A method of estimating an operating state of a drive system is presented. The drive system comprises an electric motor and a mechanical unit being moved by the electric motor. The method comprises a) operating the electric motor using electrical properties, b) determining movement properties regarding the movement of the mechanical unit using the electrical properties, repeating steps a) and b) for a number of times using changed electrical properties, and generating a distribution function. The distribution function allocates electrical properties to the resulting movement properties. The method also comprises estimating the operating state in response to the generated distribution function.