WINDSHIELD MONITORING SYSTEM

Abstract

The present invention relates to a windshield monitoring system. The windshield monitoring system comprises; a windshield (114) and an emitter (122) arranged to emit a sound pulse to induce a surface acoustic wave (SAW) to a surface of the windshield (114). The windshield monitoring system also comprises a sensor (124) arranged to receive the surface acoustic wave from the windshield (114) and a detection module (130) arranged to detect the presence of surface contamination (120) by attenuation in intensity of the received wave compared to an expected wave.

Claims

1. A windshield monitoring system, comprising: an emitter configured to emit a sound pulse to induce a surface acoustic wave (SAW) on a surface of a windshield; a sensor configured to receive the SAW from the windshield; a waveguide to spread the surface acoustic wave across the windshield from the emitter to the sensor; and a detection module configured to detect the presence of surface contamination by intensity attenuation of the received wave compared to an expected wave.

2. (canceled)

3. The system of claim 1, wherein the waveguide comprises a source reflector and a sink reflector, wherein the source reflector is configured to direct the SAW away from the emitter and progressively reflect the SAW, along the length thereof, across the windshield to the sink reflector, wherein the sink reflector is configured to reflect any received waveform to the sensor, and wherein the source and sink reflectors are formed as substantially parallel elongate strips along opposing edges of the windshield.

4. The system of claim 3, further comprising a locating module configured to locate a position of the contamination by the time of attenuation on the received SAW.

5. The system of claim 3, wherein the reflectors comprise surface etchings on the surface of the windshield.

6. The system of claim 1, wherein the emitter and sensor are provided on a same side of the windshield.

7. The system of claim 1, further comprising an identification module configured to identify a type of contamination by characteristics of the intensity attenuation of the received surface acoustic wave.

8. The system of claim 4, wherein the emitter, the sensor and the waveguide form a primary SAW system, wherein the windshield monitoring system comprises a secondary SAW system, and wherein the secondary SAW system is a substantially orthogonal duplicate of the primary SAW system to provide 2-dimensional surface contamination detection.

9. The system of claim 1, wherein the windshield is a front windscreen of a vehicle, a rear windscreen of a vehicle, or a side window of a vehicle.

10. The system of claim 1, wherein the contamination is selected from the list of moisture, liquid water, and ice.

11. A windshield clearing system, comprising: the windshield monitoring system of claim 1; and a windshield clearing element configured to clear at least part of the windshield in response to detecting the presence of surface contamination.

12. The windshield clearing system of claim 11, wherein the windshield clearing element comprises a heating mechanism.

13. The windshield clearing system of claim 12, wherein the heating mechanism comprises a plurality of heating elements, wherein, in response to locating surface contamination, a heating element corresponding to a location of contamination is heated.

14. The windshield clearing system of claim 13, wherein the heating element is a resistance heating element.

15. The windshield clearing system of claim 14, wherein the resistance heating element comprises a conductive layer made from a metallic material.

16. The windshield clearing system of claim 12, further comprising a termination module configured to terminate heating in response to the windshield monitoring system ceasing to detect contamination.

17. A vehicle comprising the windshield clearing system of claim 11.

18. A method of monitoring a windshield, the method comprising; emitting a sound pulse to induce a surface acoustic wave (SAW) to a surface of the windshield; transmitting the SAW along an edge of the windshield; progressively reflecting the SAW to an opposing edge of the windshield; reflecting the SAW along the opposing edge of the windshield to a detector; detecting a presence of surface contamination by attenuation in intensity of the received SAW; and locating the surface contamination by a time coordinate of the attenuation on the SAW signal.

19. (canceled)

20. The method of claim 18, further comprising; emitting a secondary sound pulse to induce a secondary SAW to the surface of the windshield, the secondary sound pulse transmitting across the windshield to a detector in a direction substantially orthogonal to the first SAW; and locating a position of the surface contamination in 2 dimensional co-ordinates.

21. A method of clearing a windshield, the method comprising; determining a presence of surface contamination using the method of claim 18; and heating at least part of the windshield in response to detecting surface contamination.

22. The method of claim 21, wherein the heating comprises: dividing the windshield into separate zones to be heated; and heating a zone of the windshield corresponding to a location of the surface contamination.

23-24. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0056] FIG. 1A shows a moisture detection system as known from the prior art;

[0057] FIG. 1B shows a similar view to FIG. 1A;

[0058] FIG. 2 shows part of a windshield monitoring system according to an aspect of the present invention;

[0059] FIG. 3 shows a block diagram of the windshield monitoring system from FIG. 2;

[0060] FIG. 4 shows a windshield clearing system according to a further aspect of the present invention;

[0061] FIG. 5 shows a surface acoustic wave (SAW) detected using the windshield monitoring system of FIG. 2; and

[0062] FIG. 6 shows a similar view to FIG. 5 of the SAW detecting surface contamination.

DETAILED DESCRIPTION

[0063] With reference to FIG. 2, a vehicle 110 includes a vehicle frame 112 supporting at least one windshield 114. The vehicle 110 also includes a windshield monitoring system part of which is shown in FIG. 2 with FIG. 3 showing a more detailed version in the form of a block diagram.

[0064] The term windshield is used to cover a front windscreen, or a rear windscreen or a side window, of which there are several. Each windshield 114 is fabricated from laminated glass, or may alternatively be fabricated from a single sheet of glass. Each windshield is supported by various parts of the car frame 112. The windshields 114 serve various functions such as segregating an exterior environment from an interior environment of the vehicle 110. In addition, the windshields 114 allow for visibility between the interior and exterior environments.

[0065] The windshield monitoring system includes a primary surface acoustic wave (SAW) system 116 and a secondary SAW system 118, as will be described in more detail below.

[0066] The primary SAW system 116 is used to detect a vertical position of contamination 120 and the secondary SAW system 118 is used to detect a horizontal position of contamination 120. The secondary SAW system is a substantially orthogonal duplicate of the primary SAW system. The primary and secondary SAW systems allow for two-dimensional detection when used in combination.

[0067] Both the primary and secondary SAW systems 116, 118, include an emitter 122, a sensor 124, and a waveguide.

[0068] The emitters 122 and the sensors 124 are both transducers arranged to transmit and receive a surface acoustic wave (SAW) respectively. The transducers use piezoelectric crystals to convert sound energy to electrical energy and vice versa. These transducers are formed from two inter-lockable comb shaped metallic coatings applied to a piezoelectric substrate such as quartz.

[0069] The emitter 122 and sensor 124 of each SAW system 116, 118, are provided on the same side of the windshield 114 as each other. In this case, the primary SAW system 116 has the emitter 122 and sensor 124 located on a left side edge of the windshield 114. The secondary SAW system 118 has a sensor 124 and an emitter 122 located on a lower horizontal edge of the windshield 114. As will be described in more detail below, the emitter 122 and sensor 124 located on the same side of the windshield 114 results in an expected wave form sensed by the sensor 124 to be in the form of a continuum.

[0070] The waveguide spreads the SAW across the windshield 114 from the respective emitter 122 to the sensor 124. Each waveguide has a source reflector 126 and a sink reflector 128. The source reflector 126 is formed as an elongate strip on the same side of the windshield as the emitter 122. The sink reflector 128 is provided on the opposing edge of the windshield 114 in line with the sensor 124. The source and sink reflectors thus form substantially parallel elongate strips along opposing edges of the windshield. The reflectors are formed as surface etchings on a surface of the windshield 114. It is possible to provide these surface etchings on either surface of the windshield 114. If rain or ice detection is required, the etchings should be provided on an exterior surface of the windshield 114. If contamination is required on the interior surface, the surface etchings should be provided on an interior surface of the windshield 114.

[0071] The source reflector 126 directs the SAW from the emitter 122, along the windshield to the opposing edge. The surface etchings of the reflector guide the SAW substantially transverse to its originating direction so as to progressively propagate across the windshield 114. The transverse reflection of the SAW is thus reflected across the windshield 114 to the sink reflector 128. As will be described in more detail below, any contamination 120 causes attenuation in intensity of the SAW reaching the sink reflector 128.

[0072] The sink reflector 128 is also arranged to reflect any received wave form from the sink reflector 126 transversely towards the sensor 124.

[0073] With reference to FIG. 3, the windshield monitoring system includes the emitter 122 arranged to emit a sound pulse to induce a surface acoustic wave (SAW) on a surface of the windshield 114, and a sensor 124 arranged to receive the SAW from the windshield 114. The windshield monitoring system also includes a detection module 130. The expected wave form will always be constant in the absence of any contamination on the windshield. The detection module 130 thus detects the presence of surface contamination by a change in intensity of the received wave compared to the expected wave form. In particular, surface contamination is characterised by attenuation in intensity compared to the expected wave form.

[0074] The windshield monitoring system also includes a locating module 134 arranged to receive an output from the detection module 130. The locating module has a timer function. Any contamination detected by the detection module 130 is provided with a coordinate by the locating module based on the time at which the contamination has occurred on the received wave form.

[0075] The windshield monitoring system also includes an identification module 136. The type of contamination can be determined based on the shape or characteristics of attenuation intensity of the received SAW. The identification module 136 has a look-up table detailing various expected contamination types and their corresponding attenuation shape. The identification module 136 compares the received signal to the characteristics provided in the look-up table to determine the type of contamination on the windshield 114.

[0076] With reference to FIG. 4, the vehicle also includes a windshield clearing system 140. The windshield clearing system includes the windshield monitoring system, a control module 142 and a heating mechanism 144.

[0077] The control module 142 is arranged to pass a voltage across the heating mechanism 144. The control module 142 like the other aforementioned modules, is provided as electronic data on a non-volatile memory component of an on board computer system. The computer system also has a processor arranged to execute the electronic data of the various modules during operation.

[0078] The heating mechanism 144 comprises a plurality of heating elements, these heating elements are divided into two categories; active heating elements 146 and passive heating elements 148. Each active heating element 146 is a resistance heating element including a conductive layer, made from a metallic layer. The metallic layer may be a silver based alloy. Of course, other conductive or resistive materials would suffice as a conductive layer. Those other materials may include organic materials such as graphene. The metallic layer is vapour deposited on to the windshield to form a plurality of the active heating elements 146. The active heating elements 146 are separated from adjacent active heating elements by passive heating elements 148. Passive heating elements 148 are formed by areas of clear glass not having a metallic layer deposited thereon. These uncoated areas are relatively narrow so as to prevent a pattern of unclear windshield. The passive heating elements 148 thus electrically insulate adjacent active heating elements 146. Each of the active heating elements 146 can have a voltage passed across it to specifically heat that heating element. By the provision of the active and passive heating elements, it will be appreciated that the windshield is divided into a plurality of independently controllable heating zones.

[0079] The windshield clearing system also comprises a termination module 150. The termination module 150 is again provided as electronic data by the other aforementioned modules. The termination module 150 is arranged to terminate heating of the heating mechanism 144 in response to the windshield monitoring system ceasing to detect windshield contamination.

[0080] With further reference to FIG. 2, in operation, each emitter 122 emits a sound pulse into the respective source reflector 126. The source reflector 126 reflects the respective SAW transversely across the windshield 114. The SAW is propagated across the windshield 114 for the length of the reflector 126. The sink reflector 128 receives the surface acoustic wave progressively along its length. In response to receiving the SAW, the sink reflector 128 transversely reflects the SAW to the sensor 124.

[0081] With reference to FIG. 5, the intensity of the received signal is shown over time. Over the time period for one sound pulse it can be seen that the intensity naturally drops. This drop in intensity is proportional to the distance which the SAW travels whilst being progressively transmitted across the length of the windshield.

[0082] With further reference to FIG. 2, areas of contamination 120 can exist on a surface of the windshield 114. This system particularly lends itself to detecting water based contamination such as ice, moisture, and liquid water. This is because water based contaminants absorb energy from the SAW more effectively than the windshield and surrounding structures.

[0083] With reference to FIG. 6, the drop in intensity caused by the contamination 120 can be seen as a parabola. Other shapes of attenuation and attenuation over a longer time period signifies different contamination type and area of coverage respectively.

[0084] With reference to FIG. 3, the detecting module 130 detects the contamination after comparing the expected wave form to the actual received wave form. The locating module 134 locates the contamination in two dimensions according to the time and duration of the attenuated signal on each wave form received by the respective sensor 124 of each of the primary and secondary SAW systems. In addition, the type of contamination, characterised by the shape of attenuation, is determined by the identification module 136 by comparing the attenuated portion of the signal with the look-up. The location and identification data is then passed to the control module of the windshield clearing system 140 (FIG. 4).

[0085] With reference to FIG. 4, the control module 142 uses the location of contamination to determine which active heating element 146 should be heated. The specified heating element 146 is heated by applying a voltage to the metallic layer forming the resistant heating mechanism 144. The other active heating elements 146 remain unheated.

[0086] In parallel to heating the windshield, the windshield monitoring system (FIG. 3) continues to monitor the windshield 114 to monitor the already detected contamination as well as any new contamination. Once the contamination 120 has cleared up, the termination module 150 configures the voltage passed across the previously heated element 146 to be zero Volts so as to terminate heating.

[0087] The aforementioned systems provide for numerous energy efficiencies. The surface acoustic wave may detect contamination early since SAWs are thought to be attenuated by water and are thus detectable. In addition, segmenting the windscreen and heating only the heating element where contamination has been detected is more energy efficient than heating the entire windshield.