JPH0345765B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting deformation of a part of a rotating object, and was developed particularly for application to detecting the degree of unbalance of a rotor of a helicopter. The method of the present invention can also be applied to other rotating bodies.

Another feature of the invention is that when the method is applied to the detection of helicopter rotor blades, it is convenient to display the results calculated from the test results in a very easily understood way. Concerning how to display.

According to the invention, in a method for detecting the deformation of parts of rotating objects, a transmitted radiation beam is directed to said parts sequentially as they rotate, and the radiation received after reflection from these determines the distance thereof. used to.

A helicopter rotor should be balanced with respect to its center of rotation with respect to its mass and with respect to the equality of lift from each wing, whether it is a main lift rotor or a tail rotor. A balanced rotor is one in which the blades are held at equal angles about the axis of rotation and the rotor tips rotate in the same horizontal plane relative to each other to produce equal lift in each speed range. Although this plane will be different at each flight speed, the important thing is that at a given speed all tips rotate in the same plane and produce equal lift. It is known how much each wing deforms relative to the other at different speeds, and in the past this type of deformation has been measured visually or empirically, and the results are unreliable. Not only that, but the evaluation also took a considerable amount of time.

It has been shown that the present invention, which measures the distance from a transmitter/receiver to the tip of each rotor blade, for example at a particular point in the rotational trajectory of that blade tip, yields surprisingly accurate results, but this result does not depend on the received signal. is obtained from the calculator in a very short time after inputting it into the calculator.

A preferred type of transceiver is a dual Doppler radar system, with two transceivers in close proximity transmitting slightly different frequencies between each other, and the phase difference of the reflected signals being a measure of the distance of the reflected surface. Single-pulse transceivers using frequency modulated carrier pulses may also be used. Each of these methods can produce an indication of the distance from the transceiver to the tip of the wing, so if the transceiver is placed in an appropriate position,
The measured distance can be used as a measure of the wing's deformation from the mean plane. Transmitters and receivers should generally be kept at a considerable distance from this plane, usually around 30 degrees. By relating the detection time of the received radiation to the periodic reference pulse, any angular deformation of the wing in the horizontal plane about the axis of rotation can also be determined.

Alternatively, the transmitter may be a collimated beam of laser or other radiation, in which case the reflected beam shifts according to the deformation of each rotor blade, e.g. A particular receiver receiving the reflected beam changes with the amount of deformation and emits a signal indicative of this deformation. This kind of approach has particular value in the case of tail rotors, where there is usually no mutual movement about the axis of rotation within the field of view.

By inputting the received information into a suitably programmed calculator, the measured deformations can be obtained in a very short time after the test and, in fact, can be carried out on the helicopter to measure the deformations of the main rotor blade tips. a laser beam transceiver mounted on the tail boom for measuring the deformation of the tail rotor wing, and a calculator in the cabin to receive signals from both systems; It is indeed possible to obtain complete results of tests carried out at each flight speed. In that case, as will be described later (see FIG. 6), the distance to the tip of each wing is measured, so that maintenance personnel can immediately make necessary adjustments regarding wing attachment once the helicopter lands after the test. The present invention includes a device of this type and a method of using the same.

A related invention is a method for displaying the results obtained by the above-mentioned method, but in this case the method is applied to the deformation of individual wings of a multi-blade helicopter rotor, and according to this related invention, The deformation of the wing or wings during a rotation cycle is graphically displayed for one or more flight speeds. In particular, the average deformation position of all wings for a particular speed can be determined and the display can be graphically related to this average deformation.

Another possibility is to represent the deformation of the entire wing in the direction perpendicular to the plane of rotation and angularly between each other in terms of the average deformation for a given flight speed.

It is also possible to display a trend diagram showing curves for each wing showing the wing deformation in rows at each of the various speeds; It is also possible to create a curve for each wing, or to display a curve for one wing.

Detecting and identifying defective intra-wing dampers by detecting temporal irregularities in the passage of individual rotor blades past predetermined points relative to revolution-by-rotation markers, and displaying the results to the operator. Is possible. Traditionally, this has not been possible with any degree of certainty.

While the invention may be carried out in various ways, one embodiment will be described by way of example with reference to the accompanying drawings, in which: FIG.

Helicopter rotors, both when they were manufactured and afterwards.
It is required that the rotor blades be equally angularly spaced when viewed in plan and that the rotor blade tips are always balanced so that they all move in the same plane substantially perpendicular to the axis of rotation. How to adjust the wing mounting to achieve this balance would be completely clear if the degree of unbalance of each blade was known, but to date there is no satisfactory method of accurately detecting the amount of unbalance of an individual blade. has not been discovered.

According to the invention, the dual Doppler transceiver has 11
As shown in , it is installed on one side of the cabin, just below the door 12, so that its transmission center axis is tilted upward at an angle of about 35 degrees, and when the rotor rotates, it is blocked by the tip of the rotor blade 13. There is. FIG. 2, which is a schematic plan view, shows that the central axis of the transmitter 14 is sloped upwardly as well as inwardly in the preferred arrangement. According to Fig. 4, the cone 15 centered on the central axis of the transmitter has an upward angle, and the nose of the helicopter -
Indicates that it is oriented at an angle with the tail axis. The exact location does not matter as long as the tip of the rotor can provide a reflected signal to the Doppler receiver. Other possible arrangements are shown at 11' in FIG. The tip of the rotor blade has a small metal reflective surface fixed to it to obtain a good reflected signal.

Figure 1 shows the rotor blades 13 hanging down when the rotor is not rotating, but when the rotor starts rotating, the blades tend to lift and extend outward horizontally, raising the helicopter. 5th start
It has an upwardly conical shape as shown schematically at 16 in the figure.

FIG. 5 is a schematic diagram in a vertical plane containing the rotor axis and the transceiver 11. FIG. The extreme positions that the wing assumes in its plane when the rotor is at rest and when it is producing maximum lift are indicated by "S" and "L"respectively; FIG. "S" and "L" for moving the container
The movement of the wing tip between the transmitter and the receiver results in a significant difference in the distance (R _S ) or (R _L ) from the transmitter/receiver to the wing tip.

The transmitter/receiver is from "Introduction to Radar Systems".
The system uses a multi-frequency carrier radar system of the type described by Skolnik on page 106, in which the two transmitters and receivers shown at 18 and 19 in FIG. Transmit radio waves ( ₁ ) and ( ₂ ). The reflected signals from the wing tip to the receiver are ( ₁ + d ₁ ) and ( ₂ + d ₂ ), where d ₁ and d ₂ are Doppler frequency components derived from the velocity components of the wing tip toward the transmitter and receiver. be. The phase difference between the reflected signals is a direct measure of the distance of the wingtip from the transmitter and receiver, and thus is a nearly direct measure of off-track conditions. Each wing tip provides a reflected signal to each receiver so that there are three pairs of reflected signals for each rotor rotation, as indicated generally at 22 in FIG. Therefore, from the phase difference between the reference pulse 21 synchronized with the rotation of the rotor and the reflected signal 22, it is possible to determine which wing tip the input reflected signal 22 is from.

Now, assuming that the difference between frequencies ( ₁ ) and ( ₂ ) is very small compared to ( ₁ ), (d ₁ ) and (d ₂ ) are very small compared to frequencies ₁ and ₂ , and (d ₁ ) and (d ₂ ) are approximately equal, so assuming that they are equal, the distance R between the transmitter/receiver and the wing tip can be determined by the following equation.

R=c・t/4π・T...(1) Here, c is the propagation speed of the radio wave, t is the phase difference between the reflected signals ra and rb as shown in Figure 6, and T is the two carrier frequencies. is the frequency difference (=2-1). The frequency difference T (=2-1) becomes a constant value if each carrier frequency is set, but the smaller the value, the higher the measurement sensitivity to the phase difference t can be. Since the calculation is performed using the phase difference t of the reflected signals, even if the speed of the blade changes, minute displacements can be measured with high accuracy without depending on the change.

Note that in the normal Doppler radar system, the distance R is determined by the following formula.

R=c・t/4π・...(2) Here, is the carrier frequency. As is clear from comparing equations (1) and (2), in equation (1), (2)
The carrier frequency in the equation is replaced by the frequency difference T, and it can therefore be seen how the measurement method using equation (1) can measure minute displacements.

This method of measuring the distance of a rotating wing tip from the transceiver 11 has been found to be surprisingly accurate, and analysis of the received signals has shown that the total rotational position encountered by the weight 15 from the transceiver is The amount of upward or downward displacement of each blade tip from the mean plane of rotation of the rotor blade tip can be known with great precision.

Furthermore, upon closer examination of Figure 6, the analysis shows that each blade is located horizontally at equal angular intervals;
that the center of the reflected burst of radiation can be associated with the reference repetition pulse 21 in such a way that it becomes clear whether the spacing between one wing and the wing that precedes it is greater or less than the spacing between that wing and the wing that follows it; It shows.

Once this information is available, it will be abundantly clear how the wing attachment should be adjusted to correct for any off-trajectory conditions or forward/backward errors.

Since the action of the wing varies considerably at various rotor speeds or flight speeds, this book is used to record the results of tests performed when the rotor is rotating in a grounded condition and while the helicopter is in the air or in flight at various speeds. The invention contemplates carrying electronic recording and computing equipment onboard a helicopter.

The calculator in the recording device can be programmed to display information in an easily readable manner.

For example, FIG. 7 shows the VDU display for a special four-wing helicopter at speeds of 100 knots, 120 knots, and 140 knots, respectively. The horizontal line indicated by 24 is calculated as the average height of the rotor wing tip where the rotor wing tip crosses the transmitting weight.
The height of each wing tip is shown relative to this average value. The vertical markings are graduated in inches as shown at 25, and 25 indicates the number of the four wings. The display at 120 knots shows that the second wing is high at this speed, while at 100 knots it is low.
Furthermore, it has been confirmed that minute variations can be measured with high accuracy even when the speed of the blade differs.
In the representation in Figure 7, all wings are angularly precisely located, but in the alternative representation at 60 knots shown in Figure 8, the second wing is angularly precisely located, but It can be seen that the first and fourth wings are leading from their normal angular positions, while the third wing is lagging behind.
Maintenance personnel who see this display can easily make appropriate adjustments to the wing installation.

The computer can also be programmed to collect the results for all four wings at various speeds and display them as a composite display as shown in FIG. Take readings for each of the test speeds for each of the four wings along various straight lines, whether on the line or on one side or the other of the line, and whether the wing tip is at the average level during the corresponding test. Display depending on whether it is above or below this level. For example, in Figure 9, the first wing is in a low position when levitating, but if the flight speed is 120 or
It shows an increase towards the average level as speed increases until it is reliably just below the average level in the range of 140 knots.

Figure 10 is a representation corresponding to Figure 9 for a particular wing (in this case wing 4), but since it shows the "trend" curve for only one wing, the 2
8, it is possible to scale the vertical axis in inches of deformation.

As the rotor makes many revolutions during the test, the readings from each revolution are recorded and accumulated, and an average reading is compiled.

It is possible to perform tests on a number of different helicopter designs to reveal the complex characteristics of the rotating object and to obtain the characteristics of the helicopter design.
That is, a representation of the unique characteristic vibrations at a particular airspeed for a given helicopter design is as shown in FIG. This characteristic can be recorded and entered into a computer prior to displaying the measurements made on a particular helicopter, and then the actual measured vibrations on that particular helicopter can be displayed as shown in Figure 12. . For example, by programming the box as shown in 28, the calculated maximum permissible vibration amplitude of each part is indicated, and the user who is looking at the measurement characteristics is immediately informed of the rotor, etc., which may or may not be clearly indicated in this way. It is also possible to immediately determine whether or not the parts are satisfactory. For example, the vibration peak value at 29 extends above box 28, which is unacceptable, while the peak value 31 does not extend above box 28, and the vibration amplitude for the main rotor blade is unacceptable. It shows that it is at a possible level.

In order to be able to obtain a balance of the tail rotor of a helicopter, it is necessary to measure the deformation of each wing relative to the rotational mean plane of the wing tips tested at one or more flight speeds. In Figure 13,
Although the rotor is shown as having two wings 111, in common with most helicopter tail rotors, the wings do not have a degree of freedom of movement about the axis of rotation 112, so any possible deviations from the rotor's trajectory are caused by the tail rotor. It can only be displayed as a deformation of the wing tip to or from the boom 113.

According to the invention, the blade tip deformation during rotation of the rotor is measured by a laser beam and an array of photodiodes. These are housed in a light box 114 mounted on the boom, and a laser beam 115 from a laser diode 116 is intercepted by the wing as the wing rotates, as shown schematically at 117 in FIG. Each wing 111 has a reflective strip 118 near its end, which may be a pasted aluminum foil or, for example, an area with reflective glass beads. The light reflected from the area 118 is transmitted to a light diode array 11 mounted within the light box.
9, this diode array extends within the range defined by the two arrows 121.

The undeformed rotor blades 111, ie those in the normal theoretical plane, are shown in solid lines in FIG.
It can be seen that the reflected laser beam 122 is incident on the light scattering diode in the center of the diode array.

On the other hand, if the wing were to be deflected a distance "d" toward the boom 113 as shown by the dashed line at 111', the reflected laser beam 123 would be received by a photodiode near one end of the diode array 119. . This simply means that the reflection point 124 is the undeformed wing 11.
1, or the deformation "d" is closer to the light box than the reflection point 125 for hub axle 11.
An angular deformation centered on 2, so the reflective surface 1
It may also be because the plane of 18 has an angle to the plane of the undeformed wing.

In the example of FIG. 14, some numerical sequences are shown. The rotor tip is at a radius of 185 cm from the hub axis 112, and the undeformed wing surface is 300 cm from the surface of the light box 114 and perhaps 10 cm from the side of the boom 113. The amount of deformation that will be experienced is unlikely to be more than 3 or 4 cm, but
The array of optical devices is arranged so that the reflected beam 122 or 12
3 should be such that a particular diode in diode array 119 receiving light can produce an accurate indication of the amount of wing deformation.

Signals can be obtained by reflection from black coatings or other reflective surfaces on the rotors to act as reference signals for determining the rotation of each rotor, thus correlating the outputs from the photodiodes to those reference signals. identification of the wing producing the signal.

An accelerometer 127 is attached to the hub bearing and the output thereof is waved to remove components above and below the rotational fundamental frequency, creating a fundamental sine wave that can be correlated to the periodic pulse signal from the black coating or other reference surface. can be used to determine the dynamic imbalance of the tail rotor and then produce an indication of the dynamic imbalance of the tail rotor in a known manner by checking the phase angle between the sinusoidal peak and the black coating signal.

This device measures the degree of unbalance of the tail rotor.
It may be used in conjunction with the apparatus that is the subject of FIGS. 1-6 to measure main helicopter rotor imbalance and visually display the results.
The calculator described above may therefore receive input from lightbox 114 and accelerometer 127.

Although the present invention has been described as being applied to measuring the deformation of a blade tip on a rotor, it goes without saying that it can be applied to measuring the deformation of each point on any rotating object. For example, the signal may be received from a propeller, fan, or rotating turbine rotor, or from a location along a rotating shaft that is rotating and undergoing critical speed deformations.

To restate, although the invention has been described with respect to FIGS. 3 and 6 as using a dual Doppler method to obtain a phase difference signal indicative of the distance of the component producing the reflection, the frequency within each pulse is It would also be possible to use a pulsed frequency modulated carrier signal which is modulated from beginning to end and whose amplitude is likewise modulated. The distance can be similarly determined by using signals selected from the reflected pulse at the beginning and end of the pulse.

[Brief explanation of drawings]

FIG. 1 is a side view of a helicopter equipped with a trajectory and unbalance detector according to the present invention, FIG. 2 is a plan view corresponding to FIG. 1, and FIGS. 3, 4, and 5 are trajectory and unbalance detectors. Diagrams useful for explaining the operation of the detector; Fig. 6 shows the signal characteristics used in this method; Fig. 7 shows the signal characteristics used in this method;
Figures 1 to 12 are various displays of the trajectory and unbalance information determined by the test, Figure 13 is an elevation view of the tail of the helicopter showing the tail rotor, and Figure 14 is the arrow in Figure 13. FIG. 11...transmitter/receiver, 12...helicopter door, 13,
111... Helicopter rotor, wing, 14... Transmission radiation beam, 18, 19... Dual transceiver, 113... Tail boom, 114... Light box, 115... Laser beam, 116... Laser diode, 118
...Beam reflection part, (reflection strip), 119...
Detector row, diode row, 122, 123... Laser light reflected beam, 127... Accelerometer.

Claims (1)

[Scope of Claims] 1. A step of emitting an electromagnetic wave beam toward the tip of a rotor blade of the helicopter using a transmitter attached to the helicopter body when the tip is rotating during flight, and the helicopter body receiving the reflected wave of the electromagnetic beam from the tip of the rotating blade by a receiver attached to the rotating blade; and inputting the reflected wave to each rotating blade based on at least the reflected wave signal. A method for measuring a rotating body, comprising: calculating the position of the tip of the blade; and displaying the calculated position of the tip of the blade. 2. The method of measuring a rotating body according to claim 1, wherein the reflected wave signal is input to a computer in order to calculate the position of the tip of the blade. 3 Display format that displays the deformation of all blades,
or in a display format displaying the deformation of at least one blade at different speeds, the analysis results being visually displayed in the helicopter while the measurements are being carried out. Method of measuring the described rotating body. 4 A transmitter that is attached to the helicopter body and emits an electromagnetic wave beam toward the tip of the helicopter's rotor blade when it rotates during flight; a receiver that receives the reflected wave of the electromagnetic beam from the tip of the rotating blade; 1. A device for measuring a rotating body, comprising: a computer for calculating; and means for displaying the calculated position of the tip of a blade. 5. Rotation according to claim 4, characterized in that it has a visible display screen controlled by a computer to display the deformations of all the blades or the deformations of at least one blade at different speeds. A device that measures the body. 6. The method of measuring a rotating body according to claim 1, wherein the distance between the tip of the blade and the transmitter and receiver is determined by transmitting and receiving an electromagnetic wave beam using a multi-frequency carrier wave radar method. 7. The method of measuring a rotating body according to claim 6, wherein the reflected signal of each blade is determined based on the phase difference between a synchronized pulse signal synchronized with the rotation of the rotor and the reflected wave.