A door drive device for adjusting and/or locking a vehicle door relative to a vehicle body including an adjustment member, a drive element operatively coupled to the adjustment member such that the adjustment member is movable with respect to the drive element for moving the vehicle door, a sensor device for measuring a measuring quantity indicative of a movement of the vehicle door to provide a sensor signal, a brake device operatively connected to the drive element for braking a movement of the vehicle door, and a control device for controlling operation of the door drive device. The control device is configured to compute, from the sensor signal obtained from the sensor device, an acceleration value indicative of an acceleration of the vehicle door and evaluate the acceleration value to distinguish movement of the vehicle door caused by a gravity force from movement caused by a user action.