Helicopter ground resonance test system and test method

Abstract

The invention belongs to the technical field of flight test, and particularly relates to a helicopter ground resonance test system and test method. Standards or regulations only provide requirements for ground resonance, but do not provide a specific implementation mode of a ground resonance verification test. Through corresponding calibration operation, the corresponding relation between the lift force of the rotor wings and the collective pitch position is obtained, the pull force of the rotor wings which is difficult to observe visually is converted into the collective pitch position which is easy to observe visually, and a driver controls the lift force by controlling the collective pitch; ground testers can observe overload acceleration signals of all measurement positions and linear displacement signals of a damper (or a buffer strut) in real time through the portable tablet computer, the helicopter state under excitation can be obtained more visually, and ground resonance phenomenon trends can be found in time and handled emergently when possibly existing. The driver and an onboard driver serve as emergency condition judgment backups for each other, the test risk is reduced, and the test safety coefficient is improved; through the external fuel oil cutting device, fuel oil and power of the helicopter can be cut off in time when the helicopter possibly has a ground resonance phenomenon trend and needs emergency treatment, so that the safety of testers such as a driver and the like is guaranteed. The working intensity of a driver is reduced, and the operability of the test is enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of flight testing, and in particular relates to a helicopter ground resonance testing system and a testing method. Background Art

[0002] During the development of new helicopter models, ground resonance is an essential test. There are corresponding standards or regulations for ground resonance, but the standards or regulations only put forward requirements for ground resonance, but do not give specific implementation methods for ground resonance verification tests. Summary of the invention

[0003] The present invention designs a helicopter ground resonance test system and a test method for a helicopter, which are used to verify the ground resonance of the helicopter under required working conditions.

[0004] In one aspect, the present invention provides a helicopter ground resonance test system, which includes a data collector, a GPS antenna, an overload acceleration sensor, a linear displacement sensor, a strain gauge, a network switch, a portable tablet computer and an external fuel cut-off device, wherein the overload acceleration sensor is installed on the main pilot's footrest floor, the main reducer upper casing, the main reducer mounting platform, the cabin floor and the tail reducer; the linear displacement sensor is installed on the damper of the helicopter's skid landing gear or the buffer support position of the three-point landing gear; the strain gauge is installed on the main rotor shaft of the helicopter; the data collector collects and records the original machine signal of the extraction helicopter, the GPS antenna time signal, the overload acceleration sensor signal, the linear displacement sensor signal and the strain gauge signal, and sends them to the portable tablet computer through the network switch; the portable tablet computer is used to analyze and judge the resonance situation and control the external fuel cut-off device.

[0005] Advantageously, by judging that the time history curve of the overload acceleration data does not have a divergent trend, it can be judged that the helicopter does not have a ground resonance phenomenon.

[0006] Advantageously, the absence of ground resonance in the helicopter can be determined by combining the displacement time history curve with real-time observation of the absence of divergence of the damper or buffer strut during the test.

[0007] Advantageously, two ends of the linear displacement sensor are respectively mounted on two ends of the damper or buffer support.

[0008] Advantageously, the data collector and the network switch are mounted on a test equipment mounting bracket on the floor inside the helicopter cabin by bolts.

[0009] Advantageously, the portable tablet computer is used to receive and display in real time the test data broadcasted by the network switch via mesh mode, and provides it to ground test personnel outside the helicopter to observe the test data in real time and take emergency measures based on the data to ensure test safety and reduce test risks.

[0010] Advantageously, the original engine signals of the helicopter include a rotor speed signal, a collective pitch position signal and an engine torque signal.

[0011] In another aspect, the present invention further provides a helicopter ground resonance test method, using the above-mentioned helicopter ground resonance test system, the method comprises the following steps:

[0012] S1. Install test equipment, calibrate main rotor shaft tension and strain gauge load, and calibrate collective pitch position;

[0013] S2, power on the helicopter and the test system, and start the helicopter engine;

[0014] S3. Under working conditions, the helicopter pilot operates the collective pitch lever to adjust the collective pitch position to the calibrated position, and performs disturbances along the rotor rotation direction at a set frequency and a displacement with a radius not exceeding 9 mm. The helicopter pilot feels whether the helicopter has a tendency of vibration divergence, and the ground test personnel outside the helicopter observe the acceleration signal and displacement signal of each measuring position in real time through a portable tablet computer to see if there is a tendency of vibration divergence. If either party finds that the vibration has a tendency of divergence, the control stick disturbance should be stopped immediately, the engine fuel should be cut off, and the test should be terminated. If neither party finds a tendency of vibration divergence;

[0015] S4. After completing all the test contents, the helicopter shuts down the engine, and the helicopter and the test system are powered off;

[0016] S5. Download the recovered data.

[0017] Advantageously, the data is analyzed offline, and if the acceleration data and displacement data at each measurement position do not have a divergent trend, it is determined that the helicopter does not have ground resonance.

[0018] Beneficial effects: The helicopter ground resonance test realized by the present invention can obtain the corresponding relationship between the rotor lift and the collective pitch position through corresponding calibration operations, and convert the rotor thrust that is difficult to observe intuitively into the collective pitch position that is easy to observe intuitively. The driver can control the lift by controlling the collective pitch, which reduces the driver's workload and enhances the operability of the test; ground test personnel can observe the overload acceleration signal of each measuring position and the linear displacement signal of the damper (or buffer strut) in real time through a portable tablet computer, and more intuitively obtain the helicopter state under excitation. When there is a tendency for ground resonance to occur, they can promptly discover and handle the situation in an emergency, and serve as a backup for emergency judgment with the onboard pilot, thereby reducing the test risk and improving the test safety factor; ground test personnel can use an external fuel cut-off device to promptly cut off the fuel and helicopter power when there is a tendency for ground resonance to occur in the helicopter and emergency handling is required, thereby ensuring the safety of the pilot and other test personnel.

[0019] The features, functions, and advantages that have been discussed can be achieved independently in various examples or may be combined in yet other examples. Further details of the examples can be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Examples, as well as preferred modes of use, other objects and description thereof, will be best understood by reference to the following detailed description of examples of the invention when read in conjunction with the accompanying drawings, in which:

[0021] Figure 1 It is a schematic diagram of the composition relationship of the test system;

[0022] Figure 2 Schematic diagram of the test method. DETAILED DESCRIPTION

[0023] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0024] See also Figure 1 The ground resonance test system includes a data collector, a GPS antenna, an overload acceleration sensor, a linear displacement sensor, a strain gauge, a network switch, a portable tablet computer, an external fuel cut-off device and cables.

[0025] The data collector is connected to the helicopter signal line, GPS antenna, sensor and strain gauge through cables, and is used to collect and record the original machine signal (rotor speed signal, total pitch position signal, engine torque signal), GPS antenna time signal, overload acceleration sensor signal, linear displacement sensor signal, strain gauge signal (load signal) of the extraction helicopter. The recorded data can be broadcast to a portable tablet computer through a network switch during the test to display the test data in real time, or downloaded and recovered for post-analysis after the test. The data collector is installed on the test equipment mounting frame on the floor inside the helicopter cabin and fixed by bolt connection.

[0026] In one embodiment, the data collector is a KAM-500 data collector produced by ACRA of Ireland.

[0027] The GPS antenna is used to provide the GPS time signal to the data collector as the time reference in the time history curve of each test parameter. It is connected to the data collector using a cable. In order to enhance the strength of the search satellite signal, it should be installed in principle in a position where the helicopter is unobstructed or has weak obstruction, usually on the upper part of the helicopter's nose.

[0028] In one embodiment, the GPS antenna is an L1 antenna produced by NovAtel, Canada.

[0029] The overload acceleration sensor is used to obtain the overload acceleration signal at the helicopter's main pilot's foot pedal floor, main reducer upper casing, main reducer mounting platform, cabin floor, tail reducer and other locations. By judging that there is no divergence trend in the time history curve of the overload acceleration data, it can be judged that the helicopter has no ground resonance phenomenon. The overload acceleration sensor is installed at the helicopter's main pilot's foot pedal floor, main reducer upper casing, main reducer mounting platform, cabin floor, tail reducer and other locations by bolt connection. The overload acceleration sensor is connected to the data collector using a cable.

[0030] In one embodiment, the overload acceleration sensor is a 773 overload acceleration sensor produced by ENDEVCO Corporation of the United States.

[0031] The linear displacement sensor is used to obtain the displacement of the damper of the skid landing gear (or the displacement of the buffer strut of the three-point landing gear). It is installed at the position of the damper (or the buffer strut of the three-point landing gear) of the helicopter's skid landing gear. The two ends of the linear displacement sensor are respectively installed at the two ends of the damper (or buffer strut). After installation, calibration is performed to obtain the linear relationship formula between the sensor output voltage and the displacement of the damper (or buffer strut). The formula is input into the data analysis module to obtain the displacement time history curve. At the same time, it assists in real-time observation of the absence of divergence during the test to determine that the helicopter does not have ground resonance, which helps reduce the test risk and improve the test safety factor.

[0032] In one embodiment, the linear displacement sensor is a GXY-12-150A linear displacement sensor produced by Xi'an Xiling Sensing Technology Co., Ltd.

[0033] The strain gauge is used to obtain the main rotor shaft tension. It is installed on the main rotor shaft of the helicopter by gluing. After installation, it is calibrated to obtain the linear relationship formula between the strain gauge output resistance and the main rotor shaft tension. The linear relationship formula of the main rotor shaft tension can be obtained by inputting the formula into the data analysis module. It is used to calculate the conversion process of the rotor lift to the collective pitch position, and convert the rotor tension that is difficult to observe intuitively into the collective pitch position that is easy to observe intuitively.

[0034] The specific implementation method of the main rotor shaft tension and strain gauge load (relationship with rotor lift) calibration work is as follows:

[0035] ① Known: When the helicopter just leaves the ground, the rotor lift is equal to the helicopter weight;

[0036] ② Adjust the helicopter weight to the maximum takeoff weight allowed in the "Flight Manual" and record the rotor pull (equal to the helicopter weight) as W1;

[0037] ③Power on the helicopter and the test system, use a crane and sling to lift the helicopter until it just leaves the ground, and record the load value Z1 of the main rotor shaft tensile strain gauge at this time;

[0038] ④ Adjust the helicopter weight to the minimum rotor lift required in the test, and record the rotor pull (equal to the helicopter weight) as W2;

[0039] ⑤ Use a crane and sling to lift the helicopter until it just leaves the ground, and record the load value Z2 of the main rotor shaft tensile strain gauge at this time;

[0040] ⑥ Divide the value range from W1 to W2 into five equal parts to obtain three values: W3, W4, and W5;

[0041] ⑦ Adjust the helicopter weight to W3, W4, W5, use a crane and sling to lift the helicopter until it just leaves the ground, and record the load values ​​of the main rotor shaft tension strain gauge Z3, Z4, Z5 at this time;

[0042] ⑧ Take W1 and Z1, W2 and Z2, W3 and Z3, W4 and Z4, W5 and Z5 as coordinate points in the WZ plane coordinate system, draw linear asymptotes, and obtain the values ​​of coefficients a and b in the numerical relationship formula Z = a*W + b between the rotor thrust (equal to the helicopter weight) W and the main rotor shaft tension strain gauge load by interpolation method;

[0043] ⑨Power off the helicopter and test system.

[0044] The specific implementation method of the collective pitch position (relationship with the main rotor shaft tension strain gauge load) calibration work is as follows:

[0045] ① Known: The helicopter weight is the test weight W0 required for the ground resonance test, and the rotor lift state during the test requires 0%, 50%, and 80% of the helicopter weight;

[0046] ②Set: W01 = 0% * W0, W02 = 50% * W0, W03 = 80% * W0. From the formula ⑧ in (1), it can be calculated that the load values ​​of the main rotor shaft tension strain gauge corresponding to the corresponding rotor lift are Z01, Z02, and Z03;

[0047] ③Power on the helicopter and the test system, start the helicopter engine, and increase the collective distance. Observe the load value of the main rotor shaft tension strain gauge in real time through a portable tablet computer. When the value is Z01, Z02, and Z03, record the collective distance values ​​as XPC1, XPC2, and XPC3 respectively.

[0048] ④ During the ground resonance test, when the total distance value is XPC1, XPC2, and XPC3, the rotor lift is 0%, 50%, and 80% of the helicopter weight required by the test;

[0049] ⑤ Turn off the helicopter engine and power off the helicopter and test system.

[0050] In one embodiment, the strain gauge is a strain gauge (also known as a resistance strain gauge) produced by AVIC Electro-Measuring Instrument Co., Ltd., and is installed on the surface of the main rotor shaft of the helicopter by gluing according to the form of measuring force, temperature compensation requirements and other conditions.

[0051] The network switch is used to broadcast the test data transmitted from the data collector to the portable tablet computer through mesh. The network switch is installed on the test equipment mounting frame on the floor inside the helicopter cabin and fixed by bolt connection, close to the data collector.

[0052] In one embodiment, the network switch is a TP-LINK XDR1950 network switch produced by Shenzhen TP-LINK Technology Co., Ltd.

[0053] Portable tablet computer, used to receive and display test data broadcasted by network switch in mesh mode in real time, and provide it to ground test personnel outside the helicopter to observe test data in real time and make emergency measures according to the data to ensure test safety and reduce test risks. It is placed at the ground test personnel far away from the outside of the helicopter.

[0054] The external fuel cut-off device is used by external ground test personnel far away from the helicopter to cut off the engine fuel supply in an emergency to ensure the safety of personnel and the helicopter. It is placed at the ground test personnel far away from the outside of the helicopter. The external fuel cut-off device divides the front cables of the two engine fuel cut-off switches on the onboard pilot's operating panel into two. The parallel cables of each engine fuel cut-off switch are connected to a double-pole switch (circuit breaker) and can be operated at any time according to the instructions of the ground test personnel.

[0055] See also Figure 2 Taking a certain type of helicopter ground resonance test system and test method as an example, the specific implementation of the present invention is described. Four test conditions are determined: maximum take-off weight, rear center of gravity, cement road surface; maximum take-off weight, rear center of gravity, grass; minimum test weight, front center of gravity, cement road surface; minimum test weight, front center of gravity, grass.

[0056] The following work is performed under each test condition:

[0057] ① Complete the installation of test equipment, calibration of main rotor shaft tension strain gauge load, and calibration of collective pitch position;

[0058] ②Power on the helicopter and the test system, and start the helicopter engine;

[0059] ③ The helicopter pilot operates the collective pitch lever to adjust the collective pitch position to the calibrated XPC1, XPC2, and XPC3 respectively, and repeats the following work: The helicopter pilot operates the joystick to disturb the rotor along the direction of rotation at a frequency of 1.2Hz, 2.7Hz, and 2.8Hz, respectively, with a displacement radius not exceeding 9mm, and the number of disturbance circles is not less than 5 circles. During the disturbance process, the helicopter pilot feels whether the helicopter has a tendency to diverge from vibration, and the ground test personnel outside the helicopter observe in real time through a portable tablet computer whether the acceleration signal and displacement signal at each measurement position have a tendency to diverge from vibration. If either party finds that the vibration has a tendency to diverge, the joystick disturbance (helicopter pilot) should be stopped immediately, the engine fuel should be cut off (helicopter pilot or ground test personnel outside the helicopter), and the test should be terminated; if neither party finds a tendency to diverge from vibration, the collective pitch position should be adjusted to the next state to continue the test.

[0060] ④ After all the test contents under this working condition are completed, the helicopter engine is shut down, and the helicopter and the test system are powered off;

[0061] ⑤ Download the recovered data and analyze the data. If the acceleration data and displacement data at each measurement position do not show a divergent trend, it is determined that the helicopter does not experience ground resonance.

[0062] Descriptions of different advantageous arrangements have been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may be described as having different advantages over other advantageous examples. The selected example or examples are selected and described in order to best illustrate the principles of the examples, practical applications, and to enable those of ordinary skill in the art to understand the disclosure as having various examples with various modifications suitable for the particular use contemplated.

Claims

1. A helicopter ground resonance test system, characterized in that: The system includes a data collector, a GPS antenna, an overload acceleration sensor, a linear displacement sensor, a strain gauge, a network switch, a portable tablet computer and an external fuel cut-off device. The overload acceleration sensor is installed on the main pilot's footrest floor, the main reducer upper casing, the main reducer mounting platform, the cabin floor and the tail reducer position; The linear displacement sensor is installed at the damper of the skid landing gear of the helicopter or the buffer support position of the three-point landing gear; the strain gauge is installed on the main rotor shaft of the helicopter; the data collector collects and records the original machine signal of the extraction helicopter, the GPS antenna time signal, the overload acceleration sensor signal, the linear displacement sensor signal and the strain gauge signal, and sends them to the portable tablet computer through the network switch; the resonance situation is analyzed and judged by the portable tablet computer, and the external fuel cut-off device is controlled.

2. The helicopter ground resonance test system according to claim 1, characterized in that: By judging that there is no divergence trend in the time history curve of the overload acceleration data, it can be judged that the helicopter has no ground resonance phenomenon.

3. The helicopter ground resonance test system according to claim 1, characterized in that: The displacement time history curve combined with real-time observation of the damper or buffer strut during the test shows that there is no divergence, so as to determine that the helicopter has no ground resonance.

4. The helicopter ground resonance test system according to claim 1, characterized in that: The two ends of the linear displacement sensor are respectively installed on the two ends of the damper or buffer support.

5. The helicopter ground resonance test system according to claim 1, characterized in that: The data collector and the network switch are mounted on a test equipment mounting frame on the floor inside the helicopter cabin by bolts.

6. The helicopter ground resonance test system according to claim 1, characterized in that: The portable tablet computer is used to receive and display in real time the test data broadcasted by the network switch in mesh mode, and provides it to ground test personnel outside the helicopter to observe the test data in real time and take emergency measures according to the data situation to ensure the safety of the test and reduce the risk of the test.

7. The helicopter ground resonance test system according to claim 1, characterized in that: The original engine signals of the helicopter include a rotor speed signal, a collective pitch position signal and an engine torque signal.

8. A helicopter ground resonance test method, using a helicopter ground resonance test system as claimed in any one of claims 1 to 7, characterized in that: The method comprises the following steps: S1. Install test equipment, calibrate main rotor shaft tension and strain gauge load, and calibrate collective pitch position; S2, power on the helicopter and the test system, and start the helicopter engine; S3. Under working conditions, the helicopter pilot operates the collective pitch lever to adjust the collective pitch position to the calibrated position, and performs disturbances along the rotor rotation direction at a set frequency and a displacement with a radius not exceeding 9 mm. The helicopter pilot feels whether the helicopter has a tendency of vibration divergence, and the ground test personnel outside the helicopter observe the acceleration signal and displacement signal of each measuring position in real time through a portable tablet computer to see if there is a tendency of vibration divergence. If either party finds that the vibration has a tendency of divergence, the control stick disturbance should be stopped immediately, the engine fuel should be cut off, and the test should be terminated. If neither party finds a tendency of vibration divergence; S4. After completing all the test contents, the helicopter shuts down the engine, and the helicopter and the test system are powered off; S5. Download the recovered data.

9. The helicopter ground resonance test method according to claim 8, characterized in that: The data is analyzed offline. If the acceleration data and displacement data at each measurement position do not show a divergent trend, it is determined that the helicopter does not experience ground resonance.

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