Safe Trajectory Selection for Autonomous Vehicles

Abstract

A method to select one trajectory, the so-called Selected Trajectory (ST), out of a set of trajectories (T1-T3) to be used by an autonomous or semi-autonomous ground vehicle (GV), wherein the method includes the following steps: (i) assessing said set of trajectories (T1-T3) with one, two, or a multitude of verification modules (VM1-VM4) and returning Quality Assessments (Q11-Q43) for each of the trajectories (T1-T3); (ii) ranking said trajectories (T1-T3) with a Ranking Scheme (RS), wherein the Quality Assessments (Q11-Q43) are taken into account when ranking the trajectories (T1-T3), and (iii) selecting exactly one trajectory, the Selected Trajectory (TR), based on the rank of the trajectories (T1-T3).

Claims

1. A method to select one trajectory, the so-called Selected Trajectory (ST), out of a set of trajectories (T1-T3) to be used by an autonomous or semi-autonomous ground vehicle (GV), the method comprising the following steps: assessing said set of trajectories (T1-T3) with one, two, or a multitude of verification modules (VM1-VM4) and returning Quality Assessments (Q11-Q43) for each of the trajectories (T1-T3); ranking said trajectories (T1-T3) with a Ranking Scheme (RS), wherein the Quality Assessments (Q11-Q43) are taken into account when ranking the trajectories (T1-T3); and selecting exactly one trajectory, the Selected Trajectory (TR), based on the rank of the trajectories (T1-T3).

2. The method according to claim 1, wherein the set of trajectories (T1-T3) is generated by two or more Trajectory Generators (TG1, TG2, TG3).

3. The method according to claim 2, wherein each Trajectory Generator of the two or more Trajectory Generators (TG1, TG2, TG3) generates one or more of the trajectories of the set of trajectories independently from the other Trajectory Generators.

4. The method according to claim 1, wherein all Trajectory Generators are diverse, in that each of the Trajectory Generators uses different algorithms for generating trajectories then the other Trajectory Generators and/or each Trajectory Generator is implemented on different hardware.

5. The method according to claim 1, wherein a Decision Maker (DM) is provided, which ranks the trajectories (T1-T3) and/or selects the exactly one Selected Trajectory (ST).

6. The method according to claim 5, wherein for ranking with the Decision Maker (DM), other input (IN) for selecting the Selected Trajectory (ST) is taken into account, in that the Decision Maker (DM) takes said other input into account when ranking the trajectories (T1-T3) using the Ranking Scheme (RS).

7. The method according to claim 5, wherein locally stored information (INF) is taken into account when selecting the Selected Trajectory (ST), in that the Decision Maker takes said locally stored information (INF) into account when ranking the trajectories (T1-T3) using the Ranking Scheme (RS).

8. The method according to claim 1, wherein the Ranking Scheme (RS) is static.

9. The method according to claim 1, wherein the Ranking Scheme (RS) is dynamic, in that it changes based on the input (IN).

10. The method according to claim 1, wherein each verification module (VM1-VM4), for assessing the trajectories (T1-T3), is adapted to execute at least one test on the trajectories, wherein the at least one test is one of the following tests: Collision Probability Test, CPT Vehicle Dynamics Test, VDT Vehicle Stability Test, VST Legality and Regulations Test, LRT Comfort and Convenience Test, CCT Energy Efficiency Test, EET User-defined Preferences Test, UPT.

11. The method according to claim 1, wherein the Ranking Scheme (RS) distinguishes between Safety-Relevant Verification Modules (S-VM) and Non-Safety-Relevant Verification Modules (N-VM), and wherein a Decision Maker (DM) by using the Ranking Scheme (RS) selects as Selected Trajectory (ST) a trajectory (T1-T3) with the best safety rank (SR1-SR3).

12. The method according to claim 11, wherein in the case that two or more trajectories (T1-T3) have equal safety ranks (SR1-SR3), the Decision Maker selects by use of the Ranking Scheme (RS) out of said trajectories with equal safety rank a trajectory with the highest non-safety rank (NR1-NR3).

13. The method according to claim 12, wherein in the case that two or more trajectories (T1-T3) have equal safety rank (SR1-SR3) and equal non-safety rank (NR1-NR3), the Decision Maker (DM) by use of the Ranking Scheme (RS) and a Tie Breaker (TB) selects a Selected Trajectory (ST).

14. The method according to claim 13, wherein the Tie Breaker (TB) is an identifier of the Trajectory Generator (TG1-TG3) of the respective Trajectory (T1-T3), or derived from locally stored information (INF), or derived from other input (IN).

15. A Selected-Trajectory selecting-device (STS) for selecting one trajectory, the so-called Selected Trajectory out of a set of trajectories (T1-T3), which Selected Trajectory (TR) is to be used by an autonomous or semi-autonomous ground vehicle (GV), wherein the Safety-Trajectory-selecting device comprises one, two, or a multitude of verification modules (VM1-VM4) and a Decision Maker (DM), wherein the Safety-Trajectory-selecting device is adapted to execute a method according to claim 1.

16. A Selected-Trajectory generating-device (STG), comprising: two or more trajectory generators (TG1, TG2, TG3), which are adapted to generate the set of trajectories (T1-T3) and a Selected-Trajectory-selecting device (STS) according to claim 15, for selecting one trajectory, the Selected Trajectory (ST), out of the set of trajectories generated by the trajectory generators (TG1, TG2, TG3).

17. The Selected-Trajectory generating-device (STG) according to claim 16, wherein each of the trajectory generators (TG1, TG2, TG3) is adapted to generate one or more of the trajectories of the set of trajectories independently from the other Trajectory Generators.

18. The Selected-Trajectory generating-device (STG) according to claim 16, wherein all Trajectory Generators are diverse, in particular in that each of the Trajectory Generators uses different algorithms for generating trajectories than the other Trajectory Generators and/or wherein each Trajectory Generator is implemented on different hardware.

19. A vehicle comprising the Selected-Trajectory selecting-device (STS) according to claim 15.

20. The vehicle of claim 19, wherein the vehicle is an autonomous or semi-autonomous ground vehicle (GV).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0053] In the following, in order to further demonstrate the present invention, illustrative and non-restricting embodiments are discussed, as shown in the drawings, which show:

[0054] FIG. 1 an example of a vehicle implementing a Selected-Trajectory selecting-device, and

[0055] FIG. 2 an example of an inner structure of a Selected-Trajectory selecting-device.

DETAILED DESCRIPTION

[0056] We discuss some of the many implementations of the invention next. If not stated otherwise, all details described in connection with a specific example are not only valid in connection with this example, but apply to the general scope of protection of the invention.

[0057] FIG. 1 depicts an example of an autonomous or semi-autonomous ground vehicle GV implementing three Trajectory Generators TG and a Safe Trajectory Selection STS, which may be part of a Selected-Trajectory generating-device STG. The Trajectory Generators TG generate trajectories T1-T3. The Safe Trajectory Selection STS selects a trajectory as Selected Trajectory ST. This Selected Trajectory ST is safe and the best trajectory with respect to a Ranking Scheme RS. The Selected Trajectory ST is used by the vehicle GV to manoeuvre, for example on a highway, or in urban or sub-urban environment.

[0058] FIG. 2 depicts an example of an inner structure of a Safe Trajectory Selection STS. The Safe Trajectory Selection STS receives as an input trajectories, for examples the trajectories T1-T3 from the Trajectory Generators TG1-TG3 according to FIG. 1, and preferably other inputs IN, as for example: [0059] Vehicle State information (velocity and/or acceleration and/or direction and/or tire friction and/or steering angle, etc.), and/or [0060] Map Data, and/or [0061] Trajectory Generator Diagnostics.

[0062] Furthermore, the Safe Trajectory Selection STS may have locally stored Information INF as well, as for example information about the Automotive Safety Integrity Level (ASIL) of the respective Trajectory Generators TG1-TG3, and/or diagnostics data on the operational history of the Trajectory Generators TG1-TG3, and/or other information, which may be used for selecting the Selected Trajectory ST.

[0063] The Safe Trajectory Selection STS further implements one or more Verification Modules, in this example four Verification Modules VM1-VM4. The Verification Modules VM1-VM4 are configured to implement tests on the trajectories T1-T3. Said tests on said trajectories T1-T3 return Quality Assessments Q11-Q43, wherein said Quality Assessments Q11-Q43 are indicating the quality of each of the trajectories T1-T3 in terms of said tests.

[0064] Preferably, each Verification Module implements a different test on one, two or preferably all trajectories.

[0065] For example, [0066] Verification Module VM1 implements a test that is executed on each trajectory T1-T3 and said test executed in VM1 returns for each trajectory a Quality Assessment, Quality Assessment Q11 for trajectory T1, Quality Assessment Q12 for trajectory T2, and Quality Assessment Q13 for trajectory T3; [0067] Verification Module VM2 implements a test that is executed on each trajectory T1-T3 and said test executed in VM2 returns for each trajectory a Quality Assessment, Quality Assessment Q21 for trajectory T1, Quality Assessment Q22 for trajectory T2, and Quality Assessment Q23 for trajectory T3; [0068] Verification Module VM3 implements a test that is executed on each trajectory T1-T3 and said test executed in VM3 returns for each trajectory a Quality Assessment, Quality Assessment Q31 for trajectory T1, Quality Assessment Q32 for trajectory T2, and Quality Assessment Q33 for trajectory T3; [0069] Verification Module VM4 implements a test that is executed on each trajectory T1-T3 and said test executed in VM4 returns for each trajectory a Quality Assessment, Quality Assessment Q41 for trajectory T1, Quality Assessment Q42 for trajectory T2, and Quality Assessment Q43 for trajectory T3.

[0070] The Safe Trajectory Selection STS selects a trajectory as Selected Trajectory ST from the trajectories T1-T3 generated by the Trajectory Generators TG1-TG3. In general, each Trajectory Generator generates one or more trajectories independently of the other Trajectory Generators. In the specific example, Trajectory generator TG1 generates trajectory T1, Trajectory generator TG2 generates trajectory T2, and Trajectory generator TG3 generates trajectory T3.

[0071] The selection is executed in a Decision Maker DM. The Decision Maker DM uses the Quality Assessments as returned by the tests in the Verification Modules VM1-VM4, and optionally other input IN (as described above), as well as optionally locally stored information INF for the purpose of selecting of the one Selected Trajectory ST. For this selection process, the Decision Maker DM encodes a Ranking Scheme RS according which the Decision Maker DM ranks the trajectories T1-T3. Thus, this Ranking Scheme RS uniquely identifies the best safe trajectory out of the set of trajectories T1-T3.

[0072] The Safe Trajectory Selection STS returns said best trajectory as output as Selected Trajectory ST. Said Selected Trajectory ST is typically a safe trajectory or the best safe trajectory under the assumptions mentioned in the beginning.

[0073] Example tests of Verification Modules VM1-VM4 are as follows: [0074] Collision Probability Test CPT: the test assesses the likelihood that the vehicle GV would collide with an obstacle when maneuvering along the trajectory T1-T3 under test. [0075] Vehicle Dynamics Test VDT: the test assesses how accurately the vehicle GV can follow the trajectory T1-T3 under test. [0076] Vehicle Stability Test VST: the test assesses the likelihood that the vehicle GV becomes unstable from a control theory perspective when following the trajectory T1-T3 under test. [0077] Legality and Regulations Test LRT: the test assesses the likelihood that the vehicle GV adheres to configured legal rules (e.g., maximum speeds, minimum distance to other vehicles, behaving in accordance with street signs) when following the trajectory T1-T3 under test. [0078] Comfort and Convenience Test CCT: the test assesses how comfortable the movement of the vehicle GV appears to a passenger when said vehicle GV follows the trajectory T1-T3 under test. [0079] Energy Efficiency Test EET: the test assesses the energy efficiency of the vehicle GV moving along the trajectory T1-T3 under test. [0080] User-defined Preferences Test UPT: the test assesses whether the vehicle GV adheres to user-defined restrictions (e.g., maximum speed limits preferences set by a user, maximum acceleration preference set by a user, other preferences).

[0081] In the following we give some example embodiments of Ranking Schemes RS. The Verification Modules VM1-VM4 are preferably of different criticality. For example the Verification Module implementing a Collision Probability Test CPT is more critical than the Verification Module that is configured to implement a Comfort and Convenience Test CCT, because a low Quality Assessment Q11-Q43 of a trajectory by the Collision Probability Test CPT means a high probability of collision of the vehicle GV with an obstacle, while a low Quality Assessment of a trajectory by the Comfort and Convenience Test CCT does not compromise the safety of vehicle passengers. Thus, in one embodiment the Ranking Scheme RS distinguishes between Safety-Relevant Verification Modules S-VM and Non-Safety-Relevant Verification Modules N-VM.

[0082] In one embodiment the Verification Modules VM1-VM4 are statically defined as Safety-Relevant Verification Modules S-VM and Non-Safety-Relevant Verification Modules N-VM for the duration of a complete mission of a vehicle GV.

[0083] In one embodiment the distribution of the Verification Modules VM1-VM4 into Safety-Relevant Verification Modules S-VM and Non-Safety-Relevant Verification Modules N-VM may change during the mission of a vehicle GV. It may be provided that said distribution changes during the mission of a vehicle GV depending on inputs IN that the Safe Trajectory Selection STS receives. Based on said inputs IN, the Safe Trajectory Selection STS may differentiate between driving scenarios, e.g., highway driving vs. parking vs. urban or suburban driving. Thus, the Safe Trajectory Selection STS may change the classification of the Verification Modules VM1-VM4 into Safety-Relevant Verification Modules S-VM and Non-Safety-Relevant Verification Modules N-V in response to changing driving scenarios.

[0084] It may be provided that the Safe Trajectory Selection STS normalizes the Quality Assessments Q11-Q43 to ranges, e.g. to a values RACT in a range between a minimum value R.sub.MIN and a maximum value R.sub.MAX.

[0085] It may be provided that the Safe Trajectory Selection STS normalizes two or more, preferably all Quality Assessments Q11-Q43 to the same range.

[0086] It may be provided that the Safe Trajectory Selection STS is configured to implement configurable weights W.sub.ACT, within an interval of a minimum weights W.sub.MIN and maximum weights W.sub.MAX, for Quality Assessments Q11-Q43. It may be provided that the interval of configurable weights [W.sub.MIN, W.sub.MAX] is identical for two or more, in particular for all Quality Assessments Q11-Q43.

[0087] It may be provided that the configured weights W.sub.ACT are static for the duration of a complete mission of a vehicle GV.

[0088] It may be provided that the configured weights W.sub.ACT change during the mission of a vehicle GV. The configured weights W.sub.ACT may change during the mission of a vehicle GV depending of the inputs IN that the Safe Trajectory Selection STS receives. Based on the inputs IN, the Safe Trajectory Selection STS may differentiate between driving scenarios, e.g., highway driving vs. parking vs. urban or suburban driving. Thus, the Safe Trajectory Selection STS may change the configuration of the weights W.sub.ACT in response to changing driving scenarios.

[0089] The Ranking Scheme RS defines Ranking Procedures on how to calculate a Trajectory Rank TR1-TR3 for a respective Generated Trajectory T1-T3. The Safe Trajectory Selection STS selects the Trajectory T1-T3 with the best Trajectory Rank TR1-TR3 as the Selected Trajectory ST. In the following we discuss some examples of Ranking Procedures.

[0090] In one embodiment the Ranking Procedure RP is realized as follows: [0091] For each Trajectory T1-T3 the Ranking Scheme calculates a Safety Rank SR1-SR3. The Safety Rank SR1-SR3 may be calculated as follows (where Qji represents the Quality Assessment of Trajectory Ti, of a Verification Module VMj that is classified as Safety-Relevant Verification Module S-VM):

SRi=Sum(W.sub.ACT*Qji), [0092] For each Trajectory T1-T3 the Ranking Scheme calculates a Non-Safety Rank NR1-NR3. The Non-Safety Rank NR1-NR3 may be calculated as follows (where Qki represents the Quality Assessment of Trajectory Ti, of a Verification Module VMk that is classified as Non-Safety-Relevant Verification Module N-VM):

NRi=Sum(W.sub.ACT*Qki), [0093] The Safe Trajectory Selection STS is configured to select as Selected Trajectory ST the trajectory T1-T3 a Trajectory T1-T3 with the highest value of Safety Rank SR1-SR3. In case when there are more than one Trajectories T1-T3 with equal Safety Ranks SR1-SR3, the Safe Trajectory Selection STS is configured to select as Selected Trajectory ST out of the more than one Trajectories T1-T3 with highest Safety Rank SR1-SR3, the one or more Trajectories T1-T3 with highest Non-Safety Rank NR1-NR3. More than one Trajectories T1-T3 have equally highest Safety Ranks SR1-SR3 and equally highest Non-Safety Ranks NR1-NR3, then the Safe Trajectory Selection STS is configured to select out of said Trajectories T1-T3 with equally highest Safety Rank SR1-SR3 and equally highest Non-Safety Rank NR1-NR3, a Trajectory T1-T3 in accordance with a Tie Breaker TB.

[0094] This Tie Braker TB can be for example: [0095] the identifier of the Trajectory Generator TG1-TG3 of the respective Trajectory T1-T3; [0096] derived from locally stored information INF; [0097] derived from the other input IN to the Safe Trajectory Selection.