自動車操舵系のロバスト制御

非線形H^∞状態フィードバックによるロバスト安定化

抄録

The dynamics of an automotive vehicle are designed to be stable in the usual situation. However, when the driving condition changes from moderate cornering on a dry road to hard cornering on a low friction road, the dynamics sometimes indicate unstable characteristics and in the worst case the vehicle will fall into a spin.
The purpose of this study is to design front steering control system which protects from vehicle spin. By, numerical analysis, it is shown that the unstabilization is raised by a bifurcation depending on a rear tire force saturation. Depending this observation, the tire force perturbation, caused by changes of road environments, is modeled by feedback plant perturbations. Then, a controller which compensates the instability against the perturbations is designed by nonlinear H_∞ control theory. Lastly, by computer simulations, the designed controller is shown to achieve robust stability and protect from vehicle spin.