A method for monitoring a condition of an actuator for a machine using a closed loop Hammerstein model structure is disclosed. The method includes receiving measured data for the machine and determining an actuator command associated with the measured data. The method also includes identifying a current static nonlinearity using one or more linear regression techniques, where the static nonlinearity is modeled between a known actuator and a linear plant of the machine. The method further includes determining whether the condition of the actuator has changed by comparing a resultant from identifying the current static nonlinearity with information of the known actuator.