Method for navigating a vehicle by tracking GNSS signals with selectively switchable tracking loops by means of a switch

Abstract

The invention relates to a method for navigating a vehicle by means of a GNSS receiver having a plurality of channels which are designed to track GNSS signals such that navigation solutions are calculated on the basis of the navigation data decoded from the tracked GNSS signals, wherein on at least one channel, a GNSS signal is tracked with the following steps: a) tracking the GNSS signal by means of a scalar tracking module (1) until a navigation solution is calculated, b) switching the scalar tracking module (1) to a vector tracking module (2) such that the signal is tracked taking into account the navigation solution, or switching the scalar tracking module (1) directly or via the vector tracking module (2) to a differential vector tracking module (3) such that the signal is tracked both taking into account the navigation solution and taking into account base station data, wherein the switching is carried out by means of a switch and depending on the quality of the GNSS signal and the availability of the base station data, and c) returning to step a) if step b) cannot be carried out.

Description

[0001] Description

[0002] title

[0003] Procedure for navigating a through from GNSS with selectively switchable by means of a switch

[0004] State of the art

[0005] The present invention relates to a method for navigating a vehicle by tracking GNSS signals with selectively switchable tracking loops using a switch. Furthermore, a control unit, a computer program, a machine-readable storage medium, and a localization system for a vehicle are specified. The invention can be used in particular in GNSS-supported localization systems for autonomous or semi-autonomous driving.

[0006] Currently, there are a variety of vector tracking (VT) approaches for tracking GNSS satellites, which were developed based on the well-known scalar tracking (ST) approaches to improve tracking capability. The vector tracking approaches can be divided into three main categories: frequency-based vector frequency lock loops (VFLL), code-based vector delay lock loops (VDLL), and phase-based vector phase lock loops (VPLL). Using a (virtual) base station as a reference unit, the vector tracking approaches can be extended; these include, for example, differential vector phase lock loops (DVPLL).

[0007] The most common use of vector tracking approaches is the parallel use of VDLL for code control and VFLL for Doppler control, or the parallel use of VDLL for code control and DVPLL for carrier and Doppler control. Alternatively, Doppler and code control can also be performed using a common VDFLL (i.e., VDLL combined with VFLL). However, with the current use of tracking approaches in a GNSS receiver, the tracking loops to be used are usually already specified during the design of the GNSS receiver, so that, for example, the above-mentioned parallel uses cannot exploit the full potential of the tracking loops used in some scenarios. Therefore, it is desirable to use different tracking loops complementarily and to have the option of selecting the most suitable tracking loops for different scenarios in order to exploit the full potential of the tracking loops used.

[0008] Based on this, the object of the present invention is to alleviate or at least partially solve the problems described with reference to the prior art. In particular, a method for navigating a vehicle by tracking GNSS signals with selectively switchable tracking loops is to be provided. This method enables GNSS signals to be tracked with selected tracking loops depending on scenarios and the real environmental context, so that different tracking loops for tracking GNSS signals can functionally compensate for each other, thus improving overall tracking performance.

[0009] Disclosure of the invention

[0010] A method for navigating a vehicle using a GNSS receiver with a plurality of channels contributes to this, wherein the channels are configured to track GNSS signals so that a navigation solution can be calculated based on the navigation data decoded from the tracked GNSS signals, and wherein the following steps are carried out on at least one channel: a) tracking a GNSS signal with a scalar tracking module until a navigation solution is calculated, b) switching the scalar tracking module to a vector tracking module so that the GNSS signal is tracked taking into account the navigation solution, or switching the scalar tracking module to a differential vector tracking module so that the GNSS signal is tracked taking into account both the navigation solution and base station data,wherein the switching is carried out by means of a switch and depending on the quality of the GNSS signal and the availability of the base station data, and c) returning to step a) if step b) is not executable,

[0011] The described method is particularly suitable for autonomous driving. Autonomous driving is understood here, in particular, to mean the movement of vehicles that behave largely autonomously using a GNSS receiver and based on global navigation satellite systems (GNSS). The vehicles can be a motor vehicle, for example a passenger car, a truck or other commercial vehicle, a robot, or the like. It is particularly advantageous if a self-driving vehicle is equipped with a localization system with such a GNSS receiver for implementing the described method.

[0012] GNSS is the abbreviation for Global Navigation Satellite Systems, such as GPS, GLONASS, Galileo, and Beidou. Each GNSS system comprises a multitude of GNSS satellites distributed across the sky. A GNSS signal is specifically defined as a signal emitted by a GNSS satellite, in which a low-frequency useful signal (e.g., for GPS C / A code, fcode = 1.023 MHz) is modulated onto a high-frequency carrier (e.g., for GPS, finger = 1.57542 GHz). By tracking at least four GNSS satellites of the same GNSS system, it is in principle possible to position and navigate a vehicle three-dimensionally. With favorable geometry (measured, for example, in "dilution of precision") and an increasing number of satellites, the positioning quality generally improves.

[0013] A GNSS receiver can track GNSS satellites by receiving and tracking the GNSS signals broadcast by the corresponding GNSS satellites to decode navigation data from the tracked GNSS signals and calculate a navigation solution based on the decoded navigation data.

[0014] In the GNSS receiver, each received GNSS signal can be tracked on a single channel. The GNSS receiver preferably has a plurality of channels, e.g., two, eight, or twelve. A channel here is, in particular, a GNSS signal processing unit configured to locally demodulate a modulated GNSS signal to determine the information contained in this GNSS signal, e.g., the distortion of the carrier frequency (Doppler frequency), pseudocode, and navigation message.

[0015] When tracking a GNSS signal on a channel, code control, carrier control, and / or Doppler control can be performed for that GNSS signal. Each of these controls can be performed using a corresponding tracking loop. A tracking loop can be a scalar tracking loop, a vector tracking loop, or a differential vector tracking loop extended beyond the vector tracking loop. In general, a tracking loop comprises at least the following basic components: a generator (e.g., NCO: Numerically Controlled Oscillator) for generating a local replica, a correlator for correlating the local replica with a currently received GNSS signal, and a frequency, phase, and / or code discriminator for Doppler estimation and / or code rate estimation.

[0016] To calculate a navigation solution, such as a classic Position-Velocity-Time (PVT) prediction for Single Point Positioning (SPP), preferably at least four GNSS signals are tracked simultaneously. To track many GNSS signals simultaneously, steps a), b), and c) can preferably be performed on many (e.g., four) channels simultaneously, so that each received GNSS signal can be tracked on a single channel.

[0017] According to step a), a GNSS signal is tracked with a scalar tracking module until a navigation solution is calculated.

[0018] The use of the scalar tracking module in step a) has the advantage that a readily available GNSS satellite in the field of view can be quickly acquired. The scalar tracking module can include a delay-lock loop (DLL) for code control. Additionally, the scalar tracking module can include a frequency-lock loop (FLL) for Doppler control and / or a phase-lock loop (PLL) for carrier phase control. Alternatively, the scalar tracking module can include an FLL-based PLL tracking loop (F-PLL) for Doppler control and phase control. The frequency-lock loop (FLL), the phase-lock loop (PLL), the delay-lock loop (DLL), and the FLL-based PLL tracking loop (F-PLL) are referred to herein as scalar tracking loops.

[0019] In step a), the scalar tracking module can be configured to use only one or more scalar tracking loops. Compared to other tracking loops, scalar tracking loops are the easiest to configure, therefore require the least computing power, and can function well with high carrier-to-noise ratios. Using the scalar tracking module with only one or more scalar tracking loops has the particular advantage of allowing a readily available GNSS satellite in the field of view to be detected as quickly as possible.

[0020] If a navigation solution such as a classical Position-Velocity-Time (PVT) prediction for Single Point Positioning (SPP) can be calculated in step a), this means that at least the GNSS satellite detected by the scalar tracking module and the GNSS signal emitted by this GNSS satellite are trackable and available.

[0021] To track the GNSS signal tracked with the scalar tracking module in step a) more accurately and robustly, the scalar tracking module is switched to a vector tracking module in step b), so that the GNSS signal is tracked taking the navigation solution into account. Alternatively, the scalar tracking module can also be switched to a differential vector tracking module, allowing the GNSS signal to be tracked taking both the navigation solution and base station data into account. Switching is performed via a switch and depends on the quality of the GNSS signal and the availability of valid base station data.

[0022] The vector tracking module may include at least one vector delay lock loop (VDLL), so that code control can be performed using the vector delay lock loop (VDLL). In this embodiment, Doppler control and / or carrier phase control can further be performed using a frequency lock loop (FLL) and / or a phase lock loop (PLL). Additionally or alternatively, the vector tracking module may include a vector frequency lock loop (VFLL) and / or a vector phase lock loop (VPLL). In this embodiment, Doppler control can be performed using the vector frequency lock loop (VFLL) and / or carrier phase control can be performed using the vector phase lock loop (VPLL). The vector delay lock loop (VDLL), the vector frequency lock loop (VFLL), and the vector phase lock loop (VPLL) are referred to herein as vector tracking loops.

[0023] The main difference between scalar and vector tracking loops can be summarized as follows: The single-channel scalar tracking loop tracks a GNSS signal independently of other channels. The scalar tracking loop is the easiest to configure, therefore requires the least computing power, and can be used in high carrier-to-noise conditions, such as outdoors or on highways.

[0024] In comparison to scalar tracking loops, a vector tracking loop tracks on one channel also depending on other channels. For example, the navigation solution, which was also calculated using decoded navigation data from other GNSS signals tracked on other channels, is fed back into the vector tracking loop so that, for example, the Doppler frequency and / or the code rate can be estimated not only using the output information of the discriminator configured in the vector tracking loop, but also using the currently calculated navigation solution. This has the particular advantage that if the quality of the GNSS signal to be tracked deteriorates or the corresponding GNSS satellite is temporarily blocked due to an obstacle or interference, the vector tracking loop can correct the GNSS signal using information from the other channels, such asthe navigation solution, such as the position and speed of the vehicle and the GNSS satellite. Compared to scalar tracking loops, the vector tracking loop therefore offers higher positioning accuracy and greater robustness, especially in low carrier-to-noise conditions, such as in urban environments.

[0025] Switching from the scalar tracking module to the vector tracking module has the advantage that the GNSS signal can continue to be tracked even in the case of degraded reception and / or increased safety and accuracy requirements. According to step b), the scalar tracking module can also be switched to a differential vector tracking module. The differential vector tracking module can comprise at least one differential vector phase-lock loop (DVPLL), so that Doppler estimation can be performed using the differential vector phase-lock loop (DVPLL). In this embodiment, the code rate C rbased on the Doppler frequency d determined with the DVPLL according to the formula C r = fcode *(1 + d / frrägger) where C r the code rate, d the Doppler frequency, fcode the nominal code frequency (e.g. for GPS L1 , fcode = 1 ,023 MHz), frrägger the nominal carrier frequency (e.g. for GPS L1 , frrä gge r = 1 .57542 GHz).

[0026] The differential vector phase-lock loop (DVPLL) is referred to here as a differential vector tracking loop. A differential vector tracking loop is an extension of the vector tracking loop in that it uses a base station as a reference unit, thus feeding additional base station data from the base station into the differential vector tracking loop. The base station is preferably located at a fixed location with a clear view of the sky and can measure a GNSS satellite, which is also measured and tracked by one channel of the GNSS receiver in the vehicle, so that the measured values ​​of the GNSS receiver can be corrected by the measured values ​​of the base station. The base station data is, in particular, correction data for improving the tracking accuracy of the GNSS signal currently tracked on the respective channel.In addition, the base station data may include the code phase measurements measured by the base station, carrier phase measurements, Doppler frequency measurements of the corresponding GNSS satellite, and position information of the base station.

[0027] Compared to the vector tracking loop, the differential tracking loop offers even greater positioning accuracy and robustness thanks to the additional base station data. The differential vector tracking loop can be used when valid base station data is available from a base station and can be used when particularly high security and accuracy requirements are required.

[0028] In step b), it is possible for the scalar tracking module to switch directly to the vector tracking module if a valid navigation solution is available, or to switch directly to the differential vector tracking module if both a valid navigation solution and valid base station data are available. Alternatively, the scalar tracking module can first switch to the vector tracking module if a valid navigation solution is available, and then switch from the vector tracking module to the differential vector tracking module if valid base station data is also available and even higher positioning accuracy and robustness is required.

[0029] Analogous to switching from the scalar tracking module to the vector tracking module or to the differential vector tracking module, there are also options for switching back to the scalar tracking module according to step c).

[0030] It is possible to switch the vector tracking module or the differential vector tracking module directly to the scalar tracking module if, for example, certain signal quality monitors detect erroneous or insufficient overall availability. This allows, for example, the scalar tracking module to track a new GNSS signal (i.e., a new GNSS satellite).

[0031] It is also possible to first switch the differential tracking module to the vector tracking module, for example, if the base station data is no longer available, and only then switch back from the vector tracking module to the scalar tracking module if DVLL also no longer functions, for example, if the code lock is lost.

[0032] In contrast to known approaches in which a GNSS signal is only tracked with one or more fixed (i.e., non-selective or selectable) tracking loops, the method proposed here allows a GNSS signal to be selectively tracked with one or more of the most suitable tracking loops using a switch. In step a) the corresponding GNSS satellite can be acquired as quickly as possible, in step b) the accuracy and robustness of the signal tracking can be improved, and in step c) a new GNSS satellite can be quickly acquired if the currently tracked GNSS satellite can no longer be tracked. With the method proposed here, the full potential of all vector tracking loops can be exploited without major hardware changes. The switch can, for example, be a software-based switching logic implemented in a microcontroller or microprocessor as the corresponding device.

[0033] It is preferred if, in step a), the GNSS signal is tracked with the scalar tracking module such that the code control is carried out with a delay lock loop, while the Doppler and / or carrier phase control is carried out with a frequency lock loop and / or a phase lock loop.

[0034] It is preferred if, in step b), the GNSS signal is tracked with the differential vector tracking module such that at least the Doppler and carrier phase control are performed using a differential vector phase-lock loop and a base station. In this embodiment, the code rate estimation can be performed based on the estimated Doppler frequency. Alternatively, the code rate estimation and code control can continue to be performed using the VDLL.

[0035] It is preferred if, in step b), the GNSS signal is tracked with the vector tracking module such that at least the code control is performed using a vector delay lock loop. In this embodiment, the Doppler and / or carrier phase control can be performed using a frequency lock loop and / or a phase lock loop. Alternatively, the Doppler control can be performed using a vector frequency lock loop.

[0036] It is preferred if, in step b), the code control is carried out with the vector delay lock loop taking into account the LOS projection and the output information of the code discriminator configured in the vector delay lock loop.

[0037] The output information of the code discriminator configured in the vector delay-lock loop is the currently measured code phase deviation. The LOS projection is the prediction of the code phase deviation of the tracked GNSS signal at time k+1 by predicting the corresponding GNSS satellite in the field of view based on the calculated navigation solutions, in particular the calculated vehicle position information at time k.

[0038] With the predicted code phase deviation by the LOS projection and the currently measured code phase deviation by the code discriminator, the accuracy and robustness for code control and signal tracking can be improved.

[0039] By comparing the predicted with the measured code phase deviation, it can also be decided whether the vector tracking module should be switched back to the scalar tracking module or further to the differential vector tracking module.

[0040] It is preferred if the vector tracking module is switched to the differential tracking module, taking into account the LOS projection and the output information of the code discriminator. Weighting factors can be used between VDLL- and DVPLL-based code control. It can be provided that the weighting factor of the output information of the carrier phase discriminator configured in the DVPLL is reduced if the output information of a code discriminator, e.g., a code discriminator configured in the VDLL, for code control of the same GNSS signal deviates from a predefined threshold.

[0041] It is preferred if the quality of the GN SS signal is assessed using a signal quality monitoring unit based on at least one of the following criteria:

[0042] Carrier-to-noise ratio of the GNSS signal, navigation data decoded from the GNSS signal, overall status of the GNSS signal tracking, hysteresis threshold related to the number of available GNSS satellites in the field of view,

[0043] Availability of base station data.

[0044] It is preferred if a control device for the GNSS receiver is configured to carry out a described method.

[0045] It is also preferred if a computer program is used to carry out a method described here. In other words, this particularly concerns a computer program (product) comprising instructions that, when executed by a computer, cause the computer to carry out a method described here. It is also preferred if a machine-readable storage medium is used on which the computer program proposed here is stored. The machine-readable storage medium is usually a computer-readable data carrier.

[0046] It is particularly preferred if a localization system for a vehicle is set up to carry out a method described here.

[0047] The invention and the technical environment are explained below with reference to Fig. 1. It should be noted that Fig. 1 is schematic in nature. Furthermore, it should be noted that the features shown in Fig. 1 do not necessarily have to be used in the illustrated combination; rather, partial features can be extracted and combined with other explanations of the description. Anything different will only apply if this is explicitly stated here as a mandatory combination of features.

[0048] Fig. 1 shows schematically and by way of example a method presented here for tracking GNSS signals with selectively switchable tracking loops in a GNSS receiver during a regular operating sequence.

[0049] The method is illustrated in Fig. 1 by a state machine. The state machine here has three circles that represent three different states: the first state, in which a GNSS signal is tracked using a scalar tracking module 1, the second state, in which a GNSS signal is tracked using a vector tracking module 2, and the third state, in which a GNSS signal is tracked using a differential vector tracking module 3. Switching between the different states can be accomplished using a switch. The arrows in Fig. 1 represent the state transitions, i.e., how one state transitions to another, or in other words, how one tracking module switches to another tracking module. During state transitions, or when remaining in the states, certain actions are executed under specific conditions.These actions are referred to as method steps a), b), and c) and are represented by blocks 110, 120, and 130. Method steps a), b), and c) with blocks 110, 120, and 130 are merely examples here. In block 110, a GNSS signal is tracked with a scalar tracking module 1 until a navigation solution is calculated, such as a classic position-velocity-time (PVT) prediction for the positioning of individual points (single point positioning (SPP)). The Doppler and / or carrier phase control of the GNSS signal can be performed with an FLL and / or a PLL, while the code control of the GNSS signal can be performed with a DLL.

[0050] In block 120, a switchover occurs from the scalar tracking module 1 to a vector tracking module 2 or to a differential vector tracking module 3. As the state machine in Fig. 1 shows, there are three possible switches. In the first case, the scalar tracking module 1 can be switched directly to the vector tracking module 2, e.g., when a valid navigation solution is available. In the second case, the scalar tracking module 1 can be switched directly to the differential vector tracking module 3, e.g., when both a valid navigation solution and valid base station data are available. In the third case, the scalar tracking module 1 can be switched to the differential vector tracking module 3 via the vector tracking module 2.This means that the scalar tracking module 1 can first be switched to the vector tracking module 2 when a valid navigation solution but no valid base station data is available, and then switched from the vector tracking module 2 to the differential vector tracking module 3 when valid base station data is also available.

[0051] In block 130, a return from the second or third state to the first state occurs if the second and third states are no longer executable. Analogous to switching from the scalar tracking module 1 to the vector tracking module 2 or to the differential vector tracking module 3, there are also three possibilities for returning, as the state machine in Fig. 1 shows. In the first possibility, the vector tracking module 2 can be switched directly to the scalar tracking module 1, and in the second possibility, the differential tracking module 3 can be switched directly to the scalar tracking module 1. In these two possibilities, for example, all DVPLL and / or VDLL executions are stopped if, for example, certain signal quality monitors detect faulty or insufficient overall availability. In this way, for example, the scalar tracking module 1 can track a new GNSS signal (i.e., a new GNSS satellite).In the third option, the differential tracking module 3 can first be switched to the vector tracking module 2, e.g., if only the base station data is no longer available, and only then can the vector tracking module 2 switch back to the scalar tracking module 1, e.g., if the DVLL also no longer functions, e.g., if the code lock is lost.

[0052] According to the state machine shown in Fig. 1, GNSS signals can be tracked using a GNSS receiver located in a vehicle and equipped with multiple channels. To calculate navigation solutions, many GNSS signals are tracked on one channel each, with one GNSS signal being tracked on each available channel using the following switching logic:

[0053] Step (1): Use the Scalar Tracking Module 1 for Doppler and / or carrier phase control, e.g., with an FLL and / or PLL, and for code control with a DLL, until a classical Position-Velocity-Time (PVT) prediction for Single Point Positioning (SPP) is available,

[0054] Step (2): Initiating and operating the vector tracking module 2, where, for example, the code control can be performed with a VDLL, while the Doppler and / or carrier phase control can continue to be performed with the FLL and / or PLL, and returning to step (1) if the VDLL is no longer operable, e.g., upon loss of the code lock.

[0055] Step (3): Activate and operate the Differential Vector Tracking Module 3 when an RTK fix is ​​available so that Doppler and carrier phase control can be performed with a DVPLL,

[0056] Step (4): Executing code control during operation of the differential vector tracking module 3 by subtracting code rates from the LOS projection estimated based on the PVT prediction, and returning to step (1) if the DVPLL is no longer operational, and step (5): Stopping all DVPLL and / or VDLL executions if a signal quality monitor detects faulty or insufficient overall availability.

[0057] In addition to step (2), a VFLL or a PLL / FLL can be used to support the VDLL. This means that while code control is performed with the VDLL, Doppler frequency control can be performed with a VFLL or an FLL, and carrier frequency control with a PLL or an F-PLL.

[0058] In addition to step (3) and step (4), the code rate C r based on the Doppler frequency d determined with the DVPLL according to the formula C r= fcode *(1 + d / frrägger) where C r the code rate, d the Doppler frequency, fcode the nominal code frequency (e.g. for GPS L1, fcode = 1,023 MHz), flügger the nominal carrier frequency (e.g. for GPS L1, fTrä gg er= 1 .57542 GHz).

[0059] In addition to step (5), the Signal Quality Monitoring (SQM) may perform a cross-check according to at least one of the following criteria:

[0060] - the quality of the received GNSS signal (e.g. based on the carrier-to-noise ratio)

[0061] - the navigation data decoded from the GNSS signal,

[0062] - Overall status of GNSS signal tracking

[0063] - Hysteresis thresholds related to the number of available GNSS satellites in the field of view,

[0064] - Availability of base station data, especially RTK correction data.

[0065] Furthermore, the decision to switch between the scalar vector tracking module 1, the vector tracking module 2 and the differential vector tracking module 3 can be made taking into account the LOS projection and the output information of the discriminators configured in the respective tracking loops used.

Claims

Claims 1. A method for navigating a vehicle using a GNSS receiver with a plurality of channels configured to track GNSS signals so that navigation solutions are calculated based on the navigation data decoded from the tracked GNSS signals, wherein a GNSS signal is tracked on at least one channel with the following steps: a) tracking the GNSS signal with a scalar tracking module (1) until a navigation solution is calculated, b) switching the scalar tracking module (1) to a vector tracking module (2) so that the signal is tracked taking into account the navigation solution, or switching the scalar tracking module (1) directly or via the vector tracking module (2) to a differential vector tracking module (3) so that the signal is tracked taking into account both the navigation solution and base station data,wherein the switching is carried out by means of a switch and depending on the quality of the GNSS signal and the availability of the base station data, and c) returning to step a) if step b) is not feasible.

2. The method according to claim 1, wherein in step a) the GNSS signal is tracked with the scalar tracking module (1) such that the code control is carried out with a delay lock loop, while the Doppler and / or carrier phase control is carried out with a frequency lock loop and / or a phase lock loop.

3. The method according to claim 1 or 2, wherein in step b) the GNSS signal is tracked with the differential vector tracking module (3) such that at least the Doppler and carrier phase control are carried out with a differential vector phase lock loop and a base station.

4. Method according to one of the preceding claims, wherein in step b) the GNSS signal is tracked with the vector tracking module (2) in such a way that that at least the code control is performed with a vector delay lock loop.

5. The method according to claim 4, wherein the Doppler and / or carrier phase control is carried out with a frequency lock loop and / or a phase lock loop.

6. The method of claim 4, wherein the Doppler control is performed with a vector frequency lock loop.

7. The method according to claim 4, wherein the code control is carried out with the vector delay lock loop taking into account the LOS projection and the output information of the code discriminator configured in the vector delay lock loop.

8. The method according to claim 7, wherein the vector tracking module (2) is switched to the differential tracking module (3) taking into account the LOS projection and the output information of the code discriminator.

9. Method according to one of the preceding claims, wherein the quality of the GNSS signal is assessed using a signal quality monitoring unit based on at least one of the following criteria: Carrier-to-noise ratio of the GNSS signal, navigation data decoded from the GNSS signal, overall status of the GNSS signal tracking, Hysteresis threshold related to the number of available GNSS satellites in the field of view, Availability of base station data.

10. Control device for the GNSS receiver, which is configured to carry out a method according to one of the preceding claims.

11. Computer program for carrying out a method according to one of the preceding claims 1 to 9.

12. A machine-readable storage medium on which the computer program according to claim 11 is stored.

13. Localization system for a vehicle, arranged to carry out a method according to one of claims 1 to 9.

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