This paper proposes models of short-range sensors. The target application is the simulation of the environment perception for an autonomous biped robot that evolves in an unknown surroundings. These proximity sensors can be of different types, emulating real sensors such as laser range finders, ultrasonic sensors or reflectance sensors. These sensors will be used to provide real-time local information about the environment to the robot in a simulation. Strategies to avoid an circumvent an obstacle can then be easily tested.