Preview Control for Vehicle Lateral Guidance in Highway Automation

The continuous time deterministic optimal preview control algorithm is applied to the lateral guidance of a vehicle for an automated highway. In the lateral guidance problem, the front wheel steering angle of the vehicle is controlled so that the vehicle follows the center for a lane with small tracking error and maintains good ride quality simultaneously. A preview control algorithm is obtained by minimizing a quadratic performance index which includes terms representing the passenger ride quality as well as the lateral tracking error, each of these terms is multiplied by a frequency dependent weight. This design method is known as a frequency shaped linear quadratic (FSLQ) optimal control approach. It permits incorporating frequency domain design specifications such as high frequency robustness and ride quality in the optimal controller design. It is shown that the optimal preview control law consists of a feedback control term and two feedforward control terms. The feedback term is exactly the same as that of traditional LQ control algorithm. The feedforward preview control action significantly improves the tracking performance and ride quality. Frequency-domain analyses, as well as numerical simulation results, show the improvements achieved by using the preview control algorithm in both the frequency and time domains.