Abstract
Research and/or Engineering Questions/Objective
In-wheel motors (IWMs) are an interesting alternative to central, on-board electric drives. This type of distributed electric drive system offers a multitude of advanced driver assistance systems based on vehicle dynamics as well as a vast amount of possibilities for overall vehicle design. It is therefore necessary to solve several conflicts of objectives regarding the design of electric powertrain and chassis. These conflicts of objectives focus on functional integration aspects and especially on designed space usage inside and close to the wheel. There are manifold concepts and prototypes of these so-called active corner modules, which showcase various subsystem configurations for precise applications. However, general approaches focusing on scaling and different subsystem configurations to explore further applications have not been presented yet.
Methodology
An interdisciplinary design methodology for different subsystem configurations is presented. It allows an overall evaluation of active corner modules in early stages of development and is the basis for a detailed design of the various subsystems of the active corner modules. The methodology starts off with the "basic configuration" of an active corner module, which has been designed as a parametric model of IWM and wheel brake for both direct and geared drives. Suitable suspension kinematics are adapted subsequently and active chassis systems can be supplemented if necessary. An extensive evaluation concept for the quality of kinematic values based on MBS and full vehicle simulation is presented.
Dimensioning of the wheel brake got a special status within the methodology, as the wheel brake does not only provide essential safety functions, but its layout also limits the leeway for design of the IWM and suspension.
Results
Based on the cross-system design methodology for active corner modules, exemplary configurations are shown and evaluated automatically. The capability of the chosen approach is verified by virtual prototypes. Focus is on a newly developed wheel brake of perimeter design, which copes with the specific requirements in active corner modules and features distinct advantages over conventional wheel brake designs of spot type disc brakes. Validation of the concept is carried out by extensive simulations and dynamometer test runs with a newly developed wheel brake prototype.
Limitations of this study
To represent broad scaling of electric wheel hub drives (IWM + gear), the IWM dimensioning is limited to basic calculation approaches for permanent magnet excited synchronous machines of inner rotor type. The machine concepts have not been optimized in detail for precise applications.
What does the paper offer that is new in the field including in comparison to other work by the authors?
The possibility to evaluate a wide range of configurations of active corner modules regarding their properties and technical feasibility is an extensively new approach. In addition to earlier publications, the modular construction system of the wheel brake has been reworked and the design has been considerably improved. Thus, designed space for IWM and suspension can be increased while simultaneously improving performance, lightweight design and energy efficiency.
Conclusions A method is presented which allows systematic configuration and dimensioning of chassis systems for active corner modules for various application scenarios. In particular, a novel, highly integrated wheel brake system is presented, which can be used as a universal modular construction system.
KEYWORDS : perimeter brake, in-wheel motor, active corner module