{'fraction_non_alphanumeric': 0.015197568389057751, 'fraction_numerical': 0.0, 'mean_word_length': 5.333333333333333, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
NONLINEAR FEEDBACK CONTROL BASED ON POSITIVE INVARIANCE FOR A NUTRIENT REMOVAL BIOLOGICAL PLANT

Activated sludge wastewater treatment processes are difficult to be controlled because of their complex and nonlinear behavior; however, the control of the dissolved oxygen and nitrogen levels in the reactors plays an important role in the operation of the facility. For this reason a new approach is proposed in this work. The paper describes the theory and applications of a nonlinear control technique, i.e., the so-called nonlinear feedback control. The control law consists of a linear feedback part which is designed using the positive invariance concept technique and a nonlinear feedback part without any switching elements. The control approach structure is combined with a state space estimation algorithm, for the on-line reconstruction of unmeasured biological states of the bioprocess. The efficiency of both the control and estimation is demonstrated via computer simulations.