Drive controller with self-contained correction function of position errors

An electric drive, comprising

• a converter,
• an electric machine receiving electrical energy via the converter, and
• a drive controller,
• wherein the drive controller is configured to operate in a normal operation or in a special operation,
• wherein the drive controller, in the normal operation, continuously
• receives raw signals from a position transmitter disposed on the electric machine and detecting a rotational position of a rotor shaft of the electric machine,
• determines an actual position of the rotor shaft based on the received raw signals in conjunction with correction variables determined during the special operation, and
• determines for the converter control signals based on a target position and the actual position or based on a target rotational speed and an actual rotational speed of the rotor shaft, with the actual rotational speed being determined from the actual position, and outputs the determined control signals to the converter,
• wherein the drive controller, in the special operation,
• first determines for the converter control signals that cause the rotor shaft to rotate at an initial rotational speed, and outputs the first determined control signals to the converter,
• thereafter operates the electric machine in a non-powered manner causing the rotor shaft to coast down,
• while the rotor shaft coasts down, continuously receives the raw signals from the position transmitter, determines therefrom raw positions of the rotor shaft, and buffers the determined raw positions,
• models the coasting down of the rotor shaft in accordance with a model comprising model parameters,
• determines based on the determined raw positions the correction variables and the model parameters, and
• saves the determined correction variables in a correction variable memory and makes the determined correction variables available in the normal operation for determining the actual position.