Abstract— This paper deals with the optimization of RobotObstacle interaction computations, in the context of nonholonomic trajectory deformation for mobile robots. We first recall the principle of the trajectory deformation and the role of the potential field gradient in the configuration space. The contribution of the paper is twofold. First we show that the potential field gradient can be computed without any closed-form expression of the potential function if this latter depends only on the distance between the robot and the obstacles. Then an algorithm to filter obstacles that have no influence in Robot-Obstacle interactions is presented. This algorithm takes advantage of the spatial coherence of the planned trajectory, and has been evaluated by experiments on mobile robot Hilare2 towing a trailer.