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Control system I/O technical characteristics

Apr. 19 ,2024

The universal I/O technology of the control system means that the I/O module has good versatility. The same I/O point can be configured as AI, AO, DI, DO, or even more signal types. For the universal I/O technology of the control system, compared with the universal input technology of the display introduced above, the "universal" object has been extended from "input" only to "output". Compared with the IMP remote measurement and control terminal, the universal The object has expanded from analog quantities with only input and switching values with both "input" and "output" to analog quantities and switching values with both "input" and "output".

When it comes to general-purpose I/O technology in control systems, it is usually thought that it started with the introduction of electronic wiring by Emerson Process Management in 2009. Three to five years or more later, foreign Honeywell, Yokogawa, ABB, Schneider Foxboro, Pepperl+Fuchs, Eaton, Phoenix, and Computrols have all launched general-purpose I/O technology. In recent years, domestic Hollysys Lai has also launched products applying this technology.

Characteristics of general I/O technology for control systems

The traditional control system wiring method is to use a single cable to connect the field equipment to the field instrument box, and then aggregate it into multi-core cables and transmit them to the wiring cabinet in the control room, and then through complex cross-wiring and the I/O of the control system. O module connection. General-purpose I/O technology uses a single cable to connect field devices to a centralized wiring cabinet or field instrument box. After aggregation, it is usually connected to the control system via fiber optic Ethernet. Improvements in wiring methods and I/O technology have given the control system general I/O technology the following characteristics:

Just as the universal input function of the display can reduce the workload of design selection, the universal I/O technology of the control system can also reduce the workload of design selection. The design process does not consider which I/O module to choose. Various I/O points can be installed in a nearby wiring cabinet or instrument box. At the same time, the outlet terminal wiring of the wiring cabinet or instrument box has been gathered into a bus for transmission. There is no need to mark the number of the outlet lines one by one, and the workload of drawing, reviewing, and proofreading is also greatly reduced. Figure 30 compares the schematic diagram of I/O module configurations between traditional cabinets and universal cabinets. The different color mixed configurations representing various I/O modules in traditional cabinets need to be carefully designed and checked, while the universal cabinet I/O module configuration is a A single configuration represented by color does not require design and verification except quantity.

In the past, the manufacturer's wiring cabinets or instrument boxes were non-standard products and needed to be produced after the user provided information such as the number of I/O points, detailed I/O signal module types/quantities, and arrangement positions. With the adoption of universal I/O technology, the manufacturer's wiring cabinet or instrument box can be made into standard products, such as products with different I/O points. When the user provides the I/O points, they can be supplied directly without requiring the user to Provide detailed signal type, number of different modules, arrangement position and other information. The production of wiring cabinets or instrument boxes is standardized. It only needs to provide several basic models according to the number of I/O points. The design institute does not need to provide wiring cabinet or instrument box drawings, and the manufacturer does not need to complete separate cabinet layout and wiring. Figures and power and heat calculations. Standard products will reduce equipment configuration errors/wiring errors, speed up production, simplify acceptance testing, and reduce costs. As a standard product, it can be mass-produced before users place orders. Since there are no longer hardware design, cabinet design, cabinet complete sets, system function testing, etc., the supply cycle is shortened by about 1 to 6 months.

Since the general I/O technology of the control system usually installs a field instrument box nearby the site, this is equivalent to moving the I/O modules originally installed in the control room wiring cabinet to the field instrument box (see Figure 32). Its advantages are very prominent. In addition to the single cable connecting the field equipment to the field instrument box, a large number of other cables can be replaced by a single optical cable or electric cable. It saves investment, is quick to construct, and saves the space occupied by the wiring cabinet. In the traditional solution, an instrument signal requires two copper core wires to transmit. The new solution requires only a pair of redundant optical fibers to transmit hundreds of instrument signals, reducing cable laying costs to about 3% of the original cost. Optical fiber has a transmission distance of up to 20km without the need for relays, and can also achieve redundant transmission of on-site signals, with higher transmission efficiency and greater availability.

Various temporary change requirements often occur during the construction period of engineering projects, which often require the addition of equipment and cable laying, which may delay the construction period. For control system general I/O technology, in most cases, changes in engineering projects have less impact and higher tolerance, and can reduce the cost increase and time consumption caused by these changes. When adding field devices, as long as there are redundant I/O channels, the user only needs to lay the wiring to the wiring cabinet; if only the I/O type changes (such as the liquid level switching input signal is changed to an analog input signal), There is no need to re-wiring; outside the wiring cabinet or instrument box, since it has been aggregated into a bus or optical fiber for unified transmission, there is no need to add or change the wiring.

Control system I/O technical characteristics

The general I/O technology of the control system is designed with high-level redundancy performance in mind. For example, in Emerson's electronic wiring technology, all communications from CHARM to DeltaV S series controllers are completely redundant. Redundant CHARM I The /O card backplane has a redundant communication module, and each independent CHARM is also equipped with a redundant power supply and communication backplane, thus ensuring the reliability of the entire system in the I/O link. However, there is no redundancy in the CHARM link. This is because CHARM failure only affects one channel, and it can be replaced online without affecting the work of other CHARMs. In Hollysys' OpticVIO I/O technology, in addition to the power module, photoelectric conversion module, optical bus connection unit, control unit, and optical cable connection that are redundantly configured, even the IO module can also be redundant, so it can be to full redundancy.

Due to the following factors during the project implementation process, the total project cost can be significantly saved: reduction of wiring and control system infrastructure, increased I/O density of wiring cabinets/instrument boxes, reduced spare parts inventory, minimal changes caused by design changes, The engineering volume is reduced, maintenance labor costs are reduced, and performance is improved. The data given by Hollysys is that the area between cabinets has been reduced by more than 90%, the instrument and control system project cycle has been shortened by more than 50%, and the total project cost has been saved by more than 30%; the data given by Honeywell is that the number of cabinets has been reduced by 15 %~20%, the engineering time is reduced by 10%~15%, the debugging time is reduced by 20%~30%, and the total project cost is saved by 30%; the data given by Schneider Foxboro Company is that the total project cost can be saved by 35%

Just as the universal input technology of the display was widely welcomed as soon as it came out, the universal I/O technology of the control system not only realizes universal input, but also adds universal output based on the characteristics of the control system. At the same time, universal I/O technology also enables the wiring of field instrument boxes and control rooms to use cheap, large-capacity optical fibers to replace the copper core main cables, which improves signal transmission efficiency and saves a lot of materials and installation costs. Now general I/O technology not only benefits users, but also benefits manufacturers. This has become a trend in the development of control systems and formed a trend.