Manned helicopter torsional vibration test system and method based on collective distance rod automatic excitation

Abstract

The invention relates to a torsional vibration test system and method for a manned helicopter based on automatic excitation of a collective distance rod. Comprising a signal controller, a driver, a servo motor and a mounting bracket, the servo motor is fixed on the cabin floor of the manned helicopter through the mounting bracket, and the output end of the servo motor is connected with the total pitch rod; the signal controller is in communication connection with the driver, the frequency range, the frequency step length, the excitation duration and the interval duration of an excitation signal are set and managed through a man-machine interaction interface, and the signal is transmitted to the driver; the driver is in communication connection with the servo motor, receives the control signal, converts the control signal into a driving signal and transmits the driving signal to the servo motor; the servo motor receives a signal of the driver and operates, and meanwhile, rotation of an output shaft of the motor is converted into linear motion through the mechanical interface, so that excitation of the collective pitch rod is achieved.

Description

[0001] TECHNICAL FIELD The present application belongs to the field of helicopter dynamics, and particularly relates to a manned helicopter torsional vibration test system and method based on automatic excitation of a total pitch lever. BACKGROUND

[0002] The helicopter torsional vibration test is used for obtaining torsional vibration frequencies of a rotor\power\transmission coupling system and checking torsional vibration stability of the system, and is a key test for verifying helicopter dynamics design and ensuring safe operation of the helicopter.

[0003] The test process mainly includes: determining test measurement contents, determining test working conditions, exciting the torsional vibration system according to a prescribed method, and analyzing test data to determine torsional vibration frequencies or system stability characteristics. The traditional manned helicopter torsional vibration test mainly relies on manual excitation of a test pilot or excitation of engine power turbine speed through an engine FADEC control system. The former has the disadvantages of large excitation frequency and excitation amplitude errors and can only perform single frequency point excitation, resulting in insufficient test verification results and possible excessive vibration of the helicopter during the test. The latter needs to change the software of the engine FADEC control system and needs to check the safety of the software change through ground semi-physical simulation tests and engine bench tests, and has the disadvantages of complex test implementation, high risk, long cycle and the like. SUMMARY

[0004] The present application improves the traditional torsional vibration test excitation method of a manned helicopter, proposes a manned helicopter torsional vibration test system and method based on automatic excitation of a total pitch lever, can make up for the shortcomings of the above method, conveniently and accurately obtain torsional vibration frequencies of a helicopter torsional vibration system, and fully verify the stability of the torsional vibration system.

[0005] According to a first aspect of the present application, a manned helicopter torsional vibration test system based on automatic excitation of a total pitch lever is provided, which comprises: a signal controller, a driver, a servo motor and a mounting bracket. The servo motor is fixed to a cabin floor of a manned helicopter through the mounting bracket, and an output end of the servo motor is connected with the total pitch lever. The signal controller is in communication connection with the driver, sets and manages a frequency range, a frequency step, an excitation time length and an interval time length of an excitation signal through a man-machine interface, and transmits the signal to the driver. The driver is in communication connection with the servo motor, receives a control signal and converts the control signal into a driving signal for the servo motor. The servo motor receives the signal of the driver and operates, and simultaneously converts rotation of a motor output shaft into linear motion through a mechanical interface to realize excitation of the total pitch lever.

[0006] In a possible embodiment, the mounting bracket comprises a servo motor mounting table, a side support plate movable plate, a side support plate fixed plate, a bottom plate; the servo motor mounting table is connected with the side support plate movable plate through bolts; the side support plate movable plate and the fixed plate are provided with sliding grooves, and are fixed through bolts after the required height is adjusted; the side support plate fixed plate is connected with the bottom plate through bolts; the bottom plate is fixed to the floor of the helicopter cockpit through bolts; each part of the mounting bracket is provided with a sliding groove, which is used for adjusting the translational position in three orthogonal directions as required, so as to adapt to different types of helicopters.

[0007] In a possible embodiment, the servo motor output end is provided with an adapter rod, which is used for converting the angular motion of the motor rotating shaft into linear motion of the elastic rod; one end of the adapter rod is fixed with the motor rotating shaft, and the other end is hinged to the elastic rod; the other end of the elastic rod is hinged to the clamp.

[0008] In a possible embodiment, the excitation frequency range of the constant-pitch rod is 0.1 Hz-20 Hz, and the maximum excitation amplitude is 15 mm.

[0009] According to the second aspect of the present application, a manned helicopter torsional vibration test method based on automatic excitation of a constant-pitch rod is provided, which adopts the above-mentioned manned helicopter torsional vibration test system based on automatic excitation of a constant-pitch rod, and comprises the following steps: Step 1: Determine the test conditions. The typical combinations need to be selected for testing according to the working state of the helicopter and the torsional vibration characteristic influencing factors (including the constant pitch, the number of engines, the rotor speed), to ensure that these states can cover the normal use state of the helicopter, so that the torsional vibration characteristics can be fully verified; Step 2: Determine the measurement signals. The signals that need to be measured during the helicopter torsional vibration test need to be determined, which generally include but are not limited to the helicopter rotor shaft torque, the tail transmission shaft torque, the blade section oscillation load, the blade anti-oscillator load and displacement, the engine power turbine torque, etc. These signals are used to monitor the working condition of the helicopter during the helicopter torsional vibration test and the torsional vibration test effect, to facilitate the adjustment of the excitation signal and to ensure the safety of the test process; on the other hand, they are used to analyze the torsional vibration response characteristics of the helicopter, to obtain accurate torsional vibration frequency and stability characteristics; Step 3: Determine the excitation signal characteristics. It affects whether the accurate torsional vibration system natural frequency can be obtained. The torsional vibration system natural frequency is calculated according to the parameters of the helicopter rotor and tail rotor, the transmission system parameters and the engine parameters, and the sweep frequency range, the sweep frequency amplitude and the sweep frequency duration of the excitation signal are determined according to the calculation results; Step 4: The sweep frequency range, the sweep frequency amplitude and the sweep frequency duration of the excitation signal obtained in step 3 are set by using a signal controller, to ensure that the characteristics of the output excitation signal meet the requirements; Step 5: Conduct a torsional vibration excitation test. The pilot starts the engine, and the helicopter is in the running state. When the helicopter reaches the operating condition required in Step 1, an excitation signal is sent to the automatic excitation device through the software interface to achieve automatic excitation; at the same time, the measurement signals required in Step 2 are recorded, and the test effect and helicopter operating status are judged based on the signals. Step 6: Perform frequency domain analysis and damping identification on the measured signal to determine the natural frequency and modal damping of the torsional vibration system, and analyze the torsional vibration stability characteristics.

[0010] In one possible embodiment, the specific process of calculating the excitation frequency in step 3 includes: Step 3.1: Establish the equations of motion for the oscillation of the propeller blade structure:

[0011] In the formula: [ M P ] is the blade modal mass matrix; [ C P ] is the modal damping matrix; [ K P ] is the modal stiffness matrix; z p This represents the blade oscillation displacement.

[0012] Step 3.2: Establish the torsional vibration equation of the transmission system substructure as follows:

[0013] In the formula: [ I q [ is the modal mass matrix of the transmission system;] C q ] is the modal damping matrix; [ K q ] is the modal stiffness matrix; θ q This refers to the torsional displacement of the transmission system.

[0014] Step 3.3: Obtain the coupled torsional vibration equations of the above subsystem using the modal synthesis method:

[0015]

[0016] In the formula: [ C qp [ ] is the damping coupling matrix between the rotor and the transmission system; I r ] is the modal mass matrix of the propeller blade.

[0017] Step 3.4: Solve the eigenvalues ​​of the equations listed in Step 3.3 to obtain the torsional vibration frequency of the coupled system, where the first-order modal frequency is the excitation frequency of the torsional vibration test.

[0018] In one possible embodiment, the specific process of analyzing torsional vibration stability in step 6 includes: Step 6.1: After excitation is completed, select two peak points in the free decay stage of the rotor shaft torque time-domain curve, and denote them as follows: A (t1) A (t n ); Step 6.2: According to the formula: Calculate the damping ratio, where n is the number of cycles between the two peak points.

[0019] In one possible embodiment, the safety of the torsional vibration test is ensured by installing an engine emergency shut-off switch on the manned helicopter. The control button of the emergency shut-off switch is operated by an off-board test personnel. When the helicopter experiences vibration during the test, the test personnel will switch the control button to the "off" position. The signal emitted by the control button is transmitted via cable to the engine start / stop control box in the cockpit, enabling independent control of the engine to stop.

[0020] The advantages of this invention are: Traditional torsional vibration testing of manned helicopters mainly relies on manual excitation by the test pilot or excitation of the engine's turbine speed through the engine's FADEC control system. The former suffers from large errors in excitation frequency and amplitude, and can only perform single-frequency point excitation; the latter requires modifications to the engine's FADEC control system software, and the safety of these modifications needs to be verified through ground-based semi-physical simulation tests and engine bench tests. This makes the test complex, high-risk, and time-consuming. The helicopter torsional vibration testing method based on automated collective pitch rod excitation proposed in this invention significantly improves excitation accuracy and does not require connection to other control systems, avoiding the technical risks associated with system cross-linking, reducing pre-test risk checks, and shortening the test cycle. This method is applicable to all types of manned helicopters. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a manned helicopter torsional vibration testing system based on collective pitch bar automated excitation, according to a preferred embodiment of the present invention. Figure 2 This is a schematic diagram of the connection structure between the servo motor and the collective pitch rod according to a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the mounting bracket structure according to a preferred embodiment of the present invention; Figure 4This is a flowchart of a manned helicopter torsional vibration test method based on automated collective pitch rod excitation, according to a preferred embodiment of the present invention. Figure 5 This is a comparison diagram showing the effects of the method using the preferred embodiment of the present invention and the conventional method. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0024] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] First, an experimental system and method for automatically stimulating the collective pitch bar are described. The main components and interconnections of the system are detailed below. Figure 1 ,include: The signal controller, through a human-machine interface, sets and manages the frequency range, frequency step size, excitation duration, and interval duration of the excitation signal, and transmits the signal to the driver. The driver receives control signals and converts them into drive signals for the servo motor; The installation of the mounting bracket is as follows: Figure 2 As shown, it is bolted to the pilot's floor, and the servo motor is fixed to it to provide sufficient support for the servo motor; to accommodate different helicopter models, the mounting bracket is adjustable in translational displacement in three orthogonal directions; The connection between the servo motor and the collective pitch rod is as follows:Figure 3 As shown, it is mounted on the upper mounting platform of the mounting bracket, receives the signal from the driver and operates, and at the same time converts the rotation of the motor output shaft into linear motion through the mechanical interface, and connects to the helicopter collective pitch rod through the elastic rod to achieve excitation of the collective pitch rod from 0.1Hz to 20Hz, with a maximum excitation amplitude of 15mm.

[0026] Torsional vibration tests were conducted on manned helicopters using an automated collective pitch bar excitation method. The test procedure is as follows: Figure 4 The steps are as follows: [1] Determine the test conditions. Typical combinations need to be selected for testing based on the helicopter's operating status and the factors affecting torsional vibration characteristics (including collective pitch, number of engines, and rotor speed) to ensure that these conditions cover the normal operating conditions of the helicopter and that the torsional vibration characteristics are fully verified. [2] Determine the measurement signals. It is necessary to determine the signals that need to be measured during the helicopter torsional vibration test. These signals generally include, but are not limited to, the helicopter rotor shaft torque, tail drive shaft torque, blade profile yaw load, blade damper load and displacement, and engine power turbine torque. These signals are used to monitor the helicopter's operation and the torsional vibration test effect during the test, so as to adjust the excitation signal and ensure the safety of the test process. They are also used to analyze the helicopter's torsional vibration response characteristics and obtain accurate torsional vibration frequency and stability characteristics. [3] Determine the characteristics of the excitation signal. This affects whether the accurate natural frequency of the torsional vibration system can be obtained. Calculate the natural frequency of the torsional vibration system based on the parameters of the helicopter rotor and tail rotor, transmission system, and engine. Determine the sweep frequency range, sweep amplitude, and sweep duration of the excitation signal based on the calculation results.

[0027] [4] Installation of excitation equipment and setting of excitation signal. The automatic collective pitch excitation device is installed in the helicopter cockpit, and the excitation signal determined in step 3 is set through the human-machine interface to ensure that the characteristics of the output excitation signal meet the requirements; [5] Install an emergency shut-off switch. This switch will allow for the timely shutdown of the engine should excessive vibrations occur during testing that could affect the safety of the helicopter and pilot. [6] Conduct torsional vibration excitation test. The pilot starts the engine and the helicopter is in the driving state. When the helicopter reaches the working condition required in step 1, the excitation signal is sent to the automatic excitation device through the software interface to realize automatic excitation; at the same time, the measurement signal required in step 2 is recorded, and the test effect and helicopter working state are judged according to the signal. [7] Analyze torsional vibration characteristics. Perform frequency domain analysis and damping identification on the measured signals to determine the natural frequency and modal damping of the torsional vibration system, and analyze the torsional vibration stability characteristics.

[0028] Example [1] Determine the test conditions. Based on the helicopter's operating conditions and the influencing factors of torsional vibration characteristics, typical combined test conditions were selected: Table 1 Test Status

[0029] [2] Determine the measurement signal. The measurement signal is determined based on the monitoring and data analysis requirements: Table 2 Measurement Parameters

[0030] [3] Determine the characteristics of the excitation signal. Determine the sweep frequency range, sweep amplitude, and sweep duration of the excitation signal based on the calculated natural frequency of the torsional vibration system.

[0031] Table 3 Test Status Table

[0032] [4] Installation of excitation equipment and setting of excitation signal. The automatic collective pitch excitation device is installed in the helicopter cockpit, and the excitation signal determined in step 3 is set through the human-machine interface to ensure that the characteristics of the output excitation signal meet the requirements; [5] Install an emergency shut-off switch to cut off the engine's fuel supply in an emergency; [6] Conduct torsional vibration excitation test. The pilot starts the engine and the helicopter is in the driving state. When the helicopter reaches the working condition required in step 1, the excitation signal is sent to the automatic excitation device through the human-machine interface to realize automatic excitation. At the same time, the test personnel monitor and judge the measurement signal to determine the test effect and the working state of the helicopter. [7] Analyze torsional vibration characteristics. Perform frequency domain analysis and damping identification on the measured signals to determine the natural frequency and modal damping of the torsional vibration system, and analyze the torsional vibration stability characteristics. The results are shown in […]. Figure 5 .

Claims

1. A manned helicopter torsional vibration test system based on total length bar automated excitation, characterized in that, Comprise: Signal controller, driver, servo motor, mounting bracket; the servo motor is fixed on the cabin floor of manned helicopter through the mounting bracket, the output end of the servo motor is connected with the total pitch rod; the signal controller is in communication connection with the driver, the frequency range, the frequency step, the excitation time, the interval time of the excitation signal are set and managed through the man-machine interface, and the signal is transmitted to the driver; the driver is in communication connection with the servo motor, the driver receives the control signal and converts it into the driving signal for the servo motor; the servo motor receives the signal of the driver and operates, and simultaneously converts the rotation of the motor output shaft into linear motion through the mechanical interface, so as to realize the excitation of the total pitch rod.

2. The automatic excitation based on total length bar manned helicopter torsion vibration test system according to claim 1, characterized in that, The mounting bracket comprises a servo motor mounting table, a side support plate movable plate, a side support plate fixed plate and a bottom plate; the servo motor mounting table is connected with the side support plate movable plate through bolts; the side support plate movable plate and the fixed plate are provided with sliding grooves, and are fixed through bolts after the required height is adjusted; the side support plate fixed plate is connected with the bottom plate through bolts; the bottom plate is fixed on the cabin floor of the helicopter through bolts; the structures of the mounting bracket are all provided with sliding grooves, which are used for adjusting the translational position in three orthogonal directions as required, so as to adapt to different types of helicopters.

3. The automatic excited by total length bar manned helicopter torsion vibration test system according to claim 1, characterized in that, The output end of the servo motor is provided with an adapter rod, which is used for converting the angular motion of the motor rotating shaft into linear motion of the elastic rod; one end of the adapter rod is fixed with the motor rotating shaft, and the other end is hinged to the elastic rod; the other end of the elastic rod is hinged to the clamp, and the clamp is clamped on the head of the total pitch rod.

4. The automatic excited by total length bar manned helicopter torsion vibration test system according to claim 1, characterized in that, The excitation frequency range of the total pitch rod is 0.1 Hz-20 Hz, and the maximum excitation amplitude is 15 mm.

5. A method for torsional vibration test of manned helicopter based on total- length-rod automated excitation, characterized in that, The manned helicopter torsional vibration test system based on total pitch rod automatic excitation comprises the following steps: Step 1: determining the test working condition; Step 2: determining the signals needed to be measured during the helicopter torsional vibration test; Step 3: calculating the inherent frequency of the torsional vibration system according to the parameters of the helicopter rotor and tail rotor, the parameters of the transmission system and the parameters of the engine, and determining the sweep frequency range, sweep amplitude and sweep time of the excitation signal according to the calculation result; Step 4: setting the sweep frequency range, sweep amplitude and sweep time of the excitation signal obtained in step 3 by using the signal controller, so as to ensure that the characteristics of the output excitation signal meet the requirements; Step 5: sending the excitation signal to perform the torsional vibration excitation test under the test working condition determined in step 1; Step 6: performing frequency domain analysis and damping identification on the measured signals, determining the inherent frequency and modal damping of the torsional vibration system, and analyzing the torsional vibration stability characteristics.

6. The method of claim 5, wherein the method is a human-in-the-loop test method for torsional vibration of a helicopter based on total length bar automated excitation. In step 3, the specific process of calculating the excitation frequency comprises: Step 3.1: establishing the flapping motion equation of the blade substructure: where: M P is the blade modal mass matrix; C P is the modal damping matrix; K P is the modal stiffness matrix; Step 3.2: establishing the torsional vibration equation of the transmission system substructure: p is the blade whirl displacement. Step 3.3: obtaining the coupled torsional vibration equation of the above-mentioned subsystems by modal synthesis method: where: I q is the modal mass matrix of the driveline system; C q is the modal damping matrix; K q is the modal stiffness matrix; Step 3.4: solving the characteristic value of the equation listed in step 3.3 to obtain the torsional vibration frequency of the coupled system, wherein the first order modal frequency is the excitation frequency of the torsional vibration test. q is the torsional displacement of the driveline system. In step 6, the specific process of analyzing the torsional vibration stability comprises: where: C qp is the damping coupling matrix of the rotor and drive train; I r is the modal mass matrix of the blades. ​ 7. The method of claim 5, wherein the method is a human-in-the-loop test method for torsional vibration of a helicopter based on total length bar automated excitation. ​ Step 6.1: After the excitation is completed, select two peak points on the rotor shaft torque time domain curve in a free decay stage, respectively denoted as A (t1), A (t n ) ; Step 6.2: Calculate the damping ratio, n, as the number of interval periods between two peak points. Calculate the damping ratio, n, as the number of interval periods between two peak points.

8. The method of claim 5, wherein the method is a human-in-the-loop test method for torsional vibration of a helicopter based on total length bar automated excitation. The safety of torsional vibration test is ensured by installing engine emergency cut-off switch on manned helicopter.

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