The development direction of Siemens PLC
Early electrical automatic control system is widely used in industrial production relay - contactor control system. With the rapid development of industry, the shortcomings of equipment operation of complicated mechanical action, relay control systems have become increasingly prominent .1969, the US Digital Equipment Corporation developed the first programmable logic controller, since then, this new technology quickly used widely in the world. Beginning in 1974, the development of our country, in 1977 began the industrial application. With the rapid development of microelectronics technology, programmable logic controllers began to use general-purpose microprocessors, including the United States, produced by Intel MCS51 series microcontrollers represented.
Early programmable controller is only logical, timing, counting sequence control function, commonly referred to as programmable logic controller’s .PLC After years of development, has been widely PLC all aspects of breakthrough, becoming a major process-oriented system equipment.
PLC main features are: anti-interference ability, high reliability; versatility, can be adapted to most industrial design integrated design of PLC; easy operation and maintenance; PLC programming is easy to learn with the above characteristics is due to make. in the industrial sector have other types of microprocessor products incomparable advantages, resulting in various industrial fields has been widely used. At home and abroad, PLC has penetrated into all areas of industrial control, the application range of the PLC is also expanding.
PLC to the CPU core, it has many of the characteristics of the computer, but it works with the computer, but there are very different. Generally use the wait command computer work, and work is used PLC scan cycle. The user program is stored in chronological order in the PLC, CPU from the first instruction, the instruction step by circulation numbers do periodic scans, if there is no branch instruction, the first instruction from the user program is executed sequentially one by one, until the encounter terminator and then returned to the first instruction, the cycle of the cycle, so called cyclic scanning mode. The length of the scan cycle mainly depends on several factors: First, the speed of the CPU executes instructions; the second is the time it takes to execute each instruction; three is the number of instructions in the program a few bars. After the PLC into working condition, the first input terminal through which the state of the external input devices to collect and store the corresponding input relays, input signal acquisition after, CPU will combine state of the input, step by step according to the statement sort of logic operation, generating determine The output information, and then sent to the output section, thereby controlling the actuator action. After the PLC is powered monitoring system under the program, again and again to a certain order for a variety of tasks within the system to query, judgment and execution, the process is essentially a process of sequential scan cycle.
Siemens PLC is the development trend of miniaturization, modularization, integration.
The shape, size, means of convenient installation and maintenance, system integration occupies less space of the cabinet body. But the small size does not mean that the user functional requirements in the lower, contrary to the users demand more and more, which means the integration of products and higher requirements. A new generation of PLC should be integrated more Siemens operation and maintenance functions, such as the built-in CPU display, can quickly access a variety of text information and detailed diagnostic information, to improve the availability of equipment, but also easy to understand all the information factory; integrated short splicing, convenient for users is more flexible and convenient to establish the potential group; integrated DIN rail, can quickly and easily installed automatic circuit breaker, relay and other components; flexible cables with cable storage methods, the locating slot device designed in advance, even for coarse type cable, can also be easily closed module front cover; integrated shielding clamp, proper shielding of analog signals, which can ensure high quality identification of signal and effectively prevent the external electromagnetic interference.
In structure, flexible expansion of the user recognition modular PLC. In order to meet the needs of various automation, intelligent I/O module with CPU and memory, which can extend the function of PLC, and the use of flexible, extends the application scope of PLC. For the module settings, user requirements between modules connection should be solid and reliable, has a certain degree of vibration resistance, connection is best to use terminal pluggable, without using any tools can realize fast installation module; setting the pre wiring position, through the steering wiring system with positioning function, whether it is the first time the wiring or reconnect, fast and convenient; the wiring plug terminal is best to use a screwdriver and non welded; standard connector, which not only simplifies the wiring operation of cables, but also save more time connecting line. In the aspect of reliability of modular design and product, PLC has always been at the forefront of Siemens. S7-300 is a modular PLC system, each module can be combined to form a wide range of different requirements of the system.
In order to adapt to the development trend of information technology, the PLC network system is no longer the closed systems, but the rapid development of the open system, the major brand PLC in addition to PLC network system to form their own equipment, complete control tasks, but also with the host computer management system, to achieve the exchange of information, become a part of the information management system. On the other hand, the field bus technology has been widely used in the field of intelligent devices, the PLC and other installation, such as intelligent instrument, intelligent sensor, actuator, connected by a transmission medium, and in accordance with the same communication protocol to transmit information to each other, which constitutes an industrial control network, the compared with the pure PLC network remote network, configuration is more flexible, expansion is more convenient, lower cost, performance and price are better, more open significance.
With the urgent demand of various control devices to work together, to PLC Ethernet compatible extensions and further put forward higher requirements to Web technology. Through the integration of WebServer, users may need to visit the site, you can through the Internet browser to view the CPU state, the process variables are displayed in a graphical way to simplify the operation, information collection. Based on this, the user that the S7-1200 as the representative of the new generation of small
PLC, Ethernet has become the industry standard, the network is no longer at the early stage of the luxury goods, but the modern industrial control system, which represents the control system with PLC as the representative of the emerging from the control based on network, become the control based on network.
Even users think, "copper back into the light", "copper back into the wireless network communication era" should lead to a new generation of PLC hardware on the revolution, it is the input and output should be separated from PLC, directly in the field bottom, through the optical fiber or wireless and PLC to signal a new industry standard connection thus, the PLC will return to its "programmable logic process control" essential function. The future, the interconnection of PLC and the intelligent mobile phone, even the configuration of WIFI, and even bring the wireless revolution in industrial field.
With the rapid development of computer technology and enter the field of automation, "a 32 bit processor, processing speed nanosecond, tens of thousands of I/O users believe that," characteristics of the fifth generation PLC have, will be "faster" embodied in the next generation of PLC, so that the future of computing ability and data processing ability of PLC with the PC.
PLC with high reliability, strong anti-interference ability is known, but the modern industry of reliability requirements more and more high, the user is still hope that the next generation of PLC fault detection and processing capacity will be stronger. According to statistics, in the fault of PLC control system, CPU and I/O accounted for only 20%, while the input and output devices, fault accounted for 80%. The former can be realized by hardware and software testing, with PLC software itself, and the external fault to strengthen the special intelligent module development, development for the detection of external fault, to further improve the reliability of the system.
According to statistics, the motion controller based on PLC occupy half of the country general motion controller, these products are based on the platform of PLC, add a stepper motor or servo motor driven single axis or multi axis position control module, to provide for all kinds of machinery and equipment logic control at the same time, provides the function of motion control. The future, the user will be able to recommend the next generation of PLC motion control functions integrated directly into the PLC, without the use of other modules, that more and more strong motion control, which can be connected to the various analog driving speed, support shaft and a positioning shaft.
The application of a variety of automation technology, has created the conditions for a variety of control fusion. For the application for more equipment, user's prospects for the next generation PLC will have a higher degree of integration of hardware and software. For example, PLC combined with CIM, CAD/CAM, robot, personal computer, MIS, PLC occupy a more important position in the future development of factory automation.
In addition, users require a new generation of products with better backward compatibility, seamless upgrade of the system, so as to ensure that the return on investment and investment security to the maximum extent.
Now has PLC applications beyond the switch, control logic and discrete quantity monitoring, has developed into a logic control function, control function, the function of motion control, data processing function, the network communication function of the multi functional controller, analog processing ability is more and more strong, and the other is in the past only to advanced computer processing capabilities, such as floating point arithmetic, PID control, temperature control, precise positioning, step motor drive, statistics etc.. In this sense, the future of the PLC will be from the "controller" was promoted to a new generation of multifunctional control platform. On behalf of the OMRON LOGIX platform, Rockwell NJ platform this trend.
The user is no uniform standard for most of the problems of programming software. An engineer complained: "into the industrial sector, and a variety of industrial products to deal with every day, a lot of software installed on the computer, very convenient, more trouble is every time to re install the system, all the software must be installed again, waste a lot of time." In practical work, there are a few days ago by the engineer to reflect the PLC programming software to write a program, after a few days, but also with the PC configuration software SCADA development system, to the scene to use software setting and debugging device drivers.
This not only need to install and learn different software platform, but also between different software platform configuration of complex communication, repeated data input data and, which directly affects the work efficiency is also prone to human error. Therefore, I hope the automation manufacturers introduced software platform can be compatible with the relevant products of automation and drive, in order to reduce the complex application problems.
In the software to improve the software view, add, helpful tips and software operation is too complicated is user problems. Engineers often use the notebook computer when debugging equipment, but a laptop computer screen is too small, thus affecting the image display, inconvenience for users to browse the program. In view of the optimization software, users hope that manufacturers can provide comprehensive view size adjustment, and can customize the interface on the flexible layout. In addition, the software prompts the user to add help, not familiar with the function, can help engineers to improve the efficiency of programming. Engineers think that, at present Siemens in this respect do more in place, especially for those unfamiliar Siemens users, help prompt function can improve programming efficiency.
Simple programming, software interoperability, call the software integration platform, users even said, "the PLC software in waiting for a similar to the Microsoft windows as the breakthrough, to create a new era of PLC". Leading automation market in the hardware, can already see the integration design software - hardware platform software, this is the beginning, with the software to enhance the value of the automation system, the future of software automation platform real or anticipated.
In the traditional view, the user to purchase PLC products procurement and total cost of ownership (TOC TotalOperationCost), now, fast time to market, reduce the operation cost has become an important index to enhance market competitiveness, the life cycle of PLC has become a new focus of user attention.
The PLC life cycle including equipment selection, purchase, installation, maintenance, repair, service and other links, users hope that the life cycle of PLC tends to be more reasonable, that the design, selection, development, debugging, maintenance, more simple, more user-friendly; and time, more reliable in design, selection, development period,, but time is shorter; and in the operation and maintenance phase, more simple, and longer life. "We spend less time in the design and development, focus on the process optimization, capacity optimization, energy conservation and other aspects, wouldn't it be better?"
At the sight of the future PLC more conducive to life cycle long and short in front of the functions and services, for example, adding liquid crystal panel, during debugging, more convenient to know what the problem is. In the maintenance phase, can be more intuitive to see the situation. To reduce personnel costs, increase reliability; for instance, since joining the function maintenance and remote diagnosis function, also can reduce the maintenance cost.
Changes in the needs of the development of PLC driver and user expectations, the development direction of the new generation of Siemens PLC has begun to take shape. The performance is more and more strong, the function is more and more, PLC will be able to adapt to the more complex control tasks; network communication become the standard, PLC control system will be gradually integrated into the management information system for plant automation and enterprise; design software tends to be more simple, platform software trend can be expected; installation, debugging, maintenance, diagnosis more convenient PLC, the use of more simple, and the application of more intelligent. Therefore, a new generation of Siemens PLC change more than reflected in the function and performance of the traditional, more reflected in the product platform, enterprise system integration and whole life cycle value. Only this, the new generation of Siemens PLC can more satisfy various kinds of industrial automation and control applications, industrial control platform of a hundred years is not bad.
