Method and device for measuring motion of external suspension of rotorcraft

Abstract

The invention provides a rotor craft external suspension motion measurement method and device, and the method employs a strain test mode, employs a load strain calibration coefficient to calculate an external suspension load, calculates an external suspension rope angle according to course, lateral and vertical loads, carries out the time derivation of the rope angle, obtains an angular rate and an acceleration rate, and achieves the measurement of the external suspension motion of a rotor craft. Therefore, the relative movement of the external hanger relative to the hanging point is deduced. According to the invention, a technical means is provided for accurately measuring the three-dimensional motion trail and motion parameters of the external suspension, and the provided load strain nonlinear calibration method can improve the measurement precision; in addition, the device can adopt a modular design, and is convenient to install, high in precision and strong in universality.

Description

Technical Field

[0001] The invention belongs to the field of aviation technology, and in particular relates to a method and a device for measuring the external suspension motion of a rotorcraft. Background Art

[0002] One of the main features of helicopters is to carry out external suspension flight. Helicopter suspension flight has become the most common mode of transportation for helicopters. The status and value of helicopters have also been fully demonstrated time and again by the mission capabilities of helicopter suspension flight. As early as the 1950s, people began to use helicopters to perform external suspension transportation tasks. With its flexible maneuverability and the advantages of not requiring a dedicated airport, helicopters play an increasingly important role in the field of helicopters. When helicopters perform external suspension transportation flights, they can transport large volumes of cargo without considering the loading volume of the helicopter itself and the matching relationship with the shape of the cargo. They are not restricted by local geographical conditions and traffic conditions. They can transport cargo to remote places that are difficult to reach by general transportation tools, and can deliver cargo accurately and quickly, thereby greatly broadening the scope of transportation, reducing time, speeding up project progress, and improving economic efficiency.

[0003] When a helicopter takes off with a hanging cargo, the hanging cargo will generate additional aerodynamic loads and inertial loads during normal hanging flight, which will be coupled with the movement of the helicopter, causing the helicopter's flight dynamics to change. If the pilot is unaware of the change in the hanging cargo load and fails to adjust the flight attitude in time, the flight stability will be affected. At this time, once the engine fails, the helicopter is likely to enter the danger zone (avoidance zone) determined by the combination of flight altitude and flight speed, causing a safety accident; after arriving at the destination, due to the ground effect and other environmental influences, the pilot needs to concentrate on controlling the helicopter, especially when there is only one pilot, and has no time to take care of the drop operation of the hanging cargo. Therefore, in the helicopter design stage, it is necessary to establish a complete helicopter external hanging model coupled with a flight dynamics model to analyze the characteristics of different flight states.

[0004] The precise measurement of the motion of the helicopter external pylon provides test data for the correction and verification of the flight test for the establishment of a high-confidence flight dynamics model of the helicopter / pylon combination. Due to the relative motion and mutual coupling between the helicopter and the external pylon, the relatively large pylon, and the compound torsion and swing motion, the precise measurement of the three-dimensional motion trajectory and motion parameters of the external pylon has always been an unresolved problem. Summary of the invention

[0005] In order to solve the measurement problem of the three-dimensional motion trajectory and motion parameters of the external suspension, the present invention provides a rotorcraft external suspension motion measurement method and device based on strain testing. By installing a set of portable strain measurement devices and load calibration coefficients, the three different direction loads corresponding to the body coordinate system are obtained. The angle can be obtained by trigonometric calculation, and the corresponding angular velocity and speed can be obtained by time differentiation, which can meet the relative motion measurement requirements of the external suspension motion parameters of the helicopter test flight and ensure the safety of the helicopter suspension flight. The technical solution is as follows:

[0006] In a first aspect, a method for measuring the motion of an external suspension of a rotorcraft is provided. The method adopts a strain test method, uses a load-strain calibration coefficient to calculate the load of the external suspension, calculates the angle of the external suspension rope according to the heading, lateral and vertical loads, and then takes the time derivative of the rope angle to obtain the angular velocity and acceleration rate, thereby deriving the relative velocity and relative acceleration of the external suspension relative to the suspension point.

[0007] Optionally, the method comprises:

[0008] Step 1: Arrange the strain assembly at the connecting rod beam between the helicopter and the external suspension;

[0009] Step 2: Install a data acquisition system on the helicopter fuselage;

[0010] Step 3: When the helicopter is not in operation, loads fx, fy and fz are applied to the connection point between the helicopter and the external suspension along the heading, lateral and vertical directions respectively, and the data acquisition system collects strain data of the strain component;

[0011] Step 4, processing the strain data in step 3 to obtain the load strain coefficient matrix K;

[0012] Step 5: When the helicopter is in flight, the data acquisition system collects strain data of the strain component;

[0013] Step 6: Based on the load strain coefficient matrix K in step 4 and the strain data collected in step 5, the extended least square method is used to invert and obtain the actual loads Fx, Fy and Fz in the heading, lateral and vertical directions;

[0014] Step 7: Based on the actual loads Fx, Fy and Fz obtained in step 6, the rope angle is obtained by combining the trigonometric function projection relationship between the three forces;

[0015] Step 8: Derivative the rope angle obtained in step 7 with time to obtain the angular velocity and acceleration rate of the rope, and then multiply by the rope length to derive the relative velocity and relative acceleration of the external suspension relative to the suspension point.

[0016] In step 1, the number of strain components arranged is ≥ 6. To improve the accuracy, each strain component adopts a full bridge or a half bridge.

[0017] Among them, in order to avoid being affected by fuselage overload, the strain component in step 1 should not be arranged on the fuselage load-bearing frame beam, but should be arranged above the external hanging cable point, which is on the fuselage connecting rod beam.

[0018] Among them, the vertical load satisfies: fz ≥ 2 times the maximum external hanging design weight Mg; considering the difference between tensile and compressive loads and strain coefficients, the heading load satisfies: -0.5Mg ≤ fx ≤ 0.5Mg; the lateral load satisfies: -0.5Mg ≤ fy ≤ 0.5Mg.

[0019] Among them, in step 4, considering the difference between tensile and compressive loads and strain coefficients, in order to reduce the error, a quadratic curve is used to express the load-strain relationship as follows:

[0020] εi=k11*Fx 2 +k12*Fx+k13*Fy 2 +k14*Fy+k15*Fz 2 +k15*Fz,

[0021] The corresponding rectangular form is:

[0022]

[0023] The load strain coefficient matrix K is calculated as:

[0024]

[0025] in,

[0026] εi represents the strain value of the bridge at the i-th measuring point collected in step 32,

[0027] ki1 is the heading calibration load fx 2 The influence coefficient on the strain of the strain component at the i-th measuring point;

[0028] ki2 is the influence coefficient of the heading calibration load fx on the strain of the strain component at the i-th measuring point;

[0029] ki3 is the lateral calibration load fy 2 The influence coefficient on the strain of the strain component at the i-th measuring point;

[0030] ki4 is the influence coefficient of the lateral calibration load fy on the strain of the strain component at the i-th measuring point;

[0031] ki5 is the vertical calibration load fz 2 The influence coefficient on the strain of the strain component at the i-th measuring point;

[0032] ki6 is the influence coefficient of the vertical calibration load fz on the strain of the strain component at the i-th measuring point.

[0033] Among them, in step 6, the inverse of the extended least squares method is used to obtain the actual loads Fx, Fy and Fz borne by the external suspension, and the calculation formula is:

[0034]

[0035] INV represents matrix inversion, []' represents matrix transposition, εi is the strain value of the strain component; Fx is the actual load in the heading direction of the external suspension, Fy is the actual load in the lateral direction, and Fz is the actual load in the vertical direction; kn1 represents the number of strain components with the subscript n.

[0036] In step 7, the rope angles include: heading angle θ1 and yaw angle Based on the Fx, Fy and Fz obtained in step 6, combined with the trigonometric function projection relationship between the three forces, the rope angle is calculated according to the following formula:

[0037]

[0038] Among them, in step 8, the time derivative of the rope angle obtained in step 7 is performed to calculate the relative speed of the external suspension relative to the suspension point and the acceleration.

[0039] The calculation formula of the relative speed of the external suspension to the suspension point is:

[0040]

[0041] The calculation formula for the relative acceleration of the external suspension relative to the suspension point is:

[0042]

[0043] Where l is the length of the rope, is the relative speed of heading at time k, is the lateral relative velocity at time k; is the vertical relative velocity at time k; Δt is the sampling interval; is the relative acceleration of heading at time k, is the lateral relative acceleration at time k, is the vertical relative acceleration at time k.

[0044] In a second aspect, a device for measuring the motion of an external pylon of a rotorcraft is provided, comprising: a strain component, a data acquisition system, and a processor; the strain component is located at a connecting rod beam between a helicopter and an external pylon, and is used to measure strain data;

[0045] The data acquisition system is connected to the strain component and is used to collect strain data of the strain component;

[0046] The processor is used to:

[0047] The strain data is processed to obtain the load strain coefficient matrix K;

[0048] According to the load strain coefficient matrix K and strain data, the extended least square method is used to invert and obtain the actual loads Fx, Fy and Fz in the heading, lateral and vertical directions;

[0049] According to the actual loads Fx, Fy and Fz in heading, lateral and vertical directions, the rope angle is obtained by combining the trigonometric function projection relationship between the three forces;

[0050] The time derivative of the rope angle is taken to obtain the angular velocity and acceleration rate of the rope, which are then multiplied by the rope length to derive the relative velocity and acceleration of the external suspension relative to the suspension point.

[0051] The beneficial effects of the present invention are at least:

[0052] The present invention discloses a method and device for measuring the motion of an external suspension of a rotorcraft based on strain testing, which provide technical means for accurately measuring the three-dimensional motion trajectory and motion parameters of the external suspension. At the same time, the present invention provides a load strain nonlinear calibration method, which can greatly improve the accuracy. In addition, the device can adopt a modular design, is easy to install, has high accuracy, strong versatility, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the definition of the helicopter body axis and hanging posture of the present invention;

[0054] Figure 2 It is a composition diagram of the device of the present invention;

[0055] Figure 3 It is the full bridge strain composition diagram of the present invention;

[0056] Figure 4 It is a composition diagram of the test acquisition system of the present invention;

[0057] Figure 5 This is a schematic diagram of external hanging heading calibration loading of the present invention;

[0058] Figure 6 It is a schematic diagram of the lateral load calibration curve of the present invention;

[0059] Figure 7 is a schematic diagram of a load identification curve of the present invention;

[0060] Figure 8 It is the heading angle identification curve of the present invention. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below through specific implementation modes and drawings.

[0062] The generalized coordinates for measuring the suspension displacement (suspension attitude angle) are defined within the helicopter body axis system, such as Figure 1 As shown, θ1 and They are called the suspension's back swing angle (heading angle) and side swing angle (yaw angle), and the vector

[0063] The external hanging joint is fixed under the middle part of the fuselage. During flight, random loads are generated due to gravity, resistance and movement of the external hanging. The external hanging load is transmitted to the fuselage through the rope along the direction of the rope, which can be decomposed into heading load Fx, vertical load Fz and lateral load Fy. These loads produce strain in the fuselage structure.

[0064] The coordinates of the center of mass of the suspension with the suspension point as the origin are:

[0065]

[0066] In the formula, r1 is the distance from the center of gravity of the fuselage to the point where it is suspended on the fuselage;

[0067] Consider the external hanging position and the external hanging load force F L The directions are exactly the same, the axial load Fx, the vertical load Fz and the lateral load Fy are equal to the resultant force F L The relationship is as follows:

[0068]

[0069] The relationship between the strain εi at each measuring point of the structure and the load F can be expressed by a linear equation: εi=k11*F,

[0070] The present invention takes into account the difference in load-strain variation coefficient under tensile and compressive loads, and uses a quadratic curve to give a calibration curve εi=k11*F 2 +k12*F,

[0071] Structural strain follows the principle of linear superposition, that is, when the structure is subjected to axial load, vertical load and lateral load at the same time, the strain value of each measuring point is the linear superposition of the strain when these loads act separately.

[0072] The relationship between the strain εi of the bridge at the i-th measuring point of the external hanging load-bearing structure and the load can be expressed by a nonlinear equation:

[0073] εi=k11*Fx 2 +k12*Fx+k13*Fy 2 +k14*Fy+k15*Fz 2 +k15*Fz

[0074] εi represents the strain value of the bridge at the i-th measuring point, which can be written in rectangular form as follows:

[0075]

[0076] By testing the strain of each measuring point during flight, When known, the heading load, vertical load and lateral load can be obtained by the extended least squares method.

[0077] The present invention arranges multiple sets of strain bridges in the structure connecting the main load-bearing points in the fuselage, tests the strain value during flight, combines the calibration coefficient matrix, uses the least square method to obtain the external suspension load, solves the heading angle and yaw angle based on trigonometric functions, and then solves the angle against time to obtain the relative speed and relative acceleration of the external suspension movement. The method of the present invention mainly includes strain testing, ② data acquisition system, ③ calibration coefficient and load decoupling algorithm, ④ load-based angle solution algorithm, see Figure 1 .

[0078] 1) Arrange multiple sets of strain test points in the structure connected to the main load-bearing points in the machine body

[0079] The strain gauge converts the relative deformation of the test piece into a change in resistance. Each test point uses a full bridge or half bridge to improve accuracy. Considering the three directions of X, Y, and Z, the number of test points is ≥6; the strain gauge is mainly composed of four parts: grid wire, substrate, cover layer and lead wire. The grid wire is also called sensitive grid, which is the main factor determining the performance index of the strain gauge.

[0080] 2) Data acquisition system

[0081] The strain gauge strain measurement system generally consists of four parts: sensor (Wheatstone bridge composed of strain gauge), signal conditioner (mainly composed of excitation source and signal amplifier) ​​and data acquisition and recording system and its software system.

[0082] 3) Calibration coefficient and load decoupling algorithm

[0083] At the position of the external hanging ring, fix an angle steel with two bolts, and then use three aluminum levers to form a two-stage lever system, and finally synthesize a loading point. Use a hand chain hoist to apply static loads of 0.1mg, 0.2mg, 0.4mg...1.0mg step by step along the heading, and measure the static bending strain of positive loading in the heading; use a hand chain hoist to apply static loads fx of -0.1mg, -0.2mg, -0.4mg...-1.0mg step by step along the heading, and measure the static bending strain of negative loading in the heading;

[0084] After load calibration, a load-strain relationship curve is obtained. In the present invention, the difference in load-strain variation coefficient under tensile and compressive loads is considered, and a calibration curve is given using a quadratic curve. Each calibration test is repeated 3 times, and k11 and k12 are obtained using the least squares method.

[0085] εi x=k11*fx 2 +k12*fx

[0086] By using a hand chain hoist to apply static loads of 0.1mg, 0.2mg, 0.4mg...1.0mg step by step laterally, the static bending strain under lateral positive loading is measured; by using a hand chain hoist to apply static loads fy step by step laterally of -0.1mg, -0.2mg, -0.4mg...-1.0mg, the static bending strain under lateral negative loading is measured, and k13 and k14 are calculated in the same way.

[0087] By using a hand chain hoist to apply static load fz in the vertical direction step by step -0.3mg, -0.6mg, -0.9mg…3.0mg, the static bending strain under vertical positive loading is measured, and k15 and k16 are also calculated.

[0088] At this time, the linear superposition relationship between the strain at each measuring point of the structure and the multiple loads can be expressed by the linear equation:

[0089] εi=k11**fx 2 +k12*fx+k13*fy 2 +k14*fy+k15*fz 2 +k16*fz

[0090] εi represents the strain value of the bridge at the i-th measuring point, which can be written in matrix form as:

[0091]

[0092] 4) Identify external hanging load by strain:

[0093] By testing the strain of each measuring point in flight, the number of measuring points n is required to be ≥ 6, and the load-strain calibration coefficient matrix When known, the heading load Fx, vertical load Fz and lateral load Fy can be obtained by the extended least squares method, the formula is:

[0094]

[0095] Among them, INV means matrix inversion, []' means matrix transposition;

[0096] εi is the strain value of the strain component;

[0097] Fx is the external hanging heading load, Fy is the lateral load, and Fz is the vertical load;

[0098] kn1 represents the number of strain components with subscript n.

[0099] 5) Calculate the relative motion of the external suspension through the structural load relationship:

[0100] The axial load Fx, vertical load Fz and lateral load Fy are related to the resultant force F L The projection formula is:

[0101]

[0102] From the above formula, we can get:

[0103] θ1=acos(Fz / F L )

[0104]

[0105] The relative position vector of the external suspension:

[0106]

[0107] By using the differential formula to derive the position vector, the relative velocity can be obtained. The discrete form can be expressed as follows:

[0108]

[0109] By using the differential formula to derive the velocity vector, the relative acceleration can be obtained. The discrete form can be expressed as follows:

[0110]

[0111] For example, in one embodiment, the maximum external hanging weight of the helicopter is 3600kg, the external hanging rope is 3m long, and 6 groups of full bridge strain are arranged on the fuselage connecting rod beam above the external hanging rope point. Figure 3 , add a test system, the collector uses the universal collector UMA2000, collects PCM signals, uses the MDR data recorder to record data and display it in real time for monitoring, and adds a B code generator to output the IRIG-B120 clock code to synchronize the UMA2000 airborne collector to form time synchronization. The fuselage test system uses a 28V power supply, and the power does not exceed 700W. Its test collection composition is shown in Figure 4 .

[0112] Calibrate according to the plan. See the schematic diagram of external hanging lateral calibration loading for details. Figure 5 , the calibration results are shown in Figure 6 , and the equation of the lateral load calibration curve is obtained: y = 1E-13x2 + 1E-08x + 2E-05;

[0113] The calculation is carried out according to the external hanging motion measurement method of the present invention, and the result curve is shown in FIG. Figure 7 , which is the heading angle identification curve.

[0114] The above only expresses the implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. In addition, the parts not detailed in the present invention are all conventional technologies.

Claims

1. A method for measuring the external suspension motion of a rotorcraft, characterized in that: The strain test method is adopted to calculate the external hanging load using the load-strain calibration coefficient. The external hanging rope angle is calculated according to the heading, lateral and vertical loads. The angular velocity and acceleration rate are then obtained by taking the time derivative of the rope angle, thereby deducing the relative velocity and relative acceleration of the external hanging relative to the hanging point.

2. The method according to claim 1, characterized in that The method comprises: Step 1: Arrange the strain assembly at the connecting rod beam between the helicopter and the external suspension; Step 2: Install a data acquisition system on the helicopter fuselage; Step 3: When the helicopter is not in operation, loads fx, fy and fz are applied to the connection point between the helicopter and the external suspension along the heading, lateral and vertical directions respectively, and the data acquisition system collects strain data of the strain component; Step 4, processing the strain data in step 3 to obtain the load strain coefficient matrix K; Step 5: When the helicopter is in flight, the data acquisition system collects strain data of the strain component; Step 6: Based on the load strain coefficient matrix K in step 4 and the strain data collected in step 5, the extended least square method is used to invert and obtain the actual loads Fx, Fy and Fz in the heading, lateral and vertical directions; Step 7: Based on the actual loads Fx, Fy and Fz obtained in step 6, the rope angle is obtained by combining the trigonometric function projection relationship between the three forces; Step 8: Derivative the rope angle obtained in step 7 with time to obtain the angular velocity and acceleration rate of the rope, and then multiply by the rope length to derive the relative velocity and relative acceleration of the external suspension relative to the suspension point.

3. The method according to claim 2, characterized in that In step 1, the number of strain components arranged is ≥ 6, and each strain component adopts a full bridge or a half bridge.

4. The method according to claim 2, characterized in that: In step 1, the strain assembly is arranged above the external hanging cable point, which is on the fuselage connecting rod beam.

5. The method according to claim 2, characterized in that: In step 3, the vertical load satisfies: fz ≥ 2 times the maximum external hanger design weight Mg; the heading load satisfies: -0.5Mg ≤ fx ≤ 0.5Mg; the lateral load satisfies: -0.5Mg ≤ fy ≤ 0.5Mg.

6. The method according to claim 2, characterized in that In step 4, a quadratic curve is used to express the load-strain relationship as: εi=k11*Fx 2 +k12*Fx+k13*Fy 2 +k14*Fy+k15*Fz 2 +k15*Fz, The load strain coefficient matrix K is calculated as: in, εi represents the strain value of the bridge at the i-th measuring point collected in step 32, ki1 is the heading calibration load fx 2 The influence coefficient on the strain of the strain component at the i-th measuring point; ki2 is the influence coefficient of the heading calibration load fx on the strain of the strain component at the i-th measuring point; ki3 is the lateral calibration load fy 2 The influence coefficient on the strain of the strain component at the i-th measuring point; ki4 is the influence coefficient of the lateral calibration load fy on the strain of the strain component at the i-th measuring point; ki5 is the vertical calibration load fz 2 The influence coefficient on the strain of the strain component at the i-th measuring point; ki6 is the influence coefficient of the vertical calibration load fz on the strain of the strain component at the i-th measuring point.

7. The method according to claim 1, characterized in that In step 6, the inverse of the extended least squares method is used to obtain the actual loads Fx, Fy and Fz borne by the external suspension. The calculation formula is: INV represents matrix inversion, []' represents matrix transposition, εi is the strain value of the strain component; Fx is the actual load in the heading direction of the external suspension, Fy is the actual load in the lateral direction, and Fz is the actual load in the vertical direction; kn1 represents the number of strain components with the subscript n.

8. The method according to claim 2, characterized in that: In step 7, the rope angles include: heading angle θ1 and yaw angle Based on the Fx, Fy and Fz obtained in step 6, combined with the trigonometric function projection relationship between the three forces, the rope angle is calculated according to the following formula:

9. The method according to claim 1, characterized in that: In step 8, the time derivative of the rope angle obtained in step 7 is performed to obtain the relative speed of the external suspension relative to the suspension point and the acceleration. The calculation formula of the relative speed of the external suspension to the suspension point is: The calculation formula for the relative acceleration of the external suspension relative to the suspension point is: Where l is the length of the rope, is the relative heading speed at time k, is the lateral relative velocity at time k; is the vertical relative velocity at time k; Δt is the sampling interval; is the relative acceleration of heading at time k, is the lateral relative acceleration at time k, is the vertical relative acceleration at time k.

10. A device for measuring the external suspension motion of a rotorcraft, characterized in that: include: Strain components, data acquisition systems, processors; The strain component is located at the connecting rod beam between the helicopter and the external pylon and is used to measure strain data; The data acquisition system is connected to the strain component and is used to collect strain data of the strain component; The processor is used to: The strain data is processed to obtain the load strain coefficient matrix K; According to the load strain coefficient matrix K and strain data, the extended least square method is used to invert and obtain the actual loads Fx, Fy and Fz in the heading, lateral and vertical directions; According to the actual loads Fx, Fy and Fz in heading, lateral and vertical directions, the rope angle is obtained by combining the trigonometric function projection relationship between the three forces; The time derivative of the rope angle is taken to obtain the angular velocity and acceleration rate of the rope, which are then multiplied by the rope length to derive the relative velocity and acceleration of the external suspension relative to the suspension point.

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