Human fingertip-simulated touch sensor

Abstract

The invention discloses a humanoid fingertip tactile sensor, which comprises a humanoid phalanx, a touch sensor and a control module, the bottom permanent magnet is arranged on the anthropomorphic phalanx; the flexible circuit board covers the bottom permanent magnet; the separation fixing layer is arranged on the flexible circuit board and is provided with a mounting hole; the piezoresistive film and the top permanent magnet are mounted in the mounting hole of the separation fixing layer; and the silica gel contact layer is sleeved on the separation fixing layer. The invention aims to solve the technical problems of low sensitivity, low array, serious crosstalk between sensing units, low integration level and the like of a fingertip touch sensor in the existing robot sensing technology. According to the invention, a plurality of sensing units are distributed on the human-simulated fingertip, so that the detection of the magnitude of multi-contact pressure and the action position can be realized. The human fingertip simulating sensor can be installed at the tail end of the mechanical arm, and necessary tactile information is provided for achieving flexible operation.

Description

Technical Field

[0001] The present invention relates to the technical field of robot sensing, and particularly to a humanoid fingertip tactile sensor. Background Art

[0002] With the gradual maturity of robot technology, the applications of robots have expanded from repetitive and limited industrial tasks to complex and random human-machine interactions. Therefore, higher requirements are imposed on indicators such as the safety of human-machine interaction, the accuracy of robot operation, and the humanoid degree of interaction actuators. The multi-fingered dexterous hand is the main application carrier for robots to interact with the outside world. At the current research stage, high-degree-of-freedom, flexible, and bionic robotic hands have been developed. However, for a dexterous hand to achieve precise operation and safe human-machine interaction, it not only requires a high degree of flexibility but also the ability to perceive similar to that of a human hand.

[0003] Tactile sensors can provide certain tactile signals to robots. Although there are many solutions for fingertip tactile sensors in recent years, however, they still face many challenges in practical applications. In particular, there are relatively few fingertip tactile sensors that can be actually applied to robotic hands for daily fine operation assistance, and even fewer sensor solutions with commercial potential. Traditional fingertip tactile sensors are large in size, low in humanoid degree, and difficult to integrate; most are single-point type, with low spatial resolution and limited tactile information collection; and the output signals of the sensing units are unstable and vulnerable to interference. Therefore, developing a humanoid fingertip tactile sensor with high sensitivity, multi-point pressure sensing, less crosstalk between sensing units, and high integration is still an urgent challenge. Summary of the Invention

[0004] In order to overcome the technical problems in the existing robot sensing technology, such as low sensitivity of fingertip tactile sensors, low array level, serious crosstalk between their sensing units, and low integration, the present invention provides a humanoid fingertip tactile sensor and its preparation method. Thirty sensing units are distributed on the humanoid fingertip, which can detect the magnitude and action position of multi-contact pressures. The humanoid fingertip sensor can be installed at the end of a robotic hand to provide necessary tactile information for achieving dexterous operation.

[0005] To achieve the above object, the present invention adopts the following technical solutions.

[0006] A humanoid fingertip tactile sensor, comprising:

[0007] A humanoid finger bone;

[0008] A bottom permanent magnet disposed on the humanoid finger bone;

[0009] A flexible circuit board covering the bottom permanent magnet;

[0010] A separation and fixing layer is provided on the flexible circuit board, and the separation and fixing layer is provided with mounting holes;

[0011] A piezoresistive film and a top permanent magnet installed in the mounting holes of the separation and fixing layer;

[0012] A silicone contact layer sleeved on the separation and fixing layer.

[0013] A mounting groove is provided on the anthropomorphic phalanx, and the first permanent magnet is arranged in the mounting groove.

[0014] The number of the mounting grooves and the first permanent magnets is the same, which is 24 - 36, and most preferably 30.

[0015] The flexible circuit board includes a flexible substrate and electrode units provided on the flexible substrate. The number of the electrode units is the same as that of the bottom permanent magnets and their positions correspond to each other.

[0016] The piezoresistive film in the mounting hole of the separation and fixing layer is in close contact with the electrode unit of the flexible circuit board, and the thickness of the piezoresistive film is 0.05 - 0.15 mm.

[0017] The number of the piezoresistive film, the top permanent magnet, and the electrode unit of the flexible circuit board is the same, and their positions correspond to each other.

[0018] Silicone contacts are provided on the silicone contact layer. The number of the silicone contacts is the same as that of the top permanent magnets and their positions correspond to each other.

[0019] The silicone contact layer includes silicone and glass microspheres. The addition amount of the glass microspheres in the silicone contact layer is 3 - 5% of the mass of the silicone, and most preferably 4%.

[0020] The silicone contact includes silicone and glass microspheres. The addition amount of the glass microspheres in the silicone contact is 3 - 5% of the mass of the silicone, and most preferably 4%.

[0021] A humanoid fingertip tactile sensor includes a humanoid finger bone, a permanent magnet, a partition fixing plate, a piezoresistive film, an FPCB, and a silicone contact layer. Part of the permanent magnet is embedded in 30 corresponding slots of the humanoid finger bone; the "head contour shape" of the FPCB is designed to be close to the contour shape of the unfolded plane of the outer surface of the finger bone, and the "tail" is led out by a flexible cable. The FPCB is adhered to the surface of the finger bone with an adhesive; the partition fixing plate is sleeved on the surface of the finger bone with the FPCB adhered, and is fixed at the bottom with an adhesive; the piezoresistive film is sequentially placed on 30 "windowed" interdigital electrodes of the FPCB; the permanent magnet is embedded in the slot of the partition fixing plate, and it attracts the permanent magnet in the slot, making the piezoresistive film fully contact with the electrode, fixing the position of the piezoresistive film, and at the same time providing a certain pre-tightening force; the silicone contact layer is sleeved on the outermost surface and fixed at the bottom with an adhesive to form a humanoid fingertip tactile sensor.

[0022] Further, the piezoresistive film is selected as a velostat conductive film, and its resistance value is inversely proportional to the pressure applied.

[0023] Further, the array electrodes of the FPCB include a common electrode and the remaining electrodes arranged in an array. The common electrode is connected to the GND terminal, and the remaining electrodes are connected to an external test circuit; the FPCB has a planar structure, that is, the two end electrodes of the sensing unit are on the same plane.

[0024] Further, the preparation material of the silicone contact layer is a solution composed of AB silicone and glass microbeads accounting for 4% of the mass of AB silicone.

[0025] Further, both the humanoid finger bone and the partition fixing plate are processed by 3D printing, and the material used is resin LEDO 6060.

[0026] In summary, the present invention has the following beneficial effects:

[0027] (1) The sensor can realize the pressure detection of multiple contacts, and has a simple manufacturing process and low cost;

[0028] (2) The piezoresistive film has a certain pre-pressure by the way of attracting with a magnet, skipping the area where its resistance value jumps too much and the non-linear interval in the initial stage, which is beneficial to improving the stability of the circuit and the sensitivity of detection;

[0029] (3) The silicone contact layer with an appropriate amount of glass microbeads added can improve the elastic modulus of the silicone, enabling the external force to be better transmitted to the sensing unit and improving the sensitivity of the sensor;

[0030] (4) By designing a specific shape of the sensing unit and the partition fixing plate, the units are completely separated from each other, reducing the crosstalk between the units;

[0031] (5) The sensor appearance structure imitating a human fingertip can be better integrated into the manipulator body. Brief Description of the Drawings

[0032] Figure 1 is the assembly drawing of the present invention.

[0033] Figure 2(a) is a schematic diagram of the front array electrode arrangement of the FPCB in the present invention.

[0034] Figure 2(b) is a schematic diagram of the back common terminal trace of the FPCB in the present invention.

[0035] Figure 3(a) is a schematic diagram of the first step of the assembly of the present invention.

[0036] Figure 3(b) is a schematic diagram of the second step of the assembly of the present invention.

[0037] Figure 3(c) is a schematic diagram of the third step of the assembly of the present invention.

[0038] Figure 4 is the assembly drawing of the preparation mold of the silicone contact layer in the present invention.

[0039] Figure 5 is the exploded view of the preparation mold of the silicone contact layer in the present invention.

[0040] Figure 6 is the comparison diagram of the structure with or without pre-tightening force in the present invention.

[0041] Figure 7 is the crosstalk signal display diagram of the fingertip sensing unit in the present invention.

[0042] In the figures:

[0043] Permanent magnet 1, piezoresistive film 2, FPCB 3, magnet 4, humanoid finger bone 5, partition fixing layer 6, silicone contact layer 7, mold A 8, mold B 9, bolt 10, nut 11. Detailed Embodiment

[0044] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described by referring to the drawings below are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0045] Embodiment:

[0046] This embodiment provides a humanoid fingertip tactile sensor, the structure of which is as Figure 1As shown in the figure: The magnet 4 is embedded into 30 holes of the phalanx 5; the flexible printed circuit board 3 is bonded to the surface of the phalanx 5 with an adhesive. The positions of the array electrodes on the FPCB are aligned with the positions of the magnets 4. The back-wiring of the common end of the FPCB electrodes is shown in Fig. 2(b), and the holes are connected to the front electrodes. The distribution of the front array electrodes of the FPCB is shown in Fig. 2(a); the fixed separation layer 6 is sleeved on the phalanx with the assembled FPCB, and the bottom is fixed into one body with an adhesive. The holes on the separation layer 6 are aligned with the positions of the array electrodes on the FPCB; the piezoresistive film 2 cut into unit size is embedded into the holes of the separation layer 6 and placed on the FPCB array electrodes; the magnet 1 is embedded into the holes of the separation layer 6 and attracts to the magnet 4, which plays a role in fixing the piezoresistive film 2 and providing a certain pre-tightening force; the silicone contact layer 7 is sleeved on the outermost layer, and the bottom is fixed into one body with an adhesive.

[0047] The working principle of the humanoid fingertip tactile sensor based on the above structure is as follows: When the silicone contact of the sensor is not under pressure, the piezoresistive film 2 is only under the pre-tightening force generated by the attraction between the magnet 4 and the magnet 1. At this time, the piezoresistive film 2 maintains its initial resistance value. When the sensor contacts an object, the hemispherical contacts of the silicone contact layer 7 deform, and the force received by the contacts is transmitted to the magnet 1. The magnet 1 displaces and transmits the force to the piezoresistive film 2. Due to the piezoresistive effect, the resistance value of the piezoresistive film 2 decreases as the pressure increases. After the sensor separates from the object, due to the unloading of the external force, the silicone contacts and the film reset, and the resistance value of the piezoresistive film 2 returns to the initial value. Therefore, by detecting the resistance value of the piezoresistive film 2, the force received by the sensor can be reflected. At the same time, the sensing units are distributed in a full-coverage manner on the fingertip surface. By quickly and cyclically detecting the resistance values of each unit, the force-receiving position can be accurately and real-timely reflected.

[0048] Since the resistance value cannot be directly read, a voltage-dividing circuit can be built. A voltage-dividing resistor is connected in series with the lead-out end of the array electrode in contact with the piezoresistive film, and the other end of the pin of the voltage-dividing resistor is connected to the positive pole of the power supply. The single-chip microcomputer reads the voltage across the piezoresistive film to indirectly reflect its resistance value.

[0049] At the same time, since the sensor in this design has 30 sensing units, in order to reduce the occupation of the peripherals of the single-chip microcomputer, multiple multiplexers are used to cyclically sample all the sensing units. The output pins of the multiplexer are connected to the ADC channels of the single-chip microcomputer, and the input pins are connected to the array electrode end channels of multiple FPCBs; it has multiple pins, and the output channels can be controlled by the high and low levels input by the pins of the single-chip microcomputer. In addition, the clock frequency of the single-chip microcomputer is extremely high, so it is approximately regarded as sampling all the sensing units simultaneously.

[0050] On the other hand, this embodiment also provides a preparation method for the above sensor, including the following processes:

[0051] (1) The FPCB is attached to the surface of the phalange. Align the electrodes on the FPCB with the phalange hole grooves. After covering the surface of the phalange, fix the FPCB with tape, then separate the FPCB from the phalange surface. On the phalange surface, evenly apply an adhesive, slip on the fixed FPCB, place it in an oven and heat at 50 °C for 2 hours. Finally, take out the phalange and remove the tape. In this way, the FPCB can be attached to the phalange surface.

[0052] (2) Prepare the silicone contact layer. The two-component room-temperature-curing platinum-catalyzed silicone rubber prepared in a 1:1 ratio is mixed and injected into mold A, then cover mold B coated with a release agent, fix the positions of molds A and B with bolts and nuts. Under a negative pressure of 0.1 MPa, evacuate the bubbles in the platinum-catalyzed silicone rubber and maintain for 5 minutes. Then place the mold containing the silicone in an oven and heat at 50 °C for 2 hours. Finally, take out the mold, separate the two molds and perform cooling and demolding. Molds A and B are as Figure 5 shown. When preparing the silicone contact layer, add 4% of the mass of glass microspheres to the silicone mixture, which can increase the elastic modulus of the silicone contact and improve the sensitivity of the sensor.

[0053] (3) Sensor assembly. Embed the permanent magnet 4 into the corresponding 30 slots of the anthropomorphic phalange 5; attach the FPCB to the surface of the phalange with an adhesive; slip the partition fixing plate 6 onto the phalange surface with the attached FPCB and fix it at the bottom with an adhesive; place the piezoresistive film 2 on the 30 "open window" interdigital electrodes of the FPCB in sequence; embed the permanent magnet 1 into the slots of the partition fixing plate; slip the silicone contact layer 7 onto the outermost surface and fix it at the bottom with an adhesive to form an anthropomorphic fingertip tactile sensor. The assembly steps are shown in Figures 3(a), 3(b) and 3(c).

[0054] Test the structure that provides a pre-tightening force by the attraction of magnets to verify the feasibility of this structure to improve the sensor performance. The obtained results are as Figure 6 shown.

[0055] Through Figure 6 it can be seen that, in the structure without the pre-tightening force provided by the attraction of magnets, the amplitude change of the analog quantity is relatively large. This change reflects from the side that the resistance change value and current change value of the piezoresistive film are relatively large, which will affect the stability of the circuit and cause relatively large power loss. While in the structure with the pre-tightening force provided by the attraction of magnets, the range with a relatively large change in the resistance value of the piezoresistive film is skipped, making the amplitude of the analog quantity change less under the same pressure. The stability of the circuit is better and the power loss is smaller, which can extend the service life of the sensor.

[0056] Press the 4 sensing units in the fingertip area of the sensor in sequence to verify the crosstalk degree of this structure. The obtained effects are as Figure 7 shown.

[0057] ThroughFigure 7 It can be seen that there is a small crosstalk phenomenon between multiple sensing units adjacent at a distance of 3-4 mm. Compared with the traditional array sensor with upper and lower electrodes, this structure has better anti-interference ability.

[0058] As mentioned above, it is only a further embodiment of the invention, but the protection scope of the invention is not limited thereto. Any person skilled in the art within the scope disclosed by the invention, according to the technical solution and concept of the invention, makes equivalent substitutions or changes, all belong to the protection scope of the invention.

Claims

1. A humanoid fingertip tactile sensor, characterized in that, Comprising: Anthropomorphic finger bones; Bottom permanent magnets arranged on the anthropomorphic finger bones; Flexible circuit boards covering the bottom permanent magnets; Partition fixing layers arranged on the flexible circuit boards, and the partition fixing layers are provided with mounting holes; Piezo-resistive films and top permanent magnets mounted in the mounting holes of the partition fixing layers; Silicone contact layers sleeved on the partition fixing layers.

2. The humanoid fingertip tactile sensor according to claim 1, wherein Mounting grooves are arranged on the anthropomorphic finger bones, and the first permanent magnets are arranged in the mounting grooves.

3. The humanoid fingertip tactile sensor according to claim 1, characterized in that, The number of the mounting grooves and the first permanent magnets is the same, being 24 to 36.

4. The artificial fingertip tactile sensor according to claim 1, characterized in that, The flexible circuit board comprises a flexible substrate and electrode units arranged on the flexible substrate. The number of the electrode units is the same as that of the bottom permanent magnets and the positions are corresponding.

5. The anthropomorphic fingertip tactile sensor according to claim 1, characterized in that, The piezo-resistive films in the mounting holes of the partition fixing layers are closely attached to the electrode units of the flexible circuit board, and the thickness of the piezo-resistive films is 0.05 to 0.15 mm.

6. The anthropomorphic fingertip tactile sensor according to claim 5, characterized in that, The number of the piezo-resistive films, the top permanent magnets and the electrode units of the flexible circuit board is the same, and the positions of the three are corresponding.

7. The anthropomorphic fingertip tactile sensor according to claim 1, characterized in that, Silicone contacts are arranged on the silicone contact layers. The number of the silicone contacts is the same as that of the top permanent magnets and the positions are corresponding.

8. The humanoid fingertip tactile sensor according to claim 1, characterized in that The silicone contact layer comprises silicone and glass microbeads, and the addition amount of the glass microbeads in the silicone contact layer is 3 to 5% of the mass of the silicone.

9. The humanoid fingertip tactile sensor according to claim 1, wherein The silicone contact comprises silicone and glass microbeads, and the addition amount of the glass microbeads in the silicone contact is 3 to 5% of the mass of the silicone.

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