Application Story
Democratizing NCAP scenarios for virtual test drives with ASAM OpenX
Summary
Euro NCAP provides descriptions of collision scenarios to test active safety systems of vehicles such as AEB. To conduct these tests in Simulation, the scenarios must be described in a machine-readable format. This application story sheds light on the capabilities of ASAM OpenSCENARIO XML and ASAM OpenDRIVE to be used to that extent. As the Euro NCAP scenarios are widely used, Vector decided to provide the implementation of these scenarios, which are based on ASAM standards, as open source at: github.com/vectorgrp/OSC-NCAP-scenarios.
Introduction
It is undisputed that the development and validation of complex ADAS functions require scenario-based testing as an essential component of the test strategy. Due to the high resource consumption of real-world test drives and the oftentimes late availability of technology carriers and prototypes in the development process, these test drives are increasingly conducted in a simulated manner. This process already begins in early development phases with model-based function design (MIL), continues through the implementation of functions as control unit code (SIL) and extends to testing with isolated but real target control units (HIL). It is desirable to reuse any test drive scenarios across all development phases and different execution environments as unchanged as possible. By defining input formats to compliant simulators, ASAM OpenSCENARIO and ASAM OpenDRIVE form the basis for this reusability. The relevant scenario catalog content can originate from various sources, including recorded test drives, accident databases, expert knowledge from function developers, or regulatory requirements. Euro NCAP, for example, provides descriptions of collision scenarios to test active safety systems of vehicles. Although these tests are not mandatory, you may as well regard them as regulatory requirements.
I am pleased to hear Vector publishes the Euro NCAP scenarios in the ASAM OpenSCENARIO XML format free of charge. Such activities foster the community trend for shift left testing with virtual test drives, which ultimately contributes to safer roads.
Richard Schram, Technical Director Euro NCAP
Motivation
As the ratings by Euro NCAP are of high importance for OEMs, the scenarios are well-accepted and widely used, both on real test tracks and in simulation. Simulations are not only carried out by the OEMs, but also by their suppliers. Furthermore, numerous simulators exist, many of them with proprietary scenario descriptions. Therefore, it must be suspected that a large number of implementations in various different formats has been created in the past, both by users of simulators and the tool providers alike. This, undoubtedly, has many disadvantages: duplicated efforts, non-reusable scenarios in proprietary formats and potential misinterpretations of the scenario definitions to name just a few. To alleviate these issues, we decided to comprehensively evaluate the suitability of the open standards ASAM OpenDRIVE and ASAM OpenSCENARIO for modeling various scenarios [1]. Specifically, the following aspects were examined:
- The use of ASAM OpenSCENARIO XML parameters to avoid proprietary pre-processing of simulation input data.
- The suitability of the ASAM OpenSCENARIO XML Synchronize Action for generating conflict situations under different initial conditions and parameters.
- The functional capabilities related to logical scenarios in ASAM OpenSCENARIO XML for parameter variations.
After the proof-of-concept implementation had proven ASAM OpenSCENARIO XML and ASAM OpenDRIVE capable of fulfilling these requirements, Vector decided to make its implementation of these scenarios available open source on Github [2]. You may use the QR code below to access the repository.
The goal is not only to avoid duplicate work, but also to foster discussions about the correct interpretation of both the standards and the scenario descriptions by Euro NCAP. It can be expected that this will directly lead to both time savings for the users and an increased quality of the standards.
Implementation using ASAM OpenSCENARIO XML, ASAM OpenDRIVE and ASAM MDF
Euro NCAP provides test protocols free of charge that contain the descriptions of the tests including the scenario definitions. These are made available as textual descriptions and sketches, but also tables with parameters that shall be varied, like the speed of the vehicle under test. Furthermore, assessment protocols are available that describe how to calculate the ratings after the test conduct. The scenarios that were implemented here concern the test of active safety systems, especially AEB systems. The used test protocols include collision scenarios with cars [3] and vulnerable road users [4]. The vehicle and environment simulator Vector DYNA4 [5] natively supports both ASAM OpenSCENARIO XML and ASAM OpenDRIVE as Simulation input formats. Hence, the implementation and Simulation of the scenarios was possible without any intermediate conversion to proprietary input formats. The findings of the implementation can be summarized as follows:
- NCAP static parts in ASAM OpenDRIVE
- Simple straight roads and symmetrical intersections allow for easy creation of matching ASAM OpenDRIVE descriptions.
- NCAP dynamic parts in ASAM OpenSCENARIO XML
- The ASAM OpenSCENARIO Synchronize Action is used for the behavior descriptions: It synchronizes the target entity’s arrival at a target position with the vehicle under test and was of great value to model the desired collision scenarios.
- Together with this action, the extensive usage of parameters was key to fulfill the goal of avoiding proprietary pre-processing.
- An apt choice of parameter definitions made it possible to translate the parameter tables from Euro NCAP directly into ASAM OpenSCENARIO XML variation files.
- NCAP assessment based on ASAM MDF results
- ASAM MDF is used for the recorded data, when simulating the scenarios in DYNA4.
- A Python-based reporting then automatically calculates the Euro NCAP ratings based on key performance indicators such as impact speed or collision avoidance.
The entire workflow from creation of the scenarios based on the Euro NCAP protocols up to the reporting is summarized in Figure 1.
During the implementation, a likely candidate for future standardization has been identified already: For scenarios in which the vehicle under test makes a turn at an intersection, Euro NCAP prescribes concatenated trajectories using straight, clothoid and arc elements. Such trajectories are supported by the latest ASAM OpenSCENARIO XML version 1.3. However, ASAM OpenSCENARIO XML uses the center of the rear axle as the control point for following trajectories, while Euro NCAP specifies the center of the front axle, which is a common reference coordinate system for vehicle dynamics Simulation. Until a feature supplement in the Standard is possible, a Standard-compliant but still proprietary controller property was introduced in DYNA4 to move the control point accordingly.
Conclusion
The standards ASAM OpenSCENARIO XML and ASAM OpenDRIVE proved to be capable of modelling the scenarios described by Euro NCAP for the assessment of active safety systems. The open-source publishing of this work will likely lead to fruitful discussions regarding the correct interpretation of both the standards and the scenario descriptions by Euro NCAP. In this way, we strive to foster the adoption of the standards within the community and further improve their quality.
[1] O.Funk, „Simulative Untersuchung automatisierter Notbremsfunktionen, Masterarbeit,“ Hochschulföderation SüdWest, 2024.
[2] Vector Informatik GmbH, „OSC-NCAP-scenarios,“ [Online]. Available: github.com/vectorgrp/OSC-NCAP-scenarios.
[3] Euro NCAP, Euro NCAP Test Protocol – AEB Car-to-Car systems, Implementation 2023, Version 4.3.1, 2024.
[4] Euro NCAP, Euro NCAP Test Protocol – AEB/LSS VRU systems, Implementation 2023, Version 4.5.1, 2024.
[5] Vector Informatik GmbH, „Euro NCAP: Test of AEB and FCW Functions with Virtual Test Drives,“ [Online]. Available: www.vector.com/ncap.
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