JP2837399B2 - Airspeed measurement system for rotary wing aircraft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airspeed measurement system for a rotary wing aircraft, and more particularly to an airspeed measurement system for a rotary wing aircraft when the rotary wing aircraft is flying at a low speed of, for example, 40 kt or less. The present invention relates to an airspeed measurement system for a rotary wing aircraft that measures speed.

[0002]

2. Description of the Related Art Many noises at the time of approach and landing of a helicopter are caused by rotation of a main rotor.
(Blade vortex interference) Noise is generated when a trailing blade crosses an air vortex caused by a leading blade, and a simple linear landing path generates significant BVI noise.

FIG. 3 is a graph showing a region in which a BVI noise is generated in relation to an airspeed and a descent speed of a helicopter. According to the graph, BVI noise occurs at an airspeed of 40 to 120 kt (knots) and a descent speed of 300 to 1200 ft (ft) / min, and the lowest BVI noise occurs when the descent angle is around 4 to 6 degrees. Turns out to be intense.

[0004] Therefore, in order to suppress the generation of BVI noise as much as possible, the descent angle should be kept small, for example, 3 degrees or less at the start of landing, and the descent angle should be made large, for example, 6 degrees or more just before landing. It is desirable to take a convex, curved flight path.

[0005] Such a flight is possible by manual piloting of a pilot, but in order to reduce the workload, a system that automatically transitions to hovering by automatic piloting is desirable.

For such a flight, it is necessary to accurately measure the airspeed of the helicopter in real time.
To measure airspeed, a speedometer manufactured by Paesa using a pitot tube or a rotating Venturi tube is used.The latter is expensive, tens of millions of yen, and is used for small private helicopters. It is difficult to do so, and usually the former is used. The pitot tube is disposed at the forehead of the helicopter, and measures the airspeed of the helicopter from the difference between the dynamic pressure of air from the front and the pressure of stationary air during forward flight.

[0007]

The measurement of the airspeed by the pitot tube is performed with relatively high accuracy when flying at an airspeed of about 40 kt or more, but is performed at an airspeed of about 40 kt or less. In this case, the air flowing down from the rotor blade of the helicopter disturbs the air entering the pitot tube, and the measurement accuracy cannot be maintained. This makes it impossible to accurately grasp the airspeed of the helicopter, making it impossible to select a flight path that avoids the generation of BVI noise, and to automatically transition to hovering by automatic control.

It is an object of the present invention to provide an airspeed measurement system for a rotary wing aircraft capable of easily and accurately measuring an airspeed even during low-speed flight.

[0009]

SUMMARY OF THE INVENTION The present invention measures a ground speed vector of a rotary wing aircraft and outputs a measured value Vg, a ground speed meter of the rotary wing aircraft, and measures an air speed vector of the rotary wing aircraft to obtain a measured value Va. An airspeed meter that outputs the following formulas: a wind speed vector VW when the magnitude of the measured value Va becomes equal to or less than the predetermined value VT = measured value Vg−storage means for storing the measured value Va; Processing means for setting the measured value Vg-wind speed vector VW to the airspeed vector Vp when the value is equal to or less than the predetermined value VT, and setting the measured value Va to the airspeed vector Vp when the magnitude of the measured value Va is larger than the predetermined value VT; This is an airspeed measurement system for a rotary wing aircraft, comprising: According to the present invention, even if the accuracy of the airspeed indicator deteriorates due to the effect of air flowing downward from the rotor during low-speed flight, the measurement value Vg measured by the ground speedometer which is not similarly affected, and the low-speed flight Since the airspeed vector Vp defined by using the wind speed vector VW measured until the transition to is used, the accuracy of the measurement of the airspeed vector during low-speed flight can be improved. Further, by using the airspeed vector Vp accurately measured in the entire speed range as described above, it is possible to perform a flight control that automatically transitions to hovering while performing a flight control to avoid the generation of BVI noise, for example. Becomes

[0010] In the present invention, the ground speed meter may be a GPS.
Alternatively, it is characterized by being constituted by DGPS. According to the present invention, since the GPS (Global Positioning System) is used, even if the rotary wing aircraft flies over the earth, it receives radio waves from a plurality of satellites orbiting the earth. , The ground speed vector of the own device can be output as the measured value Vg. Thereby, the airspeed vector Vp can also be obtained, and the versatility of the airspeed measurement system for a rotary wing aircraft can be expanded. Also, DGP
When S (Differential GPS) is used, a higher-accuracy measurement value Vg is output by taking a difference with respect to a base station that is stationary at a predetermined position on the ground, so that the accuracy of the airspeed vector Vp can be improved. It can be further improved.

Further, the present invention is characterized in that the airspeed meter is constituted by an inexpensive pitot tube. According to the present invention, in the velocity region where the air entering the pitot tube is not disturbed by the air from the rotor blade, the measured value Va by the pitot tube is used.
Is replaced by the airspeed vector Vp, and the wind speed vector VW can be obtained by subtracting Va from the ground speed vector Vg.

[0012]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of the present invention. The antenna 1 and the pitot tube 3 are arranged on a surface of a helicopter body (not shown). The GPS receiver 2 receives radio waves from a plurality of artificial satellites rotating around the earth from the antenna 1, measures a ground speed vector of the helicopter, and outputs a measured value Vg as a vector value. The GPS may be a DGPS, in which case it also receives radio waves from a base station stationary at a predetermined location on the earth. The pitot tube 3 measures the total pressure of the fluid flowing into the total pressure tube and the static pressure of the stationary fluid, and measures the difference between them to measure the flow velocity of the fluid. The flow velocity can be measured in one to three dimensions depending on the number and arrangement. Here, it is assumed that an airspeed vector is measured and a measured value Va that is a vector value is output. The processing unit 4 performs different processing depending on the magnitude of the measurement value Va of the pitot tube 3.

First, when the helicopter flies at an airspeed satisfying | measured value Va |> predetermined value VT, the processing unit 4 uses the measured value Va as it is as an airspeed vector Vp,
And sent to the flight control computer 7. The predetermined value VT is
For example, it is about 40 kt. The processing unit 4 always calculates the measurement value Vg−the measurement value Va as the wind speed vector VW. At the moment when the magnitude of the measured value Va of the pitot tube 3 decreases and becomes equal to or less than the predetermined value VT, the processing unit 4 stores the measured value Vg-measured value Va at that moment in the memory 6 as a wind speed vector VW. . | Measured value Va | ≦ predetermined value VT,
Measured value Vg-wind speed vector VW is converted to airspeed vector Vp
To the instrument 5 and the flight control computer 7. When the magnitude of the measured value Va again falls below the predetermined value VT after exceeding the predetermined value VT, the wind speed vector at that moment is stored again as a new wind speed vector VW.

The instrument 5 displays the airspeed vector Vp to notify the helicopter pilot. The flight control computer 7 controls each part of the helicopter based on the airspeed vector Vp to select an optimal flight path and fly. In particular, when performing bovering or landing, the airspeed vector Vp
Based on the above, automatic transition to hovering by automatic control is performed while performing control such as flight avoiding generation of BVI noise.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention. At the time of start, it is assumed that the helicopter is flying at an airspeed satisfying | measured value Va |> predetermined value VT. First, in step s1,
Substitute 0 for the wind speed vector VW. In step s2, the output from the pitot tube 3 is set as a measured value Va. In step s3, the output from the GPS receiver 2 is measured
g. In step s4, it is determined whether or not the magnitude of the measurement value Va is equal to or smaller than a predetermined value VT. If | Measured value Va |> predetermined value VT, in step s6, the wind speed vector VW is newly measured value Vg−measured value Va
After that, in step s7, the airspeed vector V
The process proceeds to step s8, where p = measured value Va. Measured value V
At the moment when a becomes equal to or less than the predetermined value VT, the wind speed vector VW calculated in step s6 is stored in the memory. If | measured value Va | ≦ predetermined value VT, in step s5, the airspeed vector Vp = measured value Vg−wind speed vector VW (memory value), and the process proceeds to step s8.

In step s8, the flight control computer 7
Controls each part of the helicopter based on the airspeed vector Vp and flies. In step s9, it is determined whether the helicopter has landed or hovered based on the measured value Vg of the GPS and changes in the altimeter disposed on the aircraft. If the helicopter is landing or hovering, the flowchart ends. If neither landing nor hovering has been performed, the procedure returns to step s2 and repeats the processing of steps s2 to s9.

As shown in FIG. 2, while the magnitude of the measured value Va is larger than the predetermined value VT, steps s2 and s
, S6, s7, s8, s9, s2,... Are sequentially repeated, and flight control is performed using the measured value Va output from the pitot tube 3 as the airspeed vector Vp as it is, and each time the wind speed vector VW Is replaced with the measured value Vg-the measured value Va. When the magnitude of the measurement value Va shifts to the predetermined value VT or less, the measurement value Vg-measurement value Va at that moment is expressed by:
Finally, it remains as the wind speed vector VW. Thereafter, as long as | measured value Va | ≦ predetermined value VT, the wind speed vector VW
Holds a constant value. | Measured value Va | ≦ predetermined value VT, and then steps s2, s3, s4, s5, s
8, s9, s2... Are sequentially repeated, and each time, the airspeed vector Vp is rewritten to the measured value Vg-wind speed vector VW.

In the above-described embodiment, the pitot tube 3 is used as an airspeed meter. However, another device may be used as long as it measures an airspeed vector from the pressure of air near the surface of the helicopter body. Similarly, GPS as a ground speed meter
The present invention is not limited to this, and any device that can measure the ground speed vector regardless of the pressure fluctuation of the air around the helicopter, such as a Doppler velocimeter, may be used.

Further, in the above embodiment, the wind speed vector VW is fixed at a constant value until the helicopter reaches the landing or hovering state after the magnitude of the measured value Va falls below the predetermined value VT. This is because generally, it takes about several seconds to ten seconds until the helicopter decelerates from the airspeed of 40 kt to landing or hovering, and the wind direction and the wind speed during that time may be considered to be constant.

[0020]

As described above, according to the present invention, the airspeed vector Vp can be easily and accurately measured even during low-speed flight. Further, by using the airspeed vector Vp accurately measured in the entire speed range in this way, for example, it is possible to avoid the occurrence of BVI noise and to perform flight control in which transition to hovering is automatically performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the embodiment of the present invention.

FIG. 3 is a graph showing a region where BVI noise is generated with respect to an airspeed and a descent speed of a helicopter.

[Explanation of symbols]

 2 GPS receiver 3 Pitot tube 4 Processing unit 6 Memory

Claims (3)

(57) [Claims] 1. measuring a ground speed vector of a rotary wing aircraft,
A ground speed meter that outputs a measured value Vg, an air speed meter that measures an air speed vector of a rotary wing aircraft and outputs a measured value Va, and a magnitude of the measured value Va is a predetermined value VT
A storage means for storing the wind speed vector VW = measured value Vg-measured value Va when the measured value is equal to or less than the measured value V when the magnitude of the measured value Va is equal to or less than the predetermined value VT
g-wind speed vector VW as airspeed vector Vp, and when the magnitude of measured value Va is greater than predetermined value VT, processing means for measuring value Va as airspeed vector Vp. Airspeed measurement system for aircraft. 2. The ground speed meter is a GPS or DGP.
The airspeed measurement system for a rotary wing aircraft according to claim 1, wherein the airspeed measurement system is constituted by S. 3. The airspeed measurement system for a rotary wing aircraft according to claim 1, wherein the airspeed meter is constituted by a pitot tube.