Paddy field water level monitoring system based on throw-in type liquid level transmitter and electrode induction plate

Abstract

The invention discloses a paddy field water level monitoring system based on a throw-in type liquid level transmitter and an electrode induction plate. Comprising a main processor module, and a throw-in type liquid level transmitter, an electrode induction plate, a lightning protection and protection module, a voltage transformation and stabilization module, an LCD screen display module, a basic current comparison module, a 2.5 V voltage reference module, a 485 signal communication module, a temperature and humidity monitoring module, a FLASH storage module, a 4G communication module and a watchdog monitoring module which are connected to the main processor module. According to the system and the method, on the basis of the throw-in type liquid level transmitter and the electrode induction plate, the water level of the paddy field can be accurately and effectively monitored. The system is high in monitoring precision and can realize remote uploading of data.

Description

Technical Field

[0001] The invention belongs to the technical field of monitoring the permeability of cultivated soil layers, and in particular relates to a paddy field water level monitoring system based on an immersion type liquid level transmitter and an electrode sensing plate. Background Art

[0002] Land consolidation can effectively increase the area of ​​arable land, but the quality detection of newly reclaimed arable land after land consolidation (such as permeability detection) often lacks efficient and quantitative testing methods. The arable land for aquatic plant cultivation needs to have sufficient water sources, which must have both water retention capacity and certain water permeability. Therefore, it is imperative to explore the detection technology of arable land soil permeability.

[0003] Based on water level detection, the algorithm can calculate the infiltration capacity of cultivated land. The principle of water level detection technology based on image recognition is to construct a perspective projection relationship through manually set identification points, and use the color characteristics of the water gauge and image processing to calculate the water surface at the water gauge identification position. The principle of water level detection technology based on radar recognition is to transmit radar electromagnetic waves through the antenna. These electromagnetic waves will be reflected when encountering the water surface. Part of the reflected signal is received by the radar. The distance between the radar and the water surface is calculated by the time difference from transmission to reception and the propagation speed of the electromagnetic wave in the air; however, due to the reflection and scattering effects of electromagnetic waves, it is difficult to ensure the measurement accuracy and stability during long-term use, and regular maintenance and calibration are required. The principle of water level detection technology based on electrode plate recognition is that the conductive electrode contacts the liquid surface to cause a change in capacitance, triggering induction for recognition; its accuracy is determined by the spacing between the electrode plates (from the current process, the minimum can be 5mm), and it has the advantages of simple structure and strong anti-interference ability.

[0004] As is known to all, the liquid in the paddy field has a large turbidity, and its density changes with a gradient along the height. It can be seen that the method of calculating the water level based on water pressure measurement will have a large error. Therefore, in order to accurately monitor the water level of the paddy field and accurately calculate its permeability, the present invention proposes a paddy field water level monitoring system based on a submersible liquid level transmitter and an electrode sensing plate, which can provide a more accurate water level change value. Summary of the invention

[0005] In order to solve the defects and shortcomings in the above-mentioned prior art, the present invention provides a paddy field water level monitoring system based on a immersion liquid level transmitter and an electrode sensing plate, which is used to accurately measure the water level and provide real-time feedback of water level changes through a remote transmission system to achieve the purpose of paddy field water level monitoring.

[0006] The technical scheme of the present invention is as follows: a paddy field water level monitoring system based on an immersion liquid level transmitter and an electrode sensing plate, comprising a main processor module and an immersion liquid level transmitter connected to the main processor module, an electrode sensing plate, a lightning protection and protection module, a voltage transformation and voltage stabilization module, an LCD screen display module, a basic current comparison module and a 2.5V voltage reference module, a 485 signal communication module, a temperature and humidity monitoring module, a FLASH storage module, a 4G communication module and a watchdog monitoring module;

[0007] The immersion type liquid level transmitter is used to provide a water level output in the form of current, and the water level is positively correlated with the current;

[0008] The electrode sensing plate outputs high / low levels through electrodes of different heights;

[0009] The lightning protection and protection module prevents damage to components due to excessive power input signals, and prevents damage to equipment due to lightning strikes during outdoor operations.

[0010] The LCD screen display module is used to display the current water level, temperature and humidity of the system and the measured water level value;

[0011] The basic current comparison module and the 2.5V voltage reference module provide a comparison reference for the current output by the submersible liquid level transmitter to ensure the measurement accuracy of the system, and provide a precise voltage for the main processor module.

[0012] The 485 signal communication module provides the same protocol for information communication between the main processor module and the electrode sensing board;

[0013] The temperature and humidity monitoring module, on the one hand, serves as the output of paddy field environmental parameters, and on the other hand, reduces the influence of temperature and humidity through filtering algorithms to provide more accurate water level values;

[0014] The FLASH storage module is used to store various types of data received by the main processor;

[0015] The 4G communication module is used to provide a 4G remote data upload function;

[0016] The watchdog monitoring module provides a convenient restart method for system programs that are accidentally stuck;

[0017] The main processor module is used to process information transmission between modules.

[0018] Preferably, the current range is 4-20mA, the module receives the current signal output by the sensor that is positively correlated with the water level, and uses a differential comparison circuit to eliminate the current error generated in the process of transmitting the current from the immersion liquid level transmitter to the main processor; the main processor module adds a 32.768KHz crystal oscillator to provide a more accurate original clock frequency for the main processor, so that the sampled signal can be effectively analyzed and processed inside the main processor, ensuring the reliability of the paddy field plow bottom water level monitoring system and enhancing interactivity; the electrode sensing board uses a polling method to periodically query the high and low level changes of each electrode, and regards the highest high level electrode position as the water level position and outputs it to the main processor module; the voltage transformation and voltage stabilization module provides a stable 3.3V voltage for conventional circuits and a 3.8V voltage for 4G circuits.

[0019] Preferably, the water level calculation process of the paddy field water level monitoring system is as follows: the input liquid level transmitter signal receiving module outputs 4-20mA current to the main processor module, and the current magnitude I corresponds to the sensor pressure P, that is, the water pressure magnitude, and the corresponding formula is shown in formula (1):

[0020]

[0021] Where P is the water pressure measured by the submersible level transmitter, in MPa; I is the current received by the main processor module m, in mA; I set is the actual current output by module f, which is 1mA in theory; A is the minimum current output by the signal receiving module a of the submersible liquid level transmitter, in mA; B is the range of the output current of the signal receiving module a of the submersible liquid level transmitter, in mA;

[0022] The electrode sensing plate outputs the water level signal to the main processor module after being translated by the 485 signal communication module. The module has low accuracy but high reliability and is mainly used to determine whether the immersion liquid level transmitter has any abnormal conditions. The lightning protection and protection module and the voltage transformation and voltage stabilization module jointly provide safe, reliable and stable voltage for the equipment. The LCD screen display module receives the signal from the main processor module and provides an interactive interface. The basic current comparison module and the 2.5V voltage reference module output 2.5V reference voltage and 1mA reference current to the main processor module. The FLASH storage module provides space to store historical water level, temperature and humidity, and 4G transmission information. The 4G communication module provides a means for the present invention to perform wireless data transmission. The watchdog monitoring module receives the periodic dog feeding signal of the main processor module to prevent the program from accidentally getting stuck.

[0023] Preferably, the signal receiving module of the submersible liquid level transmitter includes diodes D5, D6, D15, shunt resistors R11, R12, ground separation resistor R16, filter capacitor C8 and magnetic bead H4. The positive poles of diodes D5, D6, and D15 are respectively connected to the three submersible liquid level transmitter signals, and the negative poles are connected to the same circuit to avoid interference on the one hand, and to cut off the three signals on the other hand to prevent them from conducting with each other; one end of the shunt resistors R11 and R12 is connected to the negative pole of the diode, and one end is grounded to prevent excessive current from passing through the magnetic bead and entering the main processor module; the two ends of the ground separation resistor R16 are respectively connected to the ground and the analog ground, separating the ground noise of the digital circuit and the analog circuit and maintaining the connection between them; the two ends of the filter capacitor C8 are respectively connected to the ground and the analog ground, and the two ends of the magnetic bead H4 are respectively the negative pole of the diode and the main processor module. The function of the magnetic bead H4 and the filter capacitor C8 is mainly to filter the noise input by the submersible liquid level transmitter;

[0024] The electrode sensing board includes a comparator U3B, resistors R92 to R97, and capacitors C59 and C60. The first pin of the comparator is used as an input to receive electrode signals; the second pin of the comparator is connected to the ground through the resistor R97; the third pin of the comparator is output as a comparison signal to the main processor module; the fourth pin of the comparator is grounded; the fifth pin of the comparator is used as an input pin to receive electrode signals; the sixth pin of the comparator is connected to the ground through the resistor R94; the seventh pin of the comparator is output as a comparison signal to the main processor module; the eighth pin of the comparator is connected to the capacitor C59, and the other end of the capacitor C59 is grounded for filtering; the two ends of the resistor R92 are respectively connected to the 3.3V power supply and the sixth pin of the comparator; the two ends of the resistor R9 are respectively connected to the 3.3V power supply and the seventh pin of the comparator; the two ends of the resistor R95 are respectively connected to the 3.3V power supply and the second pin of the comparator; the two ends of the resistor R96 are respectively connected to the 3.3V power supply and the third pin of the comparator; the electrode sensing board provides phased measurement data of the electrode point position, and outputs the data in the form of RS-485.

[0025] Preferably, the lightning protection and protection module includes an original power input 12V, a power output 12V, a diode D4, filter capacitors C1, C2, transient voltage suppression diodes D1, D2, D3, an inductor L2, a ceramic chip capacitor L1, varistors MOV1-MOV3, a gas venting pipe GT1, and a fuse FS1. The two ends of the diode D4 are respectively connected to the power output 12V and the filter capacitor, and its main purpose is to prevent reverse current; the two ends of the filter capacitors C1 and C2 are respectively connected to the ground wire and the diode D4; the two ends of the transient voltage suppression diode D1 are respectively connected to the ground and the electrical ground; the two ends of the transient voltage suppression diode D2 are respectively connected to the inductor L2 and the diode D4; the two ends of the transient voltage suppression diode D3 are respectively connected to the electrical ground and the inductor L2, and are connected to the power input together with the inductor L2; the two ends of the inductor L2 are respectively connected to the diode D4 and the power input 12V; the first two ends of the ceramic chip capacitor L1 are respectively connected to the power input 12V; the first two ends of the inductor L2 are respectively connected to the power input 12V; the second ... Pin 1 is connected to the power input 12V, pin 2 is connected to the ground, pin 3 is connected to the power integrity ground, and pin 4 is connected to the original power input and connected to the battery after passing through the fuse PS1; one end of the varistor MOV1 and MOV2 is connected to the negative pole of the gas venting pipe GT1, and the other end of the former is connected to the power integrity ground, and the latter is connected to the fourth pin of the ceramic chip capacitor L1; the gas venting pipe GT1, the positive pole is connected to the electrical ground, and the negative pole is connected to the varistor MOV1 and MOV2; the fuse FS1 is responsible for connecting the fourth pin of the ceramic chip capacitor L1 to the original power input.

[0026] Preferably, the voltage transformation and voltage stabilization module includes a P-channel field effect transistor Q16, resistors R60-67, a digital transistor Q17, filter capacitors C52-C57, an inductor L5, a magnetic bead MB1, and a step-down chip U19. The left D pin of the P-channel field effect transistor Q16 is connected to the 12V power supply, the right S pin is connected to the power input pin of the buck chip, and the lower G pin is connected to the buck chip control pin of the main processor module after being connected through the resistor R63 and the digital transistor Q17; the two ends of the resistor R60 are respectively connected to the 2nd and 3rd pins of the power input of the buck chip U19; one end of the resistor R61 is connected to the 6th pin of the buck chip U19, and the other end is connected to the ground wire of the 4G module through the capacitor C57; the two ends of the resistor R62 are respectively connected to the 12V power supply and the lower G pin of Q17; one end of the resistor R63 is connected to the lower G pin of Q17 like R62, and the other end is connected to the upper pin of the digital transistor Q17. In addition to being connected to R63, the lower pin of the digital transistor Q17 is grounded, and the left pin is connected to the buck chip control pin of the main processor module; one end of the resistor R64 is connected to the 3rd pin of the buck chip pin; both ends of the resistor R65 are connected to the 5th pin of the buck chip U19 and the power output respectively; both ends of the resistor R66 are connected to the 4th pin of the buck chip U19 and the ground wire of the 4G module respectively; one end of the resistor R67 is also connected to the 5th pin of the buck chip, and the other end is connected to the ground wire of the 4G module; both ends of the filter capacitor C51 are connected to the 1st and 8th pins of the buck chip respectively; one end of the filter capacitors C52 and C55 are connected to the 4G module, and the other end is connected to the power input pin of the buck chip; the filter capacitors C53 and C54 are connected to the ground wire of the 4G module to filter the power supply; one end of the capacitor C56 is connected to the 3.8V power supply of the 4G module, and the other end is connected to the ground wire of the 4G module, which also plays a filtering role; one end of the inductor L5 is connected to the 8th pin of the buck chip, and the other end is the output pin of the 3.8V power supply. At the same time, the 3.8V power supply is used as the power output of the 4G module after passing through the magnetic bead MB1.

[0027] Preferably, the LCD screen display module includes resistors R27 to R30, a P-channel field effect transistor Q9, a digital transistor Q10, a capacitor C29, and a connector J5. The two ends of the resistor R27 are respectively connected to the power supply and the D pole of the P-channel field effect transistor Q9; the G pole of the P-channel field effect transistor Q9 is connected to the LCD screen power control pin of the main processor module after passing through the resistor R28 and the digital transistor Q10 in sequence, and the S pole is connected to the ground wire through the capacitor C29; the left pin of the digital transistor Q10 is connected to the LCD screen power control pin of the main processor module, the upper pin is connected to one end of the resistor R28, and the lower pin is connected to the ground wire; the 1st and 2nd pins of the connector J5 are connected to Q9 as power pins, the 3rd and 6th pins are left hanging, the 4th pin is connected to the information receiving pin of the main processor module after passing through the resistor R29, the 5th pin is connected to the information sending pin of the main processor module after passing through the resistor R30, and the 7th and 8th pins are connected to the ground wire.

[0028] Preferably, the basic current comparison module and the 2.5V voltage reference module include resistors R17, R18, R23, capacitors C11-C15, a 2.5V reference voltage module U2, a 1mA reference current module U4, a magnetic bead L6, and a P-channel MOS tube Q6. The G pole of the P-channel MOS tube Q6 is connected to the signal control end of the main processor through the resistor R17, the S pole is connected to the 3.3V power supply, and the D pole is connected to the first pin of the 2.5V reference voltage module U2; the second pin of the 2.5V reference voltage module U2 is connected to the 1mA reference current module U4 through the magnetic bead L6. The second pin of the 2.5V reference voltage module U2 is connected to the analog ground; the third pin of the 2.5V reference voltage module U2 is connected to the analog ground; the first pin of the 1mA reference current module U4 is connected back to the third pin through the resistor R23; the two ends of the resistor R18 are respectively connected to the 3.3V power supply and the G pole of the P-channel MOS tube Q6; the two ends of the capacitor C11 are respectively connected to the first pin of the 2.5V reference voltage module U2 and the analog ground; the two ends of the capacitor C12 are respectively connected to the second pin of the 2.5V reference voltage module U2 and the analog ground; the two ends of the capacitors C13, C14, and C15 are respectively connected to the second pin of the 1mA reference current module U4 and the analog ground. The current size received by the main processor is based on the 1mA current output by the basic current comparison module and the 2.5V voltage reference module f. However, the 1mA current output by module f is affected by the working temperature. The compensation formula of the 1mA reference current related to temperature is shown in formula (2):

[0029]

[0030] Among them, I set is the actual current output by module f, in mA; T is the absolute temperature, which is output by the temperature and humidity monitoring module h to the main processor module m, in K; R set The resistance value of the control module output theoretical current is Figure 7 R 23 , in mΩ; A is the voltage flowing through the temperature control resistor inside the module, which is a fixed value of 224uV / °K under 2.5V voltage input. The temperature is output by the temperature and humidity monitoring module h to the main processor module m.

[0031] Preferably, the 485 signal communication module outputs RS485 form A, B signals or outputs signals to the main processor module, including resistors R36 to R40, capacitors C32, C33, static and surge protection tubes D9, D10, and RS-485 chip U8. Resistor R36 and capacitor C32 are both grounded at one end, and the other end is connected to the 7th pin of RS-485 chip U8; both ends of resistor R38 are respectively connected to the 6th and 7th pins of RS-485 chip U8; both ends of resistor R39 are respectively connected to the 3.3V power supply and the 5th pin of RS-485 chip U8; both ends of static and surge protection tube D9 are respectively connected to resistor R37 and ground; both ends of static and surge protection tube D10 are respectively connected to resistor R40 and ground; the 1st, 2nd, 3rd, and 4th pins of RS-485 chip U8 are connected to the main processor module for data transmission, the 5th pin is grounded, and the 8th pin is connected to the power supply;

[0032] The temperature and humidity monitoring module includes a temperature and humidity monitoring chip U12, and resistors R48 and R49. Under the 3.3V power supply controlled by the main processor, the temperature and humidity monitoring module transmits signals with the main processor module. Resistors R48 and R49 exist as pull-up resistors, so that the SDA and SCL lines remain in a logic high state when there is no main processor module actively pulling down the signal line, ensuring the correct transmission of data and clock signals;

[0033] Under the 3.3V power supply controlled by the main processor, the FLASH storage module transmits and stores signals between the storage chip and the main processor module, including the FLAH storage chip U11. Pins 1, 2, 3, 5, 6, and 7 of the FLAH storage chip U11 are connected to the main processor module. Pin 1 is used as the CS signal line to select and activate a specific storage chip for communication. Pin 2 is used as the MISO signal line to output data. Pin 3 is used as the WP signal line to prevent data from being accidentally or unauthorizedly written to the storage chip. Pin 4 is grounded. Pin 5 is used as the MOS I signal line to receive data. Pin 6 is used as the CLK signal line for synchronous data transmission. Pin 7 is used as the RST signal line for restarting the module and other signals. Pin 8 is connected to the 3.3V power supply.

[0034] The circuit diagram of the 4G communication module includes a 4G module U18, resistors R55-R59, capacitors C48-C50, an electrostatic and wandering protection tube D11, and an IPEX1 generation RF1. The first pin of the 4G module U18 is connected to the main processor module as a TX signal line to output data, the second pin is connected to the main processor module as an RX signal line to input data, the 8th, 13th, 19th, 21st, 27th, 30th, 31st, 33rd, 36th, and 37th pins are grounded, the 15th pin is used as a DATA signal line through a resistor R55 to perform bidirectional data transmission with the main processor module, and the 16th pin is used as a CLK clock line through a resistor R58 to synchronize data transmission with the main processor module. , the 17th pin is connected to the main processor module as the RST signal line through resistor R59 for functions such as unexpected restart, the 18th pin is grounded after passing through capacitor C50, the 29th pin is used as an external restart signal line, and the 32nd pin is connected to the antenna base IPEX1 generation RF1 signal pin (1st pin) through resistors R56 and R57, wherein one end of the static and wandering protection tube D11 is connected to the signal line of the antenna base IPEX1 generation RF1, and one end is grounded; one end of the capacitor C48 is connected to the 32nd pin of the 4G module, and the other end is grounded; one end of the capacitor C49 is connected to the resistor R56, and the other end is grounded; the watchdog monitoring module includes the watchdog monitoring chip U9, resistors R43, R44, and capacitor C34. The watchdog monitoring chip U9 has a built-in timer. When the system is running normally, the program needs to regularly send a signal to reset the timer to the watchdog chip. If the system fails or hangs up, the watchdog chip will trigger a reset signal to complete the monitoring of the main processor module. The first pin of the watchdog monitoring chip U9 is connected to the main processor, and is used to restart the main processor when the main processor sends a dog feeding message in time. The second pin is grounded, the third pin is connected to the 3.3V power supply through the resistor R44 and serves as the signal input channel of the dog feeding channel. The fourth pin is connected to the main processor module as the RST signal line to handle unexpected restart events, and the fifth pin is connected to the 3.3V power supply; the two ends of the resistor R43 are respectively connected to the 3.3V power supply and the first pin of the watchdog monitoring chip U9; the two ends of the capacitor C34 are respectively connected to the 3.3V power supply and the ground;

[0035] The main processor module includes resistors R50, R51, R52, passive crystal oscillator X2, capacitors C9, C10, C41, inductor L4, button battery holder BAT1, test point CN2, and main control chip U10. Since the connection circuits between the main processor module and each module have been described in the previous text, only the minimum system of the main processor module is described here. The second pin of the main control chip is connected to a 3.3V power supply, the 4th and 5th pins are connected to a passive crystal oscillator X2 respectively, the 30th pin is grounded through a resistor R51, and the 60th pin is grounded through a resistor R50; capacitors C9, C10 and the passive crystal oscillator X2 provide a more accurate external clock for the main control chip U10; the two ends of capacitor C41 are connected to a 3.3V power supply and ground respectively; inductor L4 is connected to the positive pole of the battery to filter out high-frequency noise and interference in the power supply; one end of the button battery holder BAT1 is grounded, and the other end is connected to the inductor L4, and the other end of the inductor L4 is connected to a 3.3V power supply to provide a power-free protection for the NTC function of the main processor; one end of the test point CN2 is connected to the 60th pin of U10 through a resistor R52, and the other end is connected to a 3.3V power supply; the main control chip U10 is mainly used as a carrier to complete the functions of controlling the working status of other modules and power control.

[0036] Preferably, the water pressure conversion of the single immersion liquid level transmitter output device of the paddy field water level monitoring system is as follows. Since the signal source of the immersion liquid level transmitter is the water pressure of the detection surface, the theoretical relationship between the water pressure value and the water level is shown in formula (4):

[0037] P=ρgh (4)

[0038] Among them, ρ is the water density, g is the acceleration of gravity, and h is the water level. It can be seen that the change of water level is proportional to the density. The application scenario is paddy fields. The water contains suspended matter of uncertain quantity and different sizes, which leads to different densities in different paddy fields. It can only be clear that the closer to the water surface, the smaller the water density. When the water level is above the electrode plate measurement points i-1 and i, the water pressure P at that time can be obtained. i-1 With P i , substituting it into formula (4), we get formula (5):

[0039] P i -P i-1 =ρ i-1 g(h i -h i-1 ) (5)

[0041] where ρ i-1 is the water density between the electrode plate measuring point i and i-1. Since the water surface is very close to the electrode plate measuring point i, ρ is taken as approximation. i-1 =ρ i , and substitute the water pressure on the water surface and the electrode measuring point i into equation (4), and we get equation (6):

[0042] P1-P i =ρ i-1 g(h1-h i ) (6)

[0043] Where P1 is the water pressure from the water surface to the level transmitter, and h1 is the distance from the water surface to the level transmitter.

[0044] (5) The obtained ρ i-1 Substituting into equation (6), we get equation (7):

[0045]

[0046] In summary, the distance from the water surface to the liquid level transmitter is obtained; due to the characteristics of material precipitation in static water, the closer to the water surface, the smaller the water density is roughly satisfied; therefore, the discrete Kalman filter method is used for the ρ in the previous article i-1 =ρ i The setting is further optimized, and the density near the water level at the nearest measuring point is predicted by the water level density at the previously known measuring point.

[0047] The algorithm adopts the discrete Kalman filter calculation process. In the process of deriving formula (6), ρ is approximated i-1 =ρ i , in fact i-1 =K k * i , formula (6) should be

[0048] P1-P i =K k ρ i-1 g(h1-h i ) (8)

[0049] Where K k is the kth Kalman gain. i-1 Substituting into equation (8), we get equation (9):

[0050]

[0051] The actual density calculated by the previous measurement point of the electrode plate is used, that is, based on the known last state, the current state is inferred through physical mechanism and experience; there is a measurement noise factor in the inference process, so when the actual state appears this time, the error analysis between the actual state and the estimated state is used to allocate the proportion of each gain, so as to estimate the next state; the core of Kalman filtering is to calculate the future gain trend based on the previous state; the following is the calculation process and iteration of discrete Kalman filter;

[0052] The known parameter is k, which is the number of iterations. is the last state (i.e. water density ρ i-1 ), P0 is the previous gain, as shown in formula (10):

[0053] k=1 (10)

[0054] At this time, the time is updated and the next state is estimated, as shown in formula (11):

[0055]

[0056] in, is the prior covariance estimate, that is, the current state quantity calculated and estimated based on the physical mechanism and the previous state, is the last optimal estimate; u0 is the last system control quantity; A is the state transfer matrix, which indicates the current state is inferred from the state at the last moment; B is the control matrix, which indicates how the control quantity u acts on the current state;

[0057] At the same time, the state covariance in this state is estimated based on the state transfer matrix and the covariance when k=0, as shown in formula (12):

[0058]

[0059] is the state covariance estimate in this state; P0 is the optimal covariance estimate of the previous time; Q is the model noise, that is, the noise contained in the prediction model;

[0060] According to formula (10), the Kalman gain of this time can be calculated, as shown in formula (13):

[0061]

[0062] Among them, H is the state transfer matrix, which represents the relationship between the predicted value and the observed value; R is the observation noise, which can be regarded as the measurement noise of the sensor;

[0063] Substituting the Kalman gain calculated by equation (13) into equation (12) yields the optimal estimate, which can also be used for the next iteration:

[0064]

[0065] Among them, z1 is the relative value of the observed value to the predicted value;

[0066] Substitute the prior covariance estimate calculated by equation (9) and the Kalman gain calculated by equation (11) into equation (13) to update the posterior covariance for the next iteration:

[0067] P1=(I-K1H)P1 - (14)

[0068] Among them, I is the unit matrix.

[0069] The testing principle of the present invention is: based on the positions of the two electrode sensing plates, the average density of the liquid at the two positions is inversely calculated, and then the water level height is corrected and calculated by an interpolation method in combination with the water pressure.

[0070] On the one hand, the main processor of the present invention performs temperature, humidity and reference current compensation calculations on the original current signal transmitted by the liquid level transmitter to obtain the final accurate water level. On the other hand, it performs real-time auxiliary verification of the water level through the electrode sensing plate to improve the accuracy of water level detection and avoid the possibility of accuracy fluctuations of the product over time.

[0071] The voltage conversion and voltage stabilization module of the present invention needs to provide a stable 3.3V for conventional circuits and 3.8V for 4G circuits. This is because the voltage requirements of multiple modules in the system are different. At the same time, due to the frequency interference brought by the power supply itself and the noise caused by the cross interference between different signal lines, not only filtering is required in various places in the circuit, but also the voltage stabilization module is required to perform the initial voltage stabilization operation.

[0072] The screen of the LCD screen display module of the present invention is usually in a sleep mode and can be awakened by pressing a button.

[0073] The FLASH storage module of the present invention is used to store various data received by the main processor, such as water level, voltage, temperature and humidity, etc.

[0074] The beneficial effects of the present invention are as follows: The system and method of the present invention are based on a immersion liquid level transmitter and an electrode sensing plate, and can realize accurate and effective monitoring of paddy field water level. The system has high monitoring accuracy and can realize remote data uploading. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0076] Figure 1-1 is a structural block diagram of an embodiment of the present invention;

[0077] Figure 1-2 It is a functional schematic diagram of each module in an embodiment of the present invention;

[0078] Figure 2 A circuit diagram of a signal receiving module of a submersible liquid level transmitter according to an embodiment of the present invention;

[0079] Figure 3is a circuit diagram of an electrode sensing plate according to an embodiment of the present invention;

[0080] Figure 4 A circuit diagram of a lightning protection and protection module according to an embodiment of the present invention;

[0081] Figure 5 is a circuit diagram of a voltage conversion and voltage stabilization module according to an embodiment of the present invention;

[0082] Figure 6 A circuit diagram of an LCD screen display module according to an embodiment of the present invention;

[0083] Figure 7 A circuit diagram of a basic current comparison module and a 2.5V voltage reference module according to an embodiment of the present invention;

[0084] Figure 8 A circuit diagram of a 485 signal communication module according to an embodiment of the present invention;

[0085] Fig. 9 is a circuit diagram of a temperature and humidity monitoring module according to an embodiment of the present invention;

[0086] Fig.10 A circuit diagram of a FLASH storage module according to an embodiment of the present invention;

[0087] Fig.11 A circuit diagram of a 4G communication module according to an embodiment of the present invention;

[0088] Fig.12 A circuit diagram of a watchdog monitoring module according to an embodiment of the present invention;

[0089] Fig.13 is a circuit diagram of a main processor module according to an embodiment of the present invention;

[0090] Fig.14 It is a schematic diagram of a height formula for a water pressure conversion diagram of a single-drop liquid level transmitter output device according to an embodiment of the present invention;

[0091] Fig.15 The algorithm of the embodiment of the present invention adopts a discrete Kalman filter calculation flow chart. DETAILED DESCRIPTION

[0092] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0093] Reference Figure 1-1As shown, the present invention includes a immersion liquid level transmitter signal receiving module a, an electrode sensing plate b, a lightning protection and protection module c, a voltage transformation and voltage stabilization module d, an LCD screen display module e, a basic current comparison module and a 2.5V voltage reference module f, a 485 signal communication module g, a temperature and humidity monitoring module h, a FLASH storage module i, a 4G communication module j, a watchdog monitoring module k and a main processor module m.

[0094] Reference Figure 1-2 As shown, the water level calculation process and the functions of each module in the system are described below: The signal receiving module a of the submersible liquid level transmitter outputs 4-20mA current to the main processor module m. The current I corresponds to the sensor pressure P, that is, the water pressure. The corresponding formula is shown in formula (1):

[0095]

[0097] Where P is the water pressure measured by the submersible level transmitter, in MPa; I is the current received by the main processor module m, in mA; I set is the actual current output by module f, which is theoretically 1mA; A is the minimum current output by the signal receiving module a of the submersible liquid level transmitter, in mA; B is the range of the output current of the signal receiving module a of the submersible liquid level transmitter, in mA; as an embodiment, when the signal receiving module a of the submersible liquid level transmitter outputs 20mA, A=4, B=6, K=0.0981MPa.

[0098] The electrode sensing plate b outputs the water level signal to the main processor module m after being translated by the 485 signal communication module g. The module has low accuracy (10mm) but high reliability, and is mainly used to determine whether the immersion liquid level transmitter has any abnormal conditions. The lightning protection and protection module c and the voltage transformation and voltage stabilization module d jointly provide safe, reliable and stable voltage for the equipment. The LCD screen display module e receives the signal from the main processor module m and provides an interactive interface. The basic current comparison module and the 2.5V voltage reference module f output 2.5V reference voltage and 1mA reference current to the main processor module m. The FLASH storage module i provides space to store historical water level, temperature and humidity, 4G transmission and other information, and the 4G communication module j provides a means for the present invention to perform wireless data transmission. The watchdog monitoring module k receives the periodic dog feeding signal from the main processor module m to prevent the program from accidentally getting stuck.

[0099] Reference Figure 2As shown, the circuit diagram of the signal receiving module a of the immersion liquid level transmitter of the present invention includes diodes D5, D6, D15, shunt resistors R11, R12, ground wire separation resistor R16, filter capacitor C8 and magnetic bead H4. The positive poles of diodes D5, D6, and D15 are respectively connected to the three immersion liquid level transmitter signals, and the negative poles are connected to the same circuit to avoid interference on the one hand, and to cut off the three signals on the other hand to prevent them from being connected to each other; one end of the shunt resistors R11 and R12 is connected to the negative pole of the diode, and one end is grounded to prevent excessive current from passing through the magnetic bead and entering the main processor module; the two ends of the ground wire separation resistor R16 are respectively connected to the ground and the analog ground, separating the ground noise of the digital circuit and the analog circuit and maintaining the connection between them; the two ends of the filter capacitor C8 are respectively connected to the ground and the analog ground, and the two ends of the magnetic bead H4 are respectively connected to the negative pole of the diode and the main processor module, and the magnetic bead H4 and the filter capacitor C8 mainly filter the noise input by the immersion liquid level transmitter.

[0100] Reference Figure 3 As shown, the circuit diagram of the electrode sensing board of the present invention includes a comparator U3B, resistors R92-R97, and capacitors C59 and C60. The first pin of the comparator is used as an input to receive the electrode signal; the second pin of the comparator is connected to the ground through the resistor R97; the third pin of the comparator is output to the main processor module as a comparison signal; the fourth pin of the comparator is grounded; the fifth pin of the comparator is used as an input pin to receive the electrode signal; the sixth pin of the comparator is connected to the ground through the resistor R94; the seventh pin of the comparator is output to the main processor module as a comparison signal; the eighth pin of the comparator is connected to the capacitor C59, and the other end of the capacitor C59 is grounded for filtering; the two ends of the resistor R92 are respectively connected to the 3.3V power supply and the sixth pin of the comparator; the two ends of the resistor R9 are respectively connected to the 3.3V power supply and the seventh pin of the comparator; the two ends of the resistor R95 are respectively connected to the 3.3V power supply and the second pin of the comparator; the two ends of the resistor R96 are respectively connected to the 3.3V power supply and the third pin of the comparator; the electrode sensing board provides the electrode point position phase measurement data, and outputs the data in the form of RS-485.

[0101] Reference Figure 4As shown, the circuit diagram of the lightning protection and protection module of the present invention includes an original power input 12V, a power output 12V, a diode D4, filter capacitors C1, C2, transient voltage suppression diodes D1, D2, D3, an inductor L2, a ceramic chip capacitor L1, varistors MOV1-MOV3, a gas release pipe GT1, and a fuse FS1. The two ends of the diode D4 are respectively connected to the power output 12V and the filter capacitor, and its main purpose is to prevent reverse current; the two ends of the filter capacitors C1 and C2 are respectively connected to the ground wire and the diode D4; the two ends of the transient voltage suppression diode D1 are respectively connected to the ground and the electrical ground; the two ends of the transient voltage suppression diode D2 are respectively connected to the inductor L2 and the diode D4; the two ends of the transient voltage suppression diode D3 are respectively connected to the electrical ground and the inductor L2, and are connected to the power input together with the inductor L2; the two ends of the inductor L2 are respectively connected to the diode D4 and the power input 12V; the first two ends of the ceramic chip capacitor L1 are respectively connected to the ground wire and the electrical ground; the two ends of the transient voltage suppression diode D2 are respectively connected to the inductor L2 and the diode D4; the two ends of the transient voltage suppression diode D3 are respectively connected to the electrical ground and the inductor L2, and are connected to the power input together with the inductor L2; the two ends of the inductor L2 are respectively connected to the diode D4 and the power input 12V; Pin 1 is connected to the power input 12V, pin 2 is connected to the ground, pin 3 is connected to the power integrity ground, and pin 4 is connected to the original power input and connected to the battery after passing through the fuse PS1; one end of the varistor MOV1 and MOV2 is connected to the negative pole of the gas venting pipe GT1, and the other end of the former is connected to the power integrity ground, and the latter is connected to the fourth pin of the ceramic chip capacitor L1; the gas venting pipe GT1, the positive pole is connected to the electrical ground, and the negative pole is connected to the varistor MOV1 and MOV2; the fuse FS1 is responsible for connecting the fourth pin of the ceramic chip capacitor L1 to the original power input.

[0102] Reference Figure 5As shown, the circuit diagram of the voltage transformation and voltage stabilization module of the present invention includes a P-channel field effect transistor Q16, resistors R60-67, a digital transistor Q17, filter capacitors C52-C57, an inductor L5, a magnetic bead MB1, and a step-down chip U19. The left D pin of the P-channel field effect transistor Q16 is connected to the 12V power supply, the right S pin is connected to the power input pin of the buck chip, and the lower G pin is connected to the buck chip control pin of the main processor module after being connected through the resistor R63 and the digital transistor Q17; the two ends of the resistor R60 are respectively connected to the 2nd and 3rd pins of the power input of the buck chip U19; one end of the resistor R61 is connected to the 6th pin of the buck chip U19, and the other end is connected to the ground wire of the 4G module through the capacitor C57; the two ends of the resistor R62 are respectively connected to the 12V power supply and the lower G pin of Q17; one end of the resistor R63 is connected to the lower G pin of Q17 like R62, and the other end is connected to the upper pin of the digital transistor Q17. In addition to being connected to R63, the lower pin of the digital transistor Q17 is grounded, and the left pin is connected to the buck chip control pin of the main processor module; one end of the resistor R64 is connected to the 3rd pin of the buck chip pin; both ends of the resistor R65 are connected to the 5th pin of the buck chip U19 and the power output respectively; both ends of the resistor R66 are connected to the 4th pin of the buck chip U19 and the ground wire of the 4G module respectively; one end of the resistor R67 is also connected to the 5th pin of the buck chip, and the other end is connected to the ground wire of the 4G module; both ends of the filter capacitor C51 are connected to the 1st and 8th pins of the buck chip respectively; one end of the filter capacitors C52 and C55 are connected to the 4G module, and the other end is connected to the power input pin of the buck chip; the filter capacitors C53 and C54 are connected to the ground wire of the 4G module to filter the power supply; one end of the capacitor C56 is connected to the 3.8V power supply of the 4G module, and the other end is connected to the ground wire of the 4G module, which also plays a filtering role; one end of the inductor L5 is connected to the 8th pin of the buck chip, and the other end is the output pin of the 3.8V power supply. At the same time, the 3.8V power supply is used as the power output of the 4G module after passing through the magnetic bead MB1.

[0103] Reference Figure 6As shown, the circuit diagram of the LCD screen display module of the present invention includes resistors R27-R30, P-channel field effect transistor Q9, digital transistor Q10, capacitor C29, and connector J5. The two ends of resistor R27 are respectively connected to the power supply and the D pole of P-channel field effect transistor Q9; the G pole of P-channel field effect transistor Q9 is connected to the LCD screen power control pin of the main processor module after passing through resistor R28 and digital transistor Q10 in sequence, and the S pole is connected to the ground wire through capacitor C29; the left pin of digital transistor Q10 is connected to the LCD screen power control pin of the main processor module, the upper pin is connected to one end of resistor R28, and the lower pin is connected to the ground wire; the first and second pins of connector J5 are connected to Q9 as power pins, the third and sixth pins are suspended, the fourth pin is connected to the information receiving pin of the main processor module after passing through resistor R29, the fifth pin is connected to the information sending pin of the main processor module after passing through resistor R30, and the seventh and eighth pins are connected to the ground wire.

[0104] Reference Figure 7 As shown, the circuit diagram of the basic current comparison module and the 2.5V voltage reference module of the present invention includes resistors R17, R18, R23, capacitors C11-C15, a 2.5V reference voltage module U2, a 1mA reference current module U4, a magnetic bead L6, and a P-channel MOS tube Q6. The G pole of the P-channel MOS tube Q6 is connected to the signal control end of the main processor through the resistor R17, the S pole is connected to the 3.3V power supply, and the D pole is connected to the first pin of the 2.5V reference voltage module U2; the second pin of the 2.5V reference voltage module U2 is connected to the 1mA reference current module U4 through the magnetic bead L6. The second pin of 4 and the third pin of 2.5V reference voltage module U2 are connected to analog ground; the first pin of 1mA reference current module U4 is connected back to the third pin through resistor R23; the two ends of resistor R18 are respectively connected to the 3.3V power supply and the G pole of P-channel MOS tube Q6; the two ends of capacitor C11 are respectively connected to the first pin of 2.5V reference voltage module U2 and analog ground; the two ends of capacitor C12 are respectively connected to the second pin of 2.5V reference voltage module U2 and analog ground; the two ends of capacitors C13, C14, and C15 are respectively connected to the second pin of 1mA reference current module U4 and analog ground. The current size received by the main processor is based on the 1mA current output by the basic current comparison module and the 2.5V voltage reference module f. However, the 1mA current output by module f is affected by the working temperature. The compensation formula of 1mA reference current related to temperature is shown in formula (2):

[0105]

[0106] Among them, I set is the actual current output by module f, in mA; T is the absolute temperature, which is output by the temperature and humidity monitoring module h to the main processor module m, in K; R setThe resistance value of the control module output theoretical current is Figure 7 R 23 , in mΩ; A is the voltage flowing through the temperature control resistor inside the module, which is a fixed value of 224uV / °K under 2.5V voltage input. The temperature is output by the temperature and humidity monitoring module h to the main processor module m.

[0107] Reference Figure 8 As shown, the circuit diagram of the 485 signal communication module of the present invention, the 485 signal communication module outputs RS485 form A, B signals or outputs signals to the main processor module, including resistors R36 ~ R40, capacitors C32, C33, static and surge protection tubes D9, D10, RS-485 chip U8. Resistor R36 and capacitor C32 are both grounded at one end, and the other end is connected to the 7th pin of RS-485 chip U8; both ends of resistor R38 are respectively connected to the 6th and 7th pins of RS-485 chip U8; both ends of resistor R39 are respectively connected to the 3.3V power supply and the 5th pin of RS-485 chip U8; both ends of static and surge protection tube D9 are respectively connected to resistor R37 and ground; both ends of static and surge protection tube D10 are respectively connected to resistor R40 and ground; the 1st, 2nd, 3rd, and 4th pins of RS-485 chip U8 are connected to the main processor module for data transmission, the 5th pin is grounded, and the 8th pin is connected to the power supply. Refer to Fig. 9 As shown, the circuit diagram of the temperature and humidity monitoring module of the present invention includes a temperature and humidity monitoring chip U12, and resistors R48 and R49. Under the 3.3V power supply controlled by the main processor, the temperature and humidity monitoring module transmits signals with the main processor module. Resistors R48 and R49 exist as pull-up resistors, so that the SDA and SCL lines remain in a logic high state when there is no main processor module actively pulling down the signal line, ensuring the correct transmission of data and clock signals.

[0108] Reference Fig.10 As shown, the circuit diagram of the FLASH storage module of the present invention, the FLASH storage module is under the 3.3V power supply controlled by the main processor, the storage chip and the main processor module perform signal transmission and storage, including the FLAH storage chip U11. The 1st, 2nd, 3rd, 5th, 6th, and 7th pins of the FLAH storage chip U11 are connected to the main processor module, the 1st pin is used as the CS signal line to select and activate a specific storage chip for communication, the 2nd pin is used as the MISO signal line to output data, the 3rd pin is used as the WP signal line to prevent data from being accidentally or unauthorizedly written to the storage chip, the 4th pin is grounded, the 5th pin is used as the MOSI signal line to receive data, the 6th pin is used as the CLK signal line for synchronous data transmission, the 7th pin is used as the RST signal line for restarting the module and other signals, and the 8th pin is connected to the 3.3V power supply.

[0109] Reference Fig.11 As shown, the circuit diagram of the 4G communication module of the present invention includes a 4G module U18, resistors R55-R59, capacitors C48-C50, an electrostatic and wandering protection tube D11, and an IPEX1 generation RF1. The first pin of the 4G module U18 is connected to the main processor module as a TX signal line to output data, the second pin is connected to the main processor module as an RX signal line to input data, the 8th, 13th, 19th, 21st, 27th, 30th, 31st, 33rd, 36th, and 37th pins are grounded, the 15th pin is used as a DATA signal line through a resistor R55 to perform bidirectional data transmission with the main processor module, and the 16th pin is used as a CL through a resistor R58. The K clock line is used for synchronous data transmission with the main processor module. The 17th pin is used as the RST signal line with the main processor module through resistor R59 for functions such as unexpected restart. The 18th pin is grounded after passing through capacitor C50. The 29th pin is used as an external restart signal line. The 32nd pin is connected to the antenna base IPEX1 generation RF1 signal pin (pin 1) through resistors R56 and R57. One end of the static and wandering protection tube D11 is connected to the signal line of the antenna base IPEX1 generation RF1, and one end is grounded; one end of the capacitor C48 is connected to the 32nd pin of the 4G module, and the other end is grounded; one end of the capacitor C49 is connected to the resistor R56, and the other end is grounded. Reference Fig.12 As shown, the circuit diagram of the watchdog monitoring module of the present invention includes a watchdog monitoring chip U9, resistors R43, R44, and a capacitor C34. The watchdog monitoring chip U9 has a built-in timer. When the system is running normally, the program needs to regularly send a signal to the watchdog chip to reset the timer. If the system fails or hangs up, the watchdog chip will trigger a reset signal to complete the monitoring of the main processor module. The first pin of the watchdog monitoring chip U9 is connected to the main processor, which is used to restart the main processor when the main processor sends a dog feeding message in time. The second pin is grounded, and the third pin is connected to the 3.3V power supply through the resistor R44 and serves as the signal input channel of the dog feeding channel. The fourth pin is connected to the main processor module as the RST signal line for handling unexpected restart events, and the fifth pin is connected to the 3.3V power supply; the two ends of the resistor R43 are respectively connected to the 3.3V power supply and the first pin of the watchdog monitoring chip U9; the two ends of the capacitor C34 are respectively connected to the 3.3V power supply and the ground.

[0110] Reference Fig.13As shown, the circuit diagram of the main processor module of the present invention includes resistors R50, R51, R52, passive crystal oscillator X2, capacitors C9, C10, C41, inductor L4, button battery holder BAT1, test point CN2, and main control chip U10. Since the connection circuits between the main processor module and each module have been described in the previous text, only the minimum system of the main processor module is described here. The second pin of the main control chip is connected to a 3.3V power supply, the 4th and 5th pins are connected to a passive crystal oscillator X2 respectively, the 30th pin is grounded through a resistor R51, and the 60th pin is grounded through a resistor R50; capacitors C9, C10 and the passive crystal oscillator X2 provide a more accurate external clock for the main control chip U10; the two ends of capacitor C41 are connected to a 3.3V power supply and ground respectively; inductor L4 is connected to the positive pole of the battery to filter out high-frequency noise and interference in the power supply; one end of the button battery holder BAT1 is grounded, and the other end is connected to the inductor L4, and the other end of the inductor L4 is connected to a 3.3V power supply to provide a power-free protection for the NTC function of the main processor; one end of the test point CN2 is connected to the 60th pin of U10 through a resistor R52, and the other end is connected to a 3.3V power supply; the main control chip U10 is mainly used as a carrier to complete the functions of controlling the working status of other modules and power control.

[0111] Reference Fig.15 As shown, the schematic diagram of the height formula of the water pressure conversion diagram of the single immersion liquid level transmitter output of the present invention, since the signal source of the immersion liquid level transmitter is the water pressure of the detection surface, the theoretical relationship between the water pressure value and the water level is shown in formula (4):

[0112] P=ρgh (4)

[0113] Among them, ρ is the water density, g is the acceleration of gravity, and h is the water level. It can be seen that the change of water level is proportional to the density. The application scenario of the present invention is paddy fields. The water contains suspended matter of uncertain quantity and different sizes, which leads to different densities in different paddy fields. It can only be clear that the closer to the water surface, the smaller the water density. When the water level is above the electrode plate measurement points i-1 and i, we can get the water pressure P at that time. i-1 With P i , substituting it into formula (4), we get formula (5):

[0114] P i -P i-1 =ρ i-1 g(h i -h i-1 ) (5)

[0116] where ρ i-1 is the water density between the electrode plate measuring point i and i-1. Since the water surface is very close to the electrode plate measuring point i, we approximate ρ i-1 =ρ i, and substitute the water pressure on the water surface and the electrode measuring point i into equation (4), and we get equation (6):

[0117] P1-P i =ρ i-1 g(h1-h i ) (6)

[0118] Where P1 is the water pressure from the water surface to the level transmitter, and h1 is the distance from the water surface to the level transmitter. i-1 Substituting into equation (6), we get equation (7):

[0119]

[0120] In summary, we have obtained the distance from the water surface to the liquid level transmitter. Due to the characteristics of material precipitation in static water, the closer to the water surface, the smaller the water density is, which is roughly satisfied. Therefore, the present invention adopts the discrete Kalman filter method to target ρ in the above text. i-1 =ρ i The setting is further optimized, and the density near the water level at the nearest measuring point is predicted by the water level density at the previously known measuring point;

[0121] Reference Fig.15 As shown in the flowchart of the algorithm of the present invention, the discrete Kalman filter is used. In the process of deriving formula (6), we approximately take ρ i-1 =ρ i , in fact i-1 =K k * i , formula (6) should be

[0122] P1-P i =K k ρ i-1 g(h1-h i ) (8)

[0123] Where K k is the kth Kalman gain. i-1 Substituting into equation (8), we get equation (9):

[0124]

[0125] In simple terms, the actual density calculated by the previous measurement point of the electrode plate is the actual density of the point measured before the electrode plate. i-1 ) is used to infer the current state (the actual density ρ of the current measuring point of the electrode plate) through physical mechanism and experience. i). There are factors such as measurement noise in the inference process. Therefore, when the actual state appears, the error analysis between the actual state and the estimated state is used to allocate the weight of each gain, so as to estimate the next state. The core of Kalman filtering is to calculate the future gain trend based on the previous state. The following is a description of the calculation process and iteration of the discrete Kalman filter.

[0126] The known parameter is k, which is the number of iterations. is the last state (i.e. water density ρ i-1 ), P0 is the previous gain, as shown in formula (10):

[0127] k=1 (10)

[0128] At this time, the time is updated and the next state is estimated, as shown in formula (11):

[0129]

[0130] in, is the prior covariance estimate, that is, the current state quantity calculated and estimated based on the physical mechanism and the previous state, is the last optimal estimate; u0 is the last system control quantity; A is the state transfer matrix, which means the state at the current moment is inferred from the state at the previous moment; B is the control matrix, which means how the control quantity u acts on the current state.

[0131] At the same time, the state covariance in this state is estimated based on the state transfer matrix and the covariance when k=0, as shown in formula (12):

[0132]

[0133] is the state covariance estimate in this state; P0 is the optimal covariance estimate of the previous time; Q is the model noise, that is, the noise contained in our prediction model.

[0134] According to formula (10), the Kalman gain of this time can be calculated, as shown in formula (13):

[0135]

[0136] Among them, H is the state transfer matrix, which represents the relationship between the predicted value and the observed value; R is the observation noise, which can be regarded as the measurement noise of the sensor.

[0137] Substituting the Kalman gain calculated by equation (13) into equation (12) yields the optimal estimate, which is also the value we can use for the next iteration:

[0138]

[0139] Among them, z1 is the relative value of the observed value to the predicted value (which can be regarded as the sensor return value).

[0140] Substitute the prior covariance estimate calculated by equation (9) and the Kalman gain calculated by equation (11) into equation (13) to update the posterior covariance for the next iteration:

[0141]

[0142] Among them, I is the unit matrix.

[0143] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0144] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A paddy field water level monitoring system based on a submersible liquid level transmitter and an electrode sensing plate, characterized in that: It includes a main processor module and a submersible liquid level transmitter connected to the main processor module, an electrode sensing board, a lightning protection and protection module, a voltage transformation and voltage stabilization module, an LCD screen display module, a basic current comparison module and a 2.5V voltage reference module, a 485 signal communication module, a temperature and humidity monitoring module, a FLASH storage module, a 4G communication module and a watchdog monitoring module; The immersion type liquid level transmitter is used to provide a water level output in the form of current, and the water level is positively correlated with the current; The electrode sensing plate outputs high / low levels through electrodes of different heights; The lightning protection and protection module prevents damage to components due to excessive power input signals, and prevents damage to equipment due to lightning strikes during outdoor operations. The LCD screen display module is used to display the current water level, temperature and humidity of the system and the measured water level value; The basic current comparison module and the 2.5V voltage reference module provide a comparison reference for the current output by the submersible liquid level transmitter to ensure the measurement accuracy of the system, and provide a precise voltage for the main processor module. The 485 signal communication module provides the same protocol for information communication between the main processor module and the electrode sensing board; The temperature and humidity monitoring module, on the one hand, serves as the output of paddy field environmental parameters, and on the other hand, reduces the influence of temperature and humidity through filtering algorithms to provide more accurate water level values; The FLASH storage module is used to store various types of data received by the main processor; The 4G communication module is used to provide a 4G remote data upload function; The watchdog monitoring module provides a convenient restart method for system programs that are accidentally stuck; The main processor module is used to process information transmission between modules.

2. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The current range is 4-20mA. The module receives the current signal output by the sensor that is positively correlated with the water level, and uses a differential comparison circuit to eliminate the current error generated in the process of transmitting the current from the immersion liquid level transmitter to the main processor; the main processor module adds a 32.768KHz crystal oscillator to provide a more accurate original clock frequency for the main processor, so that the sampled signal can be effectively analyzed and processed inside the main processor, ensuring the reliability of the paddy field plow bottom water level monitoring system and enhancing interactivity; the electrode sensing board uses a polling method to periodically query the high and low level changes of each electrode, and regards the highest high level electrode position as the water level position and outputs it to the main processor module; the voltage transformation and voltage stabilization module provides a stable 3.3V voltage for conventional circuits and a 3.8V voltage for 4G circuits.

3. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The water level calculation process of the paddy field water level monitoring system is as follows: the input liquid level transmitter signal receiving module outputs 4-20mA current to the main processor module. The current size I corresponds to the sensor pressure P, that is, the water pressure size. The corresponding formula is shown in formula (1): Where P is the water pressure measured by the submersible level transmitter, in MPa; I is the current received by the main processor module m, in mA; I set is the actual current output by module f, which is 1mA in theory; A is the minimum current output by the signal receiving module a of the submersible liquid level transmitter, in mA; B is the range of the output current of the signal receiving module a of the submersible liquid level transmitter, in mA; The electrode sensing board outputs the water level signal to the main processor module after being translated by the 485 signal communication module. The module has low accuracy but high reliability and is mainly used to determine whether the submersible liquid level transmitter has any abnormal conditions. The lightning protection and protection module and the voltage transformation and voltage stabilization module jointly provide safe, reliable and stable voltage for the equipment. The LCD screen display module receives the signal from the main processor module and provides an interactive interface. The basic current comparison module and the 2.5V voltage reference module output 2.5V reference voltage and 1mA reference current to the main processor module. The FLASH storage module provides space to store historical water level, temperature and humidity, and 4G transmission information. The 4G communication module provides a means for the present invention to perform wireless data transmission. The watchdog monitoring module receives the periodic dog feeding signal of the main processor module to prevent the program from accidentally getting stuck.

4. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The signal receiving module of the submersible liquid level transmitter includes diodes D5, D6, D15, shunt resistors R11, R12, ground separation resistor R16, filter capacitor C8 and magnetic bead H4; the positive poles of diodes D5, D6, and D15 are respectively connected to the three submersible liquid level transmitter signals, and the negative poles are connected to the same circuit to avoid interference on the one hand, and to cut off the three signals on the other hand to prevent them from conducting with each other; one end of the shunt resistors R11 and R12 is connected to the negative pole of the diode, and one end is grounded to prevent excessive current from passing through the magnetic bead and entering the main processor module; the two ends of the ground separation resistor R16 are respectively connected to the ground and the analog ground, separating the ground noise of the digital circuit and the analog circuit and maintaining the connection between them; the two ends of the filter capacitor C8 are respectively connected to the ground and the analog ground, and the two ends of the magnetic bead H4 are respectively connected to the negative pole of the diode and the main processor module, and the function of the magnetic bead H4 and the filter capacitor C8 is mainly to filter the noise input by the submersible liquid level transmitter; The electrode sensing board includes a comparator U3B, resistors R92 to R97, and capacitors C59 and C60; Pin 1 of the comparator receives the electrode signal as input; Pin 2 of the comparator is connected to ground through resistor R97; Pin 3 of the comparator is output as a comparison signal to the main processor module; Pin 4 of the comparator is grounded; Pin 5 of the comparator is used as an input pin to receive electrode signals; Pin 6 of the comparator is connected to ground through resistor R94; Pin 7 of the comparator is output as a comparison signal to the main processor module; Pin 8 of the comparator is connected to capacitor C59, and the other end of capacitor C59 is grounded for filtering; both ends of resistor R92 are connected to a 3.3V power supply and Pin 6 of the comparator respectively; both ends of resistor R9 are connected to a 3.3V power supply and Pin 7 of the comparator respectively; both ends of resistor R95 are connected to a 3.3V power supply and Pin 2 of the comparator respectively; both ends of resistor R96 are connected to a 3.3V power supply and Pin 3 of the comparator respectively; the electrode sensing board provides periodic measurement data of the electrode point position and outputs the data in the form of RS-485.

5. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The lightning protection and protection module includes an original power input 12V, a power output 12V, a diode D4, filter capacitors C1, C2, transient voltage suppression diodes D1, D2, D3, an inductor L2, a ceramic chip capacitor L1, varistors MOV1-MOV3, a gas release pipe GT1, and a fuse FS1; the two ends of the diode D4 are respectively connected to the power output 12V and the filter capacitor, and its main purpose is to prevent reverse current; the two ends of the filter capacitors C1 and C2 are respectively connected to the ground wire and the diode D4; the two ends of the transient voltage suppression diode D1 are respectively connected to the ground and the electrical ground; the two ends of the transient voltage suppression diode D2 are respectively connected to the inductor L2 and the diode D4; the two ends of the transient voltage suppression diode D3 are respectively connected to the electrical ground and inductor L2, and connected to the power input together with the inductor L2; the two ends of the inductor L2 are respectively connected to the diode D4 and the power input 12V; the first pin of the ceramic chip capacitor L1 is connected to the power input 12V, the second pin is grounded, the third pin is connected to the power integrity ground, and the fourth pin is connected to the original power input and connected to the battery after passing through the fuse PS1; one end of the varistor MOV1 and MOV2 is connected to the negative pole of the gas venting pipe GT1, and the other end of the former is connected to the power integrity ground, and the latter is connected to the fourth pin of the ceramic chip capacitor L1; the gas venting pipe GT1, the positive pole is connected to the electrical ground, and the negative pole is connected to the varistor MOV1 and MOV2; the fuse FS1 is responsible for connecting the fourth pin of the ceramic chip capacitor L1 with the original power input.

6. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The voltage conversion and voltage stabilization module includes a P-channel field effect transistor Q16, resistors R60-67, a digital transistor Q17, filter capacitors C52-C57, an inductor L5, a magnetic bead MB1, and a buck chip U19; the left D pin of the P-channel field effect transistor Q16 is connected to a 12V power supply, the right S pin is connected to a power input pin of the buck chip, and the lower G pin is connected to a buck chip control pin of the main processor module after being connected through a resistor R63 and a digital transistor Q17; the two ends of the resistor R60 are respectively connected to the second and third pins of the power input of the buck chip U19; one end of the resistor R61 is connected to the sixth pin of the buck chip U19, and the other end is connected to the ground wire of the 4G module through a capacitor C57; the two ends of the resistor R62 are respectively connected to a 12V power supply and to the lower G pin of Q17; one end of the resistor R63 is connected to the lower G pin of Q17 like R62, and the other end is connected to the upper pin of the digital transistor Q17. In addition to being connected to R63, the lower pin of the digital transistor Q17 is grounded, and the left lead The first foot is connected to the buck chip control pin of the main processor module; one end of the resistor R64 is connected to the 3rd pin of the buck chip; the two ends of the resistor R65 are respectively connected to the 5th pin of the buck chip U19 and the power output; the two ends of the resistor R66 are respectively connected to the 4th pin of the buck chip U19 and the ground wire of the 4G module; one end of the resistor R67 is also connected to the 5th pin of the buck chip, and the other end is connected to the ground wire of the 4G module; the two ends of the filter capacitor C51 are respectively connected to the 1st and 8th pins of the buck chip; the filter capacitors C52 and C55 are both connected to the 4G module at one end, and the other end is connected to the power input pin of the buck chip; the filter capacitors C53 and C54 are connected to the ground wire of the 4G module to filter the power supply; one end of the capacitor C56 is connected to the 3.8V power supply of the 4G module, and the other end is connected to the ground wire of the 4G module, which also plays a filtering role; one end of the inductor L5 is connected to the 8th pin of the buck chip, and the other end is the output pin of the 3.8V power supply. At the same time, the 3.8V power supply is used as the power output of the 4G module after passing through the magnetic bead MB1.

7. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The LCD screen display module includes resistors R27-R30, a P-channel field effect transistor Q9, a digital transistor Q10, a capacitor C29, and a connector J5. The two ends of the resistor R27 are respectively connected to the power supply and the D pole of the P-channel field effect transistor Q9; the G pole of the P-channel field effect transistor Q9 is connected to the LCD screen power control pin of the main processor module after passing through the resistor R28 and the digital transistor Q10 in sequence, and the S pole is connected to the ground wire through the capacitor C29; the left pin of the digital transistor Q10 is connected to the LCD screen power control pin of the main processor module, the upper pin is connected to one end of the resistor R28, and the lower pin is connected to the ground wire; the 1st and 2nd pins of the connector J5 are connected to Q9 as power pins, the 3rd and 6th pins are left hanging, the 4th pin is connected to the information receiving pin of the main processor module after passing through the resistor R29, the 5th pin is connected to the information sending pin of the main processor module after passing through the resistor R30, and the 7th and 8th pins are connected to the ground wire.

8. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The basic current comparison module and the 2.5V voltage reference module include resistors R17, R18, R23, capacitors C11-C15, a 2.5V reference voltage module U2, a 1mA reference current module U4, a magnetic bead L6, and a P-channel MOS tube Q6. The G pole of the P-channel MOS tube Q6 is connected to the signal control end of the main processor through the resistor R17, the S pole is connected to the 3.3V power supply, and the D pole is connected to the first pin of the 2.5V reference voltage module U2; the second pin of the 2.5V reference voltage module U2 is connected to the second pin of the 1mA reference current module U4 through the magnetic bead L6, and the third pin of the 2.5V reference voltage module U2 is connected to the analog ground; the first pin of the 1mA reference current module U4 is connected to the analog ground through the resistor R 23 is connected back to the third pin; both ends of the resistor R18 are connected to the 3.3V power supply and the G pole of the P-channel MOS tube Q6 respectively; both ends of the capacitor C11 are connected to the first pin of the 2.5V reference voltage module U2 and the analog ground respectively; both ends of the capacitor C12 are connected to the second pin of the 2.5V reference voltage module U2 and the analog ground respectively; both ends of the capacitors C13, C14, and C15 are connected to the second pin of the 1mA reference current module U4 and the analog ground respectively; the current size received by the main processor is based on the 1mA current output by the basic current comparison module and the 2.5V voltage reference module f; however, the 1mA current output by the module f is affected by the working temperature, and the compensation formula of the 1mA reference current related to temperature is shown in formula (2): Among them, I set is the actual current output by module f, in mA; T is the absolute temperature, which is output by the temperature and humidity monitoring module h to the main processor module m, in K; R set The resistance value of the control module output theoretical current is R in Figure 7. 23 , in mΩ; A is the voltage flowing through the temperature control resistor inside the module, which is a fixed value of 224uV / K under 2.5V voltage input; and the temperature is output by the temperature and humidity monitoring module h to the main processor module m.

9. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The 485 signal communication module outputs RS485 form A and B signals or outputs signals to the main processor module, including resistors R36-R40, capacitors C32 and C33, static and surge protection tubes D9 and D10, and RS-485 chip U8; one end of the resistor R36 and the capacitor C32 are grounded, and the other end is connected to the 7th pin of the RS-485 chip U8; the two ends of the resistor R38 are respectively connected to the 6th and 7th pins of the RS-485 chip U8; the two ends of the resistor R39 are respectively connected to the 3.3V power supply and the 5th pin of the RS-485 chip U8; the two ends of the static and surge protection tube D9 are respectively connected to the resistor R37 and the ground; the two ends of the static and surge protection tube D10 are respectively connected to the resistor R40 and the ground; the 1st, 2nd, 3rd, and 4th pins of the RS-485 chip U8 are connected to the main processor module for data transmission, the 5th pin is grounded, and the 8th pin is connected to the power supply; The temperature and humidity monitoring module includes a temperature and humidity monitoring chip U12, resistors R48 and R49; under the 3.3V power supply controlled by the main processor, the temperature and humidity monitoring module transmits signals with the main processor module, and resistors R48 and R49 exist as pull-up resistors, so that when there is no main processor module actively pulling down the signal line, the SDA and SCL lines remain in a logic high state, ensuring the correct transmission of data and clock signals; Under the 3.3V power supply controlled by the main processor, the FLASH storage module transmits and stores signals between the storage chip and the main processor module, including the FLAH storage chip U11; the 1st, 2nd, 3rd, 5th, 6th and 7th pins of the FLAH storage chip U11 are connected to the main processor module, the 1st pin is used as the CS signal line to select and activate a specific storage chip for communication, the 2nd pin is used as the MISO signal line to output data, the 3rd pin is used as the WP signal line to prevent data from being accidentally or unauthorizedly written to the storage chip, the 4th pin is grounded, the 5th pin is used as the MOSI signal line to receive data, the 6th pin is used as the CLK signal line for synchronous data transmission, the 7th pin is used as the RST signal line for restarting the module and other signals, and the 8th pin is connected to the 3.3V power supply; The circuit diagram of the 4G communication module includes a 4G module U18, resistors R55-R59, capacitors C48-C50, an electrostatic and wandering protection tube D11, and an IPEX1 generation RF1; the first pin of the 4G module U18 is connected to the main processor module as a TX signal line to output data, the second pin is connected to the main processor module as an RX signal line to input data, the 8th, 13th, 19th, 21st, 27th, 30th, 31st, 33rd, 36th, and 37th pins are grounded, the 15th pin is used as a DATA signal line through a resistor R55 to perform bidirectional data transmission with the main processor module, and the 16th pin is used as a CLK signal line through a resistor R58. The clock line and the main processor module are used for synchronous data transmission. The 17th pin is used as the RST signal line through the resistor R59 and is used with the main processor module for functions such as unexpected restart. The 18th pin is grounded after passing through the capacitor C50. The 29th pin is used as an external restart signal line. The 32nd pin is connected to the antenna base IPEX1 generation RF1 signal pin (pin 1) through the resistors R56 and R57. One end of the static and wandering protection tube D11 is connected to the signal line of the antenna base IPEX1 generation RF1, and one end is grounded; one end of the capacitor C48 is connected to the 32nd pin of the 4G module, and the other end is grounded; one end of the capacitor C49 is connected to the resistor R56, and the other end is grounded; The watchdog monitoring module includes a watchdog monitoring chip U9, resistors R43 and R44, and a capacitor C34; the watchdog monitoring chip U9 has a built-in timer. When the system is operating normally, the program needs to periodically send a signal to reset the timer to the watchdog chip. If the system fails or hangs up, the watchdog chip will trigger a reset signal to complete the monitoring of the main processor module; the first pin of the watchdog monitoring chip U9 is connected to the main processor, which is used to restart the main processor when the main processor sends a dog feeding message in time, the second pin is grounded, the third pin is connected to the 3.3V power supply through the resistor R44 and serves as the signal input channel of the dog feeding channel, the fourth pin is connected to the main processor module as the RST signal line to handle unexpected restart events, and the fifth pin is connected to the 3.3V power supply; the two ends of the resistor R43 are respectively connected to the 3.3V power supply and the first pin of the watchdog monitoring chip U9; the two ends of the capacitor C34 are respectively connected to the 3.3V power supply and the ground; The main processor module includes resistors R50, R51, R52, passive crystal oscillator X2, capacitors C9, C10, C41, inductor L4, button battery holder BAT1, test point CN2, and main control chip U10; since the connection circuit between the main processor module and each module has been described in the previous text, only the minimum system of the main processor module is described here; the second pin of the main control chip is connected to the 3.3V power supply, the 4th and 5th pins are respectively connected to the passive crystal oscillator X2, the 30th pin is grounded through the resistor R51, and the 60th pin is grounded through the resistor R50; capacitors C9, C10 and the passive crystal oscillator X2 Provide a more accurate external clock for the main control chip U10; the two ends of capacitor C41 are connected to the 3.3V power supply and ground respectively; the inductor L4 is connected to the positive pole of the battery to filter out high-frequency noise and interference in the power supply; one end of the button battery holder BAT1 is grounded, and the other end is connected to the inductor L4, and the other end of the inductor L4 is connected to the 3.3V power supply to provide power-free protection for the NTC function of the main processor; one end of the test point CN2 is connected to the 60th pin of U10 through the resistor R52, and the other end is connected to the 3.3V power supply; the main control chip U10 is mainly used as a carrier to complete the functions of controlling the working status of other modules and power control.

10. The paddy field water level monitoring system based on the immersion liquid level transmitter and the electrode sensing plate according to claim 1 is characterized in that: The water pressure conversion of the single immersion liquid level transmitter output device of the paddy field water level monitoring system is as follows. Since the signal source of the immersion liquid level transmitter is the water pressure of the detection surface, the theoretical relationship between the water pressure value and the water level is shown in formula (4): P=ρgh (4) Among them, ρ is the water density, g is the acceleration of gravity, and h is the water level. It can be seen that the change of water level is proportional to the density. The application scenario is paddy fields. The water contains suspended matter of uncertain quantity and different sizes, which leads to different densities in different paddy fields. It can only be clear that the closer to the water surface, the smaller the water density. When the water level is above the electrode plate measurement points i-1 and i, the water pressure P at that time can be obtained. i-1 With P i , substituting it into formula (4), we get formula (5): P i -P i-1 =ρ i-1 g(h i -h i-1 ) (5) where ρ i-1 is the water density between the electrode plate measuring point i and i-1. Since the water surface is very close to the electrode plate measuring point i, ρ is taken as approximation. i-1 =ρ i , and substitute the water pressure on the water surface and the electrode measuring point i into equation (4), and we get equation (6): P1-P i =ρ i-1 g(h1-h i ) (6) Where P1 is the water pressure from the water surface to the liquid level transmitter, h1 is the distance from the water surface to the liquid level transmitter; ρ obtained by formula (5) i-1 Substituting into equation (6), we get equation (7): The distance from the water surface to the liquid level transmitter is obtained; due to the characteristics of material precipitation in static water, the closer to the water surface, the smaller the water density is roughly satisfied; therefore, the discrete Kalman filter method is used to target ρ in the previous article i-1 =ρ i The setting is further optimized, and the density near the water level at the nearest measuring point is predicted by the water level density at the previously known measuring point; The algorithm adopts the discrete Kalman filter calculation process. In the process of deriving formula (6), ρ is approximated i-1 =ρ i , in fact i-1 =K k *ρ i , formula (6) should be P1-P i =K k r i-1 g(h1-h i ) (8) Where K k is the kth Kalman gain; the ρ obtained by formula (4) i-1 Substituting into equation (8), we get equation (9): The actual density calculated by the previous measurement point of the electrode plate is used, that is, based on the known last state, the current state is inferred through physical mechanism and experience; there is a measurement noise factor in the inference process, so when the actual state appears this time, the error analysis between the actual state and the estimated state is used to allocate the proportion of each gain, so as to estimate the next state; the core of Kalman filtering is to calculate the future gain trend based on the previous state; the following is the calculation process and iteration of discrete Kalman filter; The known parameter is k, which is the number of iterations. is the last state, that is, the water density ρ i-1 , P0 is the previous gain, as shown in formula (10): k＝1 (10) At this time, the time is updated and the next state is estimated, as shown in formula (11): in, is the prior covariance estimate, that is, the current state quantity calculated and estimated based on the physical mechanism and the previous state, is the last optimal estimate; u0 is the last system control quantity; A is the state transfer matrix, which indicates the current state is inferred from the state at the last moment; B is the control matrix, which indicates how the control quantity u acts on the current state; At the same time, the state covariance in this state is estimated based on the state transfer matrix and the covariance when k=0, as shown in formula (12): is the state covariance estimate in this state; P0 is the optimal covariance estimate of the previous time; Q is the model noise, that is, the noise contained in the prediction model; According to formula (10), the Kalman gain of this time can be calculated, as shown in formula (13): Among them, H is the state transfer matrix, which represents the relationship between the predicted value and the observed value; R is the observation noise, which can be regarded as the measurement noise of the sensor; Substituting the Kalman gain calculated by equation (13) into equation (12) yields the optimal estimate, which can also be used for the next iteration: Among them, z1 is the relative value of the observed value to the predicted value, which can be regarded as the sensor return value; Substitute the prior covariance estimate calculated by equation (9) and the Kalman gain calculated by equation (11) into equation (13) to update the posterior covariance for the next iteration: Among them, I is the unit matrix.

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