Dynamic study of the passive safety of an active vehicle with Ansys LS-DYNA

CIXI is a start-up whose ambition is to make active mobility intelligent and environmentally friendly. To do so, it aims to reintegrate physical activity into daily commute. In order to build a more sustainable future, CIXI’s mobility solutions reduce the impact on the environment and improve the mental and physical health of users. The Vigoz is a vehicle that allows active travel with a low carbon footprint and the comfort of a car. Users can travel fast, safely, and in a weatherproof manner, while pedaling (up to 120 km/h) on roads previously reserved for cars. The Vigoz also offers a unique driving experience thanks to CIXI's pedaling and rolling technologies.

By using Ansys LS-DYNA, CIXI was able to quickly obtain valuable information on the performance of its products with respect to the normative framework to be complied with. The use of numerical simulation has also allowed for detailed optimization of parameters or shapes that would not have been possible if the development had been based solely on physical tests. Conducting crash tests with a dummy on board is very time-consuming and costly, but thanks to digital simulation, CIXI was able to carry out numerous crash tests using virtual dummies. This increased the number of designs tested and produced a more successful product at a lower cost. Without Ansys-LS-DYNA, the number of prototypes required would have resulted in much higher development costs and time-to-market. Ansys LS-DYNA has enabled CIXI to obtain an active vehicle with a highly satisfactory level of driver safety. Thanks to the start-up program, CIXI had access to a very broad product portfolio. The company has not only limited itself to crash applications. Instead, it has used simulation in several fields. This is the case, for example, for heat transfer issues or the use of topological optimization as a design aid. Within a company, integrating simulation into the product development process is not an easy task. CIXI was able to rely on CADFEM teams for training on the use of simulation and was also able to visit CADFEM engineers in various workshops to monitor their developments. They were also able to call on technical support to answer questions or exchange ideas about the methodology.

The meshing and data setting of the model are initially performed with the Ansys Mechanical tool. The integration of the dummy and the modeling of the belts are performed with the Ls-Prepost tool. Front and rear crash tests are performed. They allow the measurement of the vehicle's performance both from a structural point of view, such as intrusions, as well as from a biomechanical point of view, such as the measurement of the HIC. They also allow for dimensioning of the seat and belt anchorage points. Initially, front and rear crash cases are performed without the dummy being integrated into the vehicle. From these models, the performance of the vehicle structure and the accelerations undergone by the seat are measured. In a second step, a sled test sub-model, consisting only of the seat and the Hybrid III dummy, is performed. The seat accelerations are then applied to this sub-model. From this model, the biomechanical criteria can be established. It is also from this model that the performance of the seat can be observed and optimized. The forces induced by the crashes are measured and then used in static analyses to optimize the seat structure. The various dynamic simulations made it possible to correctly position the belt anchorages and observe the pretension forces. In addition, the criteria needed for approval were measured to determine whether the vehicle meets the requirements. Finally, the driver in this active vehicle is in a greatly reclined position, so the simulation was able to highlight a submarining phenomenon. From this observation, technical solutions were added to counter this undesirable phenomenon.