Automatic loop tuning at water treatment plant: some implementation problems and their solutions

An overview of a CAD software tool developed for fast tuning conventional and predictive controllers has been given. The problem of outliers at water treatment plants has been the weakness of the popular relay auto-tuner and the online outlier removal technique described has provided a very effective, computationally inexpensive, solution to the problem. The Smith predictor described is also particularly simple and can easily be applied within conventional hardware. Many other predictive techniques have significantly higher computational burden that require specialised hardware, which, for many control loops cannot be justified. The paper has exploited several simple and well proven techniques to yield a particularly industrially-relevant design tool - a robust self-tuning procedure applicable to a wide range of process.