ES2347005T3 - RAIN SENSOR WITH FRACTAL CONDENSE (RES). - Google Patents

Abstract

A rain sensor for installation with a vehicle window comprising: a sensor circuit comprising at least a first sensor capacitor (C1, C2, C3, C4) adapted to be supported by a vehicle window, the first sensor capacitor being sensitive to moisture on a surface external to said window under installation conditions; the first sensor capacitor having first and second separate capacitor electrodes (7, 8) that are substantially coplanar; and in which at least part of the first sensor capacitor has a fractal geometry, characterized in that the fractal geometry is selected from the group consisting of a Hilbert fractal and a Cantor fractal.

Description

Rain sensor with condenser (s) fractal (s).

This invention relates to a system for detection of the presence of rain in embodiments of a vehicle windshield, one or more of the condenser (s) Sensor (s) has a fractal geometry.

Background and summary of exemplary embodiments of the invention

The presence of moisture (e.g., rain or condensation) on windshields and / or rear windows of the vehicle can create dangerous driving conditions for drivers, passengers and pedestrians if not removed with speed. Wiper blades are a common and well known to eliminate such materials and reduce risks of driving during dangerous conditions. Sensors rain have been developed to detect the presence of moisture (e.g., rain or other condensation) on the windshield of the vehicle, and to activate and deactivate the windshield wipers, as necessary, when this humidity is detected. Automatic detection of rain, sleet, fog and the like, and take action appropriate (for example, enable / disable scrapers windshield wiper at adequate speed) potentially reduces the distractions to the driver, allowing the driver Focus better on the road ahead. Without However, activating / deactivating the windshield wipers improperly or not to activate them when there is humidity can also create dangerous conditions. In addition, such systems are also susceptible to "dirt" distractions that may cause false readings / actions of the windshield wiper when dirt on the windshield.

Some conventional rain sensors are based on an electro-optical concept. According to certain such techniques, raindrops are detected only by measuring the change in the total internal reflection of a light beam outside the glass-air interface Other electro-optical techniques have tried to analyze the luminosity of a section of a window "image" to detect raindrops or fog in a window. However, these optical techniques have areas of limited detection, are quite expensive, and can result in erroneous detection indications due to the use of optical images As the only detection method.

US Patent No. 6,373,263 to Netzer explains how to use capacitive rain sensors and read the current differential between two condensers on the windshield. Unfortunately, the Netzer system also has important disadvantages For example, the Netzer system may be subject to certain harmful effects of electromagnetic interference (EMI), as well as interference from other sources. For example, when external bodies (e.g., a human hand, the waves of radius, etc.) interfere with the function of the capacitors, the excitation charges and receiving electrodes may vary uncontrollably in Netzer, which leads to false alarms or detections and therefore to possibly produce false actions of the windshield wipers and / or detections. The Netzer system is also subject to possible false readings produced by drastic changes of temperature in view of the reference condenser system used by Netzer, where the Netzer reference capacitor It has a different geometry / shape / size than the condenser sensor.

A rain sensor with a condenser that has a meander shape is described in US 2003/0080871.

Thus, it can be seen that there is a need in the technique of a rain sensor that has an operation and / or efficient detection.

In accordance with this invention, the capacitors They are formed based on a fractal pattern. One or more of the capacitors are formed based on a Hilbert fractal pattern or a a set of Cantor. These fractal structures maximize or amplify the periphery and therefore result in a large capacitance for a given area. The use of two fractal designs dimensions also allows the sensor to take up little physical space in the window and at the same time be electrically larger than its physical size The concentration of lateral flow in a geometry fractal can also allow the sensor to detect rain / water not necessarily distributed over the actual physical area of the sensor in certain exemplary embodiments of this invention. Also, in its highest iteration (s) a fractal capacitor (s) has (n) an attribute of being its own Faraday screen or quasi-screen of Faraday which can reduce the adverse effects of EMI interference or the like.

Brief description of the drawings

These and other features and advantages are they will understand better and more completely by referring to the following detailed description of embodiments illustrative by way of example together with the drawings, of those who:

Figure 1 (a) is a block diagram of components of an example rain sensor.

Figure 1 (b) is a sectional view. transverse of a rain sensor, which can use the characteristics of Fig. 1 (a) and / or one or more of Figs. 2-12.

Figure 1 (c) is a sectional view. transverse of a rain sensor, which can use the characteristics of Fig. 1 (a) and / or one or more of Figs. 2-12.

Figure 1 (d) is a sectional view. transverse of a rain sensor, which can use the characteristics of Fig. 1 (a) and / or one or more of Figs. 2-12.

Figure 1 (e) is a sectional view. transverse of a rain sensor, which can use the characteristics of Fig. 1 (a) and / or one or more of Figs. 2-12.

Figure 1 (f) is a sectional view. transverse of a rain sensor, which can use the characteristics of Fig. 1 (a) and / or one or more of Figs. 2-12.

Figure 2A is an optimized pattern by way of example for a capacitive quadrant system based on Hilbert fractals, in which said capacitors can be provided in the window as a sensor system in one or more of Figs. 1 (a) -1 (f) and 4-12, for example.

Figure 2B is another optimized pattern to title example for a capacitive quadrant system, in which said capacitors can be provided in the window as a sensor system in one or more of Figs. 1 (a) -1 (f) and 4-12, by example.

Figure 3 is an enlarged drawing of another capacitive example quadrant system, in which said capacitors can be provided in the window as a system of sensors in one or more of Figs. 1 (a) -1 (f) and 4-12, by example.

Figure 4 is a circuit diagram of example that includes an example circuit system used for a writing clock pulse on the electronics reading of output, for use in one or more of Figs. 1 (a) -1 (f) and 5-12, by example.

Figure 5 is a circuit diagram of example that includes an example circuit system used for A pulse of erase clock on the output reading electronics, for use in one or more of Figs. 1 (a) -1 (f) and 6-12, by example.

Figure 6 is a timer diagram a sample title derived from the reading circuit system of output of Figs. 4-5.

Figure 7 is a flow chart or diagram of states by way of example showing how data can be used autocorrection and cross correlation to control windshield wipers, which can be used together with one or more of the Figs. 1-6 and 8-12.

Figure 8 is a flow chart by way of example that shows how autocorrect data can be used and cross correlation to control windshield wipers, which can be used together with one or more of Figs. 1-7 and 9-12.

Figure 9 is a stylized view by way of example of how a raindrop can travel through a windshield

Figure 10 is a graph that draws some maximum experimentally obtained values for example of non-standard autocorrelations for different disturbances

Figure 11A is a snapshot of experimentally obtained autocorrelation of indicative example of strong rain.

Figure 11B is a snapshot of experimentally obtained autocorrelation of indicative example of A slight haze

Figure 11C is a snapshot of experimentally obtained autocorrelation of indicative example of CB radio interference.

Figure 11D is a snapshot of experimentally obtained autocorrelation of indicative example of a grounded body with a voltage.

Figure 12A is a correlation matrix to Sample title indicative of light rain.

Figure 12B is a correlation matrix to Sample title indicative of heavy rain.

Figure 13 is an example of autocorrelation of according to an exemplary embodiment of this invention.

Figure 14 is a table showing data from example cross correlation of capacitors C1, C2.

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Figure 15 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 16 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 17 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 18 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 19 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 20 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 21 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 22 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 23 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 24 is a correlation graph cross, in which cross correlation values are plotted versus time periods (periods of time are in microseconds in the temporal domain), using certain signals from Fig. 14.

Figure 25 is a block diagram that illustrates the circuit system and / or signal processing when a sensor capacitor (eg C1) is present, including sigma-delta modulation.

Figure 26 is a block diagram that illustrates the circuit system and / or signal processing when there is a plurality of capacitors (eg C1-C4) present, including sigma-delta modulation.

Figure 27 is a block diagram that illustrates sigma-delta modulation; being carried out this processing through a circuit system, in firmware and / or software.

Figures 28 (a) Y (28b) are about schematic diagrams illustrating the advantages of using electrodes floats for sensor capacitors (e.g. C1-C4).

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Detailed description

Referring below more specifically to the attached drawings in which numbers of similar references indicate similar parts in all views.

A rain detection system is provided and includes a capacitance based detection that translates a physical input signal (e.g., the presence of a drop of water in a windshield, or the like) on a digital electric voltage signal that is received and interpreted in a program (s) of software or in a circuit (s) that decides Whether or not the windshield wipers should be activated, and, if applicable, optionally its adequate speed. In this way, the capacitive coupling to detect water and / or other material in the outer surface of a window like the windshield, the roof solar and / or the rear window of the vehicle. It will be appreciated that computational methods can be carried out using hardware or a combination of hardware and software in different ways of exemplary embodiment of this invention. May not be necessary no capacitance or no reference capacitor, (i.e. a compensation capacitor is not necessary).

The system can take advantage of a permittivity equation, which provides a physical quantity that describes how it affects an electric field and is affected by a medium. An example basic permittivity equation
is:

one

where D is the electric flow, ? 0 is the dielectric constant of a vacuum, E is a electric field (eg the voltage set between plates or electrodes divided by distance, or V / m), and P is the Polarization. The polarization P can be described mathematically in greater detail how:

2

where \ varepsilon_ {r} is the relative permittivity (e.g., the dielectric constant of water, ice, dirt or anything else that could be found in an exterior surface of a window like a windshield). In In general, a high value of \ varepsilon_ {i} will correspond to high polarizability The permittivity of glass is approximately 8, and the water permittivity is approximately 85. By substitution and factorization, then, the equation of permittivity can be rewritten how:

3

In this way, it can be seen that D is the response to excitation E.

The capacitance C is given by C = Q / V , where Q is the load and V is the potential, in volts. In addition, C = \ Phi / V , where \ Phi is the electrical flow associated with the charge Q. By Gauss's Law:

4

where dA is the area of a square differential on the closed surface S. By replacement, then, it is clear that capacitance is related to the Difference of potential:

5

These equations form the basis of a technical example to measure the interaction of water on glass using a sensor with a capacitive system to explore on the window (e.g., glass). In particular, the data can be used of a sensor that includes at least one or two or more capacitor (s) (eg C1, C2, C3, etc.) to detect if there is or not moisture (e.g., rain or the like) on a surface outside of a window such as the windshield or the rear window of vehicle. The equations indicated above illustrate that the presence of water on the window surface can affect the Capacitance of a properly placed sensor capacitor.

Fig. 1 (a) is a block diagram of example components of a humidity sensor (eg, rain). The power supply 10 is connected to the output reading electronics 12 which may include one or more of hardware, firmware and / or software. As will be described in greater detail below, the sensor includes one or more capacitors to construct a capacitive sensor 5 in certain exemplary embodiments. Capacitors each having a pair of approximately coplanar electrodes arranged in a fractal pattern in the sensor according to the invention are used. The fractal pattern can be divided into a capacitive system. While the window can be flat or curved, the capacitor electrodes of a given sensor capacitor (C1, C2, C3 and / or C4) are considerably coplanar to each other and are supported by the flat or curved window, although it can There is a small curvature of the glass. The data of and / or related to the capacitor (s)
Capacitive sensor sensor (s) 5 are received and read by an output readout electronics 12 that may be composed of one or more of hardware, firmware and / or software. The output reading electronics 12 captures the electrical noise and converts it to a digital signal (s). This digital signal (s) is passed to a calculation module 14 (which may be composed of one or more of hardware, firmware and / or software) that determines what action the windshield wipers should take. For example, windshield wipers can initiate a single wiper action, low speed windshield actions, high speed windshield actions, etc., based on the analyzed data of and / or related to the capacitive sensor. Windshield wipers can also be deactivated, their speed reduced / increased, etc., based on the data analyzed and / or related to the capacitive sensor. A windshield wiper control system motor 16 receives instructions from the calculation module 14 and instructs the windshield wipers 18. to carry out the appropriate action.

The capacitive sensor 5 is connected to a Bus of Local interconnection (LIN bus) of a vehicle. A LIN bus (no shown) is usually a serial bus to which they connect Slave devices in a car. A LIN bus usually runs a handshake with slave devices to ensure that they are, for example, connected and in functional state. In addition, a LIN bus can provide other information to the devices slaves such as the current time.

Capacitive sensor 5 includes a plurality of capacitors in the form of any suitable system.

Fig. 1 (b) is a sectional view. transverse of a vehicle window that includes a sensor humidity. A vehicle windshield includes a glass substrate interior 1 and an exterior glass substrate 2 that are laminated to at the same time by means of an interlayer 3 which includes a polymer of a material such as polyvinyl butyral (PVB) or similar. May provide a coating 4 of low e (low emissivity) optional on the inner surface of the outer glass substrate 2 (or even on the surface of the substrate 1). A coating of low E 4 usually includes at least one reflective layer of Fine IR of a material such as silver, gold or similar interleaved between at least some first and second dielectric layers of a material such as silicon nitride, tin oxide, zinc oxide, or Similar. Sample low E 4 coatings, for the purpose of example and without limitations, are described in US Pat. Nos. 6,686,050, 6,723,211, 6,782,718, 6,749,941, 6,730,352, 6,802,943, 4,782,216, 3,682,528, and 6,936,347.

Fig. 1 (b) illustrates an example capacitor of the capacitive sensor. While the capacitive sensor of Fig.
1 (a) usually includes a plurality of capacitors in a system, only one sensor capacitor is shown in Fig. 1 (b) for simplicity. The other capacitors are similar in cross-section to that shown in Fig. 1 (b) in certain exemplary embodiments of this invention. The example capacitor (C1, C2, C3 or C4) of the capacitive sensor shown in Fig. 1 (b) includes a pair of separate coplanar or considerably coplanar condenser electrodes 7 and 8. Electrodes 7 and 8 are made of a conductive material that can be printed or otherwise formed in the window. For example, the electrodes of capacitor 7 and 8 of the sensor capacitor may be made of or include silver, ITO (indium tin oxide), or other suitable conductive material. The capacitor shown in Fig. 1 (b) is affected by a drop of water on the outer surface of the window because the electric field Es of the capacitor extends to or beyond the outer surface of the window as shown in Fig. 1 (b) and in that way can interact with the raindrop or other material on the exterior surface of the window. The signals received from and / or related to the capacitor (s) sensor (s) and the analysis thereof are described herein.

In Fig. 1 (b), a layer is provided opaque insulation (e.g., fried black or enamel, or the like) 9 in the window on electrodes 7 and 8 in order to hide the electrodes 7, 8 from the view of the passenger (s) that You are sitting inside the vehicle. This way, you can it is appreciated that the opaque layer 9 is provided only in one small part of the window, including in the area in which the capacitive system of the sensor capacitor system rain is located. The capacitive system of the rain sensor and in this way the opaque layer 9 can be placed on the windshield of a vehicle in an area near the mirror mounting bracket rearview. The opaque layer 9 (e.g., fried black or enamel) can make contact with the fractal pattern of the electrodes of the capacitor 7, 8 directly because layer 9 is not conductive. However, even if a layer of black frit 9 was conductive (what is possible), its dielectric constant is similar to that of the water so that it will not adversely interfere with the capture of data from and / or related to capacitors C1-C4 and the associated analysis:

Fig. 2A is a top or plan view that illustrates an example capacitive sensor system that includes four capacitors C1, C2, C3 and C4. Each one of these capacitors C1, C2, C3 and C4 include electrodes of first and second separate coplanar capacitor 7 and 8 as it shown in Fig. 1 (b) (or in any of Fig. 1 (c) -1 (f)). Electrodes capacitor 7 and 8 of each C1-C4 capacitor can be made of conductive silver frit or similar as shown in Fig. 2A. In addition, there may be a space 22 of approximately 0.2 to 1.5 mm, more preferably about 0.3 to 1.0 mm (e.g. 0.6 mm), between coplanar condenser electrodes 7 and 8 of each capacitor (C1, C2, C3 and / or C4) as shown in the Fig. 2A. In Fig. 2A, capacitors C1-C4 they are covered with a layer of black insulated frit 9 which is the same as the opaque layer 9 indicated above with respect to the Fig. 1 (b). In Fig. 2A, a system of contact plates in the center of the sensor system, and includes four contact plates electrically connected to the respective electrodes 7 of capacitors C1-C4, and four contact plates electrically connected to the respective electrodes 8 of capacitors C1-C4. An example contact plate is indicated by the number of reference 28 in Fig. 2A. The four colored contact plates target 28 of Fig. 2A are electrically connected to the respective capacitor electrodes 7 of the capacitors C1-C4, while the color contact plates dark gray 28 of Fig. 2A are electrically connected to the respective capacitor electrodes 8 of the capacitors C1-C4. All sensor capacitors C1-C4 are sensitive to moisture like own rain the external surface of the window.

In the embodiment of the invention of the Fig. 2A, each of the capacitors C1-C4 of the Capacitive sensor is formed using fractal geometry. In concrete, each of the coplanar electrodes 7 and 8 of each capacitor C1-C4 is formed with a geometry fractal Fractal design patterns allow you to get a great capacitance in a very small area, and are therefore desirable about other geometries in rain sensor applications.

In the embodiment of Fig. 2A, you can show that the coplanar electrodes 7 and 8 of each capacitor (where electrodes 7 and 8 are shown but not marked on the Fig. 2A due to the dark color of frit 9, but they are separated through spaces 22) they present fractal geometries and are arranged substantially in parallel with each other throughout the Sinuous length of each capacitor. In other words, each electrode 7, 8 of a given capacitor (e.g., C1, C2, C3 or C4) It has a sinuous shape in fractal geometry, but it remains substantially parallel to the other electrode (the other 7, 8) of the capacitor over the entire sinuous length of the capacitor. The overall length of each capacitor (e.g., C1), along the Sinuous length of the fractal is approximately 25 to 200 mm in certain exemplary embodiments of this invention, more preferably about 30 to 90 mm, with an example that is of approximately 50 mm.

The fractal pattern of Fig. 2A is a pattern Hilbert's fractal. Electrodes 7, 8 of the capacitors C1-C4 in the embodiment of Fig. 2A They form a fractal pattern of Hilbert. Specifically, the capacitors shown in Fig. 2A have a Hilbert fractal shape of third order. Hilbert's fractals are continuous fractals that they fill the space, with fractal dimensions of two. This means that higher order fractals will have a more square shape. A Hilbert's fractal can be formed using the following L system:

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where "Angle 90" sets The following rotations at 90 degrees, X and Y are functions defined, "F" means "draw forward", "+" means "turn counterclockwise of the clock ", and" - "means" turn in the direction of clockwise. "In certain embodiments of example of this invention, as shown in Figs. 2A, 2B and 3, all sensor capacitors of the sensor system can have an identical or practically identical

Each of the capacitors C1-C4 in the sensor system can be electrically floating (this can be called a virtual earth in certain example cases) in order not to have a land fixed common as zero fixed volts, and / or be spatially separate or similar what may be useful with respect to correlation functions In addition, the lack of a common land means that the capacitive system will not be subject to effects adverse effects such as EMI interference thereby reducing the potential for false actions of the windshield wipers, false detections, and the like.

The fractal design for capacitors C1-C4 can be used in any of Figs. 1 (a) -1 (f).

Fig. 1 (c) is a sectional view. cross section of another example, which can use the system of Fig. 1 (a) and one or more of Figs. 2-12. In the Fig. 1 (c), the vehicle window (e.g., rear window) It is made of only a glass sheet 10, and the electrodes 7, 8 of the capacitor are arranged on, directly or indirectly, the inner main surface of the sheet of glass 10. The condenser (eg, C1) shown in Fig. 1 (c) is designed in such a way that it is affected by a raindrop (or other material) on the outer surface of the window because the electric field of the capacitor is extended up to or beyond the exterior surface of the window as shown in Fig. 1 (c) and in that way it can interact with the raindrop or other material on the outer surface of window. Each of the C1-C4 capacitors It is similarly formed. It should be noted that the use of the word "on" here covers both directly on and indirectly about, and is not limited to physical contact to unless expressly stated. An opaque layer 9, similar to the shown in the embodiment of Fig. 1 (b), also can be provided in the embodiment of Fig. 1 (c) if desired.

Fig. 1 (d) is a sectional view. cross section of another example, which the system of Fig. 1 (a) and one or more of Figs. 2-12. In the Fig. 1 (d), the vehicle window (e.g. windshield laminated) includes 1 and 2 laminated glass sheets at the same time by means of a polymer-based interlayer 3, and optionally includes a low E 4 coating on any of the substrates 1 or 2. Fig. 1 (d) differs from Fig. 1 (b) in that the electrodes 7, 8 of the capacitor are arranged on the surface main glass substrate 1 that is farther from the inside vehicle. The capacitor electrodes 7, 8 can make contact with polymer interlayer 3 in this form of realization, in certain example cases. The condenser (p. eg, C1, C2, C3 or C4) shown in Fig. 1 (d) is designed in such a way that it is affected by a raindrop (or other material) on the outside surface of the window because the field electric is the capacitor extends to or beyond the exterior surface of the window as shown in Fig. 1 (d) and that way it can interact with the raindrop or other material on the exterior surface of the window. Each of the C1-C4 capacitors of the sensor system is formed in a manner similar to that shown for the capacitor of Fig. 1 (d). The opaque layer 9 can also be arranged in Fig. 1 (d) if desired, on a part of the window so that the condenser electrodes are hidden from view of the passengers of the vehicle. In fig. 1 (d), electrodes 7 and 8 may be formed of a conductive silver frit or ITO printed or stamped directly on and in contact with the surface of the substrate 1. However, this invention is not limited thereto, and electrodes 7 and 8 of one or more of the sensor capacitors may instead be formed and stamped from an IR reflective layer conductive metal (e.g., a silver-based layer) of a low E 4 coating that is supported by the window.

Fig. 1 (e) is a cross-sectional view of another example, which may use the system of Fig. 1 (a) and one or more of Figs. 2-12. In Fig. 1 (e), the vehicle window (e.g. laminated windshield) includes laminated glass sheets 1 and 2 at the same time by means of a polymer-based interlayer 3, and optionally includes a coating low E 4 on any of the substrates 1 or 2. Fig. 1 (e) differs from Fig. 1 (b) in that the electrodes 7, 8 of the capacitor (eg, C1, C2, C3 or C4) are arranged on the main surface of the outer glass substrate 2 that is closer to the interior of the vehicle. The capacitor electrodes 7, 8 can make contact with the polymer interlayer 3. The capacitor (eg, C1, C2, C3 or C4) shown in Fig. 1 (e) is designed such that it looks affected by a raindrop (or other material) on the outer surface of the window because the electric field of the capacitor extends to or beyond the outer surface of the window as shown in Fig. 1 (e)
and that way it can interact with the raindrop or other material on the outside surface of the window. Each of the capacitors C1-C4 of the sensor system is formed in a manner similar to that shown for the capacitor of Fig. 1 (e). The opaque layer 9 can also be arranged in Fig. 1 (e) if desired, on a part of the window so that the condenser electrodes are hidden from view of a passenger (s) of vehicle.

Fig. 1 (f) is a sectional view. cross section of another example, which the system of Fig. 1 (a) and one or more of Figs. 2-12. In the Fig. 1 (f), the vehicle window (e.g. windshield laminated) includes 1 and 2 laminated glass sheets at the same time by means of a polymer-based interlayer 3, and optionally includes a low E 4 coating on any of the substrates 1 or 2. Fig. 1 (f) differs from Fig. 1 (b) in that the electrodes 7, 8 of the capacitor (e.g., C1, C2, C3 or C4) are disposed on the main surface of the inner glass substrate 1 that is closer to the interior of the vehicle, through the support element 12. The support element 12, located between the glass substrate 1 and electrodes 7, 8, may be made of glass, silicon or the like. The condenser (e.g., C1, C2, C3 or C4) shown in Fig. 1 (e) is designed in such a way that is affected by a raindrop (or other material) in the outer surface of the window because the electric field is from capacitor extends to or beyond the outer surface of the window as shown in Fig. 1 (f) and in that way can interact with the raindrop or other material in the exterior surface of the window. Each of the capacitors C1-C4 of the sensor system consists of a similar to that shown for the capacitor of Fig. 1 (f). The opaque layer 9 can also be arranged in Fig. 1 (f) if desired, on a part of the window so that the electrodes 7, 8 of the capacitor are hidden from view of a passenger (s) of vehicle.

Fig. 2B is a plan view of a pattern example for a capacitive quadrant system of C1-C4 fractal shaped capacitors for capacitive sensor according to this invention. The four of them capacitors shown in Fig. 2B are similar to those of the Fig. 2A, except for the specific forms thereof. The Capacitors of Fig. 2B can be used in any of Figs. 1 (a) - (f). The lines to overlapping points show the divisions in four different capacitors C1-C4. The width of the outer line can be approximately 2 mm, and the width of the inner line can be about 1 mm

Fig. 3 is an enlarged drawing of another system example quadrant capacitive of shaped capacitors C1-C4 fractal for capacitive sensor according With this invention. The four capacitors shown in Fig. 3 They are similar to those in Figs. 2A and 2B, except for the forms concrete of them. The fractal capacitors of Fig. 3 can be used in any of Figs. 1 (a) - (f). The lines overlays show an example split between C1-C4 capacitors in Fig. 3. It will be appreciated that some example embodiments may have systems capacitive with only two capacitors. However it is preferably have at least four capacitors to capture and get nuances in disturbances.

The use of fractal geometry for C1-C4 sensor capacitors is advantageous in reducing false readings due to EMI interference. Specifically, the fractals at high iterations help reduce incidents by EMI interference, because the Faraday cage or Quasi-cage Fractal Faraday at high iterations reduces EMI coupling thereby reducing the adverse effects of EMI interference. Fractals at high iterations form quasi-cages of Faraday.

The readout electronics examines the interaction of rain and / or other disturbances in the window. This process can be carried out by sequentially loading the capacitors, read your data, quantify this data and / or eliminate the charges

Fig. 4 is a circuit diagram of a detection circuit or output reading. The detection circuit of Fig. 4 may be made of an electronic unit 12 and the capacitive sensor system 5 of Fig. 1. Any of the capacitors of Figs. 1 (b) -1 (f), 2A, 2B and / or 3 can be used as capacitors C1-C4 of the circuit of Fig. 4. The system of circuit of Fig. 4 is used for a writing clock pulse in Readout electronics. The transistors Q1, Q2 and Q7 they are p channel MOSFETs, being mainly transistors Q1 and Q2 responsible for a writing phase. The transistors Q5 and Q6 They are channel n MOSFETs.

Still in relation to Fig. 4, during a writing phase you enter a writing pulse Clk_ {Wr} in the gate of transistor Q7, which functions as a resistor or a switch, charging one or more of the capacitors C1-C4 of the sensor capacitance C_ {s}. Fig. 6 includes certain signals used in the circuit of Fig. 4 in the writing cycle In the write cycle, transistor Q1 is found in a saturated mode, since its door and its drain are connected, so that Q1 is activated. Q4, Q5 and Q6 are deactivated, and Q2 is activated during write mode. The Transistors Q3 and Q4 are optional. When Q7 is activated by the writing pulse, we have a writing cycle, and Vcc appears in Cs through A and charges one or more of the capacitors C1-C4 of the capacitance of sensor Cs. V_ {cc} It can be a constant voltage, like 5V. One or more of the C1-C4 capacitors can be charged at the same time During a writing cycle. However, the circuit loads and reads capacitors C1, C2, C3 and C4, one by one (eg, see Fig. 6). In this way, during a writing cycle, only charge one of the capacitors C1, C2, C3 or C4.

The above process described for the side left of the sensor circuit of Fig. 4 is basically duplicated on the opposite side or right side of the circuit of Fig. 4. As the current flows through the branch on the left side, the current it also flows in B through the branch of the right side, and they are imitated changes to C_ {s}, or are substantially imitated in the internal replication capacitance C_ {int}. When Q7 is activated, the current also flows through Q2 (found activated) and load C_ {int} using Vcc. In this way, the charging of one of the C1-C4 capacitors by means of the capacitor charge C_ {int}. In other words, C_ {int} is charge at the same level, or substantially at the same level, as the capacitor (eg C1) that is being charged to the other side of the circuit of Fig. 4. The output voltage of the circuit of Fig. 4, Vout (or Vo), is based on C_ {int} and is taken on an electrode or next to it of the C_ {int} capacitor as shown in the Fig. 4. An example formula that reflects Vout (or Vo) is shown in the bottom of Fig. 4. Accordingly, it can be seen that the Vout (or Vo) output of the circuit of Fig. 4-5 refers to and is based on the capacitors C1-C4 of the sensor Cs. More specifically, the exit Vout of the circuit of Fig. 4-5 refers to and is indicative of the status of capacitors C1-C4 and the effects on said surface moisture condensers outside the window, although Vout is not taken directly of capacitors C1-C4. Specifically, Vout (or Vo) is captured during a writing cycle, due to the pulse of writing shown in Fig. 4 (see also Fig. 6). In the formula from the bottom of Fig. 4 for Vout, W1 is for Q1, W2 is for Q2, L1 is for Q1, L2 is for Q2, where W is the width channel of transistors, and L is the channel length of transistors; and V_ {T} is a threshold voltage of each MOSFET. There is Note that alternatively the circuit's Vout output can taken directly (instead of indirectly through C_ {int}) from the sensor capacitors C1-C4.

Transistors Q3, Q4 are optional. These transistors can be found at low voltages (e.g., deactivated) during the writing phase, and activated during erase phase

The output signal Vout (or Vo) of the circuit sensor of Fig. 4 (and Fig. 5) is modulated by modulation sigma-delta. Modulators sigma-delta, which can be used in a converter digital to analog (DAC) sigma-delta, can provide a level of noise formation or filtering of quantification that may be present. Modulators Sample sigma-delta that can be used is described in US Patent Nos. 6,975,257, 6,972,704, 6,967,608 and 6,980,144. In the conversion sigma-delta., the oversampling, noise shaping and / or filtering by decimation Example advantages of modulation sigma-delta include one or more of: i) the Analog anti-lapping filter requirements are less complex and therefore may be cheaper than certain systems of example based on nyquist; ii) a circuit system can be used sampling and retention due to the high sampling frequency input and low precision A / D conversion; iii) since there may be phase (s) of digital filtering behind the A / D conversion, injected noise can be controlled during Conversion process such as power supply oscillation, the voltage reference noise and the noise itself A / D converter; iv) since the converter sigma-delta can be essentially linear can that does not suffer from appreciable differential nolinealities and / or the level (s) of background noise can be independent of the input signal level. Can be obtained Improved S / N ratios.

Fig. 25 which is a simplified version of a sigma-delta modulator system, to modulate and / or convert the output signal Vout (or Vo) of the circuit of Fig. 4 (and Fig. 5). In Fig. 25, a write pulse is used (see pulse at the bottom of Fig. 25) to charge the capacitor sensor (C1, C2, C3 or C4) as explained above with with respect to Fig. 5. Square wave excitation is used (eg, for write and / or erase cycles) on the sensor capacitor for upload and download the same This process is duplicated or imitated, to C_ {int}, as explained herein. Vout output signal (or Vo) of the circuit of Fig. 4 is modulated in sigma-delta using a modulator sigma-delta 60. Modulator 60 can take the shape of a hardware circuit, firmware, and / or software. The pulses of clock 62 of a clock are introduced to modulator 60, which activate the latch of a modulator quantifier 60. Once the signals Vout (or Vo) output have been modulated by the modulator sigma-delta 60, the modulated signals 64 are sent to an optional digital filter 66 (e.g., a low pass filter or Similary). Digital filter 66 processes digital output 64 of sigma-delta modulator, which is a train of 0s and 1s. TO data is then scaled appropriately using a calibration coefficient (s). The data filtered 68 are then read through a serial interface 69 or similar and send to a computer that performs the calculations of correlation for data packet segments. In this way, then it is applied on the interface 69 data a correlation (e.g., autocorrelation or cross correlation) as explained herein. Fig. 26 is similar to Fig. 25, except that Fig. 26 illustrates a capacitor system C1-C4 sensors that are multiplexed through a multiplexor.

Fig. 27 is a block diagram illustrating an example of a sigma-delta modulation that can be carried out in modulator 60 of Figs. 25-26- Again, this modulation can lead to carried out by means of a circuit, firmware and / or software. The signal of analog output Vout (or Vo) of the circuit of Fig. 4 (and Fig. 5) is receives by an adder 70 of the sigma-delta modulator 60. Adder 70 receives the analog Vout (or Vo) signal as well as a feedback signal from a feedback loop 71 of modulator 60. The output of adder 70 is received by the integrator 72 chose output is received by a quantifier 74 as a quantifier of a bit. Digital output 64 is filtered 66 to Then as explained above, and so on. The sigma-delta modulation is advantageous in that provides oversampling and allows to treat noise such as EMI and Reduce its adverse effects. Specifically, noise is distributed by the sigma-delta modulator in the band frequency so that the signal / noise ratio can be improved (Y / N).

Referring again to Fig. 4, each capacitor (C1, C2, C3, C4) is discharged before charging the next. The process of discharging each capacitor is described in connection with the erase pulse, with respect to Figs. 5-6.

Fig. 5 is a circuit diagram of the sensor circuit of Fig. 4, with respect to an erase cycle. During a erase cycle, a capacitor is discharged (C1, C2, C3 or C4) previously loaded before the next write cycle. Fig. 6 includes an example signals used during the erase cycle (s). It is not carried out No reading during the erase phase. During a cycle or a erase phase, Q7 is deactivated (the writing pulse Clkw_ {r} not present), and transistors Q5 and Q6 are activated by a  deletion pulse Clk_ {Er} (see also Fig. 6). This In this way, the capacitor (C1, C2, C3 and / or C4) is discharged to ground (p. eg, V = 0) or a virtual earth (VG), as does C_ {int}. Again, C_ {int} mimics the capacitance of the Cs sensor. One time that the capacitances Cs and C_ {int} have been grounded and unloaded, the pulse and erase cycle end. So you can prepare, charge and read the next capacitor (C1, C2, C3 or C4) in the sequence.

In this way, in relation to Figs. 4-6, it will be appreciated that a rain sensor comprises: a sensor circuit comprising at least about first and second sensor capacitors (e.g., C1 and C2) that are sensitive to moisture on an external surface of a window, and at least one imitator capacitor (C_ {int}) that mimics so minus the loading and / or unloading of at least one of the first and second sensor capacitors; in which a pulse of write (Clk_ {wr}) causes at least the first one to load sensor capacitor (p. e., C1), and an erase pulse (Clk_ {Er}) causes each capacitor to discharge substantially first sensor (e.g., C1) and imitator capacitor (C_ {int}); in the presence of rain on the outer surface of the window in a sensor field of the first sensor capacitor (e.g., C1) causes a voltage (see Vo or Vout) at an output electrode of the mimic capacitor (C_ {int}) fluctuate proportionally to the voltage fluctuation at an output electrode (8) of the first sensor capacitor (e.g., C1), even if there is no rain present in a field of the mimic capacitor (C_ {int}); and in the that rain is detected based on an output signal (see Vo or Vout) of the output electrode of the mimic capacitor (C_ {int}), in which the output signal is read at least between one end of the write pulse (Clk_ {wr}) and a start of erase pulse (Clk_ {Er}) (see the "read" area in the Fig. 6).

Still in relation to Fig. 5, during erase cycle, the erase pulse Clk_ {Er} makes the capacitor (C1, C2, C3 and / or C4) and therefore also the capacitor imitator C_ {int} are discharged to ground (e.g., a potential fixed as V = 0) (see conventional ground symbol in Fig. 5). However, it has been discovered that a fixed land can carry to certain problems. In this way, during the erase cycle the Clk_ {Er} erase pulse causes the capacitor (C1, C2, C3 and / or C4) and therefore also the imitating capacitor C_ {int} is download to a virtual land VG that is floating (see VG and the Earth symbol in Fig. 5). In other words, an electrode of each of the capacitors C1-C4 is floating. It can be at a floating or reference potential / voltage. It has been discovered that a floating or virtual land can be highly advantageous (e.g., a floating land and / or a) condenser electrode (s) can lead to a considerable reduction in EMI interference problems). By For example, such floating or virtual land can help reduce possibilities of the sensor system being distorted by EMI interference. In this regard, reference is made to Figs. 28 (a) and 28 (b) (together with Fig. 5).

In Figs. 28 (a) - (b), the numbers of reference 7 and 8 refer to the electrodes of a capacitor  (e.g., C1, C2, C3 or C4). In these figures, "q" does reference to the load and \ Phi refers to the potential (\ Phi1 is different from \ Phi2). In Fig. 28 (a) the capacitor (e.g., C1) is grounded to a fixed potential as 0 volts (the charge on the grounded electrode is fixed a + q). In this regard, when the charge on electrode 7 set to Earth is fixed at + q, when an external body E_ {B} is brought (e.g., the finger of a person with one more dielectric constant high) to a sensing or sensing zone of the condenser (e.g., touching the front surface of the windshield above the condenser) this external body induces a change in the load of - \ Deltaq and the another electrode 8 that is not fixed changes from a charge of -q to a load of -q + \ Deltaq in an attempt to balance the load. This way, if the capacitor was grounded to a fixed potential like 0 volts, and a capacitor output voltage will be read, it will would read load changes caused by a \ Deltaq that is not necessary, and this can lead to false readings. Comparing the Figs. 28 (a) and 28 (b), Fig. 28 (b) illustrates a advantage of having an electrode 7 of the sensor capacitor (e.g., C1-C4) is floating (e.g., to a floating land or virtual). In Fig. 28 (b), the charge q on electrode 7 does not Is fixed. E.g., electrode charge 7 changes from + q 'to + q' ' when the external body makes contact with the windshield in a sensing or detection zone, thus indicating the nature floating electrode. In Fig. 28 (b), when the body external (e.g., a person's finger) is applied to the windshield over the sensor or sensing zone of the charges free on both electrodes 7 and 8 of the capacitor change. This way, the adverse effect of Δq is eliminated or reduced using the VG floating or virtual ground (electrode 7 is floating). In concrete, when electrode 7 is floating as in Fig. 28 (b), the external body (E_ {B}) does not affect so Adverse to the sum of the load because adding the charges (+ q '' and -q '') of electrodes 7 and 8 when the external body is present gives a result of zero or practically zero. False readings due to EMI interference can also be reduced using this floating feature. In this way, the floating nature can allow the absolute values of the charges q in the capacitor electrodes 7 and 8 are the same or substantially equal even when the external body is present since the electrode 7 is floating and not grounded. This is a reason example of why it can be advantageous to make the electrodes 7 of the C1-C4 capacitors are floating, or are  posts to a virtual land VG as shown in Fig. 5. From this way, referring to Figs. 5 and 28, the C1-C4 sensor capacitors are floating and their two electrodes are isolated from the earth. Therefore, the sensor Rainfall comprises at least one sensor capacitor (C1, C3, C3 and / or C4) that is sensitive to moisture on an external surface of a window, including the sensor capacitor a first electrode of capacitor (8) that receives a charge signal and a second condenser electrode (7) separated from the first electrode of condenser (8); and in which the second condemner electrode (7) it is floating so that the sensor capacitor is isolated from the land.

Fig. 6 is an example timer diagram of the signals applied to or captured from the circuit of Fig. 4-5 during write / erase modes / cycles. As noted above, the capacitors (C1-C4) are charged, read, quantified and deleted sequentially. Fig. 6 shows a write clock (Clk_ {wr}) and erase (Clk_ {Er}) pulse for each capacitor C1-C4, in sequence. Then, the voltages are quantified and put in the output. The variable Vol-Vo4 output voltages correspond to capacitors C1-C4 respectively, and therefore C_ {int}. Note that the Vo1-Vo4 output signals in Fig. 6 are taken in V_ {out} (or Vo) in Figs. 4-5. In addition, in Fig. 6, the Vo output signals are read or analyzed (eg, for autocorrelation and / or cross correlation) at the peak of the reading zones (see "Read" in Fig. 6) of the output signals where the output signals are substantially stabilized and / or the saturated condenser. Specifically, the output signal V_ {out} (or Vo) in Fig. 6 for a specific capacitor is read in the "reading zone" after the end of the write pulse (Clk_ {wr}) for that capacitor , and before and / or until the start of the erase pulse (Clk_ {Er}) for that
condenser.

Still in reference to Fig. 6, for example, a drop of water on the outside surface of a windshield will affect the magnitude of the output signal (s) V_ {out} (or Vo). For example, a drop of water above the area of a given capacitor (e.g., C1) will cause the level of the output signal (s) V_ {out} (or Vo) for said capacitor in the "reading" zone of the signal is higher compared to a situation in which this drop is not present. The exact magnitude or level depends on the droplet size of Water. With incremental amounts of water, the magnitude of the signal in the "reading" zone it becomes higher because the dielectric constant of water is higher than that of glass and / or of air and this increases capacitance. By way of similar, if there is no water drop present on the windshield above the area of a given capacitor (e.g., C1) then this will cause the level of the output signal (s) V_ {out} (or Vo) for the capacitor in the "read" zone of the output signal is lower compared to a situation in that there is a drop present.

The signals of the capacitor (s) they can be converted from analog to digital through a scheme of sigma-delta modulation or similar, which can be implemented at the software level or in any other way suitable as through hardware. The principle behind a sigma-delta architecture is to make evaluations Stop the signal, measure the error, integrate it, and compensate for Then that mistake. The data can be oversampled to a given frequency of at least 32 kHz, p. eg, more preferably 64 kHz, although it will be appreciated that other ones can also be used sampling frequencies Quantification in progress can recover by modulation scheme sigma-delta to produce a simple binary output 0 or 1, corresponding to activated and deactivated, respectively, in this way, the modulation scheme sigma-delta can be used to reduce noise (e.g. eg, at the tail of a signal) and produce a digital output train (e.g., 1s and 0s).

Before analyzing the detailed operation of y example math behind a sensor algorithm For example, a summary of the states that can be provided take the sensor and / or the windshield wipers in connection with Fig. 7, which is an example state diagram that shows how autocorrelation and cross correlation data can be used to control vehicle windshield wipers. The system starts in a Start / Initialization Status S702. In this state, they empty All buffers. Based on the entries of the capacitors C 1, C 2, ..., C n, a analog-to-digital conversion of the signals of the respective inputs through modulation sigma-delta. Data for plurality is read of channels over a period of time T. The Selector State of Operation Mode S704 functions as a switch that Select between manual and automatic windshield wiper mode. If the S704 Operation Mode Selector Status indicates that select manual mode, then in Manual Mode Status S706 an automatic mode can be disabled and a pre-existing manual mode. Then the system returns to Start / Initialization Status S702. However, if the State Operation Mode Selector S704 indicates that the automatic mode, then the automatic mode of wiper blades in the S708 Automatic Mode Status.

In the S710 Autocorrelator Motor Status, it They carry out at least three calculations. First, it calculates a normalized autocorrelation for each signal input of the capacitive system. Second, the gradient is calculated of autocorrelation. Third, the difference between the signal input and an undisturbed signal of reference (Δ1). This information is passed to the State It's raining? S712, in which at least three are verified conditions to determine if it is likely to be raining, there moisture on the windshield, etc. Probable indications of rain are the autocorrelation gradient is greater than 1, than all autocorrelation values are positive, and / or that Δ1 is greater than a predefined threshold value t1. If not these conditions are met, the system moves to the Stop State Windshield Wiper / Stop Engine S714, in which the windshield wipers are they deactivate (if they are moving) or do not operate, and the motor will for (if it is running), and the system is returned to the State of Start / Initialization S702.

On the other hand, if all the conditions (e.g., there is likely to be a water interaction, moisture or some other disturbance in the glass, etc.), the system it moves to the State of Lower Speed S716, in which the engine Windshield wiper is activated at the lowest available speed. In The S718 Cross-Correlation Engine Status is calculates the cross correlation between the input signals of the capacitors The shape of the correlation curve is determined crossed, and the symmetry of the two sides of the curve of cross correlation. As will be described later, you are verifications help, for example, to determine the type of disturbance (e.g., light rain, heavy rain, fog, snow, etc.) that you are hitting the window (eg, windshield). At Rain Level Assessment Status S720, the "rain level" (eg, strong, light, etc.). Based on this determination, the wiper motor is activated to the adequate speed in the Speed Selector Status S722. By Lastly, the system is returned to the Start / Initialization Status S702 to determine whether or not there is any change in conditions external to the car.

The steps carried out by the sensor rain will be described in greater detail in connection with Fig. 8, which is an example flowchart that shows how autocorrelation and cross correlation data can be used to control the windshield wipers. In Fig. 8, in step S800 Buffers are emptied, and modulation is applied sigma-delta on the data obtained at circuit output from Fig. 4-5 (e.g., from C_ {int}, of capacitors C1-C4), and are read in S802

The algorithm to determine whether or not to put in windshield wipers, and if necessary, the speed at which start the windshield wipers, start by autocorrecting the data modulated by sigma-delta modulation in step S804. Autocorrelation can be used to analyze value series functions, such as time domain signals. An autocorrelation is the cross correlation of a signal with itself same. Autocorrelation is used to find patterns repetitive or practically repetitive in a signal like, for example, determine the presence of a hidden periodic signal low noise, identify the fundamental frequency of a signal that properly does not contain that frequency component but implies within it many harmonic frequencies, etc. The cross correlation is a measure of the similarity of two signals, and It is used to find characteristics in an unknown signal comparing it to a known one; in other words, it can be used to carry out the identification using the fingerprint of a signal. Cross correlation is a function of time relative between the signals. Cross correlation is applied on digital signals from any two capacitors (e.g., C1 and C2), in close spatial proximity, and the system searches for any degree of correlation in periods of time other than a period of zero time. This correlation space-time allows the system to extract patterns of how the falling rain projects itself electrically about the sensor system. As an example, the system can take the case of raindrops that move on a capacitor C1 in an instant t0 and the same drop that "touch" another capacitor C4 (spatially separated by a distance L of C1). If the drop is moves at an average speed of Vi, time (t0 + T), where T = L / Vi, The cross correlation function will have another end or fold. The standardized magnitude of this extreme value may allow the system determine the degree of rain that falls on the sensor.

Each C1-C4 capacitor has a autocorrelation function associated with the digitized Vout that results from the acquisition of data (or the corresponding data acquisition of C_ {int}). The autocorrelation function It depends on the temporary difference, instead of the time itself. Calculating autocorrelations is beneficial because it allows, by example, deduce the fundamental frequency regardless of the phase. Autocorrelations are advantageous over other methods, like Fourier transforms (which can also be used) that They provide information only about the underlying harmonics. In this way, the use of data autocorrelation purchased from capacitors C1-C4 (which as explained above, includes the corresponding data acquired from the C_ {int} bully) can be used to detect and distinguish drops of water, dirt, dust, water droplets; a downpour, etc.

It should be noted that this is considered that the C_ {int} data is from the capacitors C1-C4 because the C_ {int} capacitance mimics or substantially mimics C1-C4 capacitances as explained above. This way, when we talk about receiving data from capacitors (e.g., C1-C4), this covers and includes receiving data from the C_ {int} capacitance. In other words, the circuit output from Fig. 4-5 is one of the C1-C4 capacitors, even if not taken directly from them.

Rain, as a function of time, can represented by the following formula:

7

Essentially, b takes a binary value that Indicates whether it is raining (1) or not (0). It will be appreciated that b is at least two bits, and that for modulation Sigma-delta can be used 24 bits. You can also it is appreciated that a scale could be introduced, potentially for capture more data related to voltages in the C1-C4 (or C_ {int}) capacitors.

At the end of a sampling cycle L , for example, the circuit output of Fig. 4-5, p. eg, of the C1-C4 four capacitor system (or through C_ {int}), it goes from 0000 to 1111, using binary digital data. A single bit to one can initiate a single wiper action. In the case where all bits are at zero (0000) or all bits are at one (1111), then no action of the windshield wiper can be initiated, because there is probably nothing on the windshield, the car is completely submerged, etc., since all the capacitors in the array would be reading the same, which is not consistent with the fall of rain on a window. In this way, the most likely events in which the windshield wipers will be necessary are those that are in the range of 0001 to 1110 (that is, when the output of all the capacitors in the system is not the same). When the data is in this interval, or even if it is not in this interval, correlation functions (autocorrelation and / or cross-correlation functions) can be executed using the following integral. It will be appreciated that the integral indicated below can be rewritten in other ways such as, for example, a sum. The correlations between two drops over a long period of time can be calculated according to the following formula:

8

where R_ {b} is the correlation of a binary event, given as a function of the resistances r_ {i} in the moments of time t_ {i} ; and L is a long sampling period during which data is captured. The sampling period L may be approximately 10 to 100 ms, and more preferably approximately 20-30 ms, which corresponds approximately to the frequency at which a standard human eye can discern. R_ {b} is also equal to a function of the correlation of the changes in the resistances in the capacitors Δ \ bar {r} and the change in time. When \ Delta \ bar {r} = 0, the autocorrelation value is determined since the data of the same capacitor is being analyzed, and when \ Delta \ bar {r} \ neq 0, cross correlations are calculated since the correlation is carried out on data from different capacitors.

These functions are subject to several underlying restrictions and assumptions of example. In first place,

9

This restriction basically means that a Water drop or similar is moving at a given time scale. Secondly,

10

This restriction mimics or substantially mimics what happens when a few drops of water or the like move from a condenser to another. In this way, the correlation functions could be interpreted as discrete steps p in space and T in weather. This feature can be represented mathematically as The following equation:

eleven

Basically, the left part of the equation establishes a theoretical network in space and time through which a drop of water or similar moves. For example, Fig. 9 is a stylized example view of how a raindrop could Travel through a windshield. Fig. 9 shows a drop of water moving through a windshield in the plane X-Z for an initial period of time (t = 0) and certain amount of time later (t = T). The assumption that the Drop distribution is uniform in space and time allows  the creation of a binary field produced by the rain that is in a broad stationary sense. The system also assumes that the temporal correlation between the preferred pixels in it neighborhood is elevated in the direction of rain. Finally, the degree of autocorrelation and cross correlation over time quantify the fall of rain and other disturbances.

It will be appreciated that time can be saved from calculation due to the nature of the correlation matrices and to The nature of the fallen rain. For example, the matrices of Correlation can be symmetric. Also, as another example, because the rain tends to fall down from the sky and move up along a windshield, it can be enough to compare only capacitors that are arranged vertically relative to each other in cross correlation, at time the capacitors are ignored horizontally adjacent.

It should be noted that while using data binary, gray scale data can also be used with respect to the circuit outputs of Figs. 4-5, or other circuit (s) similar (s) or suitable (s).

Once autocorrelation has been executed in step S804 (e.g., using equation (s) previously analyzed (s), or some (s) other correlation equation (s) adequate (s)), one or more may be carried out checks to improve system accuracy. Examples of such checks (e.g., if the autocorrelated Rxx data they have negative values, if a gradient is greater than one, and / or if the shape of an Rxx curve is different or considerably different from that of an undisturbed autocorrelation data normalized stored in memory) are shown in the part bottom of the frame for step S804 in Fig. 8. They can One, two or all three checks are carried out.

For example, a check of the data of autocorrelation in step S806 can be to determine if the data autocorrelated of one or more of the capacitor (s) (C1, C2, C3 and / or C4; or through the C_ {int} imitator) comprise values negative For example, when autocorrelated data have negative value (s), then the system or method it can indicate that it is not raining, it can stop the windshield wipers, and / or may not operate the windshield wipers (see step S806). This check is to determine, for example, if a disturbance detected is rain. In this regard, the Fig. 10 is an example of a plot of maximum values of standard autocorrelations for different disturbances obtained experimentally. Fig. 10 illustrates that the signals of water are greater than the undisturbed and positive signals,  and that external interference like electromagnetic waves from CB radios and the human hand that is touching a window tend to be below the levels of non-disturbance and that may be negative In this way, to eliminate or reduce false detections due to external disturbances such as the human hand that is touching the window, signal interference radio, etc., any signal with negative values of Autocorrelation is considered as a "no rain" event. Negative autocorrelation values could be considered, or other measures could be taken to eliminate or reduce detections false due to external interference by, for example, gradient comparison (e.g., any lower or lower curve that the curve / non-disturbance plot of Fig. 10 can be considered as a "no rain" event, capacitors of shielded, etc.

A second sample check of the data of autocorrelation is to check if a gradient of a curve of autocorrelation associated with autocorrelated data is greater than one; and if not then the system or method may indicate that it is not raining, stop the windshield wipers and / or do not operate the vehicle windshield wiper (see step S806). In this check, the autocorrelation gradient is checked Normalized disturbance. The autocorrelation gradient normalized of an undisturbed signal is close to 1. Measure the gradient is beneficial because it is not affected by the temperature changes In this way, the rain sensor can be virtually immune to false readings due to changes in temperature in certain exemplary embodiments of this invention. Gradients less than 1 (or some other value default) can be considered as non-rain events.

A third example of checking data from autocorrelation is to determine if there is a match or a substantial coincidence between an associated autocorrelation curve with the autocorrelated data and one or more curve (s) of Default autocorrelation (s) stored in a database data and / or in memory. When the shape of the curve of autocorrelation associated with autocorrelated circuit data of Fig. 4-5 is different or substantially different with respect to the autocorrelation curve referring to data from a normalized undisturbed autocorrelation, this may considered as a non-rain event and it may be indicated that no it's raining, windshield wipers can stop, and / or it may not operate the windshield wipers (see step S808). But nevertheless, when there is a match or a substantial match between the autocorrelation curve associated with the autocorrelated data of the circuit of Fig. 4-5 and an autocorrelation curve default associated with humidity like rain, then you can indicate that it is raining, the windshield wipers can be operated  or keep moving them.

In this regard, the shape of the curve of autocorrelation can be used to reduce false actions of the windshield wipers and / or false detections. Specifically, the normalized autocorrelation of an undisturbed signal is used as reference. Then, the normalized autocorrelation of each signal captured from the circuit of Fig. 4-5 is compared to the reference to identify the closest fingerprint in Certain example cases. Generally, the more water there is present in the detection zone, the greater the difference between the reference signal and the observed signal. In this way, they can Compare correlation snapshots with snapshots of reference of well-known events such as the presence of rain, dirt, no disturbance, ice, etc. In general, the correlation snapshots may be normalized, although the invention is not limited to it. The correlation snapshots preferably plot r values versus amounts of time at over a discrete time interval.

When there is a match or a match substantial between the autocorrelation curve associated with the data autocorrelated circuit of Fig. 4-5 and a curve of default autocorrelation associated with a substance not wet as dirt, then this can be considered as a no rain event and it can be indicated that it is not raining, they can windshield wipers stop and / or they may not be activated (see step S808).

Thus, it will be appreciated that the shape of the autocorrelation curve resulting from the data output of the circuit of Fig. 4-5 (from capacitors C1-C4, or through C_ {int}) can be used to reduce false Wiper actions as a third condition. For example, a normalized autocorrelation curve of an undisturbed signal can be used as a reference. Then, the normalized autocorrelation of each signal captured from the circuit of Fig. 4-5 is compared to the reference to identify the nearest fingerprint. Generally, the more water is present in the detection zone, the greater the difference between the reference signal and the observed / detected signal. In this way, correlation snapshots can be compared with reference snapshots of well-known events. In general, correlation snapshots may be normalized. Correlation snapshots preferably plot r values versus amounts of time over a time interval
discreet.

A potential problem with rain sensors capacitive is that rapid temperature changes (e.g., due to the black radiation absorption frit used to cosmetically hide the sensor pattern) change the dielectric "constant" (permittivity) of the glass. So this is recorded as a capacitance change and can Misinterpreted as a rain signal. But nevertheless, a normalized autocorrelation function remains unchanged, or substantially unalterable, for different temperatures despite that there may be differences for the functions of Autocorrelation not standardized for different temperatures. In this way, the sensor system is not affected or is not seen. substantially affected by temperature changes.

In addition, the extremely slow accumulation of water like ultrafine mist can slowly accumulate up to a level that activates sensors based on converters Nyquist frequency. In the observation time that concerns the human eye (e.g., 30-60 Hz), the function of autocorrelation is able to distinguish between accumulation Ultra-slow dew or condensation and normal fog and rain.

Figs. 11A-11D provide correlation snapshots obtained experimentally from the sample. These correlation snapshots, or fingerprints of a event, can be stored as fingerprints or curves of reference correlation. Correlation snapshots observed / detected (e.g., autocorrelation curves) can compare to these reference fingerprints to determine the type of event that is occurring. For example, Fig. 11A it is an experimentally obtained autocorrelation snapshot Indicative of heavy rain. Fig. 11B is a snapshot of Autocorrelation obtained experimentally indicative of haze light Fig. 11C is an autocorrelation snapshot obtained experimentally indicative of CB radio interference. The Fig. 11D is an autocorrelation snapshot obtained experimentally indicative of a body with a voltage set to land. It will be appreciated that these fingerprints are provided as examples and reflect experimentally obtained data. The Actual events may differ in various characteristics. This way, when it is determined that there is a match or a substantial coincidence between the associated autocorrelation curve with the autocorrelated data of the circuit of Fig. 4-5 and a non-moisture autocorrelation curve default like the one in Fig. 11C or Fig. 11D, then this It can be considered as a non-rain event and can be indicated that it is not raining, you can stop the windshield wipers and / or they may not be activated (see step S808). But nevertheless, when it is determined that there is a match or a match substantial between the autocorrelation curve associated with the data autocorrelated circuit of Fig. 4-5 and a curve autocorrelation related to predetermined humidity such as Fig. 11A or Fig. 11B, then this can be considered as a rainy event and it can be indicated that it is raining, they can the windshield wipers are activated and / or the same. In addition to the default autocorrelation curves of Figs. 11A-11D, can be stored and / or compared other reference fingerprints with snapshots of correlation observed in other exemplary embodiments of this invention.

Returning to Fig. 8, in step S806, determine if each of the three conditions shown is met at the bottom of the frame of S804. Specifically, it is determined in S806 if each of the following is met: a) the data autocorrelated do not have negative data; b) a gradient of one autocorrelation curve associated with said autocorrelated data is greater than a default value as one; c) the shape of the autocorrelation curve associated with the autocorrelated data of the circuit of Fig. 4-5 is different from a curve of default autocorrelation associated with autocorrelation data not disturbed. If all conditions are not met, this is a indication of a non-rain event and the process moves to the step S808 in which the (the) stops vehicle windshield wipers (if moving) or maintained deactivated, and the initialization of S800 starts again. Without However, if all these requirements are met in S806, then the process moves to S810 and the windshield wipers are activated vehicle (e.g. windshield wipers) to your lower speed

Fig. 13 illustrates an example of autocorrelation. In Fig. 13, the values of (or corresponding) al) sensor capacitor C1 are, in sequential times -t2, -t1, t0, t1, t2 and t3 are 0, 0, 1, 1, 0 and 0 respectively. The autocorrelation for the instant 0 (aco) is determined by multiplying the values corresponding to C1 in an outdated manner, and adding or adding the results below. It can be seen in the Fig. 13 that aco is equal to 2 in this case. In this way, in the autocorrelation plot at the bottom of Fig. 13, is produces an entry in the graph at time 0 for a value of autocorrelation of 2. It should be noted that the graph of autocorrelation at the bottom of Fig. 13 is similar, although simpler than the autocorrelation graph of Fig. 10 and autocorrelation values can be obtained for Fig. 10 of a similar way. Then, still in relation to Fig. 13, an autocorrelation is carried out using the values of capacitance corresponding to C1 for the next point in the time to obtain the autocorrelation value ac1. This next autocorrelation value (ac1) is obtained by moving the sequence of lower row values for C1 with respect to the row top as shown in Fig. 13, and multiplying to then the values in the rows that form the same line and Adding the results. Fig. 13 illustrates that acl is equal to 1 for time 1. In this way, this autocorrelation value of 1 for time t1 can be entered in the graph in the part bottom of Fig. 13 and a line is drawn between the two points of data entered for purposes of example and understanding. He, for the next value (or period) of time, it runs again the lower row to another segment higher than the row superior and the process is repeated, and so on. It may look that the autocorrelation paths in Fig. 10 can be obtained similarly. In Fig. 13, it can be seen that it can be cross correlation is performed replacing the values corresponding to C1 in the bottom row with values of or corresponding to another capacitor like C2 (or C3 or C4).

Examine an autocorrelation and / or correlation crusade can also help distinguish between, for example, a Light rain or heavy rain. For example, if only the autocorrelation in time is high (and cross correlation is low), then there is probably only a light rain. The Fig. 12A is an example correlation matrix that shows rain light Note in Fig. 12A is that the correlations between C1 and C1, C2, and C2, C3 and C3, and C4 and C4 (these are autocorrelations) at over a given period of time they are high, while the rest of correlations (cross correlations) are low. Based on hypotheses and experimental data confirmed, a matrix of this guy would indicate a light rain.

On the other hand, if both autocorrelation and the cross correlation in time between the signals of the Capacitors are high, there is probably heavy rain. Fig. 12B is an example correlation matrix that shows rain strong. In Fig. 12B, not only are the autocorrelations of high individual capacitors (i.e. autocorrelations are the correlations between C1 and C1, C2 and C2, C3 and C3, and C4 and C4), the autocorrelations between the different capacitors are also generally high (correlations in Fig. 12B that go diagonally from the upper left to the bottom right are the autocorrelations, and the rest are cross correlations). Based on hypotheses and data Experimental confirmed, such a matrix would indicate a strong rain. The degree of cross correlation can be quantified to determine the relative speed of the rain. These dates they can, in turn, be used to activate various speeds of windshield wipers, as appropriate for the speed of the rain. For example, the more high cross correlations there are, higher windshield wiper speed to use.

More systematically, in step S812, it calculate cross correlations (correlations between data corresponding to different capacitors), and both are used sides of the cross correlation curve to determine a level of symmetry L. If the level of symmetry is below a threshold predefined t_ {min}, step S814 directs the system towards the step S816 in which the wipers are activated at speed lower, and the system is returned to the initialization stage S800 If the level of symmetry is greater than t_ {min} but less than an arbitrary value t, step S818 directs the system to the stage S820 in which the wipers are activated at a speed higher or average, and the system is returned to the stage of S800 initialization. It will be appreciated that a plurality of arbitrary values t_ {i}, and a level of symmetry between t_ {i} and t_ {i + 1} will activate a speed of appropriate windshield wiper and then return the system to the initialization stage S800. Finally, in the step S822, if the level of symmetry is above a level predefined t_ {max}, step S822 directs the system towards the step S824 in which the wipers are activated at a higher speed, and the system is returned to the stage of S800 initialization. In this way, the correlations of the data outputs of the circuit of Fig. 4-5 can used to adjust the windshield wiper speed. How many more High autocorrelations are there, the higher the speed of windshield wiper to use due to the likelihood of more rain strong.

Figs. 12-24 illustrate ones examples of cross correlations carried out Fig. 14 sample cross correlation data, while Figs. 15-24 illustrate cross correlation graphs of certain of the data in Fig. 14 in which it is detected rain. In Figs. 15-24, each period on the axis horizontal is a microsecond (1 \ mus) for example purposes, and the Sampling was carried out every microsecond. As explained above with respect to Fig. 13, in Figs. 15-24 in time = 0 (period 0), there is no time shift of the values of the different capacitors that are being correlated. Fig. 14 illustrates that when rain is present (see signs S1-S5 and W1-W5), delta signals corresponding to autocorrelation were high. Figs. 15-24 are plotted of cross correlations corresponding to these signals. Help look for symmetries among traces of the left part and the right part of each of Figs. 15-24 (a side of zero is compared to other side of zero). Usually, if there is a symmetry around the zero period axis, there is not much cross correlation what indicates that the rain detected is not very strong. However, if there is an asymmetry around the zero period axis, then this means more cross correlation and indicates that the rain is strong or stronger. For example, note the asymmetry in Figs. 18, 19 and 23 around the zero period axis due to the peaks or valleys in one or both sides. More cross correlation indicates that the drops of rain are moving from a detection zone of a capacitor to a detection zone of another capacitor. To this respect, every interaction of a raindrop and the surface of a windshield has its own correlation signature in the domain temporary. A high cross correlation indicates that the same drop is being detected by different capacitors, at different points in time (eg, see also Fig. 9). It should be noted that the lowercase "t" in Fig. 9 represents the same as the axis of periods in Figs. 15-24.

In this way, it will be appreciated that a sensor of humidity (e.g., a rain sensor) can detect rain in the vehicle window without the need for a capacitor reference. The correlation can be used temporal space. All capacitors, or one plurality of capacitors, in the sensor system they can have a identical or substantially identical form in certain forms of example embodiment. For example purposes, at a given point in time (e.g., t1), the system can compare values corresponding to C1 with values corresponding to C2, and / or values corresponding to another capacitor. For this time t1 the system can also compare values corresponding to C1 with itself (autocorrelation), and you can also compare the autocorrelation for C1 with autocorrelation for C2 and / or for other capacitor (s) sensor (s).

Claims (10)

1. A rain sensor for installation with a vehicle window comprising:

a circuit sensor comprising at least a first sensor capacitor (C1, C2, C3, C4) adapted to be supported by a vehicle window, being the first moisture sensitive sensor capacitor in a external surface to said window in conditions of installation;

having the first capacitor sensor separate capacitor electrodes first and second (7, 8) that are substantially coplanar; Y

in which at least part of the first sensor capacitor has a fractal geometry, characterized in that the fractal geometry is selected from the group consisting of a Hilbert fractal and a Cantor fractal. 2. The rain sensor of claim 1, in which the fractal geometry is such that the first capacitor sensor (C1, C2, C3, C4) works as your own Faraday screen or quasi-screen of Faraday to reduce the adverse effects of EMI interference. 3. The rain sensor of claim 1, wherein the first sensor capacitor (C1, C2, C3, C4) comprises a fractal geometry so that the lateral flow caused by the fractal geometry allows the condenser to be sensitive to moisture on the external surface of the window that is not located directly on the first sensor capacitor. 4. The rain sensor of claim 1, in which the window is one of the windshield of the vehicle, the rear window of the vehicle, and / or the sunroof of the vehicle. 5. The rain sensor of claim 1, in which the rain sensor comprises at least about first and second sensor capacitors (C1, C2, C3, C4) of about the same size that are sensitive to moisture in the external surface of the window, and in which each of the first and second sensor capacitors comprises a geometry fractal 6. The rain sensor of claim 1, in which the rain sensor includes a plurality of sensor capacitors (C1, C2, C3, C4) that have a geometry fractal, in which the plurality of sensor capacitors are they have in a system around a contact plate (28) centrally located 7. The rain sensor of claim 1, in which the overall length of the first sensor capacitor (C1, C2, C3, C4) is about 25 to 200 mm, more preferably of approximately 30 to 90 mm. 8. The rain sensor of claim 1, which additionally comprises means to autocorrelate data corresponding to and / or the sensor capacitor to obtain data autocorrelated, and means to determine based on so less such autocorrelated data if there is moisture on the surface External window. 9. The rain sensor of claim 1, wherein the at least one sensor capacitor (C1, C2, C3, C4) is part of a sensor circuit, comprising the sensor circuit additionally at least one imitator capacitor (C_ {int}) that imitates at least charging and / or discharge the first capacitor sensor, in which a write pulse causes it to charge so minus the first sensor capacitor and a clear pulse causes each first sensor capacitor and imitator capacitor are discharged substantially; in which presence of rain on the external surface of the window in a sensor field of the first Sensor capacitor (C1, C2, C3, C4) causes a voltage in a output electrode of the imitator capacitor fluctuate in one way proportional to the voltage fluctuation in an output electrode of the first sensor capacitor, even though there is no rain present in an imitator capacitor field; Y in which rain is detected based on a signal output of the imitation capacitor output electrode, in the that the output signal is read at least between an end of the writing pulse and a start of the erase pulse. 10. The rain sensor of claim 1, which additionally comprises at least one correlation engine that (a) autocorre information of and / or corresponding to the sensor capacitor to determine whether or not there is rain in the outer surface of the window, and / or (b) performs cross correlations of information of and / or corresponding to sensor capacitor to determine at what speed to operate so minus a vehicle windshield wiper and / or an amount of rain on the outer surface of the window.