AD ready: Future occupant protection

The EU “Vision Zero” target aims to reduce the road traffic fatalities to almost zero until the year 2050. The consumer test program Euro NCAP contributes to this vision with the “Roadmap 2025”, where automated driving functions promise to play a major role in protecting vehicle occupants and vulnerable road users (VRU). Advanced driver assistant systems (ADAS) also need to prove their performance, just as restraint systems and structural safety measures need to do already. Hereby, especially automated emergency braking (AEB) functions for VRUs will be monitored in the upcoming testing procedures. This includes interurban situations and cyclists as well as autopilot function. The Euro NCAP Roadmap 2025 supports the development and testing efforts by industry and research organizations.

Challenges for occupant protection

From the viewpoint of occupant protection, ADAS will allow people, to sit in new, more comfortable positions with different geometric conditions. Although the overall goal of these systems is to completely avoid accidents at all, vehicles still need to fulfill passive safety requirements. For the development of the necessary restraint systems, the established methods and tools (e.g. Crash Test Dummies) are not fully appropriate any more. There is the need to detect different injury mechanisms due to new load directions on the occupant compared to former sitting positions.

Therefore, measurement and development tools (Crash Test Dummies, Human Body Models, – HBMs) need to be further developed. VIRTUAL VEHICLE for example improves and extends human body models (HBMs). These models can depict internal organs, bones and individual muscles. HBMs do not exist in the physical world, rather they are virtual computer simulations. That allows a much more accurate injury assessment than common crash-test-dummies.

Further advantages of HBMs are:

• Scalable (e.g. elderly people, obese persons) à larger variety of the society can be considered
• Muscle activity can be implemented à realistic occupant model response in pre-crash activities

This is necessary for the realistic occupant kinematic analysis in pre- and in-crash and for injury risk assessment.

Mastering the amount of simulations: The SAFETY TOOL CHAIN (ViF)

The possible combinations of ADAS lead to different occupant kinematics in pre-crash situations. That results in a high number of initial positions for the in-crash simulation. Therefore, an effective overall simulation for pre- and in-crash is necessary, to rate the integral measures which are taken for occupant protection. Figure 2 shows the approach developed by VIRTUAL VEHICLE, which seamlessly connects the different discipline-specific simulation tools enabling a totally integrated virtual accident assessment

This enables the detailed study of the vehicle behavior from ordinary driving to in-crash in a large number of critical situations in a consistent manner for active, passive and integrated protection systems.

The main element is the automated, continuous SAFETY TOOL CHAIN (ViF) for all accident phases. By taking different sub-models covering all relevant components a complete transition from the simulation of the pre-collision phase to the collision can be achieved. Each model is valid for its purpose and the (patented) synchronized combination of these models opens the way for a complete paramatrized system simulation.  Typical components include:

• Sensors and algorithms of the protection systems
• Occupant, belt strengthener, airbag, ECU
• Environment, especially visual obstructions
• Vehicle and VRU mechanical behavior: Vehicle dynamics models during pre-crash, multi body system (MBS) models and finite element (FE) models during in-crash. The transition between simulation tools is fully automated in that each accident party’s state is transferred and used as a starting condition by the subsequent model.

Finally, this approach achieves:

• Short calculation times by using surrogate models
• Efficiency analysis of different parameters (ADAS, restraint systems, ..)
• Co-Simulation covers comprehensively the complete accident scenario (from activating the ADAS up to the in-crash phase)

Current research topics

Research projects at VIRTUAL VEHICLE include:

• Pre- and -In-crash simulation with SAFETY TOOL CHAINVIF
• Active HBM development
• Future restraint system development

Currently, these topics are adressed of the following projects:

• EU H2020 funded project OSCCAR deals amongst others with the further development of HBMs for the challenges of automated driving and new sitting positions, while striving to enable virtual testing and even homologation. www.osccarproject.eu
• COMET K2 funded projects like OM4IS and Precooni provides data about the occupant kinematic in low-g driving and pre-crash maneuvers.
• COMET K2 funded, internal strategic project a completely new controller is developed to implemented re-active pre-crash behavior in HBMs.