Доклади на Българската академия на науките Comptes rendus de l’Acad´ emie bulgare des Sciences Tome 64, No 5, 2011 SCIENCES ET INGENIERIE Automatique et informatique COMPOSITE ADAPTIVE CONTROL FOR A SIMPLE BIOTECHNOLOGICAL PROCESS MODEL Haoping Wang, Boyko Kalchev * , Ivan Simeonov * , Nicolai Christov, Christian Vasseur (Submitted by Corresponding Member P. Petkov on January 20, 2011 ) Abstract This paper presents a new Composite Adaptive Controller for trajec- tory tracking and disturbance compensation on the basis of a second-order continuous anaerobic digestion model. The proposed controller comprises an Algebraic Differential Estimation based compensation component and a Re- cursive Model Free Controller based stabilization component which does not require any knowledge of the model parameters. The proposed entire con- trol overperforms existing anaerobic digestion control schemes such as classical Proportional-Integral-Derivative control or a nonlinear PI control. Computer simulation examples illustrate the performance and robustness of the proposed approach. Key words: anaerobic digestion, piecewise continuous systems, algebraic differential estimation, recursive model free controller 1. Introduction. Anaerobic digestion (AD) is a biotechnological process widely used in life sciences and wastewater treatment and a promising method for solving energy shortage and ecological protection problems in agriculture and agro-industry. In such kind of processes, usually carried out in Continuously Stirred Tank bioReactors (CSTR), the organic matter is de-polluted by microor- ganisms into biogas (mainly methane and carbon dioxide) and digestate in the absence of oxygen [ 1, 2 ]. Despite the long history of practical experience and decades of academic study [ 3, 4 ], the control of AD seems still open. Many mathematical models of this process in CSTR of nonlinear ordinary differential equations with a great This work was supported by contract No DO 02-190/08 of the Bulgarian National Science Fund and the ARCUS Project funded by the French Ministry of Foreign Affairs and the Nord - Pas-de-Calais Region. 737