1. An actuator control apparatus comprising: an observation unit configured to estimate a state of a load based on an equation including at least one modeled load parameter; a controller which outputs a signal for controlling the load; a compensation unit configured to compensate for the signal output from the controller comprising: a first compensator configured to increase or decrease an output signal of the controller; a second compensator configured to increase or decrease position compensation information; a third compensator configured to increase or decrease speed compensation information; and an adder which adds an output of the second compensator to an output of the third compensator and adds a result of an addition to an output of the first compensator, thus outputting a final control signal; and an estimator configured to estimate a change of a load parameter, to decide a gain of the compensation unit based on the estimated change of the load parameter, and to update the modeled load parameter based on the estimated change of the load parameter.