Method for synchrophaser measurement and synchrophaser control

Claim 1

Apparatus for controlling the relative spatial positioning of blades on different propellers of a multi-engine aircraft of the type having blade pitch control to vary each propeller's blade pitch angle to regulate actual propeller speed in a manner to reduce a difference speed error between an actual speed signal and a propeller reference speed signal, the apparatus controlling blade positioning by adjusting the blade pitch angle of each designated slave propeller to achieve a desired phase angle offset between each slave propeller and a designated master propeller, comprising: sensor means, one for each engine, for providing a signal pulse in response to rotation of each propeller blade past a reference point, the real time interval between successive said signal pulses from the master propeller being designated T M and the real time interval between each master propeller signal pulse and a next succeeding said signal pulse for a slave propeller being designated T D ; signal processing means, responsive to said signal pulses from each said sensor means, and having memory means for storing a first executable algorithm for calculating individual phase error signals (φ E ) , each representative of the difference angular displacement between a reference phase value (φ REF ) and the actual angular displacement in blade position between the master propeller and each slave propeller, as defined by the equation: ##EQU10## where NP is equal to the number of propeller blades; and signal summing means, for summing each said individual phase error signal with the related propeller reference speed signal to produce a modified difference speed error therefor to adjust each slave propeller's blade pitch angle in a manner to reduce the magnitude of each said phase error; as characterized by the improvement, comprising: counter means, responsive to each said calculated phase error signal for incrementing a standing count value (φ COUNT ) by one unit value for each positive value discontinuity occurring in a calculated phase error signal and for descrementing said standing count value for each negative value discontinuity occurring therein; and wherein said memory means further includes a second executable algorithm for calculating improved accuracy phase error signals as defined by the equation: ##EQU11## said improved accuracy phase error signals being presented to said signal summing means for summation with the related propeller reference speed signal to produce said modified speed reference speed error.