The robot should be able to assess its location in order to move to a specific location to carry out its command. It plans its path, taking into consideration the location of an obstacle, and moves itself by biped walking or wheeling. To measure its location, a StarGazer sensor system is used. A landmark is printed with a pattern reflecting an infra-red light and is attached to the ceiling. The landmark plays the role of an independent coordinate system with an identity number. The StarGazer consists of an infra-red beam emitter and an infra-red image camera. Generally, the sensor system is equipped on the head of the robot. It analyzes the infra-red image of the pattern on the ceiling and calculates its position and the heading angle of the robot.