Environmental sensor with resonator for detecting sensor degradation

Abstract

Method for detecting an impairment of an environment sensor (10) by means of a ring-shaped resonator (1) arranged in the direction of radiation of the environment sensor (10), comprising the steps: - setting a resonance frequency on the resonator (1), - determining a damping and / or shift of the resonance frequency, and - determining the impairment of the environment sensor (10) from the determined damping and shift.

Description

The invention relates to an environmental sensor with a resonator which is configured to detect moisture that impairs the environmental sensor. State of the art EP 2 251 679 A1 discloses a device and a method for measuring the moisture content of a product using different resonance frequencies of a ring resonator. A frequency below the relaxation frequency of water, for example the SM 2.4 GHz band, is suitable for exciting the ring resonator. Environmental detection systems, particularly those using radar, are known, for example, from DE 10 2010 006 214 A1 and are used for emergency braking of a vehicle. These systems must therefore be highly reliable to prevent false braking. Furthermore, DE 10 2005 039 851 A1 discloses a humidity sensor for detecting water droplets on a vehicle surface. In addition, DE 10 2012 220 311 A1 discloses a generic method for detecting sensor degradation in distance sensors. Task and solution The object of the invention is to provide a device and a method by which the influence of moisture on an environmental sensor can be determined. The problem is solved by a method and a device according to the independent claims. Further advantageous embodiments of the invention are the subject of the dependent claims. According to the invention, a method for detecting an impairment of an environmental sensor by means of a resonator comprises the following steps: setting a resonance frequency on the resonator, determining a damping and / or shift of the resonance frequency, wherein the impairment of the environmental sensor is determined from the determined damping and shift. Impairment of the environmental sensor can be caused by dirt or moisture. Moisture can lead to a shift and / or damping of the resonant frequency at the resonator. This shift is a measure of the moisture content at the resonator. The effect on the environmental sensor can therefore be determined from the shift and / or damping of the resonant frequency. Advantageously, the resonator can detect moisture, which protects against misinterpretations of the measurement results from the environmental sensor. The environmental sensor could be, for example, a radar sensor, a camera sensor, or an ultrasonic sensor. Preferably, in the case of a radar sensor, the existing RF components of the radar sensor could be used. According to the invention, the resonator is ring-shaped. Advantageously, a ring-shaped resonator can determine the moisture content more accurately, since the ring-shaped resonator is less affected by radiation losses than a strip-shaped resonator. Preferably, the method can control a large number of resonators. The control can be performed alternately, or the individual resonators can be controlled in any sequence. This allows for the advantageous use of multiple resonators, enabling a more precise determination of moisture levels and thus also of the influence on the environmental sensor. Preferably, the impairment can be determined from the measured damping and / or displacement using a parameter list. This parameter list can be stored in the environmental sensor, thus enabling the correlation of the moisture, determined from the displacement and / or damping of the resonance frequency, with a degree of influence on the environmental sensor. Advantageously, this allows any impairment of the environmental sensor to be determined directly from the parameter list based on the calculated shift and / or damping of the resonance frequency. In a further embodiment of the invention, the parameter list can be determined experimentally. The degree of influence on the environmental sensor is determined as a function of the humidity measured by the resonator. Advantageously, this parameter list allows for a particularly precise determination of the influence on the environmental sensor as a function of the frequency shift and / or damping of the resonator. According to the invention, an environment sensor in a vehicle comprises a ring resonator which is configured to detect an impairment of the environment sensor by being able to adjust a resonance frequency on the ring resonator, by being able to determine a damping and / or shift of the resonance frequency, and by being able to determine the impairment of the environment sensor from the determined damping and shift. Furthermore, the resonator is arranged in the direction of radiation from the environmental sensor. Advantageously, this allows the influence on the environmental sensor to be determined where the greatest influence is expected. Preferably, the resonator can be part of a housing surrounding the environmental sensor. This allows the resonator to be taken into account advantageously during the manufacturing of the housing. In a further embodiment, at least one resonator can be arranged on or in a wall of the housing. This advantageously protects the resonator from environmental influences. Preferably, the ring resonator has a distance of less than 2 cm to an outer surface of a wall of the housing. In this way, the effectiveness of the resonator can be further improved to its advantage. Character description Fig. 1 shows the construction of a ring resonator according to the prior art. Fig. 2 shows the frequency shift of a ring resonator according to the prior art. Fig. 3 shows a housing for an environmental sensing system on which a ring resonator is arranged. Fig. 4 shows a housing for an environmental sensing system with a ring resonator integrated into the housing. Fig. 5 shows a housing for an environmental sensing system with four ring resonators arranged on the housing. Fig. 6 shows a housing for an environmental sensing system with four ring resonators integrated into the housing. The well-known ring resonator 1 in Fig. 1 has a microstrip conductor 3 that forms a closed circuit. The microstrip conductor 3 can be coupled to an RF line via two contacts 5, allowing excitation of the microstrip conductor 3. Figure 2 shows the known influence on the resonance frequency 23, 33 of a ring resonator 1. The frequency response of an air measurement 21 is shown as a dashed line and differs from the frequency response of a measurement of moist material 31. The bandwidth 25 of an air measurement 21 is smaller than the bandwidth 35 of a measurement of moist material 31. In contrast, the amplitude of the resonance frequency 23 of the air measurement 32 is larger than the amplitude of the resonance frequency 33 of a measurement of moist material 31. Moisture causes a shift in the resonant frequency towards lower frequencies and a damping of the amplitude. This behavior of the ring resonator is used to determine the moisture content. In Fig. 3, the ring resonator 1 is formed by a microstrip line 3 on the surface 7 of a housing 9. The frequency response of the ring resonator changes due to moisture. The degree of moisture on the housing 9 can be determined from the damping and displacement. The influence of the moisture on the environmental sensor 10 can be determined from this degree and taken into account during the operation of the environmental sensor 10. The housing 9 in Fig. 4 has a microstrip line 3 located inside the housing 9, which forms a ring resonator 1. The ring resonator 3 is located in the direction of radiation from the environmental sensor 10. Fig. 5 shows a further embodiment of the invention. Four microstrip lines 3 are arranged on the surface 7 of a housing 9 with an environmental sensor 10 and form four ring resonators 1. In Fig. 6, the four microstrip lines 3 are arranged in a housing 9 above an environmental sensor 10.

Claims

Method for detecting an impairment of an environment sensor (10) by means of a ring-shaped resonator (1) arranged in the direction of radiation of the environment sensor (10), comprising the steps: - setting a resonance frequency on the resonator (1), - determining a damping and / or shift of the resonance frequency, and - determining the impairment of the environment sensor (10) from the determined damping and shift. Method according to claim 1, wherein a plurality of resonators (1) are alternately controlled. Method according to one of the preceding claims, wherein the impairment is determined from the determined damping or displacement by means of a parameter list. Method according to claim 3, wherein the parameter list was determined experimentally. Environment sensor (10) in a vehicle comprising: a ring-shaped resonator (1), wherein the resonator (1) is arranged in the direction of radiation of the environment sensor (10) and is configured to detect an impairment of the environment sensor (10) by being able to adjust a resonance frequency on the resonator (1), by being able to determine a damping and / or shift of the resonance frequency, and by being able to determine the impairment of the environment sensor (10) from the determined damping and shift. Environmental sensor (10) according to claim 5, wherein the resonator (1) is part of a housing (9) surrounding the environmental sensor (10). Environmental sensor (10) according to claim 6, wherein at least one resonator (1) is arranged on or in a wall (7) of the housing (9). Environmental sensor (10) according to one of claims 6 or 7, wherein the resonator (1) has a distance of less than 2 cm to an outer surface of a wall (7) of the housing (9).

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