the first electrode, deactivate the first electrode, and activate the second electrode to draw the fluid to a second location on the second side of the outermost layer opposite the second electrode. 
     In addition to one or more of the features described herein, the first electrode and the second electrode are disposed in a first electrode layer located at a first distance from the first side. The window further includes a third electrode and a fourth electrode disposed in a second electrode layer located at a second distance from the first side of the outermost layer. The processor is further configured to run an electrode activation sequence that activates the first electrode, the second electrode, the third electrode and the fourth electrode in sequence to move the fluid at the first location opposite the first electrode to a destination location opposite the fourth electrode. The processor is configured to repeat the activation sequence to draw the fluid away from the destination location. The first electrode and the second electrode can be are arranged in a line along a selected direction or can form a spiral. The processor is further configured to perform at least one of measuring an impedance when at least the first electrode is activated to detect the presence of ice and activating at least the first electrode to melt the ice. 
     In another exemplary embodiment, a Lidar system is disclosed. The Lidar system includes a window including a glass layer having a first side and a second side opposite the first side, a first electrode disposed on the first side of the glass layer, a second electrode disposed on the first side of the glass layer, and a processor. The processor is configured to activate the first electrode to draw a fluid to a first location on the second side of the glass layer opposite the first electrode, deactivate the first electrode, and activate the second electrode to draw the fluid to a second location on the second side of the outermost layer opposite the second electrode. 
     In addition to one or more of the features described herein, the first electrode and the second electrode are disposed in a first electrode layer located at a first distance from the first side, further comprising a third electrode and a fourth electrode disposed in a second electrode layer located at a second distance from the first side. The processor is further configured to run an activation sequence that activates the first electrode, the second electrode, the third electrode and the fourth electrode in sequence to move the fluid at the first location opposite the first electrode to a destination location opposite the fourth electrode. The processor is configured to repeat the activation sequence to draw the fluid away from the destination location. The first electrode and the second electrode can be are arranged in a line along a selected direction or can form a spiral. The processor is further configured to perform at least one of measuring an impedance when at least the first electrode is activated to detect the presence of ice and activating at least the first electrode to melt the ice. 
     The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which: 
         FIG.  1    shows a vehicle having a Lidar system, in an exemplary embodiment; 
         FIG.  2    shows a side cross-sectional view of the window of the Lidar system, in an embodiment; 
         FIG.  3    shows a top view of a first electrode pair of the window; 
         FIG.  4    shows a top view of the second electrode pair of the window; 
         FIG.  5    shows a top view of the conductors of  FIGS.  3  and  4    as arranged in the window of the Lidar system, in an illustrative embodiment; 
         FIG.  6    shows an alternative arrangement of the conductors disposed in the window; 
         FIG.  7    shows an activation sequence for the voltage sources shown in  FIGS.  5  and  6   , in an illustrative embodiment; 
         FIG.  8    shows an alternative arrangement of the electrodes within the window; 
         FIG.  9    (Prior Art) shows a graph of frequency-related resistivity values for different accumulation conditions of the window; and 
         FIG.  10    shows a graph illustrating a melting rate of ice using the de-icing methods disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
     In accordance with an exemplary embodiment,  FIG.  1    shows a vehicle  100  having a Lidar system  102 . The Lidar system  102  includes a housing  104  and a window  106 . A laser (not shown) is disposed in the housing  104  and the window  106  allows the laser beam to pass through. In various embodiments, the window  106  is oriented at a non-zero angle with respect to a horizontal direction. The window  106  can be oriented vertically or can have a direction along its outer surface having a vertical component, such that a fluid or water runs off of the outer surface along a substantially vertical direction. The window  106  includes circuitry therein, as disclosed herein, suitable for cleaning fluids, such as rain, from its outer surface. The vehicle  100  further includes a processor  108  that operates the Lidar system  102  as well as the circuitry for cleaning fluids from the window  106 . 
       FIG.  2    shows a side cross-sectional view  200  of the window  106  of the Lidar system  102 , in an embodiment. The window  106  has been rotated from its orientation in  FIG.  1    for ease of explanation. The window  106  includes an innermost glass  202  or innermost layer, generally made of a transparent or semi-transparent glass through which a laser beam can be transmitted. A first electrode layer  204  and a second electrode layer  206  are placed on top of (i.e., on the outer surface of) the innermost glass  202 . The first electrode layer  204  is disposed directly on top of the innermost glass  202  and the second electrode layer  206  is disposed on top of the first electrode layer  204 , such that the first electrode layer  204  is between the innermost glass  202  and the second electrode layer  206 . A first dielectric layer  208  is disposed between the first electrode layer  204  and the second electrode layer  206  and a second dielectric layer  210  is disposed on top of the second electrode layer  206 . An outermost layer  212  can be disposed on top of the second dielectric layer  210 . The outermost layer  212  can be glass or other suitable material. The outermost layer  212  is exposed to contamination from the outside environment such as dirt, rain, etc. In various embodiments, the outermost layer  212  is made of hydrophobic glass material. 
     The first electrode layer  204  includes a first electrode E 1  and a second electrode E 2 . The first electrode E 1  and the second electrode E 2  form a first electrode pair P 1 . The second electrode layer  206  includes a third electrode E 3  and a fourth electrode E 4 . The third electrode E 3  and the fourth electrode E 4  form a second electrode pair P 2 . The first electrode pair P 1  and the second electrode pair P 2  form a first electrode group EG 1 . The first electrode, second electrode, third electrode and fourth electrode are aligned in a row along a selected direction  214  in the order shown (i.e., E 1 , E 2 , E 3 , E 4 ). In various embodiments, the window  106  includes a plurality of electrode groups (EG 1 , EG 2 , . . . ) aligned in the selected direction  214 . The selected direction  214  can be in a vertical direction along the window  106 , oriented toward a bottom edge of the window. However, this is not meant to be a limitation of the invention. 
     The outermost layer  212  includes a first surface (bottom surface  230 ) and a second surface (top surface  232 ) opposite the first surface. The top surface  232  is exposed to the elements. Outermost layer  212  is coated onto the second dielectric layer  210 . The second dielectric layer  210  covers both the first electrode pair P 1  and the second electrode pair P 2 . Due to the presence of the first dielectric layer  208  and the second dielectric layer  210 , the first pair P 1  is separated from a bottom surface  230  by a first distance and the second pair P 2  is separated from the bottom surface  230  by a second distance. 
     In an embodiment, the electrodes are activated in a selected activation sequence progressing along the selected direction  214 . Activating an electrode refers to applying a non-zero voltage to the electrode. An activation sequence is applied in which one electrode (e.g., E 1 ) is held at a high voltage while the remaining electrodes (e.g., E 2 , E 3 , E 4 ) are held at low voltages or grounded at zero volts. When an electrode is activated or set to a high voltage, a rain droplet or fluid droplet on the top surface  232  of the outermost layer  212  is drawn to a location of the outermost layer  212  that is opposite the activated electrode. By activating the electrodes in order (i.e., E 1  first, E 2  second, E 3  third and E 4  fourth), the droplet can be moved along the surface and eventually off to a side of the window  106 . 
     In an embodiment, the first electrode E 1  is activated to draw the droplet to a first location  220  opposite the first electrode E 1 . The first electrode E 1  is then deactivated or set to low voltage (i.e., set to ground) and the second electrode E 2  is activated to draw the droplet from the first location  220  to a second location  222  opposite the second electrode E 2 . Continuing this process, the second electrode E 2  is deactivated and the third electrode E 3  is activated to draw the droplet from the second location  222  to a third location  224  opposite the third electrode E 3 . Finally, the third electrode E 3  is deactivated and the fourth electrode E 4  is activated to move the droplet from the third location  224  to a fourth location  226  opposite the fourth electrode E 4 . The fourth location  226  is a destination location for the droplet within the first electrode group EG 1 . When the droplet is at the fourth location, repeating the activation sequence (i.e., activating first electrode E 1 ) activates the first electrode E 1 ′ of the adjacent electrode group EG 2 , thereby drawing the droplet from the fourth location  226  to a fifth location  228  opposite the electrode E 1 ′. The droplet can thus be passed between electrodes groups and moved along the surface until a last electrode or edge of the window  106  is reached, thereby moving the droplet off to a side of the window  106 . 
       FIG.  3    shows a top view  300  of the first electrode pair P 1  of the window  106 . The top view  300  is a view looking into the window  106  from outside the vehicle  100  (i.e., with the outermost layer  212  closest to the viewer). The top view  300  shows a first conductor  302  and a second conductor  304 . The first conductor  302  includes strips that branch off of a first conductive backbone  306 . The strips form the first electrodes (E 1 , E 1 ′, E 1 ″, . . . ) within their respective electrode groups (EG 1 , EG 2 , EG 3 , . . . ). The first conductor  302  is coupled to a first voltage source  312 . Activation of the first voltage source  312  raises each of the first electrodes (E 1 , E 1 ′, E 1 ″, . . . ) to a selected voltage value. The second conductor  304  includes strips that branch off of a second conductive backbone  308 . The strips form the second electrodes (E 2 , E 2 ′, E 2 ″, . . . ) within their respective electrode groups (EG 1 , EG 2 , EG 3 , . . . ). The second conductor  304  is coupled to a second voltage source  314 . Activation of the second voltage source  314  raises each of the second electrodes (E 2 , E 2 ′, E 2 ″, . . . ) to selected voltage value. 
       FIG.  4    shows a top view  400  of the second electrode pair P 2  of the window  106 . The top view  400  shows a third conductor  402  and a fourth conductor  404 . The third conductor  402  includes strips that branch off of a third conductive backbone  406 . The strips form the third electrodes (E 3 , E 3 ′, E 3 ″, . . . ) within their respective electrode groups (EG 1 , EG 2 , EG 3 , . . . ). The third conductor  402  is coupled a third voltage source  412 . Activation of the third voltage source  412  raises each of the third electrodes (E 3 , E 3 ′, E 3 ″, . . . ) to selected voltage value. The fourth conductor  404  includes strips that branch off of a fourth conductive backbone  408 . The strips form the fourth electrodes (E 4 , E 4 ′, E 4 ″, . . . ) within their respective electrode groups (EG 1 , EG 2 , EG 3 , . . . ). The fourth conductor  404  is coupled to a fourth voltage source  414 . Activation of the fourth voltage source  414  raises each of the fourth electrodes (E 4 , E 4 ′, E 4 ″, . . . ) to selected voltage value. 
       FIG.  5    shows a top view  500  of the conductors of  FIGS.  3  and  4    as arranged in the window  106  of the Lidar system  102 , in an illustrative embodiment. As shown in  FIG.  5   , the conductors are arranged such that their respective electrodes form a repeating pattern. The first electrode group EG 1  includes, in order, electrodes (E 1 , E 2 , E 3 , E 4 ). The second electrode group EG 2  is adjacent the first electrode group EG 1  and includes, in order, electrodes (E 1 ′, E 2 ′, E 3 ′, E 4 ′). The third electrode group EG 3  is adjacent the second electrode group EG 2  and includes, in order, electrodes (E 1 “, E 2 ”, E 3 ″, E 4 ″). The electrode groups are aligned in the same direction as their electrodes along the selected direction  214 . 
     In the arrangement shown in  FIG.  5   , the first conductor  302  and the second conductor  304  are planar elements and are placed side by side within the first electrode layer  204 . Similarly, the third conductor  402  and the fourth conductor  404  are planar elements and are placed side by side within the second electrode layer  206 . 
       FIG.  6    shows an alternative arrangement  600  of the conductors disposed in the window  106 . The alternative arrangement allows the electrodes to lie within a single electrode layer. Referring to the first electrode group EG 1  for illustrative purposes, the electrodes (E 1 , E 2 , E 3 , E 4 ) form the first electrode group EG 1  and lie entirely within the single electrode layer. The third conductor  402  includes a jump section  602  that extends out of the electrode layer in order to prevent electrical contact with the first conductor  302  and second conductor  304 . Similarly, the fourth conductor  404  includes a jump section  604  that extends out of the electrode layer in order to prevent electrical contact with the first conductor  302  and second conductor  304 . 
       FIG.  7    shows an activation sequence for the voltage sources shown in  FIGS.  5  and  6   , in an illustrative embodiment. Time is shown along the abscissa in seconds (s) and pulse amplitude is shown along the ordinate axis in Volts (V). The first voltage source  312  is activated to raise the first electrodes (E 1 , E 1 ′, . . . ) to a selected voltage value for a selected duration. The first voltage source  312  is then deactivated and the second voltage source  314  is activated to raise the second electrodes (E 2 , E 2 ′, . . . ) to a selected voltage value for the selected duration. The second voltage source  314  is then deactivated and the third voltage source  412  is activated to raise the third electrodes (E 3 , E 3 ′, . . . ) to a selected voltage value for the selected duration. The third voltage source  412  is then deactivated and the fourth voltage source  414  is activated to raise the fourth electrodes (E 4 , E 4 ′, . . . ) to a selected voltage value for the selected duration. After the fourth voltage source  414  is deactivated, the activation sequence can be repeated. 
     In various embodiments, the selected voltage is the same for each of the voltage sources and the duration for each the voltages sources are activated at the same. In the illustrative activation sequence of  FIG.  7   , the first activation pulse  702  (for the first voltage source  312 ) is initiated at about 0.5 milliseconds (msec) and is deactivated at about 1 msec. The second activation pulse  704  (for the second voltage source  314 ) is initiated at about 1 msec and is deactivated at about 1.5 msec. The third activation pulse  706  (for the third voltage source  412 ) is initiated at about 1.5 msec and is deactivated at about 2 msec. The fourth activation pulse  708  (for the fourth voltage source  414 ) is initiated at about 2 msec and is deactivated at about 2.5 msec. Each of the activation pulses has a magnitude of 400 Volts (V). It is to be understood that the duration and magnitude for the pulses shown in  FIG.  7    are illustrative only. The duration and magnitude of the pulse can be any selected value, in various embodiments. 
       FIG.  8    shows an alternative arrangement  800  of the electrodes within the window  106 . Each of the electrodes forms a spiral, with the spiral of a selected electrode being interleaved between its adjacent spirals. By activating the electrodes using the activation sequence of  FIG.  7   , a droplet can be drawn from a center “C” of the window  106  to a circumference or perimeter of the window. The electrode spirals can lie within a single electrode layer. 
       FIG.  9    (Prior Art) shows a graph  900  of frequency-related resistivity values for different accumulation conditions of the window  106 . Frequency is shown along the abscissa in kilohertz (kHz) and resistivity is shown along the ordinate axis in Megaohms (MΩ). A first frequency group  902  includes resistivity measurements obtained when the hydrophobic glass is clear or dry (i.e., with no fluid on the glass). A second frequency group  904  includes resistivity measurements obtained when the hydrophobic glass has a layer of ice. A third frequency group  906  includes resistivity measurements obtained when the hydrophobic glass has a layer of water. The resistance on the window  106  can be measured and compared or matched with regions on graph  900  to determine the surface condition (i.e., accumulation condition). 
     The electrodes can be operated in various modes. In a first mode, a voltage can be applied at a selected frequency to at least the first electrode E 1  and a resistance or impedance resulting from the applied voltage can be measured. Given data from the graph  900 , the processor  108  can determine from the frequency and resistance measurements whether there is ice or water on the glass or whether the glass is dry. Once it is determined that ice is on the window, the processor  108  can operate the electrodes in a second mode to activate the electrodes to heat the ice, thereby melting the ice. Due to the electric field generated by the electrodes, heat is generated by the resistance of ice without heating the outermost layer  212 . In a third mode, which is used when there is no more ice on the window but water remains on the window, the electrodes can be activated in sequence to move the water from the glass. 
     In various embodiments, in order to melt ice, a width of the electrodes is about 300 micrometers (μm) and a gap between electrodes (i.e., first electrode E 1  and second electrode E 2 ) is about 100 μm. An electrode is activated at about 30 kHz to melt ice and about at 1 kHz to move water along the surface of the glass. The second dielectric layer  210  has a thickness from about 2 μm to about 10 μm. An insulation layer can be placed between the electrode layers and the innermost glass  202  in order to reduce the amount of heat that is transferred to the glass. 
       FIG.  10    shows a graph  1000  illustrating a melting rate of ice using the de-icing methods disclosed herein. Time is shown along the abscissa in seconds and a percentage of water phase on the window is shown along the ordinate axis as a ratio. At time t=0, the window has a total layer of ice, as indicated by the percentage being zero. At about 25 seconds, the ice begins to melt and transition to water, as shown by the increase in the water percentage. By about t=45 seconds and onward, the window is completely covered by the water phase (i.e., all of the ice is melted). 
     Although the invention is described herein as having four electrodes per electrode group, this is not meant to be a limitation of the invention. The number of electrodes in an electrode group can be any suitable number. In various illustrative embodiments, the invention can include three, five or six electrodes per electrode group. 
     While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof