阅读说明：本技术 一种神经形态输出的压阻型触觉传感单元 (Piezoresistive tactile sensing unit for nerve form output ) 是由 刘卫华 苑菀彬 韩传余 张嘉贺 贾瑞强 李昕 于 2020-04-29 设计创作，主要内容包括：本发明公开的一种神经形态输出的压阻型触觉传感单元,压阻电桥电路、前端调理电路和脉冲编码器电路原位集成,当按压操作发生时压敏电阻阻值变化引起电桥失衡,电桥两端电压产生差异并进一步由前端调理电路经求差运算输出至脉冲编码器电路,脉冲编码器电路将电压信号转换为脉冲信号输出,从而实现神经形态的触觉信息输出,脉冲编码器中晶体管输出电流IDS作为触觉信号,由一个Mott忆阻器和一个电容原位转换成频率与IDS大小相关的脉冲信号,从而实现神经形态的触觉信息输出；该神经形态输出的压阻型触觉传感单元具有高灵敏度、低功耗、易于集成和良好的生物兼容性特征,具有一定应用前景。(The invention discloses a piezoresistive tactile sensing unit for neural form output, which is characterized in that a piezoresistive bridge circuit, a front end conditioning circuit and a pulse encoder circuit are integrated in situ, when pressing operation occurs, the resistance value of a piezoresistor changes to cause bridge unbalance, voltages at two ends of a bridge generate difference and are further output to the pulse encoder circuit through difference calculation by the front end conditioning circuit, the pulse encoder circuit converts a voltage signal into a pulse signal to be output, so that neural form tactile information is output, transistor output current IDS in the pulse encoder is used as a tactile signal, and a Mott memristor and a capacitor are converted into a pulse signal with frequency related to IDS in situ, so that neural form tactile information is output; the piezoresistive tactile sensing unit for the nerve morphology output has the characteristics of high sensitivity, low power consumption, easiness in integration and good biocompatibility, and has a certain application prospect.)

1. A piezoresistive tactile sensing unit for nerve morphology output is characterized by comprising a piezoresistive bridge circuit, a front end conditioning circuit and a pulse encoder circuit which are sequentially connected;

the piezoresistive bridge circuit is used for acquiring tactile information and outputting the tactile information to the front-end conditioning circuit;

the front-end conditioning circuit is used for calculating the input tactile information and outputting the calculated tactile information to the pulse encoder circuit;

and the pulse coding circuit is used for converting the input tactile information into a tactile pulse sequence signal in a neural form and outputting the signal.

2. The piezoresistive tactile sensing unit according to claim 1, wherein said piezoresistive bridge circuit comprises a wheatstone bridge and a voltage regulator connected thereto, and the piezoresistors in the wheatstone bridge are tactile sensors.

3. The piezoresistive tactile sensing unit according to claim 1, wherein said wheatstone bridge is a single-arm bridge, a double-arm bridge or a full-arm bridge.

4. The piezoresistive tactile sensing unit according to claim 2 or 3, wherein said Wheatstone bridge comprises four resistors, at least one of which is a piezoresistor and the others are fixed resistors;

resistance R_aResistance R_bResistance R_cAnd a resistance R_dSequentially connecting the head and the tail;

the resistor R_aAnd a resistance R_bAnd a resistor R, and_{d and}resistance R_cThe connecting end of the connecting rod is connected with the constantThe positive and negative poles of the flow source;

the resistor R_aAnd a resistance R_dThe connecting end is an output end V₁Resistance R_cAnd a resistance R_bThe connecting end is an output end V₂。

5. The piezoresistive tactile sensing unit according to claim 1, wherein said front-end conditioning circuitry comprises 3 operational amplifiers and 4 resistors;

operational amplifier A₁And operational amplifier A₂The input end of the operational amplifier A is respectively connected with the output end of the piezoresistive bridge circuit and is used as a voltage follower to realize front and rear stage isolation, and the operational amplifier A₁And operational amplifier A₂Output terminal of and operational amplifier A₃The input ends of the two-way valve are connected;

the operational amplifier A₃And 4 resistors constitute a subtraction circuit for performing subtraction operation on the tactile information and outputting the tactile information.

6. The piezoresistive tactile sensing unit according to claim 1 or 5, wherein said front-end conditioning circuit comprises 3 operational amplifiers and 4 resistors;

operational amplifier A₁Output end V of the positive phase and piezoresistive bridge circuit₁Connected to the inverting and output terminals of the operational amplifier A1 and the resistor R₁Is connected to a resistor R₁The other end and a resistor R₄And an operational amplifier A₃Is connected in anti-phase, resistor R₄And the other end of (1) and an operational amplifier A₃Is connected with the output end of the power supply.

Operational amplifier A₂Output end V of the positive phase and piezoresistive bridge circuit₂Connected to the inverting and output terminals of the operational amplifier A2 and the resistor R₂Is connected to a resistor R₂Another terminal resistance R₃And an operational amplifier A₃Is in the positive phase connection, operational amplifier A₃And the other end of the same is grounded.

7. The neuromorphic output piezoresistive tactile sensing unit according to claim 1, wherein said pulse encoder circuitry comprises transistors, a capacitance C and a Mott memristor;

the transistor is used for outputting an antenna control signal to charge the capacitor according to the input tactile information;

the capacitor is used for controlling the conduction of the Mott memristor according to the voltage value during charging;

and the Mott memristor is used for outputting a pulse signal according to resistance state change.

8. The piezoresistive tactile sensing unit according to claim 1 or 7, wherein the pulse encoder circuit comprises a transistor, a capacitor C, and a resistor R₅And a Mott memristor;

the grid electrode of the transistor is connected with the output end of the front-end conditioning circuit, the source electrode of the transistor is connected with one end of a capacitor C and one end of a Mott memristor respectively, the other end of the capacitor C is grounded, and the other end of the Mott memristor is connected with a resistor R₅Is connected to a resistor R₅The other end of the transistor is grounded, and the drain electrode of the transistor is connected with a power supply.

Technical Field

The invention relates to the technical field of flexible electronic touch sensors, in particular to a piezoresistive touch sensing unit for nerve form output.

Background

In the face of rapid popularization of artificial intelligence and increasing requirements for human-computer interaction, the touch sensing technology has important application prospects in the fields of bionic robots, medical instruments and the like as an important window for interaction of mechanical equipment and an external environment. The piezoresistive tactile sensor takes the resistance as a sensitive parameter, has the advantages of simple structure, good linearity, mature process and the like, and is widely applied to tactile sensing.

The tactile sensing units are integrated in an array mode through a planar process, so that the spatial distribution information of the tactile sense is obtained, and the method is an important strategy for improving the judgment capability of the tactile sense. However, due to the limitation of factors such as data acquisition speed and circuit calculation resources, the size of the array of the touch sensing units is greatly limited, and the improvement of the touch sensing judgment capability of the touch sensors is greatly limited.

Disclosure of Invention

Aiming at the problem that the touch sensing judgment capability of the existing touch sensor is limited, the invention provides a piezoresistive touch sensing unit for neural form output, which realizes the improvement of the touch sensing judgment capability of the touch sensor.

The invention is realized by the following technical scheme:

a piezoresistive tactile sensing unit for nerve form output comprises a piezoresistive bridge circuit, a front end conditioning circuit and a pulse encoder circuit which are sequentially connected;

the piezoresistive bridge circuit is used for acquiring tactile information and outputting the tactile information to the front-end conditioning circuit;

the front-end conditioning circuit is used for calculating the input tactile information and outputting the calculated tactile information to the pulse encoder circuit;

and the pulse coding circuit is used for converting the input tactile information into a tactile pulse sequence signal in a neural form and outputting the signal.

Preferably, the piezoresistive bridge circuit comprises a wheatstone bridge and a voltage stabilizing source connected with the wheatstone bridge, and the piezoresistors in the wheatstone bridge are tactile sensors.

Preferably, the wheatstone bridge is a single-arm working bridge, a double-arm working bridge or a full-arm working bridge.

Preferably, the wheatstone bridge comprises four resistors, wherein at least one of the four resistors is a voltage dependent resistor, and the rest of the four resistors are fixed resistors;

resistance R_aResistance R_bResistance R_cAnd a resistance R_dSequentially connecting the head and the tail;

the resistor R_aAnd a resistance R_bAnd a resistor R, and_{d and}resistance R_cThe connecting end of the constant current source is connected with the anode and the cathode of the constant current source;

the resistor R_aAnd a resistance R_dThe connecting end is an output end V₁Resistance R_cAnd a resistance R_bThe connecting end is an output end V₂。

Preferably, the front-end conditioning circuit comprises 3 operational amplifiers and 4 resistors;

operational amplifier A₁And operational amplifier A₂The input end of the operational amplifier A is respectively connected with the output end of the piezoresistive bridge circuit and is used as a voltage follower to realize front and rear stage isolation, and the operational amplifier A₁And operational amplifier A₂Output terminal of and operational amplifier A₃The input ends of the two-way valve are connected;

the operational amplifier A₃And 4 resistors constitute a subtraction circuit for performing subtraction operation on the tactile information and outputting the tactile information.

Preferably, the front-end conditioning circuit comprises 3 operational amplifiers and 4 resistors;

operational amplifier A₁Output end V of the positive phase and piezoresistive bridge circuit₁Connected to the inverting and output terminals of the operational amplifier A1 and the resistor R₁Is connected to a resistor R₁The other end and a resistor R₄And an operational amplifier A₃Is connected in anti-phase, resistor R₄And the other end of (1) and an operational amplifier A₃Is connected with the output end of the power supply.

Operational amplifier A₂Output end V of the positive phase and piezoresistive bridge circuit₂Connected to the inverting and output terminals of the operational amplifier A2 and the resistor R₂Is connected to a resistor R₂Another terminal resistance R₃And an operational amplifier A₃Is in the positive phase connection, operational amplifier A₃And the other end of the same is grounded.

Preferably, the pulse encoder circuit comprises a transistor, a capacitor C and a Mott memristor;

the transistor is used for outputting an antenna control signal to charge the capacitor according to the input tactile information;

the capacitor is used for controlling the conduction of the Mott memristor according to the voltage value during charging;

and the Mott memristor is used for outputting a pulse signal according to resistance state change.

Preferably, the pulse encoder circuit comprises a transistor, a capacitor C and a resistor R₅And a Mott memristor;

the grid electrode of the transistor is connected with the output end of the front-end conditioning circuit, the source electrode of the transistor is connected with one end of a capacitor C and one end of a Mott memristor respectively, the other end of the capacitor C is grounded, and the other end of the Mott memristor is connected with a resistor R₅Is connected to a resistor R₅The other end of the transistor is grounded, and the drain electrode of the transistor is connected with a power supply.

Compared with the prior art, the invention has the following beneficial technical effects:

the piezoresistive tactile sensing unit for neural form output provided by the invention comprises a piezoresistive bridge circuit, a front end conditioning circuit and a pulse encoder circuit which are integrated in situ, when the pressing operation occurs, the resistance value of the piezoresistor changes to cause bridge unbalance, the voltages at two ends of the bridge generate difference and are further output to the pulse encoder circuit through the difference calculation by the front end conditioning circuit, and the pulse encoder circuit converts the voltage signals into pulse signals to be output, so that the neural form tactile information is output.

The piezoresistive bridge circuit arranges the output of the piezoresistive tactile sensor into a voltage signal related to delta RR, changes the characteristics that a resistance signal is difficult to measure and has no driving capability, and meanwhile, the piezoresistive bridge circuit has the advantages of high measurement precision, high sensitivity, simple circuit and the like, and can realize the characteristic that no output is generated under the condition of no pressing by matching with a conditioning circuit, thereby reducing the static power consumption of the encoder circuit.

The transistor output current IDS in the pulse encoder is used as a tactile signal and is converted into a pulse signal with the frequency related to the IDS size in situ by a Mott memristor and a capacitor, and therefore the tactile information output of the nerve morphology is achieved.

The Mott pulse encoder outputs the haptic signal in a pulse train similar in character to the pulse signal released by the biological neuron conductive ion channel switch, hence the name neuromorphic output. The neural morphology output avoids ADC sampling conversion circuit and sampling frequency limitation thereof, thereby ensuring time domain resolution of the touch signal, greatly reducing sensing data volume, facilitating array scale expansion and ensuring that space resolution is improved greatly. The touch sensor with pulse sequence output has biocompatibility, is an urgent need for developing a neural morphology calculation system based on a pulse neural network (SNN) from a short term, and is also a demand for research of biological neuroscience and intelligent brain-computer interfaces from a long term.

Drawings

FIG. 1 is a schematic diagram of a piezoresistive tactile sensing unit for neuromorphic output according to the present invention;

FIG. 2 is a circuit diagram of a piezoresistive bridge according to the present invention;

FIG. 3 is a front-end conditioning circuit of the present invention;

FIG. 4 is a pulse encoder circuit of the present invention;

FIG. 5 shows the simulation results of the pulse coder circuit according to the present invention;

the graph a is a hysteresis curve graph of the Mott memristor, the graph b is a charge-discharge current graph of the capacitor C, the graph C is an SA pulse signal graph, the graph d is a graph of the relationship between the SA pulse signal frequency and the maximum charge current, and the graph e is a graph of the relationship between the SA pulse signal frequency and the capacitor C.

Detailed Description

The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.

Referring to fig. 1, a piezoresistive tactile sensing unit for neuromorphic output includes a piezoresistive bridge circuit, a front-end conditioning circuit, and a pulse encoder circuit.

The piezoresistive bridge circuit is used for acquiring tactile information and outputting the tactile information to the front-end conditioning circuit; the piezoresistive bridge circuit consists of a Wheatstone bridge formed by resistors and a voltage stabilizing source, and the piezoresistors in the Wheatstone bridge are used as tactile sensors.

The front-end conditioning circuit is used for calculating the input tactile information and outputting the calculated tactile information to the pulse encoder; the front-end conditioning circuit consists of an operational amplifier and a resistor and carries out signal front-end processing according to the negative feedback operational amplifier virtual short virtual break principle.

A pulse encoder circuit for converting the input tactile information into a tactile pulse sequence signal in a neural form and outputting the signal; the pulse encoder circuit is composed of a transistor, a capacitor, a resistor and a Mott memristor, the transistor is connected with the output of the front-end conditioning circuit and controls the pulse encoder to work, and the Mott memristor is a neural mimicry device and is used for simulating a neuron ion channel switch and is a core element for realizing neural form touch signal output.

When pressing occurs, the resistance values of four arms of the bridge are not equal due to the fluctuation of the resistance values of the piezoresistors of the piezoresistor bridge circuit, so that the bridge is unbalanced, the voltages at two ends of the bridge of the piezoresistor bridge circuit are changed and input into the front-end conditioning circuit, signals are subjected to isolation transmission and then output to the pulse encoder circuit through the difference calculation of the conditioning circuit, and as the grid electrode of the transistor in the pulse encoder circuit is directly connected with the output of the conditioning circuit, the working state of the transistor is controlled by the resistance value of the piezoresistor, and the transistor outputs a current I_DSAs a touch control signal, the capacitor is charged, and the Mott memristor has a resistance change characteristic, namely can change between a high resistance state and a low resistance state under a specific pressure difference condition, so that the channel current I of the transistor_DSIn the process of charging the capacitor C, when the voltage of the upper end of the capacitor rises to reach a certain threshold value, the Mott memristor can be turned on, at the moment, the circuit finishes one-time discharging, namely a pulse output is generated, then the Mott memristor is turned off, and I_DSThe capacitor C is charged again until the Mott memristor is conducted again; i is_DSThe size is determined by the contact pressure, and the pulse frequency is changed by determining the charging and discharging speed, so that the neural shape of the tactile signal is realizedAnd (5) encoding the state pulse.

Referring to fig. 2, the piezoresistive bridge circuit is composed of 4 resistors and 1 voltage-stabilizing source, at least one of the 4 resistors is a piezoresistor, the rest are fixed resistors, the 4 resistors form a wheatstone bridge, the voltage-stabilizing source is connected with the wheatstone bridge, and the wheatstone bridge outputs a voltage V₁And V₂。

The 4 resistors are respectively a resistor R_aResistance R_bResistance R_cAnd a resistance R_dResistance R_aOne terminal of (1) and a resistor R_bIs connected to a resistor R_bAnother terminal of (1) and a resistor R_cIs connected to a resistor R_cAnother terminal of (1) and a resistor R_dIs connected to a resistor R_dAnother terminal of (1) and a resistor R_aThe other end of the connecting rod is connected.

Resistance R_aAnd a resistance R_bAnd a resistor R, and_dand a resistance R_cThe connecting end is connected with the anode and the cathode of the constant current source, and the resistor R_aAnd a resistance R_dThe connecting end is an output end V₁Resistance R_cAnd a resistance R_bThe connecting end is an output end V₂。

The bridge output voltage V is listed in FIG. 1₁And V₂Can be represented by formula (1), wherein V_briA regulated supply voltage.

Referring to FIG. 3, the front-end conditioning circuit comprises 3 operational amplifiers and 4 resistors, and the operational amplifier A₁And operational amplifier A₂Connected with the output end of the piezoresistive bridge circuit to serve as a voltage follower to realize front-stage and back-stage isolation, and an operational amplifier A₃And 4 resistors form a subtraction circuit to realize bridge output operation.

Operational amplifier A₁Output end V of the positive phase and piezoresistive bridge circuit₁Connected, operational amplifier A₁And the inverting sum output terminal of (3) and the resistor R₁Is connected to a resistor R₁The other end and a resistor R₄And an operational amplifier A₃Is connected in anti-phase, resistor R₄And the other end of (1) and an operational amplifier A₃Is connected with the output end of the power supply.

Operational amplifier A₂Output end V of the positive phase and piezoresistive bridge circuit₂Connected, operational amplifier A₂And the inverting sum output terminal of (3) and the resistor R₂Is connected to a resistor R₂Another terminal resistance R₃And an operational amplifier A₃Is in the positive phase connection, operational amplifier A₃And the other end of the same is grounded.

It should be noted that the resistances listed in FIG. 1 should satisfy R₁＝R₄，R₂＝R₃The output of the front-end conditioning circuit is shown as the formula (2), and the bridge arm ratio of the bridge meets the requirement under the condition of no pressingTime-bridge balancing, i.e. conditioning the output voltage V of the circuit₃＝0。

The resistance in the piezoresistive bridge circuit provided by the embodiment of the invention has various combination modes, and the bridge has different working characteristics under different combinations.