Design of shipborne monitoring system based on ARM9

The coastal zone is the most sensitive part of the ocean to human activities, and human activities will have a serious impact on the structure and function of its ecosystem. This makes the coastal zone a vulnerable area of ​​marine ecological environment. Therefore, the safety and management of the coastal zone has become a hot research field internationally. The scientific management of the coastal zone is based on a large amount of data. Traditional coastal zone surveys require a lot of manpower and material resources, and the data obtained is very limited. High-throughput coastal zone data acquisition has become the main bottleneck restricting the scientific management of the coastal zone.

Countries with a high level of marine research, represented by the United States and the European Union, have developed various forms of marine monitoring systems, such as buoys, towed monitoring ships, underwater gliders, satellite remote sensing, and seabed observation stations to obtain massive data.

Here, a new method for collecting marine data is introduced, and a collection system, the ship-borne monitoring system (Automated Instrument Packages on Ships of Opportunities), is developed. It is

a marine data acquisition mode that integrates multiple marine environment monitoring sensors. As the ship sails, it conducts real-time sampling along the entire route. The data obtained can be directly transmitted to the data center through remote transmission, or stored on the ship and obtained regularly.

Compared with other marine data acquisition systems, the ship-borne monitoring system has the following advantages:

(1) Adequate energy. The ship can provide energy for the system, which is convenient for the application of more complex analysis systems. Therefore, different sensors can be used according to different functional requirements to integrate corresponding ship-borne monitoring systems. (
2) Good working environment. The system working conditions can be guaranteed inside the ship, which is convenient for the installation of more sophisticated equipment.
(3) Easy to maintain. No auxiliary maintenance costs are required, and the maintenance cost is low.
(4) The data source is wide and the accuracy is high. Data parameters at different times and spaces can be obtained.

Combining the above advantages, it can be seen that the application prospects of the ship-borne monitoring system are broad. If the system is placed on commercial ships on different routes, the entire coastal monitoring system of China can be established; if it is placed on ocean-going ships, a large amount of ocean surface seawater data can be obtained.

1 System Principle

The system uses ARM9 as the control core and consists of sampling, testing, storage and sending parts. After the system is started, the software controls the start of the pump, and the sensors installed in the water storage device measure the seawater pH, conductivity, dissolved oxygen, temperature and other parameters, and obtain the location parameters by GPS. The seawater parameters and location parameters are stored in the system's own SD card, or the data is sent to the data center via GPRS. The PC or industrial computer in the data center receives the data by the same GPRS, and the data is processed by the data center program and stored in the database. The working principle is shown in Figure 1. 2 Hardware Design 2.1 Box Design The entire system is installed in a stainless steel box, which can protect the system from working normally under certain severe weather conditions. The box size is 555 mm×519 mm×454 mm, divided into three layers, the upper layer is a push-pull distribution box, the middle layer is a water storage tank and water pump, and the lower layer is a battery. The upper cover and the front and rear walls of the box can be opened to the side, and the overall installation and movement are convenient. The structure is shown in Figure 2. Among them, the distribution box is fixed on the slide. After the upper cover is opened to the side, the distribution box can be pushed to the rear side so that the lower equipment can be disassembled or debugged without disassembling other devices. The water tank has water inlet and outlet, upper cover, conical air filter cover and other components. As shown in Figure 2(b) above, seawater flows from the water inlet through the inner tube to the conical air filter cover, and the gas flows from the center of the upper cover to the drain pipe through the connecting hose. Due to the flow factor, a large amount of seawater flows out from the lower edge of the conical air filter cover, thereby reducing the gas entering the water tank to prevent it from affecting the performance of the sensor. The upper cover mainly has a water outlet and a sensor installation port. The reason why the air outlet is located on the upper cover is also based on the consideration of reducing the accumulation of gas in the water tank. A sealing gasket is added between the upper cover and the water tank body, and bolts are connected. The physical appearance of the system assembly is shown in Figure 3. 2.2 Circuit design The circuit part of the system consists of various functional circuits, including power supply circuit, A/D acquisition circuit, sampling isolation circuit, serial communication circuit and ARM core board. The ARM core board is an ordered product. 2.2.1 Power supply circuit The power supply required by the system is complex, including DC 24 V, ±12 V, 5 V, and AC 220 V. All power supplies are provided by 12 V 60 Ah batteries. Among them, 24 V and -12 V power supplies are realized by power modules respectively; 220 V AC power supply is converted by inverter. 5 V power supply is obtained by combining 2576-ADJ chip and 7805, as shown in Figure 4. This circuit has strong load capacity. First, the 2576-ADJ with strong load capacity reduces the 12 V power supply to a suitable value (6.3~8 V), and then the 7805 with better stability obtains 5 V voltage. This can not only meet the high-precision ADC voltage requirements, but also reduce heat generation. 2.2.2 Acquisition circuit The 16-bit high-performance ADC chip MAX11046 occupies the ARM pin GPIO resources as shown in Table 1. 2.2.3 Serial port time-division multiplexing circuit Since the high-performance ADC occupies part of the GPIO resources of the ARM chip, resulting in insufficient system serial ports, the analog switch 4052 is used to time-division multiplex the serial port. Different types of analog switches have different requirements for the conduction voltage of the serial port signal. Among them, if the HCF4052 analog switch is used to conduct the serial port signal, a power supply of more than 10 V is required, while the 74HC4052 switch only needs 5 V to conduct. In addition, the serial port chip RS 3232 can work at a voltage of 3.3 V, while RS 232 is at least 5 V. The serial port time-division multiplexing circuit is shown in Figure 5. 3 Software Design 3.1 ARM-side Program Writing The ARM9 platform is implanted in the WinCE system. The application running under this system is written by EVC. After the program is opened, select the acquisition, storage and sending cycle, and set the SMS center number (with default value). After clicking Start, the system starts to work automatically. First, start the water pump, and wait for a while until the water tank is full of water. Then set the timer and start the operation cycle of reading data, processing data, storing and displaying data, and sending data. During the cycle, if a text message is read, the text message content is parsed. If it is a protocol instruction, the text message is executed and deleted; if it is not a protocol text message, it is directly deleted and the cycle is continued. There is a button on the software to end the system work directly. Its workflow diagram is shown in Figure 6. 3.2 PC-side programming The PC-side program is written in Visual Studio 2010 using C#. It adopts the left-tree and right-table structure and is divided into three parts: user management, terminal management, and data management. The program connects to the database project file established by SQL Server. The database project includes three types of forms: user table, terminal table, and data table. The user management part mainly operates on the user table, which can save and change different user information to determine the user's authority to access ocean data and system operations. The terminal management part can operate on the terminal table and data table, mainly realizing data reception and storage. In order to realize that the data center can be managed by multiple ship-borne monitoring systems at the same time, multiple ship-borne monitoring system numbers are saved in the terminal table to facilitate the classification and storage of marine parameters. The data management part can display the latest received data and output the data within a period of time as a curve, so as to more intuitively see the trend of changes in a certain range of data. In addition, this part can also save the data in the database in common file formats such as Excel, PDF, etc. The communication between the data center and the ship-borne monitoring system is realized through the SMS terminal. The SMS terminal and the PC are connected by a serial port and communicate through AT commands. The software receives SMS by setting the serial port response event. The SMS program flow chart is shown in Figure 7. 4 Conclusion This instrument is based on the ARM9 hardware platform and the WinCE operating system. It integrates a variety of online seawater testing instruments, realizes wireless transmission of offshore waters data through the GPRS module, and is extended with an interface that can be equipped with a 4G SD card, as well as multiple master-slave USB interfaces, which are easy to maintain and debug, meet the requirements of intelligent instruments, and realize the miniaturization, mobility, low cost, and intelligence of the instrument. It can meet the needs of marine scientific research for massive data and has important significance for the study of coastal ecology in China.