The authors are developing a model-based remote maintenance robot system which autonomously carried out maintenance tasks in nuclear facilities: for example, nuclear power plants and nuclear fusion reactors. In this paper, two measurements methods for the robot system are described: one is a laser range finder which is popularly used, and the other is a groping method to target tasks which are to insert a bolt and set a nut. These measurements are indispensable for autonomous robots. In the groping method, the arm with a bolt gropes on the flange surface, and a rapid change in the force signal is detected when the bolt tip comes across a hole. Position measurements are made by the joint angles in groping. Therefore, it has the same merit as direct teaching in industrial robots. The robot system carried out inserting a bolt and setting a nut on a flange by using these methods.