static public Vector2D compute_dipole_vector(Vector2D object, Vector2D robot, Vector2D goal){

		Vector2D object_to_goal = new Vector2D(object, goal);
		
		double angle = Vector2D.get_angle_signed_PI(object_to_goal, new Vector2D(object, robot));
		Vector2D x_vec = Vector2D.normalize(object_to_goal);
		Vector2D y_vec = Vector2D.rotate90(x_vec);

		// computing "a" ( move cautiously when the object is near the goal)
		double angleROG_ = Vector2D.get_angle_PI(new Vector2D(object, robot), new Vector2D(goal, object));
		double angleORG = Vector2D.get_angle_PI(new Vector2D(robot, object), new Vector2D(robot, goal));
		double a = angleROG_ / angleORG;
		if (angleORG == 0 || angleROG_ == 0)
			a = 1;
		if (a>10)
			a=10;
		
		double cos = Math.cos(angle);
		double sin = Math.sin(angle);
		Vector2D vec = Vector2D.add(Vector2D.multiply(x_vec,  cos*cos - a*sin*sin), 
									Vector2D.multiply(y_vec, -sin*cos - a*sin*cos));

		// orbit when the robot is in front of the object
		Vector2D object_to_robot = new Vector2D(object, robot);
		object_to_robot.normalize();
		if (Vector2D.dot_product(vec, object_to_robot)>0){
			if (Vector2D.cross_product(vec, object_to_robot) == 0)
				vec = Vector2D.rotate90(vec);
			else
				vec.subtract(Vector2D.multiply(object_to_robot, Vector2D.dot_product(vec, object_to_robot)));
		}
		
		return vec;
	}