Robust Lateral Control of Heavy Duty Vehicles: Final Report
In this report, achievements under TO4201, "Robust Lateral Control of Heavy Duty Vehicles," are presented. The purposes of this project are: to design new controllers or redesign existing controllers for lateral control of heavy vehicles to improve performance; to evaluate designed controllers by experiments and to study autonomous vehicle following control. TO4201 is a continuation of MOU385, which makes it necessary to comment on the nature of the present report. Results on autonomous lateral control obtained under MOU385 (TO4201), was reported in the final report of MOU385, UCB-ITS-PRR-2001-35, and they are not part of the present report. It is noted that further research on autonomous lateral control is in progress under TO4233, "Fault Tolerant Autonomous Following Lateral Control for Heavy Vehicles." This report summarizes all types of nonlinear and adaptive controllers for lateral control of heavy vehicles and presents an experimental comparative studies of several control algorithms. The vehicle lateral control model is nonlinear and has two types of model uncertainties: dynamical nonlinear uncertainties and parametric uncertainties. To achieve robust stability as well as robust performance, various nonlinear robust control techniques such as sliding mode control, adaptive robust control, and robust nonlinear control based on feedback linearization are sought. To further improve robust performance, the dynamics of the steering subsystem is considered in the lateral controller design. In doing so, to account for the saturation and rate limit in the steering subsystem, a nonlinear loop-shaping approach is proposed. An analogy between the road disturbance to a vehicle lateral control system and the Coulomb friction to a mechanical system is observed. Based on this observation, two feedforward compensators are proposed which can be used in combination with linear robust controllers to further improve tracking performance of the linear feedback control systems. The sliding mode controller, a linear robust controller with feedforward compensation, and the same linear robust controller are implemented on a tractor-semitrailer combination and compared experimentally.