A tilt-rotor helicopter rotor state sensing system and measuring method

Abstract

The present application belongs to the field of rotor state monitoring of tilt-rotor helicopter, and particularly relates to a rotor state sensing system and a measuring method for tilt-rotor helicopter. The system comprises six linear displacement sensors, an azimuth angle sensor, a current collector ring and a processor, wherein the six linear displacement sensors are arranged to form a six-degree-of-freedom parallel platform, the lower end surface of each linear displacement sensor is connected to the upper end surface of an elastic universal joint, and the upper end surface of each linear displacement sensor is fixed to the upper end surface of a rotor shaft; the azimuth angle sensor is installed on the current collector ring, the current collector ring is installed on a hub, and the azimuth angle sensor measures the azimuth angle of a hub arm; the output ends of the six linear displacement sensors and the azimuth angle sensor are connected to the processor; and a power supply system on the helicopter transmits direct current to the processor through the current collector ring after direct current distribution.

Description

Technical Field

[0001] This invention belongs to the field of tiltrotor helicopter rotor status monitoring, specifically relating to a tiltrotor helicopter rotor status sensing system and measurement method. Background Technology

[0002] Tiltrotor aircraft perfectly combine the advantages of helicopters and fixed-wing aircraft, boasting high speed, long range, large payload capacity, and low vibration. In helicopter mode, the tiltrotor rotor provides lift to overcome gravity and achieve maneuvering; in fixed-wing mode, it provides thrust to overcome aerodynamic drag and achieve high-speed flight. To ensure good performance in all modes, more stringent requirements are placed on the tiltrotor rotor. Because flexible universal joints can effectively solve rotor speed and load fluctuation problems and improve the overall aeroelastic stability of the aircraft, they have great application potential in tiltrotor aircraft.

[0003] Tiltrotors with a flexible universal joint configuration primarily achieve rotor pitch control through the deformation of flexible bearings. During this pitch control process, the rotor hub plane deflects relative to the rotor shaft. When the hub deflection angle is too large, it not only generates significant dynamic loads on the rotor's flexible universal joint but also risks blade collisions with the fuselage, potentially leading to premature failure of the flexible universal joint or blade impacts, thus affecting flight safety. Currently, there is no monitoring system for the rotor hub status of this type of helicopter. To ensure flight safety, it is necessary to obtain effective measured data on the hub deflection angle. Summary of the Invention

[0004] Purpose of the invention: To provide a tiltrotor helicopter rotor state sensing system and measurement method for measuring the rotor state of a tiltrotor helicopter with an elastic universal joint hub.

[0005] Technical solution:

[0006] A tiltrotor helicopter rotor state sensing system includes: six linear displacement sensors, an azimuth angle sensor, a collector ring, and a processor.

[0007] Six linear displacement sensors are assembled to form a six-degree-of-freedom parallel platform. The lower end face of each of the six linear displacement sensors is connected to the upper end face of the elastic universal joint, and the upper end face of each of the six linear displacement sensors is fixed to the upper end face of the rotor shaft.

[0008] An azimuth sensor is mounted on a collector ring, which is mounted on the propeller hub. The azimuth sensor measures the azimuth angle of the propeller hub support arm.

[0009] The outputs of six linear displacement sensors and an azimuth angle sensor are connected to the processor.

[0010] The onboard power system transmits DC power to the processor via a current collector after DC power distribution; the sensors are powered by the processor after power conversion; the azimuth sensor is directly powered by the onboard power system.

[0011] The linear displacement signal, azimuth signal, and clock signal from the sensor and the flight control system are processed by the processor; the processed rotor plane tilt angle and the azimuth angle of the rotor plane normal vector are transmitted to the flight control system via the bus, thereby realizing real-time monitoring of the rotor status.

[0012] A method for measuring the rotor state of a tiltrotor helicopter, the method being executed using the aforementioned tiltrotor helicopter rotor state sensing system, the method comprising:

[0013] Step 1: Determine the relationship between the six-degree-of-freedom platform formed by the linear displacement sensor and the state of the propeller hub;

[0014]

[0015] R θ The tilt angle of the propeller disk plane. Let be the azimuth angle of the normal vector of the propeller disk plane, that is, the angle between the projection of the normal vector onto the oxy plane and the x-axis. Let be the azimuth angle of the propeller disk plane normal vector in the propeller hub rotating coordinate system o1x1y1z1. Rx is the azimuth angle of the x1 axis at time T in the rotating coordinate system o1x1y1z1 of the propeller hub, which is the angle of rotation of the rotating coordinate system about the z axis. Rx is the rotation about the x1 axis and Ry is the rotation about the y1 axis.

[0016] Step 2: The clock signals of the airborne power supply and flight control system are transmitted to the processor through the collector loop to complete the self-test and data synchronization check of the processor and sensors;

[0017] Step 3: During flight, acquire linear displacement sensor signals and azimuth angle signals, and transmit them to the processor;

[0018] Step 4: The processor performs A / D conversion and filtering on the acquired linear displacement sensor signal, and stores the filtered data to obtain valid time-domain data;

[0019] Step 5: Based on the relationship between the six-degree-of-freedom platform and the rotor hub state determined in Step 1, obtain the rotor disk plane tilt angle and the azimuth angle of the rotor disk plane normal vector through relevant data processing algorithms;

[0020] Step 6: Transmit the rotor plane tilt angle and rotor plane normal vector calculated by the processor to the flight control system to complete rotor status monitoring;

[0021] Step 7: Determine whether the rotor disk tilt angle exceeds the relevant angle limit in the flight control system. If the rotor disk tilt angle exceeds the relevant angle limit, adjust the flight attitude. After the adjustment is completed, repeat steps 2 to 6. If the rotor disk tilt angle is within the relevant limit range, continue to maintain flight without adjusting attitude.

[0022] Furthermore, step three also includes:

[0023] Before collecting data, the linear displacement sensor and azimuth sensor need to be calibrated.

[0024] Further, step five specifically involves: determining the three translational and three rotational quantities of the propeller disk plane based on the extension and retraction of the six linear displacement sensors, thereby determining the tilt angle of the propeller disk plane. Based on the tilt angle of the propeller disk plane and the azimuth sensor data, the azimuth angle of the normal vector of the propeller disk plane can be obtained.

[0025]

[0026] A tiltrotor helicopter rotor state sensing system includes: three angular displacement sensors, an azimuth sensor, a collector ring, and a processor.

[0027] Three angular displacement sensors are installed between the elastic link and the central component to measure the rotation angle of the elastic link relative to the central component. The elastic link is connected to the central component of the rotor hub by means of a connector, and the intermediate gear of the central component is fixed on the rotor shaft.

[0028] An azimuth sensor is mounted on a collector ring, which is mounted on the propeller hub. The azimuth sensor measures the azimuth angle of the propeller hub support arm.

[0029] The outputs of the three angular displacement sensors and the azimuth sensor are connected to the processor.

[0030] The onboard power system transmits DC power to the processor via a current collector after DC power distribution; the sensors are powered by the processor after power conversion; the azimuth sensor is directly powered by the onboard power system.

[0031] The angular displacement signal, azimuth signal and clock signal from the sensor and the flight control system are processed by the processor; the processed rotor plane tilt angle and the azimuth angle of the rotor plane normal vector are transmitted to the flight control system through the bus, thereby realizing real-time monitoring of the rotor status.

[0032] A method for measuring the rotor state of a tiltrotor helicopter, the method being executed using the aforementioned tiltrotor helicopter rotor state sensing system, the method comprising:

[0033] Step 1: Determine the relationship between the angular displacement sensor and the rotor hub state;

[0034] Step 2: The clock signals of the airborne power supply and flight control system are transmitted to the processor through the collector loop to complete the self-test and data synchronization check of the processor and sensors;

[0035] Step 3: During flight, collect angular displacement sensor signals and azimuth angle signals, and transmit them to the processor;

[0036] Before collecting data, the angular displacement sensor and azimuth sensor need to be calibrated.

[0037] Step 4: The processor performs A / D conversion and filtering on the acquired angular displacement sensor signal, and stores the filtered data to obtain valid time-domain data;

[0038] Step 5: Based on the relationship between the six-degree-of-freedom platform or the angular displacement sensor and the rotor hub state determined in Step 1, obtain the rotor hub attitude angle information and the azimuth angle of the rotor disk plane normal vector through relevant data processing algorithms.

[0039] Step 6: Transmit the rotor hub attitude angle and the azimuth angle of the rotor disk plane normal vector calculated by the processor to the flight control system to complete rotor status monitoring;

[0040] Step 7: In the flight control system, determine whether the rotor disk tilt angle exceeds the relevant angle limit. When the rotor disk tilt angle exceeds the relevant angle limit, adjust the flight attitude. After the adjustment is completed, repeat steps 2 to 6 to adjust and then monitor the rotor hub status. When the rotor disk tilt angle is within the relevant limit range, continue to maintain flight without adjusting the attitude.

[0041] Furthermore, in step one, the relationship between the angular displacement sensor and the rotor hub state is as follows:

[0042] The torsion angle amplitude of the elastic connecting rod is equal to the deflection angle amplitude of the elastic universal joint hub, and the phase difference is constant.

[0043] Further, step five specifically involves:

[0044] The three sets of filtered RVDT data were subjected to spectrum analysis to obtain the amplitude and phase corresponding to 1Ω of each angular displacement sensor. Then, the amplitude data corresponding to the three sets of angular displacement sensors were compared to eliminate abnormal data. Finally, the mean value of the normal data was calculated to obtain the propeller hub attitude angle value.

[0045] The azimuth angle of the propeller disk plane normal vector is determined based on the phase corresponding to 1Ω.

[0046] Further, step five specifically involves:

[0047] Select the maximum time-domain amplitude of the three sets of filtered RVDT data and the corresponding time T; use the maximum amplitude as the propeller plane tilt angle.

[0048] Read the azimuth signal corresponding to time T, and use the azimuth signal corresponding to time T as the azimuth of the propeller disk plane normal vector.

[0049] Beneficial effects:

[0050] 1) This method uses two types of sensors to measure the rotor status, which can realize real-time monitoring of the rotor status. Moreover, the measurement signal is accurate and effective, and effectively avoids the influence of factors such as light, weather and electromagnetic interference during flight.

[0051] 2) This method can preprocess the signals collected by the sensors, ensuring the accuracy of signal processing, and transmit signals to the flight control system via the bus. The clock signal ensures that the flight control system and the attitude angle have good synchronization.

[0052] 3) The method uses sensors, processors, and current collector rings, all of which are integrated to ensure minimal impact on the structure;

[0053] 4) This method derives the correlation between the angular displacement sensor signal and the propeller hub attitude signal;

[0054] 5) Angular displacement sensors are easy to connect, occupy little space, are lightweight, have fast dynamic response, fast output rate, low cost, and have little impact on the entire rotor system;

[0055] 6) The angular displacement sensor method has a high level of technological maturity. This method indirectly measures the rotor attitude angle, avoiding the errors caused by introducing too many connecting devices in direct measurement.

[0056] 7) The linear displacement sensor method has a high level of technological maturity. This method can directly measure through relevant connecting tooling, monitor the rotor status in real time, and measure the attitude angle of the rotor hub in various states.

[0057] 8) The processor can not only perform data processing, but also add storage devices to store raw data, which facilitates subsequent data inspection and reprocessing;

[0058] 9) The current collector ring can effectively realize data transmission and azimuth signal transmission;

[0059] This method not only enables real-time monitoring of rotor status to ensure flight safety, but also verifies the isotropic properties of the elastic universal joint through relevant signal data. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of a tiltrotor helicopter rotor state sensing system according to the present invention;

[0061] Figure 2 A simplified geometric diagram of the propeller hub structure;

[0062] Figure 3 This is a simplified geometric diagram at time T0;

[0063] Figure 4 Curve showing the change in torsion angle of the elastic connecting rod bearing over time;

[0064] Figure 5 Schematic diagram of coordinate system establishment and hinge point location distribution;

[0065] Figure 6 This is a schematic diagram of a six-degree-of-freedom platform.

[0066] Figure 7 This is a schematic diagram of the propeller disk's state. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0068] In the description of this invention, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0069] This paper proposes a method for measuring the rotor hub attitude using angular displacement sensors (RVDT) / linear displacement sensors (LVDT) for monitoring the rotor hub status of this type of helicopter.

[0070] This method uses the propeller hub attitude to measure the propeller disk plane tilt angle R. θ (The angle between the normal vector of the rotor disk tilt plane and the rotor shaft) and the rotor disk azimuth angle where the normal vector of the rotor disk tilt plane is located. Two parameters are used to describe the rotor hub attitude (these two parameters can be converted into the rake and yaw angles required by the flight control system through relevant formulas), which facilitates the description of the rotor hub attitude, such as... Figure 7 As shown.

[0071] This method utilizes both angular and linear displacement sensors to simultaneously measure the rotor hub attitude angle. When using an LVDT (Low-Freedom Transmission Detector), a six-DOF parallel platform is constructed using linear displacement sensors. The lower end face of the linear displacement sensor is connected to the upper end face of the elastic universal joint, while the upper end face of the linear displacement sensor remains fixed to the upper end face of the rotor shaft. By varying the lengths of the six LVDTs and combining this with the azimuth signal, the rotor hub state is obtained. When using an RVDT (Rapid Reduction Transmission Detector), the angular displacement sensor is installed between the elastic link and the center component. Through theoretical derivation and simulation analysis, the relationship between the rotation angle of the elastic link and the tilt angle of the rotor hub plane is determined, thereby indirectly measuring the rotor hub attitude angle. To ensure aircraft attitude safety, the measured rotor hub state signal must be transmitted to the flight control system in a timely manner via a bus for attitude adjustments. Furthermore, to ensure synchronization between the rotor hub measurement state and the flight control system adjustments, a clock signal must be transmitted. This method utilizes linear displacement sensors / angular displacement sensors for higher reliability and more accurate measurement signals. It can effectively avoid the influence of light, weather, etc. during flight. At the same time, this measurement method has the advantages of high accuracy, fast dynamic response, low cost, and strong resistance to dynamic loads.

[0072] This invention proposes a rotor state sensing system for tiltrotor helicopters with a flexible universal joint hub configuration, such as... Figure 1 A linear displacement sensor / angular displacement sensor, a processor, a collector ring, and an azimuth sensor are added to the flexible universal joint rotor hub structure to measure the corresponding signals, thereby obtaining the attitude angle of the tiltrotor helicopter rotor hub.

[0073] The rotor status awareness system mainly includes signal acquisition, signal processing, and signal transmission. Signal acquisition mainly includes linear displacement data / angle data and azimuth angle signal of the fly loop. Signal processing mainly processes the linear displacement / angle signal, azimuth angle signal and clock signal from the sensor and the flight control system through the processor. Signal transmission is to transmit the processed rotor plane tilt angle and rotor plane normal vector azimuth angle to the flight control system through the bus, thereby realizing real-time monitoring of rotor status.

[0074] Power supply information for each component: The onboard power system transmits DC power to the processor via a current collector after DC distribution; the sensors are powered by the processor after power conversion; the azimuth sensor is directly powered by the onboard power system; the overall sensing system scheme is as follows: Figure 1 As shown.

[0075] The proposed rotor state perception system includes signal acquisition, signal processing and signal transmission modules (integrating sensors, processors and flow rings into rotor state perception);

[0076] The rotor state can be described by the tilt angle of the rotor plane and the azimuth angle of the rotor plane normal vector. The corresponding forward tilt angle of the corresponding air intake system can be obtained theoretically. and side chamfer

[0077] A six-DOF parallel platform is constructed using six linear displacement sensors and twelve cross hinges. This platform measures the rotor hub attitude angles via contact, providing a more comprehensive view of the rotor hub state. The proposed method involves assembling six linear displacement sensors into a six-DOF parallel platform. Figure 6 Installed between the upper end face of the flexible universal joint rotor hub and the upper end face of the rotor shaft, it has the advantages of high precision, fast dynamic response speed, and effective measurement of rotor status, effectively preventing the rotor from continuing to maintain effective data measurement under external load.

[0078] The rotor hub attitude angle is indirectly measured by using an angular displacement sensor, and the rotation angle of the elastic connecting rod bearing is also measured by the angular displacement sensor. The installation is convenient, and the angular displacement sensor is equipped with an eccentricity compensation device, which can effectively remove the influence caused by other offsets.

[0079] The relationship between the torsion angle of the elastic link and the attitude angle of the rotor hub was established (the tilt angle of the rotor plane and the azimuth angle of the rotor plane normal vector are related).

[0080] The symmetrical arrangement of the three sets of angular displacement sensors not only enables data mutual verification but also effectively improves the attitude angle output frequency. In addition, the symmetrical arrangement has little impact on the rotor dynamic balance.

[0081] To avoid a large deviation between the angular displacement sensor measurement and the rotor attitude angle due to factors such as aerodynamic drag, certain requirements are placed on the stiffness of the elastic connecting rod bearing in all directions. In addition, a corresponding compensation device is added to the angular displacement sensor to avoid the influence of other directional angles on the measurement.

[0082] This linear displacement sensor measuring device can verify the constant velocity performance of the elastic universal joint angle;

[0083] The angular distribution of the linear displacement sensor and the radius of the connecting nodes on the upper and lower end faces affect the measurement angle range and spatial dimensions; (an unreasonable angular distribution and cross angle distribution of the linear displacement sensor can cause jamming within the deflection angle range; the radius of the connecting nodes on the upper and lower end faces will have a certain impact on the measurement stroke and accuracy of the linear displacement sensor)

[0084] The tilt angle of the propeller disk plane is measured by a linear displacement sensor / angular displacement sensor, and the azimuth angle of the propeller disk plane normal vector can be obtained by combining the azimuth angle signal.

[0085] The rotor hub attitude angle is calculated based on the relevant processor and fed back to the flight control system;

[0086] Methods for measuring the rotor condition of tiltrotor helicopters include:

[0087] Step 1: Determine the relationship between the six-degree-of-freedom platform composed of linear displacement sensors or the state of the propeller hub using angular displacement sensors;

[0088] An angular displacement sensor is installed between the elastic link and the center member to measure the torsion angle of the elastic link. By using the physical connection relationship, it can be deduced that the amplitude of the torsion angle of the elastic link is equal to the amplitude of the deflection angle of the elastic universal joint hub, and the phase difference is constant.

[0089] A six-degree-of-freedom parallel platform composed of linear displacement sensors measures the angle between the upper end face of the elastic universal joint and the fixed plane of the rotor shaft. The planar deflection attitude of the platform is solved by the changes in the extension and retraction of the six linear displacement sensors.

[0090] The relationship between the six-degree-of-freedom platform constructed from linear displacement sensors and the state of the propeller hub is as follows:

[0091]

[0092] R θ The tilt angle of the propeller disk plane. Let be the azimuth angle of the normal vector of the propeller disk plane, that is, the angle between the projection of the normal vector onto the fixed coordinate system oxy plane and the x-axis. Let be the azimuth angle of the propeller disk plane normal vector in the propeller hub rotating coordinate system. Rx is the azimuth angle corresponding to the x-axis at time T in the rotating coordinate system of the propeller hub, that is, the angle of rotation of the rotating coordinate system about the z-axis. Rx is the rotation about the x1-axis, and Ry is the rotation about the y1-axis.

[0093] An azimuth sensor is mounted on a collector ring, which is mounted on the propeller hub. The azimuth sensor measures the azimuth angle of the propeller hub support arm.

[0094] Step 2: The clock signals of the airborne power supply and flight control system are transmitted to the processor through the collector loop to complete the self-test and data synchronization check of the processor and sensors;

[0095] The clock signal of the flight control system is transmitted to the processor through the fly loop, thereby performing the processor's self-test to ensure the effectiveness of the device and to achieve synchronization between the flight control system and the processor. In addition, the airborne power signal is transmitted to the processor to power the processor and sensors.

[0096] Step 3: During flight, acquire linear displacement sensor signals or angular displacement sensor signals and azimuth angle signals, and transmit them to the processor;

[0097] Before collecting data, the angular displacement sensor, displacement sensor and azimuth sensor need to be calibrated.

[0098] Step 4: The processor performs A / D conversion and filtering on the acquired linear displacement sensor signal or angular displacement sensor signal, and stores the filtered data to obtain valid time domain data;

[0099] Filtering: First, when the sampling rate of the angular displacement sensor is large, the amount of data obtained is large. Therefore, it can be averaged, smoothed, and other data processing can be performed, and then the data can be resampled to facilitate the selection of the maximum and minimum values ​​in the future.

[0100] Step 5: Based on the relationship between the six-degree-of-freedom platform or the angular displacement sensor and the rotor hub state determined in Step 1, obtain the disk plane tilt angle and the azimuth angle of the rotor disk plane normal vector through relevant data processing algorithms; where the disk plane tilt angle is the angle between the rotor hub plane normal vector and the rotor shaft axis, and the azimuth angle of the rotor disk plane normal vector is the angle between the rotor disk plane normal vector and the fuselage heading.

[0101] When determining the disk plane tilt angle based on RVDT data, two methods can be used.

[0102] Processing Method 1: Perform spectrum analysis on the three sets of filtered RVDT data to obtain the amplitude and phase corresponding to 1Ω of each angular displacement sensor. Then compare the amplitude data corresponding to the three sets of angular displacement sensors, eliminate abnormal data, and then calculate the mean value of the normal data to obtain the disk plane tilt angle value.

[0103] The azimuth angle of the propeller disk plane normal vector is determined based on the phase corresponding to 1Ω;

[0104] Processing Method 2: Select the maximum amplitude in the time domain of the three sets of filtered RVDT data and the corresponding time T; use the maximum amplitude as the disk plane tilt angle.

[0105] Read the azimuth signal at time T and use it as the azimuth angle of the propeller disk plane normal vector.

[0106] In step 5, the LVDT forms a six-degree-of-freedom parallel platform. Data collected at each moment can be used to analyze the rotor hub state. To ensure data validity, multiple time points can be selected for analysis, and then the data can be used to solve for the rotor state (disk plane tilt angle and azimuth angle of the disk plane normal vector). The rotor state is calculated repeatedly using the following formula. When the rotor state is determined, the disk plane tilt angle is obtained by averaging the values ​​at time T1 and T2. To ensure calculation accuracy, multiple time points can be selected for solving. The desired rotor hub state is obtained by averaging multiple sets of data, and the corresponding azimuth angle is also deduced using the time and azimuth angle signals.

[0107] Step 6: Transmit the rotor plane tilt angle and rotor plane normal vector calculated by the processor to the flight control system to complete rotor status monitoring;

[0108] Step 7: In the flight control system, determine whether the rotor disk tilt angle exceeds the relevant angle limit. If the rotor disk tilt angle exceeds the relevant angle limit, adjust the flight attitude. After the adjustment, repeat steps 2 to 6 to make adjustments and then monitor the rotor hub status. If the rotor disk tilt angle is within the relevant limit range, continue to maintain flight without adjusting the attitude.

[0109] Each outrigger is equipped with an angular displacement sensor, which not only improves data acquisition and data validity but also provides signal output rate.

[0110] The method described can be applied to the measurement of the isokinetic performance of elastic universal joints.

[0111] In step one,

[0112] (1) Derivation of the relationship between the angular displacement sensor and the tilt angle of the rotor disk plane:

[0113] An angular displacement sensor is used to measure the torsion angle of an elastic connecting rod bearing (at the connection position of the central component). It mainly consists of an angular displacement sensor, an eccentricity compensation device, and corresponding mounting and connecting parts.

[0114] 1.1 Parameter Definition

[0115] Fixed coordinate system oxyz: Fixed coordinate system, with the origin o at the center of the ball where the elastic universal joint is located, the x-axis parallel to the incoming flow direction, the y-axis perpendicular to the x-axis, and the z-axis along the rotor axis;

[0116] θ: The angle between the rotor hub plane axis and the x-axis;

[0117] β: Inclination angle of the propeller disk plane;

[0118] Ro: The transformation matrix between the propeller disk deflection coordinates and the fixed coordinate system;

[0119] R2: The radius of the circle containing the elastic bearing;

[0120] N i : Bearing coordinates at the connection point of the central component of the propeller hub (bearing No. 1 is the bearing near the propeller hub support arm 1).

[0121] N i ': Coordinates of the bearing at the connection point of the propeller hub after the change;

[0122] M i : Bearing coordinates at the connection point of the central component;

[0123] Bearing torsion angle at the center connection;

[0124] The direction of the torsion angle of the elastic bearing: when viewed from the outside of the center component towards the center of the propeller hub, clockwise is positive and counterclockwise is negative. That is, when the elastic connecting rod bearing is raised relative to the propeller disk plane, it is positive, and when the elastic connecting rod bearing is lowered relative to the propeller disk plane, it is negative.

[0125] 1.2 Geometric Relationships

[0126] A flexible universal joint moves around the center of a spherical elastic bearing, enabling the transmission of centrifugal force and waving motion. A simplified model of the flexible universal joint is given below, where the center of the universal joint is the origin of the coordinate system, and the initial center of the elastic bearing is in the xoy plane, as shown below. Figure 2 .

[0127] 1.3 Derivation of Angular Relationships

[0128] 1.3.1 Derivation of Amplitude Relationship

[0129] The motion of the central component of the propeller hub around the center of the sphere o is equivalent to the rotation of bearings N1, N2, and N3 around a straight line passing through the center of the sphere o in the xoy plane. The transformation matrix between the propeller disk's deflected coordinates and the fixed coordinate system is as follows:

[0130]

[0131] In a fixed coordinate system, the bearing coordinates N1, N2, and N3 at the connection point of the central component of the propeller hub are:

[0132]

[0133] After the rotor hub plane deflects, the bearing coordinates change as follows:

[0134] [N′1 N′2 N′3]=Ro[N1 N2 N3]

[0135] In a fixed coordinate system, the bearing coordinates M1, M2, and M3 at the connection point of the central component are:

[0136]

[0137] After the hub plane deflects, the bearing coordinates change as follows:

[0138] [N′1 N′2 N′3]=Ro[N1 N2 N3]

[0139] In a fixed coordinate system, the bearing coordinates M1, M2, and M3 at the connection point of the central component are:

[0140]

[0141] Torsion angle of the bearing at the center connection It can be considered as a vector The angle between the line and plane of the xoy plane, therefore:

[0142]

[0143] Taking bearing No. 1 as an example, by substituting the relevant coordinate data, we can obtain:

[0144]

[0145] Considering that the actual propeller disk tilt angle is relatively small, we can approximate it with sinβ≈0 and cosβ≈1, and then simplify it to obtain:

[0146]

[0147] From the above formula, we can see that:

[0148] Right now

[0149] When θ = 0, cosθ = 1, therefore:

[0150] Right now

[0151] Therefore, the propeller disk tilt angle β and the elastic bearing torsion angle The amplitudes are equal.

[0152] 1.3.2 Derivation of Phase Relationship

[0153] Down Figure 3 A simplified geometric diagram at time T0 is given.

[0154] Direction definition: Looking down from the outside of the center component towards the center of the propeller hub, clockwise is positive and counterclockwise is negative. That is, the elastic connecting rod bearing rising relative to the propeller disk plane is positive, and the elastic connecting rod bearing falling relative to the propeller disk plane is negative.

[0155] The motion of an elastic universal joint in a rotating coordinate system is primarily a sinusoidal curve at a first-order rotational frequency. The torsional angle variation curve of an elastic connecting rod bearing follows the same pattern as that of the elastic universal joint. Figure 4 The curve of the torsion angle of the elastic connecting rod bearing as a function of time is given.

[0156] When the rotor is stable, the disk tilt angle relative to the fixed coordinate system is constant. In the fixed coordinate system, the rotor attitude can be described by the disk plane tilt angle and the azimuth angle of the disk plane normal vector. Assume the disk attitude angle is:

[0157] β = 10°

[0158]

[0159] Note: For ease of description, the unit for plane tilt angle is (°) and the unit for azimuth angle is (rad).

[0160] At time t=0, the azimuth angle of bearing M1 is -π / 3, and the plane tilt angle is 10°.

[0161]

[0162] At time t=0, the azimuth angle of bearing M2 is π / 3, and the deflection angle amplitude is -5°.

[0163]

[0164] At time t=0, the M3 bearing has an azimuth angle of π and a deflection angle of -5°.

[0165]

[0166] Depend on Figure 4 It can be seen that the M1 bearing reaches its maximum positive rotation at an azimuth angle of -π / 3, and the structural angle between the M1 bearing and the propeller hub support arm is π / 3. The difference between the azimuth angle corresponding to the maximum tilt angle of the propeller disk plane and the azimuth angle corresponding to the maximum positive torsion angle of the elastic connecting rod bearing M1 is the structural angle between the elastic connecting rod bearing M1 and the propeller hub support arm. Therefore, the difference between the azimuth angle corresponding to the maximum torsion angle of the elastic connecting rod bearing and the azimuth angle corresponding to the maximum tilt angle of the propeller disk plane is constant.

[0167] The difference in azimuth angle only changes when the included angle of the structure changes.

[0168] (2) Linear displacement sensor:

[0169] 2.1 Parameter Definition

[0170] Coordinate system oxyz: Fixed coordinate system, with the origin o at the center of the ball where the elastic universal joint is located, the x-axis parallel to the incoming flow direction, the y-axis perpendicular to the x-axis, and the z-axis along the rotor axis;

[0171] Coordinate system o1x1y1z1: Rotating coordinate system, with the origin o1 being the center of the upper surface of the fairing, and the plane o1x1y1z1 being parallel to the upper surface of the fairing. The coordinate system o1x1y1z1 rotates only around the z-axis (rotor axis) relative to the coordinate system oxyz.

[0172] Coordinate system o'x'y'z': a moving coordinate system, with the origin o' at the center of the upper end face of the spherical elastic bearing, and the plane o'x'y' parallel to the upper end face of the spherical elastic bearing. The moving coordinate system moves with the movement of the spherical elastic bearing.

[0173] A j The coordinates of the hinge point on the linear displacement sensor in the rotating coordinate system;

[0174] B j The coordinates of the lower hinge point of the linear displacement sensor in the rotating coordinate system;

[0175] h a The height of the hinge point on the linear displacement sensor from the plane of the rotating coordinate system o1x1y1z1;

[0176] h b The height of the lower hinge point of the linear displacement sensor from the plane of the moving coordinate system o'x'y'z'.

[0177] R a The radius of the circle where the hinge points are distributed on the linear displacement sensor;

[0178] R b The radius of the circle where the lower hinge points of the linear displacement sensor are distributed;

[0179] α: Half of the angle between the hinge points of two adjacent linear displacement sensors (o1A) j1 With o1A j2 Half of the included angle);

[0180] β: Half of the angle between the lower hinge points of two adjacent linear displacement sensors (o'B) j1 With o'B j2 Half of the included angle);

[0181] Q = (Rx, Ry, Rz, Dx, Dy, Dz): The pose of the moving coordinate system relative to the rotating coordinate system, where Rx is the rotation about the x1 axis, Ry is the rotation about the y1 axis, Rz is the rotation about the z1 axis, Dx is the translation along the x1 axis, Dy is the translation along the y1 axis, and Dz is the translation along the z1 axis.

[0182] θ x Transformation matrix for rotation about the x1 axis (rotation of the moving coordinate system relative to the rotating coordinate system about the x1 axis);

[0183] θy Transformation matrix for rotation about the y1 axis (rotation of the moving coordinate system relative to the rotating coordinate system about the y1 axis);

[0184] θ z Transformation matrix for rotation about the z1 axis (rotation of the moving coordinate system relative to the rotating coordinate system about the z1 axis);

[0185] R: Transformation matrix from moving coordinate data to the rotating coordinate system;

[0186] l j0 Initial length of each moving rod (linear displacement sensor);

[0187] Δl j The extension and retraction of each moving rod (linear displacement sensor);

[0188] 2.2 Model Simplification

[0189] To clearly describe the motion of the six-DOF platform in three-dimensional space, three reference coordinate systems are selected: a fixed coordinate system oxyz, a rotating coordinate system o1x1y1z1, and a moving coordinate system o'x'y'z', with 12 hinge points, as shown below. Figure 5 As shown.

[0190] 2.3 Relationship Derivation

[0191] Depend on Figure 5 From the geometric relationships, we can obtain the coordinates of the upper hinge point in the rotating coordinate system:

[0192]

[0193] In Equation 1), the elements in the first to third rows of the j-th column represent the coordinates of the upper hinge point Aj in the rotating coordinate system.

[0194]

[0195] In Equation 2), the elements in the first to third rows of the j-th column represent the coordinates of the lower hinge point Bj in the moving coordinate system.

[0196]

[0197] Transformation matrix from moving coordinate system to rotating coordinate system:

[0198]

[0199] According to equations 2) and 4), we can obtain:

[0200] P = [p] ij ] 4×6 =R·B 5)

[0201] In equation 5), P is the coordinate matrix of the lower hinge point in the rotating coordinate system, pij The coordinates of the lower hinge point are obtained by transforming the coordinates of the lower hinge point from the moving coordinate system to the rotating coordinate system.

[0202] When the extension and retraction of the six moving rods are known, the pose Q of the motion platform can be solved, i.e., in Δl j Given the given conditions, solve for Q. Therefore, the pose forward problem of a six-DOF parallel platform can be considered as a problem with a known parameter Δl. j Solve the data problem of position parameter Q, the equation is as follows:

[0203]

[0204] Solving system of equations 6) will yield the pose Q:

[0205]

[0206] First, we perform a Taylor series expansion on the nonlinear equation system 7) around Q0, and take its linear part to transform the nonlinear equation system into a linear equation system, i.e.:

[0207]

[0208] Let ΔQ = Q - Q0, where Δq j =q j -q j0 (j=1,2,…,6) then we get:

[0209]

[0210] Treating equation 9) as a system of linear equations with Q as the unknown, its coefficient matrix J is:

[0211]

[0212] If J is the Jacobian matrix, then equation 9) can be simplified to:

[0213]

[0214] The specific steps to solve this linear equation are as follows:

[0215] a) Input the structural parameters of the platform and the extension and retraction of each moving rod, and select the platform's attitude at the midpoint as the initial value for iteration;

[0216] b) Determine f based on the extension / retraction of each moving rod calculated using the given initial values. j (Q0), and obtain the Jacobian matrix J;

[0217] c) Use equation 11) above to solve for the correct position;

[0218] d) Given a precision, determine the maximum value of Δq.i If )≤σ, output the result if the given accuracy requirement is met; otherwise, use the formula Δq. i =q i -q i0 Correct the pose and repeat steps 2) to 6) until the required solution accuracy is met.

[0219] The numerical method described above for solving nonlinear equations can be called the Newton-Taylor expansion method. Since the motion platform typically operates near its midpoint, the initial value of the forward solution is set to the attitude of the platform when it is in the midpoint, ensuring convergence and accelerating the convergence speed. Unlike other numerical methods, the formulas in this algorithm have analytical forms at each step of the solution process. The key to using this method is obtaining the coefficient matrix J; the solution for the Jacobian matrix J is given below.

[0220] Taking the partial derivative of equation 7) above, we get:

[0221]

[0222] From equation 5), we can see that

[0223]

[0224] The above solution yields the change in rotation angle between the moving coordinate system and the rotating coordinate system. Therefore, a coordinate transformation is required to convert the rotation angle in the rotating coordinate system to the fixed coordinate system.

[0225] Since the hub plane tilt angle is within a small range, the formula for calculating the disk plane tilt angle is as follows:

[0226]

[0227] R θ The tilt angle of the propeller disk plane. Let be the azimuth angle of the normal vector of the propeller disk plane, that is, the angle between the projection of the normal vector onto the oxy plane and the x-axis. Let be the azimuth angle of the propeller disk plane normal vector in the propeller hub rotating coordinate system. The azimuth angle corresponding to the x-axis of the rotor hub rotating coordinate system at time T (i.e., the angle of rotation of the rotating coordinate system about the z-axis).

Claims

1. A tiltrotor helicopter rotor state sensing system, characterized in that, include: Six linear displacement sensors, azimuth sensors, current collector rings, and processors, among which... Six linear displacement sensors are assembled to form a six-degree-of-freedom parallel platform. The lower end face of each of the six linear displacement sensors is connected to the upper end face of the elastic universal joint, and the upper end face of each of the six linear displacement sensors is fixed to the upper end face of the rotor shaft. An azimuth sensor is mounted on a collector ring, which is mounted on the propeller hub. The azimuth sensor measures the azimuth angle of the propeller hub support arm. The outputs of six linear displacement sensors and an azimuth angle sensor are connected to the processor. The onboard power system transmits DC power to the processor via a current collector ring after DC power distribution, thus powering the processor. The sensors are powered by the processor after power conversion; the azimuth sensor is directly powered by the onboard power system. The linear displacement signal, azimuth signal, and clock signal from the sensor and the air traffic control system are processed by the processor. The processed rotor plane tilt angle and rotor plane normal vector azimuth angle are transmitted to the flight control system via bus, thereby realizing real-time monitoring of rotor status.

2. A method for measuring the rotor state of a tiltrotor helicopter, characterized in that, The method is executed by means of the tiltrotor helicopter rotor state sensing system of claim 1, the method comprising: Step 1: Determine the relationship between the six-degree-of-freedom platform formed by the linear displacement sensor and the state of the propeller hub; , The tilt angle of the propeller disk plane. Let be the azimuth angle of the normal vector of the propeller disk plane, that is, the angle between the projection of the normal vector onto the oxy plane and the x-axis. Let be the azimuth angle of the propeller disk plane normal vector in the propeller hub rotating coordinate system o1x1y1z1. Rx is the azimuth angle of the x1 axis at time T in the rotating coordinate system o1x1y1z1 of the propeller hub, which is the angle of rotation of the rotating coordinate system about the z axis. Rx is the rotation about the x1 axis and Ry is the rotation about the y1 axis. Step 2: The clock signals of the airborne power supply and flight control system are transmitted to the processor through the collector loop to complete the self-test and data synchronization check of the processor and sensors; Step 3: During flight, acquire linear displacement sensor signals and azimuth angle signals, and transmit them to the processor; Step 4: The processor performs A / D conversion and filtering on the acquired linear displacement sensor signal, and stores the filtered data to obtain valid time-domain data; Step 5: Based on the relationship between the six-degree-of-freedom platform and the rotor hub state determined in Step 1, obtain the rotor disk plane tilt angle and the azimuth angle of the rotor disk plane normal vector through relevant data processing algorithms; Step 6: Transmit the rotor plane tilt angle and rotor plane normal vector calculated by the processor to the flight control system to complete rotor status monitoring; Step 7: Determine whether the rotor disk tilt angle exceeds the relevant angle limit in the flight control system. If the rotor disk tilt angle exceeds the relevant angle limit, adjust the flight attitude. After the adjustment is completed, repeat steps 2 to 6. If the rotor disk tilt angle is within the relevant limit range, continue to maintain flight without adjusting attitude.

3. The method for measuring the rotor state of a tiltrotor helicopter according to claim 2, characterized in that, Step three also includes: Before collecting data, the linear displacement sensor and azimuth sensor need to be calibrated.

4. A tiltrotor helicopter rotor state sensing system, characterized in that, include: Three angular displacement sensors, an azimuth sensor, a current collector ring, and a processor, among which, Three angular displacement sensors are installed between the elastic link and the central component to measure the rotation angle of the elastic link relative to the central component. The elastic link is connected to the central component of the rotor hub by means of a connector, and the intermediate gear of the central component is fixed on the rotor shaft. An azimuth sensor is mounted on a collector ring, which is mounted on the propeller hub. The azimuth sensor measures the azimuth angle of the propeller hub support arm. The outputs of the three angular displacement sensors and the azimuth sensor are connected to the processor. The onboard power system transmits DC power to the processor via a current collector ring after DC power distribution, thus powering the processor. The sensors are powered by the processor after power conversion; the azimuth sensor is directly powered by the onboard power system. The angular displacement signal, azimuth signal, and clock signal from the sensor and the air traffic control system are processed by the processor. The processed rotor plane tilt angle and rotor plane normal vector azimuth angle are transmitted to the flight control system via bus, thereby realizing real-time monitoring of rotor status.

5. A method for measuring the rotor state of a tiltrotor helicopter, characterized in that, The method is performed by means of the tiltrotor helicopter rotor state sensing system of claim 4, and the method includes: Step 1: Determine the relationship between the angular displacement sensor and the rotor hub state; Step 2: The clock signals of the airborne power supply and flight control system are transmitted to the processor through the collector loop to complete the self-test and data synchronization check of the processor and sensors; Step 3: During flight, collect angular displacement sensor signals and azimuth angle signals, and transmit them to the processor; Before collecting data, the angular displacement sensor and azimuth sensor need to be calibrated. Step 4: The processor performs A / D conversion and filtering on the acquired angular displacement sensor signal, and stores the filtered data to obtain valid time-domain data; Step 5: Based on the relationship between the angular displacement sensor and the rotor hub state determined in Step 1, obtain the rotor hub attitude angle information and the azimuth angle of the rotor disk plane normal vector through relevant data processing algorithms. Step 6: Transmit the rotor hub attitude angle and the azimuth angle of the rotor disk plane normal vector calculated by the processor to the flight control system to complete rotor status monitoring; Step 7: In the flight control system, determine whether the rotor disk tilt angle exceeds the relevant angle limit. When the rotor disk tilt angle exceeds the relevant angle limit, adjust the flight attitude. After the adjustment is completed, repeat steps 2 to 6 to adjust and then monitor the rotor hub status. When the rotor disk tilt angle is within the relevant limit range, continue to maintain flight without adjusting the attitude.

6. The method for measuring the rotor state of a tiltrotor helicopter according to claim 5, characterized in that, In step one, the relationship between the angular displacement sensor and the rotor hub state is as follows: The torsion angle amplitude of the elastic connecting rod is equal to the deflection angle amplitude of the elastic universal joint hub, and the phase difference is constant.

7. The method for measuring the rotor state of a tiltrotor helicopter according to claim 6, characterized in that, Step five, specifically: The three sets of filtered RVDT data were subjected to spectrum analysis to obtain the amplitude and phase corresponding to 1 Ω of each angular displacement sensor. Then, the amplitude data corresponding to the three sets of angular displacement sensors were compared to eliminate abnormal data. Finally, the mean value of the normal data was calculated to obtain the rotor hub attitude angle value. The azimuth angle of the propeller disk plane normal vector is determined based on the phase corresponding to 1Ω.

8. The method for measuring the rotor state of a tiltrotor helicopter according to claim 6, characterized in that, Step five, specifically: Select the maximum time-domain amplitude of the three sets of filtered RVDT data and the corresponding time T; The maximum amplitude is used as the tilt angle of the propeller plane; Read the azimuth signal corresponding to time T, and use the azimuth signal corresponding to time T as the azimuth of the propeller disk plane normal vector.

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