What sensors will be used in solving this problem?

Suppose you do a preliminary research on a robot system design. This robot is similar to iRobot Roomba. On the top of the robot there are a series of buttons used for basic buttons will send the robot out to clean. On the bottom are wheels designed to navigate carpet, on the bottom side are bristles in order to sweep the floors sides are sensors that can search for walls, objects that would obstruct its path, and virtual walls set up by the user. When it is finished cleaning or the battery runs low it will navigate back to its charging station to recharge