CN112741618A - Tongue posture detection system and method based on FMCW radar - Google Patents

Tongue posture detection system and method based on FMCW radar Download PDF

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CN112741618A
CN112741618A CN202011527499.3A CN202011527499A CN112741618A CN 112741618 A CN112741618 A CN 112741618A CN 202011527499 A CN202011527499 A CN 202011527499A CN 112741618 A CN112741618 A CN 112741618A
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tongue
radar
radio frequency
processing module
frequency front
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CN112741618B (en
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皇甫江涛
林溥靖
魏路松
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Zhejiang University ZJU
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    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
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    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
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    • G01—MEASURING; TESTING
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    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
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    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/418—Theoretical aspects

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Abstract

The invention discloses a tongue posture detection system and method based on FMCW radar. The output end of the radar transceiving radio frequency front end is connected with the input end of the signal processing module, the feedback end of the signal processing module is connected with the control end of the radar transceiving radio frequency front end, the output end of the signal processing module is connected with the input end of the identification module, and the output end of the identification module is connected with the terminal interface; the intelligent identification of tongue gesture is realized to the identification module and the result is transmitted for the terminal interface and is shown, identification module still transmits the feedback signal back to signal processing module, and signal processing module generates corresponding transmission parameter according to the feedback signal and transmits for radar transceiver radio frequency front end, realizes the continuous regulation of FMCW radar signal. The invention has simple integral system structure and high portability, is suitable for silent interaction under various special scenes and provides a new way for disabled people to communicate.

Description

Tongue posture detection system and method based on FMCW radar
Technical Field
The invention relates to a tongue posture detection system and a method, in particular to a tongue posture detection system and a method based on FMCW radar.
Background
Light and electromagnetic waves are main media for human beings to observe and perceive the world, and along with the continuous development of science and technology, the application of the electromagnetic waves is wider and wider, such as 5G, the Internet of things, unmanned driving and the like, and especially along with the development of 5G, various electromagnetic wave-based perceptions also become academic and engineering research hotspots.
The newly appeared tongue gesture recognition system in various perception means has extremely wide application scenes. Firstly, in various special scenes such as military operations and the like, the tongue gesture recognition system can provide effective silent interaction; in addition, cases of paralysis caused by spinal cord injury are rising year by year, with about 250,000 to 500,000 new cases of spinal cord injury per year, worldwide. Depending on the severity of the injury, the patient may suffer partial or total paralysis and limited mobility. For example, paralysis of the arms, hands, torso, and legs of a patient suffering damage to the high cervical nerve (C1-C4) occurs. Such patients can only use head, tongue and eye movements as input for gesture recognition and environmental control. Among the three types of gesture input, the tongue is a common input organ for a large group of paralyzed patients. This is due to two reasons: first, the tongue is a soft organ that can be used to perform a large number of gestures. Second, the tongue is controlled by cranial nerves, which are embedded in the skull and are not easily damaged during spinal cord injury. It is therefore equally suitable for gesture recognition for a large number of paralyzed patients.
Tongue pose detection based on FMCW (frequency modulated continuous wave) radar is a new technology, a plurality of problems of a traditional identification scheme are overcome, the application prospect is wide, however, due to the fact that dynamic tongue poses have the characteristics of complexity, diversity and changeable space-time characteristics, a plurality of new challenges are brought to the research of human-computer interaction and tongue pose identification, and the technology has great research value and simultaneously has great challenges.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a tongue gesture detection system and a tongue gesture detection method based on an FMCW radar.
According to the invention, six groups of IQ intermediate frequency signals can be obtained by utilizing the radar receiving and transmitting radio frequency front end through switch switching, the signals are transmitted to the signal processing module to be processed by the intermediate frequency signals and output Doppler frequency shift change data, the Doppler frequency shift change data are transmitted to the identification module, the identification module processes and classifies the Doppler frequency shift change data, and then the result is displayed through the terminal interface.
The technical scheme of the invention is as follows:
tongue gesture detection system based on FMCW radar
The tongue gesture detection system comprises a plurality of radar transceiving radio frequency front ends, a plurality of signal processing modules and an identification module, wherein the output ends of the radar transceiving radio frequency front ends are connected with the input ends of the signal processing modules, the feedback ends of the signal processing modules are connected with the control ends of the radar transceiving radio frequency front ends, the output ends of the signal processing modules are connected with the input ends of the identification modules, and the output ends of the identification modules are connected with a terminal interface; the radar transceiving radio frequency front end transmits an FMCW radar signal to a detected tongue to be reflected to generate an FMCW radar echo signal, the FMCW radar echo signal is returned to the radar transceiving radio frequency front end, the radar transceiving radio frequency front end denoises and amplifies the FMCW radar echo signal and outputs an IQ intermediate frequency signal, the IQ intermediate frequency signal is input into a signal processing module, the signal processing module outputs Doppler shift change data after processing, an identification module processes the Doppler shift change data to obtain complex tongue motion characteristics and classifies the complex tongue motion characteristics, intelligent tongue gesture recognition is realized, the result is transmitted to a terminal interface and is finally displayed through the terminal interface, the identification module also feeds back the complex tongue motion characteristics to the signal processing module, the signal processing module generates corresponding transmitting parameters according to the fed back complex tongue motion characteristics and transmits the transmitting parameters to the radar transceiving radio frequency front end, continuous adjustment of FMCW radar signals is achieved.
The radar receiving and transmitting radio frequency front end comprises a transmitting end and a receiving end, wherein the transmitting end comprises a voltage-controlled oscillator, a low-pass filter, a local oscillator signal generator, a first frequency mixer, a power divider, two amplifiers, two switches and two transmitters; the output end of the voltage-controlled oscillator is connected with a power divider through a low-pass filter, a first frequency mixer and a signal processing module in sequence, the control end of the voltage-controlled oscillator is used as the control end of a radar transceiving radio frequency front end and is connected with the signal processing module, the first frequency mixer is also connected with a local oscillator signal generator, the power divider is connected with a transmitter through an amplifier and a switch in sequence, and the power divider is also connected with another transmitter through another amplifier and another switch in sequence;
the receiving end comprises two receivers, two low noise amplifiers, four mixers and two phase shifters; the first receiver is connected with the second mixer after passing through the first low-noise amplifier, the power divider is connected with the second mixer, the output of the second mixer is used as the first output end of the radar transceiving radio frequency front end, the first low-noise amplifier is also connected with the third mixer, the power divider is connected with the third mixer after passing through a phase shifter, and the output of the third mixer is used as the second output end of the radar transceiving radio frequency front end; the second receiver is connected with a fourth frequency mixer after passing through a second low noise amplifier, a power divider is connected with the fourth frequency mixer, the output of the fourth frequency mixer is used as a third output end of a radar transceiving radio frequency front end, the second low noise amplifier is also connected with a fifth frequency mixer, the power divider is connected with the fifth frequency mixer after passing through another phase shifter, and the output of the fifth frequency mixer is used as a fourth output end of the radar transceiving radio frequency front end.
The signal processing module comprises four filtering amplification processing modules, four digital-to-analog converters and a voltage-controlled waveform generating and operating unit; a first output end of the radar transceiving radio frequency front end is connected with a first filtering amplification processing module, and the first filtering amplification processing module is connected to the operation unit after passing through a first digital-to-analog converter; a second output end of the radar transceiving radio frequency front end is connected with a second filtering amplification processing module, and the second filtering amplification processing module is connected to the operation unit after passing through a second digital-to-analog converter; a third output end of the radar transceiving radio frequency front end is connected with a third filtering amplification processing module, and the third filtering amplification processing module is connected to the operation unit after passing through a third digital-to-analog converter; a fourth output end of the radar transceiving radio frequency front end is connected with a fourth filtering amplification processing module, and the fourth filtering amplification processing module is connected to the operation unit after passing through a fourth digital-to-analog converter; the operation unit is connected with the control end of the voltage-controlled waveform generation module, and the output end of the voltage-controlled waveform generation module is connected with the control end of the voltage-controlled oscillator.
The radar transmitting and receiving radio frequency front end is a millimeter wave FMCW radar.
The identification module is a computer terminal.
The filtering amplification processing module comprises a preposed low noise amplifier, a high pass filter, a variable gain amplifier and a low pass filter.
Second, adopt tongue appearance detection system's a tongue appearance detection method based on FMCW radar
The transmitting end of the radar transmitting and receiving radio frequency front end has three transmitting states, each receiver in the receiving end of the radar transmitting and receiving radio frequency front end receives three groups of receiving signals, finally the radar transmitting and receiving radio frequency front end outputs six groups of IQ intermediate frequency signals, the signal processing module demodulates and calculates each group of IQ intermediate frequency signals to obtain Doppler frequency shift change data and transmits the Doppler frequency shift change data to the identification module, the identification module calculates complex tongue motion characteristics in the Doppler frequency shift change data, the complex tongue motion characteristics are used for classifying the Doppler frequency shift change data, intelligent tongue gesture identification is achieved, results are transmitted to a terminal interface, and finally the results are displayed through the terminal interface;
the identification module feeds back the complex tongue motion characteristics corresponding to the Doppler frequency shift change data to the operation unit of the signal processing module, and the operation unit judges the motion state of the detected tongue according to the fed back complex tongue motion characteristics and simultaneously calculates the distance between the detected tongue and the front end of the radar receiving and transmitting radio frequency so as to determine the motion process of the detected tongue; according to the motion process of the detected tongue, the operation unit outputs the optimal emission parameter of the emission end in the motion process, and the voltage control waveform generation module changes the generated voltage shape, so that the emitted FMCW radar signal is changed.
The transmission parameter being, in particular, an FMCW radar signal T (t)Parameter a1、a2、a3、b1、b2、b3C, the formula is as follows:
T(t)＝a1 sin b1t+a2 sin b2t+a3 sin b3t+c＝AT cos(2πftt)
wherein, a1、a2、a3、b1、b2、b3C are constants, ATRepresenting the amplitude, f, of the transmitted FMCW radar signaltRepresenting a transmission frequency of a transmitted FMCW radar signal;
the operation unit adjusts the parameter a according to the feedback tongue complex motion characteristic1、a2、a3、b1、b2、b3C, the value of the parameter a1、a2、a3、b1、b2、b3C to the voltage-controlled waveform generation module, thereby enabling the transmission frequency ftA change occurs.
The feedback tongue complex motion characteristics comprise amplitudes of two paths of I echo signals I (t) and two paths of Q echo signals Q (t) in IQ intermediate frequency signals
Figure BDA0002851245880000041
Phase phi and Doppler frequency fdThe formulas of the I echo signal I (t) and the Q echo signal Q (t) are as follows:
Figure BDA0002851245880000042
Figure BDA0002851245880000043
wherein A isTRepresenting the amplitude, A, of the transmitted FMCW radar signalR(t) amplitude of received FMCW radar return signals, fdIndicating the Doppler frequency of the received FMCW radar echo signal, phi is the time before the tongue and the radar transmit-receive radio frequency in the initial stateThe phase formed by the distance between the ends;
the Doppler shift fdSatisfy fd＝fr-ftWherein f istRepresenting the transmission frequency, f, of transmitted FMCW radar signalsrRepresenting a reception frequency of a received FMCW radar echo signal;
and a transmission frequency ftAnd a reception frequency frSatisfies the following relationship:
Figure BDA0002851245880000044
where c represents the speed of light and v represents the speed of tongue movement.
The invention has the beneficial effects that:
1) the radar electromagnetic wave perception is non-contact perception, and the universality of the system is stronger;
2) based on tongue gesture recognition of a millimeter wave radar frequency band, data flow is radar signals, and even if the signals are leaked, an attacker is difficult to directly see any useful information, so that certain guarantee is provided for the safety of a system;
3) the tongue gesture recognition based on the millimeter wave radar can be integrated on a high-speed processing chip with low energy consumption and small volume, and the possibility of embedding into a portable device is provided.
Drawings
FIG. 1 is a schematic block diagram of a system according to the present invention;
FIG. 2 is a schematic diagram of a radar module and a signal processing module according to the present invention;
FIG. 3 is a schematic diagram of a waveform fit of a transmitted signal according to the present invention;
FIG. 4 is a schematic flow chart of the algorithm of the present invention;
FIG. 5 is a schematic diagram of a terminal interface according to the present invention;
in the figure: a radar transmit-receive radio frequency front end (1); a signal processing module (2); an identification module (3); a terminal interface (4).
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 1, the tongue gesture detection system includes a plurality of radar transceiving radio frequency front ends 1, a plurality of signal processing modules 2, and an identification module 3, wherein an output end of the radar transceiving radio frequency front end 1 is connected with an input end of the signal processing module 2, a feedback end of the signal processing module 2 is connected with a control end of the radar transceiving radio frequency front end 1, an output end of the signal processing module 2 is connected with an input end of the identification module 3, an output end of the identification module 3 is connected with a terminal interface 4, the radar transceiving radio frequency front end 1 is a millimeter wave FMCW radar, and the identification module 3 is a computer terminal; the radar transceiving radio frequency front end 1 transmits FMCW radar signals to a detected tongue to be reflected to generate FMCW radar echo signals and returns the FMCW radar echo signals to the radar transceiving radio frequency front end 1, the radar transceiving radio frequency front end 1 denoises and amplifies the FMCW radar echo signals and outputs IQ intermediate frequency signals, the IQ intermediate frequency signals are input into the signal processing module 2, the signal processing module 2 outputs Doppler shift change data after processing, the identification module 3 processes the Doppler shift change data to obtain complex tongue motion characteristics and classifies the complex tongue motion characteristics to realize intelligent tongue gesture identification and transmit the result to the terminal interface 4, the result is displayed through the terminal interface 4, the identification module 3 also feeds back the complex tongue motion characteristics to the signal processing module 2, the signal processing module 2 generates corresponding transmitting parameters according to the fed back complex tongue motion characteristics and transmits the transmitting parameters to the radar transceiving radio frequency front end 1, the continuous adjustment of FMCW radar signals is realized, the detection sensitivity of the FMCW radar is improved, and the detection effect is improved.
As shown in fig. 2, the radar transceiving radio frequency front end 1 includes a transmitting end and a receiving end, where the transmitting end includes a voltage-controlled oscillator, a low-pass filter, a local oscillator signal generator, a first mixer, a power divider, two amplifiers, two switches, and two transmitters; the output end of a voltage-controlled oscillator is connected with a power divider through a low-pass filter and a first frequency mixer in sequence, the control end of the voltage-controlled oscillator is used as the control end of a radar transceiving radio frequency front end 1 and is connected with a signal processing module 2, the first frequency mixer is also connected with a local oscillator signal generator, the power divider is connected with a transmitter through an amplifier and a switch in sequence, and the power divider is connected with another transmitter through another amplifier and another switch in sequence;
the receiving end comprises two receivers, two low noise amplifiers, four mixers and two phase shifters; the first receiver is connected with the second mixer after passing through the first low-noise amplifier, the power divider is connected with the second mixer, the output of the second mixer is used as the first output end of the radar transceiving radio frequency front end 1, the first low-noise amplifier is also connected with the third mixer, the power divider is connected with the third mixer after passing through a phase shifter, and the output of the third mixer is used as the second output end of the radar transceiving radio frequency front end 1; the second receiver is connected with a fourth frequency mixer after passing through a second low noise amplifier, a power divider is connected with the fourth frequency mixer, the output of the fourth frequency mixer is used as a third output end of the radar transceiving radio frequency front end 1, the second low noise amplifier is also connected with a fifth frequency mixer, the power divider is connected with the fifth frequency mixer after passing through another phase shifter, and the output of the fifth frequency mixer is used as a fourth output end of the radar transceiving radio frequency front end 1.
The signal processing module 2 comprises four filtering amplification processing modules, four digital-to-analog converters and a voltage-controlled waveform generating and operating unit; a first output end of the radar transceiving radio frequency front end 1 is connected with a first filtering amplification processing module, and the first filtering amplification processing module is connected to an operation unit after passing through a first digital-to-analog converter; a second output end of the radar transceiving radio frequency front end 1 is connected with a second filtering amplification processing module, and the second filtering amplification processing module is connected to the arithmetic unit after passing through a second digital-to-analog converter; a third output end of the radar transceiving radio frequency front end 1 is connected with a third filtering amplification processing module, and the third filtering amplification processing module is connected to the operation unit after passing through a third digital-to-analog converter; a fourth output end of the radar transceiving radio frequency front end 1 is connected with a fourth filtering amplification processing module, and the fourth filtering amplification processing module is connected to the operation unit after passing through a fourth digital-to-analog converter; the operation unit is connected with the control end of the voltage-controlled waveform generation module, and the output end of the voltage-controlled waveform generation module is connected with the control end of the voltage-controlled oscillator.
The filtering amplification processing module comprises a preposed low-noise amplifier, a high-pass filter, a variable gain amplifier and a low-pass filter and is used for processing IQ intermediate frequency signals.
In specific implementation, the filtering and amplifying processing module mainly comprises four parts, namely a preposed low-noise amplifier, a high-pass filter, a variable gain amplifier and a low-pass filter. The preposed low-noise amplifier mainly comprises a high-precision operational amplifier OP211, can realize the characteristics of low noise, low power consumption, high bandwidth and the like, and can realize the amplification of the received weak IQ intermediate frequency signal and the reduction of the interference of the noise on the IQ intermediate frequency signal; a high-pass filter AD8671 and a low-pass filter AD8671 are adopted, the high-pass filter filters leaked modulation signals, power supply noise and short-distance low-frequency interference signals, and the low-pass filter filters high-frequency harmonic components in the circuit and in the signals; the variable gain adjusting circuit mainly comprises a variable gain amplifier AD603, the variable gain adjusting circuit adjusts gain according to the size of the filtered signal, and different IQ intermediate frequency signals are amplified to the amplitude which can be sampled and distinguished by the analog-to-digital converter, so that the operation unit can work normally.
The transmitting end of the radar transceiving radio frequency front end 1 has three transmitting states, each receiver in the receiving end of the radar transceiving radio frequency front end 1 receives three groups of receiving signals, finally, the radar transceiving radio frequency front end 1 outputs six groups of IQ intermediate frequency signals, the signal processing module 2 demodulates and calculates each group of IQ intermediate frequency signals to obtain Doppler frequency shift change data and transmits the Doppler frequency shift change data to the identification module 3, the identification module 3 calculates complex tongue motion characteristics in the Doppler frequency shift change data, the complex tongue motion characteristics are used for classifying the Doppler frequency shift change data, intelligent tongue gesture identification is achieved, results are transmitted to the terminal interface 4, and finally, the results are displayed through the terminal interface 4;
the identification module 3 feeds back the complex tongue motion characteristics corresponding to the Doppler frequency shift change data to the operation unit of the signal processing module 2, and the operation unit judges the motion state of the detected tongue according to the fed back complex tongue motion characteristics and simultaneously calculates the distance between the detected tongue and the radar transmitting and receiving radio frequency front end 1 so as to determine the motion process of the detected tongue, namely whether the detected tongue is close to or far away from the radar transmitting and receiving radio frequency front end 1; according to the motion process of the detected tongue, the operation unit outputs the optimal emission parameter of the emission end in the motion process, and the voltage-controlled waveform generation module changes the generated voltage shape, so that the emitted FMCW radar signal is changed, and the detection sensitivity and effect are improved.
The transmission parameter is specifically parameter a of FMCW radar signal T (t) fitted by a third-order nonlinear function1、a2、a3、b1、b2、b3C, the formula is as follows:
T(t)＝a1 sin b1t+a2 sin b2t+a3 sin b3t+c＝AT cos(2πftt)
wherein, a1、a2、a3、b1、b2、b3C are constants, ATRepresenting the amplitude, f, of the transmitted FMCW radar signaltRepresenting a transmission frequency of a transmitted FMCW radar signal;
the operation unit adjusts the parameter a according to the feedback tongue complex motion characteristic1、a2、a3、b1、b2、b3C, the value of the parameter a1、a2、a3、b1、b2、b3C to the voltage-controlled waveform generation module, thereby enabling the transmission frequency ftA change occurs.
The feedback tongue complex motion characteristics comprise amplitude of two paths of I echo signals It and two paths of Q echo signals Qt in IQ intermediate frequency signals
Figure BDA0002851245880000071
Phase phi and Doppler frequency fdThe formulas of the I-path echo signal It and the Q-path echo signal Qt are as follows:
Figure BDA0002851245880000072
Figure BDA0002851245880000073
wherein A isTRepresenting the amplitude, A, of the transmitted FMCW radar signalRt represents the amplitude of the received FMCW radar return signal, fdThe Doppler frequency of a received FMCW radar echo signal is represented, phi is a phase formed by the distance between the tongue and the radar receiving and transmitting radio frequency front end 1 in an initial state, and therefore the distance between the tongue and the radar receiving and transmitting radio frequency front end 1 is calculated and detected according to the phase phi;
doppler shift fdSatisfy fd＝fr-ftWherein f istRepresenting the transmission frequency, f, of transmitted FMCW radar signalsrRepresenting a reception frequency of a received FMCW radar echo signal;
and a transmission frequency ftAnd a reception frequency frSatisfies the following relationship:
Figure BDA0002851245880000074
wherein c represents the speed of light, v represents the speed of tongue movement, and v is about 0.02m/s to 0.05 m/s.
When the tongue action amplitude is large and the frequency is low, adjust a1、a2、a3、b1、b2、b3C, making the emission signal be a waveform 1 close to a sawtooth wave; when the tongue motion amplitude is small, the motion is high and the frequency is low, for example, when speaking, the a is adjusted1、a2、a3、b1、b2、b3C, the value of the transmitting signal is close to the waveform 2 of the inverse sawtooth wave; when the tongue action amplitude is small and the frequency is high, the a is adjusted1、a2、a3、b1、b2、b3C, the value of the transmitting signal is a waveform 3 close to a triangular wave; when the detected interference of the facial muscles is larger, the value of c is adjusted, so that the bandwidth of the transmitted signal is increased to reduce the interference.
Example (b):
the radar parameters mainly include the number of transmitting antennas NTxReceiving antennaNumber NRxFrequency-modulated starting frequency f1Frequency modulation slope KsFrequency modulation period TcEach frame of frequency modulation period NchirpFrame period TfNumber of ADC samples in one cycle NadcADC sampling period TadcADC sampling rate FsEtc. these parameters are determined by the maximum measured distance d of the application scenariomaxDistance resolution dresMaximum measurement velocity vmaxVelocity resolution vresAnd frame rate frateDetermined by main indexes, wherein the indexes respectively satisfy the formula
dmax＝Nadc×dres (1)
Figure BDA0002851245880000081
Figure BDA0002851245880000082
Figure BDA0002851245880000083
Figure BDA0002851245880000084
Wherein c is the speed of light, λ is the wavelength corresponding to the modulation center frequency, B is the effective bandwidth of modulation, and the effective bandwidth of modulation B is the modulation slope KsAnd ADC sampling period TadcJointly determining:
Figure BDA0002851245880000085
the wavelength lambda corresponding to the modulation center frequency is determined by the modulation starting frequency f1And the bandwidth B of the frequency modulation is determined together:
Figure BDA0002851245880000086
modulation period TcFor adjusting the maximum measuring speed vmaxAnd velocity resolution vresThe requirements are as follows:
Figure BDA0002851245880000087
wherein, tauc-idleIs the idle time after transmitting 1 periodic sweep signal.
Frame period TfFor adjusting the frame rate frateThe requirements are as follows:
Tf＝Nchirp×Tc+τf-idle (9)
wherein, tauf-idleTo transmit NchirpIdle time after the signal is swept for each period.
For Multiple Input Multiple Output (MIMO) mode using Time Division Multiplexing (TDM), frame period TfThe requirements are satisfied:
Tf＝NTx×Nchirp×Tc+τf-idle (10)
the upper parameter limit supported by radar hardware is generally taken as a prerequisite for designing radar parameters, and the upper parameter limit of millimeter wave radar related to tongue gesture recognition application comprises a maximum measurement distance d determined by transmission powerm-maxMaximum field angle θ in the horizontal and vertical directions determined by antenna designFOVAnd the number of virtual channels Nchan-HAnd Nchan-VMaximum swept bandwidth BmaxMaximum chirp slope
Figure BDA0002851245880000091
Minimum chirp slope
Figure BDA0002851245880000092
Maximum ADC sample rate
Figure BDA0002851245880000093
And minimum ADC sampling rate
Figure BDA0002851245880000094
And the like.
In-pair distance resolution dresIn the application scenario where the requirement is high, the distance resolution d should be setresAs small as possible, the effective bandwidth B is required to be as large as possible according to equation (2), and the effective bandwidth B is determined by the chirp rate K according to equation (6)sNumber of ADC samples NadcAnd ADC sampling rate FsAnd (4) jointly determining.
At a distance resolution dresAfter determination, according to the formula (1), the number N of ADC sampling pointsadcCan measure the distance d from the maximummaxAnd (4) determining.
Frequency modulation slope KsAnd ADC sampling rate FsCan be determined by formula (6) and formula (8) together, but satisfy Fs-min≤Fs≤Fs-maxAnd Ks-min≤Ks≤Ks-maxThe conditions of (1).
The human tongue has an upper limit on its velocity of movement if the frequency modulation period TcUnreasonable setting, maximum measuring speed vmaA small deviation will result in a velocity ambiguity, the maximum measured velocity vmaxGreater than this will result in vres＝2vmax/NchirpOn the larger side, according to equations (8) and (10), the design criteria are: on the premise of meeting the measurement requirement of the maximum movement speed of the target, the speed resolution v is enabled to beresAs small as possible to capture finer tongue movements, but taking into account the frequency modulation period N per framechirpFrame rate size may be affected.
According to equation (5), the frame period TfDetermines the frame rate of the range-doppler spectrogram, and thus the temporal resolution of the tongue pose, which can be divided more finely by the frame period, but the frame period T is higher for higher frame ratesfThe real-time processing capability of hardware is also considered, namely the data processing equipment is required to complete the whole process operation of radar data processing, feature elimination and tongue gesture classification in one frame period.
Fitting the transmitted FMCW radar signal with a third order nonlinear function:
T(t)＝a1 sin b1t+a2 sin b2t+a3 sin b3t+c＝AT cos(2πftt) (11)
by varying the parameter a1、a2、a3、b1、b2、b3C may change the waveform and frequency of the transmitted FMCW radar signal, e.g., when a1＝-2、a2＝-1、
Figure BDA0002851245880000101
b1＝1、b2＝2、b3When the period is 3 and the c is 1.5, the emission signal is a sawtooth wave with the period of 2 pi and the amplitude of 3. For a certain action, a specific frequency scanning mode can obtain effective tongue posture information with a higher signal-to-noise ratio, and after the operation unit receives complex tongue motion characteristics fed back by the recognition module, frequency sweep parameters can be changed, and an optimal scanning frequency band can be obtained after multiple feedbacks.
FMCW radar return signal R (t) is R (t) ═ AR(t)cos(2π(ft+fd) t + phi), obtaining an intermediate I-path echo signal I' (t), and adopting the following formula:
Figure BDA0002851245880000102
the intermediate I path echo signal I' (t) is filtered by a low pass filter to remove the high frequency component 2ft+fdAnd obtaining an I-path echo signal: (12)
Figure BDA0002851245880000103
the intermediate Q-path echo signal Q' (t) is expressed as follows:
Figure BDA0002851245880000104
the middle Q-path echo signal Q' (t) is filtered by a low-pass filter to remove the high-frequency component 2ft+fdAnd obtaining Q-path echo signals:
Figure BDA0002851245880000111
doppler shift fdSatisfy fd＝fr-ftWherein f istRepresenting the transmission frequency, f, of transmitted FMCW radar signalsrRepresenting a reception frequency of a received FMCW radar echo signal;
and a transmission frequency ftAnd a reception frequency frSatisfies the following relationship:
Figure BDA0002851245880000112
wherein c represents the speed of light, v represents the speed of tongue movement, and the speed of tongue movement is about 0.02m/s to 0.05 m/s.
When the tongue action amplitude is large and the frequency is low, adjust a1、a2、a3、b1、b2、b3C, making the emission signal be a waveform 1 close to a sawtooth wave; when the tongue motion amplitude is small, the motion is high and the frequency is low, for example, when speaking, the a is adjusted1、a2、a3、b1、b2、b3C, the value of the transmitting signal is close to the waveform 2 of the inverse sawtooth wave; when the tongue action amplitude is small and the frequency is high, the a is adjusted1、a2、a3、b1、b2、b3C, the value of the transmitting signal is a waveform 3 close to a triangular wave; when the detected interference of the facial muscles is larger, the value of c is adjusted, so that the bandwidth of the transmitted signal is increased to reduce the interference.
Because the radar works at 24GHz and the doppler shift range is [2.7, 8.0] Hz, as shown in fig. 4, the identification module processes doppler shift change data to obtain recovered I-path echo signals and Q-path echo signals, and performs arc tangent operation on the recovered I-path echo signals and Q-path echo signals to obtain a phase difference signal Θ:
Figure BDA0002851245880000113
the phase difference signal theta is subjected to derivation to obtain a derivative, and if the derivative is a positive value, the detected tongue approaches to the front end of the radar receiving and transmitting radio frequency; if the derivative is a negative value, the detected tongue is far away from the front end of the radar transmitting and receiving radio frequency, and therefore the state of the detected tongue is judged. And the recognition module determines tongue postures for classification by combining the six groups of complex motion characteristics of the tongue after Doppler frequency shift change data processing, and finally realizes intelligent recognition of the tongue postures and displays the tongue postures on a terminal interface.
In a specific implementation, as shown in fig. 5, after receiving the signal of the identification module 3, the terminal interface 4 lights up the corresponding indicator lamp according to the corresponding tongue gesture. When the detected tongue moves from the middle part to the direction of the indicator light 1, the indicator light 1 is lightened to the left; when the detected tongue moves to the middle part from the direction of the indicator light 1, the right side of the indicator light 1 is lightened; when the detected tongue moves from the middle part to the direction of the indicator light 2, the indicator light 2 is lightened right; when the detected tongue moves to the middle part from the direction of the indicator light 2, the indicator light 2 is lightened to the left; when the detected tongue moves from the middle part to the direction of the indicator light 3, the lower part of the indicator light 3 is lightened; when the detected tongue moves towards the middle part from the direction of the indicator light 3, the indicator light 3 is lightened.
The system has simple structure and high portability, can be applied to silent interaction under various special scenes, provides a new way for disabled people to communicate, and has obvious improvement compared with the traditional highly-invasive detection system.

Claims (10)

1. A tongue appearance detecting system based on FMCW radar which characterized in that: the system comprises a plurality of radar transceiving radio frequency front ends (1), a plurality of signal processing modules (2) and an identification module (3), wherein the output end of each radar transceiving radio frequency front end (1) is connected with the input end of each signal processing module (2), the feedback end of each signal processing module (2) is connected with the control end of each radar transceiving radio frequency front end (1), the output end of each signal processing module (2) is connected with the input end of each identification module (3), and the output end of each identification module (3) is connected with a terminal interface (4); the method comprises the steps that a radar transceiving radio frequency front end (1) emits FMCW radar signals to a detected tongue to be reflected to generate FMCW radar echo signals, the FMCW radar echo signals are returned to the radar transceiving radio frequency front end (1), the radar transceiving radio frequency front end (1) denoises and amplifies the FMCW radar echo signals and outputs IQ intermediate frequency signals, the IQ intermediate frequency signals are input into a signal processing module (2), Doppler frequency shift change data are output after being processed by the signal processing module (2), an identification module (3) processes the Doppler frequency shift change data to obtain tongue complex motion characteristics and classifies the tongue complex motion characteristics, intelligent tongue gesture identification is achieved, results are transmitted to a terminal interface (4), display is finally carried out through the terminal interface (4), the identification module (3) feeds the tongue complex motion characteristics back to the signal processing module (2), the signal processing module (2) generates corresponding emission parameters according to the fed back tongue complex motion characteristics and transmits the emission parameters to the radar transceiving radio frequency front end (1) And continuous regulation of FMCW radar signals is realized.
2. An FMCW radar-based tongue pose detection system as claimed in claim 1, wherein: the radar transceiving radio frequency front end (1) comprises a transmitting end and a receiving end, wherein the transmitting end comprises a voltage-controlled oscillator, a low-pass filter, a local oscillator signal generator, a first frequency mixer, a power divider, two amplifiers, two switches and two transmitters; the output end of a voltage-controlled oscillator is connected with a power divider through a low-pass filter and a first frequency mixer in sequence, the control end of the voltage-controlled oscillator is used as the control end of a radar transceiving radio frequency front end (1) and is connected with a signal processing module (2), the first frequency mixer is also connected with a local oscillator signal generator, the power divider is connected with a transmitter through an amplifier and a switch in sequence, and the power divider is connected with another transmitter through another amplifier and another switch in sequence;
the receiving end comprises two receivers, two low noise amplifiers, four mixers and two phase shifters; the first receiver is connected with the second mixer after passing through the first low-noise amplifier, the power divider is connected with the second mixer, the output of the second mixer is used as the first output end of the radar transceiving radio frequency front end (1), the first low-noise amplifier is also connected with the third mixer, the power divider is connected with the third mixer after passing through a phase shifter, and the output of the third mixer is used as the second output end of the radar transceiving radio frequency front end (1); the second receiver is connected with a fourth mixer after passing through a second low noise amplifier, a power divider is connected with the fourth mixer, the output of the fourth mixer is used as a third output end of the radar transceiving radio frequency front end (1), the second low noise amplifier is also connected with a fifth mixer, the power divider is connected with the fifth mixer after passing through another phase shifter, and the output of the fifth mixer is used as a fourth output end of the radar transceiving radio frequency front end (1).
3. An FMCW radar-based tongue pose detection system as claimed in claim 2, wherein: the signal processing module (2) comprises four filtering amplification processing modules, four digital-to-analog converters and a voltage-controlled waveform generating and operating unit; a first output end of the radar transceiving radio frequency front end (1) is connected with a first filtering amplification processing module, and the first filtering amplification processing module is connected to the operation unit after passing through a first digital-to-analog converter; a second output end of the radar transceiving radio frequency front end (1) is connected with a second filtering amplification processing module, and the second filtering amplification processing module is connected to the arithmetic unit after passing through a second digital-to-analog converter; a third output end of the radar transceiving radio frequency front end (1) is connected with a third filtering amplification processing module, and the third filtering amplification processing module is connected to the operation unit after passing through a third digital-to-analog converter; a fourth output end of the radar transceiving radio frequency front end (1) is connected with a fourth filtering amplification processing module, and the fourth filtering amplification processing module is connected to the operation unit after passing through a fourth digital-to-analog converter; the operation unit is connected with the control end of the voltage-controlled waveform generation module, and the output end of the voltage-controlled waveform generation module is connected with the control end of the voltage-controlled oscillator.
4. An FMCW radar-based tongue pose detection system as claimed in claim 1, wherein: the radar transceiving radio frequency front end (1) is a millimeter wave FMCW radar.
5. An FMCW radar-based tongue pose detection system as claimed in claim 1, wherein: the identification module (3) is a computer terminal.
6. An FMCW radar-based tongue pose detection system as claimed in claim 3, wherein: the filtering amplification processing module comprises a preposed low noise amplifier, a high pass filter, a variable gain amplifier and a low pass filter.
7. The FMCW radar-based tongue pose detection method applied to the tongue pose detection system of any one of claims 1-6, wherein:
the transmitting end of the radar transceiving radio frequency front end (1) has three transmitting states, each receiver in the receiving end of the radar transceiving radio frequency front end (1) receives three groups of receiving signals, finally the radar transceiving radio frequency front end (1) outputs six groups of IQ intermediate frequency signals, the signal processing module (2) demodulates and calculates each group of IQ intermediate frequency signals to obtain Doppler frequency shift change data and transmits the Doppler frequency shift change data to the identification module (3), the identification module (3) calculates complex tongue motion characteristics in the Doppler frequency shift change data, the complex tongue motion characteristics are used for classifying the Doppler frequency shift change data, intelligent tongue gesture recognition is achieved, results are transmitted to the terminal interface (4), and finally the results are displayed through the terminal interface (4);
the identification module (3) feeds back the complex tongue motion characteristics corresponding to the Doppler frequency shift change data to the operation unit of the signal processing module (2), and the operation unit judges the motion state of the detected tongue according to the fed back complex tongue motion characteristics and simultaneously calculates the distance between the detected tongue and the radar transmitting and receiving radio frequency front end (1) so as to determine the motion process of the detected tongue; according to the motion process of the detected tongue, the operation unit outputs the optimal emission parameter of the emission end in the motion process, and the voltage control waveform generation module changes the generated voltage shape, so that the emitted FMCW radar signal is changed.
8. The FMCW radar-based tongue pose detection method of claim 7, wherein: the transmission parameter is specifically parameter a of FMCW radar signal T (t)1、a2、a3、b1、b2、b3C, the formula is as follows:
T(t)＝a1sin b1t+a2sin b2t+a3sin b3t+c＝ATcos(2πftt)
wherein, a1、a2、a3、b1、b2、b3C are constants, ATRepresenting the amplitude, f, of the transmitted FMCW radar signaltRepresenting a transmission frequency of a transmitted FMCW radar signal;
the operation unit adjusts the parameter a according to the feedback tongue complex motion characteristic1、a2、a3、b1、b2、b3C, the value of the parameter a1、a2、a3、b1、b2、b3C to the voltage-controlled waveform generation module, thereby enabling the transmission frequency ftA change occurs.
9. The FMCW radar-based tongue pose detection method as claimed in claim 8, wherein: the feedback tongue complex motion characteristics comprise amplitudes of two paths of I echo signals I (t) and two paths of Q echo signals Q (t) in IQ intermediate frequency signals
Figure FDA0002851245870000031
Phase phi and Doppler frequency fdThe formulas of the I echo signal I (t) and the Q echo signal Q (t) are as follows:
Figure FDA0002851245870000032
Figure FDA0002851245870000033
wherein A isTRepresenting the amplitude, A, of the transmitted FMCW radar signalR(t) amplitude of received FMCW radar return signals, fdThe Doppler frequency of the received FMCW radar echo signal is shown, and phi is the phase formed by the distance between the tongue and the radar transmitting and receiving radio frequency front end (1) in the initial state.
10. The FMCW radar-based tongue pose detection method as claimed in claim 9, wherein: the Doppler shift fdSatisfy fd＝fr-ftWherein f istRepresenting the transmission frequency, f, of transmitted FMCW radar signalsrRepresenting a reception frequency of a received FMCW radar echo signal;
and a transmission frequency ftAnd a reception frequency frSatisfies the following relationship:
Figure FDA0002851245870000034
where c represents the speed of light and v represents the speed of tongue movement.
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