In the past century overhead cranes have gained a very important role in industries and ports. One of the most important parts that need to be repaired is the wheels of the bridge. The bevel of the bridge is due to the fast wearing of wheels and rails. So it is vital to eliminate yaw motion of the bridge. In this thesis the factors causing yaw motion of bridge has been studied and the dynamic behavior of trolley and bridge has been presented by differential equations. The previous methods of controlling the bridge of overhead cranes have been simulated by Matlab- Simulink. It is easily seen in a bad condition, these methods are not able to eliminate the bevel motion of bridge properly. Finally a new controller has been presented .In this method, four limit switches are applied to measure the distance between the rail and wheel axes. Different outputs of limit switches represent different states. The controller produced proper signals to control the bridge in each case. Complete simulation result of a 5-ton overhead crane bridge with two induction motors and
