Washing machine sensing turbidity and controlling method thereof

A washing machine including a washing tub, the washing machine comprising:

• a driving unit configured to rotate the washing tub;
• a turbidity sensor configured to sense a turbidity of water inside the washing tub;
• and
• one or more processors configured to:
• identify a weight of laundry contained in the washing tub when a user instruction for operating the washing machine is received;
• identify a saving mode as an operation mode, based on a number of minor contaminations identified being equal to or greater than a predetermined number based on a contamination level identification history;
• identify a normal mode as the operation mode based on the number of minor contaminations identified being smaller than the predetermined number;
• initiate a washing process based on the weight of the laundry in the identified operation mode;
• identify a level of contamination inside the washing tub based on the turbidity of water sensed by the turbidity sensor when a predetermined time elapses after the washing process is initiated;
• identify whether to terminate the washing process based on the identified level of contamination;
• and
• update the contamination level identification history based on the identified level of contamination,
• wherein the one or more processors are further configured to:
• identify whether at least one level of contamination identified within a predetermined period among a plurality of levels of contamination included in the contamination level identification history corresponds to minor contamination based on the number of minor contaminations identified being equal to or greater than the predetermined number;
• identify the saving mode as the operation mode based on the at least one level of contamination corresponding to the minor contamination;
• and
• identify the normal mode as the operation mode based on the at least one level of contamination not corresponding to the minor contamination.