CN107890350A - A kind of wearable motion sensor, sensing circuit and method for testing motion - Google Patents

Abstract

A kind of wearable motion sensor, sensing circuit and method for testing motion; it is related to man-machine interaction sensor; provided with silicon rubber Dielectric film layers; silicon rubber Dielectric film layers the upper side and lower side is respectively equipped with flexible electrode layer and lower flexible electrode layer; insulating protective layer and lower insulating protective layer are respectively equipped with the downside of the upside of upper flexible electrode layer and lower flexible electrode layer; Top electrode pin and bottom electrode pin are respectively equipped with upper flexible electrode layer and lower flexible electrode layer, upper insulating protective layer and lower insulating protective layer are silicon rubber insulation protective layer.Sensing circuit is included with sensor body, current integration module, filtration module, signal processing module, decoupling processing module, power module of voltage regulation, switch module and display module；Detection method includes signal detection, processing, signal decoupling output in real time.The present invention have it is simple in construction, sensitivity, the high cost of precision are low, and real-time is good, wearing comfort, can accurate measurement human action the advantages that.

Description

A wearable motion sensor, sensing circuit and motion detection method

technical field

The invention relates to the field of sensors for human-computer interaction. Specifically, it is a wearable motion sensor based on silicon rubber, which is simple in structure, high in sensitivity and precision, low in cost, good in real-time, comfortable to wear, and capable of accurately measuring human body movements. Circuit and motion detection method.

Background technique

Virtual reality (Virtual Reality, VR) technology has been widely used in electronic products in recent years and has become a hot topic around the world. In June 2016 alone, the sales volume of VR products in China was close to 550,000 units, an increase of 27.8 times compared with that in January. The annual growth rate of the VR product market is expected to be as high as 500%. The human body joint motion detection sensor is a key component required by the interactive VR system. It can capture the human body's movement and posture information, and transmit the information to the virtual reality system to realize human-computer interaction. With the help of data gloves, users can naturally and efficiently complete human-computer interaction. In addition, human motion capture also has great application prospects in the fields of game entertainment, animation design, surgical teaching, sign language recognition, visual scientific research, robot control, military intelligence, and sports training.

The current human motion monitoring methods mainly use visual image tracking processing system and inertial measurement system. The former is expensive and the range of motion is limited by light restrictions; the latter is uncomfortable to wear and has low detection accuracy. For example, in existing wrist motion capture devices, the camera capture system is limited to indoors, the inertial measurement unit has the disadvantage of drift, and the rigid goniometer is uncomfortable to wear.

Contents of the invention

The purpose of the present invention is to solve the deficiencies of the above-mentioned prior art, and provide a wearable motion sensor with simple structure, high sensitivity, high precision, low cost, good real-time performance, comfortable to wear, and capable of accurately measuring human body movements and its use method. Not subject to lighting restrictions and other requirements,

The technical solution adopted by the present invention to solve the above-mentioned deficiencies in the prior art is:

A wearable motion sensor is characterized in that: a silicon rubber dielectric film layer is provided, an upper flexible electrode layer and a lower flexible electrode layer are respectively provided on the upper side and the lower side of the silicon rubber dielectric film layer, and the upper flexible electrode layer The upper side and the lower side of the lower flexible electrode layer are respectively provided with an upper insulating protective layer and a lower insulating protective layer, and the upper flexible electrode layer and the lower flexible electrode layer are respectively provided with upper electrode pins and lower electrode pins, and the upper insulating protective layer and the lower insulating protective layer is a silicone rubber insulating protective layer; it is prepared from the following materials and methods:

The first step is to prepare a silicone rubber dielectric film plate: prepare a sacrificial layer, weigh the reagent according to the mass ratio of polyacrylic acid and volatile solvent in a ratio of 1:3 to 1:5, place it in a small box, and then put it into a mixer. Mix and defoam and stir to obtain a sacrificial layer slurry; configure silicone rubber liquid, place the silicone rubber stock solution and diluent in a small box at a mass ratio of 1:1~3:2, then put it into a blender, mix and defoam and stir , to obtain a silicone rubber liquid; apply a sacrificial layer, and use a spreader to coat the sacrificial layer slurry on a thermoplastic polyester substrate. After coating, wait for the sacrificial layer to dry. For the rubber layer, apply the silicone rubber liquid on the thermoplastic polyester substrate covered with the sacrificial layer by using an applicator, hold up the coated substrate with a steel plate, and cover the acrylic cover; Silicone rubber dielectric film board for use;

The second step is to prepare the silicone rubber insulating protective layer: prepare the sacrificial layer slurry, weigh the reagent according to the mass ratio of polyacrylic acid and volatile solvent at 1:3~1:5, place it in a small box, and then add 2% of the total mass ~6% water, put it into the mixer, mix and defoam and stir to get the sacrificial layer slurry; configure silicone rubber liquid, wrap the raw material tape on the small box, and the mass ratio of silicone rubber stock solution and diluent is 1:1~ 3:2 put it in a small box, then put it into a mixer, mix and defoam and stir to obtain a silicone rubber liquid; apply a sacrificial layer, and use a coater to coat the sacrificial layer slurry on the thermoplastic polyester substrate, and finish coating Finally, wait for the sacrificial layer to dry, and the plastic polyester substrate will show seven colors after drying; apply the silicone rubber layer, use the applicator to coat the silicone rubber liquid on the thermoplastic polyester substrate covered with the sacrificial layer, and hold it up with a steel plate After coating the substrate, cover it with an acrylic cover; heat and cure it, send it to a heating box for heating, and obtain a silicone rubber insulating protective layer for use;

The third step is to prepare a flexible electrode: after mixing the carbon material and the volatile solvent at a mass ratio of 1:17~1:22, add steel balls to disperse the carbon powder, mix and stir in the mixer for defoaming, and obtain the electrode slurry; after the stirring is completed, Take out the small box, add the silicone rubber stock solution with a mass ratio of 1:9 to 1:11 to the carbon material in the electrode slurry, and then add a diluent with a mass ratio of 1:1 to 3:2 to the silicone rubber stock solution, and put it in the mixer Mix and stir in medium to defoam, and obtain a flexible electrode for use;

The fourth step is to cut the prepared silicone rubber dielectric film plate and silicon rubber insulating protective layer plate into a silicone rubber dielectric film plate unit and a silicone rubber insulating protective layer plate unit, and cut an electrode on the silicon rubber insulating protective layer plate unit Pin groove, cut out the electrode smear notch in the middle of the thermoplastic polyester plate; the size of the electrode smear notch is slightly smaller than the size of the silicone rubber dielectric film plate unit, and its shape is the same as the shape of the silicone rubber dielectric film plate unit, and the electrode smear When the notch is facing the silicone rubber dielectric film plate unit, the surrounding area of the electrode coating notch is 2 to 10 mm away from the surrounding area of the silicon rubber dielectric film plate unit.

The fifth step, the silicone rubber layer side of the silicone rubber dielectric film plate unit is attached to the thermoplastic polyester plate facing the electrode coating notch, and the silicone rubber layer side of the silicone rubber dielectric film plate unit in the electrode coating notch Coating the flexible electrode, after the coating of the flexible electrode is completed, the silicone rubber dielectric film plate unit is separated from the thermoplastic polyester plate, and heated and cured to obtain the silicone rubber dielectric film electrode plate;

The sixth step, plasma treatment, put the silicon rubber dielectric film electrode plate and the silicon rubber insulating protective layer plate unit into the plasma machine for plasma treatment;

The seventh step, the silicon rubber layer of the silicon rubber insulating protective layer plate unit after the plasma treatment and the flexible electrode of the silicon rubber dielectric thin film electrode plate are attached and bonded and fixed to obtain the main substrate of the sensor;

The eighth step, place the silicon rubber dielectric film electrode plate side of the sensor main substrate in boiling water to dissolve the sacrificial layer, and remove the thermoplastic polyester substrate;

The ninth step, repeating the operations of the fifth, sixth, and seventh steps above to obtain the sensor main board;

Step 10: Place both sides of the sensor main board in boiling water to dissolve the sacrificial layer, remove the thermoplastic polyester substrate, and obtain the sensor main body;

The eleventh step, place the electrode pins in the electrode pin slots, apply an appropriate amount of flexible electrodes in the electrode pin slots, put them in the heating box to heat and cure, and finally weld the wires on the electrode pins to complete the production.

The silicone rubber stock solution used in the silicone rubber dielectric film layer described in the present invention is LSR4305 or MED4901; the silicone rubber stock solution used in the silicone rubber insulating protective layer is LSR4305 or Sylgard186; the silicone rubber stock solution used in the flexible electrode layer is MED4901 .

The volatile solvent described in the present invention is isopropanol; the diluent is isooctane or OS-20; the preferred range of thickness of the silicone rubber dielectric film layer: 70-200 μm; the preferred range of thickness of the insulating protective layer: 200-400 μm.

A sensing circuit comprising the above-mentioned wearable motion sensor, including a sensor body, a current integration module, a filter module, a signal processing module, a decoupling processing module, a regulated power supply module, a switch module and a display module; a part of the sensor body One wire is connected to the output end of the switch module, and the other wire is connected to the non-inverting input end of the operational amplifier; the output end of the current integration module is connected to the input end of the filter module, the output end of the filter module is connected to the input end of the signal processing module, and the signal processing module The output end is connected to the input end of the decoupling processing module, the output end of the decoupling processing module is connected to the input end of the display module, and the stabilized power supply module is respectively connected to the current integration module, switch module, decoupling processing module and signal processing module (power supply for them) ), the input end of the switch module is connected to the pulse signal output end of the signal processing module (Pulse Width Modulation (PWM) periodic signal), the output end of the switch module is connected to the pulse signal input end (VD) of the current integration module, the sensor body connected by a wire.

The current integration module includes an operational amplifier and a reference capacitor. Between the output terminal of the operational amplifier and the non-inverting input terminal, and between the output terminal and the inverting input terminal, a measuring resistor R ₂ and a measuring resistor R ₄ are respectively connected. The reference capacitor C _ref is added to the non-inverting input Between the terminal and the ground, a measuring resistor R ₁ is connected in parallel to both ends of the reference capacitor C _ref , and a measuring resistor R ₃ is connected between the inverting input terminal and the ground. DES in the figure is a simplified sensor; one wire (one electrode pin) of the sensor is connected to the output terminal of the switch module, and the other wire (another electrode pin) is connected to the non-inverting input terminal of the operational amplifier. The sensor is regarded as two variable resistors and a variable capacitor in series, and the circuit is designed by using the current integration method.

A method for detecting motion using the above sensing circuit, characterized in that it comprises the following steps:

a. Attach and fix a sensor at the place where the stretch of the skin outside the joint changes the most when each movement of the joint to be detected occurs;

b. The sensor detects the motion analog signal of the joint angle change and outputs it to the filter module. The filter module performs (100-500Hz 200Hz) low-pass filtering on the motion electrical signal, and the low-pass filtered motion electrical signal is A/D converted by the signal processing module. Superimpose the signals of the two periods before and after and take the average value (there is a serious 50Hz electromagnetic noise interference in the sensing circuit without filtering, which makes the sensor very susceptible to interference from external signals, such as running computers around will also affect the sensor's readings It is very unstable. The signals of the two periods before and after are superimposed and averaged, and the noise is filtered out to improve the stability of the circuit indication. In actual measurement, the electromagnetic noise interference of two adjacent periods has the opposite effect on the waveform of the motion electrical signal) , get (digitally filtered) motion digital signal;

c. The motion digital signal input decoupling processing module (processor stm32f103, stm32f407 that realizes the above functions), the decoupling processing module substitutes the motion digital signal into the formula: Calculate the angle of the motion of the joint to be detected in one motion direction;

Regulations: To detect the motion angle of joint j in the direction of motion (degree of freedom), the motion angle of the detected joint in the jth motion direction (degree of freedom) is , Indicates the change of the i -th sensor voltage reading during exercise, symbol Indicates the slope between the movement angle in the jth movement direction (degree of freedom) and the change of the sensor voltage indication corresponding to the ith sensor (during single degree of freedom movement); it is written in the form of a matrix:

abbreviated as

Calculate the wrist joint motion angle through the reading of the sensor, that is,

d. The digital signal is output in real time through the display module.

The present invention calibrates the matrix before monitoring joint motion for the first time : When the joint moves to the limit position of each movement direction, record the change of the i -th sensor voltage reading when moving in the j -th movement direction (degree of freedom) , combined with the motion angles of each motion direction (degree of freedom) of the human body joints . Changes in the voltage readings of the i -th sensor during movement in the j -th motion direction (degree of freedom) Movement angles with each movement direction (degrees of freedom) of human joints The ratio is .

Use the sensor, sensor circuit and motion detection method of the present invention to monitor and measure joint motion, and detect circuit linearity errors The size of 0.0014, hysteresis error The magnitude is 0.006, the repeatability error is 0.0081, the sensitivity is 0.0082V/mm, and the dynamic response time is about 200ms; the present invention has no obvious hindrance to human joint movement, simple structure, high sensitivity, high precision, low cost, and real-time Good and other advantages; the present invention can monitor the movement data in time and objectively under the condition that the wearer's proprioception has not disappeared, and the real-time performance is good, and the wearer's movement and the display of the data occur almost at the same time.

Description of drawings

Fig. 1 is a schematic structural diagram of a sensor in the present invention.

Fig. 2 is a schematic diagram of the circuit structure of the current integrating module and the sensor in the present invention.

Fig. 3 is a schematic structural diagram of the sensing circuit in the present invention.

Fig. 4 is a schematic diagram of the structure of the sensor attached to the wrist when the present invention detects the movement of the wrist joint.

Fig. 5 is a comparison diagram of the motion angle curve of wrist joint palmar flexion detected by the wearable motion sensor of the present invention and the motion angle curve of wrist palm palmar flexion detected by standard instruments.

Fig. 6 is a comparison diagram of the motion angle curve of the wrist dorsiflexion motion detected by the wearable motion sensor of the present invention and the motion angle curve of the wrist dorsiflexion motion detected by a standard instrument.

Detailed ways

The wearable motion sensor shown in Figure 1 is provided with a silicon rubber dielectric film layer 6, and the upper and lower sides of the silicon rubber dielectric film layer 6 are respectively provided with an upper flexible electrode layer 3 and a lower flexible electrode layer 4, and the upper and lower sides of the silicon rubber dielectric film layer 6 are respectively provided with an upper flexible electrode layer 3 and a lower flexible electrode layer 4. The upper side of the flexible electrode layer 3 and the lower side of the lower flexible electrode layer 4 are respectively provided with an upper insulating protective layer 1 and a lower insulating protective layer 5, and the upper flexible electrode layer 3 and the lower flexible electrode layer 4 are respectively provided with upper electrode pins 2 and the lower electrode pin 7, the upper insulating protective layer 1 and the lower insulating protective layer 5 are silicone rubber insulating protective layers; the wearable motion sensor is prepared by the following materials and methods:

The first step is to prepare a silicone rubber dielectric film plate: prepare a sacrificial layer, weigh the reagent according to the mass ratio of polyacrylic acid and volatile solvent in a ratio of 1:3 to 1:5, place it in a small box and seal it, and then put it into a mixer , mix and defoam and stir to obtain a sacrificial layer slurry; configure silicone rubber solution, place the silicone rubber stock solution and diluent in a small box according to the mass ratio of 1:1~3:2 and seal it, then put it into a blender, mix and remove Foaming and stirring to obtain silicone rubber liquid; the original silicone rubber liquid is LSR4305 or MED4901, the prepared silicone rubber liquid has good fluidity, and there will be no shrinkage cavity and other defects after curing, and the tensile strength of the silicone rubber dielectric film reaches 3.4MPa Tear strength 10N/mm. Apply the sacrificial layer, apply the sacrificial layer slurry on the thermoplastic polyester substrate with a coater, wait for the sacrificial layer to dry, and the thermoplastic polyester substrate will show seven colors after drying; apply the silicone rubber layer, clean and apply After the device, use the applicator to coat the silicone rubber liquid on the thermoplastic polyester substrate covered with the sacrificial layer, hold up the coated substrate with a steel plate, and cover the acrylic cover; heat and cure, send it to the heating box for heating and curing, and the heating is completed Finally, cover the release paper to obtain a silicone rubber dielectric film board for use;

The second step is to prepare the silicone rubber insulation protection layer (upper insulation protection layer and lower insulation protection layer) board: prepare the sacrificial layer slurry, weigh the reagent according to the mass ratio of polyacrylic acid and volatile solvent at 1:3~1:5 and place it in In the small box, add water accounting for 2%~6% of the total mass, put it into the mixer, mix and defoam and stir, and obtain the sacrificial layer slurry; configure silicone rubber liquid, wrap the raw material tape on the small box, and silicone rubber The stock solution and diluent are placed in a small box according to the mass ratio of 1:1~3:2, then put it into the mixer, mix and defoam and stir to obtain a silicone rubber solution; the silicone rubber stock solution is LSR4305 or Sylgard186; apply a sacrificial layer, Use a coater to coat the sacrificial layer slurry on the thermoplastic polyester substrate. After the coating is finished, wait for the sacrificial layer to dry. After drying, the plastic polyester substrate will show seven colors; The rubber liquid is coated on the thermoplastic polyester substrate covered with the sacrificial layer with a coater, the coated substrate is held up with a steel plate, and the acrylic cover is covered; heating is cured, sent to a heating box for heating, and the release paper is covered after the heating is completed , to obtain a silicone rubber insulating protective laminate for use;

The third step is to prepare a flexible electrode: after mixing the carbon material and the volatile solvent at a mass ratio of 1:17~1:22, add steel balls to disperse the carbon powder, mix and stir in the mixer for defoaming, and obtain the electrode slurry; after the stirring is completed, Take out the small box, add the silicone rubber stock solution with a mass ratio of 1:9 to 1:11 to the carbon material in the electrode slurry, and then add a diluent with a mass ratio of 1:1 to 3:2 to the silicone rubber stock solution, and put it in the mixer Mix and stir in medium to defoam, and get a flexible electrode (solution) for use; the silicone rubber stock solution is MED4901; the flexible electrode has excellent electrical conductivity, high elasticity, firm adhesion, and a tensile strength of 2 MPa after being applied and dried.

The fourth step is to cut the prepared silicone rubber dielectric film plate and silicone rubber insulating protective layer plate into silicon rubber dielectric film plate unit and silicon rubber insulating protective layer plate according to the required size and shape with a laser cutting machine For the unit, cut an electrode pin groove that penetrates up and down on the silicone rubber insulating protective layer board unit (or the silicone rubber insulating protective layer of the silicone rubber insulating protective layer board unit), and cut out the upper and lower parts with a laser cutting machine in the middle of the thermoplastic polyester board. The through electrode smearing notch; the size of the electrode smearing notch is slightly smaller than the size of the silicone rubber dielectric film plate unit, and its shape is the same as that of the silicone rubber dielectric film plate unit, and the electrode smearing notch is the same as the silicone rubber dielectric film plate unit When facing right, the surrounding area of the electrode smearing notch is 2-10 mm away from the surrounding area of the silicone rubber dielectric film plate unit, preferably 4-6 mm.

The fifth step, the silicone rubber layer side of the silicone rubber dielectric film plate unit of the release paper is pasted on the thermoplastic polyester plate facing the electrode coating notch, and the silicone rubber dielectric film plate in the electrode coating notch Coat the flexible electrode on the silicone rubber layer side of the unit. After the flexible electrode is coated, separate the silicone rubber dielectric film plate unit from the thermoplastic polyester plate, heat and cure to form a flexible electrode layer, and obtain a silicone rubber dielectric film electrode plate;

The sixth step, plasma treatment, put the silicone rubber dielectric film electrode plate and the silicone rubber insulating protective layer unit with the release paper off into the plasma machine for plasma treatment;

In the seventh step, the silicon rubber layer of the silicon rubber insulating protective layer plate unit after the plasma treatment is bonded and fixed to the flexible electrode (layer) of the silicon rubber dielectric thin film electrode plate to obtain the sensor main substrate. The silicon rubber layer of the silicon rubber insulating protective layer plate after plasma treatment is more firmly bonded to the silicon rubber layer outside the flexible electrode (layer) of the silicon rubber dielectric film electrode plate. After the bonding is completed, put it under a heavy object for a period of time to ensure that the bond is firm;

The eighth step, place the silicon rubber dielectric film electrode plate side of the sensor main substrate in boiling water to dissolve the sacrificial layer, and remove the thermoplastic polyester substrate;

Step 9: Take the sensor body substrate removed from the thermoplastic polyester substrate in step 8 as the silicone rubber dielectric film plate unit with the release paper removed, and repeat the operations of the fifth, sixth, and seventh steps above to manufacture The middle is a silicone rubber dielectric film layer, the two (outer) sides of the silicone rubber dielectric film layer are flexible electrode layers, and the outer sides of the flexible electrode layer are the sensor main board of the silicone rubber insulating protective layer;

Step 10: Place both sides of the sensor main board in boiling water to dissolve the sacrificial layer, remove the thermoplastic polyester substrate, and obtain the sensor main body;

Step 11. Place the electrode pins in the electrode pin slots of the silicone rubber insulating protective layer. The electrode pins are electrically connected to the flexible electrode layer in the electrode pin slots of the silicone rubber insulating protective layer. Take an appropriate amount with tweezers The flexible electrode is applied in the electrode pin groove, fixedly connected with the flexible electrode layer of the silicone rubber dielectric film, put into the heating box to heat and solidify, and finally the wire is welded on the electrode pin to complete the production.

The volatile solvent used in this embodiment is isopropanol; the diluent is isooctane or OS-20; the preferred range of thickness of the silicone rubber dielectric film layer: 70-200 μm; the preferred range of thickness of the insulating protective layer: 200-400 μm.

As shown in Figure 2, the sensing circuit containing the above-mentioned wearable motion sensor includes a sensor mechanical body 02 (that is, the above-mentioned wearable motion sensor), a current integration module 01, a filter module 04, and a signal processing module 06 , decoupling processing module 07, regulated power supply module 05, switch module 03 and display module 08; one wire (one electrode pin) of the sensor body is connected to the output end of the switch module, and the other wire (another electrode pin) Pin) is connected to the non-inverting input terminal of the operational amplifier; the output terminal of the current integration module is connected to the input terminal of the filter module, the output terminal of the filter module is connected to the input terminal of the signal processing module, and the output terminal of the signal processing module is connected to the input terminal of the decoupling processing module. The output terminal of the coupling processing module is connected with the input terminal of the display module, the stabilized power supply module is respectively connected with the current integration module, the switch module, the decoupling processing module and the signal processing module (to provide power for them), the input terminal of the switch module is connected with the signal processing module The pulse signal output terminal is connected (Pulse Width Modulation (PWM) periodic signal), the output terminal of the switch module is connected with the pulse signal input terminal (VD) of the current integration module and a wire (an electrode pin) of the sensor body.

It can be seen from Figure 3 that the current integration module includes a single power supply operational amplifier and a reference capacitor, and the measurement resistor _R2 and the measurement resistor are connected between the output terminal of the operational amplifier and the non-inverting input terminal, and between the output terminal and the inverting input terminal. R ₄ , the reference capacitor C _ref is added between the non-inverting input terminal and the ground, a measuring resistor R ₁ is connected in parallel to both ends of the reference capacitor C _ref , and a measuring resistor R ₃ is connected between the inverting input terminal and the ground. DES in the figure is a simplified sensor; one wire (one electrode pin) of the sensor is connected to the output terminal of the switch module, and the other wire (another electrode pin) is connected to the non-inverting input terminal of the operational amplifier. The sensor is regarded as two variable resistors and a variable capacitor in series, and the circuit is designed by using the current integration method

A method for detecting motion using the above sensing circuit, characterized in that it comprises the following steps:

a. Attach and fix a sensor at the point where the skin stretch outside the joint changes the most when each movement (single-degree-of-freedom movement) of the joint to be detected (to be detected); use two kinds of adhesive tape to fix the sensor on the skin, one It is a kinesio patch with a certain degree of elasticity, which fixes the two ends of the sensor to the skin, and the other is medical tape, which strengthens and fixes the kinesio patch to the skin.

b. The sensor detects the motion analog signal of the joint angle change and outputs it to the filter module. The filter module performs a 200Hz low-pass filter on the motion electrical signal. Periodic signals are superimposed and averaged to obtain motion digital signals;

When filtering, the signal detected by the sensor has serious 50Hz electromagnetic noise interference, which makes the sensor very susceptible to interference from external signals, such as running a computer around it will also be affected, the sensor’s reading is very unstable, and the signals of the two cycles before and after are superposed Taking the average value and filtering out the noise improves the stability of the circuit indication. In actual measurement, the electromagnetic noise interference of two adjacent cycles has the opposite effect on the waveform of the motion electrical signal.

c. Input the motion digital signal into the decoupling processing module, and the decoupling processing module substitutes the motion digital signal into the formula: Calculate the angle of the joint to be detected in a movement direction (degree of freedom);

Regulations: to detect the motion angle of the j motion direction (degree of freedom) of the joint, and to detect the motion angle of the joint in the j motion direction (degree of freedom) as , Indicates the change of the i -th sensor voltage reading during exercise, symbol Indicates the slope between the movement angle in the jth movement direction (degree of freedom) and the change of the sensor voltage indication corresponding to the ith sensor (during single degree of freedom movement); it is written in the form of a matrix:

abbreviated as

Calculate the joint motion angle through the reading of the sensor, that is,

Among them, i and j are positive integers. for the matrix the inverse matrix of . This equation is the decoupling equation of joint motion. Although the above formula is derived in the case of compound movements, it is still applicable to a single independent simple movement.

d. The digital signal is output in real time through the display module.

The signal processing module and the decoupling processing module are realized by using the processor stm32f103 and/or stm32f407.

The present invention calibrates the matrix before monitoring joint motion for the first time : When the joint moves to the limit position of each motion direction (degree of freedom), record the change of the i -th sensor voltage indication when the motion is in the j- th motion direction (degree of freedom) Combined with the movement directions (degrees of freedom) of human joints . The change of the i- th sensor voltage indication during the movement in the j -th motion direction (degree of freedom) Movement directions (degrees of freedom) with human joints The ratio is .

When working, the signal processing module sends a pulse signal, the pulse signal is amplified by the switch module, the pulse signal is provided to the sensor, and the input signal is provided to the current integration module, the integration result is an analog signal, and the filter module increases the anti-interference ability of the circuit. The analog signal is low-pass filtered, and the filtered result is an analog signal. After the analog signal is converted by the signal processing module to perform analog-to-digital conversion (AD), digital filtering is performed. The digital filtering adopts the time-domain filtering method. The signals corresponding to each period are superimposed, and the arithmetic average operation is performed, so that the 50Hz noise is basically filtered out, and the display is stable.

After the digital signal output by the signal processing module is decoupled and processed by the decoupling processing module, the calculated joint angle is output and displayed on the display module. Under normal working conditions of the lithium battery power supply, the output voltage will decrease with the loss of power. During this process, the regulated power supply module modulates the voltage to keep the voltage constant.

Use the sensor, sensor circuit and motion detection method of the present invention to monitor and measure joint motion, and detect circuit linearity errors The size of 0.0014, hysteresis error The magnitude is 0.006, the repeatability error is 0.0081, the sensitivity is 0.0082V/mm, and the dynamic response time is about 200ms; the present invention has no obvious hindrance to human joint movement, simple structure, high sensitivity, high precision, low cost, and real-time Good and other advantages; the present invention can monitor the movement data in time and objectively under the condition that the wearer's proprioception has not disappeared, and the real-time performance is good, and the wearer's movement and the display of the data occur almost at the same time.

When using the present invention to detect wrist movement, the structure of the sensor attached to the wrist is shown in Figure 4.

Wherein 8 is the measurement sensor of ulnar flexion, 9 is the measurement sensor of pronation, 10 is the measurement sensor of supination, 11 is the measurement sensor of dorsiflexion, and 12 is the measurement sensor of palmar flexion.

In the process of wrist motion measurement, single-degree-of-freedom motion will affect another motion, and there is motion measurement coupling, which needs to be decoupled. There is a linear relationship between the voltage reading change of each sensor and any simple motion angle of the wrist joint. The change in voltage reading for each sensor is the sum of the changes in voltage readings caused by multiple simple movements.

As shown in Figure 4, detect the movement angles of the five movement directions (degrees of freedom) of the wrist joint, j represents 1-5 , 1 represents the palmar flexion movement of the wrist joint, 2 represents the dorsiflexion movement of the wrist joint, and 3 represents the ulnar flexion movement of the wrist joint , 4 represents wrist pronation motion, 5 represents wrist supination motion; use 5 sensors, i represents 1-5, 1 is the sensor for measuring palmar flexion motion of wrist joint, 2 is the sensor for measuring wrist dorsiflexion motion, 3 is Measuring the wrist joint ulnar flexion motion sensor, 4 is measuring the wrist joint pronation motion sensor, 5 is measuring the wrist joint supination motion sensor.

For each simple movement of the wrist joint, there are 5 relationships between the movement angle of the joint and the change of the sensor voltage indication, namely:

In the process of joint motion measurement, single-degree-of-freedom motion will affect another motion, and there is motion measurement coupling, which needs to be decoupled. There is a linear relationship between the voltage reading change of each sensor and any simple motion angle of the joint. The change in voltage reading for each sensor is the sum of the changes in voltage readings caused by multiple simple movements. Taking the number sensor as an example, there are:

Can also be written as:

Calibrate the linear relationship between each sensor voltage reading of the wrist joint and the 5 motion angles, that is, obtain the slope between the joint motion angle and the sensor voltage reading change .

Since there are 5 sensors, the form written in matrix is:

The above formula can be abbreviated as

Calculate the wrist joint motion angle through the reading of the sensor, that is,

in for the matrix the inverse matrix of . This equation is the decoupling equation of wrist motion.

Comparing the data obtained by using the present invention to measure the palmar flexion and dorsiflexion of the wrist with the data obtained by measuring the palmar flexion and dorsiflexion of the wrist with a standard instrument, it can be seen that the maximum measurement errors of the two are 2.35° and 1.07° respectively. The comparison charts of the detected data curves are shown in Figure 5 and Figure 6, where the ordinate is the change of the joint bending angle, and the abscissa is the movement time of the joint.

The sensor of the present invention has good measurement accuracy, is lightweight, has good flexibility and elasticity, has a large stretching variable, does not affect normal activities, and has a simple structure and low manufacturing cost. Its related performance is compared with common motion sensors as follows:

sensor Linearity Stretchability repeatability Hysteresis Anrenpu Flexible Fabric Strain Sensor 5% 60% 5% 5% Wearable motion sensor of the present invention 0.2% 200% 0.81% 0.6%

Claims (6)

1. A wearable motion sensor, comprising: the silicon rubber insulation protective layer is arranged on the upper side and the lower side of the silicon rubber dielectric film layer, an upper flexible electrode layer and a lower flexible electrode layer are respectively arranged on the upper side of the upper flexible electrode layer and the lower side of the lower flexible electrode layer, an upper electrode pin and a lower electrode pin are respectively arranged on the upper flexible electrode layer and the lower flexible electrode layer, and the upper insulation protective layer and the lower insulation protective layer are silicon rubber insulation protective layers; the material and the method are as follows:

firstly, preparing a silicon rubber dielectric film plate: preparing a sacrificial layer, weighing reagents according to a mass ratio of polyacrylic acid to volatile solvent of 1: 3-1: 5, placing the reagents into a small box, placing the small box into a stirrer, and uniformly mixing, defoaming and stirring to obtain sacrificial layer slurry; preparing silicon rubber liquid, placing the silicon rubber liquid and a diluent in a small box according to the mass ratio of 1: 1-3: 2, placing the silicon rubber liquid and the diluent in a stirrer, and uniformly mixing, defoaming and stirring to obtain the silicon rubber liquid; coating a sacrificial layer, namely coating the slurry of the sacrificial layer on the thermoplastic polyester substrate by using a coater, and after the coating is finished, drying the sacrificial layer to obtain seven colors of the thermoplastic polyester substrate; coating a silicon rubber layer, namely coating a silicon rubber solution on a thermoplastic polyester substrate covered with a sacrificial layer by using a coater, lifting the coated substrate by using a steel plate, and covering an acrylic cover; heating and curing, and sending the silicon rubber dielectric film plate to a heating box for heating and curing to obtain a silicon rubber dielectric film plate for later use;

step two, preparing a silicon rubber insulation protection layer plate: preparing sacrificial layer slurry, weighing reagents according to a mass ratio of 1: 3-1: 5 of polyacrylic acid and volatile solvent, placing the reagents into a small box, adding water accounting for 2-6% of the total mass, placing the reagents into a stirrer, and uniformly mixing, defoaming and stirring to obtain the sacrificial layer slurry; preparing silicon rubber liquid, winding a raw material belt on a small box, placing the silicon rubber liquid and a diluent in the small box according to the mass ratio of 1: 1-3: 2, placing the silicon rubber liquid and the diluent in a stirrer, and uniformly mixing, defoaming and stirring to obtain the silicon rubber liquid; coating a sacrificial layer, namely coating the slurry of the sacrificial layer on a thermoplastic polyester substrate by using a coater, and after the coating is finished, drying the sacrificial layer, wherein the dried plastic polyester substrate presents seven colors; coating a silicon rubber layer, namely coating a silicon rubber solution on a thermoplastic polyester substrate covered with a sacrificial layer by using a coater, lifting the coated substrate by using a steel plate, and covering an acrylic cover; heating and curing, and sending to a heating box for heating to obtain a silicon rubber insulation protective layer plate for later use;

step three, preparing a flexible electrode: mixing a carbon material and a volatile solvent in a mass ratio of 1: 17-1: 22, adding steel balls to disperse carbon powder, uniformly mixing and stirring in a stirrer, and defoaming to obtain electrode slurry; after stirring, taking out the small box, adding a silicon rubber stock solution with the mass ratio of 1: 9-1: 11 to the carbon material into the electrode slurry, adding a diluent with the mass ratio of 1: 1-3: 2 to the silicon rubber stock solution, and uniformly mixing, stirring and defoaming in a stirrer to obtain a flexible electrode for later use;

fourthly, cutting the prepared silicon rubber dielectric film plate and the prepared silicon rubber insulating protection layer plate into a silicon rubber dielectric film plate unit and a silicon rubber insulating protection layer plate unit, cutting an electrode pin groove on the silicon rubber insulating protection layer plate unit, and cutting an electrode smearing notch in the middle of the thermoplastic polyester plate;

fifthly, the silicon rubber layer side of the silicon rubber dielectric film plate unit is attached to the thermoplastic polyester plate opposite to the electrode coating groove opening, a flexible electrode is coated on the silicon rubber layer side of the silicon rubber dielectric film plate unit in the electrode coating groove opening, the silicon rubber dielectric film plate unit is separated from the thermoplastic polyester plate after the flexible electrode is coated, and the silicon rubber dielectric film plate is heated and cured to obtain a silicon rubber dielectric film electrode plate;

sixthly, performing plasma treatment, namely putting the silicon rubber dielectric film electrode plate and the silicon rubber insulating protection layer plate unit into a plasma machine for plasma treatment;

seventhly, oppositely attaching, bonding and fixing the silicon rubber layer of the silicon rubber insulation protection layer plate unit after plasma treatment and the flexible electrode of the silicon rubber dielectric film electrode plate to obtain a sensor main body substrate;

eighthly, placing one side of the silicon rubber dielectric film electrode plate of the sensor main body substrate in boiling water to dissolve the sacrificial layer, and removing the thermoplastic polyester substrate;

ninth, repeating the operations of the fifth step, the sixth step and the seventh step to obtain a sensor main body plate;

respectively placing the two sides of the sensor main body plate in boiling water to dissolve the sacrificial layer, and removing the thermoplastic polyester substrate to obtain a sensor main body;

and step eleven, placing the electrode pins into the electrode pin grooves, coating a proper amount of flexible electrodes into the electrode pin grooves, placing the electrode pins into a heating box for heating and curing, and finally welding wires on the electrode pins to finish the manufacturing.

2. The wearable motion sensor of claim 1, wherein: the silicon rubber collagen liquid used in the silicon rubber dielectric film layer is LSR4305 or MED 4901; the silicon rubber collagen liquid used in the silicon rubber insulating protective layer is LSR4305 or Sylgard 186; the silicone rubber collagen liquid used in the flexible electrode layer is MED 4901.

3. The wearable motion sensor of claim 1 or 2, wherein: the volatile solvent is isopropanol; the diluent is isooctane or OS-20; preferred ranges of the thickness of the silicone rubber dielectric film layer are: 70-200 μm; preferred ranges of the thickness of the insulating protective layer are: 200-400 μm.

4. A sensing circuit comprising the wearable motion sensor, characterized in that: the device comprises a sensor body, a current integration module, a filtering module, a signal processing module, a decoupling processing module, a voltage-stabilized power supply module, a switch module and a display module; one lead of the sensor body is connected with the output end of the switch module, and the other lead is connected with the non-inverting input end of the operational amplifier; the output end of the current integration module is connected with the input end of the filtering module, the output end of the filtering module is connected with the input end of the signal processing module, the output end of the signal processing module is connected with the input end of the decoupling processing module, the output end of the decoupling processing module is connected with the input end of the display module, the voltage-stabilized power supply module is respectively connected with the current integration module, the switch module, the decoupling processing module and the signal processing module, the input end of the switch module is connected with the pulse signal output end of the signal processing module, the output end of the switch module is connected with the pulse signal input end of the current integration.

5. The sensing circuit of claim 4, wherein: the current integration module comprises an operational amplifier and a reference capacitor, and a measuring resistor R is respectively connected between the output end and the non-inverting input end of the operational amplifier and between the output end and the inverting input end of the operational amplifier₂And measuring the resistance R₄Reference capacitance C_refA reference capacitor C connected between the non-inverting input terminal and ground_refAre connected in parallel with a measurementResistance R₁A measuring resistor R is connected between the inverting input end and the ground₃。

6. A method for detecting motion using the above sensing circuit, comprising the steps of:

a. attaching and fixing a sensor at the position where the skin stretching change outside the joint is maximum when each motion of the joint to be detected occurs;

b. the motion analog signal of the angle change of the joint detected by the sensor is output to a filtering module, the filtering module carries out low-pass filtering on the motion electric signal, and the motion electric signal after the low-pass filtering is subjected to A/D conversion by a signal processing module and then the signals of the previous period and the next period are superposed and averaged to obtain a motion digital signal;

c. inputting the motion digital signal into a decoupling processing module, and substituting the motion digital signal into a formula by the decoupling processing module:

calculating the angle of one motion direction of the joint motion to be detected;

stipulating: detecting jointsjThe motion angle of the joint in the first motion directionjThe movement angle in the signal movement direction is，Number 1 when indicating movementiVariation of voltage indication of sensor, signIs shown asjThe motion angle in the motion direction of the horn and the firstiThe slope between changes in the sensor voltage readings corresponding to the number sensor; it is written in the form of a matrix:

is abbreviated as

By estimating the angle of movement of the wrist joint by the readings of the sensors, i.e.

d. And the digital signal is output in real time through the display module.