Target trajectory generation using clothoid curve and vehicle control for obstacle avoidance of automated driving

Abstract

In order to avoid an obstacle automatically for an automated vehicle, this paper investigated a method to generate a target trajectory using a clothoid curve and to control the vehicle. Although a mathematical constraints or a potential methods are often used to generate the target trajectory for an obstacle avoidance, it requires trial and error and experience, and it is also necessary to consider the vehicle’s drivability. The clothoid curve is often used for a road curve design, therefore, the curve is considered to be suitable for the characteristics of a vehicle driving. Although a clothoid curve passing through a target point is necessary for obstacle avoidance, such clothoid curve is often obtained by trial and error. Therefore, the numerical analyses were executed to obtain the characteristics of the clothoid curve, then, the method was investigated to generate the clothoid curve to pass through the target point. Furthermore, a method to generate a target avoidance trajectory was also investigated expanding the generated clothoid curve based on the traveling characteristics of a vehicle. For driving on the target trajectory satisfactory, both the position and turning angle of the vehicle are controlled by means of a steering manuplation. The controller was constructed using a 1-input 2-output system, therefore, it is very difficult to satisfy both value at the same time. Furthermore, it is also necessary to consider a nonholonomic characteristics of the vehicle. From these point, this paper investigated the optimal control using nonlinear least square probrem sequential quadratic programming(NLSSQP) by means of the time behaviour of input and output in the evaluation value. Well expected results are obtained and shown in the simulation and the experiment.

Keywords

• autonomous vehicle
• obstacle avoidance
• clothoid curve
• optimum control
• nonlinear least squares method