Method for operating an automatic washing machine, and automatic washing machine

A method for operating a washing machine having a suds container for holding washing liquid, a non-ribbed drum rotatably mounted in the suds container for holding laundry, a motor for driving the drum, and a control device, comprising the following steps while rotating the drum in a subcritical rotational speed range:

• determining an average value, a minimum, and a maximum of an oscillation of a physical variable relating to the drum or the motor per complete revolution of the drum over a predetermined period of time in which a plurality of revolutions of the drum take place;
• forming an overall average value from the determined average values;
• subtracting the overall average value formed from the corresponding minimum determined per oscillation and the corresponding maximum determined per oscillation to calculate a maximum value and a minimum value per oscillation, respectively;
• forming in each case an amount from the respective calculated maximum value and in each case an amount from the respective calculated minimum value;
• determining a standard deviation from the amounts formed over the predetermined period of time;
• and
• detecting, based on the determined standard deviation, whether a loading situation where laundry is rolling in the drum is present.