Measuring system for a motor vehicle

Abstract

Measuring system (200) for a motor vehicle (100), the measuring system (200) comprising the following elements: an optical fiber (220) with a first and a second end; wherein a fiber Bragg grating (225) is inscribed in the optical fiber (220) in a predetermined sensor section (225) between the first and the second end; wherein the fiber (220) in the sensor section (225) is configured to be attached to a rim (115) for the motor vehicle (100); a light source (210) configured to couple light into the first end of the fiber (220); a spectrometer (215) configured to determine a wavelength of light exiting the second end; and a processing device (205) configured to determine a deformation of the rim (115) in the region of the fiber Bragg grating (225) based on the determined wavelength.

Description

The present invention relates to a measurement system for a motor vehicle. In particular, the invention relates to a measurement system for determining a deformation of a wheel on a motor vehicle.A motor vehicle is supported with a wheel relative to a roadway. During operation of the motor vehicle, the wheel is exposed to static and dynamic forces, which can have an influence on a driving state of the motor vehicle. To determine such a force, a sensor may be attached to the wheel. However, existing sensor technology is often complicated and heavy, so that a sensor can be dynamically loaded due to its own mass. Moreover, usually only a single measured value can be determined by means of a conventional sensor, so that forces acting on the wheel cannot be determined comprehensively.DE 10 2021 114 425 A1 shows a measurement gearset. JP 2006-349645 A discloses a force measuring device for a wheel component.It is an object of the present invention to provide an improved technique for determining a force acting on a wheel of a motor vehicle. The invention achieves this object by means of the subject matter of the independent claims. Dependent claims represent preferred embodiments.According to a first aspect of the present invention, a measurement system for a motor vehicle following element comprises: an optical fiber having a first and a second end; wherein in a predetermined sensor section between the first and the second end a fiber Bragg grating is written into the optical fiber; wherein the fiber in the sensor section is configured to be attached to a rim for the motor vehicle on a periphery of the rim; a light source configured to couple light into the first end of the fiber; a spectrometer configured to determine a wavelength of light exiting from the second end; and a processing device configured to determine a deformation of the rim in the region of the fiber Bragg grating on the basis of the determined wavelength.The measuring system can allow an improved determination of a deformation of the rim. On this basis, forces acting on the rim can be determined. An operating or boundary region of the rim can be monitored in an improved manner in this way. The rim can be part of a wheel of the motor vehicle. A certain deformation or a certain force can enable valuable findings in particular for the development of the motor vehicle or of a wheel with the rim. The motor vehicle can also be controlled as a function of such a force. For example, a wheel load or an axle load of the motor vehicle on an axle can be determined with the wheel. If a predetermined wheel or axle load is exceeded, a corresponding warning can be provided. Overloading of the rim, of the wheel or of the motor vehicle can thus be prevented.The fiber Bragg grating is preferably tuned to reflect light of a predetermined wavelength and transmit light of other wavelengths. For this purpose, a series of defects can be introduced into the fiber, which are situated at predetermined distances along the fiber. A defect can be introduced by briefly melting a fiber material, for example by means of a laser or a superposition of a plurality of lasers. The predetermined wavelength can be impressed by appropriately selecting the spacings of the impurities. Fiber Bragg gratings operate as optical interference filters, in particular as a bandstop filter. A wavelength of light which is reflected has a certain, advantageously narrow bandwidth around the predetermined wavelength.The predetermined wavelength is preferably dependent on a deformation of the fiber in the sensor section. A mechanical load on the fiber can change the predetermined wavelength, so that the load can also be deduced inversely on the basis of the wavelength. Other influences on the predetermined wavelength, for example a temperature or a pressure, can be reduced or eliminated by means of customary measurement methods.A plurality of sensor sections with fiber Bragg gratings can be provided on a fiber, wherein predetermined wavelengths of the Bragg fiber gratings of different sensor sections of the fiber are preferably spaced apart from one another by a predetermined minimum. The minimum dimension is usually dependent on ranges of change of the predetermined wavelengths of the sensor sections under an expected deformation. In particular, predetermined wavelengths of two fiber Bragg gratings can be spaced apart from one another to such an extent that a maximum expansion of the one grating with simultaneous maximum compression of the other grating-within the scope of a predetermined measurement range-still allows a clear assignment of missing components in the spectrum to sensor sections. In particular, the wavelengths can be spaced apart from one another to such an extent that regions in which the wavelengths can lie under expected loads are disjunct to one another.In this way, a single fiber can be used to make multiple measurements on the rim simultaneously. As a result, complex processes on the rim, for example during dynamic operation when different forces are superimposed on the rim, can also be absorbed in an improved manner. The fiber can be light and inexpensive and easily attached to the rim. A function or a handling capability of the rim, for example when releasing or mounting a tire, cannot be adversely affected by the measurement system. The measurement system can be simple, robust and cost-effective. In addition, joint influences on different sensor sections, for example due to pressure or temperature, can be compensated by a suitable sensor configuration. For example, a differential measurement can greatly reduce or eliminate interference effects (common mode errors) acting in the same way on different sensors.In a further embodiment, the measurement system comprises a further fiber having a sensor portion configured to be attached to the rim. For this purpose, a plurality of light sources and / or a plurality of spectrometers can be provided in order to determine optical properties of the fibers. Preferably, however, the light source and / or the spectrometer are configured to determine optical absorption properties of the fibers in succession. Such measurement on different fibers in succession, usually in a cyclical sequence, is known as a multiplex method.In one variant, only one light source is used for simultaneously illuminating all fibers, while the spectrometer selectively analyzes light from the light sources one after the other. In a preferred variant, conversely, a plurality of light sources can be controlled in each case to illuminate only one of the fibers, and the spectrometer is connected to a plurality of fibers. This variant can be implemented particularly simply and cost-effectively.The measuring system can furthermore comprise a wireless transmission link in order to provide a measured value for the deformation at an element of the motor vehicle fixed to the frame. A processing device of the measurement system may alternatively be provided on the side of the rim or the side of the frame. The transmission path can be realized, in particular, optically or by means of radio waves. Exemplary radio techniques for this include Bluetooth (BT), Bluetooth Low Energy (BLE), WLAN, RFID, NFC, ZigBee or even a proprietary radio technology.According to another aspect of the present invention, an integrated rim for a motor vehicle comprises a measurement system described herein. A sensor section of an optical fiber of the measuring system is attached at a predetermined location of the rim in order to determine a deformation of the rim at this location. The integrated rim can be used for determining static and / or dynamic wheel forces on the motor vehicle. In this case, a plurality of the described rims can also be used on a motor vehicle in order to determine wheel-specific forces.The rim can be part of a wheel of the motor vehicle. The motor vehicle may include multiple wheels, optionally with multiple measurement systems described herein. In this case, a frame-fixed receiver can also receive signals of a plurality of integrated rims. The receiver may provide raw or processed signals about forces at one or more wheels of the motor vehicle.The predetermined location at which a sensor section is located preferably in the rim well of the rim. As a result, the fiber can be covered from the tire to the outside and also further components such as the processing devices can be accommodated between the rim and the tire in a well-protected manner. Preferably, the measurement system is accommodated between a surface of the rim and a cover that can provide additional protection. In another embodiment, a sensor section is attached in the rim center, outside the tire, in particular in such a way that forces acting radially on the rim can be detected. In a further embodiment, a part of the measuring system is accommodated between the rim and the tire and another is attached to another location of the rim.A sensor portion of the fiber may be oriented in the circumferential direction of the rim to determine an elongation or compression of the rim in the radial direction. Thus, a wheel load acting on the rim can be well determined. Preferably, a plurality of sensor sections are distributed over a periphery of the rim. Particularly preferably, sensor sections are situated opposite one another in pairs on the circumference. Diametrically offset forces can thereby be determined in an improved manner.A sensor portion of the fiber may be oriented in the axial direction of the rim in order to determine an elongation or compression of the rim in the lateral direction. As a result, a cornering force acting on the rim can be well determined. Here too, a plurality of sensor sections can be distributed on a circumference of the rim and sensors can be situated opposite one another in pairs.In yet another aspect of the present invention, a motor vehicle includes a wheel having a rim described herein. The motor vehicle can in particular comprise a truck or a trailer. The motor vehicle may comprise an off-road vehicle, an agricultural machine or a construction machine. In a further embodiment, the motor vehicle comprises a passenger car or a motorcycle.The invention will now be described in more detail with reference to the accompanying figures, in which: FIG. 1 shows a motor vehicle; FIG. 2 shows a measuring system; FIG. 3 shows a rim in a first embodiment; and FIG. 4 shows a rim in a second embodimentis.FIG. 1 shows, in FIGS. 1 a, 1 band 1 c, a motor vehicle 100 having a wheel 105 which is mounted rotatably about an axis of rotation 110. The wheel 105 includes a rim 115 and a tire 120. The wheel 105 is, for example, mounted on a tractor 100 on its left side and is designed as a driven wheel 105. Other embodiments are also possible.FIG. 1 ashows the motor vehicle 100, FIG. 1 bshows a rim and FIG. 1 cshows a section through a wheel 105. Purely by way of example, a Cartesian coordinate system with a vertical axis (z), a longitudinal axis (x) and a lateral axis (y) is drawn in each case. The coordinate system is preferably related to the motor vehicle 100 or fixed relative to the latter.Static and / or dynamic forces can act on the wheel 105 in different directions. For example, a wheel load may act in a vertical direction and cause the rim 115 to compress in a vertical direction and stretch in a longitudinal direction, as can be seen easily in FIG. 1 b. A cornering force may shear the rim 115 in a lateral direction, such that a lower edge of the rim 115 is pressed in a lateral direction and an upper in an opposite lateral direction.The present invention provides a technique of measuring deformation of the rim 115 and providing a measurement value. Optionally, based on the deformation and a bending stiffness of the rim 115 in the measurement direction, a load or force acting on the rim 115 can be determined. Measured values can be provided on the rim 115 or on a frame-mounted device of the motor vehicle 105.FIG. 2 shows an exemplary measurement system 200 for use on a motor vehicle 100. A processing device 205 is connected to a light source 210 and a spectrometer 215, between which an optical fiber 220 runs, so that light emitted by the light source 210 can propagate through the fiber 220 and be detected by the spectrometer 215. The fiber 220 is preferably designed as a glass fiber or as a polymer fiber, but other fiber types are also possible.A fiber Bragg grating 230 is formed in the fiber 220 on a sensor section 225, for which purpose a sequence of layers is written into the fiber 220 along the fiber 220. As a result, a periodic modulation of the refractive index, with high and low refractive index ranges, is produced in the fiber core. The fiber Bragg grating 230 reflects or scatters light of the predetermined wavelength and allows light of all other wavelengths to pass, a behavior known as a trap. The predetermined wavelength is dependent on external factors, in particular temperature, tension, pressure or a chemical change.The sensor portion 225 may be attached to the surface of a rim 115 such that deformation of the rim 115 causes deformation of the sensor portion 225. For this purpose, the fiber 220 can be connected to the rim 115 in a materially integral manner, for example in the sensor section 225, for example by adhesive bonding or welding. The deformation of the sensor section can cause a displacement of the predetermined wavelength of the associated fiber Bragg grating 230, which can be detected by means of the spectrometer 215. On the basis of a displacement, a load or force acting on the rim 115 at the location of the sensor section 225 can be deduced. The fiber 220 can also be embedded in the material of the rim 115 or can lie in a depression.Advantageously, a plurality of sensor sections 225 are provided along a fiber 220, each of which carries a fiber Bragg grating 230. Predetermined wavelengths of different fiber Bragg gratings 230 are different from one another, so that spectrometer 215 can determine all band gaps. The predetermined wavelengths are further preferably spaced apart from one another to such an extent that the predetermined wavelengths are different from one another even under unfavourable measurement conditions. The light source 210 is preferably designed to be broadband, so that all predetermined wavelengths are represented in the emitted light. Emitted light can have a wavelength of approximately 1500 to 1600 nm; however, the proposed technique is not fixed to a specific wavelength range. With conventional components, up to about 16 sensor sections 225 can be used on a fiber 220 without problems and evaluated individually as sensors.Optionally, a plurality of fibers 220 may be provided. One or more light sources 210 can be provided for coupling light into the fibers 220. Light emerging from a fiber 220 can be evaluated by means of one or more spectrometers 215. Preferably, only one spectrometer 215 is provided and the fibers 220 can be individually illuminated by multiplexing by means of different light sources 210.As is indicated in FIG. 2, the fibers 220 can be differently laid on a rim 115 and sensor sections 225 of a fiber 220 can be differently oriented in order to absorb deformations in different directions.The measuring system 200 preferably comprises an energy source 235 for supplying the components with electrical energy. For this purpose, a battery or also a device for harvesting energy (energy harvesting) can be used, for example. In a further embodiment, the measuring system 200 can be supplied with electrical energy from the outside, for example by means of an alternating magnetic field.A communication device 240 is configured for wireless communication with a receiver 245, which comprises a corresponding communication device 250, so that a wireless transmission path is formed. The light source 210, the fiber 220, the spectrometer 215 and the communication device 240 are attached to the rim 115, while the receiver 245 usually does not involve a rotational movement of the rim 115 and can be attached to the motor vehicle 105 in a fixed manner with respect to the frame. The processing device 205 may be arranged on the side of the rim 115 or the side of the receiver 245 in different embodiments.Further optionally, a rotation sensor 255 is attached to the rim 115 in order to provide a rotational position of the rim 115 at the moment of a measurement. The rotation sensor 255 is connected to the processing device 205, so that a rotational alignment of the rim 115 and thus of a fiber Bragg grating 230 providing the sensor value can be assigned to a sensor value.FIG. 3 shows a rim 115 with a fiber 220 in a first embodiment. A plurality of fiber Bragg gratings 230 are distributed around a periphery around the rim 115. The fiber Bragg gratings 230 can be attached to the rim 115 for example in the region of a rim shoulder or a rim flange, in the present embodiment for example in the region of the front rim flange, that is to say axially on a side of the rim 115 facing the motor vehicle 100.In the embodiment shown by way of example, the fiber 220 is attached to the rim 115 in front of and behind a sensor section 225, for example in a form-fitting, force-fitting or materially integral manner. In this case, the sensor section 225 can be prestressed between the fastening points in order to be able to absorb positive and negative changes in the distance between the fastening points. In another embodiment, a sensor portion 225 may also be connected to the rim 115 along its extension, in the manner of a strain gauge. Optionally, a circumferential depression can be provided on the rim 115, in which depression the fiber 220 and / or a sensor section 225 can be accommodated.FIG. 3 shows a rim 115 with a fiber 220 in a second embodiment. Here, the fiber 220 meanders on a circumference in the axial direction and in the circumferential direction. A fiber Bragg grating 230 can be attached to the rim 115 at a section of the fiber 220 extending in the axial direction, so that it can detect a deformation of the rim 115 in the lateral direction (y) (cf. FIG. 1 c ).A fiber Bragg grating 230 can also be attached to the rim 115 at a section of the fiber 220 extending in the circumferential direction, so that it can detect a deformation of the rim 115 in the radial direction (x and / or z) (cf. FIG. 1 b ). As shown in FIG. 4, fiber Bragg gratings 230 of different orientations may be formed on the fiber 220 in any order. The illustrated construction is space-saving and can allow the determination of forces in different spatial directions using only one fiber 220. In one variant, fiber Bragg gratings 230 oriented in the circumferential direction on fiber 220 can also be omitted. A further fiber 220, for example in the manner of FIG. 3, can additionally be provided.Reference numerals denote reference numerals100 Motor vehicle 105 Wheel 110 Axis of rotation 115 Rim 120 Tire 200 Measuring system 205 Processing device 210 Light source 215 Spectrometer 220 Optical fiber 225 Sensor section 230 Fiber Bragg grating 235 Energy source 240 Communication device 245 Receiver 250 Communication device 255 Rotation sensor

Claims

A measurement system (200) for a motor vehicle (100), the measurement system (200) comprising the following elements: - an optical fiber (220) having a first and a second end; - wherein in a predetermined sensor section (225) between the first and the second end a fiber Bragg grating (225) is written into the optical fiber (220); - wherein the fiber (220) in the sensor section (225) is configured to be attached to a rim (115) for the motor vehicle (100) on a circumference of the rim (115); - a light source (210) configured to couple light into the first end of the fiber (220); - a spectrometer (215) configured to determine a wavelength of light exiting from the second end; and a processing device (205) which is configured to determine a deformation of the rim (115) in the region of the fiber Bragg grating (225) on the basis of the determined wavelength.The measurement system (200) of claim 1, wherein the fiber Bragg grating (225) is tuned to reflect light of a predetermined wavelength and transmit light of other wavelengths.The measurement system (200) according to claim 2, wherein the predetermined wavelength is dependent on a deformation of the fiber (220) in the sensor section (225).Measuring system (200) according to claim 3, wherein a plurality of sensor sections (225) with fiber Bragg gratings (225) are provided on a fiber (220), the predetermined wavelengths of which are spaced apart from one another by a predetermined minimum.The measurement system (200) according to any one of the preceding claims, wherein a further fiber (220) is provided with a sensor section (225) configured to be attached to the rim (115); wherein the light source (210) and / or the spectrometer (215) are configured to determine optical absorption properties of the fibers (220) in succession.The measurement system (200) according to any one of the preceding claims, further comprising a wireless transmission link (240, 250) for providing a measurement value for the deformation at an element of the motor vehicle (100) fixed to the frame.An integrated rim (115) for a motor vehicle (100); wherein the rim (115) comprises a measurement system (200) according to any of the preceding claims; and a sensor portion (225) of an optical fiber (220) of the measurement system (200) is attached at a predetermined location of the rim (115) to determine a deformation of the rim (115) at that location.The rim (115) of claim 7, wherein the predetermined location is in the well (115).The rim (115) according to claim 7 or 8, wherein a sensor portion (225) of the fiber (220) is oriented in the circumferential direction of the rim (115) in order to determine an extension or compression of the rim (115) in the radial direction.The rim (115) according to any one of claims 7 to 9, wherein a sensor portion (225) of the fiber (220) is oriented in the axial direction of the rim (115) in order to determine an extension or compression of the rim (115) in the lateral directionMotor vehicle (100) comprising a wheel with a rim (115) according to any one of claims 7 to 10.

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