Method for determining integrity information of a positioning result of a positioning device for a vehicle

Abstract

The present invention relates to a method for determining at least one integrity information regarding a GNSS-based positioning device (2) of a vehicle (1) in case of a sudden and significant change in GNSS reception situation. The method at least comprises the following steps: a) determining a current own position of the vehicle (1) by means of the GNSS-based positioning device (2), b) determining at least one integrity information regarding the own position determined in step a) by means of the GNSS-based positioning device (2), c) identifying a suddenly and significantly changing GNSS reception situation or a significantly changed GNSS reception situation, d) adapting the determination of the at least one integrity information to the changing or changed GNSS reception situation.

Description

Field of the Invention

[0001] The present invention relates to a method for determining at least one integrity information regarding a GNSS-based positioning device of a vehicle in the case of a sudden and significant change in GNSS reception situation. Furthermore, a computer program for executing the method, a machine-readable storage medium storing the computer program, and a correspondingly designed positioning device for a vehicle are proposed. The present invention can be used in particular in GNSS-based positioning systems for autonomous or semi-autonomous driving. Background Art

[0002] Geospatial position determination can be performed at substantially every point on the earth by means of the Global Navigation Satellite System (GNSS). GNSS satellites orbit the earth and transmit encoded signals, by means of which a GNSS receiver calculates the distance or spacing of the receiver from the satellite by estimating the time difference between the signal reception time point and the transmission time. If there are enough satellites (typically more than 5), the estimated distances from the satellites can be converted into an estimate of the receiver position. Currently, there are more than 130 GNSS satellites orbiting the earth, which means that typically at most 65 of them are visible on the local horizon.

[0003] When referring to the performance of a (GNSS / INS) positioning sensor, the integrity criterion is usually also mentioned in addition to the three criteria of accuracy, continuity, and availability. Integrity is generally defined as a measure of confidence in the accuracy of the information provided by a GNSS or GNSS / INS system. So far, the studied integrity determination schemes are basically based on the instantaneous variance and / or standard deviation of the parameter estimation of the positioning solution. However, this main mathematical approach has the following disadvantages: the change of external influences cannot be fully considered, so that the integrity value is determined at least temporarily when necessary, and this integrity value cannot fully reflect the integrity value of the real situation, and in the worst case, it will also show an overly high integrity. In this case, particular focus is on further improving the positioning solution for performing integrity determination. Summary of the Invention

[0004] Here, a method for determining at least one integrity information regarding a (at least also) GNSS-based positioning device of a vehicle in the case of a sudden and significant change in GNSS reception situation is proposed, the method at least comprising the following steps:

[0005] a) determining the current own position of the vehicle by means of a GNSS-based positioning device,

[0006] b) determining at least one integrity information regarding the own position determined in step a) by means of a GNSS-based positioning device,

[0007] c) Identify a GNSS reception situation that is suddenly and significantly changing or a GNSS reception situation that has significantly changed,

[0008] d) Adapt the determination of at least one integrity information to the changing or changed GNSS reception situation.

[0009] To execute the method, for example, steps a), b), c) and d) can be executed at least once and / or repeated in the proposed order. In addition, steps a), b), c) and d), in particular steps a) and b) and possibly c), can be executed at least partially in parallel or simultaneously.

[0010] The method can in particular contribute to the determination of at least one integrity information, for example during a phase when (purely or mainly) GNSS-based positioning is not feasible, in particular during dead reckoning (so-called Dead Reckoning; abbreviated as DR), for example the so-called protection level. Here, dead reckoning particularly relates to a phase or operating mode in which the positioning device uses an inertial positioning method, such as inertial navigation. For example, if GNSS reception is disturbed or severely restricted, as can be observed, for example, in an urban canyon or a street canyon, beside a heavy vehicle and / or in a tunnel, the above-mentioned solution can be implemented.

[0011] The positioning device (positioning sensor) can be, for example, a combined GNSS-INS sensor, or the positioning can include such a combined GNSS-INS sensor. In the context, INS represents Inertial Navigation System. Thus, the positioning device can be designed to perform the positioning of the vehicle at least also based on GNSS measurements. The positioning device can preferably also be designed to perform the vehicle positioning combinatorially or fusionally based on GNSS measurements and inertial measurements (inertial measurements) and / or vehicle sensor data, that is, for example, environmental sensor data. For example, a steering angle sensor and / or a wheel speed sensor can be used as vehicle sensors. For example, a camera, a RADAR sensor, a LIDAR sensor and / or an ultrasonic sensor can be used as environmental sensors. In addition, map data from a digital map and / or messages from other vehicles can also be used in the positioning.

[0012] In step a), the current own position of the vehicle is determined by means of a GNSS-based positioning device. The positioning device can here perform a combined (hybrid) GNSS- and INS-based positioning. If GNSS-based positioning is temporarily not possible, INS-based positioning can be employed in step a). For the positioning, the positioning device can perform at least one parameter estimation. For example, as parameters, the (own) position, (own) speed, (own) acceleration and / or orientation of the vehicle can be estimated. In particular, at least the (own) position of the vehicle is estimated.

[0013] In step b), at least one integrity information regarding the own position determined in step a) is determined by means of a GNSS-based positioning device. The integrity information can in particular be the integrity range of the parameter estimation (of the at least one parameter described previously), where the integrity range describes the range in which the estimated parameter has a minimum probability. In other words, the integrity range describes the range in which the estimated parameter value actually is with a minimum probability. The estimated parameter (value) here basically describes the (individual, in particular instantaneous) estimation result of the parameter estimation. In other words, this particularly means that the integrity range describes the range in which the true or actual value of the estimated parameter is with a minimum probability. Such an integrity range can also be referred to as the so-called "protection level".

[0014] The minimum probability is usually a preset minimum probability. The minimum probability is preferably 90%, particularly preferably 95% or even 99%.

[0015] The integrity range is preferably the protection level. The protection level here usually describes the (spatial, in particular two- or three-dimensional) range in which the estimated parameter (value) is (actually) with a minimum probability. The estimated parameter (value) here basically describes the (individual, in particular instantaneous) estimation result of the parameter estimation. In other words, this particularly means that the protection level describes the range in which the true or actual value of the estimated parameter is with a minimum probability.

[0016] In other words, the protection level particularly describes the confidence interval or (spatial) confidence range in which the true value of the estimated parameter is with a minimum probability. Here, the estimated value of the parameter usually lies in the middle or center of the confidence interval or confidence range.

[0017] The minimum probability that the true or actual value of the estimated parameter actually lies within the protection level is much higher than the "usual" integrity range. Here, the minimum probability is typically higher than 99.99%, particularly preferably higher than 99.999% or even higher than 99.9999%. At this protection level, the minimum probability cannot be expressed as a percentage, but rather in terms of possible errors within a specific time interval. For example, the protection level can be defined such that the parameter in question exceeds the protection level at most once in 10 years. For example, the protection level can be expressed as a dimensionless probability or ratio, i.e., the probability of an occurrence error over a time interval.

[0018] The protection level is a (safety) parameter of the integrity concept used in the context of urban vehicles. The protection level can also be described here as a statistical error limit, which is calculated such that the probability that the absolute position error exceeds the alarm limit is less than or equal to the target integrity risk. Similar to the definition of the alarm limit value, the protection level can usually also be defined separately for the horizontal level (Horizontal Protection Level, HPL) and the vertical direction (Vertical Protection Level, VPL). Here, particular attention is paid to the horizontal dimension, which is defined as the horizontal protection level with the radius of a circle or (more generally) the semi-axis of an ellipse in the horizontal level (the local level tangent to the ellipsoid WGS - 84), where their center is located at the true position, which is described as the area for which compliance with the specified horizontal position is ensured. Here, it is especially the horizontal area where, when using autonomous error identification, the requirements for identifying faults and false alarms of the selected satellite group are met. Usually, the alarm range is specified by the application and the protection level is calculated by the positioning device. Since the position error cannot be observed, a decision regarding the alarm can be made by comparing the specified alarm limit value (AL) and the calculated protection level (PL). In particular, if PL > AL, an alarm can be triggered. Conversely, in the case of PL < AL, an alarm is usually not triggered.

[0019] In step c), a GNSS reception situation that is suddenly and significantly changing or has significantly changed is identified. The GNSS reception situation is characterized in particular by the number of GNSS satellites that can be received and / or the constellation (undisturbed and / or non-reflected). This typically relates to the GNSS satellites that can be received by the vehicle or the GNSS antenna of the vehicle. In other words, "suddenly" is particularly understood here as a sudden change, for example, a change that occurs within a time period of 60 seconds or less, preferably within a time period of 30 seconds or less, and particularly preferably within a time period of 15 seconds or less. In other words, "significantly" is particularly understood here as a severe change, for example, a change in the GNSS reception situation of at least 50%, preferably at least 70%, and particularly preferably at least 90%. For example, when driving into a tunnel, a significant decrease in the GNSS reception situation can be observed. Here, the number of GNSS satellites that can be received usually suddenly decreases by 90% or even completely. For example, when driving out of a tunnel, a significant increase in the GNSS reception situation can be observed. Here, the number of GNSS satellites that can be received usually suddenly increases. For example, a significantly changed GNSS reception situation can be observed during driving in a tunnel. Here, the tunnel is selected as an example of an area with significant GNSS shadow. The normal GNSS reception on an open surface is particularly used as a benchmark.

[0020] In step d), the determination of at least one integrity information is adapted to the changing or changed GNSS reception situation. For adaptation, in particular, the mathematically determined calculation of the integrity information is artificially intervened. In the case of a normal (undisturbed) GNSS reception situation, the integrity information can be determined, for example, based on at least one variance and / or standard deviation for estimating the own position. For example, a positioning filter, i.e., for example, a Kalman filter, can be used for this purpose. In such a filter, an algorithm is usually stored, which can process GNSS data and / or INS data as input variables to output the position result within the estimated range and its associated integrity information, i.e., for example, variance (or standard deviation) and / or covariance matrix as output variables. In the context, adaptation can be implemented, for example, as multiplying the integrity information (variance and / or standard deviation) by a scaling factor and / or adding an additional (value) to the integrity information. Usually, no subtraction is required because typically too low values for the integrity information, especially the protection level, can be observed in the reception situation changes focused on here. In other words, this particularly means that the scaling factor and / or the additional (value) are always positive.

[0021] According to an advantageous design, it is proposed that the adaptation in step d) is implemented to attenuate and / or at least partially correct the changes in the integrity information that occur due to the suddenly and significantly changing or significantly changed GNSS reception situation. "Attenuation" can particularly be understood as artificially canceling an overly strong downward shift.

[0022] According to another advantageous design, it is proposed that the adaptation in step d) is implemented such that during a sudden and significantly decreasing GNSS reception, the integrity information is scaled with a (positive) scaling factor and / or a determined (positive) first additional value is added to the integrity information. In this case, the scaling of the determined first additional value and / or the addition of the determined first additional value can be performed for a preset first duration (or during a preset first duration). The first duration can be selected, for example, according to the usual transition time when driving into a tunnel.

[0023] According to another advantageous design, it is proposed that the adaptation in step d) is implemented such that during a significantly reduced GNSS reception, a determined (positive) second additional value is added to the integrity information. Usually, no second duration is provided, however, an additional duration of the second additional value, the second duration, can be considered.

[0024] According to another advantageous design, it is proposed that the adaptation in step d) is implemented such that during a sudden and significantly increasing GNSS reception, a determined (positive) third additional value is added to the integrity information. In this case, the addition of the determined third additional value can be performed for a preset third duration (or during a preset third duration). The third duration can be selected, for example, according to the usual transition time when driving out of a tunnel.

[0025] According to another aspect, a computer program for performing the method proposed herein is provided. In other words, this particularly relates to a computer program (product) that includes instructions which, when the program is executed by a computer, cause the computer to perform the method described herein.

[0026] According to another aspect, a machine-readable storage medium is provided on which the computer program proposed herein is stored or deposited. A machine-readable storage medium is generally a computer-readable data carrier.

[0027] According to another aspect, a positioning device for a vehicle is provided, wherein the positioning device is configured to perform the method described herein. The device can, for example, include a computer and / or a control device (controller) that can execute instructions to perform the method. For this purpose, the computer or the control device can, for example, execute the proposed computer program. For example, the computer or the control device can access the proposed storage medium in order to be able to execute the computer program. The positioning device can be, for example, a mobile and position sensor that is particularly provided in or at the vehicle.

[0028] The details, features, and advantageous design options discussed in connection with this method can correspondingly also occur in the computer program and / or storage medium and / or positioning device introduced here, and vice versa. In this regard, for a more detailed characterization of the features, reference is made in full to the statements made there. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The solution introduced here and its technical environment are explained in more detail below with reference to the drawings. It should be noted that the invention is not intended to be limited by the embodiments shown. In particular, unless otherwise explicitly stated, partial aspects of the facts explained in the figures can also be extracted and combined with other components and / or knowledge from other figures and / or this description. The drawings schematically show:

[0030] Figure 1 A flow example of the method introduced here, and

[0031] Figure 2 An exemplary positioning device described here in a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0032] Figure 1 Schematically shows an exemplary flow of the method introduced here. The method is for determining at least one integrity information about the positioning result of the GNSS-based positioning device 2 of the vehicle 1 in the case of a sudden and significant change in the GNSS reception situation. The order of steps a), b), c), and d) shown in blocks 110, 120, 130, and 140 is exemplary and can be traversed at least once in the shown order, for example, to execute the method.

[0033] In block 110, according to step a), the current own position of the vehicle 1 is determined by means of the GNSS-based positioning device 2. In block 120, according to step b), at least one integrity information about the own position determined in step a) is determined by means of the GNSS-based positioning device 2. In block 130, according to step c), a suddenly and significantly changing or significantly changed GNSS reception situation is identified. In block 140, according to step d), the determination of at least one integrity information is adapted to the changing or changed GNSS reception situation.

[0034] The adaptation in step d) can be implemented as attenuating and / or at least partially correcting the changes in the integrity information that occur due to the suddenly and significantly changing or significantly changed GNSS reception situation.

[0035] The adaptation in step d) can be implemented as follows: during a sudden and significant reduction in GNSS reception, scale the integrity information by a scaling factor and / or load the determined first additional value to the integrity information. In this case, the scaling of the determined first additional value and / or the loading of the determined first additional value can be performed for a preset first duration.

[0036] For example, when entering the dead reckoning area or immediately after just entering the dead reckoning area, calculate the (current) protection level (PL) used as the integrity information for the first duration according to the following formula:

[0037] PL(t) = s.sigma + b

[0038] Here, t is the (current) time, s is the first scaling factor, b is the first additional value, and sigma is the (current) standard deviation (or the root of the variance) of the self-position estimate.

[0039] The first duration can be determined empirically. For example, 10 seconds can be used here. The first scaling factor can also be determined empirically. Sigma is the (current) standard deviation estimated from, for example, the positioning filter of the positioning device.

[0040] The first additional value can be used to compensate for systematic errors (biases) and is determined in the following way:

[0041] If PL_zuletzt - PL_DR > 0, then it is PL_zuletzt - PL_DR, otherwise it is 0

[0042] Here, PL_zuletzt is the last protection level value before entering the dead reckoning area, and PL_DR is the first protection level value after entering the dead reckoning area.

[0043] The start and end of the dead reckoning area or the dead reckoning mode can be identified, for example, by the positioning device and / or the (superordinate) system of the vehicle, especially by identifying the change in the positioning method and / or a significant reduction or increase in GNSS reception.

[0044] Furthermore, it can be proposed that the adaptation in step d) is implemented as follows: during a significantly reduced GNSS reception, load the determined second additional value to the integrity information.

[0045] For example, after entering the dead reckoning area and after the first duration has expired, calculate the protection level (PL) used as the integrity information according to the following formula:

[0046] PL(t) = sigma + delta

[0047] Here, delta is a second additional value and can be determined as follows:

[0048] Delta = PL_DR,a - sigma(a)

[0049] Here, PL_DR,a is the protection level value at the expiration of the first duration, and sigma(a) is the standard deviation of the position estimate at the expiration of the first duration.

[0050] Furthermore, it can be proposed that the adaptation in step d) is implemented as follows: during a suddenly and significantly increasing GNSS reception, the third additional value determined is loaded into the integrity information. In this case, the loading of the determined third additional value can be performed for a presettable third duration.

[0051] For example, when leaving the dead reckoning area or immediately after leaving the dead reckoning area, the (current) protection level (PL) used as an example for integrity information is calculated according to the following formula for a third duration:

[0052] PL(t) = sigma + D

[0053] Here, D is a third additional value and can be determined as follows:

[0054] D = PL_DR,zuletzt - sigma(t_zuletztDR)

[0055] Here, PL_DR,zuletzt is the last protection level value in the dead reckoning area, and t_zuletztDR is the last time in the dead reckoning area, such that sigma(t_zuletztDR) is the last standard deviation in the dead reckoning area.

[0056] Figure 2 Schematically shown is the exemplary positioning device 2 described herein in the vehicle 1. The positioning device 2 is arranged to perform the method described herein. The positioning device 2 is here, for example, a GNSS-INS positioning device.

[0057] When positioning with a GNSS-INS positioning device, it usually happens that: due to environmental obstacles or driving in a tunnel, the number of available GNSS signals decreases or is lost. This situation is usually referred to as the dead reckoning (DR) mode. Therefore, for calculating integrity information, such as the protection level (PL), it is advantageous to use a hybrid scheme in order to achieve a correct PL conversion when entering the DR mode, to obtain a reliable PL during the DR mode, and to achieve a correct conversion when leaving the DR mode.

[0058] The proposed method can advantageously contribute to the corresponding hybrid scheme in order to also maintain the integrity of the GNSS / INS-based positioning sensor in the DR module and / or contribute to the corresponding hybrid scheme when a sudden change in GNSS reception occurs from the normal state. In particular, the method can advantageously contribute to ensuring that the protection level does not experience meaningless and sudden changes even in the case of a sudden switch between the DR state and the normal state.

Claims

1. A method for adapting the protection level of a GNSS-based positioning device (2) of a vehicle (1), the method at least comprises the following steps: a) determining the current own position of the vehicle (1) by means of the GNSS-based positioning device (2), b) determining the protection level with respect to the own position determined in step a) by means of the GNSS-based positioning device (2), c) identifying a GNSS reception situation that is suddenly and significantly changing, d) adapting the determination of the protection level to the changing GNSS reception situation, wherein a sudden change is a change occurring within a time period of 60 seconds or less, and wherein a significant change is a change in the GNSS reception situation by at least 50%.

2. The method according to claim 1, wherein the adaptation in step d) is implemented as: attenuating and / or at least partially correcting the change that occurs due to the suddenly and significantly changing GNSS reception situation.

3. The method according to claim 1 or 2, wherein the adaptation in step d) is implemented as: during a suddenly and significantly decreasing GNSS reception, scaling the protection level by a scaling factor and / or loading the determined first additional value onto the protection level.

4. The method according to claim 3, wherein the scaling of the determined first additional value and / or the loading of the determined first additional value is performed for a preset first duration.

5. The method according to claim 1 or 2, wherein the adaptation in step d) is implemented as: during a significantly decreased GNSS reception, loading the determined second additional value onto the protection level.

6. The method according to claim 1 or 2, wherein the adaptation in step d) is implemented as: during a suddenly and significantly increasing GNSS reception, loading the determined third additional value onto the protection level.

7. The method according to claim 6, wherein the loading of the determined third additional value is performed for a preset third duration.

8. A computer program product for performing the method according to any one of claims 1 to 7.

9. A machine-readable storage medium, on which a computer program is stored, the computer program being configured to perform the method according to any one of claims 1 to 7.

10. A positioning device (2) for a vehicle (1), the positioning device (2) being configured to perform the method according to any one of claims 1 to 7.

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