High-speed helicopter rotor feathering-folding mechanism and multi-mode control method thereof

Abstract

The invention discloses a high-speed helicopter rotor feathering-folding mechanism and a multi-mode control method thereof.The high-speed helicopter rotor feathering-folding mechanism comprises a main shaft, a center propeller hub piece, a driving part, a variable-pitch propeller hub and propeller blades, the propeller pitch between the variable-pitch propeller hub and the center propeller hub piece is fixed through a propeller pitch locking assembly, the driving part drives the variable-pitch propeller hub to rotate through a variable-pitch assembly, and the variable-pitch propeller hub is driven to rotate through the variable-pitch assembly; a folding assembly is further connected between the propeller blades and the variable-pitch propeller hub, a folding locking assembly is arranged, and the folding assembly is fixedly connected with the variable-pitch assembly. When the propeller pitch locking assembly is unlocked and the folding locking assembly is locked, the driving part drives the variable-pitch propeller hub to rotate through the variable-pitch assembly so as to realize variable pitch of the propeller blades; and when the propeller pitch locking assembly is locked and the folding locking assembly is unlocked, the driving part drives the folding assembly through the variable pitch assembly, and the folding assembly drives the propeller blades to be folded. A dual-mode independent locking mechanism is added, through the layered layout of a propeller pitch locking mechanism and a folding locking mechanism, physical decoupling of the propeller pitch adjusting function and the rotor wing folding function is achieved, and the helicopter rotor wing folding difficulty is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft technology, in particular to a high-speed helicopter rotor feathering-folding mechanism and a multi-modal control method thereof. BACKGROUND

[0002] In the prior art, although the traditional rotorcraft has the functions of vertical take-off and landing and hovering, it faces technical bottlenecks such as low propulsion efficiency and limited range in the cruising stage. In contrast, the fixed-wing aircraft has the advantages of high aerodynamic efficiency, fast cruising speed and long range, but it relies on long-distance landing runways and has poor terrain adaptability, which makes it difficult to meet the rapid deployment requirements in complex combat environments. In order to solve the contradiction between the landing environment adaptability, cruising efficiency and task load of the traditional aircraft, a new technical path-high-speed helicopter has emerged. The high-speed helicopter is a new type of aircraft that combines the vertical take-off and landing capability of the rotorcraft with the high-speed cruising advantage of the fixed-wing aircraft. The core design goal is to provide lift in the vertical take-off and landing stage and reduce drag in the cruising stage through dynamic switching of the rotor system working mode and through the separation of the lift generation mechanism (rotor system) and the propulsion system (fixed wing + propeller), thereby breaking through the speed limit (usually below 300 km / h) of the traditional helicopter and achieving high-efficiency cruising above 400 km / h.

[0003] However, in the prior art, the helicopter rotor system rotor folding is difficult during the transition from the helicopter mode to the fixed-wing mode, and the mechanical structure is complex. In addition, the air resistance of the high-speed helicopter in the fixed-wing mode is large. SUMMARY

[0004] The present application provides a high-speed helicopter rotor feathering-folding mechanism and a multi-modal control method thereof, which can reduce the difficulty of helicopter rotor folding.

[0005] Technical Solution: To solve the above problems, the present invention employs a high-speed helicopter rotor feathering-folding mechanism, including a main shaft assembly and a blade assembly. The main shaft assembly includes a main shaft, a central rotor hub fixedly sleeved on the upper end of the main shaft, and a drive unit. At least three sets of blade assemblies are evenly arranged circumferentially on the central rotor hub. Each blade assembly includes a variable-pitch hub and blades hinged to the variable-pitch hub. The variable-pitch hub rotates relative to the central rotor hub to change the blade pitch, and the pitch is fixed by a pitch locking assembly. The variable-pitch hub is connected to the central rotor hub via the variable-pitch assembly. The drive unit is connected and drives the variable pitch hub to rotate through the variable pitch assembly. A folding assembly is also connected between the blade and the variable pitch hub. The folding assembly is fixedly connected to the variable pitch assembly, and a folding locking assembly is provided between the folding assembly and the variable pitch hub. When the pitch locking assembly is unlocked and the folding locking assembly is locked, the drive unit drives the variable pitch hub to rotate relative to the central hub component through the variable pitch assembly to achieve blade pitch adjustment. When the pitch locking assembly is locked and the folding locking assembly is unlocked, the drive unit drives the folding assembly through the variable pitch assembly, and the folding assembly drives the blade to fold.

[0006] Furthermore, the drive unit includes an actuator, a stationary swashplate ring sleeved on the main shaft, a moving swashplate ring, a main ball joint, and a main shaft mounting seat. The main ball joint is coaxially mounted on the main shaft. The stationary swashplate ring and the moving swashplate ring are sequentially hinged from bottom to top on the outer edge of the main ball joint. The main shaft mounting seat is fixedly sleeved on the main shaft and connected to the moving swashplate ring via a torque arm assembly. The output end of the actuator is hinged to the stationary swashplate ring. The actuator drives the stationary swashplate ring to slide up and down along the main shaft, thereby driving the main ball joint and the moving swashplate ring to slide up and down along the main shaft. The rotation of the main shaft drives the main shaft mounting seat to rotate. The main shaft mounting seat drives the moving swashplate ring to rotate via the torque arm assembly. The pitch control assembly is connected to the moving swashplate ring.

[0007] Furthermore, the pitch control assembly includes a pitch control link and a pitch control arm. One end of the pitch control link is hinged to the outside of the tilting disc moving ring, and the other end of the pitch control link is hinged to one end of the pitch control arm. The other end of the pitch control arm is hinged to the pitch control hub and fixedly connected to a folding assembly. A folding locking assembly is provided at the hinged part between the pitch control arm and the pitch control hub.

[0008] Furthermore, the folding assembly includes a folding crank and a folding connecting rod. One end of the folding crank is fixedly connected to the variable pitch arm, and the other end is hinged to one end of the folding connecting rod. The other end of the folding connecting rod is hinged to the blade.

[0009] Furthermore, the pitch locking assembly includes a drive motor fixedly mounted on the extension shaft of the central rotor hub, a main gear disposed at the output end of the drive motor, a transition gear meshing with the main gear, two output gears meshing with the transition gear, an Archimedean spiral cam fixedly connected coaxially to the output gears, and a locking connecting disk. The locking connecting disk is fixedly mounted on the extension shaft of the variable pitch rotor hub. The two Archimedean spiral cams are symmetrically disposed on both sides inside the locking connecting disk. The drive motor drives the main gear to rotate, and the main gear drives the two output gears to rotate through the transition gear. The two output gears respectively drive the two Archimedean spiral cams to rotate. The profile curve of the Archimedean spiral cam generates radial displacement during rotation, and friction locking is achieved by synchronously pressing the inner side of the locking connecting disk.

[0010] Furthermore, the folding locking assembly includes a locking connecting shaft fixedly connected between the pitch control arm and the folding crank, a drive motor, a main gear disposed at the output end of the drive motor, a transition gear meshing with the main gear, two output gears meshing with the transition gear, an Archimedean spiral cam fixedly connected coaxially with the output gears, and a locking mechanism housing. The locking mechanism housing is fixedly installed on the side of the pitch control hub. The two Archimedean spiral cams are symmetrically disposed on both sides of the locking connecting shaft. The drive motor drives the main gear to rotate, and the main gear drives the two output gears to rotate through the transition gears. The two output gears respectively drive the two Archimedean spiral cams to rotate. The profile curve of the Archimedean spiral cam generates radial displacement during rotation, and friction locking is achieved by synchronously pressing the side of the locking connecting shaft.

[0011] This invention also employs a multimodal control method for the aforementioned high-speed helicopter rotor feathering-folding mechanism. When the high-speed helicopter triggers a folding command, the pitch locking component unlocks and the folding locking component locks, controlling the engine driving the main shaft to idle. When the speed is low, and the speed reaches a predetermined range, the aerodynamic load is predicted through a fluid-structure interaction model, and the actuator control quantity is optimized by the Tube-MPC controller, driving the actuator to smoothly adjust the blade pitch. After adjusting the blade pitch to the feathering position, the pitch locking component is switched to the locked state and the folding locking component is switched to the unlocked state. The actuator drives the blade to complete the folding action, and the folding locking component is switched to the locked state, keeping the rotor locked in the feathering-folding state, thus completing the entire feathering-folding variant process.

[0012] When the high-speed helicopter triggers the rotor deployment command, it switches the folding locking assembly to the released state, and the actuator drives the blades to fully deploy. It then switches the folding locking assembly to the locked state and the pitch locking assembly to the released state. The actuator continuously adjusts the blade pitch to adapt to changes in wind resistance. Once the blade pitch is adjusted to a suitable state, the engine is started.

[0013] Furthermore, the state vector of the Tube-MPC controller is:

[0014]

[0015] Among them, a f The fluid modal coefficients q and q are the values ​​of the reduced-order fluid-structure interaction model. Here are the modal coordinates and their derivatives for the reduced-order model, and θ is the propeller pitch angle. The derivative of the pitch angle. For the folding angle, The derivative of the fold angle;

[0016] The prediction model equation for the Tube-MPC controller is:

[0017] x k+1 =A(ρ k )x k +B(ρ k )u k +d k

[0018] Where, x k+1 x is the control variable at time k+1. k Let A(ρ) be the control variable at time k. k B(ρ) is the time-varying system matrix, which depends on the real-time aerodynamic parameters of the fluid-structure interaction model; k ) represents the time-varying control matrix, generated from the actuator dynamics model; d k For the disturbance term, u k This represents the control input vector at discrete time step k;

[0019] The objective function of the Tube-MPC controller is:

[0020]

[0021] Where Q, R, and P are all MPC weight matrices, x ref For reference trajectory;

[0022] The dynamic management domain of the Tube-MPC controller is:

[0023]

[0024] Where γ is the safety factor. For aerodynamic load gradient; σ m σ represents the residual variance of the reduced-order model and the full-order model. noise Let d represent the sensor noise variance, and d represent the total disturbance experienced by the system during operation.

[0025] Furthermore, when the actuator drives the blades to fold, the Tube-MPC controller optimizes the actuator control input to smoothly fold the blades. The actuator is driven by constraints of a segmented speed strategy, specifically a three-segmented speed strategy, as follows:

[0026] The range of folding angles is At that time, it was in the low-speed phase, and the folding angular velocity was The range of folding angles is At that time, it was in the high-speed phase, and the folding angular velocity was Fluid-structure interaction prediction is performed; the folding angle range is... At that time, during the fine-tuning stage, the folding angular velocity was... Constraint angle error

[0027] Beneficial effects: Compared with the prior art, the significant advantages of this invention are:

[0028] (1) This invention incorporates a dual-mode independent locking mechanism. By setting a pitch locking mechanism inside the rotor hub and a folding locking mechanism on the outside, the physical decoupling of pitch adjustment and rotor folding functions is achieved. Compared with the traditional single locking mechanism scheme, this design ensures that the periodic pitch-changing motion in helicopter mode and the rotor folding action in fixed-wing mode do not interfere with each other, solving the problem of motion interference between the pitch-changing mechanism and the folding mechanism in the prior art, and significantly improving the system reliability.

[0029] (2) The present invention adopts a progressive conversion logic of helicopter mode - transition mode - fixed wing mode. In the transition mode, the rotor stops and the pitch feathering is controlled in coordination to effectively reduce rotor aerodynamic drag. In the fixed wing mode, the feathering angle is fixed with an accuracy of ±0.5° through an internal locking mechanism. The aerodynamic shape is optimized in conjunction with the folding mechanism. After folding, the folding state is locked by the folding locking mechanism. Compared with the sudden conversion scheme, it effectively avoids the risk of aerodynamic sudden change during mode switching and improves flight stability.

[0030] (3) The present invention adopts a multi-link folding mechanism. The folding and unfolding of the linkage mechanism is achieved by driving the inner ring of the main shaft to move up and down through the actuator. The drive module (actuator) is installed in the lower casing part, which effectively coordinates the motion relationship between the rotor and the stator and improves the stability of the rotor system.

[0031] (4) This invention employs an intelligent actuator with three stroke levels, achieving the multi-modal stroke requirements of the rotor with only one actuator. In helicopter mode, the actuator's ±X mm stroke enables collective / cyclic pitch control; in transition mode, the actuator moves down Y mm to complete feathering positioning; and in fixed-wing mode, the actuator moves up Z mm to drive the folding mechanism to complete the folding action. Compared to traditional multi-actuator solutions, this effectively reduces system weight.

[0032] (5) The present invention adopts a multi-stage collaborative control method for a high-speed helicopter rotor feathering-folding mechanism based on a fluid-structure interaction dynamics model and Tube-MPC. Tube-MPC resists uncertainty through dynamic domain, effectively improving the robustness of the system. Through dynamic adjustment and model update, the control strategy is continuously optimized to improve the system's adaptability. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the rotor feathering-folding mechanism in this invention;

[0034] Figure 2 This is a schematic diagram of the overall structure of the upper part of the rotor feathering-folding mechanism without a fairing in this invention;

[0035] Figure 3 This is a schematic diagram of the variable pitch locking assembly VI in this invention;

[0036] Figure 4 This is an exploded view of the structure of the pitch locking assembly VI in this invention;

[0037] Figure 5 This is a schematic diagram of the release and holding (locking) state of the pitch locking component VI in this invention;

[0038] Figure 6 This is a partial structural diagram of the folding locking assembly VII in this invention;

[0039] Figure 7 This is a schematic diagram of the release and holding (locking) states of the folding locking component VII in this invention;

[0040] Figure 8 This is a schematic diagram of the internal structure of the feathering-folding mechanism in the present invention during the feathering process; Figure 8 (a) in the diagram is a state diagram of the rotor collective pitch adjustment process. Figure 8 (b) in the diagram represents the rotor feathering state.

[0041] Figure 9 This is a schematic diagram of the internal structure of the folding mechanism in the present invention during the folding process; Figure 9 (a) in the diagram is a schematic of the rotor in its initial folded state; Figure 9 (b) in the diagram is a schematic of the rotor in a fully folded state;

[0042] Figure 10 This is a diagram illustrating the control strategy of the Tube-MPC and fluid-structure interaction model-based collaborative control method in this invention.

[0043] Figure 11 This is a flowchart illustrating the mode transition process of the rotor feathering-folding mechanism in this invention.

[0044] Figure 12 This is a rotor mode transition diagram in this invention; Figure 12 (a) in the image represents the rotor deployment / stopping state; Figure 12 (b) in the diagram represents the rotor feathering state; Figure 12 (c) in the figure represents the rotor folded state. Detailed Implementation

[0045] like Figure 1 , 2 As shown, this embodiment of a high-speed helicopter rotor feathering-folding mechanism includes a housing 1, an actuator 2, a push rod 3, a sensor mounting bracket 4, a speed sensor 5, a nose fairing 6, a main shaft assembly I, a blade assembly II, a pitch control assembly III, a folding assembly IV, a torque arm assembly V, a pitch control locking assembly VI, and a folding locking assembly VII. The main shaft assembly I and the actuator 2 are fixedly connected to the housing 1. The main shaft assembly I is used to drive the rotor to rotate. The sensor mounting bracket 4 and the speed sensor 5 are fixedly mounted on the housing 1 to detect the rotor speed. The actuator 2 is connected to the main shaft assembly I through the push rod 3 to increase the driving force of the main shaft assembly I. The nose fairing 6 is fixedly mounted on the upper end of the main shaft assembly I. At least three sets of blade assemblies II are evenly installed circumferentially on the main shaft assembly I. In this embodiment and the accompanying drawings, three sets of blade assemblies II are used as an example. At least three sets of pitch-changing assemblies III and two sets of torque arm assemblies V are installed on the main shaft assembly I. Pitch-changing assemblies III connect the main shaft assembly I and the blade assembly II. Torque arm assemblies V are used to transmit the rotational force of the main shaft assembly I. Folding assembly IV is installed on the outside of the blade assembly II and is used for folding the blades. Pitch-changing assemblies III are connected to blade assembly II and folding assembly IV. Pitch-changing locking assembly VI and folding locking assembly VII are fixedly installed inside and outside the blade assembly II, respectively. Pitch-changing locking assembly VI acts between the main shaft assembly I and the blade assembly II, and folding locking assembly VII acts between the blade assembly II and the folding assembly IV.

[0046] like Figure 2As shown, the main shaft assembly I includes a main shaft 11, a swashplate stationary ring 12, a swashplate moving ring 13, a main ball joint 14, a fairing lower support 15, a main shaft rotor seat 16, a center rotor hub 17, and a fairing upper support 18. The main shaft 11 is coaxially mounted with the main ball joint 14. The outer edge of the main ball joint 14 is sequentially hinged with the swashplate stationary ring 12 and the swashplate moving ring 13 from bottom to top. The main ball joint 14, the swashplate stationary ring 12, and the swashplate moving ring 13 can slide up and down along the main shaft 11. The swashplate stationary ring 12 can tilt around the main ball joint 14. Correspondingly, the swashplate moving ring 13 completes the tilting action under the drive of the swashplate stationary ring 12. The tilting of the swashplate causes the rotor pitch to change periodically when the blades rotate to different azimuth angles, thereby changing the direction distribution of the rotor lift. When the swashplate tilts in a specific direction, the rotor lift vector shifts accordingly, generating a torque that causes the fuselage to rotate around the center of gravity (e.g., tilting the swashplate to the left → the helicopter rolls to the left). The main shaft mount 16 and the center propeller hub 17 are installed between the lower fairing support 15 and the upper fairing support 18, and the main shaft mount 16 and the center propeller hub 17 are fixedly installed on the main shaft 11. The head fairing 6 is fixedly installed through the lower fairing support 15 and the upper fairing support 18 and rotates synchronously with the main shaft 11. The main shaft mount 16 drives the tilting disc ring 13 to rotate through at least two sets of torque arm assemblies V.

[0047] The torque arm assembly V includes a connecting arm 51, a rotating arm 52, and a spherical bearing connecting rod 53. One end of the connecting arm 51 is hinged to the outer side of the main shaft rotating seat 16, and the other end of the connecting arm 51 is hinged to one end of the rotating arm 52. The rotating arm 52 is threadedly connected to the spherical bearing connecting rod 53. One end of the spherical bearing connecting rod 53 is hinged to the outer ball joint of the tilting disc moving ring 13. When the main shaft 11 drives the main shaft rotating seat 16 to rotate, the torque arm assembly V drives the tilting disc moving ring 13 to rotate synchronously.

[0048] The blade assembly II includes blades 21, blade connectors 22, variable pitch hubs 23, and folding hinge pins 24. The variable pitch hubs 23 are axially mounted on the extension shaft of the central hub 17. The variable pitch hubs 23 can rotate around the extension shaft of the central hub 17 to achieve rotor pitch variation. The blade connectors 22 are hinged to one end of the variable pitch hubs 23 via the folding hinge pins 24. The blades 21 are fixedly mounted on the blade connectors 22. The blade connectors 22 can rotate around the folding hinge pins 24 and simultaneously drive the blades 21 to rotate synchronously to achieve blade folding or unfolding.

[0049] The pitch control assembly III includes a pitch control link 31, a pitch control arm 32, and a fixed hinge pin 33. One end of the pitch control link 31 is hinged to the outer ball joint of the tilting disc moving ring 13, and the other end of the pitch control link 31 is hinged to one end of the transversely arranged pitch control arm 32. The other end of the pitch control arm 32 is hinged to the pitch control hub 23 through the fixed hinge pin 33.

[0050] Folding assembly IV is installed outside blade assembly II. Folding assembly IV includes folding crank 41, folding ball joint 42, connecting rod hinge pin 43, folding connecting rod 44, lug connector 45, and blade hinge pin 46. One end of folding crank 41 is hinged to fixed hinge pin 33. Folding crank 41 and pitch control arm 32 are fixedly connected to locking connecting shaft 87 inside folding locking assembly VII. Folding crank 41 and pitch control arm 32 can rotate synchronously around fixed hinge pin 33. The other end of folding crank 41 is hinged to folding ball joint 42. Folding ball joint 42 and connecting rod hinge pin 43 are fixedly installed at one end of folding connecting rod 44. The other end of folding connecting rod 44 is hinged to lug connector 45 at the lug of blade connector 22 through blade hinge pin 46.

[0051] like Figures 2 to 4As shown, at least three sets of pitch locking assemblies VI are installed on the center rotor hub 17. The pitch locking assemblies VI are located between the center rotor hub 17 and the blade assembly II. The pitch locking assemblies VI include an axial fixing member 61, a front connecting pin 62, a drive motor 63, a gear bearing housing 64, a bearing flange 65, a main gear bracket 66, a main gear bearing sleeve 67, a transition gear bracket 68, a main gear 69, a transition gear 70, an output gear 71, a transition gear shaft 72, an output gear shaft 73, a transition gear sleeve 74, a cam connector 75, an Archimedean spiral cam 76, a main gear sleeve 77, a main gear shaft 78, a middle connecting pin 79, a gear train bracket 80, an axial fixing member 81, a tail connecting pin 82, and a camshaft. The components include bracket 83, locking connecting disc 84, locking nut 85, and locking mechanism housing 86; axial fixing member 61 is fixedly installed on the protruding shaft of the center propeller hub 17, and is fixedly connected to the locking mechanism housing 86; main gear bracket 66, transition gear bracket 68, gear train bracket 80, and camshaft bracket 83 are fixedly installed inside the locking mechanism housing 86; the protruding shaft of the center propeller hub 17 passes through the above-mentioned parts in sequence; the main gear bracket 66 and transition gear bracket 68 are connected by a front connecting pin 62; the main gear bracket 66 and gear train bracket 80 are connected by a middle connecting pin 79; the gear train bracket 80 is fixedly connected to the camshaft bracket 83 by a tail connecting pin 82; and the drive motor 63 is connected by a gear bearing seat 67. The main gear shaft 78 is fixedly installed on the main gear bracket 66 and is fixedly connected to the output end of the drive motor 63. The bearing flange 65, main gear bearing sleeve 67, main gear 69, main gear sleeve 77, and axial fixing member 81 are axially fixedly installed on the main gear shaft 78 in sequence. The drive motor 63 drives the main gear 69 to rotate through the main gear shaft 78. One end of the transition gear shaft 72 is connected to the transition gear bracket 68, and the other end is connected to the gear system bracket 80. One end of the output gear shaft 73 is connected to the transition gear bracket 68, and the other end is connected to the gear system bracket 80. The transition gear 70 and transition gear sleeve 74 are axially installed on the transition gear shaft 72 in sequence. The output gear 71, cam connector 75, and Archimedes spiral cam 76 are axially installed in sequence. On the output gear shaft 73, the main gear 69, the intermediate gear 70, and the output gear 71 mesh sequentially. The rotation of the main gear 69 drives the output gear 71 to rotate through the intermediate gear 70, thereby driving the Archimedes spiral cam 76 to rotate. The locking connecting disk 84 is rotatably mounted on the extended shaft of the central rotor hub 17. The outside of the locking connecting disk 84 is circumferentially fixed to the inside of the variable pitch rotor hub 23 through splines. Two Archimedes spiral cams 76 are symmetrically arranged on both sides inside the locking connecting disk 84. The two cams are driven to rotate by the output gear shaft 73. Their contour curves generate radial displacement when rotating. Friction locking is achieved by synchronously pressing the inner side of the locking connecting disk 84. The locking nut 85 axially fixes the pitch locking assembly VI and the blade assembly II.

[0052] like Figures 3 to 5As shown, the working principle of the pitch locking assembly VI is as follows: The drive motor 63 of the pitch locking assembly VI provides power to drive the main gear shaft 78 to drive the main gear 69 to rotate. Through gear transmission, the transition gears 70 and output gears 71, which are symmetrically arranged on both sides, rotate in the same direction, thereby driving the Archimedean spiral cams 76 connected to the output gear shaft 73 to rotate in the same direction. The two Archimedean spiral cams with opposite directions of rotation (left-handed and right-handed) are symmetrically arranged on both sides inside the locking connecting disk 84. The two cams rotate in the same direction around the output gear shafts 73 on both sides respectively. Their contour curves generate radial displacement when rotating. Friction locking is achieved by synchronously pressing the end faces of the locking connecting disk 84 on both sides. The outside of the locking connecting disk 84 is fixedly connected to the inside of the variable pitch hub 23 through splines, thereby locking the rotational degree of freedom of the variable pitch hub 23 around the extension shaft of the central hub component 17, and completing the pitch locking action. When it is necessary to release the pitch lock, simply control the drive motor 63 to rotate in the opposite direction, which will drive the Archimedes spiral cams 76 on both sides to rotate in the opposite direction through gear transmission, thus releasing the pitch lock.

[0053] like Figure 6 , 7 As shown, the folding locking assembly VII includes all the parts of the aforementioned pitch locking assembly VI except for the axial fixing member 61 and the locking connecting disc 84, and also includes a locking connecting shaft 87; the folding locking assembly VII is fixedly installed on the outside of the variable pitch hub 23 through the locking mechanism housing 86, the locking connecting shaft 87 passes through the locking mechanism housing 86, one end is fixedly connected to the variable pitch arm 32, and the other end is fixedly connected to the folding crank 41, the locking connecting shaft 87 rotates relative to the locking mechanism housing 86, and two Archimedean spiral cams 76 are symmetrically arranged on both sides of the locking connecting shaft 87. The working principle of the folding locking assembly VII is similar to that of the pitch locking assembly VI: the drive motor 63 provides power, and the two cams 76 rotate through the gear transmission mentioned above. Their contour curves generate radial displacement during rotation, and friction lock is achieved by synchronously pressing the two sides of the locking connecting shaft 87, thereby locking the rotational freedom of the variable pitch arm 32 and the folding crank 41 fixed to the locking connecting shaft 87 relative to the variable pitch hub 23, and thus locking the rotor folding mechanism IV, keeping the rotor in the unfolded state.

[0054] like Figure 8 , 9As shown, the working principle of the rotor feathering-folding mechanism is as follows: In helicopter mode, the pitch locking component VI is released, and the folding locking component VII is held. Actuator 2 drives actuator push rod 3 to move up and down, causing the swashplate stationary ring 12 and swashplate moving ring 13 to move up and down, thereby driving the pitch linkage 31 and pitch arm 32 to move, which in turn drives the pitch hub 23 to rotate around the extension shaft of the central hub component 17, realizing the periodic pitch change and collective pitch adjustment functions; In transition mode, actuator 2 drives actuator push rod 3 to move downward to the limit position, realizing the periodic pitch change and collective pitch adjustment functions. The propeller feathering function is now activated. After feathering is completed, the locking state is switched to the pitch locking component VI, and the folding locking component VII is released. The actuator 2 drives the actuator push rod 3 to move upward, which drives the pitch push rod 31 to move upward, thereby driving the pitch arm 32 and the folding crank 41 to rotate around the fixed hinge pin 33. The folding crank 41 drives the folding connecting rod 44 to move, which in turn drives the blade connector 22 and the blade 21 to rotate around the folding hinge pin 24, realizing the blade folding. When the actuator push rod 3 moves upward to the limit position, the blade folding action is completed.

[0055] like Figure 10 As shown, a high-speed helicopter rotor mode transition control strategy based on a fluid-structure interaction dynamics model and Tube-MPC in this invention is as follows: Based on a fluid-structure interaction reduced-order model and a robust predictive control framework, the Tube-MPC control process achieves safe rotor mode transitions through multi-modal cooperation. The Tube-MPC controller is used to control the transition from helicopter mode to transition mode and from transition mode to fixed-wing mode.

[0056] First, a fluid-structure interaction dynamic model is established. For the high-speed helicopter operating scenario, the fluid object is a three-dimensional compressible fluid. The governing equations for the fluid domain and the structural domain are established separately, and the following differential governing equations are used for description:

[0057] Fluid domain governing equations:

[0058] mass conservation equation:

[0059] Momentum conservation equation:

[0060]

[0061] Energy conservation equation:

[0062]

[0063] In the formula: ρ is the fluid density, and t is the time variable. Let u be the Laplace operator, p be the fluid pressure, f be the fluid body force vector, τ be the stress tensor, e be the fluid internal energy, and μ be the dynamic viscosity. / Here, I is the second dynamic viscosity, k is the unit tensor, and T is the absolute temperature. For thermal radiation, S is the deformation rate tensor, which is determined by the velocity component.

[0064] Domain governing equations:

[0065] Establish the generalized dynamic equations of the blade:

[0066] Where: M s C s K s These are the structural mass matrix, damping matrix, and stiffness matrix, respectively, τ s Let d be the stress vector acting on the structure, and d be the structural displacement.

[0067] The fluid-structure interaction model was modified using the immersed boundary method (IBM) to obtain the modified governing equations for the fluid domain and structural domain:

[0068] Modified domain governing equations:

[0069] mass conservation equation:

[0070] Momentum conservation equation: adding the immersion boundary force term f ibm This indicates the effect of a solid on a fluid.

[0071]

[0072] In the formula: f ibm It is a volume force calculated using IBM methods, used to represent the force exerted by a solid structure on a fluid.

[0073] Among them, f ibm The expression is:

[0074] In the formula: x represents the Eulerian coordinates in the fluid domain, i.e., the position coordinates fixed in space, used to describe the distribution of flow field variables (such as velocity and pressure) in the fluid domain. For example, in the momentum equation, u(x,t) represents the velocity of the fluid at spatial position x and time t; s represents the Lagrangian coordinates in the structural domain, i.e., the parameterized coordinates fixed on the structure (such as arc length parameters or node numbers). Γ is used to describe the position, displacement, or surface force density of the structure. For example, X(s,t) represents the spatial position of the structure at parameter s and time t; s Let F(s,t) be the surface force density, X(s,t) be the structural position, and δ be the Dirac delta function. The surface force F(s,t) of the structure is mapped from Lagrange coordinates s to Eulerian coordinates x onto the fluid mesh.

[0075] Energy conservation equation: Considering the effect of work done by the immersion boundary force on energy.

[0076]

[0077] Corrected structural domain dynamics equations: The equations of motion for the structure must include fluid force feedback.

[0078]

[0079] In the formula: F flu It is the reaction force of fluid forces on the structure, calculated by IBM:

[0080]

[0081] Among them, Ω f This represents the fluid domain, which includes the entire computational area of ​​the fluid.

[0082] Fluid-structure interaction condition: When thermal deformation of the structure is not considered, the coupling condition is as follows:

[0083] 1. Motion coupling: The structural displacement X(s,t) is transmitted to the fluid domain through interpolation, serving as the motion boundary condition of the immersion boundary.

[0084] 2. Force Coupling: Fluid forces are coupled through the IBM volume force term f. ibm It is embedded in the fluid equations and simultaneously reacts to the structural dynamics equations.

[0085] For the fluid-structure interaction model using the compressible flow infiltration boundary method, a hierarchical order reduction strategy is adopted to reduce the order of the fluid domain, structural domain, and coupling terms separately, ultimately constructing a coupled ROM:

[0086] For high-speed helicopter rotors, blades may undergo geometrically nonlinear deformation. High-speed flight leads to complex flow field phenomena such as shock waves and flow separation. Traditional linear modal superposition methods may not accurately capture the dynamic response. Introducing intrinsic orthogonal decomposition (POD) to reduce the order in the structural domain can more flexibly capture nonlinear dynamic characteristics, compensating for the shortcomings of traditional modal analysis. A nonlinear finite element analysis is performed, acquiring the structural displacement field time series d(t1), d(t2), ..., d(t... M ), construct a snapshot matrix in Let n be the average displacement, n be the structural degrees of freedom, and M be the number of time steps. Perform singular value decomposition on the snapshot matrix:

[0087]

[0088] In the formula, Left singular vector (spatial mode), Singular value matrix (characterizing modal energy), Right singular vector (time mode): k s : Retain the number of modes, retain the top k s Each POD mode satisfies the cumulative energy percentage: Where σ i It is a singular value.

[0089] The displacement field is approximated as a linear combination of POD modes:

[0090] Substituting into the structural domain dynamics equations:

[0091] The reduced-order equation is obtained by projection using the Galerkin method:

[0092] In the formula,

[0093] Similarly, POD order reduction is performed on the fluid domain, and the flow field velocity is collected at M time steps through full-order CFD simulation. Constructing the snapshot matrix: in For the average velocity, n f This represents the number of points in the fluid grid.

[0094]

[0095] The velocity field is approximated as a linear combination of POD modes: Keep the first k f One dominant POD mode

[0096] Substituting into the compressible Navier-Stokes equations, we obtain the following through Galerkin projection:

[0097]

[0098] Among them, A f For the fluid linear terms matrix, B f (a) is the fluid nonlinear term function. C f The fluid-structure interaction matrix, L is a linear operator, N is a nonlinear convection term, and G is a fluid-structure interaction term.

[0099] Coupling term definition:

[0100] 1. The effect of structure on fluid: structural displacement q s The immersion boundary conditions are updated by interpolating the data and transferring it to the fluid mesh.

[0101] 2. The effect of fluid on structure: fluid force Fflu =U f Da, where D is the force projection matrix.

[0102] The structural and fluid equations are combined to form a coupled system. A reduced-order ROM model is used to predict the Tube-MPC control. The state vector of the Tube-MPC controller is:

[0103]

[0104] Among them, a f The fluid modal coefficients q and q are the values ​​of the reduced-order fluid-structure interaction model. Here are the modal coordinates and their derivatives for the reduced-order model, and θ is the propeller pitch angle. The derivative of the pitch angle. For the folding angle, is the derivative of the fold angle.

[0105] The prediction model equation for the Tube-MPC controller is:

[0106] x k+1 =A(ρ k )x k +B(ρ k )u k +d k

[0107] Where, x k+1 x is the control variable at time k+1. k Let A(ρ) be the control variable at time k. k B(ρ) is the time-varying system matrix, which depends on the real-time aerodynamic parameters of the fluid-structure interaction model; k ) represents the time-varying control matrix, generated from the actuator dynamics model; d k For the disturbance term, u k U represents the control input vector at discrete time step k, in the rotor mode transition scenario. k The following key control variables are included: actuator displacement ΔZ k folding angular velocity Locking mechanism command.

[0108] When the helicopter mode triggers the folding command, the system first monitors the rotor speed in real time using a speed sensor and controls the engine to idle. After the speed drops to the point where the rotor stops, the blade pitch is adjusted to the feathering position, and the helicopter mode switches to the transition mode. The system predicts aerodynamic loads using a fluid-structure interaction model and optimizes actuator control using Tube-MPC to drive the actuators to smoothly adjust the collective pitch. The objective function for MPC optimization in this stage is:

[0109]

[0110] ΔF ae ≤15%

[0111]

[0112] Where ΔZ is the actuator displacement, Q and R are MPC weight matrices, and θ k Let ω be the propeller pitch angle at time k, and ω be the aerodynamic load gradient weight. Let k be the rate of change of aerodynamic load at time k, and N be the prediction time domain (usually taken as 10 to 20 steps); the constraint condition is: pitch angular rate constraint. Load fluctuation constraint ΔF ae ≤15%, Robust Pipeline Constraint

[0113] The robust pipe domain is:

[0114]

[0115] Where γ is the safety factor. The aerodynamic load gradient is predicted in real time by a reduced-order fluid-structure interaction model; σ m σ represents the residual variance of the reduced-order model and the full-order model. noise For the sensor noise variance, F ae Let d be the aerodynamic load vector (derived from the integral of pressure and viscous stress from the fluid domain), and let d represent the total disturbance experienced by the system during operation. In the state-space prediction model equations, d... k Updated in real time by the dynamic control domain. In the rotor mode transition control scenario, d k These include: model mismatch error, external environmental disturbance, and sensor noise, which correspond to the three variables in the pipeline formula.

[0116] After adjusting the pitch to the feathering position, the system switches the pitch locking mechanism to the locked state and the folding locking mechanism to the released state, adjusts the blade folding, and transitions from the transition mode to the fixed-wing mode. MPC is set to the objective function.

[0117]

[0118] ||τ ae,k ||≤τ max

[0119]

[0120] The folding process is optimized and controlled, among which, The current folding angle, The folding angular velocity, For the friction torque model related to folding, λ is the penalty coefficient for the friction compensation term; the constraints are: angular velocity constraints. (Phase-based constraints), fluid-structure interaction disturbance moment constraint ||τ ae,k ||≤τ max Robust pipe domain constraints

[0121] The segmented speed strategy is adjusted as follows:

[0122] Angle range low speed phase Compensation for static friction; angular range High-speed phase Activate fluid-structure interaction prediction; angle range Fine-tuning stage Constraint angle error Once fully folded into place, the system adjusts the folding locking mechanism to a holding state, thereby locking the rotor in that position.

[0123] like Figure 11 , 12 As shown, the mode transition process of the feathering-folding rotor is as follows:

[0124] Helicopter Mode to Fixed-Wing Mode: The forward mode transition of the rotor is a gradual transition from helicopter mode to transition mode to fixed-wing mode. In helicopter mode, when the rotor system receives the control signal of the folding variant, it first idles the engine and simultaneously obtains the current actual rotor speed through the speed sensor 5. During rotor deceleration, the pitch locking mechanism is released and the folding locking mechanism is locked. Actuator 2 drives push rod 3 to gradually adjust the blade pitch downwards. When the speed drops below a certain threshold, the internal stop mechanism (not shown in the figure) stops the rotor and locks it in a fixed position to prevent the blade 21 from colliding with the wing during subsequent folding. After the stop locking is completed, actuator 2 continues to adjust the blade pitch of blade 21 to the feathering position, thus completing the transition from helicopter mode to transition mode. Next, the pitch locking mechanism is switched to the locked state, and the folding locking mechanism is switched to the released state. Actuator 2 drives actuator push rod 3 to move upward, thereby causing the swashplate stationary ring 12 to move upward. The swashplate stationary ring 12 drives the swashplate moving ring 13 and the pitch linkage 31 to move upward, which in turn drives the multi-link mechanism to move, realizing the folding of the blade 21. During the folding process, when actuator push rod 3 reaches its limit position, the feedback signal from the limit sensor built into actuator 2 triggers the actuator limit switch, and actuator 2 stops operating, completing the folding action. After folding is completed, the system adjusts the folding locking mechanism to the holding state, realizing the locking of the rotor in this attitude state, and completely switching the rotor to fixed-wing mode, thus completing the entire mode conversion process.

[0125] Fixed-wing mode to helicopter mode: The rotor's reverse mode transition process is fixed-wing mode - transition mode - helicopter mode. In fixed-wing mode, when the rotor receives the deployment control signal, the system first switches the folding locking mechanism to the released state. Then, actuator 2 drives push rod 3 downward, causing the pitch linkage 31 and folding linkage mechanism to move, so that the blade 21 initially deploys to the feathering state, completing the transition mode switch. After switching to the transition state, the system switches the folding locking mechanism to the locked state and the pitch locking mechanism to the released state. Actuator 2 drives push rod 3 upward, causing the pitch linkage 31 and pitch arm 32 to move upward together, thereby causing the pitch hub 23 to rotate around the extension shaft of the central hub component 17, realizing the collective pitch adjustment of the blade 21. During the full deployment process, the system will continue to adjust the pitch of the blade 21 to adapt to changes in wind resistance, ensuring that the deployment can be completed quickly and stably. When actuator push rod 3 reaches its limit position, triggering the actuator limit switch, actuator 2 stops operating, and the pitch locking mechanism switches to the locked state, maintaining the rotor in the deployed state. Finally, the internal stop mechanism of the casing releases the rotor from the locked state, the system starts the engine, and the rotor gradually accelerates to normal operating conditions. After that, the pitch locking mechanism is released, and the rotor switches to helicopter mode, allowing the rotor to periodically change pitch and adjust collective pitch normally, thus completing the entire deployment and variant process.

Claims

1. A high-speed helicopter rotor feathering-folding mechanism, characterized in that, The system includes a main shaft assembly and a blade assembly. The main shaft assembly includes a main shaft (11), a central blade hub (17) fixedly sleeved on the upper end of the main shaft (11), and a drive unit. The central blade hub (17) has at least three sets of blade assemblies evenly arranged circumferentially. Each blade assembly includes a variable pitch hub (23) and blades (21) hinged to the variable pitch hub (23). The variable pitch hub (23) rotates relative to the central blade hub (17) to achieve blade pitch adjustment, and the pitch is fixed by a pitch locking assembly. The variable pitch hub (23) is connected to the drive unit through the variable pitch assembly, and the drive unit controls the pitch adjustment via a variable pitch assembly. The pitch component drives the variable pitch hub (23) to rotate. A folding component is also connected between the blade (21) and the variable pitch hub (23). The folding component is fixedly connected to the variable pitch component, and a folding locking component is provided between the folding component and the variable pitch hub (23). When the pitch locking component is unlocked and the folding locking component is locked, the drive unit drives the variable pitch hub (23) to rotate relative to the central hub component (17) through the variable pitch component to realize blade pitch change. When the pitch locking component is locked and the folding locking component is unlocked, the drive unit drives the folding component through the variable pitch component, and the folding component drives the blade (21) to fold.

2. The high-speed helicopter rotor feathering-folding mechanism according to claim 1, characterized in that, The drive unit includes an actuator (2), a stationary swashplate ring (12) and a moving swashplate ring (13) sleeved on the main shaft (11), a main ball joint (14), and a main shaft mounting seat (16). The main shaft (11) is coaxially mounted with the main ball joint (14). The outer edge of the main ball joint (14) is sequentially hinged with the stationary swashplate ring (12) and the moving swashplate ring (13) from bottom to top. The main shaft mounting seat (16) is fixedly sleeved on the main shaft (11). The main shaft mounting seat (16) is connected to the main shaft (11) via a torque arm assembly. The slant disk moving ring (13) is connected to the slant disk stationary ring (12). The actuator (2) drives the slant disk stationary ring (12) to slide up and down along the main shaft (11), thereby driving the slant main ball joint (14) and the slant disk moving ring (13) to slide up and down along the main shaft (11). The rotation of the main shaft (11) drives the main shaft spindle (16) to rotate. The main shaft spindle (16) drives the slant disk moving ring (13) to rotate through the torque arm assembly. The pitch variable assembly is connected to the slant disk moving ring (13).

3. The high-speed helicopter rotor feathering-folding mechanism according to claim 2, characterized in that, The pitch control assembly includes a pitch control link (31) and a pitch control arm (32). One end of the pitch control link (31) is hinged to the outside of the tilting disc moving ring (13), and the other end of the pitch control link (31) is hinged to one end of the pitch control arm (32). The other end of the pitch control arm (32) is hinged to the pitch control hub (23) and fixedly connected to a folding assembly. A folding locking assembly is provided at the hinged part between the pitch control arm (32) and the pitch control hub (23).

4. The high-speed helicopter rotor feathering-folding mechanism according to claim 3, characterized in that, The folding assembly includes a folding crank (41) and a folding connecting rod (44). One end of the folding crank is fixedly connected to the variable pitch arm (32), and the other end is hinged to one end of the folding connecting rod (44). The other end of the folding connecting rod (44) is hinged to the blade (21).

5. The high-speed helicopter rotor feathering-folding mechanism according to claim 1, characterized in that, The pitch locking assembly includes a drive motor (63) fixedly mounted on the extension shaft of the central hub (23), a main gear (69) disposed at the output end of the drive motor (63), a transition gear (70) meshing with the main gear, two output gears (71) meshing with the transition gear (70), an Archimedean spiral cam (76) coaxially fixedly connected to the output gear (71), and a locking connecting disk (84). The locking connecting disk (84) is fixedly mounted on the extension shaft of the variable pitch hub (23). The two Archimedean spiral cams (76) are symmetrically disposed on both sides inside the locking connecting disk (84). The drive motor (63) drives the main gear (69) to rotate. The main gear drives the two output gears to rotate through the transition gear. The two output gears drive the two Archimedean spiral cams (76) to rotate respectively. The profile curve of the Archimedean spiral cam generates radial displacement when rotating. Friction locking is achieved by synchronously pressing the inner side of the locking connecting disk (84).

6. The high-speed helicopter rotor feathering-folding mechanism according to claim 1, characterized in that, The folding locking assembly includes a locking connecting shaft (87) fixedly connected between the variable pitch arm (32) and the folding crank (41), a drive motor, a main gear located at the output end of the drive motor, a transition gear meshing with the main gear, two output gears meshing with the transition gear, an Archimedean spiral cam fixedly connected coaxially with the output gear, and a locking mechanism housing (86). The locking mechanism housing (86) is fixedly installed on the side of the variable pitch hub (23). The two Archimedean spiral cams (76) are symmetrically arranged on both sides of the locking connecting shaft (87). The drive motor drives the main gear to rotate, and the main gear drives the two output gears to rotate through the transition gear. The two output gears drive the two Archimedean spiral cams to rotate respectively. The profile curve of the Archimedean spiral cam generates radial displacement when rotating, and friction locking is achieved by synchronously pressing the side of the locking connecting shaft (87).

7. A multimodal control method for a high-speed helicopter rotor feathering-folding mechanism as described in claim 1, characterized in that, When the high-speed helicopter triggers the folding command, the pitch locking assembly unlocks and the folding locking assembly locks, controlling the engine driving the main shaft to idle and reduce its speed. When the speed reaches the predetermined range, the aerodynamic load is predicted through the fluid-structure interaction model, and the Tube-MPC controller optimizes the actuator control quantity, driving the actuator to smoothly adjust the blade pitch. After adjusting the blade pitch to the feathering position, the pitch locking assembly is switched to the locked state and the folding locking assembly is switched to the unlocked state. The actuator drives the blade to complete the folding action, and the folding locking assembly is switched to the locked state, keeping the rotor locked in the feathering-folding state. This completes the entire feathering-folding variant process. When the high-speed helicopter triggers the rotor deployment command, it switches the folding locking assembly to the released state, and the actuator drives the blades to fully deploy. It then switches the folding locking assembly to the locked state and the pitch locking assembly to the released state. The actuator continuously adjusts the blade pitch to adapt to changes in wind resistance. Once the blade pitch is adjusted to a suitable state, the engine is started.

8. The multimodal control method according to claim 7, characterized in that, The state vector of the Tube-MPC controller is: Among them, a f The fluid modal coefficients q and q are the values ​​of the reduced-order fluid-structure interaction model. Here are the modal coordinates and their derivatives for the reduced-order model, and θ is the propeller pitch angle. The derivative of the pitch angle. For the folding angle, The derivative of the fold angle; The prediction model equation for the Tube-MPC controller is: x k+1 =A(ρ k )x k +B(r k )u k +d k Where, x k+1 x is the control variable at time k+1. k Let A(ρ) be the control variable at time k. k B(ρ) is the time-varying system matrix, which depends on the real-time aerodynamic parameters of the fluid-structure interaction model; k ) represents the time-varying control matrix, generated from the actuator dynamics model; d k For the disturbance term, u k This represents the control input vector at discrete time step k; The objective function of the Tube-MPC controller is: Where Q, R, and P are all MPC weight matrices, x ref For reference trajectory; The dynamic management domain of the Tube-MPC controller is: Where γ is the safety factor, ▽F ae For aerodynamic load gradient; σ m σ represents the residual variance of the reduced-order model and the full-order model. noise Let d represent the sensor noise variance, and d represent the total disturbance experienced by the system during operation.

9. The multimodal control method according to claim 7, characterized in that, When the actuator drives the blade to fold, the Tube-MPC controller optimizes the actuator control quantity to drive the actuator to fold the blade smoothly.

10. The multimodal control method according to claim 9, characterized in that, The actuator drives the blades to perform a folding motion. When optimizing the actuator control quantity through the Tube-MPC controller, the actuator is driven by constraints of a segmented speed strategy. The actuator is driven by a three-segmented speed strategy, which is as follows: The range of folding angles is At that time, it was in the low-speed phase, and the folding angular velocity was The range of folding angles is At that time, it was in the high-speed phase, and the folding angular velocity was And perform fluid-structure interaction prediction; The range of folding angles is At that time, during the fine-tuning stage, the folding angular velocity was... Constraint angle error

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