A variable stiffness end effector based on the lever principle

Abstract

The present invention discloses a variable stiffness end effector based on the lever principle, comprising: an upper shell, a lever assembly, a spring assembly, a stiffness adjustment assembly and a housing, wherein the lever assembly comprises a lever force column, a lever connector, a lever mounting seat and a lever optical axis, the spring assembly comprises an optical axis slider, a spring guide seat, a spring, a linear slider and a linear guide rail, the lever assembly is connected to the spring assembly, the stiffness adjustment assembly contacts the spring assembly, the spring assembly and the lever assembly slide relative to each other along the lever optical axis, the optical axis slider and the lever optical axis in the lever assembly constrain each other and slide relative to each other, the spring guide seat and the stiffness adjustment assembly contact each other and displace relative to each other, the spring assembly is driven to slide linearly along the lever optical axis, and thus the resistance arm of the lever is changed. The present invention has a simple and compact structure and good adjustability, and can achieve stepless stiffness adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of robot end control, and in particular to a variable stiffness end effector based on the lever principle. Background Art

[0002] With the continuous development of robotics technology, robots have played an increasingly important role in industrial production and are playing an increasingly important role in the industrial production process. The traditional furniture grinding and polishing process has a harsh processing environment, which poses a great threat to the health of workers who perform manual grinding. Manual grinding is also inefficient. Therefore, using robotic arms to replace manual grinding and polishing has a good market prospect. For tasks such as grinding and polishing, robotic arms must interact with the environment, and rigid ends often cannot show the flexibility of human arms, so they cannot achieve the processing effect of manual grinding. However, in the current field of robot end effectors, flexible actuators account for a small proportion, and their stiffness is often uncontrollable, which cannot meet the needs of different processing tasks.

[0003] For example, patent publication number CN107738268A is a variable stiffness end effector based on the lever principle, which uses a cam plate in the stiffness adjustment mechanism to adjust the distance between the input and output ends of the joint, thereby adjusting the output stiffness characteristics;

[0004] For example, the patent publication number CN106737586A discloses a symmetrical variable stiffness flexible actuator based on a variable fulcrum. The actuator has two sets of stiffness adjustment structures symmetrically arranged along the center of the power output mechanism. The actuator uses a gear with an Archimedean spiral groove to adjust the fulcrum and change the lever arm length, thereby achieving a wide range of stiffness adjustment, allowing the actuator to be adjusted from zero stiffness to full stiffness.

[0005] However, the above-mentioned existing devices are all used in the field of robot joints, mainly dealing with stiffness adjustment in the arc direction, and do not involve the field of robot terminals, nor do they deal with stiffness adjustment in the linear direction. Summary of the Invention

[0006] In order to overcome the defects and shortcomings of the prior art, the present invention provides a variable stiffness end effector based on the lever principle. The present invention has a simple and compact structure, good adjustability, and can achieve stepless stiffness adjustment.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a variable stiffness end effector based on the lever principle, comprising an upper housing, a lever assembly, a spring assembly, a stiffness adjustment assembly, and a shell. The upper housing is movably connected to the shell, the lever assembly and the spring assembly are arranged in the shell, and the stiffness adjustment assembly is in contact with the spring assembly.

[0009] The lever assembly includes a lever force column, a lever connecting piece, a lever mounting seat and a lever optical axis;

[0010] The lever mounting seat is fixedly connected to the inner wall of the housing, and one end of the lever force column is connected to the upper housing;

[0011] The lever mounting seat is movably connected to one end of the lever connecting member and one end of the lever optical axis respectively, the other end of the lever connecting member is movably connected to the lever force column, and the other end of the lever force column is movably connected to the lever optical axis. The lever force column, the lever connecting member, the lever mounting seat, and the lever optical axis together form a parallelogram connecting rod structure, and the plane where the parallelogram of the connecting rod structure is located is perpendicular to the plane where the upper shell is located;

[0012] The spring assembly includes an optical axis slider, a spring guide seat, a spring, a linear slider, and a linear guide rail;

[0013] The top of the optical axis slider is provided with a first groove, the first groove is matched with the lever optical axis, the optical axis slider slides along the extension direction of the lever optical axis, and the bottom of the optical axis slider is connected to the spring guide seat.

[0014] One end of the spring is connected to the spring guide seat, and the other end of the spring is connected to the linear slider. A sleeve is provided on the outside of the spring. A gap is provided between the sleeve and the spring guide seat. The sleeve is fixedly connected to the linear slider. The linear slider is provided with a second groove. The second groove is matched with the linear guide rail, and the linear slider slides along the extension direction of the linear guide rail.

[0015] The linear guide rail is arranged parallel to the optical axis of the lever and is in the same plane as the parallelogram of the connecting rod structure;

[0016] The stiffness adjustment component is used to drive the optical axis slider connected to the spring guide seat to slide along the lever optical axis.

[0017] As a preferred technical solution, the stiffness adjustment assembly includes a drive motor and a stiffness adjustment disk;

[0018] The driving motor is connected to the stiffness adjustment disk, driving the stiffness adjustment disk to rotate. The stiffness adjustment disk is provided with a motion trajectory line hole. The sleeve passes through the motion trajectory line hole and contacts the motion trajectory line hole. Under the push of the stiffness adjustment disk, the sleeve moves relative to the stiffness adjustment disk along the cam track, and the optical axis slider connected to the spring guide seat is driven to slide linearly along the optical axis of the lever.

[0019] As a preferred technical solution, the motion track line hole adopts a straight cam track line hole, or an Archimedean spiral cam track line hole.

[0020] As a preferred technical solution, an actuator base is further provided, and the housing is fixedly connected to the actuator base.

[0021] As a preferred technical solution, the actuator base is provided with an internal cavity, and the linear guide rail and the drive motor are arranged in the internal cavity.

[0022] As a preferred technical solution, the actuator base is further provided with a flange, and the flange is used to connect to external equipment.

[0023] As a preferred technical solution, the lever assembly and the spring assembly are provided in at least one group, the stiffness adjustment assembly is provided in one group, the lever assembly is connected to the spring assembly correspondingly, and the stiffness adjustment assembly is in contact with each group of spring assemblies.

[0024] As a preferred technical solution, the upper shell is movably connected to the outer shell, and the upper shell and the outer shell are relatively movable in the vertical direction.

[0025] As a preferred technical solution, the lever mounting seat is connected to one end of the lever connecting member and one end of the lever optical axis through a hinge respectively, the other end of the lever connecting member is connected to the lever force column through a hinge, and the other end of the lever force column is connected to the lever optical axis through a hinge.

[0026] As a preferred technical solution, the first groove is a circular groove that matches and fits with the lever optical axis, and the second groove is a trapezoidal groove that matches and fits with the linear guide rail.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The present invention utilizes the lever principle to transmit the contact force between the end and the outside world through a lever assembly based on the lever principle, and realizes the infinite change of the length of the lever resistance arm through the mutual cooperation of the rod assembly, the spring assembly, and the stiffness adjustment assembly, thereby enabling the end actuator to achieve the infinite variable stiffness effect.

[0029] (2) The present invention utilizes the cam track on the stiffness adjustment disk to make the spring slider slide relative to each other, thereby causing the lever resistance arm to change. Different variable stiffness effects can be achieved by presetting the stiffness adjustment disk with different cam tracks. The adjustability is good, and the adjustment accuracy is basically not affected by external change factors, which enables the robotic arm to meet the needs of various production scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a cross-sectional view of the overall structure of the variable stiffness end effector based on the lever principle of the present invention;

[0031] Figure 2It is a sectional isometric view of the variable stiffness end effector based on the lever principle of the present invention;

[0032] Figure 3 Schematic diagram of an explosion of a variable stiffness end effector based on the lever principle of the present invention;

[0033] Figure 4 Schematic diagram of the structure of the lever assembly, spring assembly and stiffness adjustment assembly of the present invention;

[0034] Figure 5 It is a structural schematic diagram of the lever assembly of the present invention;

[0035] Figure 6 It is a structural schematic diagram of the spring assembly of the present invention;

[0036] Figure 7 This is a structural schematic diagram of a linear stiffness adjustment disk used in the present invention;

[0037] Figure 8 This is a structural schematic diagram of the stiffness adjustment disk of the present invention using an Archimedean spiral stiffness adjustment disk.

[0038] Among them, 1-upper shell, 2-lever force column, 3-lever connector, 4-lever mounting seat, 5-lever optical axis, 6-optical axis slider, 7-spring guide seat, 8-spring, 9-linear slider, 10-linear guide rail, 11-drive motor, 12-stiffness adjustment disk, 13-housing, 14-actuator base. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] Example

[0041] like Figures 1-6 As shown, this embodiment provides a variable stiffness end effector based on the lever principle, which is mainly aimed at the compliance adaptation of the contact surface during the interaction process of robot grinding and polishing, etc., and includes an upper shell 1, a lever assembly, a spring assembly, a stiffness adjustment assembly, a shell 13 and an actuator base 14. The upper shell 1 is movably connected to the shell 13, the lever assembly and the spring assembly are arranged in the shell 13, and the stiffness adjustment assembly is in contact with the spring assembly;

[0042] In this embodiment, the lever assembly and the spring assembly are provided in at least one group, preferably three groups, and the stiffness adjustment assembly is provided in one group. The lever assembly and the spring assembly are connected one-to-one, and the stiffness adjustment assembly is in contact with each group of spring assemblies.

[0043] In this embodiment, the upper shell 1 is located at the upper part of the variable stiffness terminal as a whole. Its upper surface has screw holes, which can be used to install other terminal devices to meet specific work requirements. The lower surface of the upper shell 1 is fixedly connected to the lever force column 2 to transmit the force received from the upper shell 1 from the outside to the internal components. The upper shell 1 is slightly smaller than the outer shell 13 and is surrounded by the outer shell 13 as a whole. The range of its movement is limited by the outer shell 13, ensuring the overall stability. The outer shell 1 is nested inside the outer shell 13 and can move relative to the outer shell 13 in the vertical direction.

[0044] In this embodiment, the housing 13 has a mounting base inside for secure connection to the lever mounting base 4. Its lower portion is fixedly connected to the actuator base 14. The housing 13 encloses most of the variable stiffness end components, providing protection and securement. The actuator base 14 is located below the entire variable stiffness end, with its upper portion fixedly connected to the housing 13. The upper portion of the actuator base 14 defines a cavity within which the linear guide 10 and drive motor 11 are securely connected, providing a mounting and force transmission foundation. The lower portion of the actuator base 14 has a flange that can be securely connected to external equipment, such as a robotic arm, allowing the variable stiffness end to be mounted on other equipment.

[0045] Combine Figure 5As shown, the lever assembly includes a lever column 2, a lever connector 3, a lever mounting seat 4, and a lever optical axis 5. The lever column 2, the lever connector 3, the lever mounting seat 4, and the lever optical axis 5 are all rod-shaped components with two hinges, wherein the lever column 2, the lever connector 3, and the lever mounting seat 4 are rectangular rods, while the lever optical axis 5 is a cylindrical rod with a smooth surface and a low surface roughness. The hinges can be located at both ends of the assembly or at one end thereof. The lever column 2 is fixed to the lever connector 3 and the lever optical axis 5 respectively by hinges, that is, the lever column 2 can rotate around the hinges relative to the lever connector 3 and the lever optical axis 5 respectively. Similarly, the lever mounting seat 4 is also fixed to the lever connector 3 and the lever optical axis 5 respectively by hinges. Therefore, the lever column 2, the lever connector 3, the lever mounting seat 4, and the lever optical axis 5 can all rotate relative to adjacent components. The lever force column 2 and the lever mounting seat 4 remain parallel, and the lever connecting member 3 and the lever optical axis 5 remain relatively parallel. Therefore, the lever force column 2, the lever connecting member 3, the lever mounting seat 4, and the lever optical axis 5 together form a parallelogram connecting rod structure, and the plane of the parallelogram of the connecting rod structure is perpendicular to the plane of the upper shell. Since the lever mounting seat 4 is fixed to the shell 13 and remains parallel to the cylindrical surface of the shell 13, the lever force column 2, as a parallelogram connecting rod member opposite to the lever mounting seat 4, will also remain parallel to the cylindrical surface of the shell 13 during movement. In addition, since the lever force column 2 is fixed to the upper shell 1, it first receives the force transmitted from the outside and then transmits the force to the internal components. Therefore, in the lever assembly, the lever connecting member 3 is the power arm and the lever optical axis 5 is the resistance arm.

[0046] Combine Figure 6As shown, the spring assembly of this embodiment includes an optical axis slider 6, a spring guide seat 7, a spring 8, a linear slider 9 and a linear guide rail 10. In the spring assembly, the upper portion of the optical axis slider 6 has an incomplete circular groove, which is interlocked with the lever optical axis 5. The surface roughness of the groove is low, and it can slide relative to the lever optical axis 5. The cross-section of the lever optical axis 5 is circular. When the spring assembly slides linearly along the linear guide rail and the lever optical axis, the distance between the optical axis slider and the root hinge of the lever optical axis will change relatively. The lower portion of the optical axis slider 6 is connected to the upper portion of the spring guide seat 7 by a hinge, and the optical axis slider 6 and the spring guide seat 7 can rotate relative to each other. The spring 8 is installed in the spring guide seat 7, and the spring guide seat 7 limits the range of motion of the spring 8, so that the spring 8 can only perform telescopic movement in a linear direction. A sleeve (i.e., a continuous cylindrical surface in the figure) is sleeved on the outside of the spring 8. A gap is provided between the sleeve 8 and the spring guide seat 7. The sleeve is fixedly connected to the linear slider 9. The linear slider 9 is a slider with a trapezoidal groove, which is engaged with the linear guide rail 10 fixed to the actuator base 14. The linear guide rail 10 is a column with a trapezoidal cross-section. The surface roughness of the linear slider 9 and the linear guide rail 10 is relatively low, and the two can slide linearly relative to each other. The linear guide rail is arranged parallel to the optical axis of the lever and is in the same plane as the parallelogram of the connecting rod structure; therefore, the spring assembly of this embodiment can also undergo linear expansion and contraction while undergoing linear sliding. When linear expansion and contraction occur, the parallelogram connecting rod composed of the lever assembly connected to the upper part of the spring assembly can ensure that the linear expansion and contraction of the spring assembly is always in the vertical direction, that is, it ensures that the force is along the vertical direction.

[0047] In this embodiment, the stiffness adjustment assembly includes a drive motor 11 and a stiffness adjustment disk 12, wherein the drive motor 11 is fixed in the cavity at the top of the actuator base 14, and the stiffness adjustment disk 12 is a disk with a hollow track, which is slightly smaller than the cavity of the actuator base 14. The hollow track is generally called a cam track, and the track width is slightly larger than the continuous cylindrical surface at the bottom of the spring guide seat 7. The stiffness adjustment disk 12 generally has three cam tracks, which are respectively in contact with the sleeves on the outside of the springs in the three groups of spring assemblies (i.e., the continuous cylindrical surface in the figure). The sleeves can move relative to the stiffness adjustment disk 12 along the cam track under the push of the stiffness adjustment disk 12. In addition, the cam track on the stiffness adjustment disk 12 can be specially designed, such as Figure 7 As shown, the stiffness adjustment disk adopts a linear stiffness adjustment disk, that is, the cam track is set to a linear cam track, such as Figure 8 As shown, the stiffness adjustment disk is an Archimedean spiral stiffness adjustment disk, that is, the cam track is set to an Archimedean spiral cam track. Different cam tracks will have different pushing effects on the spring guide seat 7 under the drive of the drive motor 11, that is, different stiffness adjustment effects can be achieved.

[0048] In this embodiment, when the variable stiffness end effector based on the lever principle is in operation, the upper shell 1 will be subjected to a certain force from the outside, and the force will be transmitted to the lever force column 2 in the lever assembly, and finally to the lever optical axis 5. The lever optical axis 5 will transmit the force to the optical axis slider 6 in the spring assembly connected to it, and the optical axis slider 6 will transmit the force to the spring 8. The force will cause the spring 8 to be compressed to a certain extent, and then the force will be transmitted in sequence through the spring guide seat 7, the linear slider 9, the linear guide rail 10, and the actuator base 14, and finally the force will be transmitted to the external equipment connected to the flange of the actuator base 14, such as a robotic arm. The principle of stiffness adjustment is primarily to regulate the force transmitted from the lever optical axis 5 to the optical axis slider 6. For a lever assembly consisting of a lever column 2, a lever connector 3, a lever mounting seat 4, and a lever optical axis 5, the external force transmitted from the upper housing 1 to the lever column 2 can be considered the lever's power, while the force transmitted from the lever optical axis 5 to the optical axis slider 6 can be considered the lever's resistance. The power arm remains unchanged, while stiffness adjustment in the present invention adjusts the length of the resistance arm in the lever. During stepless stiffness adjustment, the drive motor 11 rotates the stiffness adjustment disk 12. The cam track on the stiffness adjustment disk 12 pushes the sleeve outside the spring to slide linearly along the linear guide 10. Simultaneously, the optical axis slider 6, connected to the spring guide seat 7, is also driven to slide linearly along the lever optical axis 5. This changes the length of the resistance arm of the force transmitted from the lever optical axis 5 to the optical axis slider 6, thereby changing the force transmitted from the lever optical axis 5 to the optical axis slider 6. Consequently, as the force transmitted by the optical axis slider 6 to the spring 8 changes, the degree of compression of the spring 8 also varies, and thus the stiffness characteristics of the variable stiffness end as a whole also vary. Because the stiffness adjustment assembly controls the infinitely variable distance of the optical axis slider 6 along the lever optical axis 5, the stiffness adjustment is also infinitely variable.

[0049] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A variable stiffness end effector based on the lever principle, characterized in that: The device comprises an upper shell, a lever assembly, a spring assembly, a stiffness adjustment assembly and an outer shell, wherein the upper shell is movably connected to the outer shell, the lever assembly and the spring assembly are arranged in the outer shell, and the stiffness adjustment assembly is in contact with the spring assembly; The lever assembly includes a lever force column, a lever connecting piece, a lever mounting seat and a lever optical axis; The lever mounting seat is fixedly connected to the inner wall of the housing, and one end of the lever force column is connected to the upper housing; The lever mounting seat is movably connected to one end of the lever connecting member and one end of the lever optical axis respectively, the other end of the lever connecting member is movably connected to the lever force column, and the other end of the lever force column is movably connected to the lever optical axis. The lever force column, the lever connecting member, the lever mounting seat, and the lever optical axis together form a parallelogram connecting rod structure, and the plane where the parallelogram of the connecting rod structure is located is perpendicular to the plane where the upper shell is located; The spring assembly includes an optical axis slider, a spring guide seat, a spring, a linear slider, and a linear guide rail; The top of the optical axis slider is provided with a first groove, the first groove is matched with the lever optical axis, the optical axis slider slides along the extension direction of the lever optical axis, and the bottom of the optical axis slider is connected to the spring guide seat. One end of the spring is connected to the spring guide seat, and the other end of the spring is connected to the linear slider. A sleeve is provided on the outside of the spring. A gap is provided between the sleeve and the spring guide seat. The sleeve is fixedly connected to the linear slider. The linear slider is provided with a second groove. The second groove is matched with the linear guide rail, and the linear slider slides along the extension direction of the linear guide rail. The linear guide rail is arranged parallel to the optical axis of the lever and is in the same plane as the parallelogram of the connecting rod structure; The stiffness adjustment component is used to drive the optical axis slider connected to the spring guide seat to slide along the lever optical axis.

2. The variable stiffness end effector based on the lever principle according to claim 1 is characterized in that: The stiffness adjustment assembly includes a drive motor and a stiffness adjustment disk; The driving motor is connected to the stiffness adjustment disk, driving the stiffness adjustment disk to rotate. The stiffness adjustment disk is provided with a motion trajectory line hole. The sleeve passes through the motion trajectory line hole and contacts the motion trajectory line hole. Under the push of the stiffness adjustment disk, the sleeve moves relative to the stiffness adjustment disk along the cam track, and the optical axis slider connected to the spring guide seat is driven to slide linearly along the optical axis of the lever.

3. The variable stiffness end effector based on the lever principle according to claim 2, characterized in that: The motion track line hole adopts a straight cam track line hole, or adopts an Archimedean spiral cam track line hole.

4. The variable stiffness end effector based on the lever principle according to claim 2, characterized in that: An actuator base is also provided, and the shell is fixedly connected to the actuator base.

5. The variable stiffness end effector based on the lever principle according to claim 4 is characterized in that: The actuator base is provided with an internal cavity, and the linear guide rail and the drive motor are arranged in the internal cavity.

6. The variable stiffness end effector based on the lever principle according to claim 4 is characterized in that: The actuator base is further provided with a flange, which is used to connect to external equipment.

7. The variable stiffness end effector based on the lever principle according to claim 1, characterized in that: The lever assembly and the spring assembly are provided in at least one group, the stiffness adjustment assembly is provided in one group, the lever assembly is connected to the spring assembly correspondingly, and the stiffness adjustment assembly is in contact with each group of spring assemblies.

8. The variable stiffness end effector based on the lever principle according to claim 1, characterized in that: The upper shell is movably connected to the outer shell, and the upper shell and the outer shell are relatively movable in a vertical direction.

9. The variable stiffness end effector based on the lever principle according to claim 1, characterized in that: The lever mounting seat is connected to one end of the lever connecting member and one end of the lever optical axis through a hinge respectively, the other end of the lever connecting member is connected to the lever force column through a hinge, and the other end of the lever force column is connected to the lever optical axis through a hinge.

10. The variable stiffness end effector based on the lever principle according to claim 1, characterized in that: The first groove is a circular groove, which is matched and engaged with the lever optical axis, and the second groove is a trapezoidal groove, which is matched and engaged with the linear guide rail.

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