| Figure 1: Hardware block diagram |
1.1 Control mode selection system mainly implements precise control of temperature. AI artificial intelligence instrument has various adjustment modes such as position control (ON-OFF), standard PID, AI artificial intelligence adjustment APID or MPT. For most electric furnaces, standard PID control is adopted. The method can meet the requirements of the process conditions. The user can set the M5, P, and t parameters to adjust the corresponding parameters to realize the user-defined adjustment. For the special temperature control system, CtrL enters the self-tuning adjustment. The advanced AI artificial intelligence adjustment algorithm has self-tuning, self-learning function, no overshoot and no undershoot. The control effect after self-tuning can basically be Meet the process requirements.
1.2 Sectional Power Limiting Mode Most electric furnaces in the system are resistance furnaces. A few high-temperature electric furnaces use silicon-molybdenum rods as heating materials. It is necessary to use step-down transformers. The short-circuit is similar to short-circuit, and the resistance is much lower than the high temperature. If power is not limited, the current at low temperatures will be much greater than the rated current. Set the CF parameter to make the meter use the power segmentation limit. At this time, the instrument output lower limit will not be limited, and the oPL will be used as the output upper limit when the temperature is lower than the lower limit alarm value LoAL. When the temperature is greater than the lower limit alarm value, the output upper limit is oPH. This provides a two-stage power limit function that effectively prevents the risk of excessive current during the initial heating.
1.3 Commissioning of control system For the control and detection of furnace temperature in some electric furnaces, the temperature of the furnace wall is monitored to calculate the temperature gradient distribution curve during the heating process of the electric furnace. Combined with the control, the pure hysteresis of the control object can be reduced and the Good control effect. The display of the same furnace temperature start condition is inconsistent and can be corrected by Sc. In the debugging process, the single-stage heating curve electric furnace first considers the self-tuning adjustment function of the AI ​​meter. The parameters that need to be set are M5, P, t and other parameters. The characteristics of each section of the heater are basically the same, and the self-tuning is satisfactory. Control effect, control accuracy is less than ±1 °C at constant temperature, and maximum overshoot is less than 2 °C.
2. The software structure and function of the control system
The system consists of a two-layer structure, and the upper computer is an industrial control machine to achieve centralized control and data acquisition and processing. The lower position machine is controlled by digital and analog quantity by PLC and on-site AI intelligent instrument. The system has two sets of manual and automatic control schemes, which can realize fast switching without disturbance. The main interface of the host computer control is shown in Figure 2 below:
| Figure 2: Main interface diagram |
Mainly achieve the following functions:
2.1 The main interface of the human-computer interaction function system displays the current layout and online status of each virtual device. The real-time data is dynamically refreshed and displayed according to different performance forms such as detailed data and maximum value data. The real-time curve of each parameter (temperature, flow, etc.) Drawing, on-site interface control of each switch, historical data query, EXCEL report generation, system alarm status and parameter setting of AI smart meter.
| Figure 3: Instrument settings and data display |
2.2 Database Management Management of real-time data and historical data, data storage and import into EXCEL.
2.3 User and system management The system is divided into system administrator, operator and security officer. Each role is restricted by different permissions. According to the actual system requirements, the sampling frequency setting, real-time refresh interval and alarm mode are managed.
3, the conclusion
The system has been successfully put into use in Guangdong Shaoguan Iron and Steel Plant. The system is safe and reliable. The distributed control system consisting of AI intelligent regulator, PLC and industrial computer has the advantages of strong anti-interference ability and high control precision, which greatly meets the process conditions. Various control performance indicators are required.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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