Patent ID: 7938382
Filing Date: 2011-05-10
Classification: F16K,H02P

Abstract:
1. A stepper motor in combination with a controller and a valve, which provide for controllably adjusting the valve to vary fluid flow therethrough, the combination comprising: a valve that is configured to be rotatably displaced to thereby adjustably vary the fluid flow rate through the valve; a shaft rotatably coupled to the valve; a stepper motor having a rotor coupled to the shaft, and a stator, the stator having a plurality of stator coils that are configured to effect rotation of the rotor upon application of a voltage to the plurality of stator coils, for rotatably stepping the rotor to a desired angular displacement; one or more sensing coils disposed in the stator such that rotation of the rotor generates an induced voltage in each of the one or more sensing coils, wherein each of the one or more sensing coils are configured to output an induced voltage signal; a controller that receives the induced voltage signal from the one or more sensing coils and determines a vector value based on the induced voltage signal from the one or more sensing coils, the controller being configured to output a constant vector value that does not change in value while the rotor rotates in a continuous manner, and to output a diverging vector value when the rotor is inhibited from rotating in a continuous manner, the controller being configured to determine the angular displacement of the rotor based on the constant vector value and the induced voltage signal from the one or more second sensing coils, the controller being further configured to detect the occurrence of a diverging vector value indicative of the rotor being inhibited from rotating in a continuous manner, and to resume tracking the rotor step position upon restoration of continuous rotation of the rotor, to thereby track the rotor's actual angular displacement position with precision.