【正文】 effective, the user can browse, printing various field data, statements, and also to control the spot operation control. The temperature control system of single loop control system, by the Mitsubishi Co Fx2N series PLC as the core ponent, temperature detection using platinum thermal resistance KrlOO, used for realtime detection of temperature output, the RTD module is placed after the big into analog input module Fx2N 4AD, converted into digital quantity, the user procedure, call the PLC internal PID the control algorithm, a PID operational values, the values are converted into time value, to a timevarying PWM wave to control zero voltage trigger solid state relay SSR, to regulate the electric heating wire working current, to realize the heating furnace temperature control system. The software part Windows XP as the operating system, the industrial control configuration software MCGS as the application server platform. Between puter and PLC through the MPI port connection, the realization of PC and PLC munication. By the puter to plete the temperature setting, temperature and various control parameters realtime monitoring.3 PID control algorithm to achieve the PLC Using programmable controller for analog PID control, you can use the PID process control module, and this module is expensive, economy is poor. The system uses the PID function instruction, when P1D function instruction with the analog quantity when used together, not only can be similar to the PID process control module, and the economy is good. Due to the heating furnace is large delay, large inertia link control object, the system adopts the integral separation PID algorithm and Bang position Bang control methods, namely at the beginning of the process, the Cambodian guitar or substantially increase the set value, by using the Bang Bang control, prevent excessive deviation, integral accumulation, the system caused by larger overshoot even oscillation, so that the system stability decline. And to the process of the late, when the deviation to the specified range, increase the integral action, in order to improve the control precision. In the actual process of debugging, after several revisions of control parameters, can achieve good control parameters, to achieve the required precision.4 PID algorithm for converting the PWM wave output The adjustment of the temperature control is the control of the bidirectional thyristor turnon time, thereby changing the heating wire heating power to realize the temperature control. First of all, the PID operation result is converted into an internal timer timing value, to determine the delay time. This system adopts the power regulating circuit, control a power cycle in the actual conduction time, the output MV is converted to a time value mode. Due to the use of an internal timer time base for 10ms, T200, and because the power cycle selected for Tz, so the actual heating time for t:fⅢ100Tz detector, the time value is stored in the data register D, for timer instruction calls. In PLC, there are two ways to generate PwM output pulse wave, one is by the PLC PWM special instruction generated, but PWM wave output channels is limited, such as the FXzN series PLC only Y0 and Y1 two channels。 another is the internal timer to organization, the switch quantity output. The system uses second methods, by two timer T200 and T246 produce a PWM wave, T246 decided to transfer power cycle, in order to ensure the normal conduction of the thyristor main circuit, to ensure normal work, PLC output pulses and frequency to maintain strict synchronization relationship, therefore, will and power grid synchronization and to keep frequency relationship of basic digital pulse into the PLC input, as the timer T246 logic control signal, T200 decided to pulse width, delay time t by PID operation output value MV decision.5 conclusionsIn the control system of the furnace, the PLC is called when the builtin PID calculation program, realized PID control algorithm based on call, simplify program, improve the programming efficiency, and is not easy to make a mistake, the temperature reached the goal of accurate control。 at the same time, by the PID operation result decided width, with the timer generated PWM wave, switch quantity instead of analog output, realize the PWM wave output, allows the system to control cost. Proved by practice, this system has a fast dynamic response, high control precision, strong robustness characteristics.Change the heating wire heating power to realize the temperature control. First of all, the PID operation result is converted into an internal timer timing value, to determine the delay time. This system adopts the power regulating circuit, control a power cycle in the actual conduction time, need to be outputRegister D, for timer instruction calls. In PLC, there are two ways to generate PwM output pulse wave, one is by the PLC PWM special instruction generated, but PWM wave output channels is limited, such as the FXzN series PLC only Y0 and Y1 two channels。 another is the internal timer to organization, the switch quantity channel output. The system uses second methods, by two timer T200 and T246 produce a PWM wave, T246 decided to transfer power cycle, in order to ensure the normal conduction of the thyristor main circuit, ensure the normal work, the PLC output pulse must be with the grid frequency to maintain strict synchronization relationship, therefore, will and the electric power supply network sync and keep doubling between basic digital pulse into the PLC.Reference( 1 ) Chen Yuanqi, .F%N programmable controller for temperature monitoring and control system Design LJq. micro puter information, 2005, ( 15).( 2 ) the clock Zhaoxin . The programmable control theory and application EM . Guangzhou SCUT。University Press, .2003 ( 11).( 3 ) Song programming and practical guide ( M ) . Beijing : mechanical industry Press .2006 ( 6).譯文PLC在加熱爐溫控制系統(tǒng)中的應(yīng)用摘