Boots – shoes – and leggings
Patent
1992-05-27
1994-08-02
Black, Thomas G.
Boots, shoes, and leggings
36443101, 36443108, 416 27, 416 33, 416 44, 416 34, B64C 1150
Patent
active
053351754
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a propeller control system, and, in particular, a propeller control system for use in circumstances of high free air turbulence.
It should be noted that air turbulence buffeting the propellers of an aircraft cause fluctuations in the rotational speed of the propellers. In the case where localised turbulence is experienced the rotational speed of the propellers may vary. Therefore, in the case where the aircraft has two or more propellers which are synchrophased localised turbulence can cause the synchrophasing to be out of alignment.
In an attempt to counteract the effects of this on the performance of the aircraft, the speed and phase control system of an aircraft are set up so that they can tolerate the effects of the turbulence. In particular the gain or sensitivity of the speed or phase control system is set at a lower level than would otherwise be desirable in order to accommodate turbulent conditions.
SUMMARY OF THE INVENTION
According to the invention there is provided a propeller control system for use with an aircraft having two or more propellers comprising a propeller controller having a control gain to control a propeller relationship, a free air turbulence detection means and a gain controller for varying the control gain in response to detected free air turbulence such that in the presence of turbulence a low gain is selected and in the absence of turbulence a high gain is selected.
Thus a compromise value for the control gains need not be chosen for the gains are set according to the prevailing degree of turbulence and can be varied as the conditions change so that the control gains are always at the optimum values.
The relationship controlled may be a phase or speed relationship.
The propeller controller may act to vary the speed and/or phase of the propeller.
The means for detecting the presence of free air turbulence may detect turbulence by monitoring the electronic propeller controllers ability to hold the propellers phase and/or speed. This can be achieved by a simple check of the achieved speed and/or phase against the desired speed and/or phase, or a Performance Index. (For a description of a Performance Index refer to Richard C. Dorf "Modern Control Systems" Addison, Wesley Third Edition).
In performing the check mentioned above the Integral of Absolute Error (IAE), the Integral of Time multiplied by Absolute Error (ITAE) or similar standard measures of the Performance Index may be utilized to perform a comparison against predetermined turbulence thresholds. Turbulent conditions are present when the Performance Index crosses a threshold value.
Alternatively, turbulence may be detected using accelerometers or other detectors.
A propeller control system made in accordance with the present invention can be used with propeller systems in which the synchrophasing is achieved using a master/slave arrangement or a Master Clock arrangement or any other arrangement.
In the case where a master/slave arrangement is used for the synchrophasing, preferably turbulence detection operates on the signal from the master propeller controller.
It has been demonstrated that a controller in a master/slave configuration will produce only a slow phase drift with the phase control inhibited during turbulent conditions. This is preferable to the excessive phase changes produced by a controller attempting to follow a turbulent master propeller.
BRIEF DESCRIPTION OF THE DRAWINGS
A specific embodiment of the invention will now be described, by way of example only, with reference to the drawing in which:
FIG. 1 shows, schematically, a propeller control system in accordance with the invention; and
FIG. 2 is a rear view of a propeller controlled by the system shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIGS. 1 and 2, a propeller control system, for controlling a pair of propellers in a master slave arrangement where the slave propeller is to maintain a phase relationship with the master propeller, comprises a s
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patent: 5093791 (1992-03-01), Schneider et al.
patent: 5150855 (1992-09-01), Kaptein
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Black Thomas G.
Day Julie D.
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