One of the most important goals in the industry is the elimination of the edge of the sheet and the central surface of the sheet in the steel plate production process. The hot rolled sheet has roughness due to its current state of affairs, and it is unlikely that such a product will be used in various industries, such as automotive or military equipment. To solve this problem and improve the quality of the page, they use flattening systems. The overall structure of these systems is such that, by controlling the hydraulic cylinders, the proper air gap between the rollers is created and the leveling is carried out through the sheet passing through them. Various models have been introduced for this system. Here, the examined model consists of four single cylinder hydraulic cylinders, the piston-powered force is hydraulically pressurized and backward by a spring-loaded force. The rollers are attached to the cylinders by a rigid body, and this creates a reciprocal force between them during the movement. It is proved that the accuracy of the leveling system response, in addition to the force mentioned, is strongly dependent on the damper friction. Therefore, in this research, linear and nonlinear analysis of friction has been fully considered. On the other hand, depending on the position of the cylinders in relation to the pump, the control volume varies for each of them. This volume includes the length of the oil path from the pump to the cylinder chamber, the volume of the pipes and the volume of the valve, and should be considered unknown or variable so that the controller can be applied to each of the hydraulic cylinders. Environment and temperature conditions also affect the oil yield and cause uncertainties in the system. In this thesis, first, the nonlinear model of the system was obtained by considering the existing uncertainties and the effect of friction as well as the mutual force between the cylinders, and then, using a nonlinear non-linear adaptive controller, the effect of the indeterminate parameters was compensated. To achieve this, the step-by-step approach has been used. Keywords : Nonlinear Adaptive Robust Control, Electro-Hydraulic Cylinder, Unknown Nonlinear Parameters.