CN110207865B - Plantar pressure sensor for correcting temperature influence and corresponding correction method - Google Patents
Plantar pressure sensor for correcting temperature influence and corresponding correction method Download PDFInfo
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Abstract
The invention discloses a plantar pressure sensor for correcting temperature influence, which comprises a signal acquisition part and a circuit part, wherein the signal acquisition part is sequentially provided with a first device protection layer, a first electrode layer, a piezoelectric film layer, a ground electrode layer and a second device protection layer from top to bottom; the first electrode layer, the piezoelectric film layer and the ground electrode layer form a pressure detection unit, and the first electrode layer is used as a temperature detection unit; the circuit part comprises a front-end circuit and a back-end circuit; the front-end circuit comprises a controller, and a control signal output end of the controller is connected with a signal input end of the first electrode layer; the back-end circuit adopts one of the first back-end circuit or the second back-end circuit. The invention also discloses a method for correcting the plantar pressure affected by temperature. The invention can measure pressure and temperature at the same time, thereby correcting the piezoelectric constant change caused by temperature change, greatly improving the accuracy of the sensor, making up the defects of the existing products, and being suitable for the technical field of medical equipment.
Description
Technical Field
The invention belongs to the technical field of medical equipment, and relates to a plantar pressure sensor for detecting and correcting plantar pressure, in particular to a plantar pressure sensor for correcting temperature influence and a corresponding correction method.
Background
Along with the improvement of living standard, human health becomes an important issue of concern.
The distribution of plantar pressure of the human body can reflect the changes of the functions and the body posture of the lower limbs. The physiological and pathological parameters of the human body under different movement states can be obtained by testing and analyzing the pressure parameters of each point of the sole, which has important significance for researches such as clinical disease diagnosis, postoperative effect evaluation, rehabilitation degree evaluation and the like.
Currently, most pressure sensors adopt piezoelectric and piezoresistive materials, and the measured value is greatly influenced by temperature change. Most of the traditional in-shoe pressure sensors can only measure pressure and cannot correct the change of foot temperature, so that the defects of great influence on temperature and low accuracy are caused.
Disclosure of Invention
The invention aims to provide a plantar pressure sensor for correcting temperature influence, which can measure plantar temperature and pressure change simultaneously and correct measured results.
It is a further object of the present invention to provide a method of correcting the plantar pressure of a temperature-affected foot.
The technical scheme adopted by the invention for realizing the purposes is as follows:
a plantar pressure sensor for correcting temperature influence comprises a signal acquisition part and a circuit part;
first) signal acquisition part
The signal acquisition part is sequentially provided with a first device protection layer, a first electrode layer, a piezoelectric film layer, a ground electrode layer and a second device protection layer from top to bottom;
the first electrode layer, the piezoelectric film layer and the ground electrode layer form a pressure detection unit, and the first electrode layer is used as a temperature detection unit;
two) circuit portion
The circuit part comprises a front-end circuit and a back-end circuit;
the front-end circuit comprises a controller, and a control signal output end of the controller is connected with a signal input end of the first electrode layer;
the back-end circuit adopts one of a first back-end circuit or a second back-end circuit, wherein,
(1) first back-end circuit
The first back-end circuit comprises a first analog-to-digital conversion unit, a first central processing unit, communication equipment and an upper computer which are sequentially connected in series;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first analog-to-digital conversion unit;
(2) second back-end circuit
The second back-end circuit comprises a filtering unit, a second analog-to-digital conversion unit, a second central processing unit, communication equipment and an upper computer which are sequentially connected in series; the filtering unit comprises a low-pass filter and a band-pass filter which are connected in parallel, and the second analog-to-digital conversion unit comprises a first analog-to-digital converter and a second analog-to-digital converter which are connected in parallel;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the filtering unit, and the signal output end of the low-pass filter is respectively connected with the second central processing unit through the first analog-to-digital converter and the signal output end of the band-pass filter through the second analog-to-digital converter.
As a limitation: the first electrode layer comprises N (N is more than or equal to 1) small electrodes;
the front-end circuit further comprises a multiplexer;
the control signal output end of the controller is connected with the input ends of the N small electrodes included in the first electrode layer through a multiplexer;
the first back-end circuit further includes a first multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first analog-to-digital conversion unit through a first multiplexer;
the second back-end circuit further comprises a second multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the filtering unit through a second multiplexer.
A method for correcting temperature-affected plantar pressure, which is realized by the plantar pressure sensor for correcting temperature-affected plantar pressure, wherein the method is a first method or a second method when a back-end circuit adopts a first back-end circuit, the method is a first method when the back-end circuit adopts a second back-end circuit, the method is a second method,
I. method one
The method one comprises the following steps in sequence:
1. simultaneously applying a direct current signal and an alternating current signal on the first electrode layer through the controller; when the pressure applied by the detection unit changes, the surface of the piezoelectric film layer generates electric charge; when the temperature of the outer surface of the detection unit changes, the resistivity of the first electrode layer changes so as to cause the resistance to change; the detection unit outputs a direct-current analog current signal containing resistance value change information and an alternating-current analog current signal with pressure value change to the first analog-to-digital conversion unit;
2. the first analog-to-digital conversion unit converts the received mixed analog electric signal containing the direct-current analog current signal and the alternating-current analog current signal into a digital signal and outputs the digital signal to the first central processing unit;
3. the first central processing unit processes the received digital signal by utilizing a self-stored low-pass filtering algorithm to obtain a digital signal containing temperature information, and processes the received digital signal by utilizing a self-stored band-pass filtering algorithm to obtain a digital signal containing pressure information;
4. the first CPU calculates and processes the digital signal containing the temperature information to obtain a temperature change signal U T (t) outputting the pressure signal to the upper computer via the communication device, and calculating and processing the digital signal containing the pressure information by the first CPU to obtain a pressure signal U F (t) outputting the data to an upper computer through communication equipment;
5. the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally calculating a pressure correction value;
II, method II
The second method comprises the following steps in sequence:
simultaneously applying a direct current signal and an alternating current signal on the first electrode layer through the controller; when the pressure applied by the detection unit changes, the surface of the piezoelectric film layer generates electric charge; when the temperature of the outer surface of the detection unit changes, the resistivity of the first electrode layer changes so as to cause the resistance to change; the detection unit outputs a direct current analog current signal containing resistance value change information and an alternating current analog current signal with pressure value change to the filtering unit;
the filtering unit processes the received mixed analog electric signal through a low-pass filter to obtain a direct-current analog current signal with resistivity change and outputs the direct-current analog current signal to the first analog-to-digital converter, and the filtering unit processes the received mixed analog electric signal through a band-pass filter to obtain an alternating-current analog current signal and outputs the alternating-current analog current signal to the second analog-to-digital converter;
the first analog-to-digital converter converts the received direct-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit, and the second analog-to-digital converter converts the received alternating-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit;
(IV) the second CPU calculates the digital electric signal received from the first A/D converter to obtain a temperature variation signal U T (t) outputting the pressure signal to the upper computer through the communication equipment, and calculating the digital signal received from the second analog-digital converter by the second central processing unit to obtain a pressure signal U F (t) outputting the data to an upper computer through communication equipment;
(V) the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally calculating a pressure correction value;
as a limitation: (IA) in a first process, in which,
the first electrode layer comprises N (N is more than or equal to 1) small electrodes,
the front-end circuit further comprises a multiplexer;
the control signal output end of the controller is connected with the input ends of the N small electrodes included in the first electrode layer through a multiplexer;
the first back-end circuit further includes a first multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first analog-to-digital conversion unit through a first multiplexer;
the first step comprises the following steps sequentially carried out,
A. outputting a direct current signal and an alternating current signal to a plurality of modulators through a controller, and outputting the modulated direct current signal and alternating current signal to a first electrode layer through the multiplexer;
when the pressure applied to the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer changes, charges are generated on the surface of the piezoelectric film layer, and an alternating current analog current signal is further formed; when the temperature of the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer changes, the resistivity of the N (N is more than or equal to 1) th small electrode changes, so that the resistance changes, and a direct-current analog current signal is further formed; the detection unit outputs a direct current analog current signal containing resistance value change information and an alternating current analog current signal with pressure value change to the first multi-path demodulator;
B. the first multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the first analog-to-digital conversion unit;
in the fourth step, the first CPU calculates and processes the digital signal containing the temperature information to obtain a temperature change signal U near the N (N is more than or equal to 1) th small electrode T (t) outputting the pressure signals to an upper computer through communication equipment, and calculating and processing the digital signals containing the pressure information by a first central processing unit to obtain pressure signals U near an N (N is more than or equal to 1) th small electrode F (t) outputting the data to an upper computer through communication equipment;
in the fifth step, the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally calculating a pressure correction value near the Nth (N is more than or equal to 1) small electrode;
(IIA) in the second process,
the front-end circuit further comprises a multiplexer;
the control signal output end of the controller is connected with the input ends of the N small electrodes included in the first electrode layer through a multiplexer;
the second back-end circuit further comprises a second multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the filtering unit through a second multi-path demodulator;
the step (one) comprises the following steps which are sequentially carried out,
a. outputting a direct current signal and an alternating current signal to a plurality of modulators through a controller, and outputting the modulated direct current signal and alternating current signal to a first electrode layer through the multiplexer;
when the pressure applied to the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer changes, charges are generated on the surface of the piezoelectric film layer, and an alternating current analog current signal is further formed; when the temperature of the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer changes, the resistivity of the N (N is more than or equal to 1) th small electrode changes, so that the resistance changes, and a direct-current analog current signal is further formed; the detection unit outputs a direct-current analog current signal containing resistance value change information and an alternating-current analog current signal with pressure value change to the second multi-path demodulator;
b. the second multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the filtering unit;
in the step (IV), the second CPU calculates the digital electric signal received from the first analog-to-digital converter to obtain a temperature change signal U near the N (N is more than or equal to 1) th small electrode T (t) outputting the pressure signal to an upper computer through communication equipment, and calculating the digital signal received from the second analog-digital converter by a second central processing unit to obtain a pressure signal U near the N (N is more than or equal to 1) th small electrode F (t) outputting the data to an upper computer through communication equipment;
in the step (five), the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F And (t) finally calculating the pressure correction value near the Nth (N is larger than or equal to 1) small electrode.
Compared with the prior art, the technical proposal adopted by the invention has the following technical progress:
(1) The invention can measure pressure and temperature at the same time, thereby correcting the change of piezoelectric constant caused by temperature change, greatly improving the accuracy of the sensor and making up the defects of the prior product.
(2) The invention adopts passive piezoelectric material as piezoelectric film, which has the advantage of low energy consumption;
(3) The invention has simple and ingenious structure, applies two types of signals on the same electrode, and separates the two types of signals through the back-end circuit, thereby realizing simultaneous measurement of two parameters;
(4) The invention also discloses a method for detecting the pressure and the temperature by utilizing the sensor structure, and the method has simple steps, is easy to realize and has development in the plantar pressure detection field.
The invention is suitable for the technical field of medical equipment.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention.
In the drawings:
FIG. 1 is a schematic overall structure of embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of a back-end circuit according to embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of a back-end circuit of a second configuration of embodiment 1;
FIG. 4 is a signal plot of the positive stress measured at the insole region corresponding to a small electrode during a walk according to example 2 of the present invention.
In the figure: 1. the device comprises a first device protection layer 2, a first electrode layer 3, a piezoelectric film layer 4, a ground electrode layer 5 and a second device protection layer.
Detailed Description
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are presented for purposes of illustration and explanation only and are not intended to limit the present invention.
Example 1 plantar pressure insole for correcting temperature Effect
The embodiment relates to a sole pressure insole for correcting temperature influence, which comprises a signal acquisition part and a circuit part.
As shown in fig. 1 and 2, the signal acquisition part includes a first device protection layer 1, a first electrode layer 2, a piezoelectric thin film layer 3, a ground electrode layer 4, and a second device protection layer 5, which are sequentially disposed from top to bottom; the first electrode layer 2, the piezoelectric film layer 3 and the ground electrode layer 4 form a pressure detection unit, and the first electrode layer 2 serves as a temperature detection unit; the first electrode layer 2 comprises N (N is larger than or equal to 1) small electrodes distributed according to the shape of the sole of the foot.
The circuit part comprises a front-end circuit and a back-end circuit; the front-end circuit comprises a controller and a multiplexer, and the control signal output end of the controller is connected with the input ends of N small electrodes included in the first electrode layer 2 through the multiplexer; the back-end circuit comprises a first multi-path demodulator, a first analog-to-digital conversion unit, a first central processing unit, communication equipment and an upper computer which are sequentially connected in series; the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first multiplexer.
In this embodiment, the back-end circuit may further adopt a second structure, referring to fig. 3, where the second back-end circuit includes a second multi-path demodulator, a filtering unit, a second analog-to-digital conversion unit, a second central processing unit, a communication device, and an upper computer connected in series in sequence; the filtering unit comprises a low-pass filter and a band-pass filter which are connected in parallel, and the second analog-to-digital conversion unit comprises a first analog-to-digital converter and a second analog-to-digital converter which are connected in parallel; the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the second multiplexer, and the signal output end of the low-pass filter is respectively connected with the second central processing unit through the first analog-to-digital converter and the signal output end of the band-pass filter through the second analog-to-digital converter.
In this embodiment, the cut-off frequency of the low-pass filter is 10Hz, and the band of the band-pass filter is 20-1000Hz.
Example 2A method of correcting temperature-affected plantar pressure
This embodiment is implemented by using embodiment 1, and when the back-end circuit shown in fig. 2 is used, the method is a method one, which includes the following steps performed in order:
1. outputting a direct current signal and an alternating current signal to a multiplexer through a controller, wherein the multiplexer modulates the received direct current signal and alternating current signal and then outputs the modulated direct current signal and alternating current signal to the first electrode layer 2;
when the pressure applied to the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer 2 changes, charges are generated on the surface of the piezoelectric film layer 3, and an alternating current analog current signal is further formed; when the temperature of the sensor surface corresponding to the N (N is more than or equal to 1) th small electrode of the first electrode layer 2 changes, the resistivity of the N (N is more than or equal to 1) th small electrode changes so as to cause the resistance to change and further form a direct current analog current signal; the detection unit outputs a direct current analog current signal containing resistance value change information and an alternating current analog current signal with pressure value change to the first multi-path demodulator;
the first multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the first analog-to-digital conversion unit;
2. the first analog-to-digital conversion unit converts the received mixed analog electric signal containing the direct-current analog current signal and the alternating-current analog current signal into a digital signal and outputs the digital signal to the first central processing unit;
3. the first central processing unit processes the received digital signal by utilizing a self-stored low-pass filtering algorithm to obtain a digital signal containing temperature information, and processes the received digital signal by utilizing a self-stored band-pass filtering algorithm to obtain a digital signal containing pressure information;
4. the first CPU calculates and processes the digital signal containing the temperature information to obtain a temperature change signal U near the N (N is more than or equal to 1) th small electrode T (t) outputting the pressure signals to an upper computer through communication equipment, and calculating and processing the digital signals containing the pressure information by a first central processing unit to obtain pressure signals U near an N (N is more than or equal to 1) th small electrode F (t) outputting the data to an upper computer through communication equipment;
5. the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F And (t) finally calculating the pressure correction value near the Nth (N is larger than or equal to 1) small electrode.
When the back-end circuit is the back-end circuit shown in fig. 3, the method is a method two, the hardware structures of the front-end circuit and the signal acquisition part adopted by the method one and the method two are identical, the signal acquisition process is also identical, and only the differences in the structure of the back-end circuit and the signal processing exist, the method comprises the following steps in sequence:
outputting a direct current signal and an alternating current signal to a multiplexer through a controller, wherein the multiplexer modulates the received direct current signal and alternating current signal and then outputs the modulated direct current signal and alternating current signal to the first electrode layer 2;
when the pressure applied to the surface of the sensor corresponding to the Mth (M is more than or equal to 1 and less than or equal to N) small electrode of the first electrode layer 2 changes, the surface of the piezoelectric film layer 3 generates charges and further forms an alternating current analog current signal; when the temperature of the sensor surface corresponding to the Mth (M is less than or equal to 1 and less than or equal to N) small electrode of the first electrode layer 2 changes, the resistivity of the Mth (M is less than or equal to 1 and less than or equal to N) small electrode changes so as to cause the resistance to change and further form a direct current analog current signal; the detection unit outputs a direct-current analog current signal containing resistance value change information and an alternating-current analog current signal with pressure value change to the second multi-path demodulator;
the second multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the filtering unit;
the filtering unit processes the received mixed analog electric signal through a low-pass filter to obtain a direct-current analog current signal with resistivity change and outputs the direct-current analog current signal to the first analog-to-digital converter, and the filtering unit processes the received mixed analog electric signal through a band-pass filter to obtain an alternating-current analog current signal and outputs the alternating-current analog current signal to the second analog-to-digital converter;
the first analog-to-digital converter converts the received direct-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit, and the second analog-to-digital converter converts the received alternating-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit;
the second CPU calculates the digital electric signal received from the first A/D converter to obtain the temperature change signal U near the Mth (M is not less than 1 and not more than N) small electrode T (t) outputting the pressure signal to an upper computer through communication equipment, and calculating the digital signal received from the second analog-digital converter by a second central processing unit to obtain a pressure signal U near the Mth (M is not less than 1 and not more than N) small electrode F (t) outputting the data to an upper computer through communication equipment;
(V) the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F And (t) finally calculating the pressure correction value near the Mth (M is less than or equal to 1 and less than or equal to N) small electrode.
As shown in FIG. 4, a signal diagram of the positive stress measured in the insole region corresponding to a small electrode during a period of walking is shown, the positive rising stage of the signal indicates that the foot is gradually stepping on the insole, the positive stress is increased, and then the electric charge is consumed; the reverse descent phase of the signal indicates that the foot gradually leaves the ground and the normal stress is reduced. The walking period T can be obtained from the average value of the pulse peak intervals in a stable walking time, so as to obtain the step frequency f:
the resistance of the small electrode of the first electrode layer 2 has the following relationship with temperature change:
R(t)＝R 0 (1+αT em )
from the resulting low frequency/direct voltage signal, it is possible to obtain:
further, the change of temperature with time is obtained:
then, according to the piezoelectric constant-temperature (d 33 -T) relation, resulting in a corrected change d 'of the piezoelectric constant over time' 33 (t)。
According to the piezoelectric relationship q (t) =d 33 (t) x sigma (t) can obtain the relation Q between the charge density and the positive stress collected on the plane of the piezoelectric film F (t)＝d 33 (t) ×f (t), wherein σ is a positive stress perpendicular to the film plane direction.
The change with time of the plantar pressure after the temperature correction is:
in practical use, instead of only one small electrode detecting a temperature change or a pressure change, a plurality of small electrodes work together, and the whole back-end circuit processes a plurality of temperature signals and pressure signals together, and this embodiment is illustrated by the nth small electrode of the first electrode layer 2 for convenience and clarity.
Claims (3)
1. A method of modifying temperature-affected plantar pressure, characterized by: the method is realized by utilizing a plantar pressure sensor for correcting temperature influence, and the plantar pressure sensor for correcting temperature influence comprises a signal acquisition part and a circuit part;
first) signal acquisition part
The signal acquisition part is sequentially provided with a first device protection layer, a first electrode layer, a piezoelectric film layer, a ground electrode layer and a second device protection layer from top to bottom;
the first electrode layer, the piezoelectric film layer and the ground electrode layer form a pressure detection unit, and the first electrode layer is used as a temperature detection unit;
two) circuit portion
The circuit part comprises a front-end circuit and a back-end circuit;
the front-end circuit comprises a controller, and a control signal output end of the controller is connected with a signal input end of the first electrode layer;
the back-end circuit adopts one of a first back-end circuit or a second back-end circuit, wherein,
(1) first back-end circuit
The first back-end circuit comprises a first analog-to-digital conversion unit, a first central processing unit, communication equipment and an upper computer which are sequentially connected in series;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first analog-to-digital conversion unit;
(2) second back-end circuit
The second back-end circuit comprises a filtering unit, a second analog-to-digital conversion unit, a second central processing unit, communication equipment and an upper computer which are sequentially connected in series; the filtering unit comprises a low-pass filter and a band-pass filter which are connected in parallel, and the second analog-to-digital conversion unit comprises a first analog-to-digital converter and a second analog-to-digital converter which are connected in parallel;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the filtering unit, and the signal output end of the low-pass filter is respectively connected with the second central processing unit through the first analog-to-digital converter and the signal output end of the band-pass filter through the second analog-to-digital converter;
the method for correcting the plantar pressure of the temperature influence is a first method or a second method, wherein the method is the first method when the back-end circuit adopts the first back-end circuit, the method is the second method when the back-end circuit adopts the second back-end circuit,
I. method one
The method one comprises the following steps in sequence:
1. simultaneously applying a direct current signal and an alternating current signal on the first electrode layer through the controller; when the pressure applied by the detection unit changes, the surface of the piezoelectric film layer generates electric charge; when the temperature of the outer surface of the detection unit changes, the resistivity of the first electrode layer changes so as to cause the resistance to change; the detection unit outputs a direct-current analog current signal containing resistance value change information and an alternating-current analog current signal with pressure value change to the first analog-to-digital conversion unit;
2. the first analog-to-digital conversion unit converts the received mixed analog electric signal containing the direct-current analog current signal and the alternating-current analog current signal into a digital signal and outputs the digital signal to the first central processing unit;
3. the first central processing unit processes the received digital signal by utilizing a self-stored low-pass filtering algorithm to obtain a digital signal containing temperature information, and processes the received digital signal by utilizing a self-stored band-pass filtering algorithm to obtain a digital signal containing pressure information;
4. the first CPU calculates and processes the digital signal containing the temperature information to obtain a temperature change signal U T (t) outputting the pressure signal to the upper computer via the communication device, and calculating and processing the digital signal containing the pressure information by the first CPU to obtain a pressure signal U F (t) outputting the data to an upper computer through communication equipment;
5. the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally calculating a pressure correction value;
II, method II
The second method comprises the following steps in sequence:
simultaneously applying a direct current signal and an alternating current signal on the first electrode layer through the controller; when the pressure applied by the detection unit changes, the surface of the piezoelectric film layer generates electric charge; when the temperature of the outer surface of the detection unit changes, the resistivity of the first electrode layer changes so as to cause the resistance to change; the detection unit outputs a direct current analog current signal containing resistance value change information and an alternating current analog current signal with pressure value change to the filtering unit;
the filtering unit processes the received mixed analog electric signal through a low-pass filter to obtain a direct-current analog current signal with resistivity change and outputs the direct-current analog current signal to the first analog-to-digital converter, and the filtering unit processes the received mixed analog electric signal through a band-pass filter to obtain an alternating-current analog current signal and outputs the alternating-current analog current signal to the second analog-to-digital converter;
the first analog-to-digital converter converts the received direct-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit, and the second analog-to-digital converter converts the received alternating-current analog current signal into a digital signal and outputs the digital signal to the second central processing unit;
(IV) the second CPU calculates the digital electric signal received from the first A/D converter to obtain a temperature variation signal U T (t) outputting the pressure signal to the upper computer through the communication equipment, and calculating the digital signal received from the second analog-digital converter by the second central processing unit to obtain a pressure signal U F (t) outputting the data to an upper computer through communication equipment;
(V) the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally, calculating the pressure correction value.
2. A method of modifying temperature-affected plantar pressure according to claim 1, wherein: the first electrode layer comprises N small electrodes, and N is more than or equal to 1;
the front-end circuit further comprises a multiplexer;
the control signal output end of the controller is connected with the input ends of the N small electrodes included in the first electrode layer through a multiplexer;
the first back-end circuit further includes a first multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the first analog-to-digital conversion unit through a first multiplexer;
the second back-end circuit further comprises a second multiplexer;
the signal output ends of the pressure detection unit and the temperature detection unit are connected with the signal input end of the filtering unit through a second multiplexer.
3. A method of modifying temperature-affected plantar pressure according to claim 2, wherein: (IA) in a first process, in which,
the first step comprises the following steps sequentially carried out,
A. outputting a direct current signal and an alternating current signal to a plurality of modulators through a controller, and outputting the modulated direct current signal and alternating current signal to a first electrode layer through the multiplexer;
when the pressure applied to the sensor surface corresponding to the Nth small electrode of the first electrode layer changes, the surface of the piezoelectric film layer generates charges and further forms an alternating current analog current signal; when the temperature of the sensor surface corresponding to the Nth small electrode of the first electrode layer changes, the resistivity of the Nth small electrode changes to cause the resistance to change and further form a direct-current analog current signal; the detection unit outputs a direct current analog current signal containing resistance value change information and an alternating current analog current signal with pressure value change to the first multi-path demodulator;
B. the first multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the first analog-to-digital conversion unit;
in the fourth step, the first CPU calculates and processes the digital signal containing the temperature information to obtain a temperature change signal U near the Nth small electrode T (t) outputting the pressure signal to the upper computer through the communication equipment, and calculating and processing the digital signal containing the pressure information by the first central processing unit to obtain a pressure signal U near the Nth small electrode F (t) outputting the data to an upper computer through communication equipment;
in the fifth step, the upper computer receives the temperature change signal U T (t) calculating repairThe positive piezoelectric coefficient and the upper computer according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F (t) finally calculating a pressure correction value near the Nth small electrode;
(IIA) in the second process,
the step (one) comprises the following steps which are sequentially carried out,
a. outputting a direct current signal and an alternating current signal to a plurality of modulators through a controller, and outputting the modulated direct current signal and alternating current signal to a first electrode layer through the multiplexer;
when the pressure applied to the sensor surface corresponding to the Nth small electrode of the first electrode layer changes, the surface of the piezoelectric film layer generates charges and further forms an alternating current analog current signal; when the temperature of the sensor surface corresponding to the Nth small electrode of the first electrode layer changes, the resistivity of the Nth small electrode changes to cause the resistance to change and further form a direct-current analog current signal; the detection unit outputs a direct-current analog current signal containing resistance value change information and an alternating-current analog current signal with pressure value change to the second multi-path demodulator;
b. the second multiplexer demodulates the received mixed analog electric signal and outputs the demodulated mixed analog electric signal to the filtering unit;
in the step (IV), the second CPU calculates the digital electric signal received from the first ADC to obtain a temperature change signal U near the N-th small electrode T (t) outputting the pressure signal to the upper computer through the communication equipment, and calculating the digital signal received from the second analog-digital converter by the second central processing unit to obtain a pressure signal U near the Nth small electrode F (t) outputting the data to an upper computer through communication equipment;
in the step (five), the upper computer receives the temperature change signal U T (t) calculating the corrected piezoelectric coefficient, and the upper computer calculates the corrected piezoelectric coefficient according to the received pressure signal U F (t) calculating the total charge number Q of the detection unit F And (t) finally, calculating the pressure correction value near the Nth small electrode.
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