Tactile fingertip with fingerprint microstructure and tactile information sensing method

Abstract

The application designs a tactile fingertip with fingerprint microstructure and a tactile information sensing method, the overall structure simulates the shape, structure and functional characteristics of the fingertip of human fingers, adopts a hybrid structure of flexible skin layer-tactile sensing layer-rigid phalanx, and four groups of sensitive elements are embedded in the flexible skin, each group contains two sensitive elements for sensing dynamic signals and static signals, and is located at different skin layer depths. The surface of the finger pulp is designed with raised fingerprint microstructure, which can further enhance the tactile sensing ability. According to the different contact areas, the fingertip can realize surface attribute recognition, and the finger pulp can realize clamping and contact state sensing. The structure of the application is simple, the process is simple, and the cost is low, and various functions such as contact state sensing, object surface recognition and shape distinction can be realized, which helps the robot to realize accurate force feedback control. Further, the application can be installed on various mechanical clamps to give them tactile sensing ability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tactile perception, in particular to a tactile fingertip with fingerprint microstructure and a tactile information perception method. BACKGROUND

[0002] With the development of robot technology, the demand for robots in industrial production, commercial services, scientific research and home care is growing rapidly. As the core component of the robot, the end effector of the robot is essential to the completion of the robot automation task. However, due to the limitation of the end effector, the current robot can only complete single, repetitive and low-uncertainty tasks, and it is difficult to achieve flexibility and versatility. The end effector such as the mechanical hand (mostly two fingers, three fingers, five fingers, etc.) can greatly expand the range of robot task execution and enhance its flexibility and operation space.

[0003] However, the current mechanical hand is mostly used for gripping rigid objects, and the material itself is rigid and does not have tactile perception function, making it difficult to achieve intelligent control. Although the surface can be pasted with electronic skin to help it obtain tactile perception function, it has defects such as high cost, easy wear and poor reliability, and is difficult to be applied on a large scale. Therefore, the present application proposes a tactile fingertip with fingerprint microstructure, which fully simulates the structure and function of the human hand, wraps the tactile sensitive element inside the flexible skin, and uses a rigid phalanx in the middle. It can be used for operation of objects with different stiffness and complex shape while having a large operating force. For the gripping function commonly used by the mechanical hand, the layout of the tactile sensitive element is specifically designed; at the same time, in order to enhance the tactile perception function, a fingerprint convex microstructure is designed; based on the above structure, the tactile fingertip can realize the perception of the surface properties and motion state of the object in combination with the robot algorithm. The fingertip end also has a clamping mechanism and can be directly installed at the end of various mechanical clamps and mechanical hands, and has wide adaptability and versatility. SUMMARY

[0004] To solve the above technical problems, the present application proposes a tactile fingertip with fingerprint microstructure and a tactile information perception method. The structure of the present application is simple, the manufacturing process is simple, the price cost is low, and the contact state perception, object surface identification, shape distinction and other functions in the grabbing process can be realized to help the robot realize precise force feedback control. Further, the present application can be easily installed on various mechanical clamps to give them tactile perception ability.

[0005] To achieve the above purpose, the technical solution adopted by the present application is:

[0006] A tactile fingertip with fingerprint microstructure, characterized in that it comprises a flexible material layer as the outermost layer, a rigid phalanx embedded in the center of the flexible material, and four groups of tactile sensitive units embedded between the flexible material layer and the rigid phalanx. Three of the four groups of tactile sensitive units are respectively distributed on one side of the palm under the fingerprint area and on both sides of the finger; the other group is separately distributed on one side of the palm near the top of the fingertip. The surface of the flexible material layer is designed with raised fingerprint microstructure, and the fingerprint microstructure has three groups of tactile sensitive units distributed near the phalanx area under the fingerprint lines.

[0007] Further, the fingerprint microstructure has a raised height of 0.5mm and an interval of 1mm, and the fingerprint lines are equidistant concentric ellipses or other similar lines. The fingerprint microstructure can increase the surface friction of the flexible material and enhance the perception ability of the tactile fingertip to the microstructure of the object surface, which is the enrichment area of the perception ability of the tactile fingertip.

[0008] Further, the tactile fingertip with fingerprint microstructure is assembled on a mechanical gripper or a mechanical hand or other end effector without tactile function through a clamping mechanism. The tactile fingertip with fingerprint microstructure is assembled on a mechanical gripper without tactile function through a clamping mechanism. The tactile fingertip with fingerprint microstructure can be assembled on a mechanical gripper without tactile function through a clamping mechanism, which gives it tactile perception ability and has wider adaptability and universality.

[0009] Further, the tactile sensitive units are divided into four groups, each group consisting of a static tactile sensitive unit that can respond to static force signals and a dynamic tactile sensitive unit that can respond to dynamic force signals. One side of the static tactile sensitive unit is in close contact with the rigid phalanx, and the other side is embedded in the flexible material layer. The dynamic tactile sensitive units are all embedded in the flexible material layer and do not come into contact with the rigid phalanx. The wires of all tactile sensitive units are in close contact with the rigid phalanx and run out of the finger from the tip of the fingertip.

[0010] The design of the tactile sensitive units is based on the types of tactile receptors in the human finger. There are two types of mechanical receptors in human skin, slow adapting receptors that are sensitive to static pressure, and fast adapting receptors that are more sensitive to dynamic pressure and fluctuations. Analogous to the receptors of the human finger, the tactile sensitive units of the above-mentioned tactile fingertip are also of two types.

[0011] The signal lines of all tactile sensitive units are in close contact with the rigid phalanx and run out of the finger from the tip of the fingertip. Three of the four groups of tactile sensitive units are respectively distributed on one side of the palm under the fingerprint area and on both sides of the finger, for detecting grasping and sliding signals; the other group is separately distributed on one side of the palm near the top of the fingertip, for realizing the contact perception function of the top of the fingertip.

[0012] Furthermore, the static tactile sensitive unit is made of a resistance strain gauge or other piezoresistive materials; and the dynamic tactile sensitive unit is made of a piezoelectric material such as polyvinylidene fluoride (PVDF).

[0013] The static tactile sensitive unit 3 is made of a high-precision resistance strain gauge (SG) and is used to detect static force signals; the dynamic tactile sensitive unit 4 is made of polyvinylidene fluoride (PVDF) and is used to detect dynamic force signals.

[0014] The present invention provides a method for perceiving tactile information using a tactile fingertip with a fingerprint microstructure. The method is characterized by: When perceiving the surface properties of an object, the tactile fingertip contacts the object, using a group of sensitive elements near the fingertip as the primary sensor, supplemented by three other groups of sensitive elements. When perceiving the motion or gripping state of a clamped object, the three groups of sensitive elements within the fingerprint region are primary sensors, supplemented by the sensitive elements at the fingertip. After feature extraction, these tactile signals can be input into a neural network or machine learning model for tactile information perception.

[0015] The present invention designs a tactile fingertip with a fingerprint microstructure and a tactile information perception method. The overall structure imitates the appearance, structure and functional characteristics of the human fingertip, and adopts a hybrid structure of flexible skin layer-tactile perception layer-rigid finger bone. There are four groups of sensitive elements embedded in the flexible skin, each group contains a sensitive element for sensing dynamic signals and static signals, and are located in different positions. The surface of the fingertip is designed with a raised fingerprint microstructure, which can further enhance the tactile perception ability. The tactile fingertip can use the fingertip to realize surface attribute recognition according to the different contact areas, and use the fingertip to realize the perception of clamping and contact status. The present invention has a simple structure, simple process and low cost, and can realize multiple functions such as contact status perception, object surface recognition, shape differentiation, etc., to help robots achieve precise force feedback control. Furthermore, the present invention can be easily installed on a variety of mechanical grippers to give them tactile perception capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0017] Figure 2 Schematic diagram of the cross-sectional structure of an embodiment of the present invention, (a) is a radial cross-sectional view, and (b) is an axial cross-sectional view.

[0018] Among them: 1-flexible material layer, 2-rigid finger bone, 3-static tactile sensitive unit, 4-dynamic tactile sensitive unit, 5-fingerprint microstructure, 6-wire, 7-clamping mechanism, 8-mechanical gripper. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0020] like Figure 1 As shown, the structure of the tactile fingertip with fingerprint microstructure adopts a hybrid layout of flexible layer-sensing layer-hard layer, including an outermost flexible material layer 1, a rigid finger bone 2 embedded in the center of the flexible material, and multiple tactile sensitive units 3 and 4 embedded between the flexible material layer and the rigid finger bone.

[0021] like Figure 1 As shown, the end of the fingertip is provided with a clamping mechanism 7, which can be directly mounted on the end of a variety of mechanical grippers 8, giving it tactile perception capabilities, and having strong adaptability and versatility.

[0022] like Figure 2 As shown in (a), there are two types of tactile sensitive units in the perception layer, one is a static tactile sensitive unit 3 that can respond to static force signals, and the other is a dynamic tactile sensitive unit 4 that can respond to dynamic force signals. The static tactile sensitive unit in the present invention is made of SG, and the dynamic tactile sensitive unit is made of PVDF. Among them, one side of the static tactile sensitive unit is embedded in the flexible material layer, and the other side is close to the rigid phalanges; both sides of the dynamic tactile sensitive unit are in contact with the flexible material layer, and are all embedded in the flexible material and do not contact the rigid phalanges. Under the above design, one side of the static tactile sensitive unit is supported by the rigid phalanges. Compared with the flexible material, the rigid phalanges have the advantage of smaller vibration amplitude, which can reduce the influence of the vibration signal of the flexible material layer on the static tactile sensitive unit, which is more conducive to the static tactile sensitive unit collecting static pressure signals; the dynamic tactile sensitive unit, which is completely embedded in the flexible material layer, has no rigid material for support. The vibration signal of the flexible material can directly act on the dynamic tactile sensitive unit, which is more conducive to the dynamic tactile sensitive unit collecting vibration signals.

[0023] like Figure 2As shown in (a), the design of the present invention refers to the physiological structure of human fingers. The outermost layer of human fingers is soft skin, corresponding to the outermost flexible material layer 1 of the present invention; fingerprints are distributed on the outside of human fingers, corresponding to the raised fingerprint microstructure on the surface of the finger pulp in the present invention; the innermost layer of human fingers is supported by phalanges, corresponding to the innermost rigid phalanges 2 of the present invention; the skin of human fingers has two types of mechanical receptors distributed, namely slow-adapting receptors sensitive to static pressure and fast-adapting receptors more sensitive to dynamic pressure and fluctuations, corresponding to the static tactile sensitive units 3 that respond to static force signals and the dynamic tactile sensitive units 4 that respond to dynamic force signals in the present invention respectively; the fingerprint portion of the human finger structure corresponds to structure 5; the receptors of human fingers are connected to the nerve fibers used to conduct nerve signals, corresponding to the wires 6 used to transmit electrical signals in the present invention.

[0024] Preferably, the flexible material for the fingertip skin includes but is not limited to polyurethane, polyester, silicone rubber, etc.; the hard material for the fingertip phalanges includes but is not limited to acrylic rods, etc.

[0025] Preferably, the fingerprint patterns on the surface of the fingertip skin include but are not limited to concentric circles, concentric ellipses and the like.

[0026] like Figure 2 (a) Figure 2 As shown in (b), the present invention has three sets of tactile sensing units, one located on the fingertip below the fingerprint area and the other on the left and right sides of the fingertip. Each set of tactile sensing units consists of a static tactile sensitive unit 3 and a dynamic tactile sensitive unit 4. This design maximizes the reception of tactile signals from the fingerprint microstructure. The bilaterally symmetrical arrangement eliminates errors caused by the tactile fingertip touching an object from both left and right directions, enhancing the present invention's tactile sensing capabilities.

[0027] like Figure 2 As shown in (a), the present invention is designed with a group of tactile sensing units on the side of the fingertip near the top of the fingertip, and the group of tactile sensing units is responsible for sensing the tactile signals at the top of the fingertip. When the manipulator needs to sense tactile signals in a small area, due to the large sensing area of ​​the fingerprint area, the sensitivity to small areas decreases, and it is no longer suitable for application in the above scenario, while the fingertip area with a smaller area is more suitable for sensing the above surface. In actual operation, the tactile fingertip can be made to touch the surface of the object with the side of the fingertip at the top area of ​​the fingertip at a certain inclination angle, thereby improving the tactile sensitivity of the tactile finger to small areas and enhancing the perception ability.

[0028] Furthermore, based on the above structure, the tactile fingertips can be combined with robotic algorithms to perceive the surface properties and motion state of an object. By receiving and analyzing the tactile signals generated by the tactile fingertips sliding and rubbing against the surface of an object, the host computer can perceive various surface properties, such as roughness, flatness, and the location and shape of holes. Furthermore, when the robotic arm grasps an object, it can determine the object's motion state, such as whether it is sliding or twisting, by determining the threshold of the tactile signals.

[0029] like Figure 2 As shown in (a), the static tactile sensitive unit 3 is directly attached to the rigid phalanges 2, while the dynamic tactile sensitive unit 4 is attached to a thinner layer of flexible material 1. Since the manufacturing process of the invention mainly adopts the casting method, the outermost flexible material layer requires a subsequent casting step to be completed, so it is necessary to prepare the rigid phalanges in advance and arrange the corresponding sensors on the phalanges. In order to ensure that the dynamic tactile sensitive units can be fully embedded in the flexible material layer during the subsequent casting process, a thinner layer of flexible material must be attached to the top of the phalanges in advance. The upper surface of the flexible material layer is used to attach the dynamic tactile sensitive units, and the static tactile sensitive units can be directly attached to the rigid phalanges.

[0030] Working principle of the present invention:

[0031] The present invention employs a flexible layer-sensing layer-hard layer structure. When the outermost flexible material is squeezed or vibrated, it transmits external mechanical signals to the tactile sensing units within the finger. The dynamic tactile sensing unit collects the vibration signal, while the static tactile sensing unit collects the static pressure signal. These signals are then connected to a signal acquisition circuit and a signal processing circuit via wires. Based on this principle, the present invention enables robots to achieve tactile perception.

[0032] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A tactile fingertip with a fingerprint microstructure, characterized in that: The invention comprises an outermost flexible material layer (1), a rigid phalange (2) embedded in the center of the flexible material, four groups of touch-sensitive units embedded between the flexible material layer (1) and the rigid phalange (2), three of the four groups of touch-sensitive units being respectively distributed on one side of the fingertip below the fingerprint area and on both sides of the finger; another group being separately distributed on one side of the fingertip near the top of the fingertip, a raised fingerprint microstructure (5) being designed on the surface of the flexible material layer (1), and three groups of touch-sensitive units being distributed near the phalange area below the fingerprint lines of the fingerprint microstructure (5); The tactile sensitive units are divided into four groups, each group of tactile sensitive units is composed of a static tactile sensitive unit (3) that can respond to a static force signal and a dynamic tactile sensitive unit (4) that can respond to a dynamic force signal. One side of the static tactile sensitive unit (3) is in close contact with the rigid phalanges (2), and the other side is embedded in the flexible material layer (1); the dynamic tactile sensitive units (4) are all embedded in the flexible material layer (1) and do not contact the rigid phalanges (2). The wires (6) of all the tactile sensitive units are closely connected to the rigid phalanges (2) and pass through the finger from the end of the fingertip.

2. The tactile fingertip with a fingerprint microstructure according to claim 1, characterized in that: The fingerprint pattern of the fingerprint microstructure (5) is a concentric ellipse with equal spacing and a convex height of 0.5 mm and a spacing of 1 mm.

3. The tactile fingertip with a fingerprint microstructure according to claim 1, characterized in that: The tactile fingertip with the fingerprint microstructure is assembled on a mechanical gripper or a manipulator without a tactile function through a clamping mechanism (7).

4. The tactile fingertip with a fingerprint microstructure according to claim 1, characterized in that: The static tactile sensitive unit (3) is made of a resistance strain gauge; and the dynamic tactile sensitive unit (4) is made of polyvinylidene fluoride (PVDF).

5. The method for perceiving tactile information using a tactile fingertip with a fingerprint microstructure according to any one of claims 1 to 4, characterized in that: When perceiving the surface properties of an object, the tactile fingertips are used to touch the object, and the group of tactile sensitive units close to the fingertips are mainly used for identification, and the other three groups of tactile sensitive units are used as auxiliary. When perceiving the motion state or clamping state of the clamped object, the three groups of tactile sensitive units under the fingerprint area are mainly used, and the tactile sensitive elements at the fingertips are used as auxiliary for perception. After the above tactile information is extracted, it is input into the neural network or machine learning model for perception of tactile information.

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