Single drive tri-stable compliant variable sweep wing device

Abstract

The application provides a single-drive tri-stable compliant variable sweep wing device, which comprises a mounting plate provided with a through hole and a winding wheel arranged on the upper surface of the through hole; a driving mechanism arranged above the mounting plate and comprising a driving short rod, a driving long rod and a driving triangular plate; the driving short rod is a rotating arm fixedly connected with the winding wheel, and the driving long rod and the mounting plate form a rotating pair; the ends of the driving short rod and the driving long rod are respectively hinged to two corners of the driving triangular plate; a driven mechanism arranged below the mounting plate and comprising a driven short rod, a driven long rod and a driven triangular plate; the driven short rod and the mounting plate form a rotating pair, the driven long rod and the mounting plate form a rotating pair; the ends of the driven short rod and the driven long rod are respectively hinged to two corners of the driven triangular plate; the remaining corner of the driving triangular plate and the remaining corner of the driven triangular plate form a rotating pair through a long shaft, and the long shaft passes through the through hole; a wing is fixedly connected to the upper surface of the driving triangular plate; and a winch motor is connected with the winding wheel through a rope.

Description

Technical Field

[0001] This invention relates to the fields of variator aircraft, compliant mechanisms, multistable mechanisms, and variable sweep wings, and particularly to a single-drive tristable compliant variable sweep wing device. Background Technology

[0002] Variable sweep wing technology actively adjusts the wing sweep angle to coordinate lift, drag, and stability requirements across different phases, such as low-speed takeoff and landing, high-speed cruise, and maneuvering flight. It is an important technological approach in the field of variable aircraft.

[0003] Existing variable sweep wings can be broadly classified into three types: wing root pivot rotation type, wing in-wing shear type, and space structure type. The traditional wing root pivot rotation type is a mature technology. It usually drives the outer wing section to rotate around the wing root load-bearing pivot through a high-power hydraulic or electromechanical system. It can switch between a small sweep high lift state and a large sweep low drag state, and it is the earliest implementation method to be applied in engineering.

[0004] To alleviate the weight and load concentration problems of traditional wing root pivot schemes, existing research has proposed solutions such as replacing the heavy central pivot with a planar four-bar linkage, using preloaded springs or aerodynamic forces to achieve bistable sweep angle switching, and synchronously changing the sweep angle, wing area, and aspect ratio through the shear deformation of internal parallelogram units. The in-wing shear-type scheme has advantages such as distributed load-bearing and smaller aerodynamic center offset, but its implementation relies on a flexible skin capable of withstanding large-scale in-plane shear deformation and requires handling the elastic force coupling between the skin and the internal mechanisms.

[0005] Spatial structure variable sweepback schemes employ complex spatial linkage mechanisms, modular trusses, or distributed actuators to achieve multi-degree-of-freedom combined deformations such as sweep angle, span, dihedral angle, and torsion angle. These schemes offer high degrees of freedom in configuration design and geometric adjustment capabilities, but typically require coordinated control from multiple actuators. Furthermore, the load-bearing stiffness of the discrete frame, the adaptation of flexible skin, and system reliability remain key issues in engineering implementation.

[0006] In the area of ​​multistable structures and compliant mechanisms, existing technologies mainly achieve multiple stable equilibrium states through methods such as assembling bistable units, prestressed composite materials or thin-shell buckling, and combining rigid mechanisms with elastic energy storage elements. Multistable structures can maintain their configuration at stable points without continuous energy input and undergo abrupt transitions when crossing potential energy barriers. Related dynamic analyses typically need to consider the large-scale rigid-body motion and significant elastic deformation of flexible components. Commonly used methods include the floating coordinate system method, the co-rotation coordinate method, and the absolute nodal coordinate method. Among these, the floating coordinate system method is suitable for small-deformation flexible multibody systems, while the absolute nodal coordinate method is more suitable for describing nonlinear rigid-flexible coupling behavior under large rotations and deformations.

[0007] The drawback of the above technical solution is that: 1. Traditional root pivot rotary variable sweep wing drive and locking systems are complex in structure and heavy in weight. All aerodynamic loads tend to concentrate on the root pivot, resulting in local stress concentration, which places high demands on the load-bearing structure, drive power and locking reliability.

[0008] 2. The rotation of the traditional integral outer wing section will cause significant changes in the aerodynamic center and load distribution, which will impose additional burdens on the longitudinal static stability, flight control and structural layout of the aircraft, and is not conducive to its use in light, small or highly maneuverable aircraft.

[0009] 3. Although the in-wing shear design can reduce the aerodynamic center shift and achieve distributed load-bearing, it puts forward a complex requirement for the flexible skin to simultaneously meet the requirements of smooth aerodynamic shape, large-scale in-plane shear deformation, sufficient out-of-plane load-bearing stiffness and durability, which is difficult to implement in engineering.

[0010] 4. Spatial mechanism and modular truss schemes have more degrees of freedom and can achieve complex combination deformation, but they usually require multiple actuators, sensors and control loops to work together, which increases the system quality, assembly complexity, control difficulty and failure risk.

[0011] 5. Multistable structures based on bistable unit assembly or prestressed buckling are prone to introducing redundant stable states, disturbed motion modes or low structural stiffness, resulting in complex reconfiguration path control and possibly requiring multiple actuators to accurately select the target configuration.

[0012] 6. Existing multi-steady compliant mechanism designs mostly rely on empirical combinations, pseudo-rigid body models, or numerical optimization, lacking analytical design methods that directly address multiple preset sweep angle stable configurations, making it difficult to simultaneously ensure target pose accuracy, motion path accessibility, and energy barrier distribution rationality.

[0013] 7. Rapid transitions in compliant mechanisms involve large-scale rigid body motion, large deformation of flexible members, and nonlinear elastic energy storage and release. Traditional rigid body dynamics or small-deformation linear models are difficult to accurately predict steady-state maintenance, obstacle crossing triggering, and transient response. If a high-precision nonlinear finite element method is used, it may lead to high modeling and computation costs.

[0014] 8. Rigidly connected motors, gears, or linkages will restrict the free release of the mechanism during obstacle-crossing transitions and transmit the reverse impact to the drive hardware; at the same time, aerodynamic loads will change the equilibrium position after release, and the current solutions have not been sufficiently verified for dynamic switching and configuration maintenance under aerodynamic loads.

[0015] Therefore, how to provide a single-drive tristable compliant variable-sweep wing device that is structurally stable, lightweight, and can be quickly reconfigured has become a problem that the industry needs to solve. Summary of the Invention

[0016] To address the shortcomings of existing technologies, the present invention aims to provide a single-drive tristable compliant variable-sweep wing device that is structurally stable, lightweight, and capable of rapid reconfiguration. This invention utilizes a single drive input to achieve stable maintenance and rapid switching between three preset sweep configurations, aiming to solve the problem that existing variable-sweep wings struggle to simultaneously maintain multiple configurations, rapidly reconfigurate, and operate stably under aerodynamic loads. Addressing the limitations of complex multi-actuator systems, the constraints of traditional rigid transmissions on transient release speeds, the limited switchable configurations of bistable mechanisms, and the lack of analytical synthesis methods for multistable compliant mechanisms oriented towards specific configurations, this invention proposes a single-drive tristable compliant device composed of an active four-bar linkage, a passive four-bar linkage, a compliant energy storage rod, and a unidirectional rope wheel-type decoupled drive. This device enables the wing to maintain passive stability between three configurations: 20° deployment, 55° mid-range, and 68° large sweep, and to achieve rapid reconfiguration after overcoming the energy barrier.

[0017] This invention connects two sets of four-bar linkages at the same coupling point, ensuring that the theoretical trajectories of the two mechanisms do not completely overlap. A deformable, compliant energy storage rod absorbs this "non-overlap," transforming geometric incompatibility into elastic potential energy. This allows a stable configuration to naturally form near several trajectory intersection points. The motor does not need to continuously lock the wing; it only needs to slowly pull the wing via a rope pulley to allow it to overcome the energy barrier. After overcoming the obstacle, the rope slackens, the compliant energy storage rod releases energy, and the wing quickly jumps to the next stable swept-back configuration.

[0018] To achieve the above objectives, the present invention provides a single-drive tristable compliant variable-sweep wing device, comprising: Mounting plate, with through holes; upper surface of mounting plate is equipped with a rope winding wheel; The active mechanism is located above the mounting plate and includes an active short rod, an active long rod, and an active triangular plate. The active short rod is a rotating arm that is fixedly connected to the rope sheave. The active long rod and the mounting plate form a rotating pair through an upper fixed shaft. The ends of the active short rod and the active long rod are respectively hinged to the two corners of the active triangular plate. The passive mechanism, located below the mounting plate, includes a passive short rod, a passive long rod, and a passive triangular plate. The passive long rod is a compliant energy storage rod capable of elastic deformation along its length and storing elastic potential energy. The passive short rod and the mounting plate form a revolute joint via a first lower fixed shaft, and the passive long rod and the mounting plate form a revolute joint via a second lower fixed shaft. The ends of the passive short rod and the passive long rod are respectively hinged to two corners of the passive triangular plate. The remaining corner of the active triangular plate is the upper coupling point, and the remaining corner of the passive triangular plate is the lower coupling point. A long shaft connects the upper and lower coupling points to form a common coupling point, enabling the active and passive triangular plates to form a revolute joint. The long shaft passes through a through hole. The wing is fixedly connected to the upper surface of the active triangular plate; The winch motor is mounted on the frame and connected to the rope reel via a rope. The passive long rod is used to compensate for the deviation in theoretical motion trajectory at the common coupling point when the active and passive mechanisms move independently, so that the single-drive tristable compliant variable sweep wing device can form a steady state at the three stable configurations.

[0019] In this invention, both the active mechanism and the passive mechanism are planar four-bar linkages and share the same frame; the active mechanism and the passive mechanism are connected by a revolute joint.

[0020] In this invention, the active mechanism is used to receive a single external driving input, and the passive mechanism is used to provide motion constraints and elastic energy storage.

[0021] In this invention, the projection of the major axis is the common coupling point, and the active mechanism and the passive mechanism are coupled through the common coupling point.

[0022] In this invention, the winch motor drives the rope wheel to rotate via a rope, and the rotation of the rope wheel drives the active short rod to rotate, thereby driving the active mechanism and the passive mechanism to move together; the wing direction and sweep configuration are determined by the position of the common coupling point.

[0023] In this invention, the winch motor can only drive the winding wheel to rotate by winding the rope; unwinding the rope has no effect on the winding wheel.

[0024] In this invention, the control or determination of rapid reconfiguration is based on the release / decoupling criteria of the mechanism overcoming the potential barrier, the driving torque dropping to zero or tending to reverse, thus separating the slow motor energy storage stage from the rapid elastic transition stage.

[0025] This invention provides a single-drive tristable compliant variable-sweep wing device and its rapid reconfiguration method, enabling the variable-sweep wing to sequentially switch between three preset sweep configurations through a single input, and passively maintain its position at each stable configuration by relying on its own multistable energy terrain, thereby reducing the continuous holding torque and control complexity.

[0026] This invention also provides an analytical motion synthesis and performance screening method for preset stable configurations. It replaces at least one rigid rod in the passive mechanism with a compliant energy storage rod, transforming the geometric incompatibility between the two mechanism trajectories into the elastic deformation and potential energy storage of the compliant energy storage rod, thereby forming multiple stable swept configurations. Through three-position synthesis, six-order algebraic trajectory and full-cycle tensile deformation screening, parameters with dual energy barriers and three stable equilibrium points are obtained.

[0027] This invention also provides a mechanism size design method for multiple preset stable configurations, including selecting a passive rod reference trajectory, determining multiple target poses on the trajectory, obtaining candidate mechanism parameters by three-position analytical synthesis, and screening by kinematic feasibility and the tensile deformation range of the compliant energy storage rod.

[0028] This invention achieves dynamic decoupling between the low-speed energy storage stage and the high-speed jump release stage by using a hollow rhomboid variable stiffness compliant energy storage rod and a unidirectional rope wheel type flexible decoupling drive. During the energy storage stage, the motor input is transmitted by a tension rope. After the mechanism crosses the energy barrier, the rope relaxes and releases the drive constraint, allowing the mechanism to complete rapid reconstruction by relying on the elastic potential energy released by the compliant energy storage rod, while reducing the reverse impact on the motor and transmission chain.

[0029] Based on the problems of existing technology, this invention avoids the weight and control burden caused by heavy wing root pivots, complex space trusses and multi-actuator coordinated control. While maintaining the continuous aerodynamic shape and structural load-bearing capacity of the wing, it combines the zero power consumption maintenance, elastic jump release and single-drive controllable switching of the multi-steady-state mechanism, providing a simpler mechanism implementation for lightweight variable-sweep wings.

[0030] According to another specific embodiment of the present invention, both the active mechanism and the passive mechanism are crank-rocker mechanisms.

[0031] According to another specific embodiment of the present invention, the active triangle is an obtuse triangle, with its major axis connected to the larger acute angle (29°) of the active triangle, the active short rod connected to the smaller acute angle (22.4°) of the active triangle, and the active long rod connected to the obtuse angle (128.6°) of the active triangle.

[0032] According to another specific embodiment of the present invention, the passive triangle is a right triangle, with its major axis connected to the larger acute angle (51.3°) of the passive triangle, the passive long rod connected to the smaller acute angle (38.7°) of the passive triangle, and the passive short rod connected to the right angle of the passive triangle.

[0033] According to another specific embodiment of the present invention, the compliant energy storage rod is mainly subjected to axial tensile deformation as a whole.

[0034] In this design, the passive long rod is in an energy storage state when it is stretched, and its overall deformation is mainly axial.

[0035] According to another specific embodiment of the present invention, the rope winding wheel is provided with a rope winding groove and a rope threading hole, the rope passes through the rope threading hole and is secured, and then wound around the rope winding groove.

[0036] In this plan, the direction of rope winding will be manually adjusted as needed during actual operation.

[0037] In the latter half of the active mechanism's movement, the speed of the winding pulley is higher than that of the winch motor. If the winch motor is directly connected to the winding pulley, it will inhibit the movement of the winding pulley. Using a rope to connect the winding pulley can achieve decoupling; when the speed of the winding pulley is higher than that of the winch motor, the rope will loosen and will not interfere with the movement of the winding pulley.

[0038] According to another specific embodiment of the present invention, the upper fixed shaft, the first lower fixed shaft, and the second lower fixed shaft are all fixedly connected to the mounting plate.

[0039] According to another specific embodiment of the present invention, when the active mechanism and the passive mechanism are treated as independent rigid four-bar linkages for kinematic analysis, the trajectory of the upper coupling point is a triangular trajectory, and the trajectory of the lower coupling point is a teardrop-shaped trajectory. The trajectories of the upper and lower coupling points have three intersection points, located at the tip and two sidewalls of the teardrop-shaped trajectory, respectively. The three intersection points correspond one-to-one with three stable configurations. The state corresponding to the intersection point is the steady state where the extension of the passive rod is zero.

[0040] In this scheme, the three steady states correspond to angles of 20°, 55°, and 68° between the long side of the wing and the leading edge of the mounting plate, respectively.

[0041] When switching from a 20° spread configuration to a 55° intermediate configuration, the rope is wound clockwise around the groove; when switching from a 55° intermediate configuration to a 68° large sweep configuration, the rope is wound counterclockwise around the groove. The rope winding direction is opposite in the two switching processes, so the rope winding direction needs to be adjusted.

[0042] According to another specific embodiment of the present invention, the passive rod is hollow and has a rhomboid elongated hole. The side beams of the rhomboid elongated hole can undergo bending and tensile deformation.

[0043] In this scheme, the passive rod exhibits low equivalent tensile stiffness in the early stage of energy storage and high tangential stiffness when approaching the obstacle crossing threshold, in order to balance reducing the driving load and providing the releasable elastic potential energy required for rapid reconfiguration.

[0044] According to another specific embodiment of the present invention, the passive rod is made of thermoplastic polyurethane elastomer material.

[0045] Under perfectly rigid conditions, the active mechanism and the passive mechanism each generate different theoretical trajectories. After they couple at a common coupling point, they form an over-constrained closed chain. Unless the two theoretical trajectories completely overlap, the system has zero degrees of freedom.

[0046] To enable controllable motion and multistable behavior in overconstrained topologies, this invention replaces a rigid rod in the passive mechanism with a compliant energy storage rod (passive long rod) capable of axial extension and energy storage. The geometric incompatibility between the active and passive trajectories is converted into the axial deformation ΔL of the compliant energy storage rod. The elastic potential energy stored during the mechanism's motion is approximately proportional to the square of ΔL. When the common coupling point P moves to the vicinity of the three intersection points P1, P2, and P3 of the two theoretical trajectories, the geometric incompatibility reaches a local minimum, and the system potential energy forms a local trough, corresponding to three stable configurations: 20° spread, 55° intermediate, and 68° large sweep, respectively. Details of the three stable configurations are shown in Table 1.

[0047] Table 1. Three Preset Stable Configurations and Their Functional Positioning

[0048] The dimensions of the active and passive mechanisms are obtained through three-position analytical motion synthesis. First, a passive link curve with cusp characteristics is selected as the reference trajectory to create a deeper potential energy well near the intermediate stable point. Then, three target poses are selected on this curve as preset stable configurations, each containing both planar position and attitude angle. Based on the three-position motion generation theory, a homogeneous transformation matrix is ​​used to describe the rigid body displacement of the link plane from the initial pose to the target pose. Combined with the link length constraint that the distance between the moving hinge point and the corresponding fixed hinge point is constant, a linear relationship between the coordinates of the fixed hinge point and the coordinates of the moving hinge point is established. Given the link length, elimination yields a sixth-order algebraic trajectory that satisfies the three-target pose constraint. This trajectory constitutes the analytical solution space for the selectable fixed hinge points.

[0049] After obtaining the analytical solution space, this invention further establishes a hierarchical screening process. The first layer of screening is used to eliminate unrealizable schemes such as those that do not meet the Grashof condition, have branch defects, or have self-intersections in the connecting rod curves, thus obtaining continuous and effective line segments. The second layer of screening uses quasi-static analysis, equating the compliant energy storage rod to a variable-length rod, condensing the original rigid-flexible coupling system into a single-degree-of-freedom six-bar linkage, traversing the input angle of the active crank, and calculating the axial deformation mapping of the compliant energy storage rod. The screening conditions include: the compliant energy storage rod maintains positive tension throughout the entire deformation cycle to suppress compressive buckling and internal dissipation; the peak tensile deformation is controlled within the range of 10 mm to 30 mm to balance sufficient elastic potential energy and driving stroke and material strength constraints. Preferably, the peak tensile deformations corresponding to the two state transitions are approximately 28.6 mm and 27.6 mm, respectively, which can form two energy barriers that are crossed sequentially.

[0050] To reduce the peak driving force required to overcome the potential barrier and avoid stress concentration in the compliant rod, this invention designs the compliant energy storage rod as a hollow rhomboid microstructure. This structure exhibits a two-stage tensile stiffness response: in the initial stage of energy storage, the rhomboid side beams primarily undergo bending deformation, resulting in low equivalent tensile stiffness and reducing the motor's loaded torque; as the instability threshold approaches, the rhomboid units gradually straighten and the deformation mode locks in, significantly increasing the structural tangential stiffness and providing sufficient releaseable elastic energy for obstacle-crossing transitions.

[0051] This invention employs a unidirectional rope wheel flexible drive to decouple the energy storage and release processes. During the energy storage phase, the flexible rope remains taut and transmits the motor input, causing the angular velocity of the rope wheel to follow the input motion, and the drive mechanism gradually ascends to near the energy barrier. Once the mechanism crosses the critical point and triggers a jump, the rope yields and relaxes, the drive constraint is removed, the motor torque drops to zero, and the mechanism is rapidly reconfigured by the elastic potential energy released from the compliant energy storage rod. This process separates the low-speed motor energy storage phase from the high-speed elastic release phase, reducing the limitation of rigid transmission on the transient jump speed.

[0052] To verify the technical solution, a rigid-flexible coupled dynamic model was established. The rigid members were described using centroid coordinates, while the compliant energy storage rod was discretized into two-dimensional planar beam elements using the absolute nodal coordinate method. The longitudinal tensile strain energy, transverse bending strain energy, mass matrix, constraint equations, and Lagrange multipliers were uniformly incorporated into the first type of Lagrange dynamic equations. The simulation process consisted of two stages: energy storage loading and obstacle clearance release. Obstacle clearance was criteriond by the driving torque dropping to zero; after triggering, the motor torque and speed constraints were removed. Simulation results showed that the peak driving torque during the energy storage stage switching from 68° to 55° was approximately 2.8 N·m, and the peak loading torque during the switch from 55° to 20° was approximately -3.4 N·m. The main sweep angle reconstruction process after obstacle clearance could be completed within approximately 50 ms.

[0053] The present invention has the following beneficial effects: 1. By coupling two four-bar linkages at a common coupling point and introducing a compliant energy storage rod, trajectory incompatibility is transformed into elastic potential energy terrain, enabling the formation of three stable configurations under a single drive input, reducing the need for multi-actuator collaborative control and continuous torque holding.

[0054] 2. The design solution space is constructed by using three-position analytical motion synthesis and sixth-order algebraic trajectory. It can directly design the mechanism size for preset stable configurations such as 20°, 55° and 68°. Compared with pure numerical optimization, it is more conducive to avoiding target configuration drift and improving design interpretability.

[0055] 3. Set full-cycle tensile deformation and peak deformation range screening to keep the compliant energy storage rod in tension during movement, reduce the risk of compression buckling, and ensure that the peak tensile deformation of about 28.6 mm and 27.6 mm can take into account energy storage capacity, drive stroke and material safety.

[0056] 4. The use of hollow rhomboid variable stiffness compliant energy storage rods reduces the equivalent stiffness and driving torque in the initial stage, and increases the tangential stiffness and release elastic energy when approaching the instability threshold, which helps to reduce peak driving load and improve jump release effect.

[0057] 5. The unidirectional rope wheel flexible drive maintains coupling during the energy storage phase and automatically relaxes and decouples during the obstacle crossing and transition phase. This can separate the low-speed motor loading from the rapid elastic release, reduce the transmission of reverse impact, and improve the transient reconfiguration speed.

[0058] 6. In the prototype verification, the mechanism was able to maintain a multi-stable configuration and complete rapid reconfiguration under aerodynamic loads; steady-state CFD and wind tunnel tests both showed that when the sweep angle was reduced from 68° to 55° and 20°, the lift coefficient and lift-to-drag ratio were improved overall, demonstrating clear aerodynamic adjustment effects and engineering application potential.

[0059] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0060] Figure 1 This is a top view of the 20° deployed configuration of the variable sweep wing device in Embodiment 1; Figure 2 This is a top view of the 55° intermediate configuration of the variable sweep wing device in Embodiment 1; Figure 3 This is a top view of the 68° large sweep configuration of the variable sweep wing device in Embodiment 1; Figure 4 This is a schematic diagram of the overall structure of the variable sweep wing device in Embodiment 1; Figure 5 This is a partial structural schematic diagram of the variable sweep wing device in Embodiment 1; Figures 6a-6c This is a schematic diagram of three preset stabilization configurations for the variable sweep wing device, in which: Figure 6a It has a 20° configuration. Figure 6b It has a 55° configuration. Figure 6c It has a 68° configuration; Figures 7a-7f This includes the kinematic synthesis, candidate solution screening, axial deformation mapping, dual-barrier energy terrain diagram, and performance evaluation of the variable-sweep wing device, among which: Figure 7a This represents the topological evolution from over-constrained rigid mechanisms to rigid-flexible coupled systems. Figure 7b This indicates that target attitudes P1, P2, and P3 are located on the passive coupling path; Figure 7c This represents the analytical trajectory curve of a candidate fixed hinge at a specified side link length; Figure 7d This represents the process of constructing the feasible region and extracting the effective segment; Figure 7e Curves showing the variation of axial deformation ΔL on the two motion branches with the input angle θ; Figure 7f A topological diagram showing the elastic potential energy distribution of two switching barriers; Figures 8a-8dThis is a schematic diagram of the prototype architecture of a variable-sweep wing device equipped with a rhomboid variable stiffness compliance rod and a unidirectional rope pulley decoupled drive system, wherein: Figure 8a It is a schematic diagram of the morphing wing prototype in three stable states: 20°, 55° and 68°, and it is equipped with a diamond-shaped variable stiffness passive rod. Figure 8b yes Figure 8a Schematic diagram of the passive long rod; Figure 8c This is a schematic diagram of the rope state of the decoupled drive system during the energy storage stage (coupling state); Figure 8d This is a schematic diagram of the rope state of the decoupled drive system during the jump phase (decoupling state); Figures 9a-9d This is the rigid-flexible coupling dynamic model and simulation results of the variable sweep wing device, including: Figure 9a It is the model topology, which includes fixed pivots and moving nodes; Figure 9b Represents the coordinates of ANCF planar beam elements and nodes; Figure 9c It represents the history of the change in driving torque during two consecutive state transitions, and can show the decoupling of torque from zero after crossing the potential barrier; Figure 9d This represents the sweep angle response and instantaneous sinking phenomenon during the rapid reconstruction process; Figure 10 This is a schematic diagram of the wind tunnel testing equipment and measurement system, with the variable sweep wing device mounted on the optical worktable; Figures 11a-11e This is a schematic diagram showing the steady-state CFD aerodynamic reference data and the results of the wind tunnel dynamic switching test, where: Figure 11a The variation of the wing sweep angle is shown at wind tunnel speeds of 10 m / s and 20 m / s; the solid curve and the shaded band represent the mean and ±1 standard deviation of the sample set, respectively. Figure 11b Is with Figure 11a The change process of the lift coefficient corresponding to the event; the solid curve and the shaded band represent the mean and ±1 standard deviation of the sample set, respectively; Figure 11c Is with Figure 11a The change process of the drag coefficient corresponding to the event; the solid curve and the shaded band represent the mean and ±1 standard deviation of the sample set, respectively; Figure 11d It is a high-speed sequence of images showing the 68°→55° switching process; Figure 11e It is a high-speed sequence of images of the 55°→20° switching process. Detailed Implementation

[0061] Example 1

[0062] This embodiment provides a single-drive tristable compliant variable-sweep wing device (hereinafter referred to as "variable-sweep wing device" in the accompanying drawings), such as Figure 1-9dAs shown, it includes: mounting plate 1, active mechanism 2, passive mechanism 3, wing 4 and winch motor 901.

[0063] The mounting plate 1 has a through hole 101; the upper surface of the mounting plate 1 has a rope wheel 102.

[0064] The active mechanism 2 is located above the mounting plate 1 and includes an active short rod 201 (AB), an active long rod 202 (DC), and an active triangular plate 203 (PBC). The active short rod 201 is a rotating arm that is fixedly connected to the rope wheel 102. The active long rod 202 and the mounting plate 1 form a rotating pair through the upper fixed shaft 204. The ends of the active short rod 201 and the active long rod 202 are respectively hinged to the two corners of the active triangular plate 203.

[0065] The passive mechanism 3 is located below the mounting plate 1 and includes a passive short rod 301 (EF), a passive long rod 302 (HG), and a passive triangular plate 303 (PFG). The passive long rod 302 is a compliant energy storage rod that can undergo elastic deformation along its own length and store elastic potential energy. The compliant energy storage rod is mainly subjected to axial tensile deformation as a whole. The passive short rod 301 and the mounting plate 1 form a revolute joint through the first lower fixed shaft 304, and the passive long rod 302 and the mounting plate 1 form a revolute joint through the second lower fixed shaft 305. The ends of the passive short rod 301 and the passive long rod 302 are respectively hinged to the two corners of the passive triangular plate 303. The remaining corner of the active triangular plate 203 is the upper coupling point 51, and the remaining corner of the passive triangular plate 303 is the lower coupling point 52. A long shaft 306 connects the upper coupling point 51 and the lower coupling point 52 in series to form a common coupling point, so that the active triangular plate 203 and the passive triangular plate 303 form a revolute joint. The long shaft 306 passes through the through hole 101.

[0066] The active triangle 203 is an obtuse triangle, with its major axis 306 connected to the larger acute angle (29°) of the active triangle 203. The active short rod 201 is connected to the smaller acute angle (22.4°) of the active triangle 203, and the active long rod 202 is connected to the obtuse angle (128.6°) of the active triangle 203.

[0067] The passive triangle 303 is a right triangle, with its major axis 306 connected to the larger acute angle (51.3°) of the passive triangle 303. The passive long rod 302 is connected to the smaller acute angle (38.7°) of the passive triangle 303, and the passive short rod 301 is connected to the right angle of the passive triangle 303. The passive long rod 302 is an elastic tension rod, which is in an energy storage state when stretched. The passive long rod 302 is provided with a diamond-shaped elongated hole 307 and is made of thermoplastic polyurethane elastomer material.

[0068] The upper surface of the active triangular plate 203 is fixedly connected to the wing 4; when the active mechanism 2 and the passive mechanism 3 are treated as independent rigid four-bar linkages for kinematic analysis, the trajectory of the upper coupling point 51 is a triangular trajectory. Γ 2) The trajectory of the lower coupling point 52 is a teardrop-shaped trajectory ( Γ 1) The trajectory of the upper coupling point 51 and the trajectory of the lower coupling point 52 have three intersection points, located at the tip of the teardrop-shaped trajectory and the two sidewalls, respectively; the three intersection points correspond one-to-one with the three stable configurations. The state corresponding to the intersection point is the steady state where the extension of the passive long rod 302 is zero; the three steady states correspond to the angles between the long side 41 of the wing and the leading edge 14 of the mounting plate being 20°, 55°, and 68°, respectively.

[0069] The winch motor 901 is mounted on the frame (not shown in the figure) and is connected to the rope reel 102 via a rope 902. The rope reel 102 is provided with a rope groove 103 and a rope hole 104. The rope 902 passes through the rope hole 104 and is secured, and then winds around the rope groove 103.

[0070] Both the active mechanism 2 and the passive mechanism 3 are crank-rocker mechanisms and share the same frame. The projection of the long axis 306 is the common coupling point (P), through which the active mechanism 2 and the passive mechanism 3 are coupled. The upper fixed axis 204, the first lower fixed axis 304, and the second lower fixed axis 305 are all fixedly connected to the mounting plate 1. The passive long rod 302 is used to compensate for the theoretical motion trajectory deviation generated at the common coupling point when the active mechanism 2 and the passive mechanism 3 move independently, so that the single-drive tristable compliant variable-sweep wing device forms a steady state at three stable configurations (20°, 55°, and 68° in this embodiment).

[0071] This embodiment, while satisfying the principles of tristable energy terrain and unidirectional decoupling drive, can be adjusted according to different wing sizes and mission requirements. The specific implementation method is described below.

[0072] 1. Determine the target configuration. Based on the mission requirements of the variable sweep wing, three preset stable sweep angles are determined (20°, 55° and 68° in this embodiment), corresponding to the three configurations of spread, intermediate and large sweep, respectively.

[0073] 2. Establish the reference trajectory of the passive mechanism. Select the teardrop-shaped link curve with a cusp as the link trajectory of the passive mechanism. Select three target poses (P1, P2, P3) on this trajectory. The area near the cusp is selected as the intermediate stable point, and the other two points are selected along both sides of the curve to form a tristable layout with obvious potential energy trough.

[0074] 3. Analyze the integrated active mechanism. Establish homogeneous transformations and link length constraints using three target poses, and solve for the sixth-order algebraic trajectories of the fixed and moving hinge points under a given link length. Then, combine Grashof conditions, branch defects, self-intersection curves, and effective motion segments to select the final mechanism dimensions.

[0075] 4. Design a compliant energy storage rod. Replace the corresponding rigid rod in the passive mechanism with a hollow rhombic microstructure compliant energy storage rod, and use quasi-static calculations to ensure that its axial deformation remains tensile throughout the entire cycle, with the peak deformation controlled between 10 mm and 30 mm.

[0076] 5. Arrange a unidirectional rope pulley drive. Connect the winch motor to the flange drum (rope pulley), flexible rope, and lower connecting rod. Adjust the rope preload to tension the rope and transmit the input during the energy storage phase. After the mechanism overcomes the potential barrier, allow the rope to slacken, enabling the mechanism to complete rapid reconfiguration without drive constraints.

[0077] 6. Perform dynamic and aerodynamic verification. Establish a rigid-flexible coupled dynamic model, using zero torque as the release trigger condition; then perform CFD calculations under a fixed sweep configuration, and record the dynamic responses of sweep angle, lift, and drag in a wind tunnel to verify the multisteady state retention and rapid reconfiguration performance.

[0078] It's important to note that the winch motor is unidirectionally driven. Each time the angle is switched, the winding direction of the rope reel changes to facilitate the next switch. For example, if the winch motor always rotates clockwise, the initial winding direction of the rope reel is clockwise. When the wing angle changes from 68° to 55°, the winding direction changes to counter-clockwise; when the wing angle changes from 55° to 20°, the winding direction changes back to clockwise (as shown in Table 2). Optimizing this is the inventor's next research direction.

[0079] Table 2

[0080] The scaled-down prototype of this embodiment was validated in an open wind tunnel with a test section size of 600mm × 600mm. To meet the blockage ratio constraint, the prototype's wingspan was 300mm, the average chord length was approximately 100mm, and the airfoil adopted the high-lift airfoil of Cessna Category 182 general aviation aircraft. The main frame used high-density foam to reduce mass and allow for some deformation, and the airfoil was covered with an elastic polymer film to maintain a continuous aerodynamic shape. Rigid members were mainly made of PLA-CF and carbon fiber, high-load components and cable-driven parts were machined from 7075 aluminum alloy, compliant components were printed using TPU85A, and rotating joints were assembled using shoulder bolts, lock nuts, and washers.

[0081] like Figure 10As shown, the test platform includes a tristable mechanism 6, a nine-axis attitude sensor 7, a six-axis force sensor 8, a winch motor 901, an optical test circuit board 10, and an anemometer 11 for calibrating the free airflow speed; the wing 4 is mounted on the support rod 12.

[0082] Aerodynamic measurements employed a top-mounted six-axis force sensor, with a triaxial force measurement range of 15 N and an overall accuracy better than 0.3% FS. The test angle of attack was maintained at 8°. The force signal sampling frequency was 800 Hz, and a time history was generated at 0.01 s intervals after synchronization with the attitude measurement results. Each dynamic switching test was repeated three times, and event alignment and ensemble averaging were performed based on the sweep angle response characteristic points. The prototype and test conditions are shown in Table 3, and the numerical simulation results are shown in Table 4.

[0083] Table 3 Prototype Implementation and Testing Conditions

[0084] Table 4 Numerical simulation results of wing aerodynamic characteristics under different operating conditions (angle of attack 8°)

[0085] As shown in Figure 11, wind tunnel dynamic tests indicate that under an incoming flow of 20 m / s, the complete transition time from the start of rapid sweep angle change to the establishment of the next stable platform is approximately 444 ms (68° to 55°) and 383 ms (55° to 20°), respectively. Under the same incoming flow conditions, the measured lift coefficient increases from the large sweep state (approximately 0.35) to near the intermediate state (approximately 0.79), and reaches approximately 1.08 in the deployed state, indicating that reducing the sweep angle can significantly improve lift and lift-to-drag ratio. The drag peak is mainly concentrated within the rapid switching window, reflecting the influence of transient deformation velocity, attitude change, and unsteady flow adjustment.

[0086] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the scope of the invention. Any person skilled in the art can make modifications without departing from the scope of the invention; all equivalent modifications made in accordance with the invention should be covered by the scope of the invention.

Claims

1. A single-drive tristable compliant variable-sweep wing device, characterized in that, include: Mounting plate, the mounting plate is provided with through holes; the upper surface of the mounting plate is provided with a rope winding wheel; An active mechanism, located above the mounting plate, includes an active short rod, an active long rod, and an active triangular plate; the active short rod is a rotating arm fixedly connected to the winding wheel, and the active long rod and the mounting plate form a rotating pair via an upper fixed shaft; the ends of the active short rod and the active long rod are respectively hinged to two corners of the active triangular plate. A passive mechanism, located below the mounting plate, includes a passive short rod, a passive long rod, and a passive triangular plate. The passive long rod is a compliant energy storage rod capable of elastic deformation along its length and storing elastic potential energy. The passive short rod and the mounting plate form a revolute joint via a first lower fixed shaft, and the passive long rod and the mounting plate form a revolute joint via a second lower fixed shaft. The ends of the passive short rod and the passive long rod are respectively hinged to two corners of the passive triangular plate. The remaining corner of the active triangular plate is the upper coupling point, and the remaining corner of the passive triangular plate is the lower coupling point. A long shaft connects the upper coupling point and the lower coupling point to form a common coupling point, thereby forming a revolute joint between the active triangular plate and the passive triangular plate. The long shaft passes through the through hole. The wing is fixedly connected to the upper surface of the active triangular plate; A winch motor is mounted on a frame, and the winch motor is connected to the rope reel via a rope. The passive long rod is used to compensate for the theoretical motion trajectory deviation generated at the common coupling point when the active mechanism and the passive mechanism move independently, so that the single-drive tristable compliant variable sweep wing device forms a steady state at the three stable configurations.

2. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, Both the active mechanism and the passive mechanism are crank-rocker mechanisms.

3. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, The active triangle is an obtuse triangle, the major axis is connected to the larger acute angle of the active triangle, the active short rod is connected to the smaller acute angle of the active triangle, and the active long rod is connected to the obtuse angle of the active triangle.

4. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, The passive triangle is a right triangle, with its major axis connected to the larger acute angle of the passive triangle, its long passive rod connected to the smaller acute angle of the passive triangle, and its short passive rod connected to the right angle of the passive triangle.

5. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, The compliant energy storage rod is mainly subjected to axial tensile deformation as a whole.

6. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, The rope reel is provided with a rope groove and a rope hole. The rope passes through the rope hole, is secured, and is wound around the rope groove.

7. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, The upper fixed shaft, the first lower fixed shaft, and the second lower fixed shaft are all fixedly connected to the mounting plate.

8. The single-drive tristable compliant variable-sweep wing device as described in claim 1, characterized in that, When the active mechanism and the passive mechanism are treated as independent rigid four-bar linkages for kinematic analysis, the theoretical trajectory of the upper coupling point is a triangular trajectory, and the theoretical trajectory of the lower coupling point is a teardrop-shaped trajectory. The theoretical trajectories of the upper coupling point and the lower coupling point have three intersection points, located at the tip and two sidewalls of the teardrop-shaped trajectory, respectively. These three intersection points correspond one-to-one with the three stable configurations.

9. The single-drive tristable compliant variable-sweep wing device as described in claim 5, characterized in that, The passive rod is hollow and has a diamond-shaped elongated hole.

10. The single-drive tristable compliant variable-sweep wing device as described in claim 5, characterized in that, The passive rod is made of thermoplastic polyurethane elastomer.

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