Wheel load estimation method for four-wheel drive vehicle

A control unit of a four-wheel drive vehicle, comprising:

• a non-volatile memory that stores a correlation relationship, wherein the correlation relationship has been selected from a plurality of correlation relationships for a plurality of vehicle types, the plurality of correlation relationships having been obtained through experiments conducted in advance, and each indicating a change in a total vehicle weight as a number and a position of occupants and cargo changes, and a corresponding change in at least one of a front wheel load and a rear wheel load for each type of vehicle;
• one or more inputs configured to acquire a driving torque transmitted by a prime mover to driving wheels and a vehicle longitudinal acceleration generated by the driving torque, from one or more sensors;
• and
• a processor configured to estimate the wheel loads of the front wheels, rear wheels or both for the current vehicle by calculating a current total vehicle weight from the driving torque and the vehicle longitudinal acceleration and applying the current total vehicle weight to a formula for the correlation relationship, wherein the processor is further configured to perform driving force distribution control using the estimated wheel loads for the current vehicle,
• wherein vehicle type is determined by the correlation relationship between a total vehicle weight and at least one of the front wheel load and the rear wheel load.