Linear variable stiffness driver

Abstract

The invention discloses a linear variable-stiffness driver, relates to the technical field of robot joint drivers, and solves the problem that an existing variable-stiffness driver cannot realize large-range and high-precision continuous stiffness adjusting.The linear variable-stiffness driver comprises a structural supporting body, and a fixed connecting piece and a movable connecting piece are arranged at the two ends of the structural supporting body correspondingly; an input assembly is arranged at the end, close to the fixed connecting piece, in the structure supporting body, a cam structure and an output assembly which can slide in the axial direction are sequentially arranged on the structure supporting body, the cam structure is in transmission fit with the input assembly, the input assembly can drive the cam structure to move in the axial direction, and the output assembly is connected with the output shaft. The movable connecting piece is arranged at the end part of the output shaft; the output assembly is provided with a plate spring assembly and a rigidity adjusting assembly, the rigidity adjusting assembly is matched with the plate spring assembly, the rigidity adjusting assembly can change the matching position of the rigidity adjusting assembly and the plate spring assembly, the effective stress supporting length of the plate spring assembly is changed, and therefore the rigidity of the plate spring assembly is changed. And the plate spring assembly is matched with the cam structure. The rigidity of the driver can be adjusted along with the change of an external load, and large-range and high-precision continuous rigidity adjustment is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of robotic joint drives, and particularly to a linear variable stiffness drive. Background Art

[0002] Robotic joints have been widely used in many fields, such as rehabilitation therapy, exoskeletons, and human-robot collaboration. The safety of physical human-robot interaction is a basic requirement for robots that coexist and cooperate with humans. Compared with rigid robotic joints, flexible joints can be used to provide safer physical human-robot interaction.

[0003] Currently, there are mainly two methods to introduce compliance into joints - active methods and passive methods. For active methods, a control algorithm is required to provide compliant behavior for rigid robotic joints. For example, a compliant control method for collaborative robot joints disclosed in a Chinese invention patent with publication number CN112847327A can endow collaborative robot joints with the high-precision motion characteristics of traditional industrial robots, and also enable the joints to have force control and force-position hybrid control capabilities, making the joints have compliant characteristics. However, active compliance highly depends on controllers and sensors that may malfunction, and a high-performance control system is also required to achieve fast response.

[0004] To overcome the above limitations, a passive method of generating compliance by integrating flexible elements into robotic joints has been proposed. This method can provide a faster, sensorless response to accidental collisions, and the flexible elements can absorb part of the collision energy. Elements with fixed stiffness and variable stiffness are both commonly used in compliant joints. However, it is difficult for fixed-stiffness joints to balance the response bandwidth and output impedance. In contrast, variable-stiffness joints can alleviate this problem.

[0005] One existing solution is to install a spring with adjustable number of active turns at the end of a traditional rigid drive, and then change the effective elastic coefficient of the spring to achieve the variable stiffness effect. However, if the mechanism for adjusting the number of spring turns needs to achieve a sufficiently wide adjustable stiffness range, it will occupy a large space. Another solution is to control the angle between the spring and the axis of the drive to achieve adjustable stiffness in the projection direction of the spring on the drive axis. However, affected by its trigonometric function relationship, the variable stiffness range and the accuracy requirements cannot be satisfied simultaneously. Therefore, the field of variable stiffness drives needs a linear drive with a large stiffness adjustment range and high precision. Summary of the Invention

[0006] Aiming at the deficiencies in the above background art, the present invention proposes a linear variable stiffness drive, which solves the problem that the variable stiffness drive in the prior art cannot achieve large-range and high-precision continuous stiffness adjustment.

[0007] The technical solution of the present invention is realized as follows: A linear variable stiffness actuator includes a structural support body. Fixed connectors and movable connectors are respectively provided at both ends of the structural support body. An input component is provided at one end of the structural support body close to the fixed connector. A cam structure and an output component that can slide axially are sequentially provided on the structural support body. The cam structure is in transmission cooperation with the input component, and the input component can drive the cam structure to move axially. The output component is connected to the output shaft, and the movable connector is arranged at the end of the output shaft; A leaf spring component and a stiffness adjustment component are provided on the output component. The stiffness adjustment component is in cooperation with the leaf spring component. The stiffness adjustment component can change the cooperation position with the leaf spring component, change the effective force-bearing support length of the leaf spring component, and thus change the stiffness of the leaf spring component; The leaf spring component is in cooperation with the cam structure.

[0008] Preferably, the input component includes a drive motor fixedly arranged on the structural support body. The drive motor is in transmission cooperation with a ball screw rotatably arranged on the structural support body. The ball screw is in transmission cooperation with the cam structure.

[0009] Preferably, the cam structure includes a cam connecting plate slidably matched with the structural support body. A cam is provided on the cam connecting plate. A ball screw nut is provided between the cam and the cam connecting plate and is in transmission cooperation with the ball screw through the ball screw nut; A cam working surface is provided on the cam. The cam working surface is a concave surface.

[0010] Preferably, the output component includes a support slidably arranged on the structural support body. Through holes for the cam, ball screw, and output shaft to pass through are correspondingly provided on the support. The output shaft is fixedly connected to the support.

[0011] Preferably, the leaf spring component includes a leaf spring and a leaf spring support plate fixedly arranged on the support. An elastic end of the leaf spring is fixedly connected with a cam follower rod. A roller matched with the cam working surface is provided on the cam follower rod; A chute matched with the cam follower rod is provided on the support; One side of the leaf spring is attached to the leaf spring support plate, and the other side is in cooperation with the stiffness adjustment component.

[0012] Preferably, the stiffness adjustment component includes a stiffness adjustment disk slidably arranged on the support. A leaf spring roller that can rotate is provided on the stiffness adjustment disk. The leaf spring roller is attached to the side wall of the leaf spring; A stiffness adjustment motor is provided on the support. The stiffness adjustment motor is in cooperation with a screw transmission mechanism arranged on the support and is in transmission cooperation with the stiffness adjustment disk through the screw transmission mechanism. The stiffness adjustment motor can drive the stiffness adjustment disk to slide, thereby changing the support cooperation position of the leaf spring roller relative to the leaf spring.

[0013] Preferably, the leaf spring, the roller, and the cam working surfaces on the cam are all arranged in pairs; The leaf spring rollers on the stiffness adjustment disk are arranged in pairs and are respectively located outside the corresponding leaf springs. A linear displacement sensor is provided in cooperation between the support and the structural support body.

[0014] Preferably, the structural support includes an input - side cover plate and an output - side cover plate. The input - side cover plate and the output - side cover plate are connected by a connecting cylinder. A connecting plate is provided on the input - side cover plate, and the fixed connecting member is arranged on the connecting plate; a flanged long linear bearing for slidingly mating with the output shaft is provided on the output - side cover plate.

[0015] Advantages of the present invention: By providing the structural support, a connection and support foundation is provided for the entire driver; by providing the fixed connecting member and the movable connecting member, it is convenient for the connection between the driver and other components during actual use; by providing the cam structure and the output assembly, it can move axially along the structural support under the drive of the input assembly, thereby driving the output shaft to move and achieving the driving purpose. Under the adjustment of the stiffness - adjusting assembly, the effective force - bearing support length of the leaf - spring assembly can be changed according to different requirements, thereby changing the stiffness of the leaf - spring assembly.

[0016] Compared with other existing leaf - spring - based variable - stiffness drivers, the leaf - spring assembly in the present invention only provides elastic force and does not directly participate in motion transmission, reducing the inaccuracy of elastomer modeling caused by complex deformations such as stretching and bending of the leaf spring.

[0017] The stiffness of this driver can be adjusted according to the external load. Compared with the fixed - stiffness series - elastic driver, it can ensure the force - measurement resolution at low stiffness and the control bandwidth at high stiffness.

[0018] Furthermore, this driver directly relies on the ball screw for linear - motion input. Compared with the existing linear variable - stiffness driver that directly adds a rotary - linear motion conversion mechanism at the end of the rotary driver, the transmission efficiency is higher. This driver can customize the stiffness curve of the series - elastic component of the driver by designing the cam shape and the leaf - spring structure size according to the application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 It is a three - dimensional structure schematic diagram of the present invention; Figure 2 It is an internal - structure schematic diagram of the present invention; Figure 3 It is a sectional - structure schematic diagram of the present invention; Figure 4 It is an output - assembly structure schematic diagram of the present invention; Figure 5Schematic diagram of the leaf spring assembly structure of the present invention; Figure 6 Schematic diagram of the stiffness adjustment disk structure of the present invention; In the figure: 1 - housing assembly; 2 - joint connection assembly; 3 - guiding assembly; 4 - input assembly; 5 - output assembly; 6 - leaf spring assembly; 7 - stiffness adjustment assembly; 8 - linear displacement sensor; 101 - input side cover plate; 102 - connecting cylinder; 103 - output side cover plate; 201 - input side joint connecting rod; 202 - connecting plate; 203 - output side joint connecting rod; 301 - guide rod; 302 - long linear bearing with flange; 303 - short linear bearing; 304 - long linear bearing; 401 - driving motor; 402 - small belt pulley; 403 - large belt pulley; 404 - synchronous belt; 405 - ball screw; 406 - ball screw nut; 407 - double row angular contact ball bearing; 408 - bearing fixing plate; 409 - cam connecting plate; 410 - cam; 411 - cam working surface; 501 - roller; 502 - cam follower rod; 503 - slotted plate; 504 - output side upper connecting plate; 505 - output side middle connecting plate; 506 - output side lower connecting plate; 507 - output shaft fixing plate; 508 - cam follower rod chute; 509 - stud; 510 - output shaft; 601 - leaf spring; 602 - leaf spring support plate; 603 - leaf spring connecting block; 701 - stiffness adjustment motor; 702 - coupling; 703 - trapezoidal screw; 704 - trapezoidal screw nut; 705 - short guide rod; 706 - short linear bearing with flange; 707 - angular contact ball bearing; 708 - leaf spring roller; 709 - roller rod; 710 - stiffness adjustment disk; 711 - pin; 712 - bushing. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] AsFigure 1 , 2 As shown in FIG. 3, Embodiment 1 is a linear variable stiffness actuator, which includes a structural support 1 that can provide a connection support foundation for the entire actuator. Fixed connectors 201 and movable connectors 203 are respectively provided at both ends of the structural support 1. The fixed connectors and the movable connectors facilitate the connection between the actuator and other components of the robot during actual use. An input assembly 4 is provided at one end of the structural support 1 close to the fixed connector 201. A cam structure and an output assembly 5 that can slide axially are sequentially provided on the structural support 1. The cam structure is in transmission cooperation with the input assembly 4 and the input assembly 4 can drive the cam structure to move axially. The output assembly 5 is connected to the output shaft 510, and the movable connector 203 is provided at the end of the output shaft 510. A leaf spring assembly 6 and a stiffness adjustment assembly 7 are provided on the output assembly 5. The stiffness adjustment assembly 7 cooperates with the leaf spring assembly 6. The cam structure and the output assembly 5 can move axially along the structural support under the drive of the input assembly, thereby driving the output shaft to move and achieving the driving purpose. The stiffness adjustment assembly 7 can change the cooperation position with the leaf spring assembly 6, change the effective force-bearing support length of the leaf spring assembly 6, and thus change the stiffness of the leaf spring assembly 6; the leaf spring assembly 6 cooperates with the cam structure. In this embodiment, the leaf spring assembly provides an elastic force for the cam structure and does not directly participate in the motion transmission, reducing the inaccuracy of the elastomer modeling caused by complex deformations such as stretching and bending of the leaf spring.

[0023] As a further specific implementation manner, the structural support can be optionally a closed shell or a frame structure, which provides a support foundation for the installation of other components of the actuator. When a closed shell is used, the sealing performance can be improved to avoid contaminating the internal structure. When a frame structure is used, the volume can be reduced and the weight can be reduced. In this embodiment, a closed shell is used to improve the sealing performance. Specifically, in this embodiment: the structural support 1 includes an input side cover plate 101 and an output side cover plate 103. The input side cover plate 101 and the output side cover plate 103 are connected by a connecting cylinder 102. A connecting plate 202 is provided on the input side cover plate 101, and the fixed connector 201 is provided on the connecting plate. A flange long linear bearing 302 for slidingly cooperating with the output shaft 510 is provided on the output side cover plate 103. In this embodiment, the fixed connector 201 is connected to the connecting plate 202 by a nut or welding method, and the connecting plate 202 is connected to the input side cover plate by bolts. The connecting plate is in a U-shaped structure, providing an installation space for part of the input assembly. Further, through holes are provided on both the fixed connector 201 and the movable connector 203 to facilitate connection with other components.

[0024] Further, the cam structure and the output assembly are slidably disposed on the structural support. As an alternative solution: linear sliders are fixedly connected to both the cam structure and the output assembly, and linear slide rails are fixedly arranged axially on the structural support. The sliding fit is achieved through the cooperation of the linear sliders and the linear slide rails. As another alternative solution, in this embodiment, the input side cover plate 101 and the output side cover plate 103 of the structural support are fixedly connected through a guide rod 301. To achieve stable support and meet the rationality of the structural layout, two guide rods 301 are provided in this embodiment. The two ends of the two guide rods 301 are respectively inserted into four blind holes on the input side cover plate 101 and the output side cover plate 103 for positioning and fixing. The cam structure is slidably engaged with the guide rod through a short linear bearing 303, and the output assembly 5 is slidably engaged with the guide rod through a long linear bearing 304. The guide rod is used to realize the sliding guidance and connection of the cam structure and the output assembly.

[0025] Embodiment 2, based on Embodiment 1, the input assembly 4 includes a driving motor 401 fixedly arranged on the structural support 1. The driving motor 401 is in transmission cooperation with a ball screw 405 rotatably arranged on the structural support 1, and the ball screw 405 is in transmission cooperation with the cam structure.

[0026] In this embodiment, the driving motor 401 is fixedly arranged on the input side cover plate 101 through bolts, and the output end of the driving motor 401 is in transmission cooperation with the ball screw through a belt transmission pair. Specifically, the belt transmission pair includes a small belt pulley 402, a large belt pulley 403, and a synchronous belt 404. The small belt pulley 402 is sleeved on the output shaft of the driving motor 401 through a central hole, the large belt pulley 403 is sleeved on the ball screw 405 through a central hole, and the small belt pulley 402 and the large belt pulley 403 are sleeved through the synchronous belt 404.

[0027] In addition, the cam structure includes a cam connecting plate 409 slidably engaged with the structural support 1. A cam 410 is provided on the cam connecting plate 409. A ball screw nut 406 is provided between the cam 410 and the cam connecting plate 409 and is in transmission cooperation with the ball screw 405 through the ball screw nut 406. This actuator relies on the ball screw to directly input linear motion, and has a higher transmission efficiency compared with the existing linear variable stiffness actuator that directly adds a rotation-linear motion conversion mechanism at the end of the rotary actuator.

[0028] Specifically, in this embodiment, a step is provided at the upper end of the ball screw 405. A through hole is formed in the input side cover plate 101 to allow the ball screw 405 to pass through. A bearing fixing plate 408 is fixedly attached to the input side cover plate 101. A central countersunk through hole corresponding to the through hole is provided on the bearing fixing plate 408. A double-row angular contact ball bearing 407 is installed in the central countersunk through hole. One end of the ball screw 405 passes through the double-row angular contact ball bearing 407, the bearing fixing plate 408, and the central through hole of the input side cover plate 101, and is positioned and fixed by a shaft shoulder and a nut. The middle part of the ball screw 405 passes through the central through hole of the cam connecting plate 409 and is screwed with the ball screw nut 406. The ball screw nut 406 is arranged in a countersunk through hole opened at the center of the cam 410 and matching the outer shape of the ball screw nut 406. The cam connecting plate 409 and the cam 410 are fixedly attached to form a fixed support for the ball screw nut 406.

[0029] When the driving motor 401 operates, it can drive the ball screw 405 to rotate through the belt transmission pair. Thus, under the thread fit between the ball screw 405 and the ball screw nut 406, the cam 410 where the ball screw nut 406 is located is driven to slide along the guide rod 301. Furthermore, under the cooperative action of the cam 410, the leaf spring assembly 6, and the output assembly 5, the output shaft 510 is driven to move axially, and finally the purpose of driving the movable connecting piece 203 to move is achieved.

[0030] Embodiment 3, based on Embodiment 2, as Figure 4 shown, the output assembly 5 includes a support seat slidably arranged on the structure support body 1. Through holes are correspondingly formed in the support seat to allow the cam 410, the ball screw 405, and the output shaft 510 to pass through. The output shaft 510 is fixedly connected to the support seat.

[0031] As a further specific implementation manner, specifically, in this embodiment, the support seat includes an output side upper connecting plate 504, an output side middle connecting plate 505, and an output side lower connecting plate 506 arranged in parallel in sequence. A plurality of stud bolts 509 are provided between the output side middle connecting plate and the output side lower connecting plate and are fixedly connected by bolts. The output side upper connecting plate 504 is connected to the output side middle connecting plate 505 through a slotted hole plate 503. In this embodiment, bolts are used to connect and fix adjacent plates on the support seat to form a stable support seat structure.

[0032] In addition, as Figure 5As shown, the leaf spring assembly 6 includes a leaf spring 601 fixedly arranged on a support and a leaf spring support plate 602. An elastic end of the leaf spring 601 is fixedly connected with a cam follower rod 502, and a roller 501 cooperating with the cam working surface 411 is arranged on the cam follower rod 502. In this embodiment, the leaf spring 601, the roller 501 and the cam working surface 411 on the cam 410 are all arranged in pairs for cooperation. A groove for installing the leaf spring 601 and the leaf spring support plate 602 is arranged on the output side connecting plate. The leaf spring 601 and the leaf spring support plate 602 are both fixedly arranged in the groove of the output side lower connecting plate 506 through bolts. A chute 508 cooperating with the cam follower rod 502 is arranged on the slot plate 503 of the support.

[0033] In this embodiment, leaf spring support plates 602 are arranged on the output side lower connecting plates 506 on both sides of the ball screw. Leaf springs 601 are arranged on both sides of each leaf spring support plate, and a total of four leaf springs are arranged. Two cam follower rods are arranged in total. The upper ends of the leaf springs are all connected with leaf spring connection blocks 603 through bolts. Grooved through holes are formed in the four leaf spring connection blocks 603, and the two ends of the two cam follower rods 502 are respectively sleeved through the grooved through holes. The chutes 508 on both sides of the slot plate 503 are symmetrically arranged, which can axially support the cam follower rod 502 through the chute 508 and can also meet the movement of the cam follower rod 502. One side of the leaf spring 601 is attached to the leaf spring support plate 602, and the other side is cooperated with the stiffness adjusting component 7. An opening for the leaf spring 601 to pass through and move is formed on the output side middle connecting plate.

[0034] In addition, in this embodiment, a cam working surface 411 is arranged on the cam 410. In this embodiment, the cam working surface is a concave surface, and the roller can be attached to and roll along the concave surface. In the initial position, under the action of the elastic force of the leaf spring, the roller cooperates with the lowest point of the concave surface. The two ends of the two cam follower rods 502 pass through the chutes 508 on the slot plates 503 on both sides. The four rollers 501 are respectively located on the two cam follower rods 502, and the rollers 501 are positioned by shoulders and retaining rings. The rollers can rotate relative to the cam follower rods and can cooperate with the cam working surface 411 of the cam.

[0035] Openings for the cam 410 to pass through are correspondingly formed on the output side upper connecting plate 504 and the output side middle connecting plate 505. A total of four long linear bearings 304 are arranged in this embodiment. Among them, two long linear bearings 304 are symmetrically fixed between the output side upper connecting plate 504 and the output side middle connecting plate 505 through retaining rings in the corresponding through holes on both sides and sleeved on the guide rod 301. The other two long linear bearings 304 are symmetrically fixed in the through holes on both sides of the output side lower connecting plate 506 and the central through holes of the two leaf spring support plates 602 through retaining rings and sleeved on the guide rod 301 respectively.

[0036] As a further specific embodiment, the shaft shoulder at one end of the output shaft 510 is inserted into the counterbore at the center of the lower connecting plate 506 on the output side. The output shaft fixing plate 507 is fixedly connected to the lower connecting plate 506 on the output side in a fitting manner to fix the output shaft. The other end passes through the flanged long linear bearing 302 fixed in the central through hole of the lower connecting plate 506 on the output side and is connected to the output side joint connector 20. The connection between the output shaft and the output side joint connector can be optionally welded, thread-connected or clamped by conventional means.

[0037] Embodiment 4, based on Embodiment 3, as Figure 6 shown, the stiffness adjustment assembly 7 includes a stiffness adjustment disk 710 slidably arranged on the support. The stiffness adjustment disk 710 is provided with a leaf spring roller 708 capable of rotating, and the leaf spring roller 708 is in contact with the side wall of the leaf spring 601. A stiffness adjustment motor 701 is provided on the support. The stiffness adjustment motor 701 is matched with a lead screw transmission mechanism arranged on the support and is in transmission cooperation with the stiffness adjustment disk 710 through the lead screw transmission mechanism. The stiffness adjustment motor 701 can drive the stiffness adjustment disk 710 to slide, thereby changing the support and cooperation position of the leaf spring roller 708 relative to the leaf spring 601.

[0038] Specifically, in this embodiment, a short guide rod 705 is fixedly arranged between the middle connecting plate 505 and the lower connecting plate 506 on the output side of the support. The lead screw transmission mechanism includes a trapezoidal lead screw 703 rotatably arranged between the middle connecting plate 505 and the lower connecting plate 506 on the output side of the support. Angular contact ball bearings 707 matched with the trapezoidal lead screw are arranged on the middle connecting plate 505 and the lower connecting plate 506 on the output side of the support, so as to realize the rotation of the trapezoidal lead screw. Through holes are formed in the stiffness adjustment disk 710, and a flanged short linear bearing 706 and a trapezoidal lead screw nut 704 are respectively fixed on the through holes. The flanged short linear bearing 706 is in sliding cooperation with the short guide rod 705, and the trapezoidal lead screw nut 704 is in threaded transmission cooperation with the trapezoidal lead screw 703. The trapezoidal lead screw 703 is in transmission cooperation with the output end of the stiffness adjustment motor 701 fixedly arranged on the upper connecting plate 504 on the output side through a coupling 702. Further, counterbored through holes and blind holes respectively correspond to both sides of the middle connecting plate 505 and the lower connecting plate 506 on the output side. Angular contact ball bearings 707 are inserted into the two counterbored through holes to position and fix the trapezoidal lead screw 703, and both ends of the short guide rod 705 are inserted into the two blind holes.

[0039] In this embodiment, the leaf spring rollers 708 on the stiffness adjustment disk 710 are arranged in pairs and are respectively located outside the corresponding leaf springs 601. Further, the through hole at the center of the stiffness adjustment disk 710 allows the cam 410 to pass through. Four openings for the four leaf springs to pass through are provided on the stiffness adjustment disk around the through hole. Protrusions are fixedly provided on the stiffness adjustment disk outside the openings, and roller rods 709 are inserted on the protrusions. The roller rods 709 are fixed by pins 711. Two leaf spring rollers 708 are installed on each of the four roller rods 709. The leaf spring rollers 708 are positioned by a bushing 712. The outer sidewall of each leaf spring is in contact with the two leaf spring rollers.

[0040] During actual use, when the stiffness adjustment motor 701 operates, it drives the trapezoidal lead screw 703 to rotate. Then, under the transmission cooperation between the trapezoidal lead screw 703 and the trapezoidal lead screw nut, the stiffness adjustment disk 710 is driven to move along the short guide rod 705, thereby driving the leaf spring rollers 708 on the stiffness adjustment disk 710 to move along the outer wall of the leaf spring, forcing the leaf spring rollers to press the leaf spring from the outside, changing the cooperation position with the leaf spring, and the leaf spring support plate supports the leaf spring from the inside, so as to adjust the effective force-bearing support length of the leaf spring on the roller 501 it supports, and thus adjust the stiffness of the leaf spring according to actual needs. The cooperation interval between the leaf spring rollers and the leaf spring of this driver accounts for a high proportion of the leaf spring length, which can achieve a large range of continuous stiffness adjustment. At the same time, it can also change the initially set stiffness according to the use requirements to achieve the predefined stiffness characteristics.

[0041] When the external load connected by the fixed connector 201 and the movable connector 203 is within the set range, the leaf spring applies an elastic force to the cam working surface 411 of the cam through the roller. Within the elastic force range, the power input by the input component passes through the contact between the cam and the roller, and then contacts the chute 508 through the cam follower rod where the roller is located, and is transmitted to the slot plate 503 where the chute 508 is located, and finally transmitted to the output shaft.

[0042] When it is necessary to increase the stiffness of the leaf spring, the stiffness adjustment motor is controlled to change the cooperation position between the leaf spring roller and the leaf spring, so as to change the effective support length of the leaf spring on the force received by the roller, and change the stiffness of the leaf spring. When the connected external load is too high, the output shaft 508 is axially pushed, and then the relative position between the leaf spring and the cam changes. Under the cooperation of the roller 501 and the cam working surface 411, the roller moves along the cam working surface 411, causing the leaf spring to undergo elastic deformation and absorbing the excessive external load energy generated by factors such as collisions. Compared with other existing leaf spring-based variable stiffness drivers, the leaf spring assembly in the present invention only provides elastic force and does not directly participate in motion transmission, reducing the inaccuracy of elastomer modeling caused by complex deformations such as stretching and bending of the leaf spring.

[0043] As a further specific embodiment, a linear displacement sensor 8 is cooperatively arranged between the support and the structural support. The fixed end of the linear displacement sensor 8 is fixed on the input side cover plate 101, and the measuring end of the linear displacement sensor 8 is fixed on the output side lower connecting plate 506. The linear displacement sensor 8 adopts a conventional model, and a conventional encoder is provided on the driving motor 401. According to the measured displacement between the input side cover plate 101 and the output side lower connecting plate 506 and the reading of the encoder of the driving motor 401, the relative displacement between the input component 4 and the output component can be calculated, and then the external load value of the driver can be obtained according to the deflection-displacement relationship of the driver.

[0044] In this embodiment, the stiffness of the present driver can be adjusted with the change of the external load. Compared with the constant stiffness series elastic driver, it can ensure the force measurement resolution at low stiffness and the control bandwidth at high stiffness. The present driver can be customized for the stiffness curve of the series elastic component of the driver by designing the cam shape and the size of the leaf spring structure according to the application requirements.

[0045] Embodiment 5, as a further optional embodiment, according to the actual design size requirements, the driving motor 401 can be optionally arranged inside or outside the relative connecting cylinder to meet the design requirements of different specifications and sizes or special-shaped drivers. Similarly, the ball screw can be optionally arranged coaxially or offset with the output shaft. In this embodiment, the ball screw and the output shaft are arranged coaxially, so as to better transmit the power output along the axial direction.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A linear variable stiffness actuator, comprising a structural support (1), with a fixed connector (201) and a movable connector (203) provided at both ends of the structural support (1), characterized in that: An input component (4) is provided at one end of the structural support (1) close to the fixed connecting member (201). A cam structure and an output component (5) that can slide axially are successively provided on the structural support (1). The cam structure is in driving cooperation with the input component (4), and the input component (4) can drive the cam structure to move axially. The output component (5) is connected to the output shaft (510), and the movable connecting member (203) is provided at the end of the output shaft (510). A leaf spring assembly (6) and a stiffness adjustment component (7) are provided on the output component (5). The stiffness adjustment component (7) cooperates with the leaf spring assembly (6). The stiffness adjustment component (7) can change the cooperation position with the leaf spring assembly (6), change the effective force-bearing support length of the leaf spring assembly (6), and thus change the stiffness of the leaf spring assembly (6). The leaf spring assembly (6) cooperates with the cam structure.

2. The linear variable stiffness actuator according to claim 1, characterized in that: The input component (4) includes a driving motor (401) fixedly provided on the structural support (1). The driving motor (401) is in driving cooperation with a ball screw (405) rotatably provided on the structural support (1). The ball screw (405) is in driving cooperation with the cam structure.

3. The linear variable stiffness actuator according to claim 2, characterized in that: The cam structure includes a cam connecting plate (409) slidably cooperating with the structural support (1). A cam (410) is provided on the cam connecting plate (409). A ball screw nut (406) is provided between the cam (410) and the cam connecting plate (409), and is in driving cooperation with the ball screw (405) through the ball screw nut (406). A cam working surface (411) is provided on the cam (410).

4. The linear variable stiffness actuator according to claim 3, wherein: The cam working surface (411) is a concave surface.

5. The linear variable stiffness actuator according to claim 3 or 4, characterized in that: The output component (5) includes a support slidably provided on the structural support (1). Through holes for the cam (410), the ball screw (405), and the output shaft (510) to pass through are correspondingly provided on the support. The output shaft (510) is fixedly connected to the support.

6. The linear variable stiffness actuator according to claim 5, wherein: The leaf spring assembly (6) includes a leaf spring (601) and a leaf spring support plate (602) fixedly provided on the support. An elastic end of the leaf spring (601) is fixedly connected with a cam follower rod (502). A roller (501) cooperating with the cam working surface (411) is provided on the cam follower rod (502). A chute (508) cooperating with the cam follower rod (502) is provided on the support. One side of the leaf spring (601) is in contact with the leaf spring support plate (602), and the other side cooperates with the stiffness adjustment component (7).

7. The linear variable stiffness actuator according to claim 6, characterized in that: The stiffness adjustment component (7) includes a stiffness adjustment disk (710) slidably provided on the support. A leaf spring roller (708) that can rotate is provided on the stiffness adjustment disk (710). The leaf spring roller (708) is in contact with the side wall of the leaf spring (601). A stiffness adjustment motor (701) is provided on the support. The stiffness adjustment motor (701) cooperates with a screw drive mechanism provided on the support and is in driving cooperation with the stiffness adjustment disk (710) through the screw drive mechanism. The stiffness adjustment motor (701) can drive the stiffness adjustment disk (710) to slide, thereby changing the support cooperation position of the leaf spring roller (708) relative to the leaf spring (601).

8. The linear variable stiffness actuator according to claim 7, characterized in that: The leaf springs (601), rollers (501), and cam working surfaces (411) on the cams (410) are all arranged in paired cooperation; the leaf spring rollers (708) on the stiffness adjustment disc (710) are arranged in paired cooperation and are respectively located outside the corresponding leaf springs (601).

9. The linear variable stiffness actuator according to claim 8, wherein: A linear displacement sensor (8) is cooperatively arranged between the support and the structural support body (1).

10. The linear variable stiffness actuator according to any one of claims 1 to 4, 6 to 9, characterized in that: The structural support body (1) includes an input side cover plate (101) and an output side cover plate (103). The input side cover plate (101) and the output side cover plate (103) are connected by a connecting cylinder (102). A connecting plate (202) is provided on the input side cover plate (101), and a fixed connecting member (201) is arranged on the connecting plate; a flanged long linear bearing (302) for sliding cooperation with the output shaft (510) is provided on the output side cover plate (103).

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