An underactuated robotic finger with variable stiffness

Abstract

The present invention relates to the field of manipulator technology, and specifically discloses an under-actuated manipulator finger with variable stiffness, comprising a finger base, a variable stiffness mechanism, a first finger joint, a second finger joint, and a third finger joint, wherein one end of the first finger joint is hinged to one end of the second finger joint, and the other end of the second finger joint is hinged to one end of the third finger joint, the first finger joint comprises a front end and a rear end, the variable stiffness mechanism is connected between the front end and the rear end, one end of the second finger joint is hinged to the front end, the rear end is hinged to the finger base, the rear end is hinged to a coupling crank, one end of the coupling crank is hinged to a push rod, the third finger joint is hinged to a push rod, one end of the push rod is provided with a support rod, and the two ends of the support rod are respectively hinged to the push rod and the head end. The advantage of the present invention is that it combines the grasping characteristics of rigid and flexible manipulators, making the manipulator's grasping ability stronger.

Description

Technical Field

[0001] The present invention relates to the technical field of manipulators, in particular to an under-actuated manipulator finger with variable stiffness. Background Art

[0002] With the continuous development of society, higher requirements will be placed on manipulators as end effectors. Underactuated manipulators have become a hot topic of research due to their simple control and strong adaptability. However, different types of underactuated manipulators have different limitations. Traditional rigid manipulators have the advantages of strong grasping force and simple control, but their envelope and adaptability are relatively weak; although flexible manipulators have strong adaptability and good envelope, their grasping force is small and they are not suitable for grasping relatively large objects; in recent years, variable stiffness manipulators developed based on new materials aim to combine the advantages of rigid manipulators and flexible manipulators to improve grasping capabilities, but their production costs are relatively high and the control is also more complicated. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an under-actuated mechanical finger with variable stiffness.

[0004] The objectives of the present invention are achieved through the following technical solutions: A variable stiffness under-actuated mechanical finger, comprising a finger base, a variable stiffness mechanism, a first finger joint, a second finger joint and a third finger joint, one end of the first finger joint is hinged to one end of the second finger joint, the other end of the second finger joint is hinged to one end of the third finger joint, the first finger joint includes a front end and a rear end, the variable stiffness mechanism is connected between the front end and the rear end, one end of the second finger joint is hinged to the front end, the rear end is hinged to the finger base, the rear end is hinged to a coupling crank, one end of the coupling crank is hinged to a push rod, the third finger joint is hinged to a push rod, one end of the push rod is provided with a support rod, the two ends of the support rod are respectively hinged to the push rod and the head end.

[0005] Specifically, a driving rod is hinged on the coupling crank, one end of the driving rod is hinged on a driving slider, a sliding rod is provided on the finger base, and the driving slider is slidably connected to the sliding rod.

[0006] Specifically, the variable stiffness mechanism includes a slider, a spring steel strip, a memory alloy spring, a guide rod and a mounting bracket. The mounting bracket is fixedly arranged on the rear end, the two guide rods are arranged on the mounting bracket and the rear end, the slider is slidably connected to the guide rod, and a sliding hole is provided on the slider. The two ends of the spring steel strip are respectively connected to the front end and the rear end, the spring steel strip is slidably connected to the sliding hole of the slider, and the two ends of the memory alloy spring are respectively connected to the rear end and the slider.

[0007] Specifically, a compression spring is sleeved on the guide rod.

[0008] The present invention has the following advantages:

[0009] The under-actuated robotic finger with variable stiffness of the present invention has two grasping modes, rigid and flexible, and can switch between different grasping modes according to different grasping objects. Through the variable stiffness design, the robotic finger combines the grasping characteristics of rigid and flexible manipulators, making its grasping ability stronger. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the overall structure of the under-actuated robotic finger of the present invention;

[0011] Figure 2 for Figure 1 Schematic diagram of the enlarged structure at A in the middle;

[0012] In the figure: 1-rear end, 2-coupling crank, 3-slide rod, 4-driving slider, 5-finger base, 7-push rod, 8-front end, 9-second finger joint, 10-third finger joint, 11-slide block, 12-memory alloy spring, 13-compression spring, 14-spring steel belt, 15-thrust rod, 17-variable stiffness mechanism, 18-mounting frame. DETAILED DESCRIPTION

[0013] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein can be arranged and designed in various different configurations.

[0014] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0015] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0016] The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0017] like Figure 1-Figure 2As shown, a variable stiffness under-actuated mechanical finger includes a finger base 5, a variable stiffness mechanism 17, a first finger joint, a second finger joint 9 and a third finger joint 10, one end of the first finger joint is hinged to one end of the second finger joint 9, the other end of the second finger joint 9 is hinged to one end of the third finger joint 10, the first finger joint includes a front end 8 and a rear end 1, the variable stiffness mechanism 17 is connected between the front end 8 and the rear end 1, one end of the second finger joint 9 is hinged to the front end 8, the rear end 1 is hinged to the finger base 5, the rear end 1 is hinged to a coupling crank 2, one end of the coupling crank 2 is hinged to a push rod 7, the third finger joint 10 is hinged to a push rod 15, one end of the push rod 15 is provided with a support rod, the two ends of the support rod are respectively hinged to the push rod 7 and the head end 8. The under-actuated robotic finger in this embodiment has two grasping modes, namely a rigid grasping mode and a flexible grasping mode, which are specifically adjusted by a variable stiffness mechanism 17. In this embodiment, there are three finger joints, which are connected in series in sequence, and the three finger joints are driven by a connecting rod mechanism to grasp objects, wherein the first finger joint includes a front end 8 and a rear end 1, and the variable stiffness mechanism 17 is set between the front end 8 and the rear end 1. The grasping mode can be adjusted by adjusting the variable stiffness mechanism 17 to change the characteristics of the first finger joint. The second finger joint 9 is plate-shaped, and a bending portion is provided at one end of the front end 8. One end of the second finger joint 9 is hinged to the end of the bending portion. The third finger joint 10 is a triangular structure, one corner of which is hinged to one end of the second finger joint 9, and the other corner is hinged to one end of the push rod 15. A support rod is provided at the other end of the push rod 15, and the support rod and the push rod 15 form a T-shaped structure. The end at which the push rod 7 is hinged to the support rod is a bending The folding setting is that one end of the support rod is hinged at the connection between the front end 8 and the bending part. When in use, multiple under-actuated mechanical fingers work synchronously to grasp the object. When grasping, the coupling crank 2 is driven by external force to rotate around the hinge point with the rear end 1. The hinge point of the coupling crank 2 and the rear end 1 is the same as the hinge point of the rear end 1 and the finger base 5. When the coupling crank 2 rotates, it drives the first finger joint to rotate, and the first finger joint rotates and fits on the object. Then the coupling crank 2 continues to rotate to lift the support rod 7. In this way, the support rod rotates around the hinge point with the end head 8. The support rod lifting push rod 15 can drive the second finger joint 9 to rotate around the hinge point with the end head 8 and drive the third finger joint 10 to rotate around the hinge point with the second finger joint 9, so that the second finger joint 9 first fits the surface of the object, and then the third finger joint 10 fits the surface of the object. In this way, each finger joint contacts the object to be grasped in turn, and generates corresponding contact force to achieve envelope grasping of the object.

[0018] Furthermore, a drive rod is hingedly connected to the coupling crank 2, one end of which is hingedly connected to a drive slider 4. A slide rod 3 is provided on the finger base 5, and the drive slider 4 is slidably connected to the slide rod 3. In this embodiment, the slide rod 3 is provided on the finger base 5 to guide the drive slider 4. Under the action of an external force, the drive slider 4 moves along the slide rod 3, thereby driving the slider to drive the drive rod to push the coupling crank 2. This enables the coupling crank 2 to rotate about the hinge point with the rear end 1, thereby grasping an object. A layer of rubber is attached to the surfaces of the front end 8, the rear end 1, the second finger joint 9, and the third finger joint 10. The rubber increases the contact area between the finger and the object during grasping.

[0019] Furthermore, the variable stiffness mechanism 17 includes a slider 11, a spring steel strip 14, a memory alloy spring 12, a guide rod and a mounting bracket 18. The mounting bracket 18 is fixedly arranged on the rear end 1, and the two guide rods are arranged on the mounting bracket 18 and the rear end 1. The slider 11 is slidably connected to the guide rod, and a sliding hole is provided on the slider 11. The two ends of the spring steel strip 14 are respectively connected to the front end 8 and the rear end 1, and the spring steel strip 14 is slidably connected to the sliding hole of the slider 11. The two ends of the memory alloy spring 12 are respectively connected to the rear end 1 and the slider 11, and a compression spring 13 is provided on the guide rod. The variable stiffness mechanism 17 in this embodiment is used to adjust the grasping mode of the under-actuated mechanical finger. The front end 8 and the rear end 1 are connected by a spring steel belt 14. The spring steel belt 14 can be bent, and the slider 11 is slidably set on the guide rod. It can move on the spring steel belt 14 under the drive of the memory alloy spring 12, so that the effective length of the spring steel belt 14 between the front end 8 of the first finger joint and the slider 11 changes, thereby changing the characteristics of the entire finger, achieving the effect of variable stiffness. When the slider 11 is in a position close to the front end 8, the memory alloy spring 12 is in its original length state, and the effective length of the spring steel belt 14 between the front end 8 of the first finger joint and the slider 11 is shorter, which is a rigid grasping mode. If you want to switch to the flexible mode, you can energize the memory alloy spring 12 to heat and contract it, drive the slider 11 to move, so that the effective length of the spring steel belt 14 between the front end 8 of the first finger joint and the slider 11 becomes longer, and switch It is a flexible mode. If you want to achieve a conversion from flexibility to rigidity, you can stop energizing and heating the memory alloy spring 12. The slider 11 can be driven to move by the restoring force of the compression spring 13, so that the effective length of the spring steel strip 14 between the front end 8 of the first finger joint and the slider 11 becomes shorter, thereby realizing the conversion from the flexible mode to the rigid mode. In the flexible mode, since the front end 8 and the rear end 1 are connected by the spring steel strip 14, after the rear end 1 fits with the surface of the object, the force transmitted to the push rod 7 when the coupling crank 2 continues to rotate acts on the hinge with the front end 8. At this time, since the spring steel strip 14 between the front end 8 and the slider 11 is longer, the force of the push rod 7 acts on the front end 8 through the support rod, causing the spring steel strip 14 to bend and fit the surface of the object. This can adapt to the grasping of objects with special shapes. By adjusting the length of the spring steel strip 14 between the front end 8 and the slider 11, the bending degree of the spring steel strip 14 can be adjusted, thereby achieving the adjustment of the degree of flexibility.

[0020] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make many possible changes and modifications to the technical solution of the present invention using the above technical content, or modify it into an equivalent embodiment with equivalent changes. Therefore, any changes, modifications, equivalent changes, and modifications made to the above embodiments based on the technology of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the present technical solution.

Claims

1. An underactuated robotic finger with variable stiffness, characterized by: The finger base (5) comprises a finger joint, a variable stiffness mechanism (17), a first finger joint, a second finger joint (9) and a third finger joint (10), wherein one end of the first finger joint is hinged to one end of the second finger joint (9), and the other end of the second finger joint (9) is hinged to one end of the third finger joint (10), the first finger joint comprises a front end (8) and a rear end (1), the variable stiffness mechanism (17) is connected between the front end (8) and the rear end (1), one end of the second finger joint (9) is hinged to the front end (8), the rear end (1) is hinged to the finger base (5), the rear end (1) is hinged to a coupling crank (2), one end of the coupling crank (2) is hinged to a push rod (7), the third finger joint (10) is hinged to a push rod (15), one end of the push rod (15) is provided with a support rod, and the two ends of the support rod are respectively hinged to the push rod (7) and the front end (8); A driving rod is hinged on the coupling crank (2), one end of the driving rod is hinged on a driving slider (4), a sliding rod (3) is provided on the finger base (5), and the driving slider (4) is slidably connected to the sliding rod (3); The variable stiffness mechanism (17) comprises a slider (11), a spring steel strip (14), a memory alloy spring (12), a guide rod and a mounting frame (18), wherein the mounting frame (18) is fixedly arranged on the rear end (1), and the two guide rods are arranged on the mounting frame (18) and the rear end (1), the slider (11) is slidably connected to the guide rod, and a sliding hole is provided on the slider (11), the two ends of the spring steel strip (14) are respectively connected to the front end (8) and the rear end (1), the spring steel strip (14) is slidably connected to the sliding hole of the slider (11), and the two ends of the memory alloy spring (12) are respectively connected to the rear end (1) and the slider (11).

2. The under-actuated robotic finger with variable stiffness according to claim 1, characterized in that: A compression spring (13) is sleeved on the guide rod.

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