EXPLORE THE POSSIBILITIES
A family of virtual humans accelerate road safety certification
The digital twin helps save lives on the road
Will there ever be zero deaths in road accidents? Nearly 20% of all road accident fatalities in the EU are pedestrians. Head injuries pose the greatest threat of all so reducing them saves many human lives. Accordingly, the WHO and EU require vehicle designs to pass tests that measure the impact to the head in a collision.
If a vehicle design allows more space between the engine parts and the cover, it provides a crush space and reduces the risk of serious injuries. However that can spoil the aerodynamics and aesthetics of the design. The active hood concept solves this design dilemma. It raises the hood instantly if the vehicle hits a person. Global mobility engineering experts, EDAG, aim to rethink and redesign mobility. Combining engineering expertise with a high degree of innovation and an understanding of future technologies, Stefan Hundertmark’s team, has been using advanced simulations to model a design for an active hood, and found they could perform more accurate safety testing in the virtual world.
Safety demands tough certifications
As with all new vehicle designs, the active hood must pass the stringent the European New Car Assessment Program (Euro NCAP) safety requirements. Euro NCAP has particularly tough safety standards and to gain certification for the active hood, EDAG had to prove with certainty that the hood would always be fully raised before it strikes a pedestrian, so that it fully protects the person from the engine parts below.
This was the challenge facing Hundertmark’s specialist CAE and Safety department at EDAG. They could not test the concept in the real world because it would destroy many prototype cars, so they performed the tests in a virtual environment. This needed an accurate simulation that would mimic the behavior of the human body at the exact moment of impact.
The need for time efficient simulations
EDAG uses simulation models for testing because they can be completed early in the design cycle, and this helps its customers to bring new designs to market faster. However, the simulations for the active hood were taking time because they needed to show an accurate model of the behavior of a human body at the moment of impact. Hundertmark explains: “The old software worked but the simulations took a long time to run because the models were so complex.”
Hundertmark calculates: “From the first contact with the pedestrian until the head hits the hood is around 40 to 50 milliseconds. Within that time, the sensor must send the signal to the CPU that determines if it is a pedestrian and then send another signal to the mechanism that activates the pop-up hood.” This meant that the simulation needed to be exceptionally fast, which is why Hundertmark decided to use Simcenter Madymo. “Because we are dealing in milliseconds, the response times are critical. Simcenter solutions offered us multi-body modeling with the detail of finite elements and CFD to achieve that.”
Modeling kinematic behavior
Simcenter Madymo provides multibody dynamics, finite element method (FEM) and computational fluid dynamics (CFD) all in one solution with an extensive and validated human body model (HBM) database. It also gave the team better tools and support for simulating complex models of human bodies. This meant that the team could simplify their models and simulate just the parts of the body they were interested in, which made a huge difference in the processing times. Hundertmark explains:
“With Simcenter Madymo we can model just the kinematics and that’s all we need to verify that a pedestrian has been hit and send the signal to activate the hood in time. Owing to its multibody capability, the Simcenter Madymo analysis is much faster than with the previous finite element pedestrian HBMs. It meant that we got the results in a matter of hours instead of days.”
Simcenter Madymo made the simulations much easier. Hundertmark’s team found they were able to perform more simulations, complete their testing sooner and shorten the development time. The software is intuitive and it helped the team to perform the series of tests more easily. He explains: “The requirements for dummy positions and the different angles needed for certification are very strict. With Simcenter Madymo it’s much easier to handle and adapt the dummy as needed. The speed of the simulations also allows us to process more iterations faster so we reach the optimum design much sooner. Ultimately this helps our customers to produce a better product at a lower cost, which is the most important thing to them.”
A compliant and accepted family of human body models
As prescribed by the Euro NCAP regulations, Simcenter Madymo provides an entire family of HBMs: a large male, an average male, a small female and a six-year-old child. Vehicles need to be tested with all of the models so the set of certified HBMs replaces the traditional crash dummies.
Euro NCAP’s specifications for virtual crash dummies are particularly tough, so the engineers from Siemens Digital Industries Software have to ensure that their HBMs fully comply with Euro NCAP’s validation requirements so that simulation results will be accepted. Importantly, the Simcenter Madymo virtual family does meet the Euro NCAP Technical Bulletin (TB024 protocol) specifications, so they can be used in simulations for safety system analysis certification.
More accurate simulation, safer roads
EDAG Group’s use of advanced simulations puts them right at the forefront of vehicle design. Some manufacturers are still using physical crash dummies, but EDAG and Siemens are confident that the wider automotive industry will follow EDAG’s example. Siemens’ software engineers are already working on a joint industry roadmap and proposals to bring more HBMs into the software-based simulations that lead to certifications, and they have presented these to Euro NCAP and the other relevant authorities. It is only a matter of time until the proposals will be ratified and adopted which will move safety testing to the next level.
What is the future of vehicle design? Hundertmark believes that the ultimate goal in road safety is “Vision Zero”, which aims to end traffic-related fatalities and injuries by taking a systemic approach to road safety and minimizing the risks in the driving environment. When autonomous vehicles arrive on the roads they should make a difference, and there should be fewer accidents but there will always be the risk of hitting a pedestrian. Hundertmark believes that as vehicles change, pedestrian and occupant protection will evolve too, and simulation will overtake the old tests and play an even greater role to play in road safety. He says: “Safety authorities such as Euro NCAP have realized that the virtual models perform truer to life than physical dummies. We’ll see more testing projects shift from physical to virtual simulation because it gives more accurate results.”