Abstract
The attention of governments, car manufacturers and customers has moved to alternative energy sources and innovative powertrains due to factors like fluctuating oil prices and a stronger public and politic interest for the environment. From the actual point of view, the conversion of electrical into mechanical energy seems to be a promising approach for future powertrains.
In-wheel motors are a very interesting alternative for the electrification of vehicles. Beside environmental aspects it also provides a wide range of potentials to improve vehicle dynamics and the vehicle’s driving behavior in general. However there are some open questions related with them, like the effects of the increased unsuspended masses, failure handling, cooling as well as the integration of electrical and mechanical components (electric motor, gearbox, brake system, suspension arms) within the rim.
An innovative approach for the mechanical integration of in-wheel motors in several common single wheel suspension systems (e.g. McPherson, double wishbone, multilink, control blade) is presented in this paper. The developed algorithm is based on a co-simulation between Matlab® and CATIA V5®. Matlab® is used as master for the control of the entire optimization process and for the interaction with the user. The suspension system kinematics is depicted using the kinematics module of CATIA V5®. The starting point of the entire process is a simplified CAD-model of the suspension system in which the in-wheel motor should be integrated. The behavior of the desired characteristic suspension parameters is determined in the first step. Afterwards simplified geometries representing the in-wheel motor are added to the CAD-model. At this stage, first collision problems can be visually identified. The next step corresponds to a fully automated optimization routine aiming to find the position of the suspension hardpoints for which the behavior of the characteristic suspension parameters (e.g. camber, toe, roll center position, scrub radius) remains as close as possible to that of the original suspension. This reduces the influence on the vehicle’s driving behavior and on comfort aspects related with the suspension system. At the same time, collisions should be detected by the algorithm and avoided during the suspension movement (bound/rebound and steering). A gradient based optimization process is used. Because each step during the optimization cycle can be visualized in CATIA V5®, the user can track the development of the entire process and has therefore full control over it.
Keywords: In-wheel motors, single wheel suspension systems, synthesis of suspension systems