K.-K. Shin and S.-K. Chen (USA)
Vehicle and transportation systems, adaptive control, parameter estimation, active front steering, variable gear ratio
In this paper, the performance of active-front steering (AFS) system is enhanced by adapting the variable gear ratio (VGR) to changes in vehicle parameters, such as understeer coefficient. The parameter changes can be caused by low tire pressure, worn-out tire, different loading, suspension aging, etc. Vehicle dynamics parameters are estimated by using a real-time vehicle parameter estimation technique. The adaptation strategy is to maintain the steering sensitivity of nominal vehicle regardless of the understeer coefficient change. This strategy effectively maintains steering sensitivity in yaw rate response. Even with the limited authority of AFS, the strategy does not have adverse effect on lateral velocity response. An adaptive VGR control algorithm is then proposed and analyzed, and non-linear simulation is performed to show its effectiveness.
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