1. A method for field-oriented operation to zero speed of an encoder-less asynchronous machine, comprising the steps of: calculating an actuating voltage and an adapted rotation speed, calculating a model flux and a model current from the calculated actuating voltage and adapted rotation speed, calculating a complex difference for a rotation-speed adaptation as a function of the calculated variables model flux and model current and of a measured machine current, wherein the calculated model current and the measured machine current are weighted and subtracted from one another, with the weighted current difference being projected onto the calculated model flux, calculating from the calculated variables model flux and model current a model slip rotation speed, superimposing the adapted rotation speed and the calculated model slip rotation speed to form a sum signal representing the rotation speed actual value, and controlling the asynchronous machine with the sum signal.