Patent ID: 8727696

Claim:
A method for automatically calibrating a variable geometry turbine actuator, the turbine having an annular inlet passageway, the passageway being closable at least partially by adjusting the position of a variable geometry element, the variable geometry element being movable between first and second limit positions, the method comprising the steps of: a) providing an actuator having an output shaft; b) coupling the actuator output shaft to a transmission mechanism for moving the variable geometry element; c) providing a rotary sensor device coupled to the output shaft of the actuator, the rotary sensor device comprising a sensor wheel with a stop, a clutch mechanism and a rotary position sensor, the rotary sensor device being arranged to convert movement of the actuator output shaft into rotation of the sensor wheel, the sensor wheel having a rotational range that is limited by said stop, the rotary position sensor being configured to generate an output signal representative of the rotary position of the sensor wheel; d) operating the actuator output shaft so as to rotate the sensor wheel in a first rotational direction until the variable geometry element reaches the first limit position; e) operating the actuator output shaft so as to rotate the sensor wheel in a second direction until the variable geometry element reaches the second limit position; f) allowing the sensor device to declutch from the actuator in the event the wheel is prevented from rotating by the stop in either direction of rotation, thereby ensuring the range of movement of the variable geometry element in use occurs within the rotational range of the sensor; and g) logging, as a limit value, the value of said output signal generated when the variable geometry element is at one of said first or second limit positions.