能帮忙翻译一下么，感激不尽那~~~~~~~~~~~~~~~~~~~~~~~~
Abstract: This is a practical approach to control a continuous-time process variable (temperature)
using a discrete controller (PLC) and a custom-designed software control algorithm and hardware
interface, in a closed-loop system. Unlike the conventionally known technique of transforming a
digital control action into a proportional analogue one by a D/A converter followed by power
amplifier, the control action was formed internally by the PLC as a PID/PWM signal, which was used to trigger the power stage. This approach helped reducing the error due D/A conversion, maximized utilization of the PLC and reduced total cost. The control system is realized by utilizing the heater of the training board (RGT1), manufactured by DL-lorenzo Company and it simulates an analogue heating control system. The PLC is Siemens Simatic S7-214 model. An experimental result has shown that the control algorithm functions perfectly.
Key words: PLC, PID software program, PWM, PLC, analogue input digital output, interface board
INTRODUCTION
The use of a digital signal processor (DSP) to evaluate the actual value of an analogue process output and then compute a correction signal has many advantages. DSP does not suffer from the long-term drift effect that analogue circuits do. Changes to constants can easily be made without the actual physical change to the circuitry and simply modifying the loaded program or loading a new one can radically alter the mode of control. Realizing PWM techniques and other advanced functions is some of the vast power points of digital controllers. Actually, in most cases DSPs are designed to replace the ON-line analogue ones. This explains the continuous approaches to implement digitally the traditional analogue control modes such as PID actions.
Because of the advantages of the PLCs, a PLC type S7-200 was utilized as a DSP. Nowadays most
modern sequential control systems are based on PLCs, which are in fact specialized industrial computers. Thus, one of the targets of this work is to design a PLC program for PID control algorithm and to develop it to get at the PLC output a PWM signal proportional to the value at the output of PID controller. In this case there is no need for a DAC IC nor for a specific power amplifier stage. Here the PWM signal with the power static switch emulates the function of a D-type power amplifier. From another side, by using the designed interface board, one can exclude the implementation of a high cost proprietary power interface module, this simplifies the circuit and reduces its cost.PLC manufacturers very often provide the option of analogue I/O and support instant PID functions for extra cost. （就是英文论文翻译，头大中，有高手能私下联系下么）