This paper presents a method for a design of a robot teleoperation system based upon their mixed-initiative interactions to realize the naturalistic collaboration between a human operator and a mobile robot with its autonomy At first we analyze a robot-teleoperating environment and classify its parameters into the four different classes of information after the Kirlik's Generalized Lens Model; framework: whether the operator and/or the robot can directly perceive the information or not, and whether they can directly manipulate the information or not. Based on this analysis, we develop an ecological interface system adopting a force-feedback-joystick as a device providing with a shared modality between a human operator and a robot's autonomy.