FIELD : medicine.SUBSTANCE : invention relates to medicine and can be used for surgical stapling. Surgical instrument comprises an end effector, an articulation assembly, a shaft and a housing extending proximally from the shaft. Articulation assembly is configured to articulate the end effector relative to the shaft, a firing assembly is configured to fire a plurality of staples, and a locking member is movable between a locked configuration and an unlocked configuration. Housing is removably couplable to the shaft when the locking member is in the unlocked configuration. Motor in the housing is configured to drive at least one of the firing assembly and the articulation assembly. Controller is in communication with the motor and is configured to activate the motor to reset at least one of the firing assembly and the articulation assembly to a home state when the locking member is moved between the locked configuration and the unlocked configuration.EFFECT : drive train control arrangements for modular surgical instruments are disclosed.8 cl, 199 dwg