US Patent 7415950 Engine valve control system and method

A method of operating an engine having at least one cylinder, said cylinder including at least one electric valve actuator, said actuator including at least a coil and an armature moveable thereto, the method comprising during a non-firing state of the cylinder: holding the armature of the actuator at a first position away from an equilibrium position by supplying a first amount of current to a first coil of the actuator; and reducing current supplied to the first coil from said first amount to a lower second amount to cause the armature to begin moving toward the equilibrium position; and during a subsequent firing state of the cylinder, varying an amount of holding current supplied to the first coil for holding the armature away from the equilibrium position based on at least said second amount of current.