On the Use of Robust Design Methods in Vehicle Longitudinal Controller Design

A robustness-based methodology for designing a vehicle longitudinal controller is presented. The resulting controller, which is intended for point-following operations, is applied to velocity-dependent (slowly varying) automobile dynamics. The results obtained effectively demonstrate how robust design methods may be applied to this class of dynamics. Further, similar approaches might be applied to controller designs for vehicles under different operating modes, e.g., under car-following operations. The design consists of a cascade compensator, which is selected to achieve small tracking errors, and an observer/controller compensator. Kharitonov-related robustness methods are used to design a fixed (constant coefficient) observer/controller, such that the resulting closed-loop pole-clusters are confined to an acceptable area of the s-plane. The performance of the resulting overall system is evaluated using a large-signal, entry merging command and some small-signal mainline commands. The results are comparable to ones obtained by utilizing more complex controllers based on parameter (gain) scheduling [1,2] and nonlinear design methods [3] and designed to achieve a velocity-invariant response.