Many researchers have contribu properties of object using various method suc and color. However, stiffness of object and r same as the object property which is acquirable The bilateral control is a new method to environment as the robot contact with unknow feedback from disturbance observer is applied paper proposes a methodology to classify the o analysis. Master-Slave robot based on bilateral knock the objects. Then the motion copying save data of knocking force and replay aga knocking forces equal. Finally the force re estimated by disturbance observer (DOB) is a Fast Fourier transform.