Abstract
This paper describes the general hierarchical concept of the real time autonomous driving (Fig.1) and shows simulation results and also experiment results applied to the 4WD electric buggy vehicle. Based on a nonlinear single track model which describes the vehicle's driving dynamics, a path planning strategy is developed. A method for optimal control of nonlinear ODE is used to generate reference control values which are steering angle and driving forces that allow leading the vehicle alongside a calculated lane, which is optimal for different objectives, such as energy consumption, run time, safety or comfort characteristics. Also various constraints like width of the street or maximal lateral and longitudinal accelerations are taken into account. In this research work autonomous driving is based on a strict mathematic formulation and not rules based, which allows taking decision on undefined situation such as sudden change on road like a moving or fix obstacle.
By applying the optimal control solution to the vehicle, due to the disturbances, such as friction or side wind or unknown parameters and uncertainly in the model, the vehicle’s behavior does not match perfectly with the solution of the optimization. This is why, a path control level, in the form of lateral-longitudinal controller, is added to generate additional steering angle and driving force to compensate the error between reference and actual position of the vehicle. The operability of the system is shown and proved on simulation and some real driving experiments.
KEYWORDS – path planning, autonomous driving, optimal control, obstacle avoiding