CN102928040A - Ship-lock multi-channel water level measuring system and filter method thereof - Google Patents

Abstract

The invention discloses a ship lock multi-channel water level measuring system and a filtering method. The system is composed of multi-water level sensors, a data acquisition module, a remote monitoring PC, a GSM module, a communication network and the like. Using the single-chip microcomputer as the lower-level microcontroller, using high-precision A/D converters, real-time monitoring of water levels at multiple measurement points such as the upstream and downstream of the ship lock, and lock chambers, and repacking and reconstructing the multi-channel data, and using the 485 bus to remotely transmit them to the upper monitoring PC. Display the water level of each point in real time, and send the water level information to designated mobile phone users through the GSM short message module and its wireless network, and also support mobile phone users to use the GSM network to actively ask for the water level of each point at any time. The system adopts FIR filtering based on the median filtering of single-chip microcomputer, which has the advantages of easy implementation and absolute stability of the system. The invention has the advantages of low cost, high precision, strong anti-interference ability and friendly human-computer interaction.

Description

Multi-channel water level measurement system and filtering method for ship lock

technical field

The invention relates to a measurement system, in particular to a ship lock multi-channel water level measurement system and a filtering method.

Background technique

The real-time monitoring of the water level of the lock station is an inevitable requirement for the operation management of the lock and the safe navigation of ships. Ship lock dispatchers must always pay attention to changes in the water level upstream, downstream, and in the lock chamber. Accurate and reliable water level data make it possible for ships to automatically pass through the lock, thereby greatly reducing the difficulty of ships passing through the lock and the work intensity of ship lock dispatchers. At the same time, the ship lock It is also very necessary for the friends of the boat people to keep abreast of the changing upstream and downstream water level information in a timely manner, so that they can take the initiative to make a choice whether to set sail or stop and dock. However, at present, the water level measurement facilities in many ship lock stations are outdated, the technology is relatively backward, the degree of automation is not enough, and the accuracy of water level information is not high. Efficiency. In addition, ship lock stations mostly rely on manual release of water level information through the broadcast system or even blackboard newspapers. The form is relatively simple, the degree of humanization is not high, and the audience is limited. The timing also caused a lot of inconvenience to the operation and scheduling of the lock. Therefore, a multi-channel water level real-time monitoring, remote transmission and short message interaction system for ship lock engineering applications is designed to improve and enhance the water level automatic monitoring level of ship locks, realize the safe operation of ship lock station dispatching and improve the humanized service quality of passing ships has important practical significance.

Chinese patent specification 200710068013.2 discloses a wireless water level monitoring system to solve the problem in the existing water level monitoring system that the monitored data cannot be transmitted in real time but can only be obtained on the spot. But its shortcomings are: 1) In addition to useful signals, electromagnetic waves propagating in space also have a lot of interference, such as intermodulation, adjacent frequency, same frequency interference from other communication systems, and electromagnetic interference from the scene , and interference from natural phenomena such as sky electricity. These interferences often cause the monitoring system to fail to communicate normally; 2) The hardware cost of the monitoring system is high, and the collection of water level data at each measurement point cannot fully guarantee real-time performance; 3) Water level monitoring and information release are not organically integrated, so it is impossible to The water level information informs the user in time, which limits the scope of application of the system.

In the paper "Principle and Practice of Laser Monitoring System for Ship Lock Water Level and Water Level Difference" [Shandong Communications Technology, 2010 (1)], Chen Yonggang and others introduced a modern laser ranging technology to upgrade the water level measurement system of the original ship lock. However, this method has the following problems: 1) The laser ranging sensor is expensive, the use conditions are relatively harsh, and the installation of the reflective floating plate is difficult; 2) The change of the ambient temperature, the long-term parasitic insects and spider webs in the logging Such debris will block the laser beam and must be eliminated regularly; 3) The scalability of the system is poor, which is not conducive to real-time itinerant measurement of multi-channel water levels.

The water level pressure sensor in the prior art outputs a non-periodically continuously changing current signal in real time. In actual use in a complex water environment, there are various forms of interference sources, such as the large current impact generated by the start-up and operation of various power equipment in the hoist room of the ship lock station, the fluctuation of the 220V grid voltage and the interference of waveform distortion , electromagnetic radiation, current signal attenuation caused by long-distance transmission, overvoltage caused by lightning, etc. Once the above interference invades the input channel of the measurement system, it will undoubtedly increase the data acquisition error or submerge the useful signal components of the sensor, and even destroy the operation of the entire measurement system in severe cases.

In order to improve the water level automatic monitoring level of the ship lock, realize the safe operation of the ship lock station dispatching, improve the efficiency of passing ships through the lock and provide humanized services, a multi-channel water level measurement system for the ship lock is designed to solve the problem of the existing water level sensor data collection is difficult. Interference, low degree of automation of collection, single form of information release, and weak human-computer interaction have important practical significance.

Contents of the invention

The purpose of the present invention is to provide a ship lock multi-channel water level measurement system and a filtering method to solve the technical problems of the prior art that data collection is susceptible to interference, the degree of collection automation is not high, the form of information release is single, and the human-computer interaction is not strong.

The purpose of the present invention is achieved through the following technical solutions:

A multi-channel water level measurement system for a ship lock, including an upstream water level sensor, a downstream water level sensor, a lock chamber water level sensor, a data acquisition module, an RS485 network, a 485/232 converter, a remote monitoring PC, a GSM module, and a mobile phone user. The acquisition module includes a signal conditioning circuit A, a signal conditioning circuit B, a signal conditioning circuit C, a multi-way switch, an A/D conversion circuit, a single-chip microcomputer, a power management module, buttons, a digital tube, a TTL/485 conversion circuit, and the upstream water level sensor , the downstream water level sensor, and the sluice chamber water level sensor are respectively connected to the signal conditioning circuit A, the signal conditioning circuit B, and the signal conditioning circuit C, and the signal conditioning circuit A, the signal conditioning circuit B, and the signal conditioning circuit C are connected to the multi-way switch input terminal , the multi-way switch output end is connected with the A/D conversion circuit, and the A/D conversion circuit, power management module, button, and digital tube are respectively connected with the single-chip microcomputer, and one end of the TTL/485 conversion circuit is connected with the single-chip microcomputer, and the other end is connected with the single-chip microcomputer. One end of the 485/232 converter is connected to the RS485 network, and the other end is connected to the remote monitoring PC. The GSM module is connected to the remote monitoring PC and communicates with the mobile phone user through the wireless communication network.

A filtering method for a ship lock multi-channel water level measurement system, the method comprising the following steps:

1) Median filtering is performed on the measured parameters, that is, the measured parameters are continuously sampled multiple times, the sampling values are sorted, and the median value is selected as the effective sampling value for this time;

2) Perform finite impulse response filtering on the measured parameters, and first give the frequency characteristic Hd(e ^jw ) of the ideal filter;

3) Compute the unit sample response of the ideal filter,

4) Set filter form, window function type, window length N;

5) Call the MATLAB function to calculate the filter coefficient w(n);

6) Calculate the unit sampling response h(n)=h _d (n)w(n) of the designed filter;

7) Store the designed N h(n) sequences into the corresponding storage area;

8) Store the median filtering result x1 as x(n) into the corresponding storage area;

9) Circularly read h(n) and x(n) values for convolution operation to obtain online filtering results

The object of the present invention can also be further realized by the following technical measures:

The aforementioned multi-channel water level measurement system for ship locks, wherein the signal conditioning circuit A, the signal conditioning circuit B, and the signal conditioning circuit C respectively include an I/V conversion circuit, a follower, and a low-pass filter, and the low-pass filter is Butterwater In the second-order form, the input end of the I/V conversion circuit is connected to the water level sensor, the output end of the I/V conversion circuit is connected to the input end of the follower, and the output end of the follower is connected to the low-pass filter.

The aforementioned multi-channel water level measurement system for ship locks, wherein the A/D conversion circuit includes an A/D converter 101, a complex programmable logic device CPLD 102, and a reference voltage chip 103, and the model of the A/D converter 101 is MAX195, so The CPLD 102 model is EPM7128S, the reference voltage chip 103 model is MAX6250, the AIN end of the A/D converter 101 is the input channel of the analog signal to be converted, and the CLK end of the A/D converter 101 is connected to the CPLD The 4FPCLK end of 102 is connected, the EOC end of the A/D converter 101 is connected with the EOC end of the CPLD 102, the CONV end of the A/D converter 101 is connected with the CONV end of the CPLD 102, and the A/D conversion The DOUT end of the device 101 is connected with the SDIN end of the CPLD 102, the RESET end of the A/D converter 101 receives the self-calibration signal sent by the microcontroller, and the REF end of the A/D converter 101 is connected to the OUT of the reference voltage chip 103 The terminals are connected, and the START terminal of the CPLD 102 receives the A/D conversion start signal sent by the single-chip microcomputer, and the AD _0-7 of the CPLD 102 are connected with the parallel port of the single-chip microcomputer.

Compared with the prior art, the beneficial effect of the present invention is: the water level information is sent to the specified mobile phone user through the GSM short message module and its wireless network, and the mobile phone user is also supported to use the GSM network to actively ask for the water level value of each point at any time, and the information is released. Real-time, fast, and strong human-computer interaction; the data acquisition module adopts the "single-chip microcomputer + CPLD" architecture, so as to improve the speed of data acquisition while effectively reducing the complexity of peripheral digital circuits and improving the reliability of hardware circuits; the system The FIR filter based on the median filter of the single-chip microcomputer is used to suppress the "glitch" phenomenon to a greater extent, improve the signal-to-noise ratio, and make the signal waveform smoother, which has the advantages of easy implementation and absolute stability of the system. The invention has the advantages of low cost, high precision, strong anti-interference ability and friendly human-computer interaction.

Description of drawings

Fig. 1 is a structural diagram of the ship lock multi-channel water level measurement system of the present invention;

Fig. 2 is a structural diagram of the drop-in water level sensor of the present invention;

Fig. 3 is the signal conditioning circuit structural diagram of data acquisition module of the present invention;

Fig. 4 is A/D conversion interface circuit diagram of the present invention;

Fig. 5 is a functional schematic diagram of CPLD of the present invention;

Fig. 6 is a flow chart of the main program of the single-chip microcomputer of the present invention;

Fig. 7 is the flow chart of single-chip microcomputer median filter of the present invention;

Fig. 8 is a flow chart of PC FIR filtering in the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the ship lock multi-channel water level measurement system includes upstream water level sensor, downstream water level sensor, lock chamber water level sensor, data acquisition module, RS485 network, 485/232 converter, remote monitoring PC, GSM module, mobile phone user , the data acquisition module includes a signal conditioning circuit A, a signal conditioning circuit B, a signal conditioning circuit C, a multi-way switch, an A/D conversion circuit, a single-chip microcomputer, a power management module, buttons, a digital tube, a TTL/485 conversion circuit, the The upstream water level sensor, the downstream water level sensor, and the sluice chamber water level sensor are connected to the signal conditioning circuit A, signal conditioning circuit B, and signal conditioning circuit C respectively, and the signal conditioning circuit A, signal conditioning circuit B, and signal conditioning circuit C are connected to multiple The switch input terminals are connected, the multi-channel switch output terminals are connected with the A/D conversion circuit, the A/D conversion circuit, the power management module, the keys, and the digital tubes are respectively connected with the single-chip microcomputer, and one end of the TTL/485 conversion circuit is connected with the single-chip microcomputer , the other end is connected to the RS485 network, one end of the 485/232 converter is connected to the RS485 network, and the other end is connected to the remote monitoring PC, the GSM module is connected to the remote monitoring PC and communicates with the mobile phone user through the wireless communication network.

As shown in Figure 3, the signal conditioning circuit A, the signal conditioning circuit B, and the signal conditioning circuit C of this system respectively include an I/V conversion circuit, a follower, and a low-pass filter, and the low-pass filter is Butterworth II Step form, the input end of the I/V conversion circuit is connected to the water level sensor, the output end of the I/V conversion circuit is connected to the input end of the follower, and the output end of the follower is connected to the low-pass filter.

As shown in Figure 4, wherein A/D conversion circuit comprises A/D converter 101, CPLD 102, reference voltage chip 103, described A/D converter 101 model is MAX195, and described CPLD 102 model is EPM7128S, described Reference voltage chip 103 model is MAX6250, and the AIN end of described A/D converter 101 is the input channel of the analog signal to be converted, and the CLK end of described A/D converter 101 is connected with the 4FPCLK end of CPLD 102, and described A The EOC end of the /D converter 101 is connected with the EOC end of the CPLD 102, the CONV end of the A/D converter 101 is connected with the CONV end of the CPLD 102, and the DOUT end of the A/D converter 101 is connected with the CPLD 102 The SDIN end is connected, the RESET end of the A/D converter 101 receives the self-calibration signal sent by the single-chip microcomputer, the REF end of the A/D converter 101 is connected with the OUT end of the reference voltage chip 103, and the START of the CPLD102 The end receives the A/D conversion start signal sent by the single-chip microcomputer, and the AD _0-7 of the CPLD 102 is connected with the parallel port of the single-chip microcomputer.

The water level pressure sensor adopted in the present invention outputs a current signal without period and continuous variation in real time. In actual use, the general water level fluctuation frequency is 3-4Hz, and the fluctuation range does not exceed 10cm. The sensor output signal often presents a superposition of a slowly changing standard current signal, a few Hz low-frequency AC signals, and several small-amplitude high-frequency noise components. . At the same time, the on-site operating conditions of the system are relatively complex, and there are various sources of interference, such as the large current impact generated by the start-up and operation of various power equipment in the hoist room of the ship lock station, the fluctuation and waveform distortion of the 220V grid voltage Interference, electromagnetic radiation, current signal attenuation caused by long-distance transmission, overvoltage caused by lightning, etc. Once the above interference invades the input channel of the system, it will undoubtedly increase the data acquisition error or submerge the useful signal components of the sensor, and even destroy the operation of the entire measurement system in severe cases. Therefore, when implementing the present invention, further technical measures have been taken in terms of measurement accuracy, anti-interference ability and working stability of the system.

The present invention uses a high-precision drop-in water level sensor, the internal structure of which is shown in Figure 2. Among them, the Wheatstone bridge is composed of four diffusion resistors with equal resistance formed by ion implantation and laser correction on the silicon elastic diaphragm. When the reference voltage source remains unchanged, if there is pressure on the On a Wheatstone bridge, the bridge is out of balance and its output voltage is proportional to the pressure, thereby converting the pressure signal into an electrical signal. The constant current source is the constant current excitation required for sensor temperature compensation, and is used for sensor zero temperature drift compensation and sensitivity temperature drift compensation. Since the temperature compensation of the sensor's zero point and full scale is calculated under the condition of no output load, and the resistance of the bridge changes with the temperature, the voltage of the bridge will also change with the temperature in the constant current source excitation mode, so choose The differential normalization amplifier is used to improve the high input impedance and common mode rejection ratio, and the output signal is amplified to a convenient measurement range through the amplifier, and then further converted into a 4-20mA standard current through the V/I conversion, so that the remote distance transmission. The nonlinear correction is to feed back the output voltage through the resistor to control the bridge voltage to compensate the pressure nonlinearity of the sensor. Reverse polarity protection provides protection against damage to the system when the polarity of the power supply is reversed. The water level sensor is a two-wire output, one wire is the input of the positive terminal of the 24V DC power supply, and the other is the output of the 4-20mA standard current signal terminal. The water level sensor has a range of 0 to 10 meters, an operating temperature of -20 to 80°C, an accuracy level of 0.2% FS, and a non-linearity of 0.06%.

The RS-485 network adopted in the present invention has the advantages of simple structure, strong expansibility and the like. However, due to the complex engineering environment, there are often various sources of interference on site. Considering the stability of the system and the reliability of 485 communication, this invention uses a photocoupler to electrically isolate the 485 network from the data acquisition module. In order to protect the 485 transceiver from being broken down, a voltage regulator tube is used at the transmission end of the 485 bus to form an absorption circuit. At the same time, there may be an extreme situation where the 485 transceiver of a certain node is broken down in the line. Since there are two resistors in series at the 485 signal output end, the hardware failure of this node will not affect the communication of the entire 485 network. The beginning and end of the 485 bus are each connected with a 120Ω matching resistor, which can reduce the reflection of the transmission signal on the line. Considering that the system may crash and the 485 chip is always in the sending state and occupies the bus, grounding the sending enable end of the 485 transceiver can ensure the reliability of the 485 communication.

The present invention also adopts corresponding measures in the A/D converter of the data acquisition module, the multi-way switch type selection and the interface circuit design thereof: the multi-way switch chip MAX4598 adopted has lower conduction resistance, is compatible with TTL logic input, The leakage current is only 0.1nA; the A/D conversion chip MAX195 used is a successive approximation 16-bit analog/digital converter, which has the characteristics of high precision, fast speed, low power consumption, self-calibration, and three-state serial data output . When working, the chip adopts the synchronous conversion transmission method, that is, the converted last data bit is serially output during the A/D conversion process (high bit first). The conversion reference voltage is provided by the low-noise, precise reference power chip MAX6250; the A/D conversion circuit is equipped with a custom-made metal shield, which is welded on the printed circuit board, which can shield field interference. The system also adopts the power monitoring chip MAX706. When the data acquisition module is powered on, powered off, manually reset and the power supply voltage drops, its internal reset comparator can output a reliable reset signal. At the same time, its internal watchdog circuit also It can monitor the operation of the single-chip microcomputer. If the single-chip microcomputer is not working properly and the program runs away, the watchdog will automatically reset the single-chip microcomputer, so that the data collection will restart. At the same time, the data acquisition module separates the analog circuit from the digital circuit during the layout, and the analog ground and the digital ground are wired separately, and one point is common to eliminate common impedance coupling. At the same time, the power line is thickened, and the ground line adopts a grid system, which can reduce the system's sensitivity to interference signals.

The multi-channel water level measurement system of the ship lock uses high-precision input water level sensors to measure the water level at multiple points such as the upstream, downstream and lock chambers of the ship lock in real time. in contact with water. The water level sensor turns the actual water level into a standard current of 4-20mA. The sensor is a two-wire output mode. One is connected to the positive pole of 24VDC, and the other is a standard current of 4-20mA output to the data acquisition board. The data acquisition module is based on the node The form is attached to the 485 network, which uses high-performance 51 single-chip microcomputer as the core controller, and the peripheral expansion includes circuits such as signal conditioning, multi-way switch, A/D conversion, CPLD device, man-machine interface, and 485 communication interface. Among them, the signal conditioning circuit mainly includes I/V conversion, voltage follower and Butterworth low-pass filter, etc. After the standard current is converted by I/V, the voltage follower is used for impedance matching to improve its ability to carry the load; the low-pass filter adopts the second-order form of Butterworth to filter out the high voltage caused by power frequency signals and environmental interference. frequency noise; the filtered three-way sensor signals are respectively sent to the three input channels of the multi-way switch, and then connected to the A/D converter, and the 16-bit conversion result is output in serial format; the multi-way switch performs upstream and downstream Automatic switching of different water level measurement points such as sluice chamber and sluice chamber realizes time-sharing roving detection of multi-channel analog signals by a single A/D converter. The A/D converter adopts a successive approximation type 16-bit serial output analog/digital converter, which has a built-in sample and hold circuit and has a self-calibration function, which can convert the previous round of converted data bit strings at the same time as the current round of conversion. Line output to achieve maximum conversion transmission speed, the reference voltage required for conversion is provided by an off-chip low-noise, high-precision reference voltage source. The CPLD chip is mainly used to generate A/D logic control signals, data format conversion for serial input/parallel output of A/D conversion results, and port address decoding, etc., to ensure that the single-chip microcomputer reads 16 bits in parallel in two times according to the off-chip port access mode. Conversion results; the man-machine interface is equipped with buttons and digital tubes, and the buttons and digital tubes are used together to display the water level value of the corresponding measurement point and facilitate system debugging and self-test; the reset circuit supports power-on reset mode, and also Equipped with a reset button for manual reset of the system; photoelectric isolation effectively isolates the serial communication between the MCU and the 485 bus. The isolated signals include the serial port signals RXD and TXD of the MCU and the I/O signals used to control 485 transceivers ; TTL/485 conversion is composed of MAX485 chip, etc., and its A and B terminals are differential signals suitable for remote transmission, which are directly connected to the 485 bus, so that the water level data of each measurement point can be remotely uploaded to the upper monitoring PC.

Because the CPLD has abundant logic resources and its programmable characteristics in the system, the data acquisition module of the present invention adopts the architecture of "single-chip microcomputer + CPLD", so as to effectively reduce the complexity of peripheral digital circuits while improving the data acquisition speed. Degree, improve the reliability of the hardware circuit. Here we focus on the A/D conversion interface circuit and CPLD related function design in the data acquisition module. This module adopts high-precision A/D chip MAX195 for analog/digital conversion. It is based on successive approximation principle, 16-bit conversion accuracy, 9.4us conversion time, built-in sample and hold circuit, and has self-calibration function. bit output. MAX195 adopts synchronous conversion and transmission mode, which can output the converted last data bit during the process of analog/digital conversion, so as to realize the maximum conversion and transmission speed. Its interface circuit is shown in Figure 4. Among them, AIN is the input channel of the analog signal to be converted, CONV is the start conversion signal, EOC is the status signal used to judge whether the conversion is over, CLK is used as both the conversion clock and the serial data output clock, and DOUT is on the falling edge of CLK Output the 16-bit conversion result bit by bit in a serial manner from high bit to low bit. START and RESET are the A/D conversion start signal and self-calibration signal sent by the microcontroller respectively. At the same time, the module uses CPLD chip EPM7128S to design some digital circuits, and its top-level principle is shown in Figure 5. Perform "OR" operation on the START signal sent by the microcontroller and the 4FPCLK signal generated by the external active crystal oscillator after frequency division by 4 to generate the real A/D conversion start signal CONV, and at the same time convert the converted serial data Input from the SDIN terminal and shift the data bit by bit into two cascaded 8-bit shift registers 74595 according to the level change of the SRCLK terminal. bit conversion result. The above-mentioned control signal and status signal have the following logical relationship:

SRCLK=4FPCLK&EOCCONV=START+4FPCLK,

SRCLK=4FPCLK&EOC

The single-chip software programming in the data acquisition module adopts C51 language modular design, the program structure is clear, and it is convenient for system maintenance and upgrading. Only the main program of the one-chip computer and the A/D conversion program are described here. Among them, the main program flow chart is shown in Figure 6, which mainly completes the work of system initialization, data acquisition, digital filtering, scale transformation and man-machine interface management. After the system is powered on, the timer and the serial port should be initialized, and the data acquisition command will be sent by the upper PC at any time. In the loop body, the online median filter is first performed on the water level data of each channel, and then the digital value is converted into a water level value through scale transformation, and the key is scanned while waiting for the serial port to be interrupted. If a key is pressed, it will be recognized Press the key, and the digital tube displays the water level value of the corresponding channel; the interrupt service routine related to A/D conversion mainly includes the timer overflow interrupt (setting the sampling frequency) and INT0 external interrupt (reading the conversion result from the CPLD), And realize multi-channel switching, start A/D conversion and other functions. The A/D sampling period adopts the hardware timing/counter T0 overflow interrupt and the software counter in the single chip microcomputer to realize together. The use of external interrupt INT0 to repeatedly sample the same measurement point is to prepare for the subsequent median filter. Here, the single-chip microcomputer adopts the median filter based on the "bubble sorting" algorithm to eliminate individual "bad points" that may exist in the signal, that is, to continuously sample a certain parameter for multiple times, and then sort these sampled values, select The middle value is the effective sampling value of this time. Its implementation process is shown in Figure 7. This algorithm has the characteristics of convenient calculation, fast speed and small storage capacity.

The remote monitoring PC mainly completes the communication between the upper and lower computers, FIR (Finite Impulse Response, finite impulse response) filtering, database management, operation of the GSM short message module, and multi-point water level display. Using VB as a development tool on the PC to solve the problem of realizing the system operation interface, the interface mainly includes system operation instructions, upper and lower computer connection instructions, upper and lower computer communication content display, current multi-channel water level display, and management of sending and receiving short messages, etc. . Because the structure of this system is relatively simple and the data source is relatively single, the Access database is selected as the background database and connected with Data Access Object (DAO) technology. Among them, the database is mainly used for the record of historical water level and the management of designated user groups of the ship lock (lock staff and boat people). It should be noted that the FIR filter of the PC is based on the median filter of the single-chip microcomputer, so as to suppress the "glitch" phenomenon to a greater extent, improve the signal-to-noise ratio, and make the signal waveform smoother. While ensuring that the amplitude characteristics meet the technical requirements, the FIR filter has strict linear phase characteristics, and has the advantages of easy implementation and absolute stability of the system. Generally, there is a convolution relationship between the output y(n) of an N-order FIR filter with constant coefficients and the input sequence x(n), and its system difference equation is

$\mathrm{the\; y}\left(\mathrm{no}\right)=x\left(\mathrm{no}\right)*h\left(\mathrm{no}\right)=\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(m\right)h(\mathrm{no}-m),$ 0≤n≤N

In the formula: x(n) is the input signal sequence; y(n) is the output signal sequence; h(n) is the unit impulse response of the system, for a filter with a linear phase, the coefficient is evenly symmetrical, that is, h(n)=h (Nn-1). Applying the window function method to design FIR filters has the characteristics of convenient modification of filter parameters, simple calculation, high precision, and easy implementation. The basic design idea is to make the actual filter to be designed approach the ideal characteristics. The present invention aims at the frequency components and characteristics contained in the actual water level signal, in order to effectively eliminate the influence of high-frequency burr interference on the true value of the water level, the typical parameters of the designed low-pass filter are: sampling frequency f _s =150Hz, passband cut-off Frequency f _p =5Hz, stop band start frequency f _st =15Hz, stop band attenuation not less than -50dB, window function type using Hamming window, filter order N=30. The FIR filter design and online filtering process are shown in Figure 8, the method includes the following steps:

1) Carry out finite impulse response filtering on the measured parameters, first give the frequency characteristic Hd(e ^jw ) of the ideal filter;

2) Compute the unit sample response of the ideal filter,

3) Set filter form, window function type, window length N;

4) Call the MATLAB function to calculate the filter coefficient w(n);

5) Calculate the unit sampling response h(n)=h _d (n)w(n) of the designed filter;

6) Store the designed N h(n) sequences into the corresponding storage area;

7) Store the median filtering result x1 as x(n) into the corresponding storage area;

8) Circularly read h(n) and x(n) values for convolution operation to obtain online filtering results

The remote monitoring PC is also connected to the 485 network in the form of a node. Its man-machine interface adopts VB language programming, and the background adopts the ACCESS database, which can display the real-time water level information of each measuring point and automatically save it in the background database. Manage the designated mobile phone user groups, send and receive short messages, etc., and can conveniently perform operations such as adding and subtracting, querying, statistics, report generation, and printing. The data acquisition module and the remote monitoring PC are connected by RS485 bus. During the data transmission process, automatic conversion between different communication standards of TTL/RS485/RS232 will be carried out. The system has good scalability.

The GSM short message module TC35 is connected to the PC through the RS-232 serial port, and the PC controls the GSM module to receive and send short messages by bidirectionally transmitting commands and data in the AT command format. The communication test method between the module and the PC is as follows: 1) RS232 serial port connection. Since TC35 has its own RS232 serial port, it only needs to be connected to the PC serial port. In the self-editing software environment on the PC side, select the corresponding serial port number, and set its parameters as: baud rate 9600bps, no parity bit, 8 data bits, 1 stop bit. 2) Set parameters and connect test. Enter the AT command, if it returns OK, it means that the computer and the GSM module have been connected successfully, and the GSM module can work normally. In order to realize the function of sending and receiving short messages, the GSM module needs to be set as follows: input the command AT+CSCS="UCS2", if it returns OK, it indicates that the character set used by the terminal device is successfully set to "UCS2"; input the command AT+CACA? , such as returning +CSCA: "<sca>",<tosca> (where sca is the address of the character-type short message center, and tosca is the address of the integer-type sca) indicating that the nearest short message service center has been found and a communication connection can be established; enter the command AT+CMGF=0, if it returns OK, it means that the short message mode is successfully set to PDU mode; input the command AT+CNMI=2, 1, 0, 0, 1, return OK, it means that if a new short message arrives, the GSM module will automatically return to the prompt. 3) Send and receive short messages. Enter the command AT+CMGS=X, where the size of X is equal to the number of characters sent plus 15 and expressed in "UCS2" format, and then input the processed Unicode string and send it to the GSM module to execute the sending; such as the GSM module When a short message is received, it will return the data to remind, the format is: +CMTI: "SM", <index>, the PC can extract the information by sending the command AT+CMGR=index, where index is the storage location of the unread information .

In the present invention, two-way short message interaction can be carried out between the specified mobile phone user and the system, that is, the passive receiving mode and the active requesting mode of the user:

1) Passive receiving mode: The system operator can set multiple timing sending time points in the industrial computer program according to the actual needs. When the set time arrives, the system will automatically send the water level data of each measuring point at this time to the Specify the mobile phone user group. At the same time, the system operator can also manually send other edited short messages at any time;

2) The way the user actively requests. At any time, mobile phone users can also send short messages to the GSM module installed in the industrial computer to obtain the latest water level information. When the user sends a short message to the GSM module, the industrial computer will first perform identity verification, and immediately reply to the current water level after passing the identity verification; if it fails, no further information will be sent. With this design, the system can block invalid short messages sent by non-designated users, thereby reducing system operating costs and improving the pertinence and effectiveness of ship lock services.

In addition to the above-mentioned embodiments, the present invention can also have other implementations, and all technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (4)

1. ship lock Multi-channel water level measuring system, it is characterized in that, comprise the upper pond level sensor, level of tail water sensor, the lock chamber level sensor, data acquisition module, the RS485 network, 485/232 converter, the remote monitoring PC, gsm module, the cellphone subscriber, described data acquisition module comprises signal conditioning circuit A, signal conditioning circuit B, signal conditioning circuit C, multi-way switch, the A/D change-over circuit, single-chip microcomputer, power management module, button, charactron, the TTL/485 change-over circuit, described upper pond level sensor, level of tail water sensor, the lock chamber level sensor respectively with signal conditioning circuit A, signal conditioning circuit B, signal conditioning circuit C links to each other, described signal conditioning circuit A, signal conditioning circuit B, signal conditioning circuit C links to each other with the multi-way switch input end, the multi-way switch output terminal links to each other with the A/D change-over circuit, described A/D change-over circuit, power management module, button, charactron links to each other with single-chip microcomputer respectively, described TTL/485 change-over circuit one end links to each other with single-chip microcomputer, other end access RS485 network, described 485/232 converter, one termination enters the RS485 network, another termination remote monitoring PC, described gsm module links to each other with the remote monitoring PC and communicates by letter with the cellphone subscriber by cordless communication network.

2. ship lock Multi-channel water level measuring system as claimed in claim 1, it is characterized in that, described signal conditioning circuit A, signal conditioning circuit B, signal conditioning circuit C comprise respectively I/V change-over circuit, follower, low-pass filter, described low-pass filter is Butterworth second order form, described I/V change-over circuit input end is connected with level sensor, described I/V change-over circuit output terminal links to each other with the follower input end, and the follower output terminal links to each other with low-pass filter.

3. ship lock Multi-channel water level measuring system as claimed in claim 1 or 2, it is characterized in that, described A/D change-over circuit comprises A/D converter (101), CPLD(102), reference voltage chip (103), described A/D converter (101) model is MAX195, described CPLD (102) model is EPM7128S, described reference voltage chip (103) model is MAX6250, the AIN end of described A/D converter (101) is the input channel of simulating signal to be converted, the CLK end of described A/D converter (101) links to each other with the 4FPCLK end of CPLD (102), the EOC end of described A/D converter (101) links to each other with the EOC end of CPLD (102), the CONV end of described A/D converter (101) links to each other with the CONV end of CPLD (102), the DOUT end of described A/D converter (101) links to each other with the SDIN end of CPLD (102), the RESET termination of described A/D converter (101) is received the self calibration signal that single-chip microcomputer sends, the REF end of described A/D converter (101) links to each other with the OUT end of reference voltage chip (103), the START termination of described CPLD (102) is received the A/D conversion starting signal that single-chip microcomputer sends, the AD of described CPLD (102) _0～7Link to each other with the parallel port of single-chip microcomputer.

4. the filtering method of ship lock Multi-channel water level measuring system as claimed in claim 1 is characterized in that the method may further comprise the steps:

1) measured parameter is carried out medium filtering, namely to measured parameter continuous sampling repeatedly, sampled value is sorted, choosing intermediate value is this efficiently sampling value;

2) measured parameter is carried out finite impulse response filter, first the frequency characteristic Hd (e of given ideal filter ^Jw);

3) unit sample respo of calculating ideal filter,

4) filter form, window function type, length of window N are set;

5) Calling MATLAB function calculation coefficients w (n);

6) the unit sample respo h (n) of calculating filter=h _d(n) w (n);

7) deposit N h (n) sequence that designs in the corresponding stored district;

8) deposit median-filtered result x1 in the corresponding stored district as x (n);

9) h (n) is read in circulation, x (n) value is carried out convolution algorithm, tries to achieve online filtering result

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