The Institute for Automotive Engineering at RWTH Aachen University (ika) is currently developing, constructing, and implementing the research vehicle SpeedE as an open research and innovation platform for research and industry. The research focus f the SpeedE concept, amongst other things, is the innovative front suspension. Not only is the front axle's steer-by-wire system able to steer each wheel individually, but it is also able to achieve steering angles of up to 90°. These requirements lead to an unconventional setup of the axle replacing the tie rod and the rack and pinion steering gear of a double wishbone suspension by two steering actuators consisting of an electric motor and a strain wave reduction gear located at the outer kinematic hardpoint of the upper control arm and mounted to the wishbone through a cardan joint. This article firstly explains the virtual design process of the SpeedE research vehicle's front axle and secondly compares the achieved characteristics of the first prototype with the results of the virtual design. Especially the innovative topology of the front axle and the high steering angle demands from -60° to 90° at the wheel requires special solutions for the design and construction of the front axle. For this purpose the orientation of the lower control arm is inverted so that the comfort bushing is positioned in front of the dynamic bushing in the direction of travel. Furthermore, the steering axis is designed so that the camber angle remains below 10° for large steering angles and on the other hand the torque about the steering axis is low because of the lateral and longitudinal forces. In addition to the configuration of the steering axis, the orientation of the cardan joint in the upper control arm has an enormous influence on the toe angle progression while wheel travel. After determining the kinematics and elasto-kinematics, the prepared components are integrated into the MBS-Simulation as flexible bodies to ensure that a highly sophisticated model is used and the requirements are met. The characteristics of the first prototypes are determined on the kinematics and compliance test rig at the Institute for Automotive Engineering at RWTH Aachen University. For this, the wheel alignment changes during wheel travel and during the introduction of longitudinal and lateral forces are captured by two cameras that optically measure the changes.
The wheel-individually steerable front axle of the research vehicle "SpeedE" - virtual design and achieved performance of the first prototype
2014
28 Seiten, Bilder, 7 Quellen
Conference paper
English
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