CN115240438A - Detection system for judging whether children leave over in car - Google Patents
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- G—PHYSICS
- G08—SIGNALLING
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- G08G1/00—Traffic control systems for road vehicles
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- G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
- B60Q9/00—Arrangement or adaptation of signal devices not provided for in one of main groups B60Q1/00 - B60Q7/00, e.g. haptic signalling
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- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R21/00—Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
- B60R21/01—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents
- B60R21/015—Electrical circuits for triggering passive safety arrangements, e.g. airbags, safety belt tighteners, in case of vehicle accidents or impending vehicle accidents including means for detecting the presence or position of passengers, passenger seats or child seats, and the related safety parameters therefor, e.g. speed or timing of airbag inflation in relation to occupant position or seat belt use
- B60R21/01512—Passenger detection systems
- B60R21/0153—Passenger detection systems using field detection presence sensors
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B3/00—Audible signalling systems; Audible personal calling systems
- G08B3/10—Audible signalling systems; Audible personal calling systems using electric transmission; using electromagnetic transmission
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- G08G—TRAFFIC CONTROL SYSTEMS
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Abstract
The invention relates to a technology for detecting children left in a car, in particular to a detection system for judging whether children are left in the car, which is designed by taking a single chip microcomputer development board as a main controller and combining a millimeter wave radar detection system, a car internal environment monitoring system, an Ali cloud server and an MQTT protocol so as to solve the problems mentioned in the background technology; the child safety monitoring system comprises a vehicle state judgment module, a child sign monitoring module, an AHT10 temperature sensor and a single chip microcomputer development board, wherein the vehicle state judgment module comprises a 24GHz millimeter wave radar for monitoring a driver seat; 24GHz millimeter wave radar is connected with singlechip development board, and children's sign monitoring module is for judging according to children breathing and the particularity of rhythm of the heart whether to be children and monitor the 60GHz millimeter wave radar of children's vital sign situation, 60GHz millimeter wave radar is connected with singlechip development board, still including the AHT10 temperature sensor who is used for measuring the interior temperature of car, and AHT10 temperature sensor also is connected with singlechip development board.
Description
Technical Field
The invention relates to a technology for detecting children left in a car, in particular to a detection system for judging whether children are left in the car.
Background
EuroNCAP announces that since 2022 it will begin to score the detection of carry-over in a buggy, the main role of this function is: it can be detected that the child is left in the car alone and give an alarm to the car owner or emergency services to avoid heatstroke death. This means that every new vehicle sold in europe to begin a five-star rating in 2022 now begins to consider the development of the above-described functionality. At present, many parts suppliers around the world are concerned with the development of the above functions, and rely on vision (camera) or radar sensors to detect whether there is a person in the rear seat on the basis of the original door and seat sensors. Seat sensor based solutions, seat belt like alarm systems; a camera-based solution, which extends from driver monitoring to full cabin monitoring, is at risk of personal privacy being compromised; the third is based on millimeter wave radar, which is currently considered a promising solution.
The in-vehicle life sensing device is invented by researchers at university of Luolu, lu, canada, combines a millimeter wave radar and an artificial intelligence technology, and can accurately detect unwatched children or animals in a vehicle.
The device is subsidized by automobile part manufacturers at the end of 2020 and is already put on the market.
The device can be mounted on the rear-view mirror of a vehicle or on the ceiling of the interior of the vehicle, and has a diameter of only about 3 cm. The principle of the device is very simple, the device sends out radar signals during working, and people, animals or other objects on the vehicle reflect the signals back to the signals, and then the signals are analyzed and processed by an artificial intelligence system in the device.
The device is mainly used for detecting whether a left child or a pet exists in the car or not and preventing the tragedy that the child is suffocated in the car from happening frequently. When the device detects a child or pet left in the car, the system will prevent the car door from locking and alarm to alert the driver, passengers or surrounding people.
The device distinguishes whether an object is alive or not by detecting fine breath, can be powered by a vehicle battery, and is low in power consumption. GeorgeShaker, professor GeorgeShaker, the designer of the device, believes that the device is smaller and less expensive than other similar products, and that almost all vehicles can be equipped, which can solve a serious problem in the world.
Unlike a camera, a radar can penetrate the seat to determine if an infant is present on the rear seat of the vehicle. Thus the device does not have any blind area and protects privacy.
At present, china has held the on-line release meeting of the vital sign monitoring technology in the 6-month-8-day great wall automobile in 2020, and the vital sign monitoring technology is released. Different from the ultrasonic radar used before, the great wall automobile vital sign detection technology adopts the millimeter wave radar with higher precision, better performance, stronger anti-interference capability and better penetration capability, can effectively eliminate interference theoretically, detects vital signs in automobiles, and verifies that the working environment of the technology can be-40 ℃ to +85 ℃.
Even if the vehicle is in a flameout state, a door and window are closed and the vehicle is in a locked state, the vital sign monitoring system can still detect the life of the living body on the back row in the vehicle through the millimeter wave radar. The living body that can be detected includes children, pets, and the like, while also avoiding minute creatures such as mosquitoes. Once the system detects that there is living life in the car to wait for 30s after the vehicle nobody gets into, the system will remind the car owner and ask for help passerby through forms such as warning light (two sudden strain of a muscle), whistle and WEY way cell-phone APP, SMS propelling movement. If the vehicle door is unlocked during the reminding period, the vehicle stops warning, otherwise, the reminding of the vehicle whistle and the warning light lasts for 30min, and the interval frequency is 1 min/time.
At present, china has already many research schemes to solve the safety problem that children stay in a car: some people have developed a child anti-retention monitoring system based on a face recognition technology, and the system takes an age recognition algorithm as a core and uses a sensor to assist in monitoring the environment in a vehicle. And a monitoring system based on a wireless sensor network is designed by fusing a temperature detection module, an infrared CO2 detection module, a Hall sensor, an LCD module and a GSM module. Still others have designed a detection device to gather the signals of pressure sensitive cushion infrared alarm and door lock sensor, and then transmit the signals to actuating devices such as window regulator and audible and visual alarm.
In conclusion, the key and focus of the research on solving the safety problem of children staying in the car in China is how to well combine various sensors and remote alarm.
Disclosure of Invention
Aiming at the problems in the background art, the invention aims to provide a detection system for judging whether children are left in a car or not, which is designed by taking a single chip microcomputer development board as a main controller and combining a millimeter wave radar detection system, an in-car environment monitoring system, an Aliskiu server and an MQTT protocol so as to solve the problems in the background art.
The technical purpose of the invention is realized by the following technical scheme: a detection system for judging whether children are left in a car or not comprises a car state judgment module, a child sign monitoring module, an AHT10 temperature sensor and a singlechip development board, wherein the car state judgment module comprises a 24GHz millimeter wave radar for monitoring a driver seat; 24GHz millimeter wave radar is connected with singlechip development board, and children's sign monitoring module is for breathing and the particularity judgement of rhythm of the heart whether be children and monitor the 60GHz millimeter wave radar of children's vital sign situation according to children, 60GHz millimeter wave radar is connected with singlechip development board, still including the AHT10 temperature sensor who is used for measuring the interior temperature of car, AHT10 temperature sensor also is connected with singlechip development board, singlechip development board still is connected with display screen Lcd and bee calling organ and the cell-phone APP that is used for alarm notification respectively.
Preferably, the singlechip development board can be an Mpython-I development board.
Preferably, the 60GHz millimeter wave radar may be composed of a yunrireda R24AVD1 biosensing radar and a R60ABH1 breathing heartbeat radar.
Preferably, the frequency of the 60GHz millimeter wave radar increases linearly with time, the waveform is a chirped continuous time domain waveform,
in the formula: f. of c -an initial frequency; b-radar waveform bandwidth; t is c -a pulse width of the chirp signal; t-time;
the formula of the radar emission signal is
In the formula: a. The T -an amplitude of the transmit signal; phi (t) -phase noise of the transmitter bits;
through the time delay caused by the distance, the signal received by the radar changes, and the formula also changes into
In the formula: attenuation of signal amplitude during alpha-propagation; t is t d -time delay, t d =2R (t)/c, R (t) -the radial distance between the radar and the object, which value varies constantly for moving objects; c-speed of light; the radar receiver carries out coherent mixing on the radar transmitting signal and the radar receiving signal, and the signal after I/Q demodulation is represented as
In the formula: a. The R -the power of the received signal; f. of b -the frequency of the beat signal B (t); phi is a b (t) -the phase of the beat signal B (t); wherein f is b ，φ b (t) can be represented by the following formulae (5) and (6),
residual signal noise when the radar is close to the detection target
Can be ignored; in addition, due to
The numerical values are small in practical applications and can therefore be omitted in their expressions. Thus, the expression between the change in distance and phase between the radar and the measured target is:
in the formula, delta phi b -a change in phase; Δ R-the change in displacement caused by the heart or thorax.
Preferably, the AHT10 temperature sensor has a temperature measurement range of-40 ℃ to +85 ℃, an accuracy of + -0.5 ℃, a humidity measurement range of 0% to 100%, an accuracy of + -3% RH. The conversion formula is as follows:
in the formula: t-temperature (. Degree. C.); ST-temperature output signal.
In the formula: RH-relative humidity; SRH — relative humidity output signal.
Preferably, the main control chip adopted by the Mpython-I development board is a W601Wi-FiMCU chip which is an SoC chip supporting a multifunctional interface, the SoC chip integrates a Cortex-M3 kernel, is internally provided with Flash and supports SDIO, SPI, UART, GPIO, I2C, PWM and I 2 S, 7816, LCD and ADC interface.
In summary, the invention mainly has the following beneficial effects: the system uses the self-developed Mpython-I development board, abandons the traditional scheme of judging the vehicle state by an acceleration sensor and a GPS module, and changes the scheme into a mode of indirectly judging the vehicle state by selecting a 24GHz millimeter wave radar; an AHT10 temperature sensor with higher usability and price ratio is used for monitoring the environmental temperature in the vehicle; in the aspect of detecting the vital signs of children, a 60GHz breathing heartbeat millimeter wave radar with higher precision and higher safety is selected to reduce the false alarm rate and improve the accuracy rate of human body detection. In the data transmission function of the system, a WiFi module carried by a development board is selected, and various data in the vehicle and human bodies are transmitted to an Ali cloud server through an MQTT protocol. When the alarm module triggers, the passive buzzer of the development board alarms, the Ali cloud server sends data to the car owner APP to be displayed in real time, and the mobile phone vibration alarm is triggered.
In order to ensure that the whole final system can stably and smoothly operate, the main sub-modules of the system are tested independently, wherein the main sub-modules comprise a millimeter wave radar detection module, an AHT10 temperature detection module, an Aliskiren data uploading module and an alarm module. And after the system is assembled, testing the whole function of the system. Through integral test and optimization, the system achieves the expected main design target and makes up the defects in the design of the existing detection system for the left in the baby carriage.
Drawings
FIG. 1 is a system block diagram;
FIG. 2 is a schematic diagram of a frequency domain waveform of a chirp continuous wave;
FIG. 3 is a schematic diagram of a time domain waveform of a chirped continuous wave;
FIG. 4 is a schematic diagram of the data exchange principle of the MQTT protocol;
FIG. 5 is a schematic diagram of an MCU;
FIG. 6 is a schematic diagram of a power supply circuit;
FIG. 7 is a schematic diagram of a reset circuit;
FIG. 8 is a buzzer circuit diagram;
FIG. 9 is a circuit diagram of a liquid crystal display;
FIG. 10 is a schematic diagram of USB to TTL and MicroUSB interfaces;
FIG. 11 is a schematic diagram of the R24AVD1 circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Currently, most automobile companies are focusing on developing seats special for children in automobiles, and the seats are generally added with some unique functions to realize functions of monitoring and protecting children. The seat sensor belongs to a film type contact sensor, contacts on the sensor are uniformly distributed on a stressed surface of the seat, and when external pressure acts on the seat, a trigger signal is generated.
The sensor is mostly applied to a vehicle passenger monitoring system, for example, whether a driver leaves or not, safety belt alarming, safety airbag sensing, automatic taxi charging and the like are judged, the device can monitor whether a person is on a driving seat or not, if no person exists, a vehicle clutch can automatically return to a neutral gear, and an airbag cannot be opened. In addition, the shape of the sensor and the sensitivity of the contact thereof can also be changed according to the hardness, the shape and the tightness of the outer skin of the automobile seat.
Researchers combine the sensing technology, the single chip microcomputer control technology and the wireless communication technology, and a vibration sensor, a pressure sensor, a telephone dialing module and the like are additionally arranged on the child safety seat to prevent children from being left in a vehicle. The system uses a vibration sensor to detect the running state of the vehicle, and uses a pressure sensor to judge whether a child is in the vehicle. When the vibration sensor detects that the automobile has no vibration, namely the automobile stops, the pressure sensor works, and if the pressure detected on the safety seat exceeds 5 kilograms, it is judged that a child is left in the automobile.
By adopting the scheme of the seat sensor, when a child sits on the special seat for the child, the existence information of the child can be accurately detected, and the parents can be informed of the alarm information in time by modules such as a telephone dialing module and the like. However, when more than 5 kg of articles are stacked on the seat or other adults sit on the seat temporarily, the system also judges that a child is present, and thus a false alarm occurs. In addition, a plurality of children can move well, and the phenomena that the children are separated from the safety belt and leave the seats of the children do not occur, so that the seat sensor can not detect the existence of the children under the condition, and the expected effect can not be achieved.
Cameras have been ever more recent as the most common detection tool and now cover almost every corner of our lives. The OpenMV camera is a circuit board which is combined with a singlechip and has the advantages of light weight, low power consumption and low cost, and can easily complete a module for machine vision application. OpenMV carries a Python interpreter, which means that it can be programmed in Python language on an embedded device to handle a variety of complex outputs. The machine vision algorithm is simplified by Python programming, allowing even beginners to enter quickly. The user can easily use the external terminal to execute the algorithm or trigger the shooting instruction, and the I/O pin can be controlled by the algorithm result.
Therefore, researchers use the STM32 single chip microcomputer as a main control, and a children retention detection system in the car is designed by adopting a camera, a GPS, an accelerometer and the like. The system detects the parking of the vehicle through a GPS, an accelerometer and the like, and detects the existence of children through a camera and a Haar operator. The OpenMV embedded machine vision module is applied to camera face detection, and the face monitoring is carried out through a built-in HaarcCascade feature detector.
The scheme is mainly used for the vehicle-mounted camera, and the advantages and the disadvantages of the scheme are obvious. The system can almost monitor the conditions in the vehicle in all directions without dead angles, and can enable the mobile phone end to check at any time and any place through a program. The children can be accurately judged through the OpenMV designed by the human face, and the false alarm caused by the riding of adults can be avoided. However, the OpenMV camera has low pixels, is not suitable for performing some complex algorithms such as deep learning, and the like, and optical conditions can seriously affect the performance of the camera, possibly causing false alarm, and in addition, the scheme has the risk that private persons are leaked.
The millimeter wave radar is a detection radar working in a millimeter wave band, and the frequency domain is 30-300 GHz. The wavelength of the radar is between centimeter wave and microwave, and the advantages of the photoelectric radar and the microwave radar are integrated. Compared with other seeker, the millimeter wave seeker has the advantages of light weight, small size, small spatial resolution and effective penetration of smoke and dust. In addition, the millimeter wave radar also has the advantages of being capable of distinguishing small targets, identifying a plurality of targets, being good in concealment and mobility, capable of imaging and the like, and therefore the radar is mainly used in the military field in the early stage. With the continuous development of the technology in the automobile field, the radar is gradually applied to the automobile.
At present, 24GHz and 77GHz millimeter wave radars are mainly used on automobiles, and both the radars can be used for long-distance and short-distance detection of an ADAS system. The 24GHz radar is mostly arranged in a rear bumper of the vehicle and used for monitoring whether a lane behind the vehicle follows the vehicle or not and whether lane changing can be carried out or not. Because the detection distance and the accuracy of the 77GHz radar are better than those of the 24GHz radar, the 77GHz radar is mainly assembled on a front bumper of a vehicle to detect the speed and the distance of a front vehicle, and can assist in realizing the functions of automatic vehicle following, automatic driving and the like.
Researchers put forward that the millimeter wave radar can be used in a vehicle to detect the existence of children, the beat frequency signals obtained by radar frequency mixing are subjected to distance dimension Fourier transform, the distance range of the object to be detected is determined, and phase information of the distance range is extracted to be subjected to differential processing. Then, signals such as respiration, heartbeat and the like are separated by using a filter, and the physical signs of the children are evaluated by Fourier transform.
The detection scheme skillfully makes up the defects of the schemes, not only can realize the detection of the full coverage of the vehicle rear seat without being interfered by other objects, but also can not be limited by optical conditions, thereby greatly reducing the false alarm rate. Because millimeter wave radar can more accurately detect human breathing and rhythm of the heart, consequently also can distinguish adult and children according to the characteristics that children breathing, rhythm of the heart are different with adult, reduced the interference equally. Although the radar has the defects of higher cost of components, higher requirement on processing precision, slower development of a single chip transceiver integrated circuit and the like, the scheme is still regarded as the most promising scheme at present.
Through the comparison of the vital sign detection schemes, the overall scheme of the system is determined according to the target to be completed by design. The in-vehicle child detection system designed by the method comprises three modules, namely vehicle state judgment, in-vehicle environment detection and alarm notification. The vehicle state judgment module mainly uses a 24GHz millimeter wave radar to monitor the driver seat, and if the millimeter wave radar detects that the driver seat is unmanned and the acceleration of the vehicle is small, the vehicle is judged to be stopped. The in-vehicle environment monitoring module is composed of an AHT10 temperature sensor and a 60GHz millimeter wave radar, the AHT10 temperature sensor is used for measuring the in-vehicle temperature, and the 60GHz millimeter wave radar is used for monitoring the backseat child to form a child sign monitoring module. This radar can judge whether have children to exist according to motion information, judges whether for children and monitoring children's vital sign situation according to children's breathing and the particularity of rhythm of the heart again. And finally, an alarm notification module is formed by a buzzer and a mobile phone remote alarm, the single chip microcomputer is used for processing in-vehicle information and alarm information and then is connected to the Aliskian platform by using an MQTT protocol, and further is sent to a mobile phone end APP. The frame diagram is shown in figure 1. After the product is assembled and tested, the shell of the product is printed out by using a 3D printing technology, and the product is packaged and protected.
Used in this paper are yunshirida R24AVD1 biosensing radar and R60ABH1 breathing heartbeat radar. The radar is a self-organized air-isolation perception sensor, a module is formed by combining a radio frequency antenna, a radar chip and a high-speed main frequency MCU together, various scene detection requirements of users are met by relying on a stable, flexible and superior algorithm architecture core, an upper computer or a host can be carried to flexibly output detection states and data, and the requirements of several groups of GPIOs (general purpose input/output) can be customized and developed by the users.
The radar transmits millimeter wave signals, a target to be detected reflects the electromagnetic wave signals, the transmitted signals are demodulated, and then the signals are amplified, filtered, ADC and the like to obtain echo demodulation signal data. And the amplitude, the frequency and the phase of the echo signal are resolved in the MCU unit, and finally target parameter (respiration, motion, micromotion and the like) measurement and scene evaluation are realized.
The frequency of the millimeter wave respiration heartbeat radar is increased linearly along with the increase of time, and the waveform is a linear frequency modulation continuous wave. Fig. 2 shows a frequency domain waveform of a chirped continuous wave, which is a straight line and can be represented by equation (1). Fig. 3 is a time domain waveform of a chirped continuous wave.
In the formula: f. of c -an initial frequency; b-radar waveform bandwidth; t is c -the pulse width of the chirp signal; t-time.
The formula of the radar emission signal is
In the formula: a. The T -the amplitude of the transmitted signal; phi (t) -phase noise of the transmitter bits.
Through the time delay caused by the distance, the signal received by the radar changes, and the formula also changes into
In the formula: attenuation of signal amplitude during alpha-propagation; t is t d -time delay, t d =2R (t)/c, R (t) -the radial distance between the radar and the object, which value would not be true for a moving objectStopping changing; c-speed of light. The radar receiver carries out coherent mixing on the radar transmitting signal and the radar receiving signal, and the signal after I/Q demodulation is represented as
In the formula: a. The R -the power of the received signal; f. of b -the frequency of the beat signal B (t); phi is a b (t) -the phase of the beat signal B (t). Wherein f is b ，φ b (t) can be represented by the following formulae (5) and (6),
residual signal noise when the radar is close to the detection target
Can be ignored. In addition to this, because
The numerical values are small in practical applications and can therefore be omitted in their expressions. Thus, the expression between the change in distance and phase between the radar and the measured target is:
in the formula, delta phi b -a change in phase; Δ R-the change in displacement caused by the heart or chest.
The expression is the core of the millimeter wave radar for monitoring the respiration heartbeat signal. Therefore, certain errors possibly caused to the measurement result when the user moves can be found, but the errors can eliminate false detection points caused by target movement in an indoor scene by adjusting the sensitivity of the radar or adopting a multipath interference elimination algorithm, so that the problem of false alarm caused by the fact that the false detection points are mistakenly considered as targets by the millimeter wave radar sensor to be tracked and output is avoided.
The system is used for collecting environmental information in the vehicle and is provided with an AHT10 temperature and humidity sensor. AHT10 is a new generation of temperature and humidity sensors that establish new standards in terms of both size and performance. The dual-row flat pin-free SMD package suitable for reflow soldering is embedded, and output digital signals are calibrated and in a standard I2C format. The AHT10 uses a newly designed ASIC dedicated chip, an improved MEMS semiconductor capacitive humidity sensor and a standard on-chip temperature sensor, and the performance thereof is greatly improved even more than the previous generation sensors. Meanwhile, the performance of the improved new-generation temperature and humidity sensor is stable in severe environment, and the improved new-generation temperature and humidity sensor is widely applied to places such as dehumidifiers, automobiles, household appliances, medical treatment, heating, ventilating and air conditioning and the like.
Compared with a DHT11 temperature and humidity sensor, the AHT10 has higher precision, higher response speed, stronger anti-interference capability and higher cost performance. AHT10 has a temperature measurement range of-40 ℃ to +85 ℃, an accuracy of + -0.5 ℃, a humidity measurement range of 0% to 100%, an accuracy of + -3% RH. The conversion formula is as follows:
in the formula: t-temperature (. Degree. C.); ST-temperature output signal.
In the formula: RH-relative humidity; SRH — relative humidity output signal.
The full name of MQTT is MessageQueuingTelememtyTransport, which is a protocol for message queue transmission. The protocol is based on transmission on a TCP/IP protocol, a subscription and publishing mechanism is applied, and a subscriber only receives data subscribed by the subscriber and does not receive non-subscribed data. This ensures the necessary exchange of data and avoids storing and processing invalid data.
As shown in fig. 4, MQTT is the OASIS standard. The specification is managed by the oassismqtt technical committee. Over the years of development, release 5.0 has been reached by 2021. The MQTT has the greatest advantage of providing real-time reliable messaging services to remote devices with very little code and limited bandwidth. As an instant messaging protocol with low cost and low bandwidth occupation, the MQTT has wide application in the aspects of Internet of things, small-sized equipment, mobile application and the like. For example, in the automotive industry, EMQ helps the public at the mercy to build the IoT platform; in the intelligent household field, the intelligent control of the mobile phone to the household can be realized through the Internet of things. The MQTT protocol brings possibility for realizing intellectualization and brings great convenience to life.
The goal of the MicroPython is to be as compatible as possible with the common Python, allowing the user to easily transfer code from the desktop to the microcontroller or embedded system. Generally, the development board not only supports UART0 to carry out MicroPython command line interaction and most MicroPython characteristics and internal libraries (unicode, high-precision integer, single-precision floating point number, complex number and the like), but also supports hardware GPIO, UART, SPI, I2C, PWM, WDT, ADC, RTC, timer and other modules, and can use a WiFi network module (including a one-key distribution network function) and SSL to use hardware for encryption and decryption.
The master control chip adopted by the Mpython-I development board is a W601Wi-FiMCU chip which is an SoC chip supporting a multifunctional interface. The intelligent household appliance can be used as a main control chip and applied to the fields of Internet of things such as intelligent household appliances, intelligent houses, intelligent toys, medical monitoring and industrial control.
The SoC chip integrates Cortex-M3 kernel, is internally provided with Flash, and supports SDIO, SPI, UART, GPIO and I 2 C、PWM、I 2 The system comprises an S interface, a 7816 interface, an LCD interface, an ADC interface and the like, and supports various hardware encryption and decryption protocols, such as PRNG/SHA1/MD5/RC4/DES/3DES/AES/CRC/RSA and the like; integrated radio frequency transceiver front end RFTransceiver, PA power amplifier, baseband processor/media access control. It is provided withThe MCU schematic is shown in fig. 5.
Before writing a system code program, the requirements to be met and the functions to be realized by the program need to be clarified, an overall framework is formed, and the whole system is divided into a plurality of parts. The method comprises the steps of defining partial programs of each data acquisition device, a buzzer and the like to form each subfunction, writing the subfunctions into a main program of a main frame, and directly calling each subprogram completed before to form a logic relation to complete expected requirements.
The main functions to be realized by the program of the system are as follows:
(1) WiFi network and MQTT protocol
(2) And judging the running state of the vehicle.
(3) And detecting the temperature in the vehicle.
(4) If the temperature is detected to be too high and a child is in the car, data are uploaded to Ariiyun, and the buzzer gives an alarm.
After the system designed by the text is initialized, the existence condition of a driver of an automobile driver seat can be detected by the 24GHz millimeter wave radar, if the driver seat is not provided with any person, a pin of the 24GHz millimeter wave radar can output a low level, and a program judges that the automobile is in a stop state. And then the temperature sensor collects the environmental temperature in the vehicle, the 60GHz millimeter wave radar scans and detects the rear seat of the vehicle, and the heart rate and the respiration value of the child are generally higher than those of an adult, so that if the heart rate and the respiration value of the personnel in the rear seat are detected to be more than 100 times/min and more than 20 times/min, the child is judged to be left in the vehicle. If the temperature is higher than the limit value, the buzzer alarms locally and the development board seeks connection with WiFi and MQTT protocols. After connecting WiFi and MQTT agreement, upload temperature and children's breathing, rhythm of the heart in the car to the Ali cloud, send these information to cell-phone APP by Ali cloud again, can real-time update the information received and carry out vibrations after cell-phone APP connects the server and report to the police. The flowchart of the whole system is shown in fig. 6.
The system converts the problem of judging the vehicle state into detecting whether a driver is on the vehicle in a driver seat. If the driver's seat is unmanned, it is determined that the vehicle is stopped. According to the definition of the 24GHz millimeter wave radar pin, if the S1 pin outputs low level, it is indicated that the driver seat is unmanned, otherwise, if the driver seat is unmanned, the program is not executed. Therefore, only the high and low levels of the GPIO port connected to the S1 are needed to be detected, and meanwhile, the high and low levels are observed by converting the high and low levels into the visible on-off of the LED lamp on the development board for convenient judgment in debugging. The flow chart is shown in fig. 7.
The in-vehicle environment detection program mainly works for detecting the environment temperature and the information of the back seat personnel in the vehicle, and when the in-vehicle temperature exceeds an upper limit value and the heart rate and the respiration value of the back seat personnel are in a problem, the alarm program is activated and the acquired environment data are uploaded. The program mainly comprises a temperature detection program and a decoding and detection program of the 60GHz millimeter wave radar. The flow chart is shown in fig. 8.
The in-vehicle environment detection program mainly works for detecting the environment temperature and the information of the back seat personnel in the vehicle, and when the in-vehicle temperature exceeds an upper limit value and the heart rate and the respiratory value of the back seat personnel are in problem, the alarm program is activated and the collected environment data are uploaded. The program mainly comprises a temperature detection program and a decoding and detection program of the 60GHz millimeter wave radar. The flow chart is shown in fig. 9.
The data of the temperature detection program, the AHT10 temperature module used by the system, needs to be transmitted by using an I2C bus protocol, and data conversion is carried out by reading I2C. The sensor reading process comprises the following steps:
(1) After power-on, it waits for 40ms, before reading the temperature and humidity value, first, it needs to see if the calibration enable Bit of the status word is 1 (a byte of the status word can be obtained by sending 0x 71), if not, it needs to send a 0XE1 command (initialization), the parameter of the command has two bytes, the first byte is 0x08, and the second byte is 0x00.
(2) The 0xAC command (trigger measurement) is sent directly, and the command parameter has two bytes, the first byte is 0x33, and the second byte is 0x00.
(3) Wait for 80ms to be measured, busy status Bit is 0, and then six bytes can be read (0X 71 is sent).
The program calls an AHT10 decoding program from a MicroPython library of VScode, then selects SDA and SCL pins, and writes a temperature detection execution program, and the flow chart of the program is shown in FIG. 10.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. A detection system for judging whether children are left in a car or not is characterized by comprising a car state judgment module, a child sign monitoring module, an AHT10 temperature sensor and a single chip microcomputer development board, wherein the car state judgment module comprises a 24GHz millimeter wave radar for monitoring a driver seat; 24GHz millimeter wave radar is connected with singlechip development board, and children's sign monitoring module is for breathing and the particularity of rhythm of the heart according to children and judges the 60GHz millimeter wave radar of whether being children and monitoring children's vital sign situation, 60GHz millimeter wave radar is connected with singlechip development board, still including the AHT10 temperature sensor who is used for measuring the interior temperature of car, AHT10 temperature sensor also is connected with singlechip development board, singlechip development board still is connected with display screen Lcd and bee calling organ and the cell-phone APP that is used for the warning notice respectively.
2. The detection system for judging whether children are left in the car according to claim 1, wherein the single chip microcomputer development board can be an Mpython-I development board.
3. The detection system for determining whether a child is left in a vehicle according to claim 1, wherein the 60GHz millimeter wave radar may be composed of a Yunshirai R24AVD1 biosensing radar and a R60ABH1 breathing heartbeat radar.
4. The detection system for determining whether a child is left in a vehicle according to claim 1, wherein the frequency of the 60GHz millimeter wave radar increases linearly with time, the waveform is a chirp continuous time domain waveform,
in the formula: f. of c -an initial frequency; b-radar waveform bandwidth; t is c -the pulse width of the chirp signal; t-time;
the formula of the radar emission signal is
In the formula: a. The T -the amplitude of the transmitted signal; phi (t) -phase noise of the transmitter bits;
through the time delay caused by the distance, the signal received by the radar changes, and the formula also changes into
In the formula: α -attenuation of signal amplitude during propagation; t is t d Time delay, t d =2R (t)/c, R (t) -the radial distance between the radar and the object, which value varies constantly for moving objects; c-speed of light; the radar receiver carries out coherent mixing on the radar transmitting signal and the radar receiving signal, and the signal after I/Q demodulation is represented as
In the formula: a. The R -the power of the received signal; f. of b -the frequency of the beat signal B (t); phi is a b (t) -the phase of the beat signal B (t); wherein f is b ，φ b (t) can be represented by the following formulae (5) and (6),
residual signal noise when the radar is close to the detection target
Can be ignored; in addition to this, because
The numerical values are small in practical applications and can therefore be omitted in their expressions. Thus, the expression between the change in distance and phase between the radar and the measured target is:
in the formula, delta phi b -a change in phase; Δ R-the change in displacement caused by the heart or thorax.
5. The detecting system for determining whether a child is left behind in a car according to claim 1, wherein the AHT10 temperature sensor has a temperature measuring range of-40 ℃ to +85 ℃, an accuracy of ± 0.5 ℃, a humidity measuring range of 0% to 100%, and an accuracy of ± 3% rh. The conversion formula is as follows:
in the formula: t-temperature (. Degree. C.); ST-temperature output signal.
In the formula: RH-relative humidity; SRH — relative humidity output signal.
6. The system of claim 1, wherein the Mpython-I development board has a W601Wi-FiMCU chip as a main control chip, the chip is an SoC chip supporting a multifunctional interface, the SoC chip integrates a Cortex-M3 core, is embedded with Flash, and supports SDIO, SPI, UART, GPIO, I 2 C、PWM、I 2 S, 7816, LCD and ADC interface.
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