A coaxial dual-rotor blade tip distance monitoring method

Abstract

The application discloses a kind of coaxial dual-rotor blade tip distance monitoring methods, comprising the following steps: adjusting sensor direction to preset direction, adjusting sensor position to the position in the upper and lower blade coincident position;Make the blade of helicopter start rotating, and data is collected after speed stabilizes;From the data collected, the time of upper blade and lower blade passing through optical sensor working area is calculated in a certain period of data;The height of each piece of blade is calculated by the time of upper blade and lower blade passing through optical sensor working area;The minimum value of upper blade is selected and the maximum value of lower blade is subtracted to obtain the blade distance.It can realize the technical requirements of single sensor monitoring the height of upper and lower two pairs of blades of coaxial dual-rotor, and through the design of specific monitoring technical scheme, the purpose of real-time monitoring the tip distance of coaxial dual-rotor is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aviation test technology, and relates to a method for monitoring the tip distance of upper and lower rotors of a coaxial dual-rotor, which is used for rotor dynamic state monitoring of a coaxial dual-rotor helicopter. BACKGROUND

[0002] The coaxial dual-rotor system is one of the significant features of the coaxial dual-rotor helicopter, which is different from other helicopters. The system has two pairs of completely same rotors, one pair of upper rotors and one pair of lower rotors, which are installed on the rotor shaft. The two pairs of rotors rotate in opposite directions, and the torque items offset each other, so the coaxial dual-rotor helicopter does not need to provide the tail rotor for providing the counter torque.

[0003] Compared with the single-rotor helicopter, the coaxial dual-rotor helicopter has one more key monitoring data, that is, the vertical distance of the upper and lower rotors, which corresponds to the monitoring parameter of the tip distance, as shown in the formula. Figure 1 The tip distance of the upper and lower rotors of the coaxial dual-rotor helicopter cannot be too large or too small in order to avoid the high center of gravity. Once the tip distance is too small, when the blades swing up and down at high speed, the blades of the two pairs of counter-rotating rotors are likely to collide, causing a major safety accident of destroying the helicopter and killing people. In order to avoid the collision of the blades of the two pairs of rotors, it is necessary to monitor the tip distance of the coaxial dual-rotor in real time. Once the tip distance approaches or is less than the set threshold, some flight movements and operations must be stopped. SUMMARY

[0004] To achieve the above purpose, the present application adopts the following technical scheme:

[0005] A coaxial dual-rotor tip distance monitoring method comprises the following steps:

[0006] Adjusting the direction of the sensor to a preset direction and adjusting the position of the sensor to a position within the overlapping position of the upper and lower blades;

[0007] Starting the rotation of the blades of the helicopter, and collecting data after the rotation speed is stabilized;

[0008] Extracting the data of a certain period from the collected data to calculate the time when the upper blades and the lower blades pass through the working area of the optical sensor;

[0009] Calculating the height of each blade by the time when the upper blades and the lower blades pass through the working area of the optical sensor;

[0010] Selecting the minimum value of the upper blades and subtracting the maximum value of the lower blades to obtain the tip distance.

[0011] In a further scheme of the present application, the adjusting of the direction of the sensor to a preset direction is specifically:

[0012] The detection direction of the sensor is adjusted to be consistent with the rotating direction of the lower rotor and vertically upwards.

[0013] In a further aspect of the present application, the method of making the blades of the helicopter start rotating and collecting data after the rotating speed is stabilized specifically comprises:

[0014] The optical sensor is triggered to collect data at the position where the blades coincide, ensuring that only one blade passes above the sensor at any time, and the trajectory data is collected after the rotating speed of the helicopter is stabilized.

[0015] In a further aspect of the present application, the height of each blade is calculated by the time that the upper blade and the lower blade pass through the working area of the optical sensor, specifically by the following formula:

[0016]

[0017] h represents the relative height of the measured blade to the optical sensor;

[0018] l represents the horizontal distance from the optical sensor to the rotor shaft;

[0019] β represents the angle between the optical sensor and the horizontal plane;

[0020] α represents the angle between the two photosensitive devices inside the optical sensor;

[0021] ω represents the rotating speed of the rotor;

[0022] Δt represents the time that the blade passes through the working area of the optical sensor, Δt = T2-T1.

[0023] The advantages of the present application are as follows: the technical requirements of monitoring the heights of the upper and lower blades of the coaxial double rotors by a single sensor are achieved, and the purpose of real-time monitoring of the tip clearance of the coaxial double rotors is achieved by designing a specific monitoring technical solution. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 A multiple optical sensor tip clearance monitoring effect diagram according to the present application;

[0026] Figure 2 A helicopter upper and lower blade distribution and optical sensor layout area schematic diagram according to the present application;

[0027] Figure 3 A trajectory signal diagram generated by a paddle blade completely passing through an optical sensor working area according to the present application;

[0028] Figure 4 A schematic diagram of a paddle blade passing through an optical sensor in a forward direction according to the present application;

[0029] Figure 5 A schematic diagram of a paddle blade passing through an optical sensor in a reverse direction according to the present application; DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The sensor selected in the present application is a one-way optical sensor, which mainly monitors the trajectory parameters of a helicopter rotor. The optical sensor has two photosensitive devices therein, which have different working mechanisms, so the direction of the rotor blade passing through the working area of the sensor must be strictly implemented according to the requirements. The optical sensor shell is marked with an arrow, and when monitoring a single-layer rotor, the sensor needs to be placed on the ground, and the direction of the shell arrow is consistent with the rotation direction of the rotor, that is, the forward direction.

[0032] When the rotor rotating blade passes through the working area of the optical sensor in the forward direction, the sensor senses the light change and generates a trajectory signal. As shown in Figure 4 When the leading edge of the blade passes through the No. 1 photosensitive device, the photosensitive device senses a slight change in light brightness, generating a first pulse T1; when the leading edge of the blade passes through the No. 2 photosensitive device, the photosensitive device senses a change in light brightness, generating a second pulse T2; when the trailing edge of the blade passes through the No. 2 photosensitive device, the photosensitive device senses a change in light brightness, generating a third pulse T3, that is, a piece of the blade passes through the optical sensor, and the sensor generates three pulse signals to represent the trajectory parameters of the blade, as shown in Figure 3

[0033] When the rotor rotating blade passes through the working area of the optical sensor in the forward direction, according to the trajectory monitoring principle of the optical sensor, the relative height of a piece of the measured blade to the optical sensor is:

[0034]

[0035] h represents the relative height of the measured blade to the optical sensor;

[0036] represents the horizontal distance from the optical sensor to the rotor shaft.​

[0037] represents the angle between the optical sensor and the horizontal plane;

[0038] represents the angle between the two light-sensitive devices inside the optical sensor;

[0039] represents the rotational speed of the rotor;

[0040] represents the time of the blade passing through the working area of the optical sensor, = T2-T1.

[0041] Because the upper and lower rotors of the coaxial dual-rotor helicopter rotate in opposite directions, in order to monitor the blade tip distance of the two rotors using the same optical sensor, it is necessary to explore the reverse working mechanism of the optical sensor. When the rotor rotates the blade in the reverse direction through the working area of the optical sensor, because the blade first passes through the No. 2 light-sensitive device and then passes through the No. 1 light-sensitive device, it is different from the normal working mechanism of the optical sensor. As shown in Figure 5 , when the leading edge of the blade passes through the No. 2 light-sensitive device, the light-sensitive device senses a slight change in light brightness, generating a first pulse T1; when the trailing edge of the blade passes through the No. 2 light-sensitive device, the light-sensitive device senses a change in light brightness, generating a second pulse T2; when the leading edge of the blade passes through the No. 1 light-sensitive device, the light-sensitive device senses a change in light brightness, generating a third pulse T3, and the optical sensor also generates three pulse signals, similar to Figure 3 . It can be seen from Figure 5 that when the rotor rotates the blade in the reverse direction through the working area of the optical sensor, the time of the blade passing through the working area of the optical sensor in formula (1) is = T3-T1.

[0042] In order to more accurately monitor the blade tip distance of the upper and lower rotors of the coaxial dual-rotor helicopter, the invention adopts a vertical upward collection method of the optical sensor, ensuring that the collection points of the upper and lower blades have the same distance from the rotor shaft, avoiding the tilt of the optical sensor causing the collection points of the upper and lower blade trajectories to have different distances from the shaft, and further causing the blade tip distance to deviate. At this time, = 90° in formula (1), so formula (1) can be simplified as:

[0043]

[0044] When the blade passes through the working area of the optical sensor in the forward direction, = T2-T1, and when the blade passes through the working area of the optical sensor in the reverse direction, = T3-T1.

[0045] The height of the upper and lower rotors is calculated by formula (2), and the minimum value of the height difference between the upper and lower blades is the minimum blade tip distance of the coaxial dual-rotor, simply referred to as the blade tip distance. When the blade tip distance is close to or less than the set threshold value, there is a risk of collision between the upper and lower blades.

[0046] II. Technical scheme for monitoring the blade tip distance of a coaxial dual-rotor

[0047] The principles and technical solutions of the present application are applicable to the monitoring of the upper and lower rotor tip distance of all coaxial dual-rotor helicopters. The following will take the monitoring of the rotor tip distance of a Kamov-28 coaxial dual-rotor helicopter as an example to illustrate the implementation of the technical solutions.

[0048] The Kamov-28 helicopter has three blades for each of the upper and lower rotors. When viewed from above, the lower rotor clockwise rotor has blades 2, 4 and 6 as shown in Figure 2 , and the upper rotor counterclockwise rotor has blades 1, 3 and 5 as shown in Figure 2 . There are six positions where the upper and lower blades coincide, as shown by the dashed lines in Figure 2 . In order to avoid the influence of the coincidence of the upper and lower blades on the signal collection of the optical sensor, the optical sensor needs to be placed in the non-coincidence area of the blades, such as the areas ① to ⑥ shown in Figure 2 .

[0049] The method of the present application comprises the following steps:

[0050] Step 1, adjust the direction of the optical sensor to ensure that the arrow direction of the sensor housing is consistent with the rotation direction of the lower rotor and vertically upward. Place the optical sensor in area ①, adjust the distance between the sensor and the shaft center, and make the sensor collect the trajectory data from 70% of the blade to the blade tip position. Figure 2

[0051] Step 2, trigger the optical sensor to collect data at the positions where the blades coincide, and ensure that only one blade passes above the sensor at any time. Start collecting trajectory data when the helicopter speed is stable.

[0052] Step 3, extract data for analysis and processing at a certain period, such as 40 revolutions, from the collected trajectory data. The extracted data is in a cycle of T11, T12, T13, T21, T22, T23, T31, T32, T33, T41, T42, T43, T51, T52, T53, T61, T62, T63, a total of 40 cycles. Described by the optical sensor in area ①, T11, T12, T13 are the trajectory data of the upper layer No. 1 blade, T21, T22, T23 are the trajectory data of the lower layer No. 2 blade, T31, T32, T33 are the trajectory data of the upper layer No. 2 blade, T41, T42, T43 are the trajectory data of the lower layer No. 3 blade, T51, T52, T53 are the trajectory data of the upper layer No. 3 blade, and T61, T62, T63 are the trajectory data of the lower layer No. 1 blade (the blade numbers in the description change accordingly with different optical sensor areas). Lower blade = Tn2-Tn1, upper blade = Tn3-Tn1. Take the average of 40 cycles for the same blade to obtain: Figure 2

[0053] i is an integer ​​

[0054] Step 4, put each blade of step 3 into formula (2), calculate each piece of blade height, in turn, the upper layer No. 1 blade height h t1 , the lower layer No. 2 blade height h b2 , the upper layer No. 2 blade height h t2 , the lower layer No. 3 blade height h b3 , the upper layer No. 3 blade height h t3 , the lower layer No. 1 blade height h b1 ,

[0055] Step 5, select the minimum value of the upper layer each piece of blade height, that is, ht1, ht2, ht3, and the maximum value of the lower layer each piece of blade height, that is, hb1, hb2, hb3, the minimum value of the upper layer blade height minus the maximum value of the lower layer blade height is the minimum blade tip distance monitored by the optical sensor in Figure 2 the ① area.

[0056] Step 6, according to the principles of steps 1-5, place optical sensors in the 6 areas in Figure 2 , monitor the blade tip distance of the coaxial dual-rotor helicopter at multiple angles, Figure 1 the blade tip distance monitoring effect of multiple optical sensors.

Claims

1. A coaxial twin-rotor blade tip distance monitoring method, characterized by, The method comprises the following steps: adjusting the sensor direction to a preset direction and adjusting the sensor position to a position within the upper and lower blade overlap position, wherein the adjusting the sensor direction to a preset direction specifically comprises adjusting the detection direction of the sensor so that the detection direction is consistent with the rotation direction of the lower rotor and vertically upwardly detects; causing the blades of the helicopter to start rotating and collecting data after the rotation speed is stabilized, specifically comprising triggering the optical sensor to collect data at the blade overlap position to ensure that only one blade passes above the sensor at any time, and starting to collect trajectory data when the rotation speed of the helicopter is stabilized; extracting certain period data from the collected data to calculate the time for the upper blade and the lower blade to pass through the working area of the optical sensor; calculating the height of each blade through the time for the upper blade and the lower blade to pass through the working area of the optical sensor, specifically obtaining the height of each blade through the following formula: ； represents the relative height of the measured blade to the optical sensor; represents the horizontal distance of the optical sensor to the rotor axis; represents the angle of the optical sensor with the horizontal plane; denotes the included angle of the two light-sensitive devices inside the optical sensor; represents the rotational speed of the rotor; represents the time the blade passes through the optical sensor working area; selecting the minimum value of the upper blade and subtracting the maximum value of the lower blade to obtain the inter-blade distance.

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