Methods and devices for releasing an electric actuator in a reliable manner using a quasi-elastic release end stop

A method for releasing an electric parking brake of a brake system of a motor vehicle, said motor vehicle having an electronic control unit which is configured to control a plurality of electric actuator units, wherein the electronic control unit is embodied with a respective channel for each of the plurality of electric actuator units, and wherein an activation request is generated electrically by an operator control element or automatically and is executed by the plurality of electric actuator units, and wherein a release request is generated electrically by the operator control element or automatically and is executed by the plurality of electric actuator units, the method comprising:

• a) moving, by at least one of the plurality of electronic actuator units, an actuator element in the direction of a release end stop in the release process by energizing the at least one of the plurality of electronic actuator units,
• b) observing, by the electronic control unit, a power demand of the at least one of the plurality of electric actuator units,
• c) wherein the release end stop has a defined elasticity, with the result that
• d) the approach, formation of contact and impacting between the actuator element and the release end stop feeds back a particularly modulated change in the power demand of the at least one of the plurality of electric actuator units, which is observed by the electronic control unit,
• e) calculating with the electronic control unit a switch-off current using a predefined relationship and based on one or more physical parameters,
• f) selecting with the electronic control unit a defined switch-off current limiting value based on the calculated switch-off current, wherein the electronic control unit selects the switch-off current limiting value from a plurality of stored values, and
• g) automatically interrupting, by the electronic control unit, the energization of the at least one of the plurality of electric actuator units after detection of the approach, formation of contact and impacting against the release end stop, wherein the interruption of the energization is performed by the electronic control unit if an observed power demand reaches or exceeds the selected switch-off current limiting value.