On-line control of dissolved oxygen concentration using an automatic tuning PID controller

With improvements in sensor reliability and computer systems, digital process control has been widely accepted as an effective way of improving the performance of fermentation processes, and of reducing operating costs. Despite the availability of methodical techniques for manually tuning PID controllers, the problem of finding an optimum set of controller parameters for the full operating range of the process can be arduous, time-consuming and prone to mistakes. In general, controllers which have fixed tuning parameter values, such as conventional PID controllers, are considered to be insufficient to cover a wide range of dynamic changes in fermentation processes. Improved performance can be achieved by adaptive techniques which monitor the time-variant dynamics of the process and adjust the controller tuning parameters to continuously optimise the performance of the closed-loop system.