A microprocessor-based, vehicle lateral controller

A velocity-adaptive lateral controller was designed to meet requirements pertaining to lateralposition tracking accuracy, ride comfort, and an insensitivity to both changes in critical vehicle parameters and disturbance forces. This controller was implemented using a 16-bit microcomputer (which was based on an Intel 8086 microprocessor) and installed in a dual-mode test vehicle. The controller/vehicle combination was evaluated under field conditions at the Transportation Research Center of Ohio. A wire-follower configuration was employed to provide both a lateral reference and a lateral position error (ΔSf). The vehicle was automatically steered on straight sections of roadway at speeds up to 35.8 m/s, and small-radius (100-m) curves were traversed at speeds up to 17.9 m/s. Excellent lateral control -- close tracking (|ΔSf| < 0.07m on curved sections), a comfortable ride (aRMS< 0.2 m/s²), and a good insensitivity to disturbance forces-- resulted. The selected control algorithm, which involved an inverse compensation stage for velocity-independent performance and a lead/lag stage for both good tracking and ride comfort, was realized using some 10 percent of the available computation time. Thus, the microcomputer could also be employed for such tasks as vital function monitoring (e.g., oil pressure, alternator output and engine temperature), and serve as a source of intelligence on-board the vehicle. The latter could be especially important in reducing the response time to various emergencies.