Intelligent sensor and FCS technology for monitoring and control design
Ora pubblicata: 2020-03-23 11:01:04
With the development of computer technology and the advancement of sensor technology, the shortcomings of traditional sensors have become increasingly prominent. In order to maximize the potential of existing submarine equipment, improve combat capabilities, and increase survival probability, it is necessary to form a fieldbus control system based on intelligent sensors.
1. The main method to realize the intelligence of submarine equipment sensors
1.1 Replace traditional sensors with smart sensors
Currently, there are three types of smart sensors: ① using non-integration; ② using integration; ⑧ hybrid implementation. For this reason, the realization of sensor intelligence should be based on non-integrated intelligent sensors, supplemented by integrated intelligent sensors as appropriate. The measures are as follows:
(1) Non-integrated transformation of pressure, temperature and humidity sensors. It can be made into a non-integrated smart sensor by adding signal conditioning circuits, single-chip microcomputers and digital bus interfaces. This method can not only realize the intelligence of the sensor, but also make full use of the original sensor resources. It is a most convenient and effective method and saves costs.
(2) Install a gas sensor. The atmospheric composition in submarines is relatively complicated, and dozens of species can be detected, as shown in Table 1. There are few atmospheric monitoring equipment for submarines, and no network is formed. There is no equipment monitoring for the exhaust gas after missile launch. In order to ensure the safety of the submarine and the health of the crew, an intelligent gas sensor can be installed to monitor the above gases.
(3) Improve the working method of the depth gauge. In order to overcome the shortcomings of the traditional depth gauge during the sounding process, an intelligent pressure sensor can be installed outside the boat to convert the physical signal into a digital signal and transmit it to the boat, so as to ensure that the submarine accurately understands the depth of the submarine. The choice of pressure sensors includes capacitive pressure sensors and piezoresistive pressure sensors. Generally, capacitive pressure sensors are more sensitive than piezoresistive pressure sensors (Sc is about 50 times higher than Sr), so a capacitive pressure sensor should be selected as the depth. Sensitive components of the meter.
(4) Constructing a full-boat intelligent sensor system. Should focus on building three full-boat intelligent sensor networks:
(a) Intelligent sensor network for cabin pressure monitoring in the whole ship;
(b) a whole-boat gas monitoring intelligent sensor network;
(c) Whole-boat temperature intelligent sensor network.
1.2 Using Fieldbus Control System (FCS)
The use of smart sensors requires a field that transmits digital signals to communicate between the underlying equipment and the control layer. The smart sensors and field bus together form the field bus and form the field bus control system (FCS).
Considering the special environment of submarine cabins, the explosion-proof requirements of battery compartments and torpedo compartments for field instruments, and the information flow of the entire boat, a PROFIBUS bus with mature technology, a large market share, and intrinsically safe bus should be selected as the underlying intelligent sensor in each mainstream bus Information exchange bus with workstations.
2. Overall technical plan
2.1 Network Structure
Because each cabin of the submarine is relatively independent, the crew can control the equipment in this cabin, and can transmit the bottom digital signal to the command cabin to realize the monitoring and control of the whole boat system. Therefore, a three-layer linear network structure should be adopted. The first layer: Ethernet (ETHERNET). Realize the data transmission from the workstations in each cabin to the command cabin. The command cabin can be used for data acquisition, exchange and monitoring by this network; the second layer: PROFIBUS fieldbus network, the network topology is a linear bus type, and it is connected by shielded twisted pair. It consists of PROFIBUS-DP and PROFIBUS-FMS, and adopts intrinsically safe PROFIBUS-PA in explosion-endangered areas. Because PROFIBUS-DP and PROFIBUS-FMS systems use the same transmission technology and bus access protocol, the system can operate simultaneously on the same cable. In order to connect the intrinsically safe PROFIBUS-PA to the bus, a segment coupler is available. The third layer: AS-I interface network layer. The AS-I bus is used for the networked communication of sensors and actuators, and can be used as a manipulation actuator. Depending on the data traffic, data can also be transmitted using optical fibers.
2.2 working principle
The PROFIBUS-DP bus in this network is used for high-speed data transmission between the intelligent sensors at the bottom of each cabin and the cabin master station (PLC). The cabin master station (PLC) reads the input information of the slave station (smart sensor) periodically and sends the output information to the slave station periodically. The bus cycle time is shorter than the master program cycle time. In addition to periodic user data transmission, PROFIBUS-DP also provides acyclic communication required for intelligent field devices for configuration, diagnostics, and alarm processing. The access method of the bus is the token transfer between the master stations in each cabin, and the master-slave transmission between the master station and the slave stations. Single-master or multi-master systems can be used. The communication method is point-to-point (user data transmission) or broadcast (control instruction), cyclic master-slave user data transmission and acyclic master-master data transmission. The system has powerful diagnostic functions. The bus assigns an address to the PROFIBUS-DP slave. The maximum input and output data for each slave is 246 bytes.
The brand bus protocol is a multi-master protocol. A token-holding master station can use tokens and query other master stations. After a master station gets the token, the master station can communicate with the slave station or other master stations within a certain time. The token cycle should ensure that there is enough time to complete the communication task. PROFIBUS-DP completes periodic and aperiodic data exchange in this way. The PROFIBUS-DP protocol settings include: ① a periodic timer that counts the actual running cycle of the token: ② a licensed timer that counts the token holding time.
2.3 Work flow
The main station (PLC) of each cabin performs data transmission with the smart sensor in a token mode through the PROFIBUS-DP bus. According to the data obtained by the smart sensor, the crew can control the underlying equipment through the main station to realize the monitoring of the implementation devices of the cabin. . The command cabin can collect, analyze, and monitor the data of each cabin through Ethernet (ETHERNET), and need to control the implementation devices of each cabin.
This bus system uses tokens for data transmission. When the network load is light, the efficiency is low, and the tokens need to be maintained to avoid token loss or duplicate tokens. The control circuit of this method is more complicated.Etichetta: sensor