Tactile perception and flat gripping bionic robotic finger mechanism and tactile recognition method

Abstract

This invention provides a tactile sensing and flat gripping bionic robotic finger mechanism and tactile recognition method, relating to the field of robotic tactile sensing technology. The finger employs a three-layer sandwich structure consisting of a phalanx unit, a piezoresistive sensing unit, and a bionic nail unit. These three units are fixedly encapsulated with silicone material to form a flexible fingertip structure and nail bed structure. The bionic nail unit is used to contact objects and transmit contact force to the piezoresistive sensing unit within the nail bed region. The piezoresistive sensing unit is located on the surface of the phalanx unit and deforms under external contact force, causing a change in resistance, thereby acquiring tactile information. This structure achieves effective sensing of the contact state, while the rigid nail structure enhances the gripping stability of flat objects. Furthermore, this invention has a simple structure, is easy to encapsulate, and has good practicality.

Description

Technical Field

[0001] This invention relates to the field of robotic tactile perception technology, and in particular to a tactile perception and flat gripping bionic robotic finger mechanism and tactile recognition method. Background Technology

[0002] Bionic robotic arms are increasingly being used in industrial grasping, service robots, medical assistance, and agricultural harvesting. In actual grasping operations, robotic arms not only need to have reliable gripping capabilities, but also need to be able to sense the contact state, force position and magnitude in real time, thereby improving grasping stability and precision operation capabilities, and preventing objects from slipping or being damaged due to improper gripping force.

[0003] Currently, most common robotic fingers employ purely rigid structures (such as metal or hard plastic fingers), lacking tactile sensing capabilities on their surfaces. This makes it difficult to provide effective feedback on contact states, resulting in gripping control relying heavily on position or current detection, and failing to accurately perceive the force distribution at the contact point. Furthermore, some research has attempted to integrate thin-film pressure sensors onto the finger surface, but issues such as sensor detachment, complex wiring, and packaging difficulties exist, impacting the reliability of practical applications.

[0004] On the other hand, in the grasping process of flat or thin objects (such as paper, cards, films, flexible circuit boards, etc.), existing mechanical fingers, due to their mostly blunt cylindrical or flat ends, lack a rigid nail structure similar to the distal phalanx of a human finger as a stress fulcrum. This makes it difficult to apply effective initial agitation or stopping force to the edge of the object, causing the object to easily slip off the fingertip, resulting in a low grasping success rate. Although alternative solutions such as suction cups, electrostatic adsorption, or large-area flexible grippers exist, these solutions often require additional pneumatic or electrical equipment, have complex structures, and have high requirements for the flatness of the object surface.

[0005] Therefore, there is an urgent need to design a bionic robotic finger mechanism that is simple in structure, easy to encapsulate, and has both tactile sensing function and stable gripping ability for flat objects, in order to solve the problems of lack of tactile feedback and unstable gripping of thin objects in the existing technology. Summary of the Invention

[0006] This invention proposes a tactile sensing and flat gripping bionic robotic finger mechanism and tactile recognition method, aiming to solve the problems of poor object grasping stability and difficulty in effectively gripping small or flat objects caused by the lack of tactile sensing in traditional rigid robotic finger technology.

[0007] In a first aspect, the present invention provides a tactile sensing and flat clamping bionic robotic finger mechanism, wherein the fingertip unit of the bionic robotic finger mechanism wraps around and fixes the phalanx unit, the phalanx unit is provided with a pressure resistance sensing unit, a nail bed structure is formed in the area corresponding to the pressure resistance sensing unit, and a nail unit is provided on the bionic nail bed structure, and the nail unit is a thin sheet structure. The piezoresistive sensing unit consists of multiple conductive silicone sheets arranged in a 4×2 array, with gaps between adjacent conductive silicone sheets.

[0008] Furthermore, the finger bone unit is a hollow cavity with a semi-cylindrical structure, featuring two through holes on the planar side and a closed structure on the arc-shaped side.

[0009] Furthermore, the signal line of the piezoresistive sensing unit passes through the through hole into the hollow cavity of the finger bone unit and is connected to the external acquisition device.

[0010] Furthermore, the finger bone unit and nail unit are rigid structures, both made of PLA material through 3D printing.

[0011] Furthermore, the fingertip unit is formed by filling with flexible, molded silicone.

[0012] Furthermore, the overall dimensions of the piezoresistive sensing unit are 4mm × 9mm × 0.5mm; the dimensions of the conductive silicone sheet are 1.8mm × 2mm × 0.5mm.

[0013] Secondly, the present invention provides a tactile recognition method for a tactile sensing and flat clamping bionic robotic finger mechanism, which is implemented using the above-mentioned structure. When the conductive silicone sheet array is subjected to force, the tactile information of the center position of the force, as well as the offset angle and offset amount, can be obtained by collecting the resistance value of the array unit. The specific steps are as follows: Step S1: Collect the resistance changes of all conductive silicone pad units in the array; After the conductive silicone sheet undergoes deformation, the resistance value RS of different conductive silicone sheet units is: in, i This indicates the number of conductive silicone pads in the array. This represents the fixed resistor in different channel voltage divider circuits. These are the output sampling voltages of different conductive silicone pads. Vcc It is the excitation voltage output by the controller; Furthermore, the resistance change of different silicone sheet units can be obtained. : in, This represents the reference resistance of different units before deformation; Step S2: Calculate the coordinates of the position of the resultant force in the contact area by collecting the resistance value changes and the spatial coordinates of each silicone sheet; Establish a coordinate axis with the center point of the piezoresistive sensing unit as the center, and then measure the change in resistance of each unit. The center point of the force application can be determined: , Where, and represent the spatial coordinates of the center point of the external force acting on the tactile array, respectively; and and These represent the spatial coordinates of different conductive silicone sheet units in the array; Step S3: Calculate the tactile information of the offset direction angle and offset amount based on the offset relationship between the position of the resultant force and the geometric center of the array; The offset angle of the center point of the external force relative to the origin is then calculated. θ and offset d : , .

[0014] Thirdly, the present invention provides a bionic clamp, including the above-mentioned tactile sensing and flat clamping bionic robotic finger mechanism, as well as a servo motor, a servo motor bracket, a connecting rod and a servo motor clamp. The servo bracket is a semi-circular rigid support structure on which a servo is mounted, and a boss structure for fixing the servo clamp is provided at the bottom. One end of the connecting rod is connected to the output shaft of the servo motor, and the other end is connected to the servo motor clamp. The servo clamp is mounted on the servo bracket through a limiting structure formed by the engagement of a boss and a groove, and its other end is connected to the bionic robotic finger mechanism.

[0015] Furthermore, the operating angle of the servo motor is 0°-34°.

[0016] Compared with the prior art, the present invention has the following advantages: 1. This invention constructs a three-layer sandwich structure consisting of a finger bone unit, a piezoresistive sensing unit, and a bionic nail unit, thereby enabling the effective transmission of contact force from the nail to the nail bed region. This allows the conductive silicone sheet to produce a stable and repeatable deformation response, improving the reliability and stability of tactile signal acquisition.

[0017] 2. The rigid edge of the bionic nail unit of the present invention can serve as a stress fulcrum, effectively improving the clamping stability of flat or thin objects and preventing slippage.

[0018] 3. The overall structure of the present invention is simple, and it adopts flexible silicone integrated encapsulation, which is easy to manufacture and integrate.

[0019] The bionic robotic finger provided by this invention solves the technical problems of poor object grasping stability and difficulty in effectively gripping small or flat objects caused by the lack of tactile perception in traditional rigid robotic finger technology; thus enabling better gripping of various objects. Attached Figure Description

[0020] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein: Figure 1 This is a front view of the finger of the release machine provided by the present invention; Figure 2 This is a top view of the bionic robotic finger provided by the present invention; Figure 3 This is a cross-sectional view of the bionic robotic finger provided by the present invention; Figure 4 This is an exploded view of the bionic robotic finger provided by the present invention; Figure 5 is a schematic diagram and force analysis diagram of the conductive silicone sheet array provided by the present invention; Figure 6 is a thermogram of array-type resistance changes under different orientations of the bionic finger mechanism provided by the present invention. Figure 7 This is a front view of the bionic clamping device based on a bionic finger mechanism provided by the present invention.

[0021] In the diagram: 1. Finger bone unit; 11. Through hole; 2. Piezoresistive sensing unit; 21. Conductive silicone sheet; 3. Nail unit; 4. Finger pad unit; 41. Bionic nail bed structure; 5. Servo motor; 6. Connecting rod; 7. Servo motor clamp; 8. Servo motor bracket. Detailed Implementation

[0022] The exemplary embodiments disclosed in this application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of this application and to fully convey the scope of this application to those skilled in the art. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0023] Combination Figure 1-4As shown, the present invention provides a bionic robotic finger with tactile sensing function, comprising a phalangeal unit 1, a pressure-sensitive unit 2, a nail unit 3, and a fingertip unit 4; the phalangeal unit 1 is a hollow semi-cylindrical structure, with a planar structure on one side having two 1.5mm through holes 11, and an arc-shaped closed structure on the other side; the pressure-sensitive unit 2 is disposed on the planar structure of the phalangeal unit 1, and the signal line enters the hollow structure through the two through holes 11 on the phalangeal unit 1 and is connected to an external acquisition device; the fingertip unit 4 is used to encapsulate the phalangeal unit 1 and the pressure-sensitive unit 2 to form a bionic nail bed structure 41 at the position corresponding to the pressure-sensitive unit 2; the nail unit 3 is disposed on the outer surface of the bionic nail bed structure 41.

[0024] Thus, this invention provides a bionic robotic finger mechanism with tactile sensing function and the ability to grip flat objects. By constructing a three-layer sandwich structure consisting of a finger bone unit 1, a piezoresistive sensing unit 2, and a nail unit 3, the contact force is effectively transmitted from the nail to the nail bed area, causing the conductive silicone sheet 21 to generate a deformation response during the force application process. This results in a stable and repeatable deformation response in the conductive silicone sheet 21 during the force application process, thereby improving the reliability and stability of tactile signal acquisition. At the same time, it is equipped with a bionic nail unit to enhance the ability to grasp flat objects.

[0025] In one specific embodiment, the finger bone unit 1 and the nail unit 3 are rigid structures. Considering factors such as low cost, good shaping ability and high molding accuracy, the structures are all made of PLA material by 3D printing.

[0026] In one specific embodiment, the piezoresistive sensing unit 2 is composed of multiple conductive silicone sheets 21 arranged in a 4×2 array, and is encapsulated and fixed between the phalanx unit 1 and the nail bed structure 41 by silicone. In order to cover the entire nail bed structure 41 and realize tactile sensation of the nail bed, the overall size of the piezoresistive sensing unit 2 is set to 4mm×9mm×0.5mm, so as to ensure that the piezoresistive sensing unit 2 can realize comprehensive tactile information during the force application process of the nail bed structure 41. In order to meet the 4×2 array arrangement and ensure that there is a gap between adjacent conductive silicone sheets 21 to avoid signal interference between conductive silicone sheets 21, the size of the conductive silicone sheets 21 is set to 1.8mm×2mm×0.5mm.

[0027] In one specific embodiment, the silicone sheet is installed inside the finger as shown in Figure 5(a). The conductive silicone sheet array 21 uses an analog multiplexer CD4051 as a selector for the conductive silicone sheet 21 units to poll and collect the output voltage of the conductive silicone sheet 21 units in the array. Referring to Figure 5(b), after the conductive silicone sheet 21 deforms, the resistance value RS of different conductive silicone sheet 21 units is: Where i represents the number of conductive silicone sheets 21 in the array. This represents the fixed resistor in different channel voltage divider circuits. Vcc represents the output sampling voltage of different conductive silicone pads 21, and Vcc is the excitation voltage output by the controller. Furthermore, the resistance change of different conductive silicone pad units 21 can be obtained. : in, The reference resistance before deformation of different units is shown in Figure 5(c). Referring to Figure 5(c), a coordinate axis is further established with the center point of the piezoresistive sensing unit 2 as the center. The coordinates of the eight conductive silicone sheets 21 in the array are shown in Figure 5(c). Then, the center point of the force application position can be obtained by observing the changes in the resistance of each unit. , Where, and represent the spatial coordinates of the center point of the external force acting on the tactile array, respectively; and and These represent the spatial coordinates of the 21 units of different conductive silicone sheets in the array. Furthermore, the offset angle θ and offset amount of the center point of the external force relative to the origin are calculated using these coordinates. d : In one specific embodiment, the fingertip unit 4 is formed by filling with flexible molded silicone, and the whole is a flexible adhesive structure.

[0028] In one specific embodiment, the nail unit 3 is used to uniformly transmit the pressure generated by the contact of an external object to the piezoresistive sensing unit 2 fixed on the finger bone unit 1, thereby causing the conductive silicone sheet 21 to undergo directional deformation and synchronously generate a corresponding resistance change signal based on the piezoresistive effect; the resistance change signal is transmitted to an external acquisition device via a signal line passing through the through hole 11. By acquiring the resistance value change of each conductive silicone sheet 21 and combining it with the spatial position coordinates of each unit, the position, offset angle and offset of the resultant force in the contact area can be calculated, thereby realizing the tactile information recognition of the magnitude and direction of the contact force.

[0029] The above tactile information can be used to determine the grasping state: when the offset... d When the offset angle θ is less than the set threshold and close to 0°, it is considered a stable clamping condition; when the offset angle θ points in the direction of the fingertip (positive angle) and the offset amount is less than the set threshold, it is considered a stable clamping condition. d As the force gradually increases, it is determined that the object is prone to slipping. At this point, the clamping force of servo motor 5 can be increased or the attitude of the robotic arm can be adjusted. When the offset angle θ points to the left or right (left rotation / right rotation) and the offset amount...d When the threshold is exceeded, it is determined that the object has twisted. At this time, the gripping point can be replanned or the object can be released and re-gripped. Through the above tactile feedback control strategy, adaptive and stable gripping of flat objects can be achieved, avoiding slippage or damage. Example

[0030] To verify the tactile response characteristics of the bionic robotic finger mechanism when gripping objects of different sizes, a tactile response analysis experiment was designed: Considering that the bionic finger experiences varying external forces when grasping different objects or in different grasping states using its fingernail, a high-precision HP-50 digital push-pull force gauge (0.01N resolution) was used to simulate this phenomenon. The fixed bionic finger was pressed in several directions: forward, 30° forward angle, 60° forward angle, 45° leftward rotation, and 45° rightward rotation. During the experiment, after the force gauge probe contacted the target area on the fingernail surface, a quasi-dynamic cyclic loading test was conducted by slowly and uniformly rotating the frame rocker arm. The external force was increased uniformly from 0 to a preset upper limit Fmax, held for a fixed time Thold after reaching the upper limit, and then unloaded uniformly to 0 at the same rate, completing one full loading cycle. Each loading condition was repeated at least 20 times, and the data obtained under the same conditions were aligned and statistically analyzed to improve the reliability and reproducibility of the experimental results.

[0031] The experimental results are shown in Figure 6. The thermal maps for the forward, 30° forward, 60° forward, 45° leftward, and 45° rightward directions correspond to Figures 6(a), 6(b), 6(c), 6(d), and 6(e), respectively. It can be observed that the thermal maps of the eight conductive silicone pads 21 channels in the piezoresistive sensing unit 2 are different when subjected to external forces under different conditions. Therefore, it can be concluded that the piezoresistive sensing unit 2 can effectively characterize the contact area and force distribution characteristics through the resistance change of the array-type point silicon, thereby providing reliable tactile information support for the identification and stable clamping of objects of different sizes.

[0032] refer to Figure 7 The present invention also provides a bionic clamping device based on a bionic robotic finger, comprising: a servo motor 5, a servo motor bracket 8, a connecting rod 6, and a servo motor clamp 7; the servo motor 5 has a working angle of 0°-34° and is fixedly mounted on the servo motor bracket 8; the servo motor bracket 8 is a semi-circular rigid support structure with mounting holes for mounting the servo motor 5 and a boss structure for fixing the servo motor clamp 7 at the bottom; one end of the connecting rod 6 is connected to the output shaft of the servo motor 5 by a collar, and the other end is connected to the servo motor clamp 7; the limiting structure formed by the boss and the groove of the servo motor clamp 7 is mounted on the servo motor bracket 8, and the other end is connected to the bionic robotic finger mechanism by an adhesive bonding method.

[0033] In this embodiment, the servo motor 5 is model MG996R, with an operating angle range of 0°-34°. The servo motor 5 drives the connecting rod 6 to rotate via its output shaft. The connecting rod 6 simultaneously drives the servo motor clamp 7 to work in conjunction with the bionic robotic finger mechanism, thereby driving the overall rigid finger structure to complete directional clamping, grasping, and releasing actions.

[0034] The bionic robotic finger mechanism or bionic gripper of the present invention can be installed at the end of a multi-degree-of-freedom robotic arm. The robotic arm adjusts the spatial posture of the finger (such as pitch angle and yaw angle) in real time based on tactile information (offset angle θ, offset amount d), and together with the gripping force adjustment of the servo motor 5, it achieves adaptive and stable grasping of flat objects.

[0035] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A tactile sensing and flat clamping bionic robotic finger mechanism, characterized in that, The fingertip unit (4) of the bionic robotic finger mechanism wraps around and fixes the finger bone unit (1). A pressure resistance sensing unit (2) is provided on the finger bone unit (1). A nail bed structure (41) is formed in the area corresponding to the pressure resistance sensing unit (2). A nail unit (3) is provided on the bionic nail bed structure (41), and the nail unit (3) is a thin sheet structure. The piezoresistive sensing unit (2) is composed of multiple conductive silicone sheets (21) arranged in a 4×2 array, and there is a gap between adjacent conductive silicone sheets (21).

2. The tactile sensing and flat gripper bionic robotic finger mechanism according to claim 1, wherein, The finger bone unit (1) is a hollow cavity and a semi-cylindrical structure. Two through holes (11) are opened on the planar structure side, and the arc structure side is a closed structure.

3. The tactile sensing and flat gripper bionic robotic finger mechanism according to claim 1, wherein, The signal line of the piezoresistive sensing unit (2) passes through the through hole (11) into the hollow cavity of the finger bone unit (1) and is connected to the external acquisition device.

4. The tactile sensing and flat gripper bionic robotic finger mechanism according to claim 1, wherein, The finger bone unit (1) and nail unit (3) are rigid structures, both made of PLA material by 3D printing.

5. The tactile sensing and flat gripper bionic robotic finger mechanism according to claim 1, wherein, The fingertip unit (4) is formed by filling with flexible, molded silicone.

6. The tactile sensing and flat gripper bionic robotic finger mechanism according to claim 1, wherein, The overall size of the piezoresistive sensing unit (2) is 4mm×9mm×0.5mm; the size of the conductive silicone sheet (21) is 1.8mm×2mm×0.5mm.

7. A method of tactile discrimination for a tactile sensing and flat clamping bionic robotic finger mechanism according to any one of claims 1-6, characterized in that, When the conductive silicone sheet (21) array is subjected to force, the tactile information of the center position of the force, the offset angle, and the offset amount can be obtained by collecting the resistance value of the array unit. The specific steps are as follows: Step S1: Collect the resistance changes of all conductive silicone sheet (21) units in the array; After the conductive silicone sheet (21) undergoes deformation, the resistance value RS of different conductive silicone sheet (21) units is: wherein, i represents the number of conductive silicone pieces (21) in the array, represents the fixed resistance in the different channel division voltage circuit, is the output sampling voltage of different conductive silicone pieces (21), Vcc is the excitation voltage output by the controller; Furthermore, the resistance change of different silicone sheet units (21) can be obtained. : in, This represents the reference resistance of different units before deformation; Step S2: Calculate the coordinates of the position of the resultant force in the contact area by collecting the resistance value changes and the spatial coordinates of each silicone sheet; Establish a coordinate axis with the center point of the piezoresistive sensing unit (2) as the center, and then measure the change in resistance of each unit. The center point of the force application can be determined: ， Where, and represent the spatial coordinates of the center point of the external force acting on the tactile array, respectively; and and These represent the spatial coordinates of different conductive silicone sheets (21) in the array; Step S3: Calculate the tactile information of the offset direction angle and offset amount based on the offset relationship between the position of the resultant force and the geometric center of the array; The offset angle of the center point of the external force relative to the origin is then calculated. θ and offset d : , 。 8. A bionic clip, characterized in that, Includes the tactile sensing and flat clamping bionic robotic finger mechanism as described in claim 1, as well as a servo motor (5), a servo motor bracket (8), a connecting rod (6), and a servo motor clamp (7). The servo bracket (8) is a semi-circular rigid support structure, on which a servo (5) is mounted, and at the bottom is a boss structure for fixing the servo clamp (7). One end of the connecting rod (6) is connected to the output shaft of the servo motor (5), and the other end is connected to the servo motor clamp (7); The servo clamp (7) is mounted on the servo bracket (8) through a limiting structure formed by the engagement of the boss and the groove, and its other end is connected to the bionic robotic finger mechanism.

9. The bionic clip according to claim 8, characterized in that, The working angle of the servo motor (5) is 0°-34°.

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