CN113898707A - Variable-rigidity compliant driver - Google Patents

Variable-rigidity compliant driver Download PDF

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Publication number
CN113898707A
CN113898707A CN202111286782.6A CN202111286782A CN113898707A CN 113898707 A CN113898707 A CN 113898707A CN 202111286782 A CN202111286782 A CN 202111286782A CN 113898707 A CN113898707 A CN 113898707A
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CN
China
Prior art keywords
spring
sleeve
baffle
interface board
variable stiffness
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Granted
Application number
CN202111286782.6A
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Chinese (zh)
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CN113898707B (en
Inventor
彭高亮
刘世伟
李思珏
程枫
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Harbin Institute of Technology
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Harbin Institute of Technology
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Priority to CN202111286782.6A priority Critical patent/CN113898707B/en
Publication of CN113898707A publication Critical patent/CN113898707A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/2021—Screw mechanisms with means for avoiding overloading
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/02—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems
    • F16F15/022—Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems using dampers and springs in combination
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F3/00—Spring units consisting of several springs, e.g. for obtaining a desired spring characteristic
    • F16F3/02—Spring units consisting of several springs, e.g. for obtaining a desired spring characteristic with springs made of steel or of other material having low internal friction
    • F16F3/04—Spring units consisting of several springs, e.g. for obtaining a desired spring characteristic with springs made of steel or of other material having low internal friction composed only of wound springs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
    • F16H25/2204—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with balls
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H25/24—Elements essential to such mechanisms, e.g. screws, nuts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H57/00—General details of gearing
    • F16H57/0006—Vibration-damping or noise reducing means specially adapted for gearings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/08—Means for collapsing antennas or parts thereof
    • H01Q1/10—Telescopic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2228/00—Functional characteristics, e.g. variability, frequency-dependence
    • F16F2228/06—Stiffness
    • F16F2228/066—Variable stiffness
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F2230/00—Purpose; Design features
    • F16F2230/0005—Attachment, e.g. to facilitate mounting onto confer adjustability
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
    • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
    • F16H25/20—Screw mechanisms
    • F16H2025/2062—Arrangements for driving the actuator
    • F16H2025/2081—Parallel arrangement of drive motor to screw axis

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Springs (AREA)

Abstract

The invention provides a variable-rigidity softener, which comprises a rack, and a driving mechanism, a linear actuating mechanism and a softener mechanism which are arranged on the rack, wherein the linear actuating mechanism is arranged on the rack; the rack comprises a supporting seat, the supporting seat comprises a sleeve, a first baffle arranged at one end of the sleeve and a second baffle sleeved at the other end of the sleeve, and the distance between the second baffle and the first baffle is adjustable; the linear actuating mechanism comprises a ball screw and a nut, the ball screw is used for converting the rotary motion of the driving mechanism into linear motion and connecting the linear motion with an external load, the nut is fixedly arranged on the rack, and part of the ball screw is arranged in the sleeve; the flexible mechanism comprises an interface board sleeved outside the sleeve, a first spring group sleeved outside the sleeve and respectively arranged at two free ends of two sides of the interface board, and a second spring group arranged at two free ends of the interface board. According to the scheme, multiple variable rigidities are achieved by changing the relation between the pre-tightening force of the spring and the spring gap, the operation is simple, and the implementation is easy.

Description

Variable-rigidity compliant driver
Technical Field
The invention belongs to the field of mechanical transmission devices, and particularly relates to a flexible driver with variable rigidity.
Background
The traditional driving device realizes the driving of an object through rigid design, namely, the transmission of motion and force is carried out in a mode of 'motor 401+ speed reducer + load', the mode has quick response and simple operation, is easy to realize, and is widely applied to general engineering practice. However, in the face of unknown environment, under the condition that the form and the size of the external load cannot be determined, the rigid design mode for realizing protection by means of control has great limitation, and the requirements of working conditions cannot be met.
On the basis, foreign scholars refer to a biological muscle model according to a bionic mechanism, and propose a design concept of a series elastic driver, namely, the flexible driving is realized by adopting a connection mode of 'motor 401+ reducer + spring + load', and the environment adaptability is better. The safety performance of the driving device can be effectively enhanced through the spring buffering effect when the driving device collides with the environment, the energy buffering effect is also stored, and meanwhile, due to the adoption of the linear spring, the spring force can be directly converted into the deformation of the spring for calculation, so that the accurate force control is convenient to realize. These advantages of compliance driving have led the following researchers to develop many studies in this respect, and have made great progress, but there are some limitations:
(1) the existing flexible drivers are designed in a pure spring or pure damping mode, and only some flexible drivers combining the springs and the damping are too large in size and difficult to arrange in spatial positions in actual engineering, so that the flexible drivers cannot be effectively popularized;
(2) most of the existing flexible drivers are designed into a form with fixed rigidity, and a part of variable rigidity forms have extremely high requirements on design and manufacture due to the complex structure of an elastic element, so that the processed products cannot meet the requirements;
(3) the existing flexible driver adopts an integrated design structure, and a flexible element is embedded into the whole driver, so that the modular design cannot be realized, and the requirement on interchangeability at the later stage cannot be met.
Disclosure of Invention
The invention aims to solve any defects of the prior art, and designs a bidirectional variable-rigidity compliant driver with a compact structure, which can realize the function of traditional rigid driving load, ensures good compliance adaptability by the variable rigidity characteristic, and can meet the interchangeability requirement by modular design.
Specifically, the invention provides a variable-rigidity compliant device, which comprises a rack, and a driving mechanism, a linear actuator and a compliant mechanism which are arranged on the rack;
the rack comprises a supporting seat, the supporting seat comprises a sleeve, a first baffle arranged at one end of the sleeve and a second baffle sleeved at the other end of the sleeve, and the distance between the second baffle and the first baffle is adjustable;
the linear actuating mechanism comprises a ball screw and a nut, the ball screw is used for converting the rotary motion of the driving mechanism into linear motion and connecting the linear motion with an external load, the nut is fixedly arranged on the rack, and part of the ball screw is arranged in the sleeve;
the compliant mechanism comprises an interface board sleeved outside the sleeve, a first spring group and a second spring group, wherein the first spring group and the second spring group are sleeved outside the sleeve and are respectively arranged at two free ends of two sides of the interface board; the free lengths of the second inner spring and the second outer spring are different.
In one embodiment, the first inner spring and the first outer spring are concentrically arranged and the second inner spring and the second outer spring are concentrically arranged.
In one embodiment, the two springs, which are concentrically arranged, have opposite handedness.
In one embodiment, the stiffness of the second outer spring is greater than the stiffness of the first outer spring and/or the stiffness of the second inner spring is greater than the stiffness of the first inner spring when the compliance device is subjected to a compressive force greater than a tensile force during operation.
In one embodiment, the driver further comprises a damping unit disposed inside the sleeve, and an end of the ball screw, which is remote from the load, is connected to the damping unit.
In one embodiment, the compliant mechanism further comprises a guide device and a pre-tightening device, the guide device comprises a guide rod, the guide rod penetrates through the interface board and the second baffle plate, one end of the guide rod is connected with the first baffle plate, and the pre-tightening device is used for fixing the second baffle plate at a preset position to achieve pre-tightening on the spring.
In one embodiment, the guide device further comprises a bearing seat disposed on the interface plate, the guide rod disposed through the bearing seat.
In one embodiment, the interface plate includes annular projections on both sides, the projections having an outer diameter compatible with the outer spring.
In one embodiment, the interface board further includes a connector member provided with an outer peripheral surface for connection with an external device.
In one embodiment, the frame further comprises a base, and the base is fixedly connected with the supporting seat or is of an integral structure.
By adopting the scheme, the free length of the first inner spring and the first outer spring and the free length of the second inner spring and the second outer spring are set, the distance between the second baffle plate and the first baffle plate is adjusted, the relation between the pre-tightening force of the spring and the spring gap is changed, and the variable rigidity is realized. According to the external load characteristics, the rigidity adjustment under the tension working condition and the compression working condition is realized.
Drawings
FIG. 1 is a general block diagram of a compliance of the present invention.
FIG. 2 is a cross-sectional view of a compliance of the present invention.
FIG. 3 is a block diagram of an interface board of the compliance of the present invention.
FIG. 4 is a schematic diagram of a compliant device according to the present invention in various operating conditions.
FIG. 5 is a schematic diagram of the variable stiffness of a compliance of the present invention.
FIG. 6 is a stiffness characteristic of a compliance of the present invention.
Detailed Description
In order to make the technical solution and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1-3, the variable stiffness compliant device of the present invention comprises a frame 100, and a driving mechanism 200, a linear actuator 300 and a compliant mechanism 400 disposed on the frame 100.
The rack 100 includes a support seat, the support seat includes a sleeve 111, a first baffle 112 disposed at one end of the sleeve 111, and a second baffle 113 sleeved at the other end of the sleeve 111, and a distance between the second baffle 113 and the first baffle 112 is adjustable.
Wherein the driving mechanism 200 is used for outputting a driving force.
The linear actuator 300 is used to convert the rotational motion of the driving mechanism 200 into a linear motion and is connected to an external load for providing motion and support to the load. The linear actuator 300 includes a ball screw 301 and a nut 302, the nut 302 is fixedly mounted on the frame 100, and the ball screw 301 is mounted inside the sleeve 111. In one aspect, one end of the ball screw 301 is provided with a joint 303 for connecting with an external load, and the joint 303 is connected with the ball screw 301 through a thread, for example.
The compliant mechanism 400 comprises an interface board 401 sleeved outside the sleeve 111, and a first spring group and a second spring group, wherein the first spring group and the second spring group are sleeved outside the sleeve 111 and are respectively arranged at two free ends of two sides of the interface board 401, the first spring group comprises a first inner spring 412 and a first outer spring 411 which are sleeved together, the second spring group comprises a second inner spring 422 and a second outer spring 421 which are sleeved together, and the free lengths of the first inner spring 412 and the first outer spring 411 are different; the free lengths of the second inner spring 422 and the second outer spring 421 are different.
By adopting the scheme, the free lengths of the first inner spring 412 and the first outer spring 411 and the free lengths of the second inner spring 422 and the second outer spring 421 are set, the distance between the second baffle 113 and the first baffle 112 is adjusted, the relationship between the pre-tightening force of the springs and the spring gap is changed, and the variable stiffness is realized. According to the external load characteristics, the rigidity adjustment under the tension working condition and the compression working condition is realized.
In one embodiment, the first inner spring 412 and the first outer spring 411 are concentrically disposed, and the second inner spring 422 and the second outer spring 421 are concentrically disposed.
In one embodiment, the two springs, which are concentrically arranged, have opposite handedness. For example, the first inner spring 412 is a left-handed spring and the first outer spring 411 is a right-handed spring, or vice versa. The second spring set may be the same or opposite to the first spring set. The reverse arrangement can ensure that the inner spring and the outer spring are concentric and cannot be skewed.
In one embodiment, the free length of the outer spring 411/421 is greater than the free length of the inner spring 412/422.
In one embodiment, the spring free length and stiffness are set according to the stiffness change of the driver during operation, for example, when the compliance device is subjected to a pressure force greater than a tension force during operation, the stiffness of the springs on the right side of the interface board 401 is greater than the stiffness of the springs on the left side (the stiffness of the second outer spring 421 is greater than the stiffness of the first outer spring 411 and/or the stiffness of the second inner spring 422 is greater than the stiffness of the first inner spring 412). For example, when the working environment of the softener is subjected to a tensile force and a compressive force with asymmetric stiffness in a certain section, the free length difference of the first spring group is different from that of the second spring group.
In one embodiment, the free lengths of the first inner spring 412 and the second inner spring 422 are the same, the free lengths of the first outer spring 411 and the second outer spring 421 are the same, the stiffness of the first outer spring 411 and the stiffness of the second outer spring 421 are the same, and the stiffness of the first inner spring 412 and the stiffness of the second inner spring 422 are the same. By adopting the scheme of symmetrical arrangement, the rigidity characteristic curves when the driver bears the tensile force and the pressure are the same, the method is suitable for occasions when the driver bears the tensile force and the pressure, and can realize accurate control.
In one embodiment, the compliance mechanism 400 further comprises a guide device and a pre-tightening device, the guide device comprises a guide rod 431, the guide rod 431 passes through the interface board 401 and the second baffle 113, one end of the guide rod is connected with the first baffle 112, and the pre-tightening device is used for fixing the second baffle 113 at a preset position to achieve pre-tightening on the spring. The pre-tightening device is, for example, a pre-tightening nut 432, a thread is provided on the ball screw 301, and by adjusting the position of the pre-tightening nut 432 on the thread, the pre-tightening nut 432 pushes the second baffle 113 to move along the sleeve 111, thereby controlling the pre-tightening of the first outer spring 411 and the second outer spring 421. The pre-tightening force can be directly determined by calculation according to the thread pitch and the number of tightening turns of the pre-tightening nut 432.
In one embodiment, the guide further comprises a bearing block 402, the bearing block 402 is disposed on the interface plate 401, and the guide rod 431 is disposed through the bearing block 402. The bearing mount 402 is preferably disposed on the interface plate 401 in an interference fit.
In one embodiment, the guide further includes a fixing device 433, such as a fixing nut, for preventing the guide rod 431 from falling off the second shutter 113. Specifically, the fixing device 433 is sleeved on the guide rod 431 and is installed on a side of the second blocking plate 113 away from the pretension nut 432. The first blocking plate 112 limits the movement of the guide rod 431 to the left in the figure, and the fixing device 433 limits the movement of the guide rod 431 to the right in the figure. During assembly, the first baffle plate 112, the first spring set, the interface board 401, the second spring set, the guide rod 431 and the fixing nut 433 are installed (the nut is unscrewed leftwards in advance), then the second baffle plate 113 is installed, and then the second baffle plate is pre-tightened through the pre-tightening nut 432. After the pre-tightening is completed, the fixing nut 433 is screwed to the right end, and the guide rod is blocked by the nut and the second baffle 113, so that the guide rod is fixed. By adopting the scheme, the guide rod can be fixed, the installation and the disassembly are more convenient, the guide rod and the baffle are not required to be integrally arranged, and the processing cost is reduced.
In one embodiment, the guiding rods 431 are a plurality of guiding rods 431, preferably distributed in a regular polygon, for example, four guiding rods 431 are distributed in a square shape on the periphery of the protruding structure 403.
By adopting the scheme, the spring can be pre-tensioned conveniently, and an accurate guiding function can be provided for the movement of the interface board 401.
In one embodiment, the driver further comprises a damping unit 500, the damping unit 500 is disposed inside the sleeve 111, and an end of the ball screw 301, which is far from the load, is connected to the damping unit 500. In one embodiment, the ball screw 301 is connected to the damping unit 500 by a screw thread. Preferably, an end of the damping unit 500, which is away from the ball screw 301, extends out of the sleeve 111, and is provided with a thread for engaging with the pre-tightening nut 432.
By adopting the scheme, the driver can provide elastic force and damping force, and the damping unit 500 is added in the scheme, so that the conversion of energy is facilitated, and the designed driving device can obtain better environmental adaptability; through adding damping unit 500 to the sleeve 111 of back supporting seat, can accomplish damping unit 500's arrangement under the condition that does not occupy extra space like this, can also provide the support of one end for ball 301 is vice simultaneously, greatly reduced the volume of integrated device for compact structure easily spatial arrangement.
In one embodiment, the interface plate 401 includes annular protruding structures 403 disposed on both sides, and the outer diameter of the protruding structures 403 is adapted to the outer spring 411/421. In one embodiment, the inner side of the protruding structure 403 includes a groove with sides that conform to the outer diameter of the inner spring 412/422.
With this arrangement, the annular protrusion 403 can position the inner spring 412/422 and the outer spring 411/412 when the springs are compressed, thereby increasing the stability of the springs.
In one embodiment, the interface board 401 further includes a connector 404 having an outer peripheral surface for connecting to an external device. In one aspect, the connector 404 is a stub shaft.
In one embodiment, the drive means comprises a motor 401 and a reduction mechanism 402, the reduction mechanism 402 preferably being a gear set.
In one embodiment, the frame 100 further comprises a base 114, and the base 114 is fixedly connected to the supporting base or is an integral structure. Specifically, the base 114 is fixedly connected to the first baffle 112 or is an integral mechanism.
In one embodiment, the drive means and the nut 302 cooperating with the ball screw 301 are provided on the base 114. Specifically, the base 114 is a box body having openings at both sides, and the motor 401 is fixed to the box body. The nut 302 is sleeved with a first shaft sleeve 121 on the outer circumference, and the first shaft sleeve 121 is fixed on the inner wall of the base 114 through a bearing 122. The gear shaft of the speed reducing mechanism 402 is fixed to the second bushing 123, and the second bushing 123 is fixed to the nut 302 and the first bushing 122 by bolts. The first shutter 112 closes one opening of the case, and the gear train blocks the other opening of the case.
The working principle of the compliant driver of the present application is described below with reference to fig. 4-5 and a specific scheme, wherein two springs with different free lengths are arranged in parallel to form a spring set, and the change of stiffness is realized by the difference between the lengths of the two springs; two spring groups are arranged in parallel to realize elastic driving during pressure-tension conversion, and the combined spring can be designed into various rigidity combinations according to different pre-tightening pressures and spring length differences. Specifically, in the present embodiment, the free length of the first outer spring 411 is greater than the free length of the first inner spring 412, the free length of the second outer spring 421 is greater than the free length of the second inner spring 422, the stiffness of the first outer spring 411 is the same as the stiffness of the second outer spring 421 and is k1, and the stiffness of the first inner spring 412 is the same as the stiffness of the second inner spring 422 and is k 2. As follows
(1) In the initial state, namely, no pre-tightening load is applied, and all the springs keep the original length state;
(2) and in a pre-tightening state, the spring is pre-tightened and loaded. The second outer spring 421 is driven to move by the movement of the second baffle 113, so as to push the interface board 401 to move, so that the first outer spring 411 and the second outer spring 421 reach a pre-tightening state, the first inner spring 412 and the second inner spring 422 are still in a free state, at this time, the length difference between the first outer spring 411 and the first inner spring 412 is Ld, and the length difference between the second outer spring 421 and the second inner spring 422 is Ld (hereinafter referred to as a gap Ld). At this time, the inner spring does not act, and the stiffness of the combined spring is the parallel stiffness of the first outer spring 411 and the second outer spring 421, i.e., 2k 1;
(3) as the force applied to the driver increases, there are 3 cases to discuss:
the first method comprises the following steps: when the gap Ld is small, the first baffle 112 or the second baffle 113 moves toward the interface board 401 under the action of external force, but the first outer spring 411 and the second outer spring 421 are still in a pre-tensioned state, at this time, the interface board 401 contacts one of the first inner spring 412 and the second inner spring 422 and is compressed, and at this time, the overall stiffness of the combined spring is 2k1+ k 2;
and the second method comprises the following steps: when the gap Ld is large, the first baffle 112 or the second baffle 113 moves toward the interface board 401 under the action of an external force, so that one of the first outer spring 411 and the second outer spring 421 is compressed, and the other one is separated from the pre-tightening state, at this time, the interface board 401 does not contact the first inner spring 412 or the second inner spring 422, namely, the two inner springs still do not contact the interface board 401 and keep a free state, and one outer spring is also separated from the pre-tightening state, only one outer spring is accepted, and at this time, the overall stiffness of the combined spring is k 1;
and the third is that: when the gap Ld is moderate, the first baffle 112 or the second baffle 113 moves towards the interface board 401 under the action of external force, but the first outer spring 411 and the second outer spring 421 are still in a pre-tightening state, and when the external force balances the pre-tightening force, the first baffle 112 or the second baffle 113 just moves for a distance of the gap Ld relative to the interface board 401, at this time, although the inner spring contacts the interface board 401, the inner spring does not have the powerful action, and the overall stiffness of the combined spring is 2k 1;
(4) when the external force is continuously applied to the driver, the first baffle 112 or the second baffle 113 moves towards the interface board 401 under the action of the external force, the interface board 401 is in contact with the first inner spring 412 or the second inner spring 422 and is compressed, at this time, only the first outer spring 411 and the first inner spring 412 play a role, or only the second outer spring 421 and the second inner spring 422 play a role, at this time, the overall stiffness of the combined spring in a bearable range is k1+ k 2;
according to practical engineering experience, the ball screw 301 pair is often subjected to pressure when being extended and tensile force when being retracted. When the external load is pressure, since the interface board 401 is fixed as an external support position, the left combination spring (the first spring group) is compressed as shown in fig. C; similarly, when the external load is a pulling force, the interface board 401 is fixed, and the right combined spring (the second spring set) is compressed, as shown in fig. D.
In this embodiment, the first spring set and the second spring set are in a symmetrical state, so that the tension condition and the compression condition of the driver are symmetrical, and the stiffness characteristic curve of the bidirectional variable-stiffness elastic driver can be obtained as shown in fig. 5.
Where Ld1 denotes the first of the three cases, Ld2 denotes the second of the three cases, and Ld3 denotes the third of the three cases. The horizontal axis x represents the movement distance of the first shutter 112 or the second shutter 113 with respect to the interface board 401; f0 is the balance point between the external force and the pretension force.
Example 1:
the following describes a specific application scheme of the compliant driver of the present invention, which is applied to a large radar antenna that is usually expanded by using a multi-stage framework to drive an antenna reflection net between the frameworks to move synchronously, so as to fold and furl an antenna array surface. Due to the fact that the number of the frameworks is large, the problem of asynchronous movement is easily caused in the linkage unfolding process, so that movement clamping stagnation, stress surge, error accumulation and other abnormalities are caused, and synchronous and stable erection of the array surface is difficult to achieve.
The invention takes the designed flexible driver with bidirectional variable rigidity as a driving element for linkage unfolding of the antenna framework, and the bidirectional variable rigidity can be respectively suitable for two different working conditions of unfolding and folding of the antenna.
The variable rigidity compliant device comprises a rack 100, and a motor 401, a speed reducer, a nut screw mechanism 300 and a compliant mechanism 400 which are arranged on the rack 100. The rack 100 includes a support seat, the support seat includes a sleeve 111, a first baffle 112 disposed at one end of the sleeve 111, and a second baffle 113 sleeved at the other end of the sleeve 111, and a distance between the second baffle 113 and the first baffle 112 is adjustable. The nut is fixed on the frame 100, and the ball screw 301 is installed inside the sleeve 111.
The compliant mechanism 400 includes an interface board 401 sleeved outside the sleeve 111, and a first spring set and a second spring set sleeved outside the sleeve 111 and separately disposed at two free ends of two sides of the interface board 401, wherein the first spring set includes a first inner spring 412 and a first outer spring 411 that are sleeved together, and the second spring set includes a second inner spring 422 and a second outer spring 421 that are sleeved together. The driver further comprises a damping unit 500, the damping unit 500 is arranged inside the sleeve 111, and one end, far away from the load, of the ball screw 301 is connected with the damping unit 500 through a threaded structure. One end of the damping unit 500, which is far away from the ball screw 301, extends out of the sleeve 111, and is provided with a thread for matching with the pre-tightening nut 432.
The first inner spring 412 and the second inner spring 422 have the same parameters, and the wire diameter is 8mm, the free height is 180mm, and the pitch diameter is 58 mm. The first outer spring 411 and the second outer spring 421 have the same parameters, and the wire diameter is 8mm, the free height is 200mm, and the pitch diameter is 75 mm. In order to prevent the spring wire from being locked due to the skew of the inner and outer combined springs, the first inner spring 412 and the second inner spring 422 are designed as left-handed cylindrical coil springs, and the first outer spring 411 and the second outer spring 421 are designed as right-handed cylindrical coil springs. Because each skeleton equidistance of antenna distributes, and other external disturbance effect influences are less in linkage development in-process, considers the scope and the enlarged effect of cascaded skeleton synchronous error clearance simultaneously, and the design inner and outer spring clearance Ld equals 10 mm.
During operation, the pre-tightening of the compliant driver is achieved by first tightening the pre-tightening nut 432 at the end of the bi-directional variable stiffness compliant driver. And adjusting the pre-tightening distance to be 20mm, namely the lengths of the two pre-tightened outer springs are both 190mm, and the distance between the inner spring and the outer spring is equal to the designed spring clearance Ld.
In the linkage unfolding process of the antenna frameworks, the external joint 303 of the flexible driver is hinged to a first framework of the antenna, and the peripheral short shaft of the interface board 401 is hinged to a second framework of the antenna.
The motor 401 is started to operate to drive the speed reducer to decelerate and increase force, so that linear driving of the ball screw 301 pair is realized, the first skeleton and the second skeleton of the antenna are unfolded, and the integral skeleton and the array surface are unfolded and erected through the linkage unfolding mechanism of the antenna. Since the compliant actuator itself is already in a pre-tensioned state, the external joint 303 is always in a stressed state during the deployment of the antenna backbone. If the driving force generated by the asynchronous movement of the skeletons is increased, the pre-tensioned first outer spring 411 and second outer spring 421(2k1) can play a certain energy release buffering role; if the asynchronous influence of the frameworks is serious, the single first outer spring 421 and the single second outer spring 421 cannot overcome large resistance, and the combined spring will play a role at the moment, because the gap Ld is just equal to half of the pre-tightening distance, namely, the outer spring on one side is compressed by 10mm again, and the just pre-tightening of the outer spring on the other side is lost, which is equivalent to losing the function. At the moment, the outer spring on one side is changed into 180mm and can be just connected with the inner spring in parallel, the rigidity of the combined spring is K1+ K2 which is the sum of the rigidity of the single inner spring and the rigidity of the single outer spring, and the rigidity is increased compared with that of the pre-tightened outer spring, so that larger energy can be provided to relieve motion impact caused by unstable motion, and the stable unfolding operation of the whole mechanism is further ensured.
In the linkage folding process of the antenna framework, the motion process of the antenna framework is just the inverse process of the unfolding motion. The external street of the driver is hinged to the first framework of the antenna, and the short shafts on the two sides of the driver interface board 401 are hinged to the second framework of the antenna. The motor 401 is started to run reversely to drive the speed reducer to reduce speed and increase force, so that linear driving of the ball screw 301 pair is realized, the first skeleton and the second skeleton of the antenna are folded, and the folding motion of the whole skeleton and the array surface is realized through the linkage unfolding mechanism of the antenna. Since the compliant actuator is already in a pre-tightening operating state, the external joint 303 is always in a tension state during the process of folding the antenna framework. If the driving force generated by the asynchronous movement of the skeletons is increased, the pre-tensioned first outer spring 411 and second outer spring 421(2k1) can play a certain energy release buffering role; if the skeleton is not synchronous and the influence is serious, the single outer spring can not overcome large resistance, the combined spring plays a role at the moment, and the gap Ld is just equal to half of the pre-tightening distance, so the rigidity of the combined spring is k1+ k2 at the moment, and the rigidity is increased compared with the pre-tightening outer spring, so that larger energy can be provided to relieve the motion impact caused by unstable motion, and the stable furling action of the whole mechanism is further ensured.
The above scheme is only a distance, and when the external force is changed more complexly and is not a single force source, the scheme can be designed to be the case of adding 2k1+ k2 or k 1. Among them, when the external force is large, the case of 2k1+ k2 should be designed to achieve a large energy buffer by a small displacement. When the external resistance is relatively small, the design can be in the form of k1, and the small rigidity can also satisfy the energy buffering effect.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.

Claims (10)

1. A variable stiffness compliant device, comprising: the device comprises a rack, and a driving mechanism, a linear actuating mechanism and a compliant mechanism which are arranged on the rack;
the rack comprises a supporting seat, the supporting seat comprises a sleeve, a first baffle arranged at one end of the sleeve and a second baffle sleeved at the other end of the sleeve, and the distance between the second baffle and the first baffle is adjustable;
the linear actuating mechanism comprises a ball screw and a nut, the ball screw is used for converting the rotary motion of the driving mechanism into linear motion and connecting the linear motion with an external load, the nut is fixedly arranged on the rack, and part of the ball screw is arranged in the sleeve;
the compliant mechanism comprises an interface board sleeved outside the sleeve, a first spring group and a second spring group, wherein the first spring group and the second spring group are sleeved outside the sleeve and are respectively arranged at two free ends of two sides of the interface board; the free lengths of the second inner spring and the second outer spring are different.
2. The variable stiffness compliant device of claim 1, wherein: the first inner spring and the first outer spring are concentrically arranged, and the second inner spring and the second outer spring are concentrically arranged.
3. The variable stiffness compliant device of claim 2, wherein: the two springs arranged concentrically have opposite handedness.
4. The variable stiffness compliant device of claim 2, wherein: when the pressure borne by the compliance device is larger than the pulling force in work, the rigidity of the second outer spring is larger than that of the first outer spring and/or the rigidity of the second inner spring is larger than that of the first inner spring.
5. The variable stiffness compliant device of claim 1, wherein: the driver further comprises a damping unit, the damping unit is arranged inside the sleeve, and one end, far away from the load, of the ball screw is connected with the damping unit.
6. The variable stiffness compliant device of any one of claims 1-5, wherein: the compliant mechanism further comprises a guide device and a pre-tightening device, the guide device comprises a guide rod, the guide rod penetrates through the interface board and the second baffle plate, one end of the guide rod is connected with the first baffle plate, and the pre-tightening device is used for fixing the second baffle plate at a preset position to pre-tighten the spring.
7. The variable stiffness compliant device of claim 6, wherein: the guiding device further comprises a bearing seat, the bearing seat is arranged on the interface board, and the guiding rod penetrates through the bearing seat.
8. The variable stiffness compliant device of any one of claims 1-5, wherein: the interface board comprises annular protruding structures arranged on two surfaces, and the outer diameters of the protruding structures are matched with the outer springs.
9. The variable stiffness compliant device of any one of claims 1-5, wherein: the interface board further comprises a connecting piece provided with an outer peripheral surface and used for being connected with an external device.
10. The variable stiffness compliant device of any one of claims 1-5, wherein: the frame still includes the base, the base with supporting seat fixed connection or structure as an organic whole.
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