Development Process of the Multi-link Torsion Axle (MLTA) – A Space- Optimising Suspension for BEVs

The twist-beam axle is widely used in front-wheel driven battery electric vehicles (BEV) of the compact and subcompact segments. Since its cross beam requires major lateral and vertical design space, it is a limiting factor to the rear end of the battery package. Therefore, the goal of this work is to introduce a new rear axle concept, the so-called Multi-Link Torsion Axle (MLTA), that allows to relocate the transversal beam behind the rear wheel centers. This is done by using a reversed installation of a twist-beam axle and integrating it into a longitudinal Watt’s linkage. By doing so an increased and connected volume in the underbody of the vehicle is obtained which can directly be assigned to the battery design space. In this way, the available volume for the battery can be increased by almost 30% in comparison to the conventional twist beam axle. The usage of the Watt’s linkage also leads to the increased compliances. This paper shall introduce the new rear axle concept and its potential regarding the packaging of BEVs as well as the kinematic and elasto-kinematic design process to retain the advantages and tackle the downsides. In order to examine the performance of the suspension the research project “E-MLTA” was started in October 2018. The goal of this project is to develop the suspension concept based on the academical and industrial standards and later implement it into a small-sized passenger car.