CN115139322A - Dexterous fingertip with multi-point touch perception - Google Patents
Dexterous fingertip with multi-point touch perception Download PDFInfo
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- CN115139322A CN115139322A CN202210806873.6A CN202210806873A CN115139322A CN 115139322 A CN115139322 A CN 115139322A CN 202210806873 A CN202210806873 A CN 202210806873A CN 115139322 A CN115139322 A CN 115139322A
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- Prior art keywords
- fingertip
- array
- piezoresistive
- layer
- silica gel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J13/00—Controls for manipulators
- B25J13/08—Controls for manipulators by means of sensing devices, e.g. viewing or touching devices
- B25J13/081—Touching devices, e.g. pressure-sensitive
- B25J13/084—Tactile sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Human Computer Interaction (AREA)
- Robotics (AREA)
- Mechanical Engineering (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
Abstract
The invention discloses a dexterous hand fingertip with multipoint tactile perception, which comprises a piezoresistive tactile sensing unit, wherein the sensing unit comprises a substrate, an array electrode attached to the substrate, a piezoresistive layer arranged above the array electrode, a plastic packaging layer used for fixing the substrate and the piezoresistive layer, a pre-pressing gasket attached above the plastic packaging layer, a silica gel contact layer arranged above the pre-pressing gasket, and a fingertip base and a fingertip clamping plate for integrally packaging the sensing unit, wherein the silica gel contact layer is provided with array contacts corresponding to the array electrode. The dexterous finger tip can realize the detection of multi-point contact force, has lower manufacturing cost and excellent sensitivity.
Description
Technical Field
The invention relates to the technical field of robot sensing, in particular to a smart fingertip with multi-point touch sensing and a preparation method thereof.
Background
When a robot performs a complex operation task, the robot usually obtains surrounding environment information through various sensors, and most commonly includes a visual sensor, a touch sensor and the like. Due to the increasing development of computer vision and image processing technology, vision sensors have been widely equipped for use by robots. However, many difficulties and challenges still face visual sensing technology, such as the inability of visual sensors to perform in complex environments with dim light and high background interference. Secondly, the physical characteristics of the rigidity, texture, weight and hardness of the object cannot be obtained by the visual sensing technology. Therefore, it has become a current trend to install high-performance tactile sensors for robots to explore the environment and recognize objects. Meanwhile, with the appearance of novel excellent conductive materials such as graphene and multi-walled carbon nanotubes, the touch sensor gradually develops towards high sensitivity, high array and flexibility. This also provides the possibility for the robot to implement a haptic perception capability close to that of a human being.
Although there are many existing fingertip tactile sensor solutions, there are few tactile sensors that can be practically applied to a manipulator fingertip for daily operation assistance. Most of the traditional fingertip sensors are metal products, have large volume and are difficult to integrate into the fingertips of dexterous hands; most of the finger tips are single-point type, so that less finger tip information can be collected, and the exploration requirement of a dexterous hand cannot be met. Therefore, it remains an urgent challenge to develop a flexible array-type tactile sensor having high sensitivity, good stability, and full integration into the tip of a dexterous hand.
Disclosure of Invention
The invention provides a smart fingertip with multipoint touch sensing and a preparation method thereof, aiming at overcoming the technical problems of low array, low sensitivity, low integration level, higher manufacturing cost and the like of fingertip contact sensors in the prior art.
In order to achieve the purpose, the invention adopts the technical scheme that:
the smart finger tip with multi-point touch sensing comprises a piezoresistive touch sensing unit, wherein the sensing unit comprises a substrate, an array electrode attached to the substrate, a piezoresistive layer arranged above the array electrode, a plastic packaging layer used for fixing the substrate and the piezoresistive layer, a pre-pressing gasket attached to the upper side of the plastic packaging layer, a silica gel contact layer arranged above the pre-pressing gasket, and a finger tip base and a finger tip clamping plate for integrally packaging the sensing unit, and the silica gel contact layer is provided with an array contact corresponding to the array electrode.
Furthermore, the substrate is made of a polyimide film, and the array electrode is printed on the polyimide film.
Furthermore, a mounting groove is reserved at the top of the fingertip base for placing the sensor unit, and a sliding groove is formed in the fingertip base and used for mounting the fingertip clamping plate; an array hole is reserved on the fingertip clamping plate and corresponds to the array electrode, so that the contact of the silica gel contact layer is exposed out of the surface of the fingertip, and the fingertip clamping plate is fixed with the fingertip base through a buckle, so that the sensor unit cannot deviate and has certain pre-pressure.
Furthermore, the piezoresistive layer is a velostat conductive film.
Further, the array electrode comprises a common electrode and other electrodes arranged in an array mode, the common electrode is connected with the GND end, the other electrodes are connected with the positive electrode of the power supply, when the sensor unit is pressed, the piezoresistive material in the corresponding area is communicated with the electrodes and the common electrode to form a conductive path with a resistance value, and the size of the resistance value is inversely proportional to the pressure.
Furthermore, the silica gel in the prepressing gasket and the silica gel contact layer adopts Ecoflex0030 two-component liquid platinum-gold silica gel.
Further, the preparation method of the silica gel contact layer comprises the following steps: and pouring the uniformly mixed silica gel and glass microsphere mixture into a mold by using the mold with a hemispherical cavity array, pumping out bubbles in the mixture under the negative pressure of 0.1MPa, curing, demolding to form a flexible contact layer, wherein the mass fraction of the glass microspheres in the silica gel is 5%.
Furthermore, the fingertip base and the fingertip clamping plate are processed in a 3D printing mode and made of epoxy resin.
In summary, the invention has the following beneficial effects:
(1) The integration level is high, the volume is small, and no additional connecting piece is needed during installation;
(2) The fingertip sensor can detect the multipoint contact force and has lower manufacturing cost;
(3) The sensor can have certain initial pre-pressure by arranging the pre-pressing gasket of the silica gel, and a non-linear interval of an initial stage is skipped, so that the detection sensitivity is improved;
(4) The specific amount of the glass beads is added into the silica gel contact layer, so that the elastic modulus of the contact layer can be effectively improved, the contact force of the sensor can be better transmitted to the sensing unit when the sensor is in contact with an object, and the sensitivity of the sensor is improved.
Drawings
Fig. 1 is an exploded view of the overall package of a piezoresistive flexible array tactile sensor according to the invention.
FIG. 2 is a view showing the structure of an electrode of a sensor according to the present invention.
Fig. 3 is a left side view of the sensor fingertip base of the present invention.
FIG. 4 is a comparison of pressure characteristics of the sensor of the present invention with and without a pre-compressed gasket.
In the figure:
the finger tip clamping plate comprises a finger tip clamping plate 1, a silica gel contact layer 2, a silica gel pre-pressing gasket 3, a plastic package film 4, a velostat piezoresistive film 5, an electrode layer 6, a finger tip base 7, a public end electrode 8, an array electrode 9 and a finger tip base bottom sliding groove 10.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention and are not to be construed as limiting the present invention.
The invention discloses a smart fingertip with multipoint tactile perception, which comprises a piezoresistive tactile sensing unit, wherein the sensing unit comprises a substrate, an array electrode attached to the substrate, a piezoresistive layer arranged above the array electrode, a plastic packaging layer for fixing the substrate and the piezoresistive layer (namely, a piezoresistive layer material and the electrode are completely attached through the packaging of the plastic packaging layer), a prepressing gasket attached above the plastic packaging layer, a silica gel contact layer arranged above the prepressing gasket, and a fingertip base and a fingertip clamping plate for integrally packaging the sensing unit, wherein the silica gel contact layer is provided with array contacts corresponding to the array electrode.
In a specific embodiment of the invention, the array electrode comprises 9 electrodes arranged in an array and 1 common electrode, the piezoresistive material covers the electrode layer, wherein the 9 array electrodes are connected with the positive electrode of a power supply, the 1 common electrode is connected with a GND terminal, when the sensing unit is under pressure, the piezoresistive material in the corresponding area can be communicated with the array electrode and the common electrode to form a conductive path with a certain resistance value, the resistance value is inversely proportional to the pressure, and the piezoresistive material can be a velostat conductive film, has excellent piezoresistive characteristics, and can be cut into the shape same as the electrode layer.
In a specific embodiment of the invention, the pre-pressing gasket is a silica gel pre-pressing gasket, and the sensor can have certain initial pre-pressing force by adopting the pre-pressing gasket, so that the response time can be effectively shortened, and the sensitivity can be improved.
In one embodiment of the present invention, the silica gel contact layer is made of a mixture of silica gel and glass beads to greatly improve the sensitivity of the sensor.
Example (b):
the embodiment provides a finger tip design of a dexterous hand with multi-point tactile perception, and the structure of the design is shown in fig. 1: the fingertip comprises piezoresistive tactile sensing units arranged in an array manner, wherein each sensing unit comprises a polyimide film serving as a substrate, a public end electrode and an array electrode attached to the substrate, a piezoresistive layer fixed above the substrate, a plastic packaging layer used for fixing the substrate and the piezoresistive layer, a prepressing gasket attached above the plastic packaging layer, a silica gel contact layer fixed above the prepressing gasket, and a fingertip base and a fingertip clamping plate for integrally packaging the sensing units.
In the fingertip structure of fig. 1, a schematic diagram of the electrode structure in the piezoresistive flexible array tactile sensing unit arranged in an array is shown in fig. 2: public terminal electrodes and array electrodes arranged in a 3 multiplied by 3 mode are attached to the substrate, wherein the public terminal electrodes 8 are used for grounding, the array electrodes 9 are connected with the multiplexing switch, and the anodes are connected in turn through a time division multiplexing method.
The right view of the fingertip base is shown in fig. 3, two sliding grooves are designed at the bottom of the base and used for being fixed with the fingertip clamping plate in a buckling mode, a connecting piece is omitted in the fixing mode, and the mounting and dismounting are simple.
As an improvement, the substrate is further provided with an electrical leading-out part of each electrode, the electrodes of each pressure sensing unit are led out to the outside, and the pressure sensing units are conveniently and electrically connected with the outside.
The working principle of the piezoresistive flexible array tactile sensor based on the structure is as follows: when the touch sensor is not under pressure, the piezoresistive membrane 5 is only subjected to an initial pre-stress between the fingertip splint 1 and the fingertip base 7, and the resistance of the piezoresistive membrane is the initial resistance. When the sensor contacts an external object, the spherical contact of the silica gel contact layer 2 deforms, the force applied to the contact is transmitted to the piezoresistive film 5, the resistance of the piezoresistive film is reduced after the piezoresistive film is pressed due to the characteristics of piezoresistive materials, the current in the circuit is increased, but the current signal in the loop cannot be directly measured by the single chip microcomputer, the sensing unit is connected with a divider resistor R in series, and the voltage of the sensing unit is measured by the single chip microcomputer to reflect the pressure signal applied to the sensing unit. The larger the pressure borne by the flexible contact is, the larger the voltage of the voltage dividing resistor is, until the resistance of the piezoresistive material reaches the minimum value, and at the moment, the pressure sensing unit also reaches the maximum range of pressure monitoring.
When the pressure applied to the touch sensor is released, the conductive path in the piezoresistive material is restored to its original state, the resistance is also restored to its original value, and the electrical signal output by the touch sensor unit is restored to its original value in the absence of the external pressure.
Because the sensor is provided with a plurality of sensing contacts to form an array, in order to save occupation of a single chip microcomputer acquisition peripheral, a multiplexer is adopted to carry out cyclic gating on the acquisition unit, the single input end of the multiplexer is connected with the anode of a power supply, and the multi-path output end of the multiplexer is connected with each sensing unit, so that a sensing unit forms a complete acquisition loop during each acquisition. Because the clock frequency of the single chip microcomputer is extremely high, the single chip microcomputer can be regarded as simultaneously collecting all the sensing units.
On the other hand, this embodiment also provides a method for manufacturing the above sensor, firstly preparing an electrode layer, sputtering a copper film on a polyimide film substrate by using a metal sputtering method, forming a common electrode and an array electrode arranged as shown in fig. 4, and sputtering lead-out portions constituting the respective electrodes by the same method.
And then packaging the piezoresistive layer and the electrode layer, covering plastic packaging films below the electrode substrate and above the piezoresistive film, and thermally bonding the plastic packaging films and enabling the electrode substrate to be completely attached to the piezoresistive material under the heating of a plastic packaging machine.
And then preparing a flexible contact layer 2 and a silica gel pre-pressing gasket 3, wherein the flexible contact layer and the silica gel pre-pressing gasket are respectively injected by adopting dies A and B, and Ecoflex0030 two-component liquid platinum-gold silica gel is adopted. Mixing and injecting the two-component room temperature curing platinum catalytic silicone rubber prepared according to the proportion of 1. When the flexible contact is prepared, the glass beads with the mass fraction of 5% are added into the uniformly mixed silica gel and are mixed, and then the mixture is injected into the mold A, so that the prepared flexible contact has more excellent elastic modulus, and the sensitivity of the sensor can be improved.
As can be seen from fig. 4, the pressure characteristic curve of the sensor without the pre-pressure pad can be roughly divided into 3 stages, the sensitivity of the first stage and the third stage is high, but the sensitivity of the middle stage is low, and the linearity of the three stages is low, so that it is difficult to fit the curve with a common linear or polynomial curve. Therefore, in order to skip the first and second stages, a pre-pressure pad is added to the sensor, and it can be seen that the pressure characteristic curve of the sensor under pre-pressure is similar to a binomial curve and the sensitivity is high.
The fingertip pressure sensor based on the structure and the preparation method has the following advantages: (1) The integration level is high and small, need not extra any connecting piece during the installation. (2) The fingertip sensor can detect the multipoint contact force and has lower manufacturing cost; (3) The sensor can have certain initial pre-pressure through the silica gel pre-pressing gasket, and a non-linear interval of an initial stage is skipped; (4) A certain amount of glass beads are added into the silica gel contact layer, so that the elastic modulus of the contact layer is improved, the contact force of the sensor can be better transmitted to the sensing unit when the sensor contacts an object, and the sensitivity of the sensor is improved.
It should be noted that the above-mentioned embodiments are merely illustrative of the preferred embodiments and principles of the present invention, and those skilled in the art will appreciate that there may be variations to the embodiments based on the concepts provided by the present invention and that such variations are to be considered as within the scope of the present invention.
Claims (8)
1. The utility model provides a dexterous fingertip with multiple spot tactile sensation, its characterized in that, includes piezoresistive tactile sensing unit, and this sensing unit is including as the base plate, attached to the array electrode on the base plate, locating the piezoresistive layer of array electrode top, the plastic envelope layer that is used for fixed substrate and piezoresistive layer, attached to the pre-compaction gasket of plastic envelope layer top, locating the silica gel contact layer of pre-compaction gasket top and with the whole fingertip base and the fingertip splint of encapsulation of sensing unit, be equipped with the array contact on the silica gel contact layer with the array electrode corresponds.
2. The smart fingertip of claim 1, wherein the substrate is a polyimide film, and the array electrodes are printed on the polyimide film.
3. The smart fingertip with multi-point tactile sensation according to claim 1, wherein a mounting groove is reserved at the top of the fingertip base for placing a sensor unit, and a sliding groove is formed in the fingertip base for mounting a fingertip clamping plate; an array hole is reserved on the fingertip clamping plate and corresponds to the array electrode, so that a contact of the silica gel contact layer is exposed out of the surface of a fingertip, and the fingertip clamping plate is fixed with the fingertip base through a buckle, so that the sensor unit cannot deviate and has certain pre-pressure.
4. The smart fingertip of claim 1, wherein the piezoresistive layer is a velostat conductive film.
5. The smart finger tip with multi-touch sensing function according to claim 1, wherein the array electrode comprises a common electrode and the rest of the electrodes arranged in an array, the common electrode is connected to the GND terminal, the rest of the electrodes are connected to the positive electrode of the power supply, when the sensor unit is pressed, the piezoresistive material in the corresponding region connects the electrodes and the common electrode to form a conductive path with a resistance value, and the magnitude of the resistance value is inversely proportional to the magnitude of the pressure.
6. The dexterous fingertip of claim 1, wherein the pre-pressing pad and the silicone in the silicone contact layer are both Ecoflex0030 two-component liquid platinum-gold silicone.
7. The smart fingertip of claim 1, wherein the silicone contact layer is formed by a method comprising: and pouring the uniformly mixed silica gel and glass microsphere mixture into a mold by using the mold with a hemispherical cavity array, pumping out bubbles in the mixture under the negative pressure of 0.1MPa, curing, demolding to form a flexible contact layer, wherein the mass fraction of the glass microspheres in the silica gel is 5%.
8. A multi-touch sensitive smart finger tip as claimed in claim 1, wherein the base and the clamping plates are both 3D printed and made of epoxy resin.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210806873.6A CN115139322A (en) | 2022-07-08 | 2022-07-08 | Dexterous fingertip with multi-point touch perception |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210806873.6A CN115139322A (en) | 2022-07-08 | 2022-07-08 | Dexterous fingertip with multi-point touch perception |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115139322A true CN115139322A (en) | 2022-10-04 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210806873.6A Pending CN115139322A (en) | 2022-07-08 | 2022-07-08 | Dexterous fingertip with multi-point touch perception |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115139322A (en) |
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2022
- 2022-07-08 CN CN202210806873.6A patent/CN115139322A/en active Pending
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