CN104406627A - Wearable flexible touch sensor of artificial hand and touch detection system thereof - Google Patents

Abstract

The invention discloses a prosthetic hand wearable flexible touch sensor and a touch detection system thereof. Closely fit the flexible electrode layer, the middle layer and the PDMS convex layer from bottom to top; the middle layer includes a conductive rubber array and surrounding flexible fillers. The electrode group, the conductive rubber unit has the same side length as a group of test electrode groups on the flexible electrode layer; the PDMS convex layer is provided with a micro-projection structure, which is located directly above the conductive rubber unit; the flexible electrode layer is in the shape of a "cross" The flexible circuit board of the structure is provided with Velcro fasteners on the stretched edge edges of the upper, left and right sides of the flexible circuit board so as to be worn on the fingers. The invention has a simple structure and is easy to manufacture, solves the problem that most tactile sensors cannot detect three-dimensional contact force and slip signals at the same time, and can be conveniently bound to the irregular curved surface of the support inside the prosthetic finger.

Description

Wearable flexible tactile sensor for prosthetic hand and its tactile detection system

technical field

The invention relates to a tactile sensor and a detection system thereof, in particular to a prosthetic hand-worn flexible tactile sensor and a tactile detection system thereof.

Background technique

The tactile sensor is an indispensable means for the intelligent prosthetic hand to obtain contact information. According to the information provided by the tactile sensor, the intelligent prosthetic hand can reliably grasp the target object, and can further perceive its physical characteristics such as size, shape, weight, softness and hardness. . The unreliable grasping caused by the inability to obtain contact information when the intelligent prosthetic hand grasps the object will bring great danger. Most of the existing tactile sensors used in intelligent prosthetic hands can only detect the normal force, but cannot detect the magnitude of the tangential force. But the detection of tangential force plays a very important role in the reliability of grasping. And the tactile sensor applied to the intelligent prosthetic hand requires the tactile sensor to be highly flexible and miniaturized, and can be firmly attached to the surface of the finger and integrated in the finger of the intelligent prosthetic hand. Effective mounting methods also play a vital role in the reliability of tactile sensors.

China National Invention Patent (publication number CN201210193314.9) discloses a humanoid robot multi-finger flexible three-dimensional force tactile sensor and its three-dimensional force detection system. The sensor uses Quantum Tunneling Composites (QTC), a pressure-sensitive composite material with quantum tunneling effect. When QTC is not pressed by external force, its body is an insulator with a resistance value as high as 1kΩ; when QTC is pressed by external force, the body compresses Deformation, QTC exhibits conductive properties, and the resistance value gradually decreases with the increase of pressure. The sensor is flexible as a whole and can detect three-dimensional forces. However, the sensor electrode circuit is divided into upper and lower layers, which is easy to damage the circuit during long-term stress, and does not explain the effective installation method of the tactile sensor, which affects the reliability of the tactile sensor and is difficult to meet the needs of intelligent prosthetic hand motion feedback control.

Contents of the invention

Aiming at the problem of unreliable installation of the existing tactile sensor and its detection system in the prosthetic hand, and the problem of the simple signal acquisition circuit design of the existing tactile sensor, the purpose of the present invention is to provide a prosthetic hand-worn flexible tactile sensor and its The overall design of the tactile detection system solves the problem that most tactile sensors cannot detect three-dimensional contact force and slip signals at the same time, and can be conveniently bound to the irregular curved surface of the support body inside the finger of the intelligent prosthetic hand, which can be used for three-dimensional contact force and detection of slip signals.

The technical scheme adopted in the present invention is:

1. A wearable flexible tactile sensor for a prosthetic hand:

Closely fit the flexible electrode layer, the middle layer, and the PDMS raised layer from bottom to top; the middle layer includes a conductive rubber array with pressure-sensitive effect and a flexible filler filled around the conductive rubber array, and the conductive rubber array is composed of a conductive rubber unit array. The flexible electrode layer directly below the conductive rubber unit is provided with a test electrode group. The array distribution of the test electrode group and the conductive rubber unit is the same. The conductive rubber unit and a group of test electrode groups on the flexible electrode layer The length is the same; the PDMS convex layer is provided with a micro-boss structure corresponding to each conductive rubber unit, located directly above the conductive rubber unit; the flexible electrode layer is a flexible circuit board with a "cross" structure, the middle layer and the PDMS convex layer Covered in the middle of the "ten" shape, the test electrode group is covered in the middle of the "ten" shape and the stretched sides on the lower side, and the stretched edges on the upper, left and right sides of the flexible circuit board are provided with Velcro for binding sensors Velcro closure for easy finger wear.

Each set of test electrode groups described is a five-electrode structure in a square shape, and the five-electrode structure is composed of four right-angled triangle electrodes evenly distributed at the four corners and a square electrode in the center, and the square electrode in the center is used as a common electrode; All the square electrodes of the row test electrode group are connected in series through the leads of the parallel wiring method to lead out the pins, and the right-angled triangle electrodes with the same position in the test electrode group on the same column are connected in series through the leads of the parallel wiring method to lead out the pins, M In the row test electrode group, M pins are drawn out from square electrodes as row electrodes, and in the N-column test electrode group, 4N pins are drawn out from right-angled triangle electrodes as column electrodes.

The conductive rubber arrays are bonded together by flexible fillers cured at room temperature.

The conductive rubber array is distributed in a 3×3 array, and the conductive rubber unit is a square conductive rubber sheet.

The conductive rubber array uses Inastomer conductive rubber produced by INABA Corporation of Japan, the flexible electrode layer is a double-sided flexible circuit board, and polyimide film is used as a substrate.

2. A wearable flexible tactile detection system for a prosthetic hand:

Including the flexible tactile sensor and signal acquisition circuit, the signal acquisition circuit includes a power conversion module, a microprocessor, an operational amplifier circuit and an analog multi-channel selection module, and the microprocessor contains an analog-to-digital conversion module multi-channel ADC; the flexible The pins drawn from the column electrodes of the tactile sensor are respectively connected to the negative phase input terminals of the respective operational amplifier circuits, the two ends of the reference resistor R are respectively connected to the negative phase input terminals and the output terminals of the operational amplifier circuits, and the output terminals of the operational amplifier circuits It is connected with the ADC analog signal input terminal in the microprocessor; the external power supply is connected to the power conversion module to generate a negative 3.3V power supply voltage, and the multi-way switch input terminal of the analog multiplex selection module is connected with the negative 3.3V power supply voltage. The pins drawn from the row electrodes of the sensor are respectively connected to the signal output ends of the analog multiplex module; the microprocessor is connected to the analog multiplex module to control the selective on-off of the multiplex switch, The channel selection module sends an on-off control signal to sequentially select the negative 3.3V power supply voltage and each pin drawn from the row electrode of the flexible tactile sensor; the output voltage of the pins drawn from the column electrode of the flexible tactile sensor The analog signal is amplified by the operational amplifier circuit and then connected to the microprocessor for AD sampling to obtain a voltage digital signal.

The microprocessor adopts TMS320F28069 of TI Company, which contains 12-bit analog-to-digital converter ADC, which can double sample and hold, and at most 16 channel signals can be collected simultaneously.

The analog multi-channel selection module adopts TS5A3359 single-pole three-throw normally open analog switch of TI Company.

The operational amplifier circuit adopts the OPA656 chip of TI Company.

The power conversion module adopts a bipolar power circuit constructed by TPS65135 power conversion chip of TI Company.

The beneficial effects of the present invention are:

(1) The tactile sensor of the present invention has a simple structure and is easy to manufacture, which effectively reduces the processing cost of the sensor, and can simultaneously detect three-dimensional force and recognize slippage.

(2) The tactile sensor used in the present invention has overall flexibility and flexibility. The Velcro structure design is adopted on the flexible circuit board, and the sensor can be bound in three directions, and it can be worn on the surface of the finger or the finger firmly and conveniently. on the internal support.

(3) The tactile sensor and its detection system of the present invention are installed inside the finger, and are in contact with the external force through the flexible PDMS raised layer, which can effectively improve the detection sensitivity of the flexible tactile sensing array and protect the electrodes inside the composite sensing array. and leads.

(4) In the present invention, the electrodes on the flexible electrode layer are grouped and connected in parallel, which effectively reduces the number of external pins of the tactile sensor. Its signal processing circuit has simple structure and small size.

Description of drawings

Figure 1 is a top view of the present invention.

Fig. 2 is a schematic cross-sectional structure diagram of the tactile sensing array of the present invention.

Fig. 3 is a schematic diagram of a flexible electrode layer with Velcro according to the present invention.

Fig. 4 is a schematic diagram of a conductive rubber array filled with flexible fillers in the present invention.

Fig. 5 is the raised layer of PDMS of the present invention.

FIG. 6 is a schematic structural diagram of the tactile sensing array unit of the present invention.

Fig. 7 is a schematic diagram of the test electrode of the present invention.

FIG. 8 is a schematic diagram of the testing principle of the tactile sensing array unit of the present invention.

Fig. 9 is one of the installation diagrams of the present invention.

Fig. 10 is the second installation diagram of the present invention.

Fig. 11 is a schematic diagram of the connection structure of the system of the present invention.

In the figure: 1. PDMS convex layer, 2. Conductive rubber array, 3. Flexible filler, 4. Flexible electrode layer, 5. Micro-boss structure, 6. Conductive rubber unit, 7. Test electrode group, 8. Dimensional It can be firmly Velcro, 9. Row electrodes, 10. Column electrodes.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Tactile sensor of the present invention is as shown in Figure 1:

As shown in Figure 2, the present invention includes a flexible electrode layer 4, an intermediate layer, and a PDMS raised layer 1 closely attached from bottom to top; as shown in Figure 3, the flexible electrode layer 4 is a flexible circuit board with a "cross" structure, The middle layer and the PDMS protruding layer 1 cover the middle part of the "ten" shape, the test electrode group 7 covers the middle part of the "cross" shape and the stretching side on the lower side, and the stretching side edges on the upper side, left side and right side are provided with for binding Velcro 8 with a fixed sensor, so that it can be firmly worn on the surface of the intelligent prosthetic finger or on the support inside the intelligent prosthetic finger; as shown in Figure 4, the middle layer includes a conductive rubber array 2 with pressure-sensitive effect and The flexible filler 3 filled around the conductive rubber array 2, the conductive rubber array 2 is formed by an array of conductive rubber units 6; as shown in Figure 5, the PDMS raised layer 1 is provided with The micro boss structure 5; as shown in Figure 6, the micro boss structure 5 is located directly above the conductive rubber unit 6, and the flexible electrode layer 4 directly below the conductive rubber unit 6 is provided with a test electrode group 7, and the test electrode group 7 and The conductive rubber units 6 are distributed in the same array, and the side lengths of the conductive rubber units 6 and a set of test electrode groups 7 on the flexible electrode layer 4 are the same.

The installation diagram of the present invention is shown in Fig. 9 and Fig. 10 . The flexible electrode layer 4 of the present invention is a flexible circuit board. Generally, polyimide film is commonly used as the base material. The buckle structure is composed of a fabric with a small hook on one side and a fabric with a small plush loop on the other side. The two sides have the characteristics of "bond when touched, and separated when pulled". The sensor is bound in three directions by Velcro 8 , and can be firmly and conveniently worn on the surface of the smart prosthetic finger or on the irregular curved surface of the support inside the smart prosthetic finger.

As shown in Figure 3, each group of test electrode groups 7 is a five-electrode structure in the shape of a square. The five-electrode structure is composed of four right-angled triangle electrodes evenly distributed at the four corners and a square electrode in the center. The square electrode in the center serves as Common electrodes; all square electrodes of each row of test electrode groups 7 are connected in series through lead wires in a parallel wiring mode and lead out pins, and right-angled triangle electrodes with the same position in the test electrode group 7 on the same column are connected in series through lead wires in a parallel wiring mode Then lead out the pins, M rows of test electrode groups 7 lead out M pins from square electrodes as row electrodes 9 , and N columns of test electrode groups 7 lead out 4N pins from right-angled triangle electrodes as column electrodes 10 . As shown in FIG. 6 , a tactile sensing array unit is composed of a group of test electrode groups 7 , a conductive rubber unit 6 and a micro-projection structure 5 covering it.

The conductive rubber array 2 filled with flexible fillers 3 can be composed of 3×3 square conductive rubber sheets with the same pressure-sensitive properties, and the conductive rubber array 2 is formed by bonding the flexible fillers 3 cured at room temperature. The number of test electrode groups 7 is the same as the number of conductive rubber units 6 in the conductive rubber array 2 , and the test electrode groups 7 of the flexible electrode layer 4 are also distributed in a 3×3 array.

The conductive rubber array 2 uses Inastomer conductive rubber produced by INABA Corporation of Japan, and the flexible electrode layer 4 is a double-sided flexible circuit board, using polyimide film as a substrate.

According to the requirements of specific applications, such as required spatial resolution, three-dimensional force range, sensor sensitivity, detection accuracy, degree of bending deformation and other indicators, determine the size of the flexible tactile sensing array, the sensing unit of the tactile sensing array size and spacing between cells. The range and sensitivity of the three-dimensional force are determined by the size of the conductive rubber sheet in the sensing unit of the tactile sensing array and the size and spacing of the five-electrode square structure.

The manufacturing process of the sensor is as follows: First, the flexible electrode layer 4 is manufactured by flexible circuit printing technology, and the high-purity conductive silver glue is spin-coated on the test electrode group 7 of the flexible electrode layer 4 by using the screen printing technology; then the square conductive rubber The sheet is pasted on the test electrode group 7; then the flexible filler 3 is filled into the blank part of the flexible electrode layer 4, and cured at room temperature; finally, the PDMS raised layer 1 embossed by the mold for the second time is bonded around and filled with Flexible filler 3 on the conductive rubber array 2 . In this way, a flexible tactile sensing array as shown in Fig. 1 and Fig. 2 is obtained.

The three-dimensional contact force and slip detection principle of the present invention are as follows:

As shown in Figure 6, Figure 7 and Figure 8, the three-dimensional force in any direction transmits the force to the conductive rubber unit 6 through the micro-projection structure 5 of the PDMS raised layer 1, and the elastic deformation of the surrounding flexible filler 3 is higher than that of the conductive rubber. Unit 6 is large. Due to the piezoresistive effect of the conductive rubber unit 6 and the contact resistance between the conductive rubber array 2 and the flexible electrode layer 4, there are four equivalent resistances R1, R2, R3, R4. When the conductive rubber unit 6 is strained, the resistance value will change. The four resistors respectively output the corresponding voltage signals through their respective detection circuits, which are transformed into the measurement of the three-dimensional forces Fx , Fy , and Fz through the following principles, so as to obtain any three-dimensional force.

When only Fx works, the resistors R1 and R4 decrease because of the same degree of compressive strain; because of the same degree of tensile stress, the resistors R2 and R3 increase, and the increase of the resistors R2 and R3 is equal to the decrease of the resistors R1 and R4 Same by a small margin.

When only Fy works, because of the same degree of compressive strain, the resistance R1 and R2 decrease; because of the same degree of tensile stress, the resistance R3 and R4 increase, and the increase of resistance R3 and R4 is the same as that of resistance R1 and R2. Same by a small margin.

When only Fz works, the resistances R1, R2, R3, and R4 decrease because of the same degree of compressive strain, and the reduction range is the same.

According to the above analysis, the relationship between the three-dimensional force and the resistance changes of the four piezoresistors can be deduced. The three-dimensional force and the resistance change data of the four piezoresistors were obtained through multiple experiments, and the linear relationship between the force in the three-dimensional direction and the resistance change of the four piezoresistors was obtained through linear decoupling, so that the actual three-dimensional force can be accurately measured .

In addition, because the present invention can use Inastomer conductive rubber, which has excellent piezoresistive effect, low hysteresis performance, high linearity, and can identify slip signals with high frequency and low amplitude. After the three-dimensional force is measured, the horizontal tangential force is analyzed through signal processing, and the high-frequency and low-amplitude slip mutation signal in the horizontal direction is extracted by wavelet analysis, which can quickly determine whether slip occurs, and is suitable for adjustment during the process of grabbing objects by the robot hand The size of the grip force realizes the dynamic balance of the grip force.

As shown in Figure 11, the tactile detection system of the present invention includes the flexible tactile sensor and the signal acquisition circuit, and the signal acquisition circuit includes a power conversion module, a mixed-signal array programmable microprocessor, an operational amplifier circuit and an analog multiplexer. Select the module, the microprocessor contains an analog-to-digital conversion module multi-channel ADC; the pins drawn from the column electrodes 10 of the flexible tactile sensor are respectively connected to the negative phase input terminals of the respective operational amplifier circuits, and the two ends of the reference resistor R are respectively connected to the operational amplifier On the negative input and output terminals of the circuit, the output terminal of the operational amplifier circuit is connected to the ADC analog signal input terminal in the microprocessor; the external power supply is connected to the power conversion module to generate a negative 3.3V power supply voltage, which simulates the multi-channel selection module. The multi-way switch input terminal is connected with the negative 3.3V power supply voltage, and the pins drawn by the row electrode 9 of the flexible tactile sensor are respectively connected with each signal output terminal of the analog multi-way selection module; the microprocessor is connected with the analog multi-way selection module to control For the selective on-off of the multi-way switch, the microprocessor sends an on-off control signal to the analog multi-way selection module, and the negative 3.3V power supply voltage and each pin led out by the row electrode 9 of the flexible tactile sensor are sequentially selected; The pins of the column electrodes of the tactile sensor output voltage analog signals, which are amplified by the operational amplifier circuit and then connected to the microprocessor for AD sampling to obtain voltage digital signals.

Embodiment of the present invention and implementation work process are as follows:

The flexible electrode layer 4 adopts a double-sided flexible circuit board structure, and a polyimide film is used as a substrate. The pins are drawn out of the five-electrode structure of each test electrode group 7, and the 3-row test electrode group 7 has 3 pins drawn from square electrodes as row electrodes 9, and the 3-column test electrode group has 12 pins drawn from right-angled triangle electrodes as columns. electrode 10. The 12 pins drawn from the column electrode 10 of the flexible tactile sensor are respectively connected to the negative phase input ends of 12 operational amplifier circuits, and the 3 pins drawn from the row electrode 9 of the flexible tactile sensor are respectively connected to the 3 pins of the analog multiplexer module. Signal output connection.

The mixed-signal array programmable microprocessor contains 16-channel 12-bit analog-to-digital converter ADC, which can be double-sampled and held, and can simultaneously collect up to 16-channel signals, and includes an external data transmission port. The external data transmission port is SP Serial interface, I ² C serial interface or UART serial interface, adopt TMS320F28069 of TI Company.

The analog multi-channel selection module uses TI's TS5A3359 single-pole three-throw normally open analog switch.

The operational amplifier circuit adopts the OPA656 chip of TI Company, and the measurement method based on the current-to-voltage conversion method can be used.

The power conversion module adopts a bipolar power circuit built by TI's TPS65135 power conversion chip.

Through actual sensor manufacturing, performance calibration and slip detection experiments, it is measured that the flexible tactile sensor of the prosthetic hand and its detection system of the present invention have good pressure-sensitive characteristics, can detect three-dimensional force sensitively, and its tactile detection system has stable performance. Compared with the Chinese invention patent (CN201210193314.9), the sensitivity of the three-dimensional force of the measured sensor is increased by 10%, 10%, and 15%, respectively. At the same time, due to the particularity of the selected pressure-sensitive conductive rubber material, the low-amplitude and high-frequency slip signal is extracted from the original signal through signal processing, and the slip is effectively identified, which provides a strong guarantee for the intelligent application of the prosthetic hand. Has a significant technical effect.

The above specific embodiments are used to explain the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (10)

1. A prosthetic hand-worn flexible tactile sensor, characterized in that: the flexible electrode layer (4), the middle layer and the PDMS raised layer (1) are closely attached from bottom to top; the middle layer includes conductive rubber with pressure-sensitive effect The array (2) and the flexible filler (3) filled around the conductive rubber array (2), the conductive rubber array (2) is formed by an array of conductive rubber units (6), and the conductive rubber unit (6) is directly below The flexible electrode layer (4) is provided with a test electrode group (7), and the array distribution of the test electrode group (7) and the conductive rubber unit (6) is the same, and the conductive rubber unit (6) is connected to the flexible electrode layer (4). A set of test electrode groups (7) has the same side length; the PDMS convex layer (1) is provided with a micro-projection structure (5) corresponding to each conductive rubber unit (6), and is located on the positive side of the conductive rubber unit (6). Above; the flexible electrode layer (4) is a flexible circuit board with a "ten" structure, the middle layer and the PDMS raised layer (1) cover the middle of the "ten", and the test electrode group (7) covers the middle of the "cross" and the lower stretching edge, the stretching edge edges on the upper, left and right sides of the flexible circuit board are provided with Velcro (8) for binding the sensor so that it can be worn on the finger. 2. A prosthetic hand-worn flexible tactile sensor according to claim 1, characterized in that: each set of test electrode groups (7) is a five-electrode structure in the shape of a square, and the five-electrode structure is uniformly distributed Composed of four right-angled triangle electrodes at the four corners and a square electrode in the center, the square electrode in the center is used as a common electrode; all the square electrodes of each row of test electrode groups (7) are connected in series through parallel wiring leads to lead out the pins, The right-angled triangular electrodes in the same position in the test electrode group (7) on the same column are connected in series through the leads of the parallel wiring method to lead out the pins, and the M rows of test electrode groups (7) have M pins drawn from the square electrodes as row electrodes (9), N columns of test electrode groups (7) lead out 4N pins from right-angled triangle electrodes as column electrodes (10). 3. The prosthetic hand-worn flexible tactile sensor according to claim 1, characterized in that: the conductive rubber array (2) is bonded together by a flexible filler (3) cured at room temperature. 4. A prosthetic hand-worn flexible tactile sensor according to claim 1, characterized in that: the conductive rubber array (2) is distributed in a 3×3 array, and the conductive rubber unit (6) is a square conductive rubber piece. 5. A prosthetic hand-worn flexible tactile sensor according to claim 1, characterized in that: the conductive rubber array (2) adopts Inastomer conductive rubber produced by Japan INABA Company, and the flexible electrode layer (4) is double Surface flexible circuit board, using polyimide film as the substrate. 6. A prosthetic hand-worn flexible tactile detection system comprising the sensor of any one of claims 1 to 5, characterized in that: it includes the flexible tactile sensor and a signal acquisition circuit, and the signal acquisition circuit includes a power conversion module, A microprocessor, an operational amplifier circuit and an analog multi-channel selection module, the microprocessor contains a multi-channel ADC of an analog-to-digital conversion module; The pins drawn from the column electrodes (10) of the flexible tactile sensor are respectively connected to the negative phase input terminals of the respective operational amplifier circuits, and the two ends of the reference resistor are respectively connected to the negative phase input terminals and output terminals of the operational amplifier circuits, The output terminal of the operational amplifier circuit is connected to the ADC analog signal input terminal in the microprocessor; the external power supply is connected to the power conversion module to generate a negative 3.3V power supply voltage, and the multi-way switch input terminal of the analog multi-way selection module is connected to the negative 3.3V power supply voltage connected, the pins drawn from the row electrodes (9) of the flexible tactile sensor are respectively connected to each signal output terminal of the analog multiplexer module; the microprocessor is connected to the analog multiplexer module to control the selectivity of the multiplexer On-off, the microprocessor sends an on-off control signal to the analog multi-channel selection module, and the negative 3.3V power supply voltage and each pin drawn from the row electrode (9) of the flexible tactile sensor are sequentially selected; The pins led by the column electrodes (10) of the flexible tactile sensor output voltage analog signals, which are amplified by an operational amplifier circuit and then connected to a microprocessor for AD sampling to obtain voltage digital signals. 7. The prosthetic hand wearable flexible tactile detection system according to claim 6, characterized in that: the microprocessor adopts TMS320F28069 of TI Company, which contains a 12-bit analog-to-digital converter ADC. 8. A wearable flexible tactile detection system for a prosthetic hand according to claim 6, characterized in that: said analog multi-channel selection module adopts TS5A3359 single-pole three-throw normally open analog switch of TI Company. 9. A prosthetic hand wearable flexible tactile detection system according to claim 6, characterized in that: said operational amplifier circuit adopts OPA656 chip of TI Company. 10. The prosthetic hand wearable flexible tactile detection system according to claim 6, characterized in that: said power conversion module adopts a bipolar power supply circuit built by TI's TPS65135 power conversion chip.