Search Results

A nonlinear 8 degree-of-freedom (DOF) four wheel automobile model and a multi-loop quasi-linear driver model were used to investigate both conventional front wheel (FWS) and four wheel steering (4WS) automobiles during (a) crosswind disturbances and (b) collision avoidance maneuvers resulting from combined steering and braking commands. Two different 4WS control laws were used. The first was an open loop control law (OL4) where the rear wheel steer angle was determined by the front wheel steer angle. The second was a closed loop law (CL4) where the rear wheel steer angle was determined by both the front wheel steer angle and the vehicle yaw rate. Both of these linear control laws were proposed by previous investigators and were originally developed using 2 DOF linear “bicycle” models. These linear control laws were modified for application to the situations described above.