Lateral guidance of an autonomous vehicle by a fuzzy logic controller

This study is the fruit of cooperative research between Renault and the Fuzzy Logic Group at the University of Technology of Compiegne. Emphasizing the driver´s comfort, our main objective was to design and tune an active driver assistance enabling and ensuring automatic guidance, while at any time allowing the driver to take over control of his vehicle. A fuzzy logic controller (FLC) has been developed and implemented on a Renault Safrane, ensuring transversal control of the car. An on-board CCD camera, connected to an image processing unit, delivers the specific data required for the guidance controller. The FLC processes these data and generates a set point of steering wheel torque which is delivered to a classic PI regulator controlling an electric motor implanted in the steering column of the prototype. Simulation results show the convergence, over a large range of longitudinal speeds, between the trajectory output of a vehicle model-controlled by the FLC-and the reference trajectory to be followed: the controller is also robust to any perturbation such as gusts of wind or violent swerves of the wheel. Currently, experimental tests on road yield satisfactory results: the FLC generates a nonoscillating smooth and comfortable trajectory in hands-off driving situations, while it arouses a real feeling of trust and helpfulness when the driver keeps his hands on the steering wheel. An ergonomics study carried out concurrently will enable us to refine our copiloting system