Electronic device to detect contamination, melt ice and remove water

A Lidar system, window of the Lidar system and a method of moving a fluid along a window. The window includes a first electrode disposed on a first side of a 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.

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.

DETAILED DESCRIPTION

In accordance with an exemplary embodiment,FIG.1shows a vehicle100having a Lidar system102. The Lidar system102includes a housing104and a window106. A laser (not shown) is disposed in the housing104and the window106allows the laser beam to pass through. In various embodiments, the window106is oriented at a non-zero angle with respect to a horizontal direction. The window106can 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 window106includes circuitry therein, as disclosed herein, suitable for cleaning fluids, such as rain, from its outer surface. The vehicle100further includes a processor108that operates the Lidar system102as well as the circuitry for cleaning fluids from the window106.

FIG.2shows a side cross-sectional view200of the window106of the Lidar system102, in an embodiment. The window106has been rotated from its orientation inFIG.1for ease of explanation. The window106includes an innermost glass202or innermost layer, generally made of a transparent or semi-transparent glass through which a laser beam can be transmitted. A first electrode layer204and a second electrode layer206are placed on top of (i.e., on the outer surface of) the innermost glass202. The first electrode layer204is disposed directly on top of the innermost glass202and the second electrode layer206is disposed on top of the first electrode layer204, such that the first electrode layer204is between the innermost glass202and the second electrode layer206. A first dielectric layer208is disposed between the first electrode layer204and the second electrode layer206and a second dielectric layer210is disposed on top of the second electrode layer206. An outermost layer212can be disposed on top of the second dielectric layer210. The outermost layer212can be glass or other suitable material. The outermost layer212is exposed to contamination from the outside environment such as dirt, rain, etc. In various embodiments, the outermost layer212is made of hydrophobic glass material.

The first electrode layer204includes a first electrode E1and a second electrode E2. The first electrode E1and the second electrode E2form a first electrode pair P1. The second electrode layer206includes a third electrode E3and a fourth electrode E4. The third electrode E3and the fourth electrode E4form a second electrode pair P2. The first electrode pair P1and the second electrode pair P2form a first electrode group EG1. The first electrode, second electrode, third electrode and fourth electrode are aligned in a row along a selected direction214in the order shown (i.e., E1, E2, E3, E4). In various embodiments, the window106includes a plurality of electrode groups (EG1, EG2, . . . ) aligned in the selected direction214. The selected direction214can be in a vertical direction along the window106, oriented toward a bottom edge of the window. However, this is not meant to be a limitation of the invention.

The outermost layer212includes a first surface (bottom surface230) and a second surface (top surface232) opposite the first surface. The top surface232is exposed to the elements. Outermost layer212is coated onto the second dielectric layer210. The second dielectric layer210covers both the first electrode pair P1and the second electrode pair P2. Due to the presence of the first dielectric layer208and the second dielectric layer210, the first pair P1is separated from a bottom surface230by a first distance and the second pair P2is separated from the bottom surface230by a second distance.

In an embodiment, the electrodes are activated in a selected activation sequence progressing along the selected direction214. Activating an electrode refers to applying a non-zero voltage to the electrode. An activation sequence is applied in which one electrode (e.g., E1) is held at a high voltage while the remaining electrodes (e.g., E2, E3, E4) 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 surface232of the outermost layer212is drawn to a location of the outermost layer212that is opposite the activated electrode. By activating the electrodes in order (i.e., E1first, E2second, E3third and E4fourth), the droplet can be moved along the surface and eventually off to a side of the window106.

In an embodiment, the first electrode E1is activated to draw the droplet to a first location220opposite the first electrode E1. The first electrode E1is then deactivated or set to low voltage (i.e., set to ground) and the second electrode E2is activated to draw the droplet from the first location220to a second location222opposite the second electrode E2. Continuing this process, the second electrode E2is deactivated and the third electrode E3is activated to draw the droplet from the second location222to a third location224opposite the third electrode E3. Finally, the third electrode E3is deactivated and the fourth electrode E4is activated to move the droplet from the third location224to a fourth location226opposite the fourth electrode E4. The fourth location226is a destination location for the droplet within the first electrode group EG1. When the droplet is at the fourth location, repeating the activation sequence (i.e., activating first electrode E1) activates the first electrode E1′ of the adjacent electrode group EG2, thereby drawing the droplet from the fourth location226to a fifth location228opposite the electrode E1′. The droplet can thus be passed between electrodes groups and moved along the surface until a last electrode or edge of the window106is reached, thereby moving the droplet off to a side of the window106.

FIG.3shows a top view300of the first electrode pair P1of the window106. The top view300is a view looking into the window106from outside the vehicle100(i.e., with the outermost layer212closest to the viewer). The top view300shows a first conductor302and a second conductor304. The first conductor302includes strips that branch off of a first conductive backbone306. The strips form the first electrodes (E1, E1′, E1″, . . . ) within their respective electrode groups (EG1, EG2, EG3, . . . ). The first conductor302is coupled to a first voltage source312. Activation of the first voltage source312raises each of the first electrodes (E1, E1′, E1″, . . . ) to a selected voltage value. The second conductor304includes strips that branch off of a second conductive backbone308. The strips form the second electrodes (E2, E2′, E2″, . . . ) within their respective electrode groups (EG1, EG2, EG3, . . . ). The second conductor304is coupled to a second voltage source314. Activation of the second voltage source314raises each of the second electrodes (E2, E2′, E2″, . . . ) to selected voltage value.

FIG.4shows a top view400of the second electrode pair P2of the window106. The top view400shows a third conductor402and a fourth conductor404. The third conductor402includes strips that branch off of a third conductive backbone406. The strips form the third electrodes (E3, E3′, E3″, . . . ) within their respective electrode groups (EG1, EG2, EG3, . . . ). The third conductor402is coupled a third voltage source412. Activation of the third voltage source412raises each of the third electrodes (E3, E3′, E3″, . . . ) to selected voltage value. The fourth conductor404includes strips that branch off of a fourth conductive backbone408. The strips form the fourth electrodes (E4, E4′, E4″, . . . ) within their respective electrode groups (EG1, EG2, EG3, . . . ). The fourth conductor404is coupled to a fourth voltage source414. Activation of the fourth voltage source414raises each of the fourth electrodes (E4, E4′, E4″, . . . ) to selected voltage value.

FIG.5shows a top view500of the conductors ofFIGS.3and4as arranged in the window106of the Lidar system102, in an illustrative embodiment. As shown inFIG.5, the conductors are arranged such that their respective electrodes form a repeating pattern. The first electrode group EG1includes, in order, electrodes (E1, E2, E3, E4). The second electrode group EG2is adjacent the first electrode group EG1and includes, in order, electrodes (E1′, E2′, E3′, E4′). The third electrode group EG3is adjacent the second electrode group EG2and includes, in order, electrodes (E1“, E2”, E3″, E4″). The electrode groups are aligned in the same direction as their electrodes along the selected direction214.

In the arrangement shown inFIG.5, the first conductor302and the second conductor304are planar elements and are placed side by side within the first electrode layer204. Similarly, the third conductor402and the fourth conductor404are planar elements and are placed side by side within the second electrode layer206.

FIG.6shows an alternative arrangement600of the conductors disposed in the window106. The alternative arrangement allows the electrodes to lie within a single electrode layer. Referring to the first electrode group EG1for illustrative purposes, the electrodes (E1, E2, E3, E4) form the first electrode group EG1and lie entirely within the single electrode layer. The third conductor402includes a jump section602that extends out of the electrode layer in order to prevent electrical contact with the first conductor302and second conductor304. Similarly, the fourth conductor404includes a jump section604that extends out of the electrode layer in order to prevent electrical contact with the first conductor302and second conductor304.

FIG.7shows an activation sequence for the voltage sources shown inFIGS.5and6, 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 source312is activated to raise the first electrodes (E1, E1′, . . . ) to a selected voltage value for a selected duration. The first voltage source312is then deactivated and the second voltage source314is activated to raise the second electrodes (E2, E2′, . . . ) to a selected voltage value for the selected duration. The second voltage source314is then deactivated and the third voltage source412is activated to raise the third electrodes (E3, E3′, . . . ) to a selected voltage value for the selected duration. The third voltage source412is then deactivated and the fourth voltage source414is activated to raise the fourth electrodes (E4, E4′, . . . ) to a selected voltage value for the selected duration. After the fourth voltage source414is 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 ofFIG.7, the first activation pulse702(for the first voltage source312) is initiated at about 0.5 milliseconds (msec) and is deactivated at about 1 msec. The second activation pulse704(for the second voltage source314) is initiated at about 1 msec and is deactivated at about 1.5 msec. The third activation pulse706(for the third voltage source412) is initiated at about 1.5 msec and is deactivated at about 2 msec. The fourth activation pulse708(for the fourth voltage source414) 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 inFIG.7are illustrative only. The duration and magnitude of the pulse can be any selected value, in various embodiments.

FIG.8shows an alternative arrangement800of the electrodes within the window106. 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 ofFIG.7, a droplet can be drawn from a center “C” of the window106to a circumference or perimeter of the window. The electrode spirals can lie within a single electrode layer.

FIG.9(Prior Art) shows a graph900of frequency-related resistivity values for different accumulation conditions of the window106. Frequency is shown along the abscissa in kilohertz (kHz) and resistivity is shown along the ordinate axis in Megaohms (MΩ). A first frequency group902includes resistivity measurements obtained when the hydrophobic glass is clear or dry (i.e., with no fluid on the glass). A second frequency group904includes resistivity measurements obtained when the hydrophobic glass has a layer of ice. A third frequency group906includes resistivity measurements obtained when the hydrophobic glass has a layer of water. The resistance on the window106can be measured and compared or matched with regions on graph900to 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 E1and a resistance or impedance resulting from the applied voltage can be measured. Given data from the graph900, the processor108can 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 processor108can 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 layer212. 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 E1and second electrode E2) 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 layer210has a thickness from about 2 μm to about 10 μm. An insulation layer can be placed between the electrode layers and the innermost glass202in order to reduce the amount of heat that is transferred to the glass.

FIG.10shows a graph1000illustrating 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.