Dog clutch engagement method of electric four-wheel drive vehicle

A method of engaging a dog clutch of an electric four-wheel drive vehicle, the dog clutch comprising an input gear connected to a drive unit, an output gear connected to a drive wheel, and a sleeve engaging or disengaging the input gear and the output gear while being fitted to the output gear, the method comprising:

• when dog clutch engagement is requested during driving, determining a target synchronization speed of the input gear to be a sum of an estimated speed and an offset speed of the output gear;
• operating the drive unit so that the input gear follows the target synchronization speed;
• when an actual speed of the input gear reaches the target synchronization speed, moving the sleeve to a meeting position at which the sleeve is in contact with the input gear;
• when the actual speed of the input gear is synchronized with an actual speed of the output gear, transporting the sleeve to an engagement position at which the input gear and the output gear are coupled;
• and
• when the dog clutch engagement is requested during deceleration driving, the offset speed is determined to be a negative value.