KR102351071B1 - Sensor Module which includes textile strain sensor - Google Patents

Abstract

A sensor module according to an embodiment disclosed in this document includes: a fiber strain sensor whose resistance value changes according to a change in length; a first conversion circuit for converting the resistance value into a voltage value; an amplification circuit for amplifying the voltage value according to a specified amplification factor; a second conversion circuit for outputting a sensed voltage by digitally converting the amplified voltage value; an adaptive filter capable of determining an amplification factor of the amplification circuit; and a processor, wherein the processor determines an amplification factor corresponding to the individual characteristics of the fiber strain sensor through the adaptive filter, designates the determined amplification factor as an amplification factor of the amplification circuit, and is amplified by the specified amplification factor. A specified value may be calculated based on the sensed voltage.

Description

Sensor Module which includes textile strain sensor}

Various embodiments disclosed herein relate to a fiber strain sensor.

Bio-signal sensing technology is being actively applied in the field of wearable technology for the convenience and health of life. These wearable technologies are being developed mainly for accessories, clothes, and patches that can be worn on the human body for miniaturization of devices, wearability, and diversity of functions.

As an example of wearable technology, when a structure (eg, length) is deformed due to an external force, the strain sensor uses a principle in which a resistance value is changed due to the deformation. Using this principle, data on movement, muscle strength, or respiration of the human body may be measured based on a change in the resistance value of the strain sensor. For example, a textile strain sensor may be applied to a fitness article or clothing, and may be used to measure a user's exercise accuracy based on a change in length of the textile strain sensor. The lightweight, flexible and stretchable fiber strain sensor can be worn for a long time without any inconvenience to the user and continuously collect data such as breathing and motion.

However, since the fiber strain sensor is a sensor structure woven in the same way, the resistance value according to the change in length may be different. Accordingly, the electronic device to which the conventional fiber strain sensor is applied may measure an average value of length changes of a plurality of fiber strain sensors, and may check motion accuracy based on the average value.

Various embodiments disclosed in this document may provide a sensor module capable of correcting individual characteristic errors of the fiber strain sensor.

A sensor module according to an embodiment disclosed in this document includes: a fiber strain sensor whose resistance value changes according to a change in length; a first conversion circuit for converting the resistance value into a voltage value; an amplification circuit for amplifying the voltage value according to a specified amplification factor; a second conversion circuit for outputting a sensed voltage by digitally converting the amplified voltage value; an adaptive filter capable of determining an amplification factor of the amplification circuit; and a processor, wherein the processor determines an amplification factor corresponding to the individual characteristics of the fiber strain sensor through the adaptive filter, designates the determined amplification factor as an amplification factor of the amplification circuit, and is amplified by the specified amplification factor. A specified value may be calculated based on the sensed voltage.

In addition, the sensor module according to an embodiment disclosed in this document, a fiber strain sensor in which a resistance value changes according to a change in length; a first conversion circuit for converting the resistance value into a voltage value; an amplification circuit for amplifying the voltage value according to a specified amplification factor; a second conversion circuit for outputting a sensed voltage by digitally converting the amplified voltage value; an adaptive filter capable of determining an amplification factor of the amplification circuit; and a processor, wherein the processor determines an amplification factor corresponding to an individual characteristic of the fiber strain sensor through the adaptive filter, wherein the individual characteristic includes an initial resistance value, a maximum length, and a change in length of the fiber strain sensor. may include a resistance change rate according to , designating the determined amplification factor as an amplification factor of the amplification circuit, and calculating a specified value based on the sensing voltage amplified by the specified amplification factor.

According to various embodiments disclosed in this document, it is possible to correct the individual characteristic error of the fiber strain sensor. In addition, various effects directly or indirectly identified through this document may be provided.

1 shows an example of a sensor module according to an embodiment.
2 shows an initial resistance value error of a fiber strain sensor according to an embodiment.
3 illustrates a resistance change rate error according to a change in length of a fiber strain sensor according to an embodiment.
4 shows a maximum length error of a fiber strain sensor according to an embodiment.
5 shows the total error of fiber strain sensors according to an embodiment.
6 is a block diagram of a sensor module according to an embodiment.
7 shows an adaptive filter according to an embodiment.
In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar components.

1 shows an example of a sensor module according to an embodiment.

Referring to FIG. 1 , a sensor module 10 according to an embodiment may include a fiber strain sensor 110 , a first conversion circuit 120 , a memory 140 , and a processor 130 .

The fiber strain sensor 110 may be a type of variable resistor whose resistance value changes according to a change in length. The fiber strain sensor 110 may be provided in a portion of clothing that is connected to the user's joint portion (eg, a body portion in which an angle change occurs) in clothing worn by the user. The joint region may include, for example, at least one of an elbow, a hip, and a knee.

The first conversion circuit 120 may output a voltage value that changes according to the resistance value of the fiber strain sensor 110 . For example, the first conversion circuit 120 may be a Wheatstone bridge circuit in which four resistors are symmetrically connected. _{The resistance (R x} ) of one of the Wheatstone bridge circuits may be the fiber strain sensor 110 . The Wheatstone bridge circuit is between the first resistor (R ₁ ) and the second resistor (R ₂ ) and between the third resistor (R ₃ ) and the fiber strain sensor 110 When the input voltage (V ₀ ) is supplied, the first _{An output voltage (V G} ) may be output between the first resistor (R ₁ ) and the third resistor (R ₃ ) and between the second resistor (R ₂ ) and the fiber strain sensor 110 . The input voltage may be a DC voltage of a certain magnitude, and the output voltage may be an analog voltage that varies according to a resistance value of the fiber strain sensor 110 . The output voltage is the voltage between the first resistor R1 and the second resistor R2 (hereinafter referred to as “first voltage”) and the voltage between the third resistor R3 and the fiber strain sensor 110 ( Hereinafter, it corresponds to the potential difference of the "second voltage"), and may be smaller than the input voltage due to respective resistances.

The memory 140 may store a mapping table including joint angles corresponding to the sensed voltage. The memory 140 may include a volatile memory or a non-volatile memory.

The processor 130 may calculate the resistance value based on the relationship between the _{output voltage V G and the resistance value.} The processor 130 may check the user's joint angle corresponding to the calculated resistance value based on the mapping table stored in the memory 140 . The mapping table may include sensing voltages and joint angles corresponding to each other. For example, the mapping table may include sensing voltages corresponding to a plurality of joint angles. In this case, the processor 130 may calculate the user's joint angle (hereinafter, may be referred to as a "bending angle") based on .

The sensor module 10 is an amplifier circuit that amplifies the voltage value output by the first conversion circuit 120 between the processor 130 and the first conversion circuit 120 and (analog) digitally converts the amplified voltage value A second conversion circuit may be further included. In addition, the sensor module 10 may further include a communication circuit for transmitting the calculated joint angle to an external electronic device. Such an additional configuration will be described later.

The fiber strain sensor 110 according to the above-described embodiment may have an error for each sensor due to fiber characteristics. For example, the fiber strain sensor 110 may have errors in the initial resistance value, the resistance change rate according to the length change, and the maximum length due to the characteristics of the fiber. Such an error may lead to an error in the user's joint angle calculated by the sensor module 10 .

2 shows an initial resistance value error of a fiber strain sensor according to an embodiment. In FIG. 2 , the maximum and the minimum are the maximum and minimum voltage values convertible in the first conversion circuit 120 , respectively, and the reference point may be the center voltage value of the first conversion circuit 120 .

2, as shown in the waveform 210, the initial resistance value of the fiber strain sensor 110 is set so that the output voltage of the first conversion circuit 120 is changed based on the center voltage value of the first conversion circuit 120 It may be ideal to be However, the fiber strain sensor 110 may have an error in the initial resistance value due to the characteristics of the fiber, and this error may affect the output voltage. For example, as in the 220 waveform, when the initial resistance value of the fiber strain sensor 110 is too large (or more than the first threshold resistance), the output voltage exceeds the reference point of the first conversion circuit 120 and , in this case, the output voltage may be clamped as in the A region. For another example, as in the 230 waveform, when the initial resistance of the fiber strain sensor 110 is too small (or less than the second threshold resistance (<first threshold resistance)), the output voltage is applied to the first conversion circuit ( 120) below the baseline. In this case, the output voltage may be cut as in the B region. As such, an error in the initial resistance value of the fiber strain sensor 110 may cause an error in the output voltage conversion by the first conversion circuit 120, and this error may cause an error in the joint angle calculation.

3 illustrates a resistance change rate error according to a change in length of a fiber strain sensor according to an embodiment.

Referring to FIG. 3 , the fiber strain sensors may have an error in the resistance change rate according to the length change even if the initial resistance value and the maximum length are the same. For example, for the same length change (eg, +3 cm), the resistance change rate 310 of the first fiber strain sensor and the resistance change rate 320 of the second fiber strain sensor may have a difference e ₂ . Due to this difference (e ₂ ), the output voltage waveform 330 of the first conversion circuit 120 according to the resistance change of the first fiber strain sensor and the first conversion circuit 120 corresponding to the second fiber strain sensor The output voltage waveform 340 may be different. Such a difference may cause an error in calculating the joint angle based on the output voltage.

4 shows a maximum length error of a fiber strain sensor according to an embodiment.

Referring to FIG. 4 , in the fiber strain sensors, even if the initial resistance value and the resistance change rate according to the length change are the same, there may be an error in the maximum deformable length. The maximum length may affect the maximum and minimum (Vpp) of the output voltage. For example, the maximum length of the first fiber strain sensor is the first length (S0_max) and the maximum length of the second strain sensor is the second length (S1_max), and there may be a _{mutual difference (e 3 ).} In this case, Vpp of the first fiber strain sensor may be a first value 410 and Vpp of the second fiber strain sensor may be a second value 420 . However, a fiber strain sensor having an excessively long maximum length such as the second fiber strain sensor may exceed the maximum voltage and minimum voltage values of the first conversion circuit 120 . In this case, distortion may occur in the output voltage, and such distortion may cause an error in the joint angle calculation.

5 shows the total error of fiber strain sensors according to an embodiment.

Referring to FIG. 5 , the error range of the fiber strain sensor 110 may be wide due to the three influences (initial resistance value, resistance change rate according to length change, and maximum length). As the error ranges (e ₁ , e ₂ , e ₃ ) are smaller, the accuracy of the joint angle calculation using the fiber strain sensor 110 may be higher.

6 shows a configuration diagram of a sensor module according to an embodiment, and FIG. 7 shows an adaptive filter according to an embodiment.

Referring to FIG. 6 , the sensor module 60 according to an embodiment includes a communication circuit 610 , a memory 620 , a fiber strain sensor 630 (eg, the fiber strain sensor 110 of FIG. 1 ), a first It may include a conversion circuit 660 (eg, the first conversion circuit 120 of FIG. 1 ), an amplifier circuit 650 , a second conversion circuit 660 , an adaptive filter 670 , and a processor 680 . . In an embodiment, the sensor module 60 may omit some components or further include additional components. In addition, some of the components of the sensor module 60 are combined to form a single entity, and the functions of the components prior to the combination may be performed identically. 6 shows, for example, that the sensor module 60 includes one fiber strain sensor 630 . However, the sensor module 60 may include a plurality of fiber strain sensors. In this case, the first conversion circuit 660 , the amplifier circuit 650 , and the second conversion circuit 660 are also provided to correspond to the number of the plurality of fiber strain sensors, and a digital output corresponding to the resistance change of each fiber strain sensor. voltage values can be generated.

The communication circuit 610 may support establishment of a communication channel or wireless communication channel between the sensor module 60 and another device (eg, the external sensor module 60 ), and performing communication through the established communication channel. The communication channel may be, for example, a wireless communication channel such as NFC, Bluetooth and WiFi.

The memory 620 may store various data used by at least one component (eg, the processor 680 ) of the sensor module 60 . Data may include, for example, input data or output data for software and related instructions. For example, the memory 620 may store at least one instruction for setting an amplification factor capable of correcting an error of the fiber strain sensor 630 . As another example, the memory 620 may store a mapping table including joint angles corresponding to the sensed voltage. The memory 620 may include a volatile memory or a non-volatile memory.

The fiber strain sensor 630 may be a type of variable resistor whose resistance value changes according to a change in length. The fiber strain sensor 630 may be provided in a portion of clothing that is connected to the user's joint portion (eg, a body portion in which an angle change occurs) in clothing worn by the user.

The first conversion circuit 660 may output a voltage value corresponding to the resistance value of the fiber strain sensor 630 . For example, the first conversion circuit 660 may be a Wheatstone bridge circuit in which four resistors are symmetrically connected. _{A resistor (R x in} FIG. 1 ) of one of the Wheatstone bridge circuits may be a fiber strain sensor 630 .

The amplification circuit 650 may amplify the output voltage of the first conversion circuit 660 according to a specified amplification factor. The specified amplification factor may be an amplification factor determined through the adaptive filter 670 based on an initial resistance value of the fiber strain sensor 630 , a resistance change rate according to a change in length, and a maximum length.

The second conversion circuit 660 outputs a voltage (hereinafter, referred to as “sensing voltage”) having a magnitude corresponding to the resistance value of the fiber strain sensor 630 as it digitally converts the voltage amplified by the amplifier circuit 650 . can do.

The processor 680 may control at least one other component (eg, a hardware or software component) of the sensor module 60 by executing at least one instruction, and may perform various data processing or operations. . The processor 680 may include, for example, a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor, an application processor, an application specific integrated circuit (ASIC), or field programmable gate arrays (FPGA). )), and may have a plurality of cores.

The processor 680 may receive the sensing voltage output by the second conversion circuit 660 and calculate the user's joint angle corresponding to the sensing voltage based on the mapping table.

The processor 680 may determine an amplification factor of the amplification circuit 650 corresponding to individual characteristics of the fiber strain sensor 630 by using the adaptive filter 670 . The individual characteristics may include at least one of an initial resistance value of the fiber strain sensor 630, a maximum length, and a resistance change rate according to a change in length. The processor 680 may calculate the degree to which the initial resistance value for each fiber strain sensor 630, the maximum length, and the amplification factor according to the resistance change rate according to the length change affect the angle change. The processor 680 may determine the amplification factor of the amplification circuit 650 to reduce the calculated degree using the adaptive filter 670 . Thereafter, the processor 680 may improve the error due to the individual characteristics of the fiber strain sensor 630 by setting the amplification factor determined for the amplification factor of the amplification circuit 650 .

Referring to FIG. 7 , the adaptive filter 670 may include a first adaptive filter related to an initial resistance value and a maximum length and a second adaptive filter related to a resistance change rate according to a change in length. For example, the processor 680 may calculate an amplification factor for reducing the initial resistance value and the maximum length error of the fiber strain sensor 630 using the first adaptive filter. In more detail, the processor 680 is configured to amplify the reference sensing voltage y(n), the output voltage x(n) according to the initial resistance value and the maximum length by the filter coefficient (amplification factor), and the sensing voltage y (n)) can be calculated. The output voltage corresponding to the initial resistance value and the maximum length may be input through the communication circuit 610 and set in the adaptive filter 670 by the processor 680 . The processor 680 minimizes the difference (e(n)=d(n)-y(n)) between the reference sensing voltage and the sensing voltage using least mean square (LMS) while adjusting the filter coefficients of the first adaptive filter. The filter coefficient (amplification factor) of the available FIR filter can be calculated. As another example, the processor 680 may calculate an amplification factor for reducing a resistance change rate according to a change in the length of the fiber strain sensor 630 using the second adaptive filter. In more detail, the processor 680 may calculate the sensing voltage by amplifying the reference sensing voltage y(n) and the output voltage corresponding to the resistance change rate with a filter coefficient (amplification factor). The processor 680 is a filter coefficient (amplification factor) of the FIR filter capable of minimizing the difference between the reference sensing voltage and the sensing voltage (e(n)=d(n)-y(n)) using least mean square (LMS). ) can be calculated. The output voltage corresponding to the resistance change rate may be input through the communication circuit 610 and may be set in the adaptive filter 670 by the processor 680 . In this regard, the processor 680 may determine a filter coefficient (amplification factor) that can most reduce an error obtained by summing the error of the first adaptive filter and the error of the second adaptive filter using the LMS.

When the user's joint angle is calculated through the fiber strain sensor 630 , the processor 680 may transmit the calculated joint angle to the external sensor module 60 through the communication circuit 610 .

According to the above-described embodiment, the sensor module 60 uses the adaptive filter 670 to determine an amplification factor capable of correcting individual characteristic errors of the fiber strain sensor 630, and based on the determined amplification factor, the fiber strain sensor ( 630) can be supported to keep the error to a certain degree uniform.

The various embodiments of this document and terms used therein are not intended to limit the technical features described in this document to specific embodiments, but it should be understood to include various modifications, equivalents, or substitutions of the embodiments. In connection with the description of the drawings, like reference numerals may be used for similar or related components. The singular form of the noun corresponding to the item may include one or more of the item, unless the relevant context clearly dictates otherwise. As used herein, “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C” and “A; Each of the phrases such as "at least one of B, or C" may include any one of, or all possible combinations of, items listed together in the corresponding one of the phrases. Terms such as “first”, “second”, or “first” or “second” may simply be used to distinguish the component from other components in question, and may refer to components in other aspects (e.g., importance or order) is not limited. that one (eg first) component is “coupled” or “connected” to another (eg, second) component with or without the terms “functionally” or “communicatively” When referenced, it means that one component can be connected to the other component directly (eg by wire), wirelessly, or through a third component.

As used herein, the terms “module,” “part,” and “means” may include units implemented in hardware, software, or firmware, and include terms such as, for example, logic, logical blocks, parts, or circuits; They can be used interchangeably. A module may be an integrally formed part or a minimum unit or a part of the part that performs one or more functions. For example, according to an embodiment, the module may be implemented in the form of an application-specific integrated circuit (ASIC).

Various embodiments of the present document include one or more stored in a storage medium (eg, internal memory or external memory) (memory 620 ) readable by a machine (eg, sensor module 60 ). It may be implemented as software (eg, a program) including instructions. For example, a processor (eg, processor 680 ) of a device (eg, sensor module 60 ) may call at least one of one or more instructions stored from a storage medium and execute it. to be operated to perform at least one function according to the called at least one instruction.The one or more instructions may include a code generated by a compiler or a code that can be executed by an interpreter. The readable storage medium may be provided in the form of a non-transitory storage medium, where 'non-transitory' is a device in which the storage medium is tangible, and a signal (eg, electromagnetic wave) ), and this term does not distinguish between a case in which data is semi-permanently stored in a storage medium and a case in which data is temporarily stored.

According to an embodiment, the method according to various embodiments disclosed in this document may be included and provided in a computer program product. Computer program products may be traded between sellers and buyers as commodities. The computer program product is distributed in the form of a machine-readable storage medium (eg compact disc read only memory (CD-ROM)), or via an application store (eg Play Store ^TM ) or on two user devices ( It can be distributed (eg downloaded or uploaded) directly or online between smartphones (eg: smartphones). In the case of online distribution, at least a part of the computer program product may be temporarily stored or temporarily created in a machine-readable storage medium such as a memory of a server of a manufacturer, a server of an application store, or a relay server.

According to various embodiments, each component (eg, a module or a program) of the above-described components may include a singular or a plurality of entities. According to various embodiments, one or more components or operations among the above-described corresponding components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (eg, a module or a program) may be integrated into one component. In this case, the integrated component may perform one or more functions of each component of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to the integration. . According to various embodiments, operations performed by a module, program, or other component are executed sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations are executed in a different order, or omitted. or one or more other operations may be added.

Claims (8)

In the sensor module,
A fiber strain sensor that is provided in the user's joint area in the clothing worn by the user and the resistance value changes according to the change in length;
a first conversion circuit for converting the resistance value into a voltage value;
an amplification circuit for amplifying the voltage value according to a specified amplification factor;
a second conversion circuit for outputting a sensed voltage by digitally converting the amplified voltage value;
an adaptive filter capable of determining an amplification factor of the amplification circuit; and
A memory for storing a mapping table in which a relationship between a sensed voltage and a joint angle is defined, and a processor for calculating a joint angle corresponding to the sensed voltage amplified according to the specified amplification factor based on the mapping table, the processor Is,
determining an amplification factor corresponding to individual characteristics of the fiber strain sensor through the adaptive filter;
Designating the determined amplification factor as an amplification factor of the amplification circuit,
Calculating a specified value based on the sensed voltage amplified by the specified amplification factor,
The adaptive filter is
a first adaptive filter related to an initial resistance value and a maximum length of the fiber strain sensor; and
A second adaptive filter related to a resistance change rate according to a change in the length of the fiber strain sensor,
The processor is
In order to minimize the error range of the fiber strain sensors based on the error of the initial resistance value of the fiber strain sensor, the error of the resistance change rate according to the length change, and the error of the maximum length between the plurality of fiber strain sensors,
A sensing voltage obtained by amplifying the reference sensing voltage, the initial resistance value, and the output voltage according to the maximum length at an amplification factor according to the filter coefficient of the first adaptive filter is calculated, and while the filter coefficient of the first adaptive filter is adjusted, LMS ( Least Mean Square) to determine the filter coefficient of the FIR filter capable of minimizing the difference between the sensing voltage and the reference sensing voltage,
Calculating a sensing voltage obtained by amplifying a reference sensing voltage and an output voltage according to the resistance change rate by an amplification factor according to the filter coefficient of the second adaptive filter, and adjusting the filter coefficient of the second adaptive filter using LMS determine the FIR filter coefficient that can minimize the difference between the and the reference sensing voltage,
The amplification factor is determined to reduce a difference between the sensed voltage and a reference sensed voltage based on the filter coefficients of the first adaptive filter and the filter coefficients of the second adaptive filter, determining an amplification factor that minimizes an error obtained by summing the error and the error of the second adaptive filter;
Based on the determined amplification factor to correct the individual characteristic error of the individual fiber strain sensor, the sensor module. delete delete delete delete delete The method according to claim 1,
Further comprising communication circuitry, the processor comprising:
A sensor module for transmitting the joint angle to an external electronic device through a communication circuit. delete

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