A method and device for adjusting excitation amplitude in a helicopter hub center dynamic characteristic test

Abstract

The present application belongs to the technical field of helicopter hub center dynamic characteristic test loading, and relates to a method and device for adjusting excitation amplitude in helicopter hub center dynamic characteristic test. The method can automatically adjust the amplitude command of the sweep voltage signal in real time according to the vibration amplitude of the helicopter buffer during the vibration sweep process, so as to ensure that the vibration excitation applied to the helicopter hub makes the helicopter have obvious vibration and the landing gear buffer always meets the requirement of the specified vibration amplitude value. The method solves the problem that the test is often stopped due to the out-of-limit vibration amplitude of the landing gear buffer during the test process, avoids the excessive vibration amplitude of the helicopter body, reduces the possibility of damage to the test machine, improves the automation degree of test loading control and the test efficiency, and shortens the test cycle.

Description

Technical Field

[0001] This invention belongs to the field of loading technology for dynamic characteristic testing of helicopter rotor hub center, and relates to a method and device for adjusting the excitation amplitude of dynamic characteristic testing of helicopter rotor hub center. Background Technology

[0002] The method for testing the dynamic characteristics of the helicopter rotor hub is as follows: The helicopter is placed stably, and within the required test frequency range, a test excitation system is used to apply steady-state sinusoidal frequency sweep excitation along the fuselage heading and lateral direction at the rotor hub center. This ensures sufficient amplitude for the landing gear damper, and the amplitude-frequency and phase-frequency curves at the rotor hub center under a constant force amplitude are measured. Within the required excitation frequency range, a coarse frequency sweep is first performed to determine several resonant frequency ranges. Then, a fine frequency sweep is performed near each resonant frequency. During the frequency sweep, the steady-state sinusoidal excitation amplitude is gradually increased until the applied excitation force causes a significant response from the accelerometer at the rotor hub center and noticeable vibration in the fuselage, facilitating vibration mode analysis. The vibration amplitude of the landing gear damper needs to be monitored in real time during the test. If the damper vibration amplitude exceeds the specified safety value, the test should be stopped immediately to avoid damage to the helicopter.

[0003] The test equipment consists of two parts: a test excitation system and a test measurement and control system. The test excitation system, which is the actuator, comprises an excitation actuator cylinder, an excitation rod, a fixed bracket, and a mounting platform. The excitation point is placed on the rotor blade dummy, and excitation is applied along the fuselage heading and lateral direction. The excitation force is transmitted to the center of the rotor hub through the rotor hub, causing the helicopter fuselage to vibrate. The test measurement and control system consists of a vibration modal testing system, a hydraulic servo loading control system, and displacement sensors, acceleration sensors, etc.

[0004] The commonly used frequency sweep excitation control process for helicopter rotor hub center dynamic characteristic testing is as follows: The following explanation uses a fine sweep at a single resonant frequency as an example. The vibration modal testing system sends a frequency sweep voltage signal, which is connected to the hydraulic servo loading control system to control the excitation actuator to apply a steady-state sinusoidal frequency sweep excitation to the helicopter. A displacement sensor is installed on the helicopter's buffer to measure the buffer's vibration amplitude. The output signal of this displacement sensor is connected to the vibration modal testing system and the hydraulic servo control system. The hydraulic servo control system has a safety protection value preset according to the specified value of the buffer's vibration amplitude. During the frequency sweep, the measured vibration amplitude of the buffer may exceed the preset safety protection value due to resonance of the helicopter body near the resonant frequency. At this time, the hydraulic servo control system will immediately stop the test. After the test stops, the test personnel manually reduce the amplitude of the frequency sweep voltage signal sent by the vibration modal testing system, thereby reducing the steady-state sinusoidal frequency sweep excitation applied to the test machine, and then restart the test. Since the sweep frequency voltage signal for the dynamic characteristics test of the helicopter rotor hub is usually set to an initial value by the test personnel based on the helicopter's condition, after the test exceeds the limit and stops, the test personnel adjust the amplitude of the sweep frequency voltage signal based on experience. If the vibration amplitude of the landing gear buffer is within the specified range and the response value of the acceleration sensor is large enough, then the amplitude of the sweep frequency voltage signal is appropriate. In order to achieve this goal, the amplitude of the sweep frequency voltage signal needs to be adjusted multiple times. During the process of adjusting the amplitude of the sweep frequency voltage signal multiple times, the vibration amplitude of the landing gear buffer will also exceed the limit multiple times.

[0005] The dynamic characteristics test of the helicopter rotor hub center usually includes multiple test states, each containing several resonant frequencies. Therefore, the vibration amplitude of the landing gear buffer will exceed the limit dozens of times during the test, which may cause damage to the helicopter. Manually adjusting the amplitude of the sweep frequency voltage signal leads to low test efficiency, long test cycle, and low degree of automation in test control. Summary of the Invention

[0006] The purpose of this invention is to propose a method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test. This method enables real-time automatic adjustment of the sweep frequency voltage signal amplitude command based on the vibration amplitude of the helicopter's landing gear buffer during the vibration sweep process. This ensures that the vibration excitation applied to the helicopter rotor hub produces significant vibration while the landing gear buffer always meets the specified vibration amplitude requirements. This solves the problem of test stoppage due to excessive landing gear buffer vibration amplitude during testing, avoids excessive helicopter body vibration amplitude, reduces the possibility of damage to the test aircraft, improves the automation level and efficiency of test loading control, and shortens the test cycle.

[0007] The technical solution of the present invention: In order to achieve the above objectives, according to the first aspect of the present invention, an automatic adjustment method for the excitation amplitude of the dynamic characteristics test of the helicopter rotor hub is proposed. During the test frequency sweeping process, the displacement measurement amplitude of the landing gear buffer is used as the adjustment reference, and the amplitude of the frequency sweeping voltage signal is automatically adjusted in real time, thereby ensuring that the vibration excitation applied to the helicopter rotor hub causes the helicopter to have obvious vibration, and the landing gear buffer always meets the vibration amplitude requirement.

[0008] Two situations may occur during the vibration sweep frequency process: one is that the helicopter body does not vibrate significantly and the response value of the acceleration sensor installed on the body is too small, which is not conducive to vibration mode analysis; the other is that the resonance generated by the helicopter body is too large, and the displacement measurement amplitude of the landing gear buffer exceeds its specified safety protection value, causing the test to stop. If the helicopter body vibration is severe, it may cause damage to the helicopter body.

[0009] The automatic adjustment method includes the following steps:

[0010] Step 1: Set the specified vibration amplitude value A for the landing gear buffer, and adjust the lower limit percentage A. min Adjust the upper limit percentage A max The amplitude adjustment coefficient K for the swept frequency voltage signal;

[0011] Step 2: Conduct dynamic characteristic tests;

[0012] Step 3: During the test, record the displacement measurement amplitude of the landing gear buffer as B; and the amplitude of the pre-adjustment sweep frequency voltage signal output by the signal source of the vibration modal testing system as C0.

[0013] Step 4: Based on the vibration of the helicopter fuselage, the amplitude of the sweep frequency voltage signal is adjusted using a hydraulic servo loading control system. The amplitude of the sweep frequency voltage signal is gradually adjusted to C1 using the sweep frequency voltage signal amplitude adjustment coefficient K, until A×A is achieved. min ≤B≤A×A max .

[0014] In one possible embodiment, in step 4, when the amplitude C0 of the pre-adjustment sweep voltage signal output by the signal source of the vibration modal testing system is too small, and the helicopter body does not exhibit significant vibration, the displacement measurement amplitude B of the landing gear buffer is less than its vibration amplitude specification value A multiplied by the adjustment lower limit percentage, which is A. min That is, B <A×A min ;

[0015] The hydraulic servo loading control system performs automatic adjustment. The amplitude C1 of the sweep frequency voltage signal after the first automatic adjustment is C0 multiplied by the sweep frequency voltage signal amplitude adjustment coefficient K, that is, C1=C0×(1+K).

[0016] If the test requirements are still not met after the first adjustment, the system will automatically perform a second adjustment. The amplitude of the swept frequency voltage signal after the second adjustment will be C1 = C1 + C0 × K. If the test requirements are still not met after the second adjustment, a third automatic adjustment will be performed, and so on, until B ≥ A × A. min .

[0017] In one possible embodiment, in step 4, when the amplitude C0 of the pre-adjustment sweep voltage signal output by the signal source of the vibration modal testing system is too large, the resonance generated by the helicopter body is too large. At this time, the displacement measurement amplitude B of the landing gear buffer is greater than its vibration amplitude specified value A multiplied by the adjustment upper limit percentage, which is A. max That is, B > A × A max ;

[0018] The hydraulic servo loading control system performs automatic adjustments. The amplitude C1 of the swept frequency voltage signal after the first automatic adjustment is C0 minus C0 multiplied by the sweep frequency voltage signal amplitude adjustment ratio K, i.e., C1 = C0 × (1 - K). If the test requirements are still not met after the first adjustment, the system automatically performs a second adjustment. The amplitude C1 of the swept frequency voltage signal after the second adjustment is C1 = C1 - C0 × K. If the test requirements are still not met after the second adjustment, a third automatic adjustment is performed, and so on, until B ≤ A × A. max .

[0019] In one possible implementation, adjust the lower limit percentage A. min The range of values ​​is 0. min ≤0.5.

[0020] In one possible implementation, adjust the upper limit percentage A. max The value range is 0.5. max ≤1.

[0021] In one possible embodiment, the sweep voltage signal amplitude adjustment coefficient K ranges from 0 to 1. <K≤0.3。

[0022] ​​According to a second aspect of the present invention, a helicopter rotor hub center dynamic characteristic testing device is provided to realize the above-mentioned automatic adjustment method for the excitation amplitude of a helicopter rotor hub center dynamic characteristic test. The device includes a vibration modal testing system, a hydraulic servo loading control system, a test excitation system, and a measurement unit. The vibration modal testing system is a measurement mechanism, mainly used for acquiring and receiving acceleration sensor signals at various measurement points of the test piece and receiving excitation displacement and excitation force signals at the loading points transmitted from the hydraulic servo loading control system. It also functions as a signal source, transmitting the voltage value of the swept frequency voltage signal to the hydraulic servo loading control system via a real-time communication line. Hydraulic servo loading control system; The hydraulic servo loading control system is a loading control mechanism, which mainly controls the test excitation system to receive the swept frequency voltage signal to excite the test piece, synchronously collect the excitation force, excitation displacement and monitor the landing gear buffer displacement signal, and transmit it to the vibration modal testing system in real time through the analog signal output port; The test excitation system is an actuator, which consists of an excitation actuator cylinder, an excitation rod, a fixed bracket and a mounting platform. The excitation point is placed on the blade dummy, and excitation is performed along the fuselage heading and side, respectively. The excitation force is transmitted to the center of the rotor hub through the rotor hub, causing the helicopter body to vibrate.

[0023] According to a third aspect of the invention, a storage medium is provided that stores a computer program, which, when executed by a computer, causes the computer to perform the method described above for automatically adjusting the excitation amplitude of a helicopter rotor hub center dynamic characteristic test.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention provides a method for automatically and in real-time adjusting the amplitude of the sweep frequency voltage signal in a helicopter rotor hub center dynamic characteristic test. The method uses the displacement measurement amplitude of the landing gear buffer as the adjustment benchmark, and the software of the hydraulic servo loading control system automatically adjusts the amplitude of the sweep frequency voltage signal in real time. This ensures that the vibration excitation applied to the helicopter rotor hub causes significant vibration in the helicopter, and that the landing gear buffer always meets the specified vibration amplitude requirement. It eliminates the need to wait for excessive helicopter vibration to cause the test to stop before manual adjustment, thus avoiding excessive helicopter vibration amplitude, reducing the possibility of damage to the test aircraft, improving the automation level and efficiency of the test loading control, and shortening the test cycle. Attached Figure Description

[0026] Figure 1 A schematic diagram of a test bench for the dynamic characteristics of a helicopter rotor hub;

[0027] Figure 2 Schematic diagram of a test device for the dynamic characteristics of a helicopter rotor hub;

[0028] Figure 3 This is a schematic diagram of a test without frequency sweep voltage signal adjustment.

[0029] Figure 4 A schematic diagram for the experiment of adjusting the frequency sweep voltage signal. Detailed Implementation

[0030] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0031] Example 1

[0032] During the frequency sweep test of the dynamic characteristics of the helicopter rotor hub, the amplitude of the sweep voltage signal is automatically adjusted in real time based on the displacement measurement amplitude of the landing gear buffer. This ensures that the vibration excitation applied to the helicopter rotor hub causes the helicopter to vibrate significantly, and that the landing gear buffer always meets the specified vibration amplitude requirements.

[0033] Example: A dynamic characteristic test of the rotor hub center of a certain type of helicopter was conducted, using a 0.1–10 Hz frequency sweep. A displacement sensor was installed on the landing gear buffer. The specified value for the landing gear buffer displacement vibration amplitude was 3 mm, and the pre-set safety protection value in the hydraulic loading control system was also 3 mm. The sweep voltage signal amplitude given by the vibration modal testing system signal source was 0.5 V, i.e., the original sweep voltage signal amplitude was 0.5 V. When the frequency sweep reached 3.8 Hz, the helicopter fuselage resonated, and the measured displacement amplitude of the landing gear buffer exceeded the pre-set safety protection value of 3 mm. The adjustment process is as follows:

[0034] ① Set four test parameters in the software: the vibration amplitude of the landing gear buffer is specified as 3mm, the lower limit percentage is adjusted to 20%, the upper limit percentage is adjusted to 80%, and the amplitude adjustment coefficient of the sweep frequency voltage signal is 0.1.

[0035] The upper limit of the software settings adjustment is 2.4mm (3×80%=2.4mm), and the lower limit of the software settings adjustment is 0.6mm (3×20%=0.6mm).

[0036] ② During the frequency sweep, when the frequency is below 1Hz, the displacement measurement amplitude of the landing gear buffer is approximately 1.5mm. When the frequency sweep reaches 3.5Hz, the displacement measurement amplitude of the buffer has reached 2.5mm, which is greater than the upper limit of 2.4mm set by the software. The control unit of the hydraulic servo loading control system begins the first automatic adjustment, reducing the amplitude of the frequency sweep voltage signal given by the vibration modal testing system signal source from 0.5V to 0.45V, i.e., 0.5 - 0.5 × 0.1 = 0.45V. This signal is sent to the excitation actuator to reduce its excitation amplitude, which is then transmitted from the center of the rotor hub to the landing gear buffer, reducing its displacement measurement amplitude to 2.45mm. ③ The landing gear buffer displacement measurement amplitude of 2.45mm is still greater than the adjustment upper limit of 2.4mm set by the software. The system automatically performs a second adjustment, reducing the amplitude of the sweep frequency voltage signal given by the vibration modal test system signal source from 0.45V to 0.4V (i.e., 0.45-0.5×0.1=0.4). The landing gear buffer displacement measurement amplitude is reduced to 2.38mm, which is less than the adjustment upper limit of 2.4mm. Since it does not meet the automatic adjustment requirements, the software stops automatically adjusting the excitation amplitude.

[0037] ④ As the test continued, the sweep frequency gradually approached the helicopter's resonant frequency band of 3.8 to 4.2 Hz. The control unit of the hydraulic servo loading control system would repeatedly and automatically adjust to keep the landing gear buffer displacement measurement amplitude within 2.4 mm. At this time, the sweep voltage signal amplitude had dropped to about 0.2 V.

[0038] ⑥ When the test sweep frequency is higher than 4.2Hz, and the helicopter fuselage no longer resonates, the displacement measurement amplitude of the landing gear impactor is about 0.4mm, which is less than the adjustment lower limit of 0.6mm set by the software. The control unit of the hydraulic servo loading control system begins to perform the first automatic adjustment, increasing the sweep voltage signal amplitude given by the vibration modal test system signal source from 0.2V to 0.25V (i.e., 0.2 + 0.5 × 0.1 = 0.25), and sending it to the excitation actuator to increase its excitation amplitude. This amplitude is then transmitted from the rotor hub center to the landing gear buffer, increasing its displacement measurement amplitude to 0.45mm.

[0039] ⑦ If the measured amplitude of the landing gear buffer displacement is 0.45mm, which is still less than the lower limit of adjustment set by the software (0.6mm), the system will perform a second automatic adjustment. The amplitude of the sweep frequency voltage signal given by the vibration modal testing system signal source will be increased from 0.25V to 0.3V (i.e., 0.25 + 0.5 × 0.1 = 0.3). The measured amplitude of the landing gear buffer displacement will be increased to 0.53mm. If this is still less than the lower limit of adjustment set by the software (0.6mm), the system will perform a third automatic adjustment. Automatic adjustment will stop when the measured amplitude of the landing gear buffer displacement is greater than 0.6mm.

[0040] Example 2

[0041] like Figures 1-2 As shown, a helicopter rotor hub center dynamic characteristic testing device comprises a vibration modal testing system, a hydraulic servo loading control system, a test excitation system, and several measurement units (accelerometers at each measurement point, excitation force, excitation displacement, and monitoring landing gear buffer displacement signals). Figure 2 Schematic diagram of the helicopter rotor hub center dynamic characteristic test device. The vibration modal testing system is a measurement mechanism, primarily acquiring and receiving acceleration sensor signals at various measurement points on the test piece, as well as excitation displacement and excitation force signals transmitted from the hydraulic servo loading control system. It also functions as a signal source, transmitting the sweep frequency voltage signal value to the hydraulic servo loading control system via a real-time communication line. The hydraulic servo loading control system is a loading control mechanism, primarily controlling the test excitation system to receive the sweep frequency voltage signal and excite the test piece, simultaneously acquiring excitation force, excitation displacement, and monitoring landing gear buffer displacement signals, and transmitting these signals to the vibration modal testing system in real-time through the analog signal output port. The test excitation system is an actuator, consisting of an excitation actuator cylinder, excitation rod, fixed bracket, and mounting platform. The excitation point is placed on the rotor blade dummy, and excitation is applied along the fuselage heading and lateral directions. The excitation force is transmitted to the rotor hub center through the rotor hub, causing vibration in the helicopter fuselage.

Claims

1. A method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test, characterized in that, This is based on a helicopter rotor hub center dynamic characteristic testing device. The device includes a vibration modal testing system, a hydraulic servo loading control system, a test excitation system, and measurement units set at each measurement point. The vibration modal testing system is a measurement mechanism that collects acceleration sensor signals at each measurement point of the test piece and receives excitation displacement and excitation force signals transmitted from the hydraulic servo loading control system. It also functions as a signal source, transmitting the voltage value of the sweep frequency voltage signal to the hydraulic servo loading control system via a real-time communication line. The hydraulic servo loading control system is a loading control mechanism that mainly controls the test excitation system to receive the sweep frequency voltage signal to excite the test piece, simultaneously collects the excitation force, excitation displacement, and monitors the landing gear buffer displacement signal, and transmits it to the vibration modal testing system in real time through an analog signal output port. The test excitation system is an actuator that consists of an excitation actuator cylinder, an excitation rod, a fixed bracket, and a mounting platform. It places the excitation point on the rotor blade dummy and excites it along the fuselage heading and side, respectively. The excitation force is transmitted to the rotor hub center through the rotor hub, causing the helicopter body to vibrate. The method includes the following steps: Step 1: Set the vibration amplitude value A of the landing gear buffer to a specified value, and adjust the lower limit percentage A. min Adjust the upper limit percentage A max Step 1: Adjust the sweep frequency voltage signal amplitude by factor K; Step 2: Conduct dynamic characteristic tests; Step 3: During the test, record the displacement measurement amplitude of the landing gear buffer as B; The amplitude of the sweep frequency voltage signal output from the vibration modal testing system before adjustment is C0; Step 4: Based on the vibration of the helicopter body, adjust the sweep frequency voltage signal amplitude using a hydraulic servo loading control system, and gradually adjust the sweep frequency voltage signal amplitude to C1 using the sweep frequency voltage signal amplitude adjustment factor K, until A×A is achieved. min ≤B ≤A×A max .

2. The method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test according to claim 1, characterized in that, In step 4, when the amplitude C0 of the pre-adjustment sweep voltage signal output by the signal source of the vibration modal testing system is too small, and the helicopter fuselage does not exhibit significant vibration, the displacement measurement amplitude B of the landing gear buffer is less than its specified vibration amplitude value A multiplied by the adjustment lower limit percentage, which is A. min That is, B <A×A min ; The hydraulic servo loading control system performs automatic adjustment. The amplitude C1 of the sweep frequency voltage signal after the first automatic adjustment is C0 multiplied by the sweep frequency voltage signal amplitude adjustment coefficient K, that is, C1=C0×(1+K). If the test requirements are still not met after the first adjustment, the system will automatically perform a second adjustment. The amplitude of the swept frequency voltage signal after the second adjustment will be C1 = C1 + C0 × K. If the test requirements are still not met after the second adjustment, a third automatic adjustment will be performed, and so on, until B ≥ A × A. min .

3. The method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test according to claim 1, characterized in that, In step 4, when the amplitude C0 of the pre-adjustment sweep voltage signal output by the signal source of the vibration modal testing system is too large, the resonance generated by the helicopter body is too large. At this time, the displacement measurement amplitude B of the landing gear buffer is greater than its vibration amplitude specified value A multiplied by the adjustment upper limit percentage, which is A. max That is, B > A × A max ; The hydraulic servo loading control system performs automatic adjustment. The amplitude C1 of the sweep frequency voltage signal after the first automatic adjustment is C0 minus C0 multiplied by the sweep frequency voltage signal amplitude adjustment ratio coefficient K, that is, C1=C0×(1-K). If the test requirements are still not met after the first adjustment, the system will automatically perform a second adjustment. The amplitude of the swept frequency voltage signal after the second adjustment will be C1 = C1 - C0 × K. If the test requirements are still not met after the second adjustment, a third automatic adjustment will be performed, and so on, until B ≤ A × A. max .

4. A method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test according to any one of claims 1-3, characterized in that, Adjust the lower limit percentage A min The range of values ​​is 0. min ≤0.5.​ 5. A method for adjusting the excitation amplitude in a helicopter rotor hub center dynamic characteristic test according to any one of claims 1-3, characterized in that, Adjust the upper limit percentage A max The value range is 0.

5. max ≤1.​ 6. A method for adjusting the excitation amplitude of a helicopter rotor hub center dynamic characteristic test according to any one of claims 1-3, characterized in that, The range of values ​​for the sweep frequency voltage signal amplitude adjustment coefficient K is 0. <K≤0.3。 7. The method for adjusting the excitation amplitude of a helicopter rotor hub center dynamic characteristic test according to claim 1, characterized in that, The measurement unit includes an acceleration sensor.

8. The method for adjusting the excitation amplitude of a helicopter rotor hub center dynamic characteristic test according to claim 1, characterized in that, The landing gear buffer is connected to a displacement sensor.

9. A storage medium, characterized in that, The computer program stores a computer program that, when executed by a computer, causes the computer to perform the method for adjusting the excitation amplitude of a helicopter rotor hub center dynamic characteristic test as described in any one of claims 1-8.

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