Laundry treating apparatus and method for controlling the apparatus

A method for controlling a laundry treating apparatus, wherein the apparatus comprises a main drum and an auxiliary drum selectively mounted on the main drum, the method comprising one of:

• washing laundry in the main drum during a general washing mode in which laundry in the main drum is washed while the auxiliary drum is separated from the main drum;
• washing laundry in only the auxiliary drum during an auxiliary washing mode in which only laundry in the auxiliary drum is washed while the auxiliary drum is mounted on the main drum;
• or
• washing laundry simultaneously in the auxiliary drum and the main drum during a simultaneous washing mode in which laundry in the auxiliary drum and laundry in the main drum are washed while the auxiliary drum is mounted on the main drum;
• and
• performing one of the auxiliary washing mode or the simultaneous washing mode, including rotating the main drum to generate a centrifugal force for discharging water in the auxiliary drum out of the auxiliary drum during a provisional spinning operation;
• after the provisional spinning operation, performing a main laundry quantity detection operation for detecting a laundry quantity in the main drum by rotating a pulsator included in the main drum;
• and
• after the main laundry quantity detection operation, detecting a quantity of laundry in the auxiliary drum by rotating the main drum during an auxiliary laundry quantity detection operation;
• wherein the auxiliary laundry quantity detection operation is performed based on a main laundry quantity detected in the main laundry quantity detection operation.