Communications: electrical – Aircraft alarm or indicating systems – Nonairplane
Reexamination Certificate
1999-04-16
2001-09-25
Swarthout, Brent A. (Department: 2632)
Communications: electrical
Aircraft alarm or indicating systems
Nonairplane
C073S17800T, C244S017110
Reexamination Certificate
active
06295006
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an actuator for an aircraft and, more particularly, to an actively controlled actuator for controlling the flap angle in a helicopter rotor blade.
BACKGROUND OF THE INVENTION
Helicopter main rotor lift and rotor driving torque produce reaction forces and moments on the helicopter main gearbox. In addition to the primary flight loads, the aircraft is also subjected to vibratory loads originating from the main rotor system. These vibratory loads produce vibrations and noise within the aircraft that are extremely annoying and fatiguing to the passengers.
One vibratory load that is of particular concern results from the interaction of the rotor blades with blade vortices developed by the preceding blades during rotation. As the rotor blade rotates, the air flows passing over and under the blade combine downstream from the trailing edge creating a vortex. During normal flight modes, the blade vortices do not cause any particular problem. However, in certain instances, for example during rotor deceleration such as when the aircraft is descending, the trailing blade contacts the blade vortex generating an impulsive noise or slap. This contact with the vortex also creates a vibration within the rotor system that transfers into the cabin. These vibrations can be upwards of 5/rev (i.e., 5 times per revolution of the rotor system). The noise and vibrations generated by the blade interaction with the vortices is annoying to the passengers and crew within the helicopter and produces an external noise signature which can be easily detected at long range, increasing the aircraft's vulnerability when in a hostile environment.
Many attempts have been made over the years to alleviate or reduce blade vortex interactions. A considerable amount of those attempts have been directed toward passive type systems wherein the blade is designed to weaken the vortex at the blade tip. See, for example, U.S. Pat. No. 4,324,530 which discloses a rotor blade with an anhedral swept tapered tip which reduces the intensity and shifts the location of the tip trailing edge vortex so as to reduce the occurrence of blade vortex interactions.
While passive solutions have provided some reduction in blade vortex interaction, those solutions also tend to negatively impact the flight characteristics of the rotor blade.
Active rotor control systems have recently been proposed to counteract blade vortex interactions. These systems are typically designed to change the motion of the rotor blade to miss the blade vortex or cut the vortex differently so as to reduce contact with the blade vortex. One of these systems is called higher harmonic blade pitch control wherein the blade pitch is controlled to reduce the vortex at the blade tip. While the reduced blade tip vortex does lead to lower noise from blade vortex interaction, the change in blade pitch also reduces the aerodynamic characteristics for the entire blade.
Another active control system is discussed in U.S. Pat. No. 5,588,800. This active control system is mounted within a helicopter rotor blade and includes actuatable flaps on the rotor that are controlled to reduce the blade vortex interaction. An actuator is used to control the movement of the flaps and can be either mechanical, electrical, pneumatic, or hydraulic. U.S. Pat. No. 5,639,215 discloses a similar actuatable flap assembly. In this assembly, the actuator is a mechanical actuator that is either a push-rod type device, a linkage, or a servo-motor driven rack.
Although the prior art systems for actively controlling the rotor blade interactions with the blade vortex are empirically better than the passive systems described above, these prior art systems do not address the realistic problems associated with mounting an actuation system within a rotor blade to control the flaps in the desired manner.
A need, therefore, exists for an improved actuation system for use in an active rotor control system to control flaps on a rotor blade.
SUMMARY OF THE INVENTION
The present invention is directed to a flap angle measurement system for a helicopter rotor blade. The blade includes a trailing edge and a flap hinged to at least a portion of the trailing edge about a pivot axis. The flap angle measurement system includes a Hall effect sensor mounted to the trailing edge of the rotor blade. The Hall effect sensor has a sensing face. A magnet is mounted to the flap at a location spaced apart from the pivot axis. The magnet has a pole axis that is located parallel to the sensing face of the Hall effect sensor. A power source supplies power to the Hall effect sensor.
A controller receives output signals from the Hall effect sensor which are indicative of the location of the magnet with respect to the sensing face of the Hall effect sensor. The position of the flap relative to the trailing edge is determined based on the received signals from the Hall effect sensor.
In one embodiment of the invention, there is a second Hall effect sensor mounted on the other end of the flap. The sensing face of the second Hall effect sensor points in a direction opposite from the sensing face of the first Hall effect sensor.
The foregoing and other features and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments thereof, as illustrated in the accompanying figures. As will be realized, the invention is capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive.
REFERENCES:
patent: 4107604 (1978-08-01), Bernier
patent: 4163208 (1979-07-01), Merz
patent: 4319236 (1982-03-01), Brace et al.
patent: 5033694 (1991-07-01), Sato
patent: 5239468 (1993-08-01), Sewersky et al.
patent: 5639215 (1997-06-01), Yamakawa et al.
patent: 6200096 (2001-03-01), Kohlhepp
Paper entitled Wind Tunnel Test of an Active Flap Rotor:BVI Noise and Vibration Reduction, Seth Dawson et al., dated May 9-11, 1995, pp. 631-648.
Paper entitled “Higher Harmonic Actuation of Trailing-Edge Flaps for Rotor BVI Noise Control”, Bruce Charles et al., dated Jun. 4-6, 1996, pp. 59-79.
Paper entitled “Flight Demonstration of Higher Harmonic Control (HHC) On S-76”, W. Miao et al., dated Jun. 2-4, 1986, pp. 777-791.
Abstract entitled “Individual Blade Control Project”, pp. 1-2, http://halfdome.arc.nasa.gov/~aarweb/research/ibc.html, dated Jul. 2, 1997.
Abstract entitled “Aeroelastic and Dynamic Rotor Response with On-Blade Elevon Control”, one page, http://halfdome.arc.nasa.gov/publications/abstracts/abs14.html, dated approximately Sep., 1998.
Abstract entitled “Hover Testing of a Small-Scale Rotor with On-Blade Elevons”, one page, http://halfdome.arc.nasa.gov/publications/abstracts/abs12.html, dated approximately Apr., 1997.
Drinker Biddle & Reath LLP
Sikorsky Aircraft Corporation
Swarthout Brent A.
LandOfFree
Flap angle measurement system for an active rotor control... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flap angle measurement system for an active rotor control..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flap angle measurement system for an active rotor control... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436194