Rotorcraft takeoff safety diagnostic and lift measurement device

Abstract

The present application belongs to the field of aviation ground test technology, and provides a rotorcraft take-off safety diagnosis and lift measurement device, which comprises a main take-off platform, a force balance, a vibration acceleration sensor, an information acquisition system and a computer loaded with a weight gravity center calculation program and a rotor dynamic balance program, wherein the main take-off platform is flush with the runway as a rigid take-off platform of the rotorcraft, a frame balance structure is fixedly connected below the main take-off platform and a force balance capable of measuring force in the circumferential direction is arranged below the main take-off platform, a vibration acceleration sensor is arranged on the lower surface of the main take-off platform, a strain gauge is arranged on each force bar of the force balance, the information acquisition system acquires data of the vibration acceleration sensor and the strain gauge and sends the data to the computer for calculation of the weight gravity center and rotor dynamic balance of the rotorcraft. The device can automatically measure the weight gravity center of the rotorcraft, and can accurately evaluate the weight gravity center and rotor dynamic balance level before take-off after the rotorcraft is normally started.

Description

Technical Field

[0001] This invention belongs to the field of aviation ground testing technology, and relates to a helicopter take-off platform, specifically a rotorcraft take-off safety diagnostic and lift measurement device. Background Technology

[0002] Many factors affect the safe flight of rotorcraft. Among them, the rotor's takeoff weight and the center of gravity being within the safe envelope are the primary factors ensuring flight safety. Generally, rotorcraft have a narrow range of longitudinal and lateral changes. For example, a certain light rotorcraft has an empty weight of about 1350 kg, and its normal commercial or operational flight weight is mainly around 2000 kg. As fuel is consumed during flight, a narrow and unreasonable center of gravity envelope can easily lead to situations where the center of gravity exceeds the safe range during daily use. Figure 1 Appendix Figure 2 The heading and lateral envelope of this model are currently calculated manually based solely on the pilot's recorded fuel level and empty weight. This method is prone to calculation errors, which can result in the aircraft exceeding the center of gravity range during takeoff. This can lead to flight conditions that do not meet the requirements of the flight manual's usage restrictions section, potentially causing dangerous situations such as engine failure at maximum speeds. Exceeding the center of gravity envelope may also result in an inability to safely autorotate and land.

[0003] Furthermore, rotor dynamic balance also has a significant impact on aircraft safety. The result of blade dynamic balance adjustment directly affects the vibration level of the helicopter, playing a decisive role in its performance, reliability, and comfort. Structural failure generally involves three stages: initiation, development, and qualitative change. The rotor dynamic balance magnitude is the most direct reflection of the structural condition. Significant differences in the repeatability of rotor dynamic balance magnitudes often indicate structural abnormalities. While repeatability checks may struggle to detect the initial damage, rotor dynamic balance analysis can provide sufficient early warning during the damage development stage. Currently, most aircraft lack rotor dynamic balance monitoring devices.

[0004] Currently, the lift measurement of large rotors relies entirely on dedicated rotor towers. The change of lift with collective pitch after the rotor is mounted on an aircraft is generally measured by tethered measurement, which carries certain risks. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a rotorcraft takeoff safety diagnostic and lift measurement device. This device serves as an automatic diagnostic platform for takeoff weight center of gravity and rotor dynamic balance, accurately assessing the weight center of gravity and rotor dynamic balance level before helicopter takeoff, thereby improving rotorcraft flight safety to a certain extent. Furthermore, this device can be equipped with a tethering device, facilitating the measurement of lift variations with collective pitch, and providing a basis for rotor performance evaluation in aircraft scientific research experiments.

[0006] The technical scheme of the present application:

[0007] A rotorcraft take-off safety diagnosis and lift measurement device, comprising a main take-off platform, a force balance, a vibration acceleration sensor, an information acquisition system and a computer loaded with a weight gravity center calculation program and a rotor dynamic balance program, wherein the main take-off platform is flush with the runway as a rigid take-off platform of the rotorcraft, a frame type balance structure is fixedly connected below the main take-off platform and a force balance capable of measuring force in a circumferential direction is arranged below the main take-off platform, a vibration acceleration sensor is arranged on the lower surface of the main take-off platform, a strain gauge is arranged on each force bar of the force balance, the information acquisition system acquires data of the vibration acceleration sensor and the strain gauge and sends the data to the computer for calculation of the weight gravity center of the rotorcraft and rotor dynamic balance.

[0008] Further, a tethering device is arranged on the main take-off platform and is used for tethering the rotorcraft, when the rotorcraft is tethered and taken off, the data of the strain gauge on the force balance is acquired by the information acquisition system to calculate the lift of the rotorcraft.

[0009] Further, the force balance comprises a balance element, a strain gauge and a measurement circuit, the strain gauge is a component strain type force sensor arranged on each force bar of the balance, and the strain gauge measures the components of the weight of the helicopter on each component strain type force sensor by using the lever balance principle.

[0010] Further, the vibration acceleration sensor acquires the amplitude and phase of the vibration speed and vibration acceleration of the main take-off platform and the information acquisition system acquires the data, after the computer receives the digital signal converted by the information acquisition system, the vibration parameters are calculated by the rotor dynamic balance program, and then the rotor dynamic balance of the rotorcraft is calculated.

[0011] Further, the information acquisition system converts the amplified voltage signal into digital quantity and sends the digital quantity to the computer; when the computer calculates the strain balance for static calibration, the balance calibration coefficient in the balance calibration formula is obtained by processing; when the computer calculates the strain balance for force measurement, the force and torque coefficients acting on the test model are obtained by processing.

[0012] Further, the weight gravity center calculation program calculates the weight gravity center of the rotorcraft according to the following formula:

[0013] F i =k i ξ i (1)

[0014] F i is the load calculated by the i-th component strain type force sensor, ξ i is the measured strain value, k i is a calibration coefficient.

[0015]

[0016] g is the acceleration of gravity, n is the number of component strain gauge load cells, M is the weight of the rotorcraft;

[0017]

[0018] x i is the lateral coordinate of the i th strain gauge point; Xc is the lateral coordinate of the center of gravity of the rotorcraft;

[0019]

[0020] y i is the longitudinal coordinate of the i th strain gauge point; Yc is the longitudinal coordinate of the center of gravity of the rotorcraft.

[0021] Further, the rotor dynamic balance program calculates the rotor dynamic balance of the rotorcraft according to the following formula:

[0022] a = FFT (x (t)) (5)

[0023] According to the rotor speed frequency, the rotor speed 1Ω vibration amplitude a corresponding to the rotor speed is extracted;

[0024] V = a / (2 * pi * f0) (6)

[0025] f0 is the rotor speed frequency; V is the vibration speed.

[0026] Further, when the unit of acceleration is g, the unit is converted to:

[0027] V IPs = 9800 * a / 25.4 (7)

[0028] converted to IPS, i.e. inches per second.

[0029] Advantages of the present application:

[0030] 1. The present application can be used for rotorcraft take-off safety diagnosis and test lift measurement.

[0031] 2. When the rotorcraft is pushed to the designated position above the device platform of the present application, the weight center of gravity of the aircraft is automatically measured; then after the pilot completes the take-off check, the platform is normally started, and the rotor dynamic balance is automatically measured by the sensors on the platform, and the weight center of gravity and the rotor dynamic balance level are accurately evaluated before the helicopter takes off, which to some extent improves the flight safety of the rotorcraft.

[0032] 3. In addition, by using the platform mooring device and the force balance, the rotorcraft rotor lift can be accurately measured with different total distances, which provides a basis for blade design improvement and rotorcraft body interference analysis. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A diagram for illustrating the longitudinal center of gravity limitation of a helicopter in the background art;

[0034] Figure 2 A diagram for illustrating the lateral center of gravity limitation of a helicopter in the background art;

[0035] Figure 3 A diagram for illustrating the overall system of the present application;

[0036] Figure 4 A diagram for illustrating the measuring balance of the present application;

[0037] Figure 5 A diagram for illustrating the data acquisition system of the present application;

[0038] Wherein, 1 is a runway, 2 is a main take-off platform, 3 is a vibration acceleration sensor, 4 is a strain gauge, 5 is an information acquisition system, 6 is a measuring balance, 7 is a tethering interface. DETAILED DESCRIPTION

[0039] 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 some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0040] The present application proposes a rotorcraft take-off safety diagnosis and lift measurement device, i.e. an automatic diagnosis platform, for diagnosing the main factors affecting the safe flight of a rotorcraft, including the take-off weight center of gravity and rotor dynamic balance, so as to accurately evaluate the weight center of gravity and rotor dynamic balance level before take-off of a helicopter, and to improve the flight safety of a rotorcraft to a certain extent. In addition, the device is equipped with a tethering device, which can facilitate the measurement of the change of lift with total pitch, and provide a basis for rotorcraft scientific research and test rotor efficiency evaluation.

[0041] The core algorithm involved in the present application includes a rotorcraft weight and center of gravity calculation algorithm using a force balance and a rotor dynamic balance algorithm using a vibration acceleration sensor.

[0042] 1. Rotorcraft weight and center of gravity calculation using a force balance:

[0043] F i = k i ξ i (1)

[0044] F i is the load calculated by the ith strain gauge, ξ i is the measured strain value, ki For calibration coefficient.

[0045]

[0046] g is the acceleration of gravity, generally 9.8.

[0047]

[0048] x i For i strain gauge point horizontal coordinate.

[0049]

[0050] y i For i strain gauge point longitudinal coordinate.

[0051] 2, the rotor dynamic balance size is obtained by using vibration acceleration sensor:

[0052] a=FFT(x(t)) (5)

[0053] According to the rotor speed frequency, the vibration amplitude corresponding to the rotor speed 1Ω (corresponding to the rotor speed, the number of revolutions per second) is extracted.

[0054] V=a / (2*π*f0) (6)

[0055] f0 is the rotor speed frequency, unit is hertz.

[0056] When the unit of acceleration is g, the unit needs to be converted.

[0057] V IPs =9800*a / 25.4 (7)

[0058] Convert to IPS (inches per second).

[0059] The core device of the technical scheme of the application is a main take-off platform and a force measuring balance, in addition to an acceleration sensor, a test collection, transmission and display system, a fixed connection device; a rotor aircraft weight gravity calculation program based on the force measuring balance device, a rotor dynamic balance program based on the acceleration sensor, a total of seven components.

[0060] The first core component of the application is a main take-off platform, mainly including ① a flat plate made of alloy or other high-strength materials, ② a platform longitudinal (X direction) zero mark line, ③ a platform transverse (Y direction) zero mark line, and ④ a platform equipped with a tethering device.

[0061] The second core component of the application is a force measuring balance, mainly including ① a balance element (elastic element), ② a strain gauge, and ③ a measurement circuit (measurement bridge). The weight of the helicopter is measured on each sensor by using the principle of lever balance.

[0062] The three-vibration acceleration sensor is composed of a single, multiple conventional vibration acceleration sensor or a velocity sensor.

[0063] The fourth composition is a test acquisition, transmission and display system, mainly comprising ① amplifier, ② filter, ③ data acquisition system, ④ transmission wire, ⑤ computer and the like.

[0064] The fifth composition is a fixed connection device, mainly comprising ① main take-off platform and force balance connecting piece, ② force balance and ground connecting piece, and ③ main take-off platform and ground connecting piece.

[0065] The sixth composition is a program for calculating the weight and gravity center of a rotor aircraft based on the force balance device, and the calculation formulas are shown in formulas (1), (2), (3) and (4).

[0066] The seventh composition is a program for calculating the rotor dynamic balance based on the acceleration sensor, and the calculation formulas are shown in formulas (5), (6) and (7).

[0067] The platform is a mobile or fixed take-off platform, which is installed below the normal take-off runway of the aircraft. When the rotor aircraft is pushed to the designated position above the platform, the weight and gravity center of the aircraft are automatically measured. Then, after the pilot completes the take-off inspection, the platform is normally started on the platform, and the rotor dynamic balance is automatically measured by the sensor on the platform. The platform is composed of the main take-off platform, the fixed connection device, the force balance device, the acceleration sensor, the test acquisition system and the software evaluation system, and the specific structure is shown in the following figure. Figure 3 .

[0068] 1. Take-off platform and fixed connection device

[0069] The platform includes a flat and high-strength take-off platform, the height of which is aligned with the ground. The sensor and the force balance device are below the ground runway, and should not affect the helicopter taxiing and taking off.

[0070] The platform has obvious helicopter parking marks, including horizontal and vertical machine alignment lines. The helicopter is parked according to the marks, and the weight center coordinates can be conveniently measured by the force balance, which provides a basis for evaluating whether the helicopter exceeds the weight and gravity center envelope.

[0071] The rotor dynamic balance of the helicopter includes rotor dynamic balance and tail rotor dynamic balance. Compared with the rotor dynamic balance, the tail rotor dynamic balance is relatively simple. Therefore, the rotor dynamic balance is mainly discussed in the following description. The weight imbalance of a rotating machine will produce 1 / rev vibration during the operation of the machine, and the vibration parameters can be represented by the amplitude and phase of the vibration speed or vibration acceleration.

[0072] The platform is equipped with a tethering device, which can conveniently realize tethering of the rotorcraft, and is combined with a force balance, which can realize accurate measurement of lift under different total distances.

[0073] 2. Force balance

[0074] The mechanical balance is a balance based on zero position measurement principle, and is a frame balance structure (see Figure 4 ). It is composed of component strain type force transducers, which measure the weight of the helicopter on each sensor by using lever balance principle. The mechanical balance is generally composed of a model support, a decomposition mechanism, a transmission mechanism and a measurement element. The free end of the balance is connected to the platform by a 1:5 taper, and the fixed end of the balance is connected to the fixed end of the platform by a plurality of (≥4) M12 screws, and is positioned by the end face of the balance.

[0075] The resistance strain gauge is the most commonly used sensitive element of high-precision sensors, which can convert the strain of the tested object into resistance change, and measure physical quantities such as force, pressure and acceleration. The strain gauge is composed of a sensitive grid, a substrate, a lead wire, an adhesive and a surface protector.

[0076] The circuit adopts a Wheatstone bridge, which has the advantages of high sensitivity, wide measurement range, simple circuit structure, high measurement accuracy and easy compensation. According to the number of strain gauges in the bridge arm, there are three kinds of strain measurement bridges: single-arm working bridge, double-arm working bridge (half bridge) and four-arm working bridge (full bridge). The strain balance measurement circuit generally adopts a full bridge circuit, which can increase the signal output under the same sensitivity coefficient K and bridge voltage U, and can also reduce the mutual interference between the components of the balance and the influence of temperature effect.

[0077] 3. Acceleration sensor and arrangement

[0078] The rotor is a key component of the helicopter vibration reduction, and the rotor cone trajectory and the result of the dynamic balance adjustment of the rotor blade directly affect the vibration level of the helicopter. It plays a decisive role in the performance, reliability and comfort of the helicopter. The structural failure process generally has three stages of initiation, development and phase change. The rotor dynamic balance level is the most intuitive reflection of whether the structure is in good working condition. The significant difference in the repeatability of the rotor dynamic balance level often means that the structure has an abnormal condition. Although it is difficult to find the initiation of damage through repeated inspection, the rotor dynamic balance analysis can provide sufficient early warning time in the development stage of the damage.

[0079] The vibration sensor is installed at a specific position of the fuselage to measure the force caused by the rotor unbalance. The vibration amplitude and phase sensed by the vibration sensor are influenced by the dynamic response of the rotor system, the fuselage structure and the transfer function of the measuring system. Meanwhile, the vibration sensor receives signals from the rotor, the tail rotor, the aerodynamic force and the engine vibration in flight. Therefore, in order to obtain the data of the rotor dynamic balance, the signal of the nominal dynamic balance should be extracted from the vibration signal with rich frequency components without distortion. There are many methods to process the measured vibration signal, including analog and digital filtering, and the method using FFT.

[0080] 4. Signal acquisition system

[0081] The task of the strain gauge signal acquisition and processing is to amplify the voltage signal output by the bridge, convert the analog signal into digital signal, and then process it. This process is completed by the computer-centered balance measurement subsystem. When the strain gauge is calibrated, the balance calibration coefficients in the calibration formula are obtained by processing. When the strain gauge is used for force test, the force and torque coefficients acting on the test model are obtained by processing. Generally, the strain gauge signal acquisition and processing system is composed of an amplifier, a filter, an analog-to-digital converter (A / D), a data recording and display device, a computer and the like.

[0082] The task of the vibration signal acquisition and processing is to amplify the voltage signal output by the bridge, convert the analog signal into digital signal, and then process it. This process is also completed by the computer-centered data processing subsystem. Generally, the vibration signal signal acquisition and processing system is composed of an amplifier, a filter, an analog-to-digital converter (A / D), a data recording and display device, a computer and the like.

[0083] The above is only a specific embodiment of the present application, which is described in detail. The part not described in detail is the conventional technology. However, the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. The protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A rotorcraft takeoff safety diagnostic and lift measurement apparatus, comprising: The main take-off platform (2), the force measuring balance (6), the vibration acceleration sensor (3), the information acquisition system (5) and the computer with the weight gravity center calculation program and the rotor dynamic balance program are included, wherein the main take-off platform (2) is flush with the runway (1) as the take-off rigid platform of the rotor aircraft, the force measuring balance (6) is fixedly connected to the frame balance structure below the main take-off platform (2) and can measure the force in the circumference, the vibration acceleration sensor (3) is arranged on the lower surface of the main take-off platform (2), the strain gauge (4) is arranged on each force measuring rod of the force measuring balance (6), the information acquisition system (5) acquires the data of the vibration acceleration sensor (3) and the strain gauge (4) and sends the data to the computer for the calculation of the weight gravity center and the rotor dynamic balance of the rotor aircraft; The vibration acceleration sensor (3) acquires the amplitude and phase of the vibration speed and vibration acceleration of the main take-off platform (2) and the information acquisition system (5) acquires the data, the computer receives the digital signal converted by the information acquisition system (5), obtains the vibration parameters through the rotor dynamic balance program and then calculates the rotor dynamic balance of the rotor aircraft; The weight gravity center calculation program calculates the weight gravity center of the rotor aircraft according to the following formula: （1） the load calculated for the first component strain gauge load cell, the measured strain value, the calibration factor; （2） g is the acceleration due to gravity, n is the number of component strain gauge load cells, and M is the weight of the rotorcraft. （3） For Xc is the lateral coordinate of the center of gravity of the rotorcraft. （4） For Yc is the longitudinal coordinate of the center of gravity of the rotorcraft.

2. The rotorcraft takeoff safety diagnostic and lift measurement apparatus of claim 1, wherein, The tethering device is arranged on the main take-off platform (2) and is used for tethering the rotor aircraft, when the rotor aircraft is tethered and taken off, the data of the strain gauge (4) on the force measuring balance (6) is acquired by the information acquisition system (5) to calculate the lift of the rotor aircraft.

3. The rotorcraft takeoff safety diagnostic and lift measurement apparatus of claim 1, wherein, The force measuring balance (6) includes the balance element, the strain gauge (4) and the measuring circuit, the strain gauge (4) is the component strain type force sensor arranged on each balance force measuring rod, the strain gauge (4) measures the components of the helicopter weight on each component strain type force sensor by the lever balance principle.

4. The rotorcraft takeoff safety diagnostic and lift measurement apparatus of claim 1, wherein, The information acquisition system (5) converts the voltage signal into digital signal after amplification and sends the digital signal to the computer; the computer obtains the balance calibration coefficient in the balance calibration formula through processing when calculating the strain balance for static calibration; the computer obtains the force and torque coefficient acting on the test model through processing when calculating the strain balance for force test.

5. The rotorcraft takeoff safety diagnostic and lift measurement apparatus of claim 1, wherein, The rotor dynamic balance program calculates the rotor dynamic balance of the rotor aircraft according to the following formula: (5) According to the rotor speed frequency, the vibration amplitude a corresponding to the rotor speed 1Ω is extracted; (6) where ω is the rotor rotational frequency; V is the vibration velocity.

6. The rotorcraft takeoff safety diagnostic and lift measurement apparatus of claim 5, wherein, When the unit of acceleration is g, the unit is converted to: (7) The unit is converted to IPS, that is, inch per second.

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