Abstarct: In this study, an active vibration absorber is utilized for a nonlinear 1 DOF system with unknown multi harmonic frequency disturbance. At first, we estimate a function of disturbance force consist of itself and first and second derivative of that. Then the position of the main system is controlled by feedback linearization and sliding mode controllers. For applying of controller force, a magnetic actuator is used which is controlled by a sub controller. Liunberger observer estimates force function value and by means of this estimation the feedback linearization and sliding mode controller regulate position of main system. Controller’s coefficients are obtained by particle swarm optimization algorithm (PSO) to minimize settling time and errors. Magnetic actuators are designed by Faraday and Lorentz law for applying the controlling force to system. Simulation results of observer is compared to real value and the results show the proper effective of active vibration absorber on vibration suppression. The optimization of controller coefficient show the improvement of settling time and error.