A method for calculating the trim control amount of a tiltrotor under sideslip

Abstract

The present invention discloses a method for calculating the trim control amount of a tilt-rotor under sideslip, which includes establishing a connection between the trim control amount between the flight state without sideslip and the flight state with sideslip; establishing a connection between the trim control amount between the left-hand rotor and the right-hand rotor on the same aircraft; converting the trim control amount calculation of the tilt-rotor under different nacelle inclination angles, different rotor rotation directions, different flight speeds, and different angles of attack and sideslip into a trim control amount calculation that only includes the flight speed, the angle between the flight speed vector and the blade disc plane. The present invention greatly reduces the number of rotor trim states, thereby reducing the difficulty of simulation calculation.

Description

Technical Field

[0001] The invention relates to the technical field of helicopter aerodynamics and computational fluid dynamics, and in particular to a method for calculating a tiltrotor trim control amount under sideslip. Background Art

[0002] Rotor trim is an essential part of wind tunnel testing or CFD numerical simulation of rotorcraft. It refers to the process of achieving a given drag coefficient and rotor cone chamfer by adjusting the total pitch angle and cyclic pitch angle under specified flight speed and rotor shaft inclination. Rotor trim restores the actual flight state of the rotor, making the flow field and aerodynamic characteristics consistent with those of a real aircraft. At present, CFD technology has made great progress in the simulation of unsteady flow fields of rotors. However, using CFD methods to trim rotor control variables is still a time-consuming and labor-intensive process. The traditional practice of relying on engineering analysis methods or wind tunnel tests to provide rotor control variables has great limitations, which restricts the widespread application of CFD technology in the study of rotor aerodynamic characteristics.

[0003] Tilt-rotor aircraft are a new type of aircraft that combines the characteristics of helicopters and propeller fixed-wing aircraft. Unlike helicopters, tilt-rotor aircraft generally use rotors arranged in pairs in a horizontal row, and the two rotors rotate in opposite directions, so that the anti-torque generated by the rotors on the fuselage cancels each other out, and a separate tail is no longer needed to balance the anti-torque. Due to the unsteady characteristics of the rotor, the balancing calculation needs to simulate multiple rotation cycles, resulting in a long total calculation time and high cost. Tilt-rotor aircraft are generally equipped with left-hand rotors and right-hand rotors, and the flight state includes 0~ The calculation cost of all the combinations of tilt angle, different flight speeds, angle of attack and sideslip angle is extremely high, which restricts the application of computational fluid dynamics (CFD) methods in engineering.

[0004] In addition, the tilt rotor is equipped with a rotor shaft tilt mechanism, which allows the rotor shaft to be tilted between 0~ The aircraft experiences the rotor axis from takeoff to high-speed forward flight. Vertical takeoff, from arrive Transition flight, rotor shaft The rotor axis of the tilt-rotor is 0~ The changes in the left and right rotation direction of the rotor, combined with different flight speeds, angles of attack and sideslip angles, result in a large number of conditions where the rotor control variables need to be trimmed. The calculation cost of using the CFD direct balancing method to trim the rotor is very high, and it is necessary to develop an efficient rotor balancing strategy based on the characteristics of the tilt-rotor. Summary of the invention

[0005] In view of this, the present invention provides a method for calculating the trim control amount of a tiltrotor under sideslip.

[0006] The present invention discloses a method for calculating a tiltrotor trim control amount under sideslip, which comprises:

[0007] Step 1: Establish the relationship between the trim control amount between the no-skid and sideslip flight states;

[0008] Step 2: Establish the relationship between the trim control variables between the left-hand rotor and the right-hand rotor on the same aircraft;

[0009] Step 3: Convert the trim control calculation of the tiltrotor at different nacelle inclination angles, different rotor rotation directions, different flight speeds, and different angles of attack and sideslip into a trim control calculation that only includes the flight speed and the angle between the flight speed vector and the rotor disc plane.

[0010] Furthermore, the step 1 comprises:

[0011] Step 11: First calculate the flight speed vector in the hub coordinate system The velocity component of the flight speed is parallel to the propeller plane. The velocity component of the propeller and the velocity component perpendicular to the propeller disc plane are then used to calculate the angle between the flight speed and the propeller disc plane in the hub coordinate system. And the velocity component parallel to the propeller disc plane and the hub coordinate axis Angle ;

[0012] Step 12: Move the blade at zero phase around the hub axis Rotation Angle, the blade pointing and the flight speed parallel to the propeller plane component Similarly, the rotor control amount balance problem is converted into a flight speed of , the angle between the flight speed and the propeller plane is The balancing problem in the no-sideslip state;

[0013] Step 13: Calculate the cyclic pitch of the left-rotating rotor without sideslip and the right-rotating rotor without sideslip. By converting the trim control amount from the no-sideslip state to the sideslip state, the cyclic pitch of the left-rotating rotor with sideslip and the right-rotating rotor with sideslip can be obtained.

[0014] Furthermore, in the body coordinate system, the origin of the coordinate is the center of mass of the aircraft, the X-axis is along the axis of the fuselage, the Z-axis is located in the longitudinal symmetry plane, perpendicular to the OX-axis, and upward is positive, and the Y-axis is perpendicular to the longitudinal symmetry plane and rightward is positive; the hub coordinate system The origin is located at the center of the rotor, and the orientation is tilted around the Y axis by the body coordinate system The angle is obtained, is the forward tilt angle of the rotor shaft.

[0015] Furthermore, the step 11 comprises:

[0016] The flight speed is known to be V, and the angle of attack is and sideslip angle , get the velocity components in three directions in the body coordinate system , , ; The relationship between the body coordinate system and the velocity vector is expressed by the angle of attack and sideslip angle express;

[0017] According to the velocity components in three directions in the body coordinate system, the velocity components of the velocity vector in the hub coordinate system are obtained;

[0018] According to the velocity component of the velocity vector in the hub coordinate system, calculate the and .

[0019] Furthermore, the velocity components in the three directions in the body coordinate system are:

[0020] (1)

[0021] in, , , They are the velocity components of the flight speed V on the X-axis, Y-axis and Z-axis in the body coordinate system;

[0022] The velocity component of the flight speed in the hub coordinate system is:

[0023] (2)

[0024] in, , , They are V in the hub coordinate system Next axis, axis, Velocity components of the axis;

[0025] Calculate the hub coordinate system and :

[0026] (4).

[0027] Furthermore, in step 13, calculating the cyclic pitch variation in the left-hand rotor state without sideslip includes:

[0028] For a left-hand rotor, if the flight speed is known to be , hub coordinate system , and under zero sideslip conditions, the rotor trim control amount is the total pitch , the lateral and longitudinal periodic pitch are and , then at the angle In this case, the periodic pitch variation in the trim state is derived through the following relationship:

[0029] Rotate the rotor blade in the direction of rotation Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and ; At this time, the cyclic pitch variation of the rotor is described as:

[0030] (5)

[0031] in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor;

[0032] The cyclic pitch variation of the left-hand rotor is obtained as:

[0033] (6).

[0034] Furthermore, in step 13, calculating the cyclic pitch variation in the right-hand rotor state without sideslip includes:

[0035] For a right-hand rotor, if the flight speed is known to be , hub coordinate system , and under zero sideslip conditions, the rotor trim control amount is the total pitch , the lateral and longitudinal periodic pitch are and , then at the angle In this case, the periodic pitch variation in the trim state is derived through the following relationship:

[0036] For right-hand rotors, rotate the rotor disc in the opposite direction of rotation. Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and , the cyclic pitch variation of the rotor is described as:

[0037] (7)

[0038] in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor;

[0039] The cyclic pitch variation of the right-hand rotor is obtained as follows:

[0040] (8).

[0041] Furthermore, in step 13, the cyclic pitch change in the left-hand rotor with sideslip and the right-hand rotor with sideslip is obtained by converting the trim control amount from the non-sideslip state to the sideslip state, including:

[0042] At a known angle of attack , Sideslip Angle , Cyclic torque variation of the rotor Under this premise, the angle between the flight speed and the propeller disc plane is obtained , and the flight speed component parallel to the disc plane and the hub coordinate system Axis Angle , the expression is:

[0043] (9)

[0044] Therefore, under the premise that the flight speed and the angle between the rotor disc plane and the rotor blade are equal, if the trim control amount of the rotor in the non-sideslip state is known, the trim control amount in the sideslip state can be directly calculated by formula (6) (applicable to left-hand rotors) or formula (8) (applicable to right-hand rotors).

[0045] Furthermore, the step 2 comprises:

[0046] The conversion formula from left-hand rotor to right-hand rotor is:

[0047] (10)

[0048] The conversion formula from right-hand rotor to left-hand rotor is:

[0049] (11).

[0050] Furthermore, the step 3 comprises:

[0051] In the full state calculation, first construct the change matrix of the trim control amount Any combination of flight speed and shaft inclination angle is converted into the hub coordinate system State, in the known control variable change matrix Interpolation to get the current state The amount of manipulation , get the left or right rotor in The trim control amount under the state; is the manipulated variable change matrix, is the flight speed in the current state, is the angle between the flight speed and the propeller disc plane in the current state, The current flight speed is parallel to the propeller disc plane component and the hub coordinate axis The full state includes different flight speeds, angle of attack, sideslip angle, rotor shaft inclination angle, and left / right rotation direction.

[0052] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0053] 1. The calculation method established by the present invention is applicable to conventional helicopters and tilt-rotor aircraft. For conventional helicopters, the number of independent variables affecting the rotor trim control amount is reduced from 3 (speed, angle of attack and sideslip angle) to 2; for tilt-rotor aircraft, the number of independent variables affecting the rotor trim control amount is reduced from 5 (speed, angle of attack, sideslip angle, nacelle inclination angle, rotor rotation direction) to 2. By simplifying multiple parameter combinations into two independent variables, the number of rotor trim states is greatly reduced.

[0054] 2. The present invention establishes the connection between the rotor trim control amount between the flight state without sideslip and the flight state with sideslip, and also establishes the connection between the trim control amount between the left-hand rotor and the right-hand rotor on the same aircraft, reducing the calculation of the rotor trim control amount from the combination of multiple parameters such as flight speed, angle of attack, sideslip angle, shaft inclination angle, left-hand rotation, right-hand rotation to only two parameter combinations of flight speed and flight speed and the angle between the propeller disc plane. The present invention establishes a rotor trim control amount database with flight speed and propeller disc plane angle as variables, and can derive the rotor trim control amount between 0 and The trim control values ​​of left-hand and right-hand rotors at any tilt angle within a range, any flight angle of attack and sideslip angle greatly reduce the difficulty of simulation calculations, allowing engineers to obtain the trim control values ​​of the rotor at a lower computing cost, and provide input conditions for the aerodynamic performance analysis of the entire aircraft in all states.

[0055] 3. The calculation method established by the present invention is applicable to conventional rotors and tiltrotors. Its value lies in that it narrows the variable range of the calculation of the rotor trim control amount to only the flight speed and the flight speed blade plane angle (defined as the reference state). The rotor trim control amount in any other state can be calculated from the reference state through the theoretical formula, which greatly reduces the number of rotor trim states and is of great significance for the steady-state flight aerodynamic performance evaluation of rotorcraft.

[0056] 4. Numerical calculation results show that the rotor thrust and torque obtained by using the trim control variables derived by this method to calculate the rotor flow field are consistent with the target values, verifying the correctness of the theoretical method. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0058] Figure 1 A schematic diagram of a hub coordinate system and a left-hand rotor according to an embodiment of the present invention;

[0059] Figure 2 A schematic diagram of an airframe / hub coordinate system and velocity vectors according to an embodiment of the present invention;

[0060] Figure 3 Schematic diagram of propeller disc plane velocity components and blade orientations according to an embodiment of the present invention;

[0061] Figure 4 A schematic diagram of changes in pull coefficient and turning moment during rotor trimming according to an embodiment of the present invention;

[0062] Figure 5 It is a schematic diagram comparing cyclic pitch variation of a left-handed rotor with sideslip, a right-handed rotor with sideslip, and a rotor without sideslip according to an embodiment of the present invention;

[0063] Figure 6 is the trim control amount of the embodiment of the present invention Schematic diagram comparing theoretical formula results and CFD results;

[0064] Figure 7 is the trim control amount of the embodiment of the present invention Schematic diagram comparing theoretical formula results and CFD results. DETAILED DESCRIPTION

[0065] The present invention is further described in conjunction with the accompanying drawings and embodiments, and the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field should fall within the scope of protection of the embodiments of the present invention.

[0066] Definitions of terms used in this invention:

[0067] ① Tilt-rotor: A rotor system with unique performance. The rotor tilt device is designed to allow the rotor shaft to rotate between horizontal and vertical positions. The angle between the rotor shaft and the ground is called the shaft tilt angle. When taking off or landing vertically, the rotor shaft is perpendicular to the ground, in a helicopter rotor flight state. When flying horizontally at high speed, the rotor shaft is parallel to the ground, in a propeller flight state.

[0068] ② Left-hand / right-hand rotor: Tilt-rotor aircraft usually adopt the layout form of rotor configuration in pairs, and the two rotors rotate in opposite directions, and the anti-torque generated cancels each other out. When viewed from the top of the rotor disc, a rotor that rotates clockwise is called a left-hand rotor, which means that the blade at the 6 o'clock position rotates to the left, and vice versa, a rotor that rotates counterclockwise is called a right-hand rotor.

[0069] ③ Cyclic pitch variation: It is a method of periodically changing the pitch of the blades during rotation. The pilot tilts the rotor cone through cyclic pitch variation to control the direction of the rotor aerodynamic force and achieve stability and control of the aircraft.

[0070] ④ Rotor balancing: by adjusting the rotor control amount, the rotor aerodynamic force, torque or flapping reaches the preset target value. The present invention is aimed at the rotor wind tunnel state balancing, the rotor control amount is the total pitch and cyclic pitch, and the balancing target value is the rotor's pull and pitch and roll torque.

[0071] Based on the characteristics of rotor flow, the present invention decomposes the flight speed into two parts: the speed component on the rotor plane and the speed component perpendicular to the rotor. For the flow part in the rotor plane, the flight sideslip angle is described by the blade azimuth angle, and the expression of the cyclic variable pitch trim control amount under any sideslip angle is derived. On this basis, the corresponding relationship between the trim control amount with and without sideslip is further derived, as well as the corresponding relationship between the trim control amount between the left-hand rotor and the right-hand rotor. Figure 1 The present invention provides an embodiment of a method for calculating a tiltrotor trim control amount under sideslip, which comprises:

[0072] Figure 1 The coordinate system of the body is shown Hub coordinate system , where the forward tilt angle of the rotor shaft is The figure also gives a schematic diagram of the velocity vector. The relationship between the body coordinate system and the velocity vector is expressed by the angle of attack. and sideslip angle In the body coordinate system, the origin of the coordinate is the center of mass of the aircraft, the X axis is along the axis of the fuselage, the Z axis is located in the longitudinal symmetry plane, perpendicular to the OX axis, and upward is positive, and the Y axis is perpendicular to the longitudinal symmetry plane, and rightward is positive; hub coordinate system The origin is located at the center of the rotor, and the orientation is tilted around the Y axis by the body coordinate system The angle is obtained, is the forward tilt angle of the rotor shaft.

[0073] First, we can calculate the angle of attack of the velocity vector in the hub coordinate system and sideslip angle . Under the current angle of attack and sideslip of the hub coordinate system, how much angle can be rotated around the rotor axis to make the velocity vector lie on the longitudinal symmetry plane of the hub coordinate system, and what is the angle between the velocity vector and the X axis at this time. The essence of this problem is what is the so-called sideslip angle and angle of attack when the rotation order is changed. In other words, from the body coordinate system to the airflow coordinate system, the normal approach is to rotate around the Y axis first - Angle, then rotate around the Z axis - Angle. The current situation is that we rotate around the Z axis first. , rotate around the Y axis - , it is necessary to find the angle between the flight speed and the propeller disc plane in the hub coordinate system And the flight speed is parallel to the propeller disc plane component and the hub coordinate axis Angle The specific steps are as follows.

[0074] The flight speed is known to be V, and the angle of attack is and sideslip angle , the velocity vectors in the three directions in the body coordinate system are:

[0075] (1)

[0076] in, , , They are the velocity components of the flight speed V on the X-axis, Y-axis and Z-axis in the body coordinate system;

[0077] The hub coordinate system is the body coordinate system tilted around the Y axis Angle (forward is a negative value), so the component of the flight velocity vector in the hub coordinate system is:

[0078] (2)

[0079] in, , , They are V in the hub coordinate system Next axis, axis, Velocity components of the axis;

[0080] Figure 2 The velocity vector diagram in the hub coordinate system is given. The three velocity components in the hub coordinate system are known. Later, the angle of attack in the hub coordinate system can be calculated and sideslip angle .

[0081] (3)

[0082] Figure 2 Medium Vector represents the velocity vector, for Point Projection of the plane, for Point Projection of the plane, flight speed vector The velocity component in the propeller disc plane is , Coordinate axis with hub The angle is ; In addition, the velocity vector The velocity component perpendicular to the propeller disc plane is ,Will With hub plane The angle is defined as . That is, OP needs to go around Angle of axis rotation , as can be seen from the schematic diagram

[0083] (4)

[0084] Figure 2 The plane formed by the blade's rotation is represented by an elliptical shadow. is the direction of blade rotation, along which The direction gives the angle at which the Schematic diagram of the blade. From the geometric relationship shown in the figure, it can be seen that when the blade at zero phase is around Axis rotation After the angle, the blade orientation will be consistent with the velocity vector in the propeller disk plane. At this time, the rotor control amount balance problem evolves into the flight speed , Flight speed, Propeller disc plane angle The balancing problem in the no sideslip state.

[0085] Figure 3 The diagram shows the velocity components in the rotor disc plane and the blade orientation. The rotor is a left-hand rotor, and the velocity components in the rotor disc plane are The angle between the axes is Assume that the flight speed is , the angle between the flight speed and the propeller disc plane in the hub coordinate system is , and under zero sideslip conditions, the rotor trim control amount is the total pitch , the lateral and longitudinal periodic pitch are and Then at the angle In this case, the periodic pitch variation in the trim state can be derived through the following relationship.

[0086] (1) For a left-hand rotor, Figure 3 As shown, it can be assumed that the rotor blade is rotated in the direction of rotation (clockwise) Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and At this time, the cyclic pitch variation of the rotor can be described as follows:

[0087] (5)

[0088] in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor;

[0089] From this, we can get the periodic pitch variation of the left-hand rotor as:

[0090] (6)

[0091] (2) For a right-hand rotor, it can be assumed that the rotor blades are rotated in the opposite direction of rotation (clockwise). Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and At this time, the cyclic pitch variation of the rotor can be described as follows:

[0092] (7)

[0093] in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor;

[0094] From this, we can get the periodic pitch variation of the right-hand rotor as:

[0095] (8)

[0096] A method for converting trim control from no sideslip to sideslip is proposed. By combining equations (1), (2) and (4), the calculation method is given by , Sideslip Angle , rotor shaft inclination Under this premise, the angle between the flight speed and the propeller disc plane can be obtained , and the disc plane component of the flight speed and the hub coordinate system Axis Angle , the expression is as follows.

[0097] (9)

[0098] Therefore, under the premise that the flight speed and the angle between the rotor disc plane and the rotor blade are equal, if the trim control amount of the rotor in the non-sideslip state is known, the trim control amount in the sideslip state can be directly calculated by formula (6) (applicable to left-hand rotors) or formula (8) (applicable to right-hand rotors), where formula (6) is for left-hand rotors and formula (8) is for right-hand rotors.

[0099] A method for converting the trim control amount from a left-hand rotor to a right-hand rotor is proposed. By combining equations (6) and (8), the conversion formula from a left-hand rotor to a right-hand rotor can be obtained as follows:

[0100] (10)

[0101] The conversion formula from right-hand rotor to left-hand rotor is:

[0102] (11)

[0103] A calculation strategy for the trim control amount of the tilt-rotor in all states is proposed. According to the method in this paper, the calculation of the trim control amount of the tilt-rotor in all states (including different flight speeds, angles of attack, sideslip angles, rotor shaft inclination angles, left / right rotation directions) can be converted into flight speed. Angle with propeller disc plane Therefore, in the full state calculation, the change matrix of the trim control amount can be constructed first Then, any combination of flight and shaft inclination can be converted into the hub coordinate system State, in the known control variable change matrix Interpolation to get the current state The amount of manipulation , through the theoretical formulas (4) and (8), we can get the left-hand or right-hand rotor The trim control amount under the state. is the manipulated variable change matrix, is the flight speed in the current state, is the angle between the flight speed and the propeller disc plane in the current state, The current flight speed is parallel to the propeller disc plane component and the hub coordinate axis Angle.

[0104] For ease of understanding, the present invention provides a more specific embodiment:

[0105] (1) First, calculate the angle between the flight speed and the propeller plane , and the flight speed parallel to the disc plane component and the hub coordinate system Axis Angle Table 1 takes the angle of attack α=2° and the sideslip angle β=15° as an example to calculate the angle of attack of the hub coordinate system at different tilt angles. and sideslip angle , and the angle between the flight speed and the propeller plane , and the disc plane component of the flight speed and the hub coordinate system Axis Angle . Pay attention here and , and has different meanings, among which and The meaning of can be understood as follows: in order to rotate the flight velocity vector around the rotor axis to the longitudinal symmetry plane of the rotor, the angle required to rotate is , after turning this angle, the velocity vector and the hub plane The angle is .

[0106] Table 1 Calculation results of flight speed and hub plane angle

[0107]

[0108] Note: tilt-nacelle inclination angle, the forward inclination angle with the rotor axis The relationship is =90-tilt.

[0109] (2) Angle and The relationship between the trim control amount between the flight without sideslip and the flight with sideslip is established (see formulas (6) and (8)), and the relationship between the trim control amount between the left-hand rotor and the right-hand rotor on the same aircraft is also established (see formulas (10) and (11)). To obtain the trim control amount of the rotor, it is necessary to select one of the three states of no sideslip, left-hand rotor with sideslip, or right-hand rotor with sideslip to perform CFD trim calculations to obtain the rotor collective pitch and cyclic pitch control amount. Here, , Angle of Attack , Sideslip Angle , a left-hand rotor was used as an example to perform trim calculations. The calculation results are shown in Figure 4 As shown, from Figure 4 It can be seen that the 1st and 2nd circles are the initial flow field calculations of the rotor under the predetermined control amount, the 3rd to 5th circles are the calculations of the rotor balancing Jacobian matrix by the method of perturbation control amount, and the rotor balancing process begins from the 6th circle. After entering the 8th circle, the rotor thrust and roll / pitch moment values ​​reach the target values, and the entire balancing process ends.

[0110] (3) After obtaining the trim control amount of the left-rotating rotor with sideslip, the trim control amount under the condition of no sideslip can be calculated by formula (6), and the trim control amount of the right-rotating rotor with sideslip can be calculated by formula (10). Figure 5 The comparison of the periodic distance curves under three conditions is shown. Figure 5 It can be seen that the amplitudes of the periodic pitch changes in the three states are equal, and there is only a phase difference between them. Taking the no sideslip state as the benchmark, in the case of right-side slip, the phase of the right-hand rotor is advanced, and the phase of the left-hand rotor is delayed.

[0111] (4) In order to further verify the effectiveness of the method of the present invention, , Angle of Attack , Sideslip Angle , Flight speed Within the state range, CFD trim was performed on the left-hand rotor and the right-hand rotor. The trim control value of the right-hand rotor was used as input, and the trim control value of the left-hand rotor was calculated using the theoretical formula of the present invention. The trim control value was compared with the CFD trim value of the left-hand rotor. The comparison results are shown in FIG. Figure 6 and Figure 7 As shown. Figure 6 The horizontal periodic pitch is shown value, Figure 7 The longitudinal cyclic pitch is shown. The diagram covers a wide range of flight speed and sideslip angle. It can be seen from the figure that the rotor trim control value converted by the theoretical formula is completely consistent with the CFD trim result, which fully demonstrates that the theoretical method of the present invention is valid and the result is correct, and it has important application and promotion value.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating the trim control amount of a tiltrotor under sideslip, characterized in that: include: Step 1: Establish the relationship between the trim control amount between the no-skid and sideslip flight states; Step 2: Establish the relationship between the trim control variables between the left-hand rotor and the right-hand rotor on the same aircraft; Step 3: Convert the trim control amount calculation of the tilt rotor at different nacelle inclination angles, different rotor rotation directions, different flight speeds, and different angles of attack and sideslip into the trim control amount calculation that only includes the flight speed and the angle between the flight speed vector and the rotor disc plane; The step 2 comprises: The conversion formula from left-hand rotor to right-hand rotor is: (10) in, is the lateral cyclic pitch variation of the left-hand rotor, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor, is the velocity component parallel to the propeller disc plane and the hub coordinate axis The angle of is the longitudinal cyclic pitch variation of the left-hand rotor; The conversion formula from right-hand rotor to left-hand rotor is: （11） The step 3 comprises: In the full state calculation, first construct the change matrix of the trim control amount Any combination of flight speed and shaft inclination angle is converted into the hub coordinate system State, in the known control variable change matrix Interpolation to get the current state The amount of manipulation , get the left or right rotor in The trim control amount under the state; is the total distance, and are the lateral and longitudinal periodic pitch variations, is the manipulated variable change matrix, is the flight speed, is the angle between the flight speed and the propeller plane, is the flight speed in the current state, is the angle between the flight speed and the propeller disc plane in the current state, The current flight speed is parallel to the propeller disc plane component and the hub coordinate axis The full state includes different flight speeds, angle of attack, sideslip angle, rotor shaft inclination angle, and left / right rotation direction.

2. The method according to claim 1, characterized in that The step 1 comprises: Step 11: First calculate the flight speed vector in the hub coordinate system The velocity component of the flight speed is parallel to the propeller plane. The velocity component of the propeller and the velocity component perpendicular to the propeller disc plane are then used to calculate the angle between the flight speed and the propeller disc plane in the hub coordinate system. And the velocity component parallel to the propeller disc plane and the hub coordinate axis Angle ; Step 12: Move the blade at zero phase around the hub axis Rotation Angle, the blade pointing and the flight speed parallel to the propeller plane component Similarly, the rotor control amount balance problem is converted into a flight speed of , the angle between the flight speed and the propeller plane is The balancing problem in the no-sideslip state; Step 13: Calculate the cyclic pitch of the left-rotating rotor without sideslip and the right-rotating rotor without sideslip. By converting the trim control amount from the no-sideslip state to the sideslip state, the cyclic pitch of the left-rotating rotor with sideslip and the right-rotating rotor with sideslip can be obtained.

3. The method according to claim 2, characterized in that In the body coordinate system, the origin of the coordinate is the center of mass of the aircraft, the X axis is along the axis of the fuselage, the Z axis is located in the longitudinal symmetry plane, perpendicular to the OX axis, and is positive upwards; the Y axis is perpendicular to the longitudinal symmetry plane and is positive to the right; the hub coordinate system The origin is located at the center of the rotor, and the orientation is tilted around the Y axis by the body coordinate system The angle is obtained, is the forward tilt angle of the rotor shaft.

4. The method according to claim 3, characterized in that The step 11 comprises: The flight speed is known to be V, and the angle of attack is and sideslip angle , get the velocity components in three directions in the body coordinate system , , ; The relationship between the body coordinate system and the velocity vector is expressed by the angle of attack and sideslip angle express; According to the velocity components in three directions in the body coordinate system, the velocity components of the velocity vector in the hub coordinate system are obtained; According to the velocity component of the velocity vector in the hub coordinate system, calculate the and .

5. The method according to claim 4, characterized in that The velocity components in the three directions in the body coordinate system are: (1) in, , , They are the velocity components of the flight speed V on the X-axis, Y-axis and Z-axis in the body coordinate system; The velocity component of the flight speed in the hub coordinate system is: (2) in, , , They are V in the hub coordinate system Next axis, axis, Velocity components of the axis; Calculate the hub coordinate system and : (4)。 6. The method according to claim 2, characterized in that In step 13, calculating the cyclic pitch change in the left-hand rotor state without sideslip includes: For a left-hand rotor, the flight speed is known to be , hub coordinate system , and under zero sideslip conditions, the rotor trim control amount is the total pitch , the lateral and longitudinal periodic pitch are and , then at the angle In this case, the periodic pitch variation in the trim state is derived through the following relationship: Rotate the rotor blade in the direction of rotation Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and ; At this time, the cyclic pitch variation of the rotor is described as: (5) in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor; The cyclic pitch variation of the left-hand rotor is obtained as: (6)。 7. The method according to claim 6, characterized in that In step 13, calculating the cyclic pitch variation in the right-hand rotor state without sideslip includes: For a right-hand rotor, the flight speed is known to be , hub coordinate system , and under zero sideslip conditions, the rotor trim control amount is the total pitch , the lateral and longitudinal periodic pitch are and , then at the angle In this case, the periodic pitch variation in the trim state is derived through the following relationship: For right-hand rotors, rotate the rotor disc in the opposite direction of rotation. Angle, at this time the new blade azimuth satisfies ,lie in The blade in the azimuth position is facing the plane component of the rotor disc at the flight speed. The rotor is in a non-sideslip state, and the trim control amount is , and , the cyclic pitch variation of the rotor is described as: (7) in, is the periodic torque of the rotor, is the new blade azimuth, is the blade azimuth before the rotor disc rotates, is the lateral cyclic pitch variation of the left-hand rotor, is the longitudinal cyclic pitch variation of the left-hand rotor; The cyclic pitch variation of the right-hand rotor is obtained as follows: (8)。 8. The method according to claim 7, characterized in that In step 13, the cyclic pitch change in the left-hand rotor with sideslip and the right-hand rotor with sideslip is obtained by converting the trim control amount from the non-sideslip state to the sideslip state, including: At a known angle of attack , Sideslip Angle , Cyclic torque variation of the rotor Under this premise, the angle between the flight speed and the propeller disc plane is obtained , and the flight speed component parallel to the disc plane and the hub coordinate system Axis angle , the expression is: (9) Therefore, under the premise that the flight speed and the angle between the rotor disc plane and the rotor blade are equal, if the trim control amount of the rotor in the non-sideslip state is known, the trim control amount in the sideslip state can be directly calculated by formula (6) or formula (8).

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