Safety package protects small electric vehicles

September 26, 2014 // By Christoph Hammerschmidt
Efficient subcompact vehicles with electric propulsion are regarded as a valid option in making electromobility more popular. However, vehicles of the "Quad class" (official term: L7E) currently only offer an insufficient safety level. Researchers from the Visio.M consortium now have demonstrated that - and how - even small and lightweight electric vehicles can offer adequate safety.

In crash tests according to the Euro-NCAP standard, light vehicles of the admission category LE7 (which have an empty weight of less than 400 kg) exhibited significant deficiencies. In particular in crash situations with heavier vehicles, even the LE7 subcompacts must provide a safe compartment, regardless of their small size. For the near-series research subcompact vehicles Visio.M, introduced earlier this year, the designers of the Munich Technical University implemented a rigid passenger compartment, made of carbon fibre reinforced plastics along with high-strength aluminium structures.

The high rigidity of the passenger compartment however leads to smaller chassis deformation length. This translates into high forces acting to passengers in the case of an accident. The Visio.M developers counteract with an integrated safety concept based on sophisticated recognition of the surrounding traffic by means of radar and camera-based sensors, resulting in a 360° surround monitoring of the vehicle's environment.

This system is capable of detecting critical traffic situations and imminent collisions early. Case it senses an imminent and unavoidable crash, it activates the passenger protection systems even before the actual impact. A critical component in this strategy are so-called structural airbags integrated into the vehicle. These consist of pressure hoses located in the bumpers and the lateral vehicle lining. Fractions of a second before the impact, a gas generator fills the hoses, pushing the lateral panels outwards and places itself as an additional absorption layer between outer skin and vehicle structure. Thus, the forces stressing the passengers are reduced by adaptive seat-belt tensioners and force limiting systems. An additional safety belt inside the vehicle holds passengers in their seats.

As an additional measure in side collisions, the passenger seat on the impact side is pulled towards the center of the car a split second before the crash. This moves the passenger out of the immediate danger zone. Furthermore the pre-acceleration also reduces the impact force on the passenger. An airbag between the seats