Tactile fingertip with fingerprint microstructure and tactile information perception method

Abstract

According to the touch fingertip with the fingerprint microstructure and the touch information sensing method, the overall structure simulates the appearance, the structure and the functional characteristics of the fingertip of a human finger, a mixed structure of a flexible skin layer, a touch sensing layer and a rigid phalanx is adopted, and four groups of sensitive elements are embedded in the flexible skin; each group comprises two sensitive elements for sensing a dynamic signal and a static signal, and the sensitive elements are positioned at different skin layer depths. And the convex fingerprint microstructure is designed on the surface of the finger pulp, so that the tactile perception capability can be further enhanced. According to different contact areas, the touch fingertip can be used for realizing surface attribute identification, and the finger pulp is used for realizing sensing of clamping and contact states. The force feedback control device is simple in structure, simple in process and low in cost, can achieve multiple functions such as contact state sensing, object surface recognition and shape distinguishing, and helps a robot to achieve accurate force feedback control. Furthermore, the device can be mounted on various mechanical clamping jaws to endow the mechanical clamping jaws with the tactile perception capability.

Description

Technical Field

[0001] The present invention relates to the field of tactile perception technology, and in particular to a tactile fingertip with a fingerprint microstructure and a tactile information perception method. Background Art

[0002] With the development of robotics technology, the demand for robots in many fields such as industrial production, commercial services, scientific research and home care has grown rapidly. As its core component, the robot's end effector is crucial to the completion of the robot's automation tasks. However, due to the limitations of the end effector, current robots can often only complete single, repetitive tasks with low uncertainty, and it is difficult to achieve flexible and universal operations. End effectors such as manipulators (mostly two-finger, three-finger, five-finger, etc.) can greatly broaden the scope of the robot's tasks and enhance its flexibility and operating space.

[0003] However, the current manipulators are mostly used for gripping rigid objects in object handling machines. The material itself is rigid and does not have tactile perception function, making it difficult to achieve intelligent control. Although the surface application of electronic skin can help it obtain tactile perception function, it has defects such as high cost, easy wear, and poor reliability, making it difficult to apply on a large scale. Therefore, this patent proposes a tactile fingertip with a fingerprint microstructure, which fully simulates the structure and function of the human hand, wraps the tactile sensitive element inside the flexible skin, and uses rigid finger bones in the middle. While having a large operating force, it can also be used for the operation of objects with different rigidity and complex shapes. In view of the grasping function that is more commonly used in manipulators, the layout of the tactile sensitive element is specifically designed; at the same time, in order to enhance the tactile perception function, a fingerprint protrusion microstructure is designed; based on the above structure, the tactile fingertip can be combined with the robot algorithm to realize the perception of the surface properties and motion state of the object. The end of the fingertip also has a clamping mechanism, which can be directly installed on the end of various mechanical grippers and manipulators, and has a wide range of adaptability and versatility. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a tactile fingertip with a fingerprint microstructure and a tactile information perception method. The present invention has a simple structure, a simple manufacturing process, and a low price and cost. It can realize multiple functions such as contact state perception, object surface recognition, and shape distinction during the grasping process to help the robot 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.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A tactile fingertip with a fingerprint microstructure, characterized in that it includes an outermost flexible material layer, a rigid phalanx embedded in the center of the flexible material, four groups of tactile sensitive units embedded between the flexible material layer and the rigid phalanx, of which three groups are respectively distributed on one side of the fingertip under the fingerprint area and on both sides of the finger; the other group is separately distributed on one side of the fingertip near the top of the fingertip, the surface of the flexible material layer is designed with a raised fingerprint microstructure, and three groups of tactile sensitive units are distributed near the phalanx area under the fingerprint lines of the fingerprint microstructure.

[0006] Furthermore, the fingerprint patterns of the fingerprint microstructure are equally spaced concentric ellipses or other similar patterns with a protrusion height of 0.5 mm and an interval of 1 mm. The above fingerprint microstructure can increase the surface friction of the flexible material, enhance the perception ability of the tactile fingertips to the microstructure of the object surface, and is an enriched area of ​​tactile fingertip perception ability.

[0007] Furthermore, the tactile fingertip with the fingerprint microstructure is assembled on a mechanical gripper or a manipulator or other end effector without a tactile function through a clamping mechanism, and the tactile fingertip with the fingerprint microstructure can be assembled on a mechanical gripper without a tactile function through a clamping mechanism, giving it tactile perception ability, and has wider adaptability and versatility.

[0008] Furthermore, the tactile sensitive units are divided into four groups, each group of tactile sensitive units consists 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 close to the rigid phalanges, 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 have no contact with the rigid phalanges, and the wires of all tactile sensitive units are routed close to the rigid phalanges and pass through the fingers from the fingertips.

[0009] The design of the tactile sensitive unit is based on the type of tactile receptors inside human fingers. There are two types of mechanical receptors under the human skin, namely 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 human fingers, the tactile sensitive units of the tactile fingertips mentioned above are also of two types:.

[0010] The signal lines of all touch-sensitive units are closely connected to the rigid finger bones and pass through the finger from the end of the fingertip. Among the four groups of touch-sensitive units mentioned above, three are respectively distributed on the side of the fingertip under the fingerprint area and on both sides of the finger to detect grasping and sliding signals; the other group is separately distributed on the side of the fingertip near the top of the fingertip to realize the contact sensing function at the top of the fingertip.

[0011] 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).

[0012] 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.

[0013] The present invention provides a tactile information perception method of a tactile fingertip with a fingerprint microstructure, characterized in that: when perceiving the surface properties of an object, the tactile fingertip is used to contact the object, and a group of sensitive elements close to the fingertip is mainly used, and the other three groups of sensitive elements are used as auxiliary for identification; when perceiving the motion state or clamping state of the clamped object, the three groups of sensitive elements under the fingerprint area are mainly used, and the sensitive elements at the fingertip are used as auxiliary for perception. After the above tactile signal is feature extracted, it can be input into a neural network or a machine learning model for the perception of tactile information.

[0014] 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 fingertip of a human finger, and adopts a hybrid structure of a flexible skin layer-tactile perception layer-rigid phalanx. 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 is located at different positions. The surface of the finger pulp 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 finger pulp to realize the perception of clamping and contact status. The present invention has a simple structure, simple process, and low cost. It can realize multiple functions such as contact state perception, object surface recognition, shape distinction, etc., and 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

[0015] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0016] Figure 2 Schematic diagram of the cross-sectional structure of an embodiment of the present invention, (a) radial cross-sectional view, (b) axial cross-sectional view.

[0017] 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 clamp. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: 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 a plurality of tactile sensitive units 3 and 4 embedded between the flexible material layer and the rigid finger bone.

[0019] like Figure 1 As shown, the end of the fingertip is provided with a clamping mechanism 7, which can be directly installed on the end of a variety of mechanical grippers 8, giving it tactile perception capabilities, and having strong adaptability and versatility.

[0020] 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, all embedded in the flexible material, and not in contact with 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, and is more conducive to the static tactile sensitive unit to collect static pressure signals; the dynamic tactile sensitive unit that is fully embedded in the flexible material layer has no rigid material for support, and 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 to collect vibration signals.

[0021] 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, which corresponds to the outermost flexible material layer 1 of the present invention; fingerprints are distributed on the outside of human fingers, which corresponds to the fingerprint microstructure raised on the surface of the finger pulp in the present invention; the innermost layer of human fingers is supported by phalanges, which corresponds to the innermost rigid phalanges 2 of the present invention; there are two kinds of mechanical receptors distributed in the skin of human fingers, namely, slow adapting receptors sensitive to static pressure, and fast adapting receptors more sensitive to dynamic pressure and fluctuation, which correspond 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; the fingerprint part in the structure of human fingers corresponds to structure 5; the receptors of human fingers are connected to the nerve fibers used to conduct nerve signals, which corresponds to the wires 6 used to transmit electrical signals in the present invention.

[0022] 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 phalanx includes but is not limited to acrylic rods, etc.

[0023] Preferably, the fingerprint patterns on the surface of the fingertip skin include but are not limited to concentric circles, concentric ellipses and the like.

[0024] like Figure 2 As shown in Figures 2(a) and 2(b), the present invention has three groups of tactile sensing units respectively distributed on one side of the finger pulp under the fingerprint area and on the left and right sides of the fingertip, and each group of tactile sensing units is composed of a static tactile sensitive unit 3 and a dynamic tactile sensitive unit 4. The above design can maximize the reception of tactile signals sensed from the fingerprint microstructure, and the left-right symmetrical arrangement can eliminate the error caused by the above tactile fingertips touching objects from the left and right directions, thereby enhancing the tactile sensing ability of the present invention.

[0025] 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 the small area 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 the small area and enhancing the perception ability.

[0026] Furthermore, based on the above structure, the tactile fingertips can be combined with the robot algorithm to realize the perception of the surface properties and motion state of the object. By receiving and analyzing the tactile signals generated by the sliding friction of the tactile fingertips on the surface of the object, the host computer can realize the perception of various properties of the object surface, such as roughness, flatness, location and shape of holes, etc.; in addition, when the robot grasps the object, it can judge the motion state of the object by judging the threshold of the tactile signal, such as whether the object is sliding, twisting, etc.

[0027] like Figure 2 As shown in (a), the static tactile sensitive unit 3 is directly pasted on the rigid phalanges 2, while the dynamic tactile sensitive unit 4 is pasted on a thinner flexible material layer 1. Since the manufacturing process of the invention mainly adopts the casting method, the outermost flexible material layer requires subsequent casting steps 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 unit can be fully embedded in the flexible material layer during the subsequent casting process, a thinner flexible material layer must be pasted on the top of the phalanges in advance. The upper surface of the flexible material layer is used to paste the dynamic tactile sensitive unit, and the static tactile sensitive unit can be directly pasted on the rigid phalanges.

[0028] Working principle of the present invention: The present invention adopts a flexible layer-sensing layer-hard layer structure. When the outermost flexible material is squeezed or vibrated, the external mechanical signal acts on the tactile sensing unit inside the finger, where the dynamic tactile sensing unit collects the vibration signal, and the static tactile sensing unit collects the static pressure signal. The signals of the two are connected to the signal acquisition circuit and the signal processing circuit through wires. Based on the above principle, the robot can achieve tactile perception through the present invention.

[0029] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required 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 finger pulp and on both sides of the finger under the fingerprint area; the other group being separately distributed on one side of the finger pulp near the top of the fingertip, the surface of the flexible material layer (1) being designed with a raised fingerprint microstructure (5), three groups of touch sensitive units being distributed near the phalange area under the fingerprint lines of the fingerprint microstructure (5).

2. The tactile fingertip with fingerprint microstructure according to claim 1, characterized in that: The fingerprint pattern of the fingerprint microstructure (5) is a series of equally spaced concentric ellipses with a protrusion height of 0.5 mm and a spacing of 1 mm.

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

4. The tactile fingertip with fingerprint microstructure according to claim 1, characterized in that: 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 routed in close contact with the rigid phalanges (2) and pass through the finger from the end of the fingertip.

5. The tactile fingertip with 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).

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

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