1. A computer-implemented method to determine an inertia parameter for an observer-based control, the method comprising the steps of: a) determining an initial value for the inertia parameter; b) running the actuator with predetermined position commands using the initial value for the inertia parameter; c) integrating an expected acceleration signal to form an integrated expected acceleration; d) integrating a corrected acceleration signal to form an integrated corrected acceleration; e) calculating an acceleration ratio using the integrated expected acceleration and the integrated corrected acceleration; f) comparing the acceleration ratio to a predetermined value; and g) setting the inertia parameter to the initial value if the acceleration ratio is within a specified tolerance of the predetermined value.