Wheeled robots are mobile robots that are noteworthy because of their maneuverability and mobility. Unicycle is a mobile robot that requires low space and needs low energy to move. It can be used in various applications especially in an area with limited space. This robot just has a single ground contact and it may be fall in both longitudinal and lateral directions. On the other hand, control of the robot is more difficult because the robot is an underactuated system. Thus balancing a unicycle robot is an important and challenging topic that has been studied for years and it is a noticeable research platform for control engineers. The unicycle robot should remain stabilize under disturbances and inherent nonlinear effects and tracks the desired straight or curved path. In this research the study is performed on an unicycle robot that is consisting of a body, wheel, and two disks that are located at the left and the right of the robot's body. The designed mechanism can stabilize the robot while tracking a direct path without effect on steering angle. Also Steering control of the unicycle can be achieved using this mechanism. First the dynamic model of the robot is derived by Lagrangian approach. Since the unicycle behavior is known and there is an explicit understanding of its dynamic, the derived equations are validated. In this way, by defining predictable conditions of dynamic system behavior and simulation the system by defining conditions, the output of the simulated system was adapted to the dynamic sense of the system. The inputs of the system are defined in such a way that the robot is limited to moving in a straight path and the study was performed on its stability. Three types of controllers were designed to maintain the robot's stability, and all of them produced some sort of desirable result. Stabilizing in longitudinal plane utilize wheel inverted pendulum technique and Stabilizing in lateral plane is based on gyroscopic effect of two disks. Therefore the stability of the system is affected by precession angular velocity of the disks and the rotational speed of the disks at the same time. So angular velocity of the disks has studied in a part of the research. But what increases the maneuverability of a single wheel and allows it to cross a curved path or an obstacle is steering control. Finally, the equations have been rewritten to control steering angle and a fuzzy controller has been designed for its control. The simulation results show that the robot stabilize itself while changing its yaw angle. Keywords: Gyroscopic effects, unicycle robot with two flywheels, three dimensional modeling, fuzzy control,underactuated robot, steering control