Abstract: Provided is a small mobile robot which moves back and forth and left and right while keeping its posture by two main wheels. The small mobile robot includes built-in auxiliary wheels to overcome topographical elevation differences. The auxiliary wheels of the small mobile robot are attached to a servomotor. The servomotor is driven by remote control, and the auxiliary wheel can be moved to the position required for operation. When the robot is in a normal state, the auxiliary wheels are retracted in the robot. When the robot meets a stepped topography, the auxiliary wheels are lowered out to contact a ground to support the main wheels going over the stepped topography. The small mobile robot includes a sensor for sensing obstacles and a control module to make a detour around obstacles while moving to a target point.