RADAR LEVEL GAUGE WITH ELASTIC SYSTEM

A radar level gauge system for determining a topographic property of a product, comprising a transceiver; a signal transfer element coupled to the transceiver and configured to emit an electromagnetic transmit signal from the transceiver in an emission direction; a propagating member for propagating the transmit signal towards the surface of the product and a reflection signal back towards the transceiver, the propagating member being movably arranged in relation to the signal transfer element and configured to deflect the transmit signal; an elastic system coupled to the signal transfer element and to the propagating member, and arranged to define at least one property of an oscillating movement of the propagating member in relation to the signal transfer element; an actuator arranged to initiate the oscillating movement; and processing circuitry coupled to the transceiver for determining the topographic property based on the transmit signal and the reflection signal.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a radar level gauge system and to a method of determining a topographic property of a product.

TECHNICAL BACKGROUND

Radar level gauge systems are in wide use for measuring filling levels in tanks. Radar level gauging is generally performed either by means of non-contact measurement, whereby electromagnetic signals are radiated towards the product contained in the tank, or by means of contact measurement, often referred to as guided wave radar (GWR), whereby electromagnetic signals are guided towards and into the product by a probe. The electromagnetic signals are reflected at the surface of the product, and the reflected signals are received by a receiver or transceiver comprised in the radar level gauge system. Based on the transmitted and reflected signals, the distance to the surface of the product can be determined.

More particularly, the distance to the surface of the product is generally determined based on the time between transmission of an electromagnetic signal and receipt of the reflection thereof in the interface between the atmosphere in the tank and the product contained therein. In order to determine the actual filling level of the product, the distance from a reference position to the surface is determined based on the above-mentioned time (the so-called time-of-flight) and the propagation velocity of the electromagnetic signals.

While measuring the filling level of a liquid product may be rather straight-forward, it is more challenging to evaluate a solid product, because the surface of the product may be non-flat and/or non-horizontal. Therefore, the highest level of the solid product may not be directly below the antenna of a radar level gauge system of the non-contacting type.

In view of this characteristic of solid products, it is known to scan the transmit signal from the transceiver of the radar level gauge system across the surface of the product, either by mechanically tilting the antenna of the radar level gauge, or by directing the emitted beam using phase array techniques. US 2019/0107424 describes examples of both of these scanning methods.

However, both of these basic scanning methods have drawbacks. Mechanical tilting of the antenna requires a relatively costly and bulky mechanical arrangement, and phase array techniques may make it difficult to transmit sufficient power to get a reliable evaluation result.

SUMMARY

In view of the above, a general object of the present invention is to provide for improved determination of a topographic property of a product, in particular a solid product.

According to a first aspect of the present invention, it is provided a radar level gauge system for determining a topographic property of a product, the radar level gauge system comprising a transceiver for generating, transmitting and receiving electromagnetic signals; a signal transfer element coupled to the transceiver and configured to emit an electromagnetic transmit signal from the transceiver in an emission direction; a propagating member arranged and configured to propagate the transmit signal towards the surface of the product, and to propagate a reflection signal resulting from reflection of the transmit signal at the surface of the product back towards the transceiver, the propagating member being movably arranged in relation to the signal transfer element and configured to deflect the transmit signal from the signal transfer element to a plurality of different propagation directions, each propagation direction corresponding to a position of the propagating member in relation to the signal transfer element in a plane perpendicular to the emission direction; an elastic system coupled to the signal transfer element and to the propagating member, and arranged to define at least one property of an oscillating relative movement between the propagating member and the signal transfer element; an actuator arranged to initiate the oscillating movement; and processing circuitry coupled to the transceiver and configured to determine the topographic property based on the transmit signal and the reflection signal.

The “transceiver” may be one functional unit capable of transmitting and receiving electromagnetic signals, or may be a system comprising separate transmitter and receiver units.

It should be noted that the processing circuitry may be provided as one device or several devices working together.

The present invention is based upon the realization that various topographic properties of a solid product can be determined without detailed knowledge about the scanning direction at all times.

The present inventors have further realized that such scanning with only limited control of the scanning direction can be achieved in a cost-efficient and compact manner, without significantly reducing the transmitted power, by providing a propagating member that can redirect the transmit signal depending on the relative positioning of the propagating member and the signal transfer element, and providing for an oscillating relative movement between the signal transfer element and the propagating member.

Hereby, predictable scanning of the surface of the product can be achieved by simple and cost-efficient means. The scanning pattern across the surface of the product can be determined by selection of the properties of the elastic system. In embodiments, the elastic system may be configured to allow tuning of its properties, providing for tuning of the scanning pattern.

To prevent changes in in the beam shape of the transmit signal, the oscillating movement of the propagating member in relation to the signal transfer element may advantageously be restricted from taking place in the emission direction, so that the oscillating movement can substantially only take place in a plane perpendicular to the emission direction.

In embodiments where a two-dimensional scanning pattern is desired, the elastic system may define a first eigenfrequency of a first component of the oscillating movement and a second eigenfrequency, different from the first eigenfrequency, of a second component of the oscillating movement.

In embodiments, a first one of the signal transfer element and the propagating member may remain stationary and a second one of the signal transfer element and the propagating member may start to move, in relation to a tank where the radar level gauge system is installed, when the oscillating movement is initiated.

In embodiments, the radar level gauge system may further comprise a position indication arrangement arranged and configured to provide a signal indicative of instantaneous positions at different times during movement of the propagating member in relation to the signal transfer element. The processing circuitry may be coupled to the position indication arrangement and configured to determine the topographic property additionally based on the instantaneous positions of the propagating member in relation to the signal transfer element. Hereby, additional detail about the topography of the product can be determined. For instance, the position of the highest level of the product can be determined and/or the shape of the surface of the product can be determined, or at least estimated.

According to a second aspect of the present invention, it is provided a method of determining a topographic property of a product using a radar level gauge system comprising a transceiver; a signal transfer element coupled to the transceiver; a propagating member movably arranged in relation to the signal transfer element and configured to deflect an electromagnetic signal from the signal transfer element depending on a position of the propagating member in relation to the signal transfer element; an elastic system coupled to the signal transfer element and to the propagating member; an actuator; and processing circuitry coupled to the transceiver, the method comprising: generating, by the transceiver, an electromagnetic transmit signal; emitting, by the signal transfer element, the transmit signal in an emission direction; propagating, by the propagating member, the transmit signal towards a surface of the product; propagating, by the propagating member, a reflection signal resulting from reflection of the transmit signal at the surface of the product, back towards the transceiver; receiving, by the transceiver, the reflection signal; oscillating, by the elastic system and the actuator, one of the propagating member and the signal transfer member in relation to the other one of the propagating member and the signal transfer member in a plane perpendicular to the emission direction, while the transmit signal is propagated towards the surface of the product and the reflection signal is propagated back towards the transceiver; and determining, by the processing circuitry, the topographic property of the product based on a timing relation between the transmit signal and the reflection signal.

In summary, the present invention thus relates to a radar level gauge system for determining a topographic property of a product, comprising a transceiver; a signal transfer element coupled to the transceiver and configured to emit an electromagnetic transmit signal from the transceiver in an emission direction; a propagating member for propagating the transmit signal towards the surface of the product and a reflection signal back towards the transceiver, the propagating member being movably arranged in relation to the signal transfer element and configured to deflect the transmit signal; an elastic system coupled to the signal transfer element and to the propagating member, and arranged to define at least one property of an oscillating movement of the propagating member in relation to the signal transfer element; an actuator arranged to initiate the oscillating movement; and processing circuitry coupled to the transceiver for determining the topographic property based on the transmit signal and the reflection signal.

FIG. 1schematically illustrates a radar level gauge system1according to an example embodiment of the present invention installed at a tank3containing a solid product5. As is schematically indicated inFIG. 1, the solid product5has a non-flat surface topography, and the radar level gauge system1is configured to determine a topographic property of the product5, which may, for example, be a maximum, minimum or average level of the product5.

To this end, the radar level gauge system1according to embodiments of the present invention is controllable to deflect the transmit signal STto hit different locations7on the surface of the product5. As is schematically indicated inFIG. 1, a reflection signal SRresulting from reflection of the transmit signal STat the surface of the product5is returned to the radar level gauge system1. This allows the radar level gauge system1to determine the distance to different positions on the surface of the product, which in turn allows determination of the above-mentioned topographic property.

Referring now toFIG. 2, which is a schematic block-diagram of the radar level gauge system1inFIG. 1, the radar level gauge system1comprises a transceiver9, a signal transfer element11, a propagation member13, an elastic system15, an actuator17, processing circuitry19, and a communication interface21.

The transceiver9is configured to generate, transmit and receive electromagnetic signals, advantageously microwave signals, in a, per se, known manner. As will be well-known to one of ordinary skill in the relevant art, the transceiver may, for example, operate using pulsed signals and/or a frequency sweep.

The signal transfer element11is coupled to the transceiver9and configured to emit the above-mentioned transmit signal STin an emission direction23. The signal transfer element11may also capture the reflection signal SRand provide the reflection signal SRto the transceiver9.

The propagating member13is arranged and configured to propagate the transmit signal STtowards the surface of the product5and to propagate the reflection signal SRback towards the transceiver9, via the signal transfer element11. The propagating member13is movably arranged in relation to the signal transfer element11, and is configured to deflect the transmit signal STfrom the signal transfer element11to a plurality of different propagation directions, each propagation direction corresponding to a position of the propagating member13in relation to the signal transfer element11in a plane perpendicular to the emission direction23.

The elastic system15is coupled to the signal transfer element11and to the propagating member13, and is arranged to define at least one property of an oscillating movement of the propagating member13in relation to the signal transfer element11.

In this context, it should be noted that movement of the propagating member13in relation to the signal transfer element11includes movement of one or both of the propagating member13and the signal transfer element11, as long as there is relative movement therebetween.

The actuator17is arranged to at least initiate the oscillating relative movement, between the propagating member13and the signal transfer element11, i.e. to start moving at least one of the propagating member13and the signal transfer element11in relation to the tank3. According to embodiments, a first one of the signal transfer element11and the propagating member13may remain stationary and a second one of the signal transfer element11and the propagating member13may start to move, in relation to the tank3, when the oscillating movement is initiated by the actuator17.

The processing circuitry19is coupled to the transceiver9and configured to determine the above-mentioned topographic property of the product5based on the transmit signal STand the reflection signal SR. In particular, the topographic property may be determined based on a series of timing relations between the transmit signal STand the reflection signal SRwhile the above-mentioned relative oscillating movement is taking place, so that the transmit signal STis deflected in different directions. A distance between a reference position at the radar level gauge system and the surface of the product5may then be determined for the different locations7on the surface of the product5mentioned above with reference toFIG. 1.

In embodiments, a position of the maximum and/or minimum may additionally be determined, and/or the surface topography may be imaged. In such embodiments, the radar level gauge system1may additionally comprise a position indication arrangement24arranged and configured to provide a signal indicative of instantaneous positions of the propagating member13in relation to the signal transfer element11. As is schematically indicated inFIG. 2by the dashed line, the position indication arrangement24may be coupled to the processing circuitry19. In these embodiments, the processing circuitry19may be configured to determine the topographic property additionally based on the instantaneous positions of the propagating member13in relation to the signal transfer element11. In particular a relative position may be acquired for each of the above-mentioned timing relations between the transmit signal STand the reflection signal SR. Based on the relative positions between the signal transfer element11and the propagating member13acquired from the position indication arrangement24, the corresponding locations7on the surface of the product5mentioned above with reference toFIG. 1can be determined.

In embodiments, the position indication arrangement24may comprise at least one accelerometer. Based on the acceleration, and a known initial position, the instantaneous positions of the moving one of the signal transfer element11and the propagating member13can be determined by simply integrating twice. The integration can take place in the accelerometer or in the processing circuitry19.

Alternatively, the position indication arrangement24may comprise a sensor and a known pattern. For instance, an optical pattern may be formed on a visible surface of the moving one of the signal transfer element11and the propagating member13, and a stationary image sensor, such as a CCD or CMOS camera may be used to acquire images of the optical pattern. Based on the images, the instantaneous positions can be determined. Alternatively, the pattern may be formed on a visible surface of the stationary one of the signal transfer element11and the propagating member13, and the image sensor can arranged to move with the moving one of the signal transfer element11and the propagating member13.

The communication from/to the radar level gauge system1via the communication interface21may be wireless communication, or may take place over an analog and/or digital wire-based communication channel. For instance, the communication channel may be a two-wire 4-20 mA loop and signals indicative of distances to the different locations7on the surface of the product5may be communicated by providing a currents corresponding to the distances on the two-wire 4-20 mA loop. Digital data may also be sent across such a 4-20 mA loop, using the HART protocol. Furthermore, pure digital communication protocols such as Modbus or Foundation Fieldbus may be used.

A first example embodiment of the radar level gauge system1inFIG. 1andFIG. 2will now be described with reference toFIGS. 3A-B.

FIG. 3Ais a schematic partial view of the radar level gauge system1facing the product5as seen along the emission direction23. In the partly structural and partly conceptual illustration inFIG. 3A, the transceiver9is realized as a microwave IC mounted on a carrier structure25in the form of a microwave circuit board, and the signal transfer element11comprises a patch formed in the carrier structure25and connected to a signal output (not shown) of the transceiver9. The propagating member13is, in this example configuration, provided in the form of a microwave lens which at least partly has an ellipsoid shape.

InFIG. 3A, the elastic system is conceptually indicated as comprising a first spring element27and a second spring element29. The first spring element27defines a first eigenfrequency woi of a first component of the oscillating movement of the propagating member13in relation to the signal transfer element11in a first direction (the x-direction inFIG. 3A), and the second spring element29defines a second eigenfrequency woe of a second component of the oscillating movement of the propagating member13in relation to the signal transfer element11in a second direction (the y-direction inFIG. 3A). Any elastic system for which the oscillating movement is restricted to a plane (the xy-plane) perpendicular to the emission direction23can be functionally represented by the first spring element27and the second spring element29inFIG. 3A.

In the example configuration inFIG. 3A, the actuator17is indicated as a controllable actuator that is coupled between the carrier structure25and the propagating member13. It should be noted that the actuator17does not have to be coupled to both the carrier structure25and the propagating member13to initiate the oscillating movement, but that the actuator17could, for example, be coupled to the carrier structure25and arranged and controllable to provide impulses to the propagating member13. Furthermore, the actuator17could alternatively be coupled between the elastic system15and a stationary structure, such as the carrier structure25inFIG. 3A.

In addition,FIG. 3Aschematically shows an accelerometer30fixed to the propagating member13, and connected to an at least partly flexible conductor32for providing a signal from the accelerometer30to the processing circuitry (not shown inFIG. 3A).

FIG. 3Bis a simplified side view of the radar level gauge system1inFIG. 3Bthat is mainly intended to illustrate an example configuration and arrangement of the propagating member13in relation to the signal transfer element11. In this example configuration and arrangement, the propagating member13is an ellipsoidal microwave lens with a first focal point31and a second focal point33. As is schematically illustrated inFIG. 3B, the signal transfer element11is arranged in the first focal point31, in the absence of the above-described relative oscillating movement.

As mentioned above, the relative oscillating movement will result in deflection, in this case through refraction, of the transmit signal ST(and the reflection signal SR).FIG. 4Ashows the propagating member13being displaced to the left (and/or the signal transfer element11being displaced to the right) as compared to the situation inFIG. 3B, resulting in deflection of the transmit signal STto the left in relation to the emission direction23, so that a different location7on the surface of the product5is hit by the transmit signal ST.FIG. 4Bshows the propagating member13being displaced to the right (and/or the signal transfer element11being displaced to the left) as compared to the situation inFIG. 3B, resulting in deflection of the transmit signal STto the right in relation to the emission direction23, so that a different location7on the surface of the product5is hit by the transmit signal ST.

FIGS. 5A-Bschematically illustrate different example configurations of the elastic system15coupled to the signal transfer element11and to the propagating member13in the first example embodiment of the radar level gauge system1described above.FIGS. 5A-Bare views of the radar level gauge system1as seen along the emission direction23from the product5side.

In the first example configuration inFIG. 5A, the elastic system15comprises a spring wire35, that is coupled to the carrier structure25and to the propagating member13. The spring wire35is configured to define a first eigenfrequency ω01of a first component of the oscillating movement of the propagating member13in relation to the signal transfer element11in a first direction (the x-direction), and a second eigenfrequency ω02of a second component of the oscillating movement of the propagating member13in relation to the signal transfer element11in a second direction (the y-direction). The oscillating movement is restricted to the xy-plane by the configuration of the spring wire35and/or by a restricting structure (not shown inFIG. 5A).

To illustrate one of many possible alternatives to the spring wire35inFIG. 5A,FIG. 5Bshows that the elastic system15instead comprises a sheet metal structure37that has been shaped to provide the desired properties of the oscillating movement.

FIGS. 6A-Bschematically show a radar level gauge system1according to a second example embodiment of the present invention, where the propagating member13comprises a parabolic reflector. The parabolic reflector has a focal point, and the elastic system is configured in such a way that the signal transfer element11is arranged in the focal point in the absence of the relative oscillating movement, when the system is at rest.

Also for this embodiment of the radar level gauge system1, the relative oscillating movement will result in deflection, in this case through reflection, of the transmit signal ST(and the reflection signal SR).FIG. 6Ashows the signal transfer element11being displaced to the left, resulting in deflection of the transmit signal STto the right in relation to the emission direction23, so that a different location7on the surface of the product5is hit by the transmit signal ST.FIG. 6Bshows the signal transfer element11being displaced to the right, resulting in deflection of the transmit signal STto the left in relation to the emission direction23, so that a different location7on the surface of the product5is hit by the transmit signal ST.

In embodiments with the basic configuration shown inFIGS. 6A-B, the radar level gauge system1may additionally comprise a position indication arrangement as described above. For instance, at least one accelerometer may be integrated in, or attached to, the signal transfer element11.

Although it is indicated inFIGS. 6A-Bthat the signal transfer element11is being displaced, it could be possible to instead displace the propagation member13, or both the signal transfer element11and the propagation member13.

To get a desired coverage of the surface of the product5, it may be desirable to configure the elastic system15to define different first ω01and second ω02eigenfrequencies.FIGS. 7A-Care simulations of scanning patterns obtainable for different configurations of the elastic system15comprised in the radar level gauge system1according to embodiments of the present invention. InFIG. 7A, the ratio between the first ω01and second ω02eigenfrequencies is 1.02, inFIG. 7B, the ratio is 1.04, and inFIG. 7C, the ratio is 1.05.