Konzeptionierung und kinematische Optimierung einer Mehrlenkertorsionsachse für den Einsatz in einem batterieelektrischen Fahrzeug

In this thesis, the concept of a new type of rear axle, the so-called multi-link torsion axle, is developed. By integrating a reversed twist-beam structure into a longitudinally orientated Watt’s linkage, the position of the space-limiting cross beam is decoupled from the original longitudinal instant centre. This opens up an increased, homogenous package space in the vehicle underbody, which can be allocated to the traction battery when used in a battery electric vehicle. At the same time, a longitudinal instant centre in front of the wheel, and thus also positive anti-lift, can be ensured by the alignment of longitudinal links in side view.
Once the basic topology of the mechanism has been defined, it is optimised regarding the hardpoints. For this purpose, multiple analytical calculation approaches of the motion are presented and then integrated into an optimisation algorithm. The hardpoints are optimised with respect to global and local package boundary conditions, as well as kinematic and elastic requirements and target values. These refer to typical suspension characteristics found in literature, as well as characteristics that can occur specifically with the given mechanism.
The resulting properties are then compared with a conventional twist-beam axle at both the suspension and full-vehicle level. For this purpose, this new type of rear axle is installed in a demonstrator vehicle loaded with ballast masses and tested on a proving ground. Full-vehicle simulations are also used for better interpretation. These experiments focus particularly on the vertical dynamic properties of the new axle with respect to comfort for different road excitations as well as pitching under braking. The results obtained also allow conclusions to be drawn about the previously defined suspension characteristics. With the results of this test series, it is possible to conclude whether the new axle concept is within a tuneable range in terms of driving dynamics.