Fluid reaction surfaces (i.e. – impellers) – With control means responsive to non-cyclic condition... – Plural distinct impellers having related control
Patent
1992-05-27
1994-11-08
Look, Edward K.
Fluid reaction surfaces (i.e., impellers)
With control means responsive to non-cyclic condition...
Plural distinct impellers having related control
416 40, 36457107, B64C 1150
Patent
active
053622057
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method and apparatus for synchronizing the speed and phase of plural propellers of an aircraft.
BACKGROUND OF THE INVENTION
With existing forms of propeller control systems a compromise of the gains for speed, phase and beta control is made. Specifically, the gains are selected to produce a satisfactory stability margin for all operating conditions and in particular all airspeeds. This in fact results in lower gains being utilized than the gains which would produce optimum control.
Propeller synchrophasing systems serve to control the phase difference in the rotary motion of two propellers so as to maintain it at a desired phase difference. A phase sensor senses the phase difference between the two propellers and this is compared with a desired phase difference to produce a phase error signal. This error signal is then used to vary the relative speed of rotation of the propellers so as to adjust the phase difference between them until it matches the desired phase difference, at which point the error signal is zero. The rate of adjustment of the phase difference is determined by the gain of the system.
U.S. Pat. No. 5,093,791 discloses a propeller synchrophasing system of this known type in which the gain of the system is varied in accordance with the phase difference between the propellers so that there is a lower gain within a limited range of phase difference either side of zero error signal, and there is a higher gain outside of this range. The system is therefore more responsive to higher values of phase difference.
SUMMARY OF THE INVENTION
In accordance with the present invention a propeller control system suitable for use with an aircraft having at least two propellers includes a propeller controller having a control gain and means for varying the control gain in response to forward airspeed data.
By varying the propeller controller gain the overall system gain can be maintained at the ideal level as the airspeed changes. The airspeed data may be provided by a sensor remote from or associated with the system.
In effect, a propeller control system made in accordance with the present invention uses a technique called gain scheduling which is applied as a function of forward air speed to operate the necessary functions of the propeller control systems.
The propeller control system may be used to control phase, speed or act as a beta controller or any combination of these.
The gain controlled may be proportional, integral or differential gain or these gains in combination.
Preferably, the propeller control system includes an electronic propeller controller.
Alternatively, the electronic propeller controller may be built into the Full Authority Digital Electronic Controller FADEC or other controller.
In a preferred embodiment of the present invention the scheduling is achieved by mathematical algorithms built into the software of the electronic propeller controller.
Alternatively, the scheduling is achieved by providing set predetermined stored data between which interpolation is used.
Preferably, as a safety precaution in the event of a loss of the forward air speed data the electronic propeller controller defaults to a single set of gains/values selected as with conventional fixed term controllers.
BRIEF DESCRIPTION OF THE DRAWINGS
A specific embodiment of the invention will now be described, by way of example only, with reference to the drawings in which:
FIG. 1 shows in schematic form a propeller phase control system in accordance with the
FIG. 2 shows the relationship of power coefficient and advance ratio for a propeller controlled by the control system shown in FIG. 1 at various blade pitch angles.
DETAILED DESCRIPTION OF THE INVENTION
An aircraft propeller synchrophasing system 1 shown in FIG. 1 comprises monitor means 10 which monitors the phase difference between two propeller rotation signals P1 and P2 and produces a corresponding output signal S1, a phase controller 6 including a variable gain function to which the signal S1 is su
REFERENCES:
patent: 4569021 (1986-02-01), Larson et al.
Lee Michael S.
Look Edward K.
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