Zero-backlash linear actuator and its installation method

Abstract

This invention provides a zero-gap holding linear actuator and its installation method, belonging to the field of spacecraft structures. The zero-gap holding linear actuator includes: an inner cylinder, an outer cylinder, a base, an elastic plate, and an electric telescopic rod assembly. The inner cylinder, outer cylinder, base, and elastic plate are all made of carbon fiber or Invar. The elastic plate is disposed within the base and fixed at one end to the bottom of the inner cylinder. The inner cylinder is nested within the outer cylinder, and an interference fit is achieved through the elastic plate. The electric telescopic rod assembly engages with a limiting hole at the bottom of the inner cylinder via a limiting screw, achieving anti-rotation and push-pull actuation. This actuator achieves ultra-low thermal deformation through low-expansion materials, and the electric telescopic rod does not require power for holding, solving the problems of large on-orbit thermal deformation and difficulty in achieving zero gap in existing spacecraft actuators. It has advantages such as high stability, compact structure, and strong adaptability to the space environment, and is suitable for on-orbit attitude adjustment of high-precision antennas or payloads in spacecraft.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft structures, specifically relating to a zero-backlash maintaining linear actuator and its installation method. More particularly, it relates to a zero-backlash maintaining ultra-low deformation linear actuator and its installation method. Background Technology

[0002] To ensure the successful execution of spacecraft missions, antennas or payloads must meet specific pointing and attitude requirements. Therefore, a six-degree-of-freedom active adjustment platform is employed to adjust the attitude of the antennas or payloads, achieving active adjustment and compensation of position and angle. Consequently, a linear actuator must be developed to overcome the harshness of the space environment, serving as the actuator to power the six-degree-of-freedom active adjustment platform and ensure its operational accuracy.

[0003] Currently, the relevant existing technologies include: A Chinese patent document with publication number CN114268241A discloses a non-contact bidirectional high-precision linear displacement actuator and its actuation method. The actuator includes multiple pairs of spring plates fixed to a base and permanent magnets fixed thereto. A driver is installed between the permanent magnets and the base boss. A conductive straight plate capable of bidirectional linear motion is mounted on a base support, and a locking device is installed below it. These structures together constitute the structure for achieving bidirectional linear displacement actuation of the conductive straight plate. The technical solution uses the driver to drive multiple permanent magnets to swing, thereby driving the conductive straight plate to achieve linear displacement output, and a locking unit is used to achieve locking and releasing. This technical solution uses various materials with high thermal expansion coefficients, resulting in a complex structural composition and significant thermal deformation under high and low temperature environments.

[0004] The existing Chinese patent document with publication number CN114679085A discloses a displacement sensor piezoelectric actuator based on the flexoelectric effect. It achieves high-precision displacement output through piezoelectric ceramics and a rhombic ring, and uses a strong flexoelectric effect sensing element to achieve high-precision displacement measurement. However, this technical solution has disadvantages such as not being able to self-lock, not being able to provide large displacement, and large thermal deformation under high and low temperature environments.

[0005] A Chinese patent document with publication number CN108599524A discloses a large-stroke, high-precision intelligent flexible actuator, comprising: a flexible hinge limiting cylinder, a flexible hinge, a support rod, a displacement sensor measuring surface, a displacement sensor, a limiting block, a top cover, a diaphragm spring assembly layer, a mover mounting cover, a voice coil motor, an outer cylinder, and a bottom cover. The voice coil motor includes a voice coil motor mover and a voice coil motor stator. After installation, vibration isolation, disturbance suppression, and precise pointing adjustment of the intelligent flexible actuator are achieved through measurement feedback from a large-stroke, high-precision eddy current displacement sensor and control output from a large-stroke, fast-response voice coil motor. This technical solution uses a voice coil motor for displacement output and an eddy current sensor for measurement feedback, but it suffers from drawbacks such as lack of self-locking and large thermal deformation under high and low temperature environments.

[0006] A Chinese patent document with publication number CN108847782A discloses a large-stroke piezoelectric linear actuator and its actuation method using micro-tooth drive. The actuator mainly consists of an actuation track with a micro-tooth structure, three sets of drive teeth that can mesh with the actuation track and have a phase difference after installation, a piezoelectric ceramic and its displacement amplification structure for controlling the up and down movement of the drive teeth, and an elastic pre-tightening device for constraining the meshing between the actuation track and the drive teeth. It achieves bidirectional linear output through the three sets of drive teeth with a phase difference. However, this technical solution has disadvantages such as low output accuracy, self-locking only at the clamping position, and large thermal deformation under high and low temperature environments.

[0007] Existing Chinese patent document CN106655879A discloses a high-precision, high-load composite piezoelectric active actuator and its active control method. The actuator includes a top cover, a force sensor, a connecting piece, a piezoelectric stack, a support rod, a circular sleeve, and a compression spring. The force sensor is connected to the top cover. Two sets of piezoelectric stacks are connected in parallel, with four piezoelectric stack actuators connected via a connecting piece, forming a two-stage piezoelectric drive unit in series. The lower-stage piezoelectric stack sits on a support base, which is connected to the support rod. The support base is connected to a pre-tightening device via a compression spring. The preload is adjusted by regulating the thread depth of the pre-tightening device. When the top cover is subjected to an external disturbance force axially, the force sensor detects the disturbance force signal and drives the two-stage piezoelectric drive unit via an external controller, generating a control force opposite to the axial disturbance force of the top cover, thus pushing the high-load object and achieving active vibration control. However, this technical solution suffers from drawbacks such as complex structure, small output displacement, lack of self-locking, and large thermal deformation under high and low temperature environments.

[0008] In summary, existing high-precision actuator technologies suffer from complex structural compositions and significant thermal deformation under high and low temperature environments. These limitations make them unsuitable for missions requiring complex on-orbit temperature environments, high thermal stability, and high actuation precision. They also fail to meet the demands of spacecraft for zero-gap, self-locking, and low-deformation actuators for on-orbit adjustment of high-precision antennas or payloads. To address these technical problems, this invention proposes a zero-gap holding ultra-low-deformation linear actuator that achieves high-precision position holding, high-precision actuation, and ultra-low thermal deformation. Compared to existing aerospace actuator technologies, it offers advantages such as compact structure, convenient installation, high reliability, and strong adaptability to the space environment, demonstrating better adaptability and scalability. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the purpose of this invention is to provide a zero-backlash holding linear actuator.

[0010] The zero-backlash holding linear actuator provided by the present invention is characterized in that it comprises: an inner cylinder, an outer cylinder, a base, an elastic sheet, and an electric telescopic rod assembly; The lower end of the inner cylinder is sleeved on the upper end of the outer cylinder, and multiple sets of elastic sheets are provided on the bottom end face of the inner cylinder. The inner cylinder is press-fitted to the inner wall of the outer cylinder by an elastic sheet; The lower part of the outer cylinder is connected to the base; The inner cylinder, outer cylinder, base, and elastic sheet are all made of a low heat deformation material, and the CTE parameter of the low heat deformation material is no greater than 1.5 × 10⁻⁶. -6 / ℃; The electric telescopic rod assembly is connected to the bottom of the inner cylinder for transmission.

[0011] Preferably, the electric telescopic rod assembly includes: a motor and a precision lead screw; The precision lead screw driven by the motor and the limiting screw fixed to the top of the precision lead screw; The limiting screw is clearance-fitted with the limiting hole located at the bottom of the inner cylinder.

[0012] Preferably, the low heat distortion material is carbon fiber or Invar.

[0013] Preferably, the elastic sheet is fixed to the bottom end face of the inner cylinder by adhesive or screwing.

[0014] Preferably, when the elastic sheet is installed on the bottom end face of the inner cylinder, the outline size of the elastic sheet is 0.2 mm to 0.5 mm larger than the outer outline size of the inner cylinder.

[0015] Preferably, the cross-sectional shape of the inner cylinder and the outer cylinder is rectangular or oblong.

[0016] Preferably, the shape of the limiting hole is adapted to the cross-sectional shape of the mating section of the limiting screw, and is rectangular or oblong, in order to prevent rotation.

[0017] Preferably, the electric telescopic rod assembly further includes: a housing, a lead screw nut, a bearing, and a pressure cap; The lead screw nut is fixed to the upper opening of the housing by a bearing; The motor is housed within the casing; The precision lead screw and the lead screw nut are threaded together. The pressure cap and fasteners press and fix the outer edge of the bearing.

[0018] The installation method of the zero-backlash holding linear actuator provided by the present invention includes: Step S1: Multiple sets of the elastic sheets are fixed to the bottom end face of the inner cylinder; Step S2: The inner cylinder is installed inside the outer cylinder, so that the elastic sheet is pressed against the inner wall of the outer cylinder; Step S3: Assemble the electric telescopic pole assembly; Step S4: The bottoms of the base and the electric telescopic rod assembly are respectively fixed to the target object; Step S5: The lower part of the outer cylinder is installed on the base, and the top of the precision lead screw is close to the bottom of the inner cylinder; Step S6: The limiting component is installed on the top of the precision lead screw, ensuring that the bottom of the inner cylinder is located between the limiting screw and the top of the precision lead screw, and that there is no forced installation stress.

[0019] A six-degree-of-freedom active adjustment platform uses a zero-backlash holding linear actuator provided according to the present invention to provide linear motion power.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses carbon fiber, Invar steel and other materials with low thermal expansion coefficients to make the main load-bearing and holding structures of the actuator. This greatly suppresses the structural deformation caused by changes in ambient temperature from the material source, ensuring the output accuracy and stability of the actuator in a wide temperature range. This solves the problems of existing actuator technology, such as the inability to reduce thermal deformation stress and its unsuitability for on-orbit flight environment. 2. In this invention, the electric telescopic rod only needs to provide pushing and pulling force during operation, without the need for power to maintain it. It has the beneficial effects of saving energy, reliable operation, and strong adaptability to spatial environment, and has better adaptability and expandability. 3. This invention achieves self-locking and zero-gap maintenance of the inner cylinder (output end) by means of an interference fit between the elastic plate at the bottom of the inner cylinder and the inner wall of the outer cylinder, relying on mechanical friction in the non-working state. It does not require continuous power supply from the motor and completely eliminates the positional uncertainty caused by the gap in traditional transmission. 4. Compared with existing actuator technologies, the overall structure of this invention is more compact and easier to install, while solving the problems of complexity and difficulty in installation and debugging of existing technologies. Attached Figure Description

[0021] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the zero-backlash holding linear actuator of the present invention; Figure 2 This is an overall sectional view of the zero-backlash holding linear actuator of the present invention; Figure 3 This is a cross-sectional view of the electric telescopic pole assembly structure of the present invention; Figure 4 This is an exploded view of the zero-backlash maintaining linear actuator of the present invention.

[0022] The diagram shows: Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0024] like Figures 1 to 3 As shown, this embodiment of the invention provides a zero-backlash holding linear actuator, including: an inner cylinder 1, an outer cylinder 2, a base 3, an elastic sheet 4, an electric telescopic rod assembly 5, a limit screw 6, a precision lead screw 7, a lead screw nut 8, a housing 9, a pressure cap 10, a bearing 11, and a motor 12. The lower end of the inner cylinder 1 is fitted onto the upper end of the outer cylinder 2. The upper side of the inner cylinder 1 serves as the output end and is connected to the load. The bottom surface of the inner cylinder 1 is provided with multiple sets of elastic plates 4. The inner cylinder 1 is press-fitted with the outer cylinder 2 through these elastic plates 4. A certain tension or force needs to be applied to achieve relative movement between the inner cylinder 1 and the outer cylinder 2 inside the outer cylinder 2. In the absence of force, the inner cylinder 1 is held in place by the elastic plates 4 against the inner wall of the outer cylinder 2, giving the inner cylinder 1 a certain holding force. The lower part of the outer cylinder is provided with a flange that is connected to the flange at the upper end of the base 3, which can be achieved by screw connection. Specifically, the upper side of the inner cylinder 1 is provided with a flange, which serves as the output end and is connected to the load. Furthermore, the inner cylinder 1 is precisely nested inside the outer cylinder 2, both of which are rectangular or waist-shaped columnar bodies; Furthermore, the inner cylinder 1, outer cylinder 2, base 3, and elastic sheet 4 are all made of carbon fiber or Invar steel. The elastic sheet 4 is fixed to the bottom of the inner cylinder 1 by adhesive or screw connection to ensure the overall low deformation characteristics of the actuator. Specifically, the elastic sheet 4 is made of high-strength carbon fiber material with good elasticity. Two to four sets of elastic sheets 4 are pasted to the bottom of the inner cylinder 1. The inner cylinder 1 and the outer cylinder 2 achieve an interference fit through the elastic sheet. A certain tensile and compressive force needs to be applied to achieve the relative movement between the inner cylinder 1 and the outer cylinder 2. Furthermore, the aforementioned electric telescopic rod assembly 5 includes: a limiting screw 6, a precision lead screw 7, a lead screw nut 8, a housing 9, a pressure cap 10, a bearing 11, and a motor 12; the lead screw nut 8 is fixed to the upper opening of the housing 9 via the bearing 11; the motor 12 is disposed inside the housing 12 and its bottom is fixed to the housing 12; the output shaft of the motor 12 is fixed to the threaded portion of the precision lead screw 7 via the lead screw nut 8 for transmission, that is, the precision lead screw 7 is driven to move up and down via the lead screw nut 8; the limiting screw 6 is disposed on the top of the precision lead screw 7; the pressure cap 10 is installed on the housing 9 by screws to press the outer ring of the bearing 11, thereby fixing the bearing 11.

[0025] Furthermore, the electric telescopic rod assembly 5 achieves clearance fit with the bottom limiting hole of the inner cylinder 1 through the limiting screw 6. Specifically, the limiting screw 6 and the bottom limiting hole of the inner cylinder 1 are fitted with a rectangular or oblong shaft hole to prevent rotation during movement. During operation, the electric telescopic rod assembly 5 needs to overcome a certain amount of free travel in order to push and pull the inner cylinder 1 up and down. In particular, the above-mentioned rectangular or oblong shaft hole design can prevent relative rotation between the inner cylinder 1 and the outer cylinder 2.

[0026] Furthermore, the lower flange provided on the lower side of the aforementioned base 3 serves as the installation base for connecting the motion base with the satellite structural plate, truss, and other general-purpose components.

[0027] Furthermore, embodiments of the present invention also provide an installation method for the zero-backlash maintaining ultra-low deformation linear actuator provided by the present invention, comprising: Step S1: Four sets of elastic sheets 4 are pasted on the bottom of the inner cylinder 1. After installation, the outline dimension of the elastic sheet 4 is 0.5 to 0.2 mm larger than the outer outline dimension of the inner cylinder 1. Step S2: The inner cylinder 1 is installed inside the outer cylinder 2, so that the elastic sheet 4 is reliably pressed against the inner wall of the outer cylinder 2, ensuring that the inner cylinder 1 can slide inside the outer cylinder 2 under stress. Step S3: The precision lead screw 7, lead screw nut 8, housing 9, pressure cap 1, bearing 11, and motor 12 are connected by fastening methods such as screws to form the electric push rod assembly 5; Step S4: The bottoms of the base 3 and the electric telescopic rod assembly 5 are respectively connected to the mounting base; Step S5: The inner cylinder 1 and outer cylinder 2 assembly is installed onto the upper flange of the base 3 through the lower flange of the outer cylinder 2, ensuring that the upper surface of the precision lead screw 7 is close to the lower surface of the inner cylinder 1; Step S6: The limit screw 5 is installed in conjunction with the lead screw nut 8 to ensure that the lower flange of the inner cylinder 1 is between the lower surface of the limit screw 6 and the upper surface of the precision lead screw 7, and there is no forced installation stress.

[0028] Furthermore, the deformation suppression principle of this invention lies in achieving high-precision fit, position retention, and low deformation characteristics through the structure of the inner cylinder 1, outer cylinder 2, and base 3 made of low-expansion material. The electric telescopic rod assembly 5 provides the actuator's extension and retraction power, without affecting the actuator's thermal deformation. In addition, the retaining function of this invention is independently achieved by a completely passive mechanical structure (low-expansion material inner cylinder 1 / outer cylinder 2 + elastic interference fit), utilizing the static friction force generated by elastic restoring force to achieve zero-clearance self-locking, requiring no energy. Because the material itself has minimal thermal deformation, the retaining accuracy is unaffected by temperature. The driving function of this invention is independently undertaken by a standard electric telescopic rod assembly 5, which is connected to the load, i.e., the inner cylinder 1, only through a clearance-fitted limiting component. It only operates briefly when a change in position is needed, providing sufficient push / pull force to overcome static friction, and does not participate in retaining. Therefore, its operating heat is not transferred to the main retaining structure and does not affect the final output accuracy. Through this decoupled design, combined with the application of low-expansion materials, the actuator simultaneously meets the three key requirements of "zero-clearance retention," "ultra-low thermal deformation," and "highly efficient and reliable drive."

[0029] In summary, this invention provides a zero-backlash maintaining ultra-low deformation linear actuator and its installation method, solving the problem of extremely large on-orbit thermal deformation and difficulty in achieving zero backlash in existing high-precision spacecraft actuators. It can provide high-precision zero-backlash displacement output and maintain ultra-low deformation characteristics in harsh temperature environments. Compared with existing spacecraft actuator technologies, it has the advantages of high stability, compact structure, and strong adaptability to space environment, and has better adaptability and scalability.

[0030] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0031] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A zero-backlash holding linear actuator, characterized in that, include: Inner cylinder (1), outer cylinder (2), base (3), elastic sheet (4) and electric telescopic rod assembly (5); The lower end of the inner cylinder (1) is sleeved on the upper end of the outer cylinder (2), and multiple sets of elastic sheets (4) are provided on the bottom end face of the inner cylinder (1). The inner cylinder (1) is interference-fitted with the inner wall of the outer cylinder (2) by an elastic sheet (4); The lower part of the outer cylinder (2) is connected to the base (3); The inner cylinder (1), outer cylinder (2), base (3), and elastic sheet (4) are all made of low heat deformation material, and the CTE parameter of the low heat deformation material is no greater than 1.5 × 10⁻⁶. -6 / ℃; The electric telescopic rod assembly (5) is connected to the bottom of the inner cylinder (1) for transmission.

2. The zero-backlash holding linear actuator according to claim 1, characterized in that, The electric telescopic rod assembly (5) includes: a motor (12) and a precision lead screw (7); The precision lead screw (7) driven by the motor (12) and the limiting screw (6) fixed to the top of the precision lead screw (7). The limiting screw (6) is clearance-fitted with the limiting hole located at the bottom of the inner cylinder (1).

3. The zero-backlash linear actuator according to claim 1, characterized in that, The low heat distortion material is carbon fiber or Invar steel.

4. The zero-backlash holding linear actuator according to claim 1, characterized in that, The elastic sheet (4) is fixed to the bottom end face of the inner cylinder (1) by adhesive or screwing.

5. The zero-backlash holding linear actuator according to claim 1, characterized in that, When the elastic sheet (4) is installed on the bottom end face of the inner cylinder (1), the outline size of the elastic sheet (4) is 0.2 mm to 0.5 mm larger than the outer outline size of the inner cylinder (1).

6. The zero-backlash holding linear actuator according to claim 1, characterized in that, The cross-sectional shape of the inner cylinder (1) and the outer cylinder (2) is rectangular or waist-shaped.

7. The zero-backlash holding linear actuator according to claim 2, characterized in that, The shape of the limiting hole is adapted to the cross-sectional shape of the mating section of the limiting screw (6), and is rectangular or waist-shaped, so as to prevent rotation.

8. The zero-backlash holding linear actuator according to claim 2, characterized in that, The electric telescopic pole assembly (5) also includes: a housing (9), a lead screw nut (8), a bearing (11), and a pressure cap (10). The lead screw nut (8) is fixed to the upper opening of the outer casing (9) by a bearing (11); The motor (12) is disposed inside the housing (9); The precision lead screw (7) is threadedly engaged with the lead screw nut (8); The pressure cap (10) and fasteners press and fix the outer edge of the bearing (11).

9. A method for installing a zero-backlash holding linear actuator according to any one of claims 1 to 6, characterized in that, include: Step S1: Multiple sets of the elastic sheets (4) are fixed to the bottom end face of the inner cylinder (1); Step S2: The inner cylinder (1) is installed inside the outer cylinder (2), so that the elastic sheet (4) is pressed against the inner wall of the outer cylinder (2); Step S3: Assemble the electric telescopic pole assembly (5); Step S4: The bottoms of the base (3) and the electric telescopic rod assembly (5) are respectively fixed to the target object; Step S5: The lower part of the outer cylinder (2) is installed on the base (3), and the top of the precision lead screw (7) is close to the bottom of the inner cylinder (1); Step S6: The limiting component (6) is installed on the top of the precision lead screw (7) and ensures that the bottom of the inner cylinder (1) is located between the limiting screw (6) and the top of the precision lead screw (7) without forced installation stress.

10. A six-degree-of-freedom active adjustment platform, characterized in that, The zero-backlash holding linear actuator according to any one of claims 1 to 8 provides linear motion power.

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