Dynamic regulation and control system and method for friction force of servo cylinder

Abstract

The invention discloses a dynamic regulation and control system and method for friction force of a servo cylinder. The dynamic regulation and control system is characterized in that a dynamic sealing pair of the servo cylinder is provided with a magneto-rheological elastomer dynamic seal; a magnetizing device is arranged on one side of the magneto-rheological elastomer dynamic seal, an axial positioning sensor is arranged on the servo cylinder, the magnetizing device is connected with a magnetic control unit, and the axial positioning sensor is connected with the magnetic control unit; the magnetic control unit judges whether the dynamic sealing pair area of the servo cylinder is in the starting stage or not through the axial positioning sensor and controls the magnetizing device to regulate and control the magnetic field intensity according to the judgment result. The problems of creeping and shaking of the servo hydraulic cylinder caused by the viscous effect of elastomer sealing in the starting process can be solved, and the displacement control precision of the servo cylinder is improved.

Description

Technical Field

[0001] The present invention specifically relates to a servo cylinder friction force dynamic control system and method. Background Art

[0002] The servo hydraulic cylinder is the actuator of the servo hydraulic system. It can convert the rotary motion of the servo motor into linear motion, and at the same time convert the servo motor's precise speed control, precise angle control and precise torque control into precise speed control, precise position control and precise thrust control. The main difference between the servo hydraulic cylinder and the standard hydraulic cylinder in design is that it adopts closed-loop servo control, which must meet the rapid response requirements during the operation of the servo system and ensure the servo system's precision control and dynamic performance requirements. However, there are the following prominent problems in the actual operation of the servo hydraulic cylinder: When the elastomeric dynamic seal and the metal contact pair in the servo hydraulic cylinder remain stationary for a long time, adhesion will occur, resulting in high static friction between the seal contact pairs. When the shear stress at the seal contact surface exceeds the static friction, the seal will break contact and jump forward, causing the hydraulic cylinder to creep and shake. When the frequency of the viscous motion is the same as the natural frequency of the system, resonance will occur, leading to severe oscillation.

[0003] In the prior art, the fundamental reason why the servo cylinder has creeping and jittering problems during the startup phase is due to the viscoelastic properties of the elastomeric sealing material. At the beginning of the startup phase, adhesion occurs between the seal and the metal contact pair, resulting in a high static friction force at the beginning of sliding, causing the elastomeric sealing material to deform violently. The elastic energy generated during the deformation process is stored inside the material. When the shear stress at the sealing contact surface exceeds the static friction force, the elastic energy stored in the sealing material will be rapidly released, and the seal will break contact and jump forward, causing the servo hydraulic cylinder to creep and jitter. Although the prior art can reduce the friction resistance of the servo cylinder during startup and operation to a certain extent by adopting a low-friction design solution, there are interval differences in the friction changes of the servo cylinder in different operating speed ranges. For example, the relationship between the friction and speed of the servo cylinder obtained through experimental testing and model fitting in the existing literature is as follows: Figure 1 shown.

[0004] from Figure 1 It can be seen that the friction force f0 of the servo cylinder under test is the largest when the speed is 0 mm / s; when the speed is 0~±50.0 mm / s, the friction force increases from f0 to f in the forward motion process. 50 , during the reverse run from f0 to f -50 The change is the most dramatic; in the speed range of ±50.0~±300 mm / s, the friction force changes from f 50 to f 300 , during the reverse operation, the friction force changes from f-50 to f -300 The variation range is small. The creep and jitter mainly occur in the range of 0 to 50.0 mm / s.

[0005] In order to solve the creep and jitter problems of the servo cylinder when it is running under starting conditions, it is necessary to perform corresponding regulation according to the friction force change law of the servo cylinder under starting conditions. Summary of the invention

[0006] The purpose of the present invention is to provide a servo cylinder friction dynamic control system and method, which can overcome the creeping and shaking problems of the servo hydraulic cylinder due to the viscosity of the elastomer seal during the startup process, and improve the displacement control accuracy of the servo cylinder.

[0007] The technical solution adopted by the present invention is: A servo cylinder friction dynamic control system, comprising: The dynamic seal pair of the servo cylinder is provided with a magnetorheological elastomer dynamic seal; A magnetizing device is provided on one side of the magnetorheological elastomer dynamic seal, an axial positioning sensor is provided on the servo cylinder, the magnetizing device is connected to a magnetic control unit, and the axial positioning sensor is connected to the magnetic control unit; The magnetic control unit determines whether the dynamic sealing area of ​​the servo cylinder is in the startup stage through the axial positioning sensor, and controls the magnetizing device to adjust the magnetic field strength based on the judgment result, and performs closed-loop dynamic regulation of the loss tangent of the seal according to the servo cylinder startup operating condition parameters.

[0008] Preferably, the dynamic sealing pair includes a sealing motion pair formed between the piston and the cylinder body and a sealing motion pair formed between the piston rod and the cylinder body.

[0009] Preferably, the base material of the magnetorheological elastomer dynamic seal is added with carbonyl iron powder particles (CIP).

[0010] Preferably, the friction force when sliding occurs between the dynamic seal pairs is: F = F adh + F hyst Formula (1) in, F adh is the adhesion friction, F hyst is the hysteresis friction.

[0011] Adhesion Friction F adh The calculation formula is: F adh = K 1 σ(E' / p)tanδ Formula (2) in, K 1 is a constant, s is the effective shear strength of the sliding interface, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent; Hysteresis friction F hyst The calculation formula is: F hyst = K 2 (p / E') n tanδ Formula (3) in, K 2 is a constant, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent.

[0012]

[0013] in, or is the viscosity constant of the elastomeric material, f is the strain frequency, E is the elastic modulus and γ is a constant.

[0014] When the magnetorheological elastomer dynamic seal is isotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 11.6~11.8 MPa in the absence of a magnetic field, and the elastic modulus is 12~12.2 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 13.9~14.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.8~16 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 20.4~20.6 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 10.5~10.7 MPa in the absence of a magnetic field, and the elastic modulus is 11.4~11.6 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 14.9-15.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.4-15.6 MPa in the presence of a magnetic field; When the magnetorheological elastomer dynamic seal is anisotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 6.6~6.7 MPa in the absence of a magnetic field, and the elastic modulus is 6.8~7.0 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 12.9~13.1 MPa in the absence of a magnetic field, and the elastic modulus is 13.5~13.7 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 17.1~17.3 MPa in the absence of a magnetic field, and the elastic modulus is 18.6~18.8 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 19.3~19.5 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 20.2~20.4 MPa in the absence of a magnetic field, and the elastic modulus is 23.0~23.2 MPa in the presence of a magnetic field.

[0015] A control method using the servo cylinder friction dynamic control system as described above, comprising: when the servo cylinder is in the starting, reversing or low-speed working stage, the magnetic field strength is controlled by a magnetizing device to change the elastic modulus of the magnetorheological elastomer dynamic seal, thereby changing the loss tangent, and then controlling the friction force, eliminating the sticking problem of the elastic seal in the starting stage, and fundamentally solving the creeping and shaking problems of the servo cylinder in the starting condition; When the servo cylinder moves normally, the magnetic field strength is reduced or there is no magnetic field through the magnetizing device, and the elastic modulus of the magnetorheological elastomer dynamic seal is reduced to restore the normal amount, thereby increasing the loss tangent to the normal amount.

[0016] When the servo cylinder is in the starting condition, the magnetic field strength is adjusted to reach the set value A1 through the magnetizing device; When the servo cylinder is in the reversing condition, the direction of the magnetic field is regulated by the magnetizing device; When the servo cylinder is in a low-speed condition, the magnetic field strength is adjusted to reach the set value A2 through the magnetizing device; A1>A2.

[0017] The beneficial effects of the present invention are: The present invention actively regulates the elastic modulus and loss tangent of the magnetorheological elastomer dynamic seal through a magnetic control unit, and utilizes the characteristics that the elastic modulus and loss tangent can be reversibly changed under the action of an external magnetic field to reduce the adhesion friction force in the sealing contact area during the startup of the servo cylinder, thereby overcoming the creeping and jitter problems of the servo hydraulic cylinder during the startup due to the viscosity of the elastomer seal, and improving the displacement control accuracy of the servo cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the relationship between the friction force and speed of a servo hydraulic cylinder in the prior art.

[0019] Figure 2 It is a schematic diagram of the principle of the servo cylinder friction force dynamic control system in an embodiment of the present invention.

[0020] In the figure: 1-piston; 2-cylinder body; 3-magnetizing device; 4-magnetic control unit; 5-axial positioning sensor; 6-magnetorheological elastomer seal; 7-central control unit. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] In the description of the present invention, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like are involved, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. It can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] Example 1 A servo cylinder friction dynamic control system, such as Figure 1~ 2, including: The dynamic seal pair of the servo cylinder is provided with a magnetorheological elastomer dynamic seal; A magnetizing device is provided on one side of the magnetorheological elastomer dynamic seal, an axial positioning sensor is provided on the servo cylinder, the magnetizing device is connected to a magnetic control unit, and the axial positioning sensor is connected to the magnetic control unit. The magnetic control unit determines whether the dynamic sealing sub-area of ​​the servo cylinder is in the startup stage through the axial positioning sensor, and controls the magnetizing device to adjust the magnetic field strength based on the judgment result, and performs closed-loop dynamic regulation of the loss tangent of the seal based on the servo cylinder startup operating condition parameters.

[0025] Furthermore, the dynamic sealing pair includes a sealing motion pair formed between the piston and the cylinder body and a sealing motion pair formed between the piston rod and the cylinder body.

[0026] Furthermore, the base material of the magnetorheological elastomer dynamic seal is added with carbonyl iron powder particles (CIP).

[0027] Furthermore, the friction force when sliding occurs between the dynamic seal pairs is: F = F adh + F hyst Formula (1) in, F adh is the adhesion friction, F hyst is the hysteresis friction.

[0028] Adhesion Friction F adh The calculation formula is: F adh = K 1 σ(E' / p)tanδ Formula (2) in, K 1 is a constant, s is the effective shear strength of the sliding interface, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent; Hysteresis friction F hyst The calculation formula is: F hyst = K 2 (p / E') n tanδ Formula (3) in, K 2 is a constant, E’is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent.

[0029]

[0030] in, or is the viscosity constant of the elastomeric material, f is the strain frequency, E is the elastic modulus and γ is a constant.

[0031] When the magnetorheological elastomer dynamic seal is isotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 11.6~11.8 MPa in the absence of a magnetic field, and the elastic modulus is 12~12.2 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 13.9~14.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.8~16 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 20.4~20.6 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 10.5~10.7 MPa in the absence of a magnetic field, and the elastic modulus is 11.4~11.6 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 14.9-15.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.4-15.6 MPa in the presence of a magnetic field; When the magnetorheological elastomer dynamic seal is anisotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 6.6~6.7 MPa in the absence of a magnetic field, and the elastic modulus is 6.8~7.0 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 12.9~13.1 MPa in the absence of a magnetic field, and the elastic modulus is 13.5~13.7 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 17.1~17.3 MPa in the absence of a magnetic field, and the elastic modulus is 18.6~18.8 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 19.3~19.5 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 20.2~20.4 MPa in the absence of a magnetic field, and the elastic modulus is 23.0~23.2 MPa in the presence of a magnetic field.

[0032] Example 2 A control method using the servo cylinder friction dynamic control system described in Example 1, comprising: when the servo cylinder is in the startup, reversing or low-speed working stage, increasing the magnetic field strength through a magnetizing device, increasing the elastic modulus of the magnetorheological elastomer dynamic seal, thereby reducing the loss tangent, thereby reducing the friction, eliminating the sticking problem of the elastic seal in the startup stage, and fundamentally solving the creeping and shaking problems of the servo cylinder under the startup condition; When the servo cylinder moves normally, the magnetic field strength is reduced or there is no magnetic field through the magnetizing device, and the elastic modulus of the magnetorheological elastomer dynamic seal is reduced to restore the normal amount, thereby increasing the loss tangent to the normal amount.

[0033] When the servo cylinder is in the starting condition, the corresponding speed range is 0~±5mm / s, and the servo cylinder adhesion friction ( F adh ) accounts for a large proportion, and the magnetic field strength is adjusted to reach the set value A1 through the magnetizing device; When the servo cylinder is in the reversing condition, the friction force changes in the positive and negative directions. The corresponding control variable is the change in the direction of the magnetic field. The direction of the magnetic field is controlled by the magnetizing device, and the magnetic field strength is also around the set value A1. When the servo cylinder is in low speed condition, the speed range corresponding to the low speed condition is 0~±50mm / s, and the friction force ( F hyst ) is relatively lagging, and the magnetic field strength is adjusted by the magnetizing device to reach the set value A2; A1>A2; In engineering practice, the starting friction force and low-speed friction force of the dynamic seal pair of the servo cylinder are obtained through testing.

[0034] Working principle of the present invention: (1) Magnetorheological elastomer dynamic seal Elastomer materials have the characteristics of high hardness, low compression permanent deformation rate, high rebound rate, and good comprehensive performance, so they are widely used in various forms of seals in the field of hydraulic sealing. However, elastomer seals have viscous characteristics. When the metal contact pair remains stationary for a long time, adhesion will occur between the sealing contact pairs. Therefore, at the beginning of sliding, there will be a high static friction between the elastomer seal and the metal contact pair, causing the elastomer seal to deform violently, and a large amount of elastic energy will be stored inside the material. When the shear stress at the sealing contact surface exceeds the static friction, the elastic energy stored in the sealing material will be quickly released, and the elastomer seal will break contact and jump forward, causing the servo hydraulic cylinder to crawl and shake.

[0035] To address this problem, the present invention proposes the use of magnetorheological elastomer (MRE), which is a new type of elastomer material prepared by adding carbonyl iron powder particles (CIP) to an elastomer matrix material (such as polyurethane, nitrile, etc.). Static compression and dynamic shear performance tests were performed on MRE material samples under conditions of no magnetic field and magnetic field, respectively. The results show that changes in the strength of the external magnetic field will change the elastic modulus of the MRE material under static compression and dynamic shear loads, as well as the loss tangent of the MRE material. By utilizing the controllable mechanical property changes of the MRE seal under the action of a magnetic field, a new solution can be provided to solve the creep and jitter problems of the servo cylinder caused by the viscous properties of the sealing material under startup conditions.

[0036] According to the above ideas, experimental research was carried out. Magnetorheological elastomer material samples were prepared with polyurethane and nitrile as the matrix, and the magnetomechanical properties of the samples were tested. The specific results are introduced as follows.

[0037] Experimental research example 1: With polyurethane as the matrix, carbonyl iron powder (CIP) was added to prepare a polyurethane-based magnetorheological elastomer dynamic sealing material sample. The elastic modulus test results of the sample under 25% compressive strain conditions are shown in Table 1.

[0038] Table 1 Elastic modulus test results of polyurethane-based magnetorheological elastomer dynamic sealing material samples

[0039] *Note: There is no pre-applied magnetic field during the preparation of isotropic samples, while there is a pre-applied magnetic field during the preparation of anisotropic samples in order to make the arrangement of carbonyl iron powder particles directional.

[0040] It can be seen from the test results in Table 1 that the elastic modulus of the polyurethane-based magnetorheological elastomer sealing material increases under the action of a magnetic field, and when the CIP content and the CIP particle diameter are different, the change in the elastic modulus is also different.

[0041] (2) Regulation of adhesion friction of elastomer sealing materials The adhesive friction between the sealing contact pairs mainly comes from the adhesion between the molecules of the elastomer sealing material and the molecules of the metal contact pairs. The friction force when sliding occurs between the sealing pairs can be expressed as: F = F adh + F hyst Formula (1) In the formula, F adh is the adhesion friction, Fhyst is the hysteresis friction.

[0042] Adhesion Friction F adh The calculation formula is: F adh = K 1 σ(E' / p)tanδ Formula (2) Where: K 1 is a constant, s is the effective shear strength of the sliding interface, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent.

[0043] Hysteresis friction F hyst The calculation formula is: F hyst = K 2 (p / E') n tanδ Formula (3) Where: K 2 is a constant; E’ is the storage modulus; p is the positive pressure of the microconvex body; tanδ is the loss tangent.

[0044] Combining the above two equations, it can be found that the friction between the sealing pair and the viscoelastic parameter loss tangent tan of the elastomer sealing material d Directly proportional.

[0045] The loss tangent, also known as loss factor, dissipation factor, damping factor or internal friction, is the tangent of the phase difference angle between the strain and stress cycles of a material under an alternating force field. It is also equal to the ratio of the loss modulus to the storage modulus of the material.

[0046] Loss tangent tan d The phase angle is defined as d The tangent of d It refers to the phase angle of the elastic sealing material strain peak lagging behind the stress peak, and its calculation formula is: Formula (4) In the formula, or is the viscosity constant of the elastomeric material, f is the strain frequency, E is the elastic modulus, and γ is the Euler-Mascheroni constant (0.577215665).

[0047] The above formula (4) shows that when the viscosity constant of the elastic material is or and strain frequency f When the loss tangent is constant, it depends on the elastic modulus of the elastic sealing material. E .Increase E Will reduce tan d, reduce E Will increase tan d Therefore, during the start-up process of the servo cylinder, the elastic modulus of the magnetorheological elastomer seal can be adjusted as needed to reduce the loss tangent of the magnetorheological elastomer seal, thereby reducing the adhesion friction and hysteresis friction between the sealing contact pairs, and eliminating the creep and jitter caused by adhesion friction between the sealing contact pairs.

[0048] Under the action of an external magnetic field, the control ranges of the above two experimental samples are shown in Table 2.

[0049] Table 2 Magnetotropic control range of polyurethane-based magnetorheological elastomer dynamic sealing material samples

[0050] It can be seen from the test results in Table 2 that the magnetically induced change rate of the polyurethane-based magnetorheological elastomer sealing material is related to the CIP content and the CIP particle diameter. Under the action of a 250mT magnetic field, the range of its elastic modulus is between 2.6147% and 13.944.

[0051] Firstly, the starting friction force of the servo cylinder is tested. Then, the polyurethane-based magnetorheological elastomer sealing material with corresponding composition is selected according to the changing law of the starting friction force of the servo cylinder. The elastic modulus variation range of the elastomer seal is changed by changing the strength of the external magnetic field. The loss tangent of the elastomer seal is adjusted accordingly. By reducing the adhesion friction and hysteresis friction of the elastomer seal, the creeping and jitter problems of the servo cylinder during the startup process are eliminated.

[0052] In summary, 1) the elastic modulus and loss tangent of the magnetorheological elastomer dynamic seal used in the servo cylinder can be reversibly changed under the action of an external magnetic field; 2) during the startup of the servo cylinder, the strength of the external magnetic field is changed by the magnetic control unit, and the elastic modulus and loss tangent of the magnetorheological elastomer dynamic seal are dynamically regulated to reduce the adhesion friction and hysteresis friction of the elastomer dynamic seal, which can fundamentally solve the creep and jitter problems of the servo cylinder under startup conditions and improve the displacement control accuracy of the servo cylinder.

[0053] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0054] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A servo cylinder friction dynamic control system, characterized in that: include The dynamic seal pair of the servo cylinder is provided with a magnetorheological elastomer dynamic seal; A magnetizing device is provided on one side of the magnetorheological elastomer dynamic seal, an axial positioning sensor is provided on the servo cylinder, the magnetizing device is connected to a magnetic control unit, and the axial positioning sensor is connected to the magnetic control unit; The magnetic control unit determines whether the dynamic sealing sub-area of ​​the servo cylinder is in the startup stage through the axial positioning sensor, and controls the magnetizing device to adjust the magnetic field strength according to the judgment result.

2. The servo cylinder friction force dynamic control system according to claim 1, characterized in that: The dynamic sealing pair includes a sealing motion pair formed between the piston and the cylinder body and a sealing motion pair formed between the piston rod and the cylinder body.

3. The servo cylinder friction force dynamic control system according to claim 2, characterized in that: The base material of the magnetorheological elastomer dynamic seal is carbonyl iron powder particles (CIP).

4. The servo cylinder friction force dynamic control system according to claim 3, characterized in that: The friction force when sliding occurs between dynamic seal pairs is: F = F adh + F hyst Formula (1) in, F adh is the adhesion friction, F hyst is the hysteresis friction.

5. The servo cylinder friction dynamic control system according to claim 4, characterized in that: Adhesion Friction F adh The calculation formula is: F adh = K 1 σ(E' / p)tanδ Formula (2) in, K 1 is a constant, σ is the effective shear strength of the sliding interface, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent; Hysteresis friction F hyst The calculation formula is: F hyst = K 2 (p / E') n tanδ Formula (3) in, K 2 is a constant, E’ is the storage modulus, p is the positive pressure of the microconvex body, tanδ is the loss tangent.

6. The servo cylinder friction force dynamic control system according to claim 4, characterized in that: in, η is the viscosity constant of the elastomeric material, f is the strain frequency, E is the elastic modulus and γ is a constant.

7. The servo cylinder friction force dynamic control system according to claim 1, characterized in that: When the magnetorheological elastomer dynamic seal is isotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 11.6~11.8 MPa in the absence of a magnetic field, and the elastic modulus is 12~12.2 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 13.9~14.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.8~16 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 20.4~20.6 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 10.5~10.7 MPa in the absence of a magnetic field, and the elastic modulus is 11.4~11.6 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 14.9-15.1 MPa in the absence of a magnetic field, and the elastic modulus is 15.4-15.6 MPa in the presence of a magnetic field; When the magnetorheological elastomer dynamic seal is anisotropic, If the CIP content is 10%, the CIP particle diameter is 5 μm, the elastic modulus is 6.6~6.7 MPa in the absence of a magnetic field, and the elastic modulus is 6.8~7.0 MPa in the presence of a magnetic field; If the CIP content is 20%, the CIP particle diameter is 5 μm, the elastic modulus is 12.9~13.1 MPa in the absence of a magnetic field, and the elastic modulus is 13.5~13.7 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 5 μm, the elastic modulus is 17.1~17.3 MPa in the absence of a magnetic field, and the elastic modulus is 18.6~18.8 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 10 μm, the elastic modulus is 19.3~19.5 MPa in the absence of a magnetic field, and the elastic modulus is 21.0~21.2 MPa in the presence of a magnetic field; If the CIP content is 30%, the CIP particle diameter is 20 μm, the elastic modulus is 20.2~20.4 MPa in the absence of a magnetic field, and the elastic modulus is 23.0~23.2 MPa in the presence of a magnetic field.

8. A control method using the servo cylinder friction dynamic control system as claimed in claim 1, characterized in that: include: When the servo cylinder is in the starting, reversing or low-speed working stage, the magnetic field strength is adjusted by the magnetizing device to change the elastic modulus of the magnetorheological elastomer dynamic seal, thereby changing the loss tangent and further adjusting the friction force; When the servo cylinder moves normally, the magnetic field strength is reduced or there is no magnetic field through the magnetizing device, and the elastic modulus of the magnetorheological elastomer dynamic seal is reduced to restore the normal amount, thereby increasing the loss tangent to the normal amount.

9. The control method according to claim 8, characterized in that: When the servo cylinder is in the starting condition, the speed range corresponding to the starting condition is 0~±5mm / s, and the magnetic field strength is adjusted by the magnetizing device to reach the set value A1; When the servo cylinder is in the reversing condition, the direction of the magnetic field is regulated by the magnetizing device; When the servo cylinder is in a low-speed condition, the magnetic field strength is adjusted to reach the set value A2 through the magnetizing device; A1>A2.

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