Generally. most of the physical systems affected by disturbance or incomplete knowledge are complex and highly nonlinear. To control under these circumstances. many researches are ongoing in modern control theory recently. But the researches need apparatuses. which can verify the controller for being not damaged the real plant. In this paper. therefore. a seesaw system is considered control system to analyze and apply the control theory. A seesaw system consists of a moving cart on the rail and seesaw frame made to demonstrate the effectiveness of the control theory. The system has balancing and positioning problems. and the driving force is applied on the DC motor of cart. but not on the pivot. The purpose of control is to maintain an equilibrium of seesaw frame in spite of an allowable disturbance. Computer simulations are given to illustrate the control performance of the proposed scheme.