A vehicle door stepless suspension system, vehicle and method based on magnetorheological fluid

Abstract

The present invention relates to the field of vehicle door technology, and discloses a system, vehicle, and method for steplessly suspending a vehicle door based on magnetorheological fluid. The system comprises a housing, a piston rod, a coil, a signal acquisition module, and a current control module. One end of the housing is provided with an opening communicating with a cavity, and the cavity is filled with magnetorheological fluid. One end of the piston rod extends into the cavity through the opening; the piston rod is fixed to the vehicle door, and the housing is fixed to the vehicle body, and can slide relative to each other as the vehicle door rotates. The opening is also provided with a seal to prevent leakage of the liquid. The coil is wound around the exterior of the housing and is used to provide a magnetic field to the magnetorheological fluid in the cavity when energized. The signal acquisition module is used to collect a response signal in real time. The current control module is used to adjust the input current of the coil based on the response signal and in accordance with a preset control strategy, thereby adjusting the damping force exerted on the piston rod by the magnetorheological fluid in the cavity to achieve rotatable or stepless suspension of the vehicle door.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle doors, and in particular to a vehicle door stepless suspension system, a vehicle and a method based on magnetorheological fluid. Background Art

[0002] Traditional door hover systems are designed to stabilize the door at a certain position after opening to a certain angle, preventing it from closing automatically due to gravity or other external forces. This design has several preset hovering positions, known as "three-level hovering." Building on this, researchers have developed a door system that can hover at any position with stepless limits, achieving both assisted door opening and closing and stepless hovering. For example, a mechanical brake connected to a drive mechanism achieves door hovering through frictional resistance. When the drive mechanism stops, the friction provided by the brake impedes the movement of the drive rod, keeping the door hovering at the preset angle. Another approach uses an electric drive to control door movement. Upon receiving a hovering command, the motor decelerates, and an electromagnetic brake provides a hovering force to maintain the door. These technologies are complex and rely on friction to maintain the door in a hovering position. With repeated use, the friction surface becomes smooth and may not provide sufficient force, resulting in a weakening of the hovering effect. Summary of the Invention

[0003] In order to solve the technical problems in the existing vehicle door stepless hovering technology, such as poor hovering effect and limited system service life due to friction loss of mechanical components, the present invention provides a vehicle door stepless hovering system, vehicle and method based on magnetorheological fluid.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The invention discloses a vehicle door stepless suspension system based on magnetorheological fluid, comprising a housing, a piston rod, a coil, a signal acquisition module and a current control module.

[0006] One end of the shell is provided with an opening communicating with a cavity inside the shell, and the cavity is filled with magnetorheological fluid.

[0007] One end of the piston rod extends into the cavity through the opening; one of the piston rod and the housing is fixedly mounted on the vehicle door, and the other is fixedly mounted on the vehicle body, and the piston rod and the housing can slide relative to each other as the vehicle door rotates, and a seal is also provided at the opening to prevent leakage of magnetorheological fluid.

[0008] The coil is wound around the exterior of the housing and is used to provide a magnetic field to the magnetorheological fluid in the cavity when power is supplied.

[0009] The signal acquisition module is used to collect the response signal reflecting the door status in real time.

[0010] The current control module is used to adjust the input current of the coil according to the response signal and a preset control strategy, thereby adjusting the damping force generated by the magnetorheological fluid in the cavity on the piston rod to achieve rotation or stepless hovering of the car door.

[0011] As a further improvement of the above scheme, the signal acquisition module includes a pressure acquisition unit and an angle acquisition unit; the pressure acquisition unit is installed on the handle of the vehicle door and is used to collect a first signal reflecting the force F1 on the handle; the angle acquisition unit is used to collect a second signal reflecting the opening and closing angle C1 of the vehicle door.

[0012] As a further improvement of the above solution, the control strategy is as follows:

[0013] Determine whether the door opening and closing angle C1 is within a preset initial angle value C0. If so, the door is considered closed, and the current control module is in a non-operating state, without performing any control operations. Otherwise, the door is considered open, and the current control module enters an operating state. It analyzes the changes in F1 and C1 and makes the following decisions:

[0014] When F1 ≥ F0, the rotatable mode is activated and the input current of the coil is adjusted to 0; where F0 is the preset upper limit of the force;

[0015] When F1<F0 and C1 remains unchanged within a preset time threshold t, the hovering mode is activated and the input current of the coil is adjusted to a preset first current threshold I1;

[0016] In the hovering mode, if the change value of C1 exceeds a preset upper limit of angle change and F1 remains unchanged, the input current of the coil is adjusted to a preset second current threshold value I2; wherein 0<I1<I2.

[0017] As a further improvement of the above solution, the hovering system further includes: a connecting piece.

[0018] The connecting piece has a tubular structure and one end is inserted into the opening; the cross-section of the outer wall of the connecting piece and the cross-section projection of the inner wall of the outer shell match each other, and the two are relatively fixed; a first sealing ring is provided between the connecting piece and the outer shell to achieve one-way sealing; the cross-section of the inner wall of the connecting piece and the cross-section projection of the piston rod match each other, and the two are in sliding contact; three fixed second sealing rings are arranged on the inner wall of the connecting piece at intervals along the sliding direction to achieve two-way sealing.

[0019] As a further improvement of the above solution, the housing, the connecting piece and the piston rod are all arc-shaped along the extension direction and have circular cross-sections.

[0020] As a further improvement of the above solution, a section of the piston rod extending into the cavity is an extending section, and a gap for allowing the magnetorheological fluid to flow exists between the circumferential outer edge of the extending section and the circumferential inner wall of the shell.

[0021] As a further improvement of the above scheme, the end of the extension section is integrally connected with a first disc; the projected area of ​​the circumferential outer edge of the first disc is larger than the projected area of ​​the circumferential outer edge of the extension section; there is at least one first disc, and when there are multiple first discs, they are distributed in sequence along the extension direction of the extension section; the first disc is provided with at least one guide hole parallel to the extension direction of the extension section along the circumferential direction.

[0022] As a further improvement of the above solution, a second disc is integrally connected to the middle portion of the outer wall of the connector, and the end face of the second disc and the end face of the outer shell are fixedly connected by a plurality of screws.

[0023] The present invention also discloses a vehicle, comprising a vehicle body and a vehicle door, and also comprising the above-mentioned vehicle door stepless suspension system.

[0024] The present invention further discloses a method for steplessly suspending a vehicle door based on magnetorheological fluid, which is applied to the above-mentioned steplessly suspending system for the vehicle door. The method includes the following steps S1 to S2.

[0025] S1. Real-time collection of response signals reflecting the state of the vehicle door, wherein the response signals include a first signal reflecting the force F1 on the handle and a second signal reflecting the opening and closing angle C1 of the vehicle door.

[0026] S2. Determine whether the door opening angle C1 is within a preset initial angle value C0. If so, the door is considered closed, and the current control module is inactive, performing no control operations. Otherwise, the door is considered open, and the current control module enters active mode. It analyzes the changes in F1 and C1 and makes the following decisions:

[0027] When F1 ≥ F0, the rotatable mode is activated and the input current of the coil is adjusted to 0; where F0 is the preset upper limit of the force;

[0028] When F1<F0 and C1 remains unchanged within a preset time threshold t, the hovering mode is activated and the input current of the coil is adjusted to a preset first current threshold I1;

[0029] In the hovering mode, if the change value of C1 exceeds a preset upper limit of angle change and F1 remains unchanged, the input current of the coil is adjusted to a preset second current threshold value I2; wherein 0<I1<I2.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention utilizes magnetorheological fluid for stepless door hovering. The fluid's viscosity can be precisely adjusted based on the external electromagnetic field, providing precise hovering force for the door hovering system. Combined with door information collection and electronic control, the system dynamically adjusts the input current, magnetic field strength, and viscosity of the magnetorheological fluid to adjust the door hovering force, achieving intelligent adjustment and control of the door hovering mode. Stepless hovering allows the door to stop at different opening angles, improving comfort and convenience while reducing friction losses in mechanical transmission components and extending the life of the hovering system.

[0032] 2. The present invention utilizes multiple sealing rings for bidirectional sealing between the connector and the piston rod, and a single sealing ring for unidirectional sealing between the connector and the housing. These two sealing methods effectively reduce leakage of magnetorheological fluid from the piston rod during feeding. The use of screws and gaskets ensures a tight mechanical connection between the housing and the connector, enhancing the stability and strength of the connection. This connection can withstand the vibration and forces of equipment operation, preventing malfunctions and damage caused by loosening. This also makes installation and maintenance of the hovering system more convenient and efficient, reducing maintenance complexity and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the three-dimensional structure of a vehicle door stepless suspension system based on magnetorheological fluid in an embodiment of the present invention.

[0034] Figure 2 for Figure 1 Schematic cross-sectional view of the center door's stepless hovering system from the main perspective.

[0035] Figure 3 Schematic diagram of the relative position of the piston rod submerged in the magnetorheological fluid in the cavity in an embodiment of the present invention.

[0036] Figure 4 This is a structural diagram of an embodiment of the present invention in which the extending section of the piston rod is provided with a plurality of first discs.

[0037] Figure 5 Schematic diagram of the interaction among the signal acquisition module, current control module and coil in an embodiment of the present invention.

[0038] Figure 6 Schematic diagram of the arrangement of the pressure collection unit on the door handle in an embodiment of the present invention.

[0039] Figure 7 Schematic diagram of the logic of the method for stepless suspension of a vehicle door based on magnetorheological fluid in an embodiment of the present invention.

[0040] In the figure: 1. Shell; 11. Opening; 12. Cavity; 2. Piston rod; 21. First disc; 210. Diversion hole; 3. Coil; 4. Signal acquisition module; 41. Pressure acquisition unit; 411. Inner pressure sensor; 412. Outer pressure sensor; 42. Angle acquisition unit; 5. Current control module; 6. Connector; 62. Second disc; 71. First sealing ring; 72. Second sealing ring; 8. Screw. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] See also Figures 1 to 3 This embodiment provides a stepless suspension system for a vehicle door based on magnetorheological fluid, including: a housing 1, a piston rod 2, a coil 3, a signal acquisition module 4 and a current control module 5, and may also include a connector 6.

[0043] In this embodiment, the housing 1, connector 6, and piston rod 2 can all be curved along their extension direction, corresponding to the rotation angle of the vehicle door on the vehicle body. The housing 1, connector 6, and piston rod 2 can all have circular cross-sections. Of course, in other embodiments, they can also be linear along their extension direction, similar to a linear cylinder or hydraulic cylinder, with some transmission device (e.g., a multi-link) driving the piston rod 2 to perform linear motion using the rotation of the vehicle door.

[0044] One end of the housing 1 is provided with an opening 11 communicating with a cavity 12 inside the housing, and the other end is a closed end. The cavity 12 is filled with magnetorheological fluid.

[0045] Magnetorheological fluids are a new type of fluid with controllable flow properties. In the absence of an external magnetic field, magnetic particles are randomly suspended in a base fluid, behaving as a linearly viscous Newtonian fluid, indistinguishable from a conventional hydraulic suspension. However, under the influence of an external magnetic field, they can transform from a low-viscosity Newtonian fluid to a higher-viscosity semi-solid within a short period of time (10 milliseconds), a phenomenon known as the magnetorheological effect. Magnetorheological fluids can achieve continuous, reversible transitions from liquid to near-solid state within milliseconds, with their viscosity increasing with increasing magnetic field strength.

[0046] One end of the piston rod 2 extends through opening 11 into the cavity 12, fully contacting the magnetorheological fluid. The portion of the piston rod 2 that extends into the cavity 12 is the insertion section. In this embodiment, the housing 1 is fixedly mounted to the vehicle body, and the piston rod 2 is fixedly mounted to the vehicle door. In other embodiments, the mounting locations of the housing 1 and piston rod 2 can be reversed. The piston rod 2 and housing 1 can slide relative to each other as the vehicle door rotates. A seal is also provided at the opening 11 to prevent leakage of the magnetorheological fluid.

[0047] It should be noted that, in addition to being filled with magnetorheological fluid, the cavity 12 is also filled with a certain amount of air. The amount of magnetorheological fluid filled in the cavity 12 can be determined based on the volume occupied by the extended section of the piston rod 2 when it is fully extended into the cavity 12. When the extended section is fully extended into the cavity 12, the magnetorheological fluid needs to submerge the piston rod 2 as much as possible. Figure 3 As shown ( Figure 3 In the figure, A represents the boundary between the magnetorheological fluid and the air), which ensures that when a magnetic field is provided to the magnetorheological fluid, sufficient damping force is provided to the piston rod 2, while ensuring that the magnetorheological fluid is not expelled from the cavity 12 during the movement of the piston rod 2 in the cavity 12.

[0048] Connector 6 is tubular in structure, with one end inserted into opening 11. The cross-section of the outer wall of connector 6 matches the cross-section of the inner wall of housing 1, and the two are relatively fixed. In this embodiment, a second disc 62 is integrally connected to the middle of the outer wall of connector 6. The end surface of second disc 62 and the end surface of housing 1 can be fixedly connected by multiple screws 8. Washers can be placed between screws 8 and second disc 62 to ensure the tightness of the threaded fit.

[0049] A first sealing ring 71 is provided between the connector 6 and the housing 1 to achieve a one-way seal, preventing leakage of the magnetorheological fluid from the gap between the connector 6 and the housing 1. Of course, in other embodiments, the connector 6 and the housing 1 can also be integrally formed, which further ensures the reliability of the seal. The cross-section of the inner wall of the connector 6 and the cross-sectional projection of the piston rod 2 coincide with each other, and the two are in sliding contact. Three fixed second sealing rings 72 are provided at intervals along the sliding direction on the inner wall of the connector 6 to achieve a two-way seal, thereby preventing leakage of the magnetorheological fluid when the piston rod 2 is pushed outward from the cavity 12, and preventing external contaminants from entering the cavity 12 when the piston rod 2 is pushed into the cavity 12.

[0050] There is a gap between the outer circumference of the extension section and the inner circumference of the housing 1 for the flow of magnetorheological fluid, which does not affect the flow exchange of the magnetorheological fluid when the extension section moves in the cavity 12. The end of the extension section is integrally connected to a first disk 21; the outer circumference projected area of ​​the first disk 21 is larger than the outer circumference projected area of ​​the extension section. Figure 4As shown, in some embodiments, the first disc 21 can also be configured as other shapes, and the number of first discs 21 can also be configured as multiple. Multiple first discs 21 are spaced apart along the extension direction at the end of the extension section to form a structure similar to an insulator. This can increase the contact area of ​​the piston rod 2 with the magnetorheological fluid (for example, in an anchor shape); the first disc 21 can be provided with six guide holes 210 pointing to the gap along the circumferential direction. By providing the first disc 21, the magnetorheological fluid can remain near the front and back surfaces of the first disc 21. The first disc 21 increases the force-bearing area compared to the end face of the piston rod 2. When the magnetorheological fluid is subjected to the magnetic field to produce a magnetorheological effect, the damping force on the entire piston rod 2 can be increased. At the same time, the guide holes 210 can facilitate the flow of the magnetorheological fluid when no magnetic field is applied.

[0051] It should be noted that Figure 1 and Figure 2 The piston rod 2 is only for illustration. In actual application, the extending section of the piston rod 2 can be set to a relatively thin rod body (such as Figure 3 and Figure 4 As shown, for example, the cross-sectional ratio of the piston rod 2 to the cavity 12 is set to 1:5. Because the anchor-shaped first disc 21 is the primary source of the damping force, this is sufficient as long as the structural strength of the piston rod 2 itself meets the required requirements. This prevents significant resistance from compressing the air within the cavity during advancement into the cavity 12. In some embodiments, after the various components of the system are assembled, a vacuum can be employed to reduce the pressure within the cavity 12 to slightly below atmospheric pressure. This also prevents significant resistance from being encountered by the piston rod 2 during advancement into the cavity 12, thereby ensuring smooth and normal opening and closing of the door.

[0052] Coil 3 is wound around the exterior of housing 1 and is used to generate a magnetic field for the magnetorheological fluid in cavity 12 when current is applied. Coil 3 can be connected to the vehicle body's electrical system via a wire. When current is applied to the wire, a magnetic field is generated around coil 3. The strength of the magnetic field is related to the input current and the number of turns of coil 3. For a fixed number of turns of coil 3, the greater the input current, the greater the magnetic field strength. Furthermore, piston rod 2, acting as an iron core, enhances the magnetic field strength.

[0053] See also Figure 5 The signal acquisition module 4 is used to acquire a response signal reflecting the state of the vehicle door in real time. In this embodiment, the signal acquisition module 4 may include a pressure acquisition unit 41 and an angle acquisition unit 42.

[0054] The pressure collection unit 41 is installed on the handle of the vehicle door and is used to collect a first signal reflecting the force F1 applied to the handle.

[0055] See also Figure 6The pressure acquisition unit 41 may include at least two pressure sensors, placed at appropriate locations on the inside and outside of the door handle. Typically, when a user grasps the door handle to open it (pulling the handle), the inner pressure sensor 411 is pressed, generating an electrical signal. When the user closes the door (pushing the handle), the outer pressure sensor 412 is pressed, generating an electrical signal. Regardless of which pressure sensor generates the electrical signal, the pressure acquisition unit 41 uses it to collect the first signal, as the signal's sole function is to determine whether the user is grasping the door handle.

[0056] Angle acquisition unit 42 is used to collect a second signal reflecting the door's opening and closing angle C1. Angle acquisition unit 42 can employ a photoelectric sensor or a Hall effect sensor, installed near the door's hinge, to monitor the door's opening and closing angle. Those skilled in the art can customize this arrangement based on common technical knowledge, and detailed description is omitted here. In some embodiments, the door's opening and closing angle C1 can also be directly acquired from the vehicle's factory-installed door angle monitoring unit.

[0057] The pressure acquisition unit 41 and the angle acquisition unit 42 can periodically report their status to the current control module 5 (once every 400ms).

[0058] The current control module 5 is used to adjust the input current of the coil 3 according to the response signal and a preset control strategy, thereby adjusting the damping force generated by the magnetorheological fluid in the cavity 12 on the piston rod 2 to achieve rotatable or stepless hovering of the car door.

[0059] The current control module 5 is an electronic device including a current amplifier, a memory, a processor, and a computer program stored in the memory.

[0060] The control strategy is as follows:

[0061] Determine whether the door opening and closing angle C1 is at a preset initial angle value C0.

[0062] Non-working state: when the door opening and closing angle C1 is at a preset initial angle value C0, it is determined that the door is completely closed, and the current control module 5 is in a low-power standby state and does not perform any control operation.

[0063] Working state: If the door opening and closing angle C1 is not at a preset initial angle value C0, the door is determined to be open, and the current control module 5 is activated and enters the working state. It starts to analyze the changes in F1 and C1 and makes the following decisions:

[0064] ① Rotatable Mode: When the door handle is in an operational state (such as being pulled or pushed), indicating that the user wishes to change the door's opening or closing state, the current control module determines whether F1 ≥ F0. If so, the current control module activates the rotatable mode, adjusting the input current to coil 3 to 0. F0 is the preset upper force limit. At this point, the magnetorheological fluid is in a low viscosity state, and the damping force on piston rod 2 is negligible, allowing the door to open and close easily.

[0065] ② Hovering mode: When the door needs to be held in a specific position (such as a half-open state) and the user wishes to hover the door, they release the door handle. A determination is then made as to whether F1 < F0 and C1 remains constant for a preset time threshold t. If so, the hovering mode is initiated, and the input current to coil 3 is adjusted to a preset first current threshold I1, generating a strong magnetic field within coil 3. Under the action of this magnetic field, the ferromagnetic particles in the magnetorheological fluid rapidly arrange themselves into chain-like or columnar structures, causing the fluid viscosity to increase dramatically. At this point, the magnetorheological fluid transforms from a low-viscosity Newtonian fluid to a high-viscosity semisolid state. The high-viscosity magnetorheological fluid exerts a significant damping force on piston rod 2, hindering door rotation. The door enters a hovering state, where rotation must overcome the damping force of the magnetorheological fluid on piston rod 2. Once the door reaches the desired position and remains hovering, the current control module 5 maintains the current intensity in coil 3 constant, ensuring that the magnetorheological fluid maintains its high viscosity and continues to exert a damping force on piston rod 2.

[0066] The magnitude of this damping force can be controlled by adjusting the magnetic field strength and the composition of the magnetorheological fluid, thereby achieving precise hovering of the car door at any position.

[0067] In the hovering mode, the current control module 5 continuously monitors the door rotation angle and handle force. If it detects a slight change in door position—that is, a change in C1 exceeding a preset angle change limit while F1 remains unchanged—the current amplifier increases the input current to coil 3, adjusting it to a preset second current threshold, I2, where 0 < I1 < I2. This further enhances the damping force and improves the door's resistance to gravity, wind, or other external forces.

[0068] This embodiment also provides a vehicle, which includes a vehicle body, vehicle doors, and the above-mentioned vehicle door stepless suspension system.

[0069] See also Figure 7 This embodiment also provides a method for stepless suspension of a vehicle door based on magnetorheological fluid, which is applied to the above-mentioned stepless suspension system of the vehicle door. The method includes the following steps S1 to S2.

[0070] S1. Real-time collection of response signals reflecting the state of the vehicle door, wherein the response signals include a first signal reflecting the force F1 on the handle and a second signal reflecting the opening and closing angle C1 of the vehicle door.

[0071] S2. Determine whether the door opening angle C1 is within a preset initial angle value C0. If so, the door is considered closed, and the current control module 5 is inactive, performing no control operations. Otherwise, the door is considered open, and the current control module 5 enters an active state. It analyzes the changes in F1 and C1 and makes the following decisions:

[0072] When F1 ≥ F0, the rotatable mode is activated and the input current of coil 3 is adjusted to 0; wherein F0 is the preset upper limit of the force;

[0073] When F1<F0 and C1 remains unchanged within a preset time threshold t, the hovering mode is activated and the input current of the coil 3 is adjusted to a preset first current threshold I1;

[0074] In the hovering mode, if the change value of C1 exceeds a preset upper limit of angle change and F1 remains unchanged, the input current of the coil 3 is adjusted to a preset second current threshold value I2; wherein 0<I1<I2.

[0075] The principle of the door stepless hovering method is the same as the above control strategy, which will not be described here.

[0076] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A car door stepless suspension system based on magnetorheological fluid, characterized in that: include: The housing (1) has an opening (11) at one end thereof which is connected to a cavity (12) inside the housing, and the cavity (12) is filled with magnetorheological fluid; A piston rod (2) has one end extending from an opening (11) into a cavity (12); one of the piston rod (2) and the housing (1) is fixedly mounted on a vehicle door, and the other is fixedly mounted on a vehicle body, and the piston rod (2) and the housing (1) can slide relative to each other as the vehicle door rotates, and a sealing member for preventing magnetorheological fluid from leaking is also provided at the opening (11); a coil (3) wound around the outside of the housing (1) and used to provide a magnetic field for the magnetorheological fluid in the cavity (12) when energized; A signal acquisition module (4) is used to acquire a response signal reflecting the state of the vehicle door in real time; the signal acquisition module (4) includes a pressure acquisition unit (41) and an angle acquisition unit (42); the pressure acquisition unit (41) is installed on the handle of the vehicle door and is used to acquire a first signal reflecting the force F1 applied to the handle; the angle acquisition unit (42) is used to acquire a second signal reflecting the opening and closing angle C1 of the vehicle door; A current control module (5) is used to adjust the input current of the coil (3) according to the response signal and in accordance with a preset control strategy, thereby adjusting the damping force generated by the magnetorheological fluid in the cavity (12) on the piston rod (2) to achieve rotatable or stepless suspension of the vehicle door.

2. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 1, characterized in that: The control strategy is as follows: It is determined whether the door opening and closing angle C1 is at a preset initial angle value C0. If so, it is determined that the door is closed, and the current control module (5) is in a non-working state and does not perform any control operation. If not, it is determined that the door is open, and the current control module (5) enters a working state and analyzes the changes of F1 and C1 to make the following decisions: When F1≥F0, the rotatable mode is activated and the input current of the coil (3) is adjusted to 0; wherein F0 is a preset upper limit of the force; When F1<F0 and C1 remains unchanged within a preset time threshold t, the hovering mode is activated, and the input current of the coil (3) is adjusted to a preset first current threshold I1; In the hovering mode, if the change value of C1 exceeds a preset upper limit of angle change and F1 remains unchanged, the input current of the coil (3) is adjusted to a preset second current threshold value I2; wherein 0<I1<I2.

3. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 1, characterized in that: Also includes: The connecting member (6) has a tubular structure and one end is inserted into the opening (11); the cross-section of the outer wall of the connecting member (6) and the cross-section projection of the inner wall of the outer shell (1) match each other, and the two are relatively fixed; a first sealing ring (71) is provided between the connecting member (6) and the outer shell (1) to achieve one-way sealing; the cross-section of the inner wall of the connecting member (6) and the cross-section projection of the piston rod (2) match each other, and the two are in sliding contact; three fixed second sealing rings (72) are provided on the inner wall of the connecting member (6) at intervals along the sliding direction to achieve two-way sealing.

4. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 3, characterized in that: The housing (1), the connecting piece (6) and the piston rod (2) are all arc-shaped along the extension direction and have circular cross sections.

5. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 4, characterized in that: The section of the piston rod (2) that extends into the cavity (12) is an extending section, and a gap for allowing magnetorheological fluid to flow exists between the circumferential outer edge of the extending section and the circumferential inner wall of the housing (1).

6. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 5, characterized in that: The end of the extension section is integrally connected with a first disc (21); the circumferential outer edge projection area of ​​the first disc (21) is larger than the circumferential outer edge projection area of ​​the extension section; at least one first disc (21) is provided, and when there are multiple first discs (21), they are sequentially spaced and distributed along the extension direction of the extension section; the first disc (21) is provided with at least one guide hole (210) parallel to the extension direction of the extension section along the circumferential direction.

7. The stepless suspension system for vehicle doors based on magnetorheological fluid according to claim 3, characterized in that: A second disc (62) is integrally connected to the middle portion of the outer wall of the connecting member (6), and the end surface of the second disc (62) and the end surface of the outer shell (1) are fixedly connected by a plurality of screws (8).

8. A vehicle comprising a vehicle body and a vehicle door, characterized in that: It also includes a vehicle door stepless suspension system based on magnetorheological fluid as described in any one of claims 1 to 7.

9. A method for stepless suspension of a vehicle door based on magnetorheological fluid, characterized in that: The method applied to a vehicle door stepless suspension system based on magnetorheological fluid as claimed in any one of claims 1 to 7 comprises the following steps: S1 real-time acquisition of a response signal reflecting the state of the door, the response signal includes a first signal reflecting the handle force F1 and a second signal reflecting the door opening and closing angle C1; S2. Determine whether the door opening and closing angle C1 is at a preset initial angle value C0. If so, the door is determined to be closed, and the current control module (5) is in a non-operating state and does not perform any control operation. Otherwise, the door is determined to be open, and the current control module (5) enters an operating state and analyzes the changes in F1 and C1 to make the following decisions: When F1≥F0, the rotatable mode is activated and the input current of the coil (3) is adjusted to 0; wherein F0 is a preset upper limit of the force; When F1<F0 and C1 remains unchanged within a preset time threshold t, the hovering mode is activated, and the input current of the coil (3) is adjusted to a preset first current threshold I1; In the hovering mode, if the change value of C1 exceeds a preset upper limit of angle change and F1 remains unchanged, the input current of the coil (3) is adjusted to a preset second current threshold value I2; wherein 0<I1<I2.

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