A combine harvester has a threshing unit for threshing picked-up crop to obtain grain, a driver assistance system for controlling the threshing unit which has a memory for storing data and a computing unit for processing the data stored in the memory. A functional system model for at least a portion of the combine harvester is stored in the memory. The computing unit is designed to carry out an autonomous determination of at least one threshing-unit parameter on a basis of the system model and, for depicting functional interrelationships, at least one family of characteristics (A-J) is assigned to at least one harvesting-process parameter. The at least one harvesting-process parameter is defined as an output variable of the at least one family of characteristics (A-J).