The goal of this research work was to determine if TV on the front axle can be used as a redundant steering concept. Both the simulation results and the vehicle tests show that the independent control of the longitudinal force on the front axle works very well to steer a vehicle. It was shown that the vehicle yaw behaviour changes and that the maximum lateral acceleration level is reduced. This change in yaw behaviour and limitation in lateral acceleration is very much dependent on the lever arms of the longitudinal and lateral force. The lower the ratio between the longitudinal and lateral force lever arm length, the more the vehicle will behave like the standard normally steered vehicle. If the ratio were zero, the steady state behaviour would be the same as the standard vehicle. Overall one can say that the concept works for standard vehicle lay-outs, but with a reduction of the maximum lateral acceleration. As a redundant steering concept for automated driving concepts on highways, where lateral dynamics are limited, the concept could work very well. In the case of redundancy for a steer by wire system, the suspension concept can be optimised for TV as during normal driving the longitudinal and lateral forces have no influence on the steering anymore. This way the overall vehicle concept can be designed such that the TV could fulfil all requirements on the redundant steering system for at least limp-aside concepts. The transition between normal steering and steering by TV still needs to be investigated in more detail. Since there are no clear requirements for this transition yet, these investigations need to be carried out on vehicle level. It remains to be investigated which concepts, other than single wheel drive concepts, can be used to sufficiently control the longitudinal forces on the front axle. Electronically controlled limited slip differentials might be an Option here. The influence of the discussed concept on tire wear has not been investigated, as this is not relevant for a redundant system. Overall it was shown that the concept opens up opportunities to optimise the overall vehicle concept for systems requiring a redundant steering system. Even for concepts without redundant steering, the steering by TV concept opens up opportunities to reduce the required performance of the steering system and optimise the vehicle control in case of a failure of the steering support.
Torque vectoring as redundant steering for automated driving or steer-by-wire
2014
15 Seiten, Bilder, 5 Quellen
Conference paper
English
Torque vectoring as redundant steering for automated driving or steer-by-wire
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