Design of remote control system of marine main eng

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Design of marine main engine remote control system based on programmable controller

1 introduction

an important part of marine automation is the main engine remote control system. At present, there are many technical schemes of the host remote control system. This paper uses PLC industrial control network to realize the function of the host remote control system, which has the characteristics of good economic performance, simple hardware circuit structure, safe and reliable work

based on the design of the host remote control system realized by multiple PLC control networks, the discussion mainly designs the overall structure and communication scheme of the whole PLC network, and realizes the automatic control of the start and stop part of the host and the design of the security system through the communication network

2 overall structure design of host remote control PLC network control and Realization of communication mode

2.1 overall structure design of host remote control PLC network control

plc control network is used for the control of host remote control system, including two splcs. One of them is used for the start and stop of the main engine and speed regulation control, and is installed in the machine control room; The other one is used to complete the task of electronic governor and is installed in the engine room. Another computer is set as the monitoring platform to monitor the important signals of the whole system

the main equipment of the whole network is: two splcs, one microcomputer, network connector, pc/ppi cable, RS-485 cable

according to the overall communication design idea, our overall structure diagram design is shown in Figure 1

Figure 1 overall structure diagram

as shown in the figure, the ground bus from the master station PLC communication port communicates with the slave station PLC and computer through the network connector and pc/ppi cable respectively. PPI protocol communication is carried out between master and slave stations through RS-485 bus, and free port communication is carried out between master station and computer terminal through pc/ppi cable. The purpose of connecting the upper network connector from the PLC communication port of the master station is to isolate and avoid the damage of the computer RS-232 port. The ground wire and RS-485 signals a and B come out through the network connector to communicate with the slave station by comparing the high and low levels. At the same time, five pins are led out through the connection port of pc/ppi cable, and are converted into three lines through RS-485 and RS-232, which are respectively receiving, transmitting and ground wires, to communicate with the computer. See the attached table for the pin distribution of SPLC communication port. This kind of electronic universal testing machine usually refers to a fully automatic electronic universal testing machine without manual participation, which automatically loads and discharges materials and is clamped by an automatic extensometer The pin division of the communication port in the attached table also makes the market of recycled plastic granulator more and more optimistic. It is equipped with the combination and debugging of

2.2 multiple communication protocols

in s-network communication, two communication protocols can be realized to communicate without mutual interference. But the premise is that the baud rate of the two protocols must be the same. Because there is only one communication port, the baud rate only supports 9600 baud. Therefore, in multi protocol communication, the baud rate is set to 9600 baud. For the combination of multiple protocols, the author adopts the bus time-sharing method. In the bus time-sharing control, the author forms a rectangular wave through several timers, so as to form PPI Protocol Communication and free port communication in different periods of time. See Figure 2 for the main program flow chart. See Figure 3 for PPI communication procedure flow. The flow of free port communication program is shown in Figure 4

see Figure 2 for the flow chart of the main program

Figure 3 for the flow chart of PPI communication program

Figure 4 for the flow chart of free port communication program

according to the above scheme, more than half of the production capacity needs to purchase spodumene concentrate. After the system design is completed, the actual communication effect meets the design requirements, and the slave station PLC and computer terminal can basically obtain the information sent by the master station within 20ms

3 design of host remote control system

3.1 design of start and stop part

the object selected by the author in the design process is the most common b&m low-speed machine. The start and stop control mainly includes five parts: start control, slow rotation control, stop control, repeated start control. Taking the forward starting as an example, the system must aim at two situations: the starting under parking and the normal reverse starting, which can ensure the on-off of the forward starting solenoid valve, and at the same time, it must also judge the status of repeated starting. The program flow of forward starting is shown in Figure 5

Figure 5 program flow of positive starting

slow rotation control should consider two situations: the shutdown time of the host exceeds 30min and the restoration of power supply after power failure. The slow rotation control can be cancelled when the main engine turns around without adjusting the speed or there is an emergency control signal. There are four kinds of situations to be considered in the parking control: Parking command, fault parking signal, inconsistency between the driving order and the running direction, and the working period of the starting solenoid valve. Repeated starting control is divided into four subprograms: starting time monitoring subprogram, reversing time monitoring subprogram, starting intermittent delay subprogram and repeated starting number counting subprogram. Due to space limitations, the above procedure flow chart will not be repeated here

3.2 design of speed control part

this design uses the analog input module EM235 to read the car clock command and speed feedback. The PLC master station first reads the analog quantity, and through three shifts, it can get a 12 bit digital signal, and then digitally filters the input quantity through the timing interrupt program. The filtered data will be compared with the normal signal voltage range determined by the external circuit, and it can judge whether there is a wire break fault at the three terminals of the vehicle order potentiometer. After ensuring the normal signal, it will undergo various restrictions, The limiting link mainly includes critical speed limit, acceleration limit and load program limit. The results of the limit processing are finally sent to the PLC electronic governor of the slave station through PPI communication protocol to control the speed of the host machine. The flow chart of speed limit processing procedure is shown in Figure 6

Figure 6 flow of speed limit processing program

another task of this design is to read the speed feedback value and process it. After processing, we can get various operating states of the host, including the forward and reverse reversing reversing speed of the host, the firing speed and the acceleration conversion point. On the one hand, we can get the host state information required for start and stop control, on the other hand, we can make the monitoring platform monitor in real time and intuitively reflect the current status of the host, At the same time, it can display the whole speed change process

4 conclusion

combined with the requirements of the host remote control system in the maintenance and reconstruction of small and medium-sized ships, this paper puts forward a design and implementation scheme of the host remote control system with relatively simple hardware circuit, easy implementation, few lines, easy programming and comprehensive functions. The system adopts two splcs and one computer to form the basic framework of the host remote control system, and the serial communication bus can realize the information transmission between each controller and computer. At present, the design and debugging of the system have been completed in the laboratory environment

this article is extracted from plc&fa (end)

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