Development of a hybrid PLC-based control system applied to a monitored fermentation process

It is well known that reliable and accurate control during biochemical processes is important, but sequential and continuous treatment requirements of bioreactors make this task difficult to achieve. In this paper, we report the development of a supervisory PLC-based control system that ensures complete bioreactor operation. Sequential phases founded during sterilization are accomplished by the programmable controller, while continuous regulation of main parameters (pH, temperature, and pressure) is achieved by control units using a PID (Proportional, Integral, Derivative) algorithm with feed-forward circuitry and auto-tuning feature. Finally, an operator graphic interface was developed in FIX MMI™'s intellution ® software, the man-machine interface provides supervisory and data acquisition functions. This system was successfully tested in E. coli and termophiles cultures; satisfactory control precisions of ±0.5°C, ±0.001 bar and ±0.1 pH unit were observed. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 197–206, 1999