The article contains results of research on the possibility of using an ultrasonic sensor in the sensor system of a mobile robot to determine the shape of the obstacle. The ultrasonic sensor has a wide beam aperture, i.e. large measuring angle (measuring angle -30°). Therefore, such a sensor allows only detecting an obstacle and determining a certain distance to him. But it is not known from which obstacle point the "echo" is received and it is not known to what part of the obstacle this distance is measured. The sensor cannot determine the shape of the obstacle because of low space resolution. For example, when a robot moves in a residential or office rooms, it would be desirable to identify obstacles such as "corners formed by walls" (internal or external) or "doorways" (with doors open or closed). A hypothesis was proposed that the use of scanning angular movements of the ultrasonic sensor will increase its resolution, required to determine the shape of the obstacle. The pivot-tilt mechanism was developed and assembled. The ultrasonic sensor attached on this computer-controlled mechanism and by algorithmic analysis of the data coming from the sensor during the scanning process, the form of the obstacle was recognized. Was found that using of algorithmic analysis is possible to determine the shapes of flat object, such as: "flat wall", "outer corner", "inner corner", "door opening with an open door", etc. This mechanism is expected to be used in the sensor system of a heterogeneous modular mobile robot.