Dissertation

Integral Steering and Drive Module for Electrified Vehicles

Author:

Torben Dittmar

Pages:

162

DOI:

https://doi.org/10.18154/RWTH-2025-05208

Year:

2025

Language:

german

Format:

ebook

The ongoing automation and electrification of vehicles necessitates and facilitates the development of novel chassis systems. The advent of x-by-wire systems, which replace the mechanical connection of actuators and control elements by electronics, paved the way for the creation of highly compact, integrated chassis modules that encompass the functions of drive, steering, and braking. Such assemblies are also referred to as corner modules. A variety of variants of these modules have been developed by research organizations and industry. However, to date, a distinct actuator has been utilized for each of the functions of driving and steering the wheel. In order to optimize the system’s performance and reduce the size of the actuators, this thesis adopts and develops a concept based on an invention by Prof. Eckstein. This concept allows both actuators to be used simultaneously for driving and steering, rather than allocating them exclusively to a single task. In this novel concept, two electric actuators are positioned coaxially with the steering axis and connected to each other at the center of the wheel via bevel gears. The application of opposite torque by both actuators generates a driving torque, while torques in the same direction by both electric motors cause a torque around the steering axis. Furthermore, both load cases can be superimposed. Consequently, the maximum power output of both actuators can be allocated with a high degree of flexibility between the functions of steering and propulsion. This configuration enables an optimized adaptation of the actuator size to the maximum required system power. In view of the inherent dependency between steering and driving during operation, it is essential to implement a dedicated control mechanism.

In the context of this thesis, the primary challenges on physical, energetic and logical levels are considered in order to facilitate the realization of the concept. To this end, a dedicated simulation model has been developed. In addition, a prototype operated at 48V for the L7e vehicle class has been built and tested on the NVH test bench of ika.

The investigation of both artifacts demonstrates that the superposition of steering angle and drive torque can be achieved with sufficient accuracy and stability through the implementation of the new control concept. In order to ensure driving safety, the control system prioritizes the precision of steering angle over drive torque. Additionally, the implementation of a hollow shaft configuration facilitates the integration of the entire steering and drive module within a 14-inch wheel rim. Despite the large steering angles of over ±50°, movements of electrical wires can be minimized due to the option to establish connectors in the non-steering sections of the corner module, except for the wheel speed sensor and the brake.