Autonomous driving system and method utilizing satellite positioning errors

Abstract

The goal is to enable safe GNSS use by calculating predictions of positional accuracy based on satellite configuration and understanding the impact of a reduction in the number of satellites in advance. [Solution] The autonomous driving system of the embodiment comprises a protection level calculation processing unit, a satellite availability determination unit, an alarm determination unit, and a display unit. The protection level calculation processing unit calculates the protection level, which is an index indicating the degree of position error due to positioning using satellite information acquired from GNSS satellites, using satellite information, map information, and traffic information relating to the traffic system that is autonomously driven by the autonomous driving system. The satellite availability determination unit uses the protection level, traffic information, and traffic system operation information to identify the time and location of movement of a moving object operated by the traffic system and determines whether the satellite is available. The alarm determination unit determines to issue an alarm if the determination result by the satellite availability determination unit does not match the prediction and monitoring. The display unit displays the determination result.

Description

[[Technical Field]]

[0001] Embodiments of the present invention relate to an automatic driving system and method that utilize satellite positioning errors. [[Background Art]]

[0002] In recent years, the utilization of position information using GNSS (Global Navigation Satellite System) has been expanding.

[0003] Monitoring of GNSS integrity is indispensable for safely operating drones and implementing automatic driving for railways, automobiles, and the like.

[0004] For aircraft, when using navigation based on GNSS, GNSS integrity is monitored by predicting and monitoring positioning accuracy. [[Prior Art Documents]] [[Patent Documents]]

[0005] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2023-93133 [[Patent Document 2]] Japanese Unexamined Patent Publication No. 2000-284830 [[Patent Document 3]] Japanese Unexamined Patent Publication No. 2019-15637 [[Patent Document 4]] Japanese Unexamined Patent Publication No. 2002-122652 [[Non-Patent Documents]]

[0006] [[Non-Patent Document 1]] ICAO International Standards and Recommended Practices Annex10 Aeronautical Telecommunications (SARPs)(2006 July Sixth Edition) [[Summary of the Invention]] [Problems that the invention aims to solve]

[0007] However, for drones flying at lower altitudes than aircraft, and for trains and cars operating near the ground, the number of visible satellites decreases due to the influence of buildings and other obstacles, and errors occur in location information due to multipath interference.

[0008] The accuracy of positioning using GNSS largely depends on the arrangement of satellites. When drones, trains, and automobiles utilize satellite positioning information, the receivers mounted on them perform positioning based on signals actually received from satellites, and the results are then used.

[0009] In this case, if the system suddenly enters an area with poor visibility during transit, or if the number of visible satellites decreases due to multipath effects, the positional accuracy may deteriorate rapidly. Therefore, conventionally, real-time control was required, such as detecting the deterioration of positional accuracy or monitoring the GNSS reception sensitivity and switching to autonomous operation when the sensitivity decreases. However, this switching method cannot provide stable operation in the face of intermittent changes.

[0010] The problem that this invention aims to solve is to provide an autonomous driving system and method that enables safe use of GNSS by calculating the prediction result of positional accuracy based on satellite configuration and understanding in advance the impact when the number of satellites decreases. [Means for solving the problem]

[0011] The embodiment is an automated driving system for a traffic system that utilizes satellite positioning errors, comprising a protection level calculation processing unit, a satellite availability determination unit, an alarm determination unit, and a display unit. The protection level calculation processing unit calculates a protection level, which is an index indicating the degree of position error due to positioning using satellite information acquired from GNSS satellites, using satellite information, map information, and traffic information relating to the traffic system that is automated by the automated driving system. The satellite availability determination unit uses the protection level, traffic information, and traffic system operation information to identify the time and location of movement of a moving object operated by the traffic system, and determines whether the satellite is available based on the identification result. The alarm determination unit determines to issue an alarm if the determination result by the satellite availability determination unit does not match the prediction and monitoring. The display unit displays the determination result by the satellite availability determination unit and the determination result by the alarm determination unit. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a block diagram showing an example configuration of an automated driving system to which the automated driving method of the embodiment is applied. [Figure 2] Figure 2 illustrates the calculation of the protection level by the protection level calculation processing unit. [Figure 3] Figure 3 is a diagram illustrating the level of protection provided by the aircraft. [Figure 4] Figure 4 illustrates the alarm determination process performed by the alarm determination unit. [Figure 5] Figure 5 illustrates areas along railway routes where satellite service is unavailable. [Figure 6] Figure 6 illustrates an example of setting thresholds for each area where the required positional accuracy changes in an aviation system. [Figure 7] Figure 7 illustrates an example of setting thresholds for each area where the required positional accuracy changes in a railway system. [Figure 8]FIG. 8 is a diagram illustrating an example of reducing the risk of changes after the start of operation by utilizing prediction results regarding the availability of GNSS satellites in an aviation system. [Figure 9] FIG. 9 is a diagram illustrating an example of reducing the risk of changes after the start of operation by utilizing prediction results regarding the availability of GNSS satellites in a railway system. [Figure 10] FIG. 10 is a diagram illustrating an example of promptly responding when it becomes clear that there is an obstacle to the continuation of automatic driving of an aviation system due to a failure of a GNSS satellite or the like. [Figure 11] FIG. 11 is a diagram illustrating an example of promptly responding when it becomes clear that there is an obstacle to the continuation of automatic driving of a railway system due to a failure of a GNSS satellite or the like. [Figure 12] FIG. 12 is a diagram illustrating an example in which the satellite availability determination unit predicts the position accuracy during an operation time period by performing prediction with a specified elevation angle for a railway system. MODE FOR CARRYING OUT THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as those in reality. Furthermore, even when the same portion is represented, the dimensions and ratios may be different depending on the drawing. In the present specification and each drawing, the same reference numerals are given to elements that are the same as those described in the preceding drawings, and detailed descriptions and repeated descriptions are appropriately omitted.

[0014] FIG. 1 is a block diagram showing a configuration example of an automatic driving system to which the automatic driving method according to the embodiment is applied.

[0015] The automatic driving system 10 according to the embodiment is an automatic driving system 10 that utilizes satellite positioning errors, and includes a protection level calculation processing unit 12, a satellite availability determination unit 14, an alarm determination unit 16, and a display unit 18.

[0016] The protection level calculation processing unit 12 uses satellite information s, map information a, and traffic information b to calculate the protection level (positional accuracy) A at any given point. For example, when applying the automated driving system 10 to a railway system, any given point corresponds to a station or any point on the railway track.

[0017] Satellite information s is provided by a GNSS receiver 22 that receives satellite information s from a GNSS satellite 20. The GNSS receiver 22 is located outside the autonomous driving system 10, but may be integrated into the autonomous driving system 10.

[0018] Map information a includes map a1 and altitude a2.

[0019] Traffic information b is information about a traffic system that is automatically driven by the automated driving system 10. A traffic system includes, for example, railways and airplanes. In this example, we will use a railway as an example of a traffic system. In this case, traffic information b will be station and track information, including location information for stations and tracks. Therefore, in the following example, we will assume that traffic information b is station and track information.

[0020] Map information (a) and station and track information (b) can both be obtained from servers accessible via the internet, etc. Alternatively, station and track information (b) may be obtained from the railway company.

[0021] Protection level A is an index that indicates the degree of positional error due to satellite information s from GNSS satellite 20, depending on the satellite configuration, etc., and it is an index that indicates the deterioration of positional accuracy in the event of a failure of GNSS satellite 20. Conceptually, protection level A can be thought of as the range that includes 99.999999% of the positional error (positioning error).

[0022] The protection level calculation processing unit 12 can calculate the protection level (positional accuracy) A at any point on the station and railway line as a prediction and monitoring result using the number of visible satellites that take the terrain into consideration, by using satellite information s, map information a, and station and railway line information b.

[0023] Figure 2 illustrates the calculation of the protection level by the protection level calculation processing unit.

[0024] The protection level calculation processing unit 12 calculates the protection level (positional accuracy) A by, for example, calculating the angle (θ) at which the GNSS satellite 20 becomes visible at the protection level calculation point d from the terrain information c, as shown in Figures 2(a) and 2(b), and then obtaining a conservative calculation result by calculating with a marginal angle (θ+dθ).

[0025] The example shown in Figure 2(b) illustrates that GNSS satellite 20(#3) is not used in the calculation because its angle is less than or equal to θ (1) it is not visible; GNSS satellite 20(#2) is not used in the calculation because its angle is greater than or equal to θ but less than or equal to (θ+dθ), and although it should be visible, it may not be reliably visible (not visible); and GNSS satellite 20(#1) is used in the calculation because its angle is greater than or equal to (θ+dθ) and it is reliably visible.

[0026] In this way, the protection level calculation processing unit 12 can easily revise the safety margin by using dθ as a parameter in the calculation of protection level A. Furthermore, by installing GNSS receivers 22 at important points, satellite information s from GNSS satellites 20 at those points can be monitored and reflected in the calculation of protection level A. The conservative calculation results obtained in this way enable the safe operation of the railway.

[0027] Furthermore, the calculation of protection level A, as mentioned above, can be performed based on different concepts depending on the traffic system. The following describes the protection levels for aircraft used in aviation systems.

[0028] Figure 3 is a diagram illustrating the level of protection provided by the aircraft.

[0029] As illustrated in Figure 3, in the case of aircraft, if the Horizontal Protection Level (HPL) is greater than the Horizontal Warning Criticality (HAL), the aircraft cannot fly along an air route using satellite navigation. The Horizontal Protection Level (HPL) is calculated by multiplying the "magnitude of the observation error" by the "satellite configuration in which the observation error occurred." Here, the "magnitude of the observation error" is a parameter (probability) based on the number of satellites, and the "satellite configuration in which the observation error occurred" is the degree of influence (geometry) of the error due to the satellite configuration. Thus, in the case of aircraft, the probability of the aircraft being outside the protection level is 10 -7 The following applies.

[0030] The satellite availability determination unit 14 uses the protection level A calculated by the protection level calculation processing unit 12, station and track information b, and operation information d to identify the time and location of the train's movement. Based on the identification result, it determines whether satellite use is possible and creates a determination result B.

[0031] Station and track information b includes location information for stations and tracks, as described above.

[0032] Operational information d includes the train's scheduled operating time d1 and the required position accuracy d2. In the case of aircraft, the scheduled operating time d1 and the required position accuracy d2 become the aircraft's scheduled operating time d1 and the required position accuracy d2. Operational information d can also be obtained from servers available via the internet, etc. Alternatively, operational information d may be obtained from the railway company.

[0033] The satellite availability determination unit 14 generates determination result B on a per-operation basis. An operation is basically defined as the period from the starting point to the destination.

[0034] The alarm determination unit 16 determines that if the determination result B created by the satellite availability determination unit 14 does not match the prediction and the monitored result, and there is a difference, it will issue an alarm and sound a buzzer, for example, D, as an alarm. It also outputs this determination result E.

[0035] Figure 4 illustrates the alarm determination process performed by the alarm determination unit.

[0036] Figure 4(a) shows the determination result (prediction) B1 created by the satellite availability determination unit 14, and Figure 4(b) shows the determination result (monitoring) B2 created by the satellite availability determination unit 14. The parts β1, β2, and β3 shown in the determination result (monitoring) B2 are different from the determination result (prediction) B1. In this way, if a difference occurs between the prediction and the monitoring, the alarm determination unit 16 performs an alarm determination, sounds a buzzer D, and outputs the alarm determination result E.

[0037] The display unit 18 displays the determination result B created by the satellite availability determination unit 14 and the alarm determination result E determined by the alarm determination unit 16.

[0038] Next, we will describe an example using the autonomous driving system 10 with this configuration.

[0039] (Example 1) In Example 1, the satellite availability determination unit 14 uses DOP (Dilution Of Precision) to determine whether a satellite is available for use. The DOP of the GNSS satellite 20 is a numerical value that represents the degree of degradation of GPS positioning accuracy, and is affected by the position of the GNSS satellite 20; a smaller value indicates higher accuracy.

[0040] By pre-planning to avoid using GNSS satellite 20 in areas with poor DOP values, we can ensure that positional accuracy remains unaffected even if it deteriorates due to sudden deterioration in visibility, multipath effects, satellite failures, etc.

[0041] For vehicles operating on fixed routes, such as railways, stable operation is ensured by implementing autonomous control in advance in areas where GNSS satellite 20 is unavailable.

[0042] Figure 5 illustrates areas along railway routes where satellite service is unavailable.

[0043] Figure 5 shows the same judgment result (monitoring) B2 as in Figure 4(b), and β1, β2, and β3 are the parts that differ from the judgment result (prediction) B1. Of these, part β3 is (1) the satellite unusable area estimated from the DOP value. In addition, (2) tunnels are examples of areas that are known to be unusable in advance.

[0044] DOP can be calculated using the line-of-sight vector matrix G obtained from the elevation and azimuth angles of the GNSS satellite 20 at the observation point, using the RAIM algorithm and the SBAS protection level calculation algorithm. Specifically, for example, the following formula is described in Appendix B 3.5.5.6 of Non-Patent Document 1.

[0045]

number

[0046] Using this, the line of sight vector G is calculated, and further the line of sight vector G is expressed by the following formula

[0047]

number

[0048] By substituting these values, the DOP can be calculated.

[0049] (Example 2) In Example 2, the satellite availability determination unit 14 determines whether the GNSS satellite 20 is available for use by identifying the operational area of ​​the GNSS satellite 20. The operational area of ​​the GNSS satellite 20 is identified using a threshold value set for each area where the required position accuracy d2 changes.

[0050] A concrete example will be explained using Figure 6.

[0051] Figure 6 illustrates an example of setting thresholds for each area where the required positional accuracy changes in an aviation system.

[0052] In the case of aviation systems, on wide air routes, as shown in Figure 6(a), the allowable positional error is large, so it is not necessary to set a strict precision to avoid collisions. Therefore, a threshold of, for example, 2 NM (nautical mile) can be used. On the other hand, on densely packed routes near airports, as shown in Figure 6(b), it is necessary to set a strict precision to avoid collisions. Therefore, a strict threshold of, for example, 0.1 NM can be used.

[0053] Figure 7 illustrates an example of setting thresholds for each area where the required positional accuracy changes in a railway system.

[0054] In railway systems, as shown in Figure 7(a), the allowable positional error is large between stations, so it is not necessary to set a strict precision for braking to avoid collisions. Therefore, a threshold of, for example, a few meters can be used. On the other hand, near stations, as shown in Figure 7(b), it is necessary to set a strict precision to avoid collisions. For this reason, a strict threshold of, for example, several tens of centimeters can be used.

[0055] (Example 3) Example 3 describes how the risk of changes after the start of operations can be reduced in a transportation system by utilizing prediction results regarding the availability of GNSS satellites 20.

[0056] Figure 8 illustrates an example of how the use of prediction results regarding the availability of GNSS satellites in an aviation system can reduce the risk of changes after the start of operations.

[0057] In aviation systems, the risk of changing the flight plan after takeoff can be reduced by using forecast results to confirm the availability of GNSS satellites for the flight before takeoff.

[0058] Figure 9 illustrates an example of how the risk of changes after the start of operations can be reduced in a railway system by utilizing prediction results regarding the availability of GNSS satellites.

[0059] In railway systems, the risk of plan changes during operation can be reduced by using prediction results to confirm the availability of GNSS satellites 20 for automated driving before commencing operations. Furthermore, it becomes possible to pre-determine and have a driver H on board to perform manual driving in sections F where automated driving is not possible.

[0060] (Example 4) In Example 4, if the Satellite Availability Determination Unit 14 determines whether the GNSS satellite 20 is available, and it becomes clear that there is a problem preventing the continuation of autonomous driving, such as a failure of the GNSS satellite 20, the traffic system will take prompt action.

[0061] Figure 10 illustrates an example of prompt action to be taken when it becomes clear that the continuation of autonomous flight operations of an aviation system is being hindered due to a GNSS satellite failure or other reasons.

[0062] (1) If it becomes clear that the continuation of autonomous flight will be hindered due to a malfunction of GNSS satellite 20 (#3) or the like, the aviation system will (2) update the forecast results and (3) revise the flight plan.

[0063] Figure 11 illustrates an example of prompt action to be taken when it becomes clear that the continued operation of the automated railway system is being hindered due to a GNSS satellite failure or other reasons.

[0064] (1) If it becomes clear that the continuation of automated operation will be hindered due to a failure of GNSS satellite 20 (#3), the railway system will (2) update the prediction results, (3) stop the train, switch to remote operation, etc., and (4) revise the subsequent plan.

[0065] (Example 5) In Example 5, we will describe an example in which the satellite availability determination unit 14 predicts the positional accuracy during the operating time period by specifying the elevation angle and making a prediction.

[0066] Figure 12 illustrates an example in which the satellite availability determination unit 14 predicts the positional accuracy during operating hours for a railway system by specifying the elevation angle and making predictions.

[0067] In this embodiment, as shown in Figure 12, the satellite availability determination unit 14 calculates the elevation angle that can secure the number of NGSS satellites 20 necessary to obtain the required positional accuracy, and determines the optimal elevation angle from the multipath information collected in advance.

[0068] The satellite usability determination unit 14 determines that automatic operation is possible if (optimal elevation angle) ≤ (threshold), and determines that automatic operation is not possible if (optimal elevation angle) > (threshold). The threshold is set to an angle where the effect of multipath cannot be ignored.

[0069] Before applying the automated driving system 10 of the embodiment, the positional accuracy when receiving satellites at an arbitrary elevation angle could not be determined without actually checking the reception strength. However, after application, as described above, it became possible to predict the positional accuracy during operating hours by specifying the elevation angle and making a prediction.

[0070] As explained above, an automated driving system to which the automated driving method of the embodiment is applied can calculate the predicted position accuracy based on the satellite configuration and, by understanding the impact of a decrease in the number of satellites in advance, enable safe use of GNSS.

[0071] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0072] 10. Autonomous driving systems 12 Protection Level Calculation Processing Unit 14 Satellite availability determination unit 16 Alarm detection unit 18 Display 20 GNSS satellites 22 GNSS receivers A Protection Level a Map information a1 Map a2 altitude B Judgment result B1 Judgment Result (Prediction) B2 Judgment result (monitoring) b Track information, traffic information c Terrain information D Buzzer sound d Operation information d1 Operating hours (scheduled) d2 Required position accuracy E Alarm result F Sections where automatic driving is not permitted G View vector H Driver s Satellite information

Claims

1. An automated driving system for a transportation system that utilizes satellite positioning errors, A protection level calculation processing unit calculates a protection level, which is an index indicating the degree of position error due to positioning using satellite information acquired from GNSS satellites, using the satellite information, map information, and traffic information relating to the traffic system that is automatically driven by the automatic driving system. A satellite availability determination unit determines whether the satellite is available or unavailable, using the aforementioned protection level, the aforementioned traffic information, and the aforementioned traffic system operation information to identify the time and location of a moving object operated by the traffic system, and based on the identification result, determines whether the satellite is available or unavailable. If the determination result by the satellite availability determination unit does not match the prediction and the monitoring, the alarm determination unit determines to issue an alarm. An autonomous driving system equipped with [the following features].

2. The automatic driving system according to claim 1, further comprising a display unit that displays the determination result from the satellite availability determination unit and the determination result from the alarm determination unit.

3. The automated driving system according to claim 1, wherein the satellite availability determination unit determines the availability of satellites using DOP (Dilution Of Precision).

4. The automated driving system according to claim 1, wherein the satellite availability determination unit sets a threshold for each area where the required position accuracy changes, identifies an operational area for the satellite based on the threshold, and determines whether the satellite is available for use based on the operational area.

5. The satellite availability determination unit calculates the elevation angle that can secure the number of satellites necessary to obtain the required positional accuracy, determines the optimal elevation angle from the multipath information collected in advance, and compares it with a threshold angle at which the influence of the multipath cannot be ignored. If (optimal elevation angle) ≤ (threshold), it is determined that the traffic system can operate autonomously. The automated driving system according to claim 1, wherein if (optimal elevation angle) > (threshold), it is determined that automated driving of the traffic system is not possible.

6. The aforementioned transportation system is a railway system, The aforementioned moving object is a railway vehicle, The aforementioned traffic information includes information regarding stations and tracks of the railway system, The automated driving system according to claim 1, wherein the operational information includes the operating time and required position accuracy of the railway vehicle.

7. The aforementioned transportation system is an aviation system, The aforementioned moving object is an aircraft. The aforementioned traffic information includes information on airports and sea routes, The automated driving system according to claim 1, wherein the operational information includes the flight time of the aircraft and the required position accuracy.

8. An automated driving method implemented by an automated driving system for a traffic system that utilizes satellite positioning errors, The aforementioned automated driving system The protection level, which is an index indicating the degree of position error due to positioning using satellite information acquired from GNSS satellites, is calculated using the satellite information, map information, and traffic information relating to the traffic system that is automatically driven by the autonomous driving system. Using the protection level, the traffic information, and the traffic system operation information, the time and location of a moving object operated by the traffic system are identified, and based on the identification result, a first determination is made to determine whether the satellite is available. An automated driving method that determines to issue an alarm if the result of the first determination does not match the prediction and the monitoring.

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