Bifurcation test device and method for landing gear over-center mechanism based on control extension

Abstract

The present invention discloses a landing gear over-center mechanism bifurcation test device and method based on control extension, which relates to the field of aerospace technology and includes a test stand assembly, a feedback control system, and an over-center mechanism assembly; the test stand assembly includes a test bench and a drive-end support bench and a linear guide rail support installed at both ends of the test bench respectively; the over-center mechanism assembly includes a first connecting rod, a second connecting rod, a slider, a linear guide rail, a tension spring, and a moving support; the feedback control system includes a servo motor, a PLC control cabinet, a reducer, a transmission shaft, a dynamic torque sensor, a first angle sensor, and a second angle sensor; the PLC control cabinet can drive the first connecting rod to rotate through the servo motor, thereby driving the slider to slide along the linear guide rail. The present invention can effectively combine feedback control to change the unstable branch into a stable branch, thereby realizing the global tracking of the mechanism motion trajectory and bifurcation point, and obtaining the most real stable branch and bifurcation point.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and particularly to a bifurcated test device and method for a landing gear over-center mechanism based on control continuation. Background Art

[0002] The strut-type locking mechanism is the key to ensuring that the landing gear is locked in the lowered position and can stably carry loads. Among many landing gear retraction and extension failures, a considerable part is caused by locking mechanism failures. As Figures 1 - 3 shown, the strut-type locking mechanism consists of two locking link rods hinged to each other, a locking spring, and a locking actuator. When studying its motion mechanism alone, it can be simplified as an over-center mechanism for analysis. At the moment when the landing gear is approaching the upper lock, the locking mechanism will instantaneously jump from an unstable state to a locked stable state. The unlocking process is the opposite. Such a phenomenon cannot be explained solely based on the results of experiments and simulations. According to the explanation of bifurcation theory, bifurcation occurs at the moment when the locking mechanism becomes unstable. Therefore, the critical point at which this bifurcation occurs is of great engineering design value for the locking mechanism.

[0003] Currently, the research on the stability of landing gear locking mechanisms using bifurcation theory mainly adopts the numerical continuation method. This method starts from the equilibrium solutions of known non-linear ordinary differential equations and extends the trajectory curves of all equilibrium solutions as the selected parameters change to find the bifurcation points. Using the numerical continuation method to solve the over-center mechanism, an S-shaped curve is obtained. On the stable region solution, even with small perturbations, the mechanism still converges to the stable angle; while within the unstable region solution, once any small perturbation appears, this unstable solution will immediately jump to the stable solution region. A saddle-node bifurcation occurs at the critical points between the stable region and the unstable region, which essentially clarifies the unstable jump problem of the strut-type locking mechanism and can quickly find the variation law of the stable motion trajectory within the entire range affected by multiple parameters, providing a practical and effective theoretical basis and design method for the parameter design of the landing gear mechanism.

[0004] However, the existing analysis methods only focus on rigid bodies and ideal hinges. When considering the effects of structural clearances, assembly deviations, and structural deformations, it is difficult to establish an accurate mathematical model, resulting in a difference between the theoretical model and the actual situation. Traditional test methods can only observe the jumping phenomenon through a high-speed camera but cannot obtain the bifurcation point position and the unstable branch. Summary of the Invention

[0005] The purpose of the present invention is to provide a bifurcated test device and method for a landing gear over-center mechanism based on control continuation to solve the above problems existing in the prior art. It can effectively combine feedback control to turn the unstable branch into a stable branch, and then achieve the global tracking of the mechanism motion trajectory and the bifurcation point, and obtain the most realistic stable branch and bifurcation point.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a landing gear over-center mechanism bifurcation test device based on control extension, comprising a test frame assembly, a feedback control system, and an over-center mechanism assembly;

[0008] The test frame assembly includes a test bench frame and a drive-end support bench frame and a linear guide rail support seat respectively installed at both ends of the test bench frame; the linear guide rail support seat includes a bottom plate, a truss, and a guide rail plate, the bottom plate is fixedly installed on the test bench frame, the truss is fixedly connected to the bottom plate, and the guide rail plate is fixedly installed on the truss;

[0009] The over-center mechanism assembly includes a first connecting rod, a second connecting rod, a slider, a linear guide rail, a tension spring, and a moving support seat; one end of the first connecting rod is connected to one end of the second connecting rod through a pin shaft, a plurality of first mounting holes are arranged at intervals on the first connecting rod, a plurality of second mounting holes are arranged at intervals on the second connecting rod, one end of the tension spring is connected to one of the first mounting holes through a mounting member, and the other end is connected to one of the second mounting holes through the mounting member. Each of the first mounting holes and the second mounting holes is also used for installing a counterweight to respectively adjust the centroid positions of the first connecting rod and the second connecting rod; the end of the second connecting rod away from the first connecting rod is rotatably connected to the shaft end of the moving support seat through a first bearing, the moving support seat is fixedly connected to the slider, the slider is slidably arranged on the linear guide rail, and the linear guide rail is fixedly installed on the guide rail plate;

[0010] The third mounting holes on the truss for installing the guide rail plate and the fourth mounting holes on the bottom plate for fixedly installing with the test bench frame are both oblong holes, and the oblong holes are used for adjusting the installation deviation of the over-center mechanism assembly;

[0011] The feedback control system includes a servo motor, a PLC control cabinet, a speed reducer, a transmission shaft, a dynamic torque sensor, a first angle sensor, and a second angle sensor; the servo motor is connected to the speed reducer, the speed reducer and the dynamic torque sensor are fixedly installed on the driving end support frame, one end of the dynamic torque sensor is connected to the output shaft of the speed reducer through a coupling, and the other end is connected to the transmission shaft through a coupling. The transmission shaft is rotatably connected to the bearing support through a second bearing, and the bearing support is fixedly installed on the driving end support frame. The transmission shaft passes through the second bearing and is fixedly connected to one end of the first connecting rod away from the second connecting rod; the rotating shaft of the first angle sensor is connected to the transmission shaft through a coupling, and the housing of the first angle sensor is fixed on the bearing support; the rotating shaft of the second angle sensor is connected to the shaft end of the moving support through a coupling, and the housing of the second angle sensor is fixed on the second connecting rod; the servo motor, the dynamic torque sensor, the first angle sensor, and the second angle sensor are all signal-connected to the PLC control cabinet, and the PLC control cabinet can drive the first connecting rod to rotate through the servo motor, and then drive the slider to slide along the linear guide through the second connecting rod.

[0012] Preferably, limit blocks are installed at both ends of the linear guide, and the limit blocks are wrapped with rubber shells.

[0013] Preferably, self-lubricating bushings are provided between the pin shaft and the pin shaft mounting holes of the first connecting rod and the second connecting rod.

[0014] Preferably, a motor support is fixedly installed on the driving end support frame, and the speed reducer is fixedly installed on the motor support.

[0015] Preferably, the mounting member is a lifting eye bolt, the first mounting hole and the second mounting hole are threaded holes, and the lifting eye bolt can be threadedly connected into the first mounting hole and the second mounting hole.

[0016] Preferably, the shaft ends of the dynamic torque sensor connected to the transmission shaft and the output shaft of the speed reducer are grooved and connected with flat keys. The shaft ends of the rotating shaft of the first angle sensor connected to the transmission shaft are grooved and connected with flat keys. The shaft ends of the rotating shaft of the second angle sensor connected to the moving support are grooved and connected with flat keys.

[0017] Preferably, the transmission shaft is connected to the transmission shaft mounting hole on the first connecting rod through a flat key. Tightening threaded holes are respectively provided on the first connecting rod on both sides of the transmission shaft mounting hole, and tightening screws are threadedly connected into the tightening threaded holes to tighten the transmission shaft.

[0018] The present invention also provides a method for the bifurcation test of the landing gear over-center mechanism based on control continuation. Using the above-mentioned device for the bifurcation test of the landing gear over-center mechanism based on control continuation, the method includes the following steps:

[0019] S1: Turn on the PLC control cabinet, so that the over-center mechanism formed by the first connecting rod and the second connecting rod rotates driven by the servo motor, and maintains balance at each angle within a specified angle range. Record the magnitude of the torque required for the over-center mechanism to maintain balance at each angle, and extend the change trajectory line of the balance torque of the over-center mechanism with the mechanism angle;

[0020] S2: Adjust the control program. After the over-center mechanism maintains balance at a specified angle, turn off the angle control, apply the balance torque corresponding to the angle, and observe the movement of the over-center mechanism;

[0021] S3: Within the specified angle range, repeat step S2;

[0022] S4: Adjust the control program. After the over-center mechanism maintains balance at a specified angle, turn off the angle control, apply a constant force other than the balance torque, and record the movement of the over-center mechanism at different release positions and different speeds;

[0023] S5: By adjusting the original length of the tension spring, the stiffness of the tension spring, the installation position of the tension spring, the installation position of the counterweight, the diameter of the pin shaft at the connection between the first connecting rod and the second connecting rod, the installation position of the bottom plate, and the installation height of the guide rail plate, and then repeating S1 - S4, conduct tests under different working conditions.

[0024] The present invention has achieved the following technical effects compared with the prior art:

[0025] The device for the bifurcation test of the landing gear over-center mechanism based on control continuation provided by the present invention enables the over-center mechanism to move following the instructions of the feedback control through the real-time feedback and precise drive of the electric control system, thereby ensuring the progress of the bifurcation analysis test of the over-center mechanism. The first mounting hole on the first connecting rod and the second mounting hole on the second connecting rod can be used to install the counterweight and the tension spring at different positions to simulate different centroid and spring installation position working conditions. Springs of multiple specifications are used to simulate different original spring lengths and spring stiffness working conditions. Adjusting the pin shaft diameter can simulate different structural clearance working conditions. The long circular holes on the bottom plate of the linear guide support and the truss can be used to adjust the installation position of the linear guide to simulate different installation deviation working conditions, and obtain the movement bifurcation characteristics of the over-center mechanism under the most realistic conditions.

[0026] The present invention provides a method for bifurcation test of the landing gear over-center mechanism based on control continuation. Aiming at the limitation problem that the bifurcation analysis method for the motion stability research of the complex landing gear mechanism in the past has large solution accuracy and actual deviation, a bifurcation analysis test device for the over-center mechanism based on control continuation is used. By switching the feedback control switch, the jumping process of the unstable point of the mechanism and the bifurcation topology change mechanism are explored. Through the feedback controller, the global tracking of the motion trajectory of the over-center mechanism in the physical test process is realized, the stability problem of the over-center mechanism is deeply studied, the effectiveness of the bifurcation analysis method based on control continuation applied to the stability analysis of the landing gear locking mechanism is verified, and a new bifurcation analysis method combining theory and experiment is formed, providing an important theoretical basis and technical support for the design of the complex landing gear mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic structural diagram of a strut-type locking mechanism in a landing gear and a structure simplified to an over-center mechanism in the prior art;

[0029] Figure 2 It is a schematic diagram of the locking process of the over-center mechanism;

[0030] Figure 3 It is a schematic diagram of the unlocking process of the over-center mechanism;

[0031] Figure 4 It is an overall installation schematic diagram of the landing gear over-center mechanism bifurcation test device based on control continuation provided by the present invention;

[0032] Figure 5 It is a schematic structural diagram of the over-center mechanism component in the present invention;

[0033] Figure 6 It is an installation structural schematic diagram of the feedback control system in the present invention;

[0034] Figure 7 It is a schematic structural diagram of the linear guide rail support in the present invention;

[0035] Figure 8 It is a logic diagram of the method for bifurcation test of the landing gear over-center mechanism based on control continuation provided by the present invention.

[0036] In the figure: 1 - test stand assembly, 2 - feedback control system, 3 - over-center mechanism assembly, 4 - test bench, 5 - drive-end support bench, 6 - bearing support, 7 - motor support, 8 - linear guide support, 9 - servo motor, 10 - PLC control cabinet, 11 - reducer, 12 - transmission shaft, 13 - dynamic torque sensor, 14 - first angle sensor, 15 - second angle sensor, 16 - first connecting rod, 17 - second connecting rod, 18 - slider, 19 - linear guide, 20 - tension spring, 21 - moving support, 22 - limit stop, 23 - counterweight, 24 - coupling, 25 - truss, 26 - bottom plate, 27 - guide plate, 28 - angle sensor fixture, 29 - first mounting hole, 30 - second mounting hole, 31 - mounting part, 32 - third mounting hole, 33 - fourth mounting hole, A - locked stable state, B - unlocked unstable state. Detailed implementation manners

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] The purpose of the present invention is to provide a landing gear over-center mechanism bifurcation test device based on control continuation and its test method to solve the problems existing in the prior art, which can effectively combine feedback control to change the unstable branch into a stable branch, and then realize the global tracking of the mechanism motion trajectory and bifurcation point, and obtain the most real stable branch and bifurcation point.

[0039] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0040] As Figures 4 - 8 shown, this embodiment provides a landing gear over-center mechanism bifurcation test device based on control continuation, which is mainly used to study the bifurcation characteristics of the over-center mechanism and explore the feasibility of applying the bifurcation analysis method based on control continuation to the research of the landing gear strut lock mechanism, and provide a theoretical basis for the design of the landing gear strut lock mechanism, including a test stand assembly 1, a feedback control system 2, and an over-center mechanism assembly 3; the over-center mechanism assembly 3 can move under the drive of the feedback control system 2 to ensure the test effect;

[0041] The test stand assembly 1 includes a test bench 4, and a driving end support stand 5 and a linear guide rail support 8 respectively installed at both ends of the test bench 4; the linear guide rail support 8 includes a bottom plate 26, a truss 25 and a guide rail plate 27. The bottom plate 26 is fixedly installed on the test bench 4, the truss 25 is fixedly connected to the bottom plate 26 by welding, and the guide rail plate 27 is fixedly installed on the truss 25;

[0042] The over-center mechanism assembly 3 includes a first connecting rod 16, a second connecting rod 17, a slider 18, a linear guide rail 19, a tension spring 20 and a moving support 21; one end of the first connecting rod 16 is connected to one end of the second connecting rod 17 through a pin shaft. A plurality of first mounting holes 29 are arranged at intervals on the first connecting rod 16, and a plurality of second mounting holes 30 are arranged at intervals on the second connecting rod 17. One end of the tension spring 20 is connected to one of the first mounting holes 29 through a mounting member 31, and the other end is connected to one of the second mounting holes 30 through the mounting member 31. Each of the first mounting holes 29 and the second mounting holes 30 is also used for installing a counterweight 23 to respectively adjust the centroid positions of the first connecting rod 16 and the second connecting rod 17; the end of the second connecting rod 17 far from the first connecting rod 16 is rotatably connected to the shaft end of the moving support 21 through a first bearing to reduce friction. The moving support 21 is fixedly connected to the slider 18 by screws. The slider 18 is slidably arranged on the linear guide rail 19. The linear guide rail 19 is coated with grease to reduce friction. The linear guide rail 19 is fixedly installed on the guide rail plate 27;

[0043] The third mounting hole 32 on the truss 25 for installing the guide rail plate 27 and the fourth mounting hole 33 on the bottom plate 26 for fixedly installing with the test bench 4 are both oblong holes. The guide rail plate 27 is fixed on the oblong hole of the truss 25 by bolts and the height can be adjusted up and down. The bottom plate 26 is fixed on the test bench 4 by bolts and the distance along the oblong hole direction can be adjusted. The oblong holes are used to adjust the installation deviation of the over-center mechanism assembly 3 to simulate different installation deviation working conditions;

[0044] The feedback control system 2 includes a servo motor 9, a PLC control cabinet 10, a speed reducer 11, a transmission shaft 12, a dynamic torque sensor 13, a first angle sensor 14 and a second angle sensor 15; the servo motor 9 is connected to the speed reducer 11, the speed reducer 11 and the dynamic torque sensor 13 are fixedly installed on the driving end support frame 5, one end of the dynamic torque sensor 13 is connected to the output shaft of the speed reducer 11 through a coupling 24, and the other end is connected to the transmission shaft 12 through a coupling 24 to measure and output the torque of the transmission shaft 12 in real time. The transmission shaft 12 is rotatably connected to the bearing support 6 through a second bearing. A positioning hole is provided in the bearing support 6, and a second bearing is installed in the hole to support the transmission shaft 12 and ensure the transmission efficiency of the transmission shaft 12. The bearing support 6 is fixedly installed on the driving end support frame 5. The transmission shaft 12 passes through the second bearing and is fixedly connected to one end of the first connecting rod 16 away from the second connecting rod 17; the rotating shaft of the first angle sensor 14 is connected to the transmission shaft 12 through a coupling, and the housing of the first angle sensor 14 is fixed to the bearing support 6 through an angle sensor clamp 28 to measure and output the angle of the first connecting rod 16 in real time; the rotating shaft of the second angle sensor 15 is connected to the shaft end of the moving support 21 through a coupling, and the housing of the second angle sensor 15 is fixed to the second connecting rod 17 through a clamp to measure and output the angle of the second connecting rod 17 in real time; the servo motor 9, the dynamic torque sensor 13, the first angle sensor 14 and the second angle sensor 15 are all signal-connected to the PLC control cabinet 10. The PLC control cabinet 10 can drive the first connecting rod 16 to rotate through the servo motor 9, and then drive the slider 18 to slide along the linear guide 19 through the second connecting rod 17.

[0045] Through the real-time feedback and precise drive of the electric control system, this device enables the over-center mechanism to move following the instructions of the feedback control, thereby ensuring the progress of the over-center mechanism bifurcation analysis test. The first mounting hole 29 on the first connecting rod 16 and the second mounting hole 30 on the second connecting rod 17 can be used to install counterweights 23 and tension springs 20 at different positions to simulate different centroid and spring installation position conditions. Springs of multiple specifications are used to simulate different spring original lengths and spring stiffness conditions. Adjusting the pin diameter at the connection of the first connecting rod 16 and the second connecting rod 17 can simulate different structural clearance conditions. The long circular holes on the bottom plate 26 of the linear guide support 8 and the truss 25 can be used to adjust the installation position of the linear guide 19 to simulate different installation deviation conditions, and obtain the over-center mechanism motion bifurcation characteristics under the most realistic conditions.

[0046] In this embodiment, limit blocks 22 are installed at both ends of the linear guide 19 to prevent the slider 18 from detaching from the linear guide 19 during movement, ensuring the safety of the test. The limit blocks 22 are wrapped with rubber shells to prevent damage to the slider 18.

[0047] In this embodiment, a self-lubricating bushing is provided between the pin shaft and the pin mounting holes of the first connecting rod 16 and the second connecting rod 17 to reduce friction.

[0048] In this embodiment, a motor support 7 is fixedly installed on the driving end support frame 5, and the speed reducer 11 is fixedly installed on the motor support 7. During use, the test bench 4 is fixed to the ground to improve the stability of the entire device during the test. The driving end support frame 5 and the linear guide support 8 are fixed to the test bench 4 by bolts, the bearing support 6 and the motor support 7 are fixed to the driving end support frame 5 by bolts, and the heights of the driving end support frame 5, the bearing support 6, and the motor support 7 ensure that the over-center mechanism assembly 3 does not contact the test bench 4 during rotation, ensuring the stability of the over-center mechanism assembly 3 during movement. The output shaft of the servo motor 9 is inserted into the speed reducer 11 and the corresponding mounting holes are connected by bolts externally. The speed reducer 11 is fixed to the motor support 7 by bolts, and the dynamic torque sensor 13 is fixed to the driving end support frame 5 by bolts. The positioning holes provided in the motor support 7 and the bearing support 6 ensure the coaxial connection of the output shaft of the speed reducer 11, the transmission shaft of the dynamic torque sensor 13, and the transmission shaft 12, ensuring the transmission efficiency and measurement accuracy.

[0049] In this embodiment, the mounting member 31 is a lifting eye bolt, the first mounting hole 29 and the second mounting hole 30 are threaded holes, five first mounting holes 29 are provided on the first connecting rod 16, five second mounting holes 30 are provided on the second connecting rod 17, and the lifting eye bolt can be threadedly connected into the first mounting hole 29 and the second mounting hole 30. Both ends of the tension spring 20 are connected to the first connecting rod 16 and the second connecting rod 17 respectively through the lifting eye bolt, and different spring installation position conditions can be simulated by changing the installation position of the lifting eye bolt.

[0050] In this embodiment, the shaft ends where the dynamic torque sensor 13 is connected to the transmission shaft 12 and the output shaft of the speed reducer 11 are all grooved and connected by flat keys. The shaft ends where the rotating shaft of the first angle sensor 14 is connected to the transmission shaft 12 are all grooved and connected by flat keys. The shaft ends where the rotating shaft of the second angle sensor 15 is connected to the moving support 21 are all grooved and connected by flat keys, ensuring the transmission efficiency and measurement accuracy.

[0051] In this embodiment, the transmission shaft 12 is connected to the transmission shaft mounting hole on the first connecting rod 16 by a flat key. One tightening threaded hole is provided on each side of the transmission shaft mounting hole on the first connecting rod 16, and a tightening screw is threadedly connected into each tightening threaded hole to tighten the transmission shaft 12, ensuring the transmission efficiency.

[0052] A method for testing the bifurcation of the landing gear over-center mechanism based on control continuation uses the above-mentioned test device for testing the bifurcation of the landing gear over-center mechanism based on control continuation, and includes the following steps:

[0053] S1: Turn on the PLC control cabinet 10, so that the over-center mechanism formed by the first connecting rod 16 and the second connecting rod 17 rotates driven by the servo motor 9, and maintains balance at each angle within the specified angle range. Record the magnitude of the torque required for the over-center mechanism to maintain balance at each angle, and extend the change trajectory line of the balance torque of the over-center mechanism with the mechanism angle.

[0054] S2: Adjust the control program. After the over-center mechanism maintains balance at the specified angle, turn off the angle control, apply the balance torque corresponding to the angle, and observe the motion of the over-center mechanism.

[0055] S3: Repeat step S2 within the specified angle range.

[0056] S4: Adjust the control program. After the over-center mechanism maintains balance at the specified angle, turn off the angle control, apply a constant force other than the balance torque, and record the motion of the over-center mechanism at different release positions and different speeds.

[0057] S5: By adjusting the original length of the tension spring 20, the stiffness of the tension spring 20, the installation position of the tension spring 20, the installation position of the counterweight 23, the diameter of the pin shaft at the connection of the first connecting rod 16 and the second connecting rod 17, the installation position of the bottom plate 26, and the installation height of the guide rail plate 27, repeat S1 - S4 to conduct tests under different working conditions.

[0058] This method uses the above-mentioned test device for bifurcation analysis of the over-center mechanism based on control extension. By switching the feedback control switch, it explores the mechanism instability point jumping process and the bifurcation topology change mechanism. Through the feedback controller, it realizes the global tracking of the motion trajectory of the over-center mechanism in the physical test process, deeply studies the stability problem of the over-center mechanism, verifies the effectiveness of the bifurcation analysis method based on control extension applied to the stability analysis of the landing gear locking mechanism, forms a new bifurcation analysis method combining theory and experiment, and provides an important theoretical basis and technical support for the design of complex landing gear mechanisms.

[0059] In the present invention, specific examples are used to elaborate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A landing gear over-center mechanism bifurcation test device based on control extension, characterized in that: It includes a test stand assembly, a feedback control system, and an over-center mechanism assembly; The test stand assembly includes a test bench and a drive-end support bench and a linear guide rail support installed at both ends of the test bench respectively; the linear guide rail support includes a bottom plate, a truss, and a guide rail plate. The bottom plate is fixedly installed on the test bench, the truss is fixedly connected to the bottom plate, and the guide rail plate is fixedly installed on the truss; The over-center mechanism assembly includes a first connecting rod, a second connecting rod, a slider, a linear guide rail, a tension spring, and a moving support; one end of the first connecting rod is connected to one end of the second connecting rod through a pin shaft. A plurality of first mounting holes are spaced on the first connecting rod, and a plurality of second mounting holes are spaced on the second connecting rod. One end of the tension spring is connected to one of the first mounting holes through a mounting member, and the other end is connected to one of the second mounting holes through the mounting member. Each of the first mounting holes and the second mounting holes is also used to install counterweights to adjust the centroid positions of the first connecting rod and the second connecting rod respectively; the end of the second connecting rod away from the first connecting rod is rotatably connected to the shaft end of the moving support through a first bearing. The moving support is fixedly connected to the slider, and the slider is slidably arranged on the linear guide rail. The linear guide rail is fixedly installed on the guide rail plate; The third mounting holes on the truss for installing the guide rail plate and the fourth mounting holes on the bottom plate for fixedly installing with the test bench are both oblong holes, and the oblong holes are used to adjust the installation deviation of the over-center mechanism assembly; The feedback control system includes a servo motor, a PLC control cabinet, a reducer, a transmission shaft, a dynamic torque sensor, a first angle sensor, and a second angle sensor; the servo motor is connected to the reducer. The reducer and the dynamic torque sensor are fixedly installed on the drive-end support bench. One end of the dynamic torque sensor is connected to the output shaft of the reducer through a coupling, and the other end is connected to the transmission shaft through a coupling. The transmission shaft is rotatably connected to a bearing support through a second bearing. The bearing support is fixedly installed on the drive-end support bench. The transmission shaft passes through the second bearing and is fixedly connected to the end of the first connecting rod away from the second connecting rod; the rotating shaft of the first angle sensor is connected to the transmission shaft through a coupling, and the housing of the first angle sensor is fixed on the bearing support; the rotating shaft of the second angle sensor is connected to the shaft end of the moving support through a coupling, and the housing of the second angle sensor is fixed on the second connecting rod; the servo motor, the dynamic torque sensor, the first angle sensor, and the second angle sensor are all signal-connected to the PLC control cabinet. The PLC control cabinet can drive the first connecting rod to rotate through the servo motor, and then drive the slider to slide along the linear guide rail through the second connecting rod.

2. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, characterized in that: Limit blocks are installed at both ends of the linear guide rail, and the limit blocks are wrapped with rubber shells.

3. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, characterized in that: A self-lubricating bushing is provided between the pin shaft and the pin shaft mounting holes of the first connecting rod and the second connecting rod.

4. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, characterized in that: A motor support is fixedly installed on the driving end support frame, and the reducer is fixedly installed on the motor support.

5. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, wherein: The mounting member is a lifting eye bolt, the first mounting hole and the second mounting hole are threaded holes, and the lifting eye bolt can be threadedly connected into the first mounting hole and the second mounting hole.

6. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, characterized in that: Both shaft ends where the dynamic torque sensor is interconnected with the transmission shaft and the output shaft of the reducer are grooved and connected by flat keys. Both shaft ends where the rotating shaft of the first angle sensor is interconnected with the transmission shaft are grooved and connected by flat keys. Both shaft ends where the rotating shaft of the second angle sensor is interconnected with the moving support are grooved and connected by flat keys.

7. The landing gear over-center mechanism bifurcation test device based on control extension according to claim 1, characterized in that: The transmission shaft is connected to the transmission shaft mounting hole on the first connecting rod by a flat key. One tightening threaded hole is respectively provided on the first connecting rod on both sides of the transmission shaft mounting hole, and a tightening screw is threadedly connected into each tightening threaded hole to tighten the transmission shaft.

8. A method for conducting a bifurcation test on a landing gear over-center mechanism based on control extension, characterized in that Using the landing gear over-center mechanism bifurcation test device based on control continuation according to any one of claims 1 to 7, comprising the following steps: S1: Turn on the PLC control cabinet, so that the over-center mechanism formed by the first connecting rod and the second connecting rod rotates under the drive of the servo motor, and remains balanced at each angle within a specified angle range, record the magnitude of the torque required for the over-center mechanism to remain balanced at each angle, and extend the change trajectory line of the balance torque of the over-center mechanism with the mechanism angle; S2: Adjust the control program. After the over-center mechanism remains balanced at a specified angle, turn off the angle control, apply the balance torque corresponding to the angle, and observe the movement of the over-center mechanism; S3: Repeat step S2 within the specified angle range; S4: Adjust the control program. After the over-center mechanism remains balanced at a specified angle, turn off the angle control, apply a constant force other than the balance torque, and record the movement of the over-center mechanism at different release positions and different speeds; S5: By adjusting the original length of the tension spring, the stiffness of the tension spring, the installation position of the tension spring, the installation position of the counterweight, the diameter of the pin shaft at the connection of the first connecting rod and the second connecting rod, the installation position of the bottom plate, and the installation height of the guide rail plate, and then repeat S1 - S4 to conduct tests under different working conditions.

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