Hector Botero

Non Linear State and Parameters Estimation in Chemical Processes: Analysis and Improvement of Three Estimation Structures Applied to a CSTR

This paper proposes a new composite observer capable of estimating the states and unknown (or changing) parameters of a chemical process, using some input-output measurements, the phenomenological based model and other available knowledge about the process. The proposed composite observer contains a classic observer (CO) to estimate the state variables, an observer-based estimator (OBE) to obtain the actual values of the unknown or changing parameters needed to tune the CO, and an asymptotic observer (AO) to estimate the states needed as input to the OBE. The proposed structure was applied to a CSTR model with three state variables. With the proposed structure, the concentration of reactants and other CSTR parameters can be estimated on-line if the reactor and jacket temperatures are known. The procedure for the design of the proposed structure is simple and guarantees observer convergence. In addition, the convergence speed of state and parameter estimation can be adjusted independently.

Limitaciones de la Controlabilidad de Estados en los Procesos por Lotes

This work shows the most important barriers found when controllability of batch processes is analyzed. The need of including irreversibility and initial state irrecoverability into that analysis is highlighted. Two study cases are analyzed. The conclusion is that such systems do not verify the controllability and therefore it is only possible to analyze the reachability of this kind of batch processes. Furthermore, it is shown through simulations that control action effect is limited and there is a strong dependency between initial conditions and batch evolution, which must be considered in then design of batch process controllers.

A fixed-time convergent observer for biomass in a batch process

This paper presents an observer to estimate the biomass in a batch bioprocess, the δ-endotoxins production of bacillus thuringiensis. The proposed observer is based on a class of second order sliding mode algorithms, allowing a fixed-time estimation of the biomass. This last feature is specially important for the case of a batch process since the whole process is completed in a given time period. In addition, a simple scaling in the measured output variables is preformed in order to reduce numerical issues due to near to singularity states in the observability conditions. Simulations show the feasibility of the proposed observer. Convergence proofs are also presented.

Design of unknown inputs observer for a chemical process: Analysis of existence and observability based on phenomenological model

This paper explains the existence and observability conditions for the design of an Unknown Inputs Observer (UIO) for a chemical process. First, a phenomenological interpretation for the existence of the observer is given from the transfer function of the linearized system. And secondly, the existence and observability conditions of the observer are verified algebraically evaluating the rank of a defined observability matrix. Both ways of verification are compared. Finally, an UIO is implemented and simulation results are presented.

A high order sliding mode observer for systems in triangular input observer form

This paper deals with the design of a high order sliding mode observer for a class of nonlinear systems that can be described in the so called triangular input observer form. The mathematical tools required to make the system transformation to such form are also presented. At last, we show the performance of the observers with several simulation examples, including the application of a CSTR process model.

Specific Growth Rate Estimation in Fed-Batch Bioreactor Using Super Twisting Sliding Mode Observer

This paper presents the application of a second order sliding mode observer based on the classic super twisting algorithm in order to estimate the specific growth rate in a model of fed-batch bioprocess. This observer estimates the specific growth rate without assuming a specific model (such as Monod or Haldane), using the biomass concentration measurement. The observer allows the fixed time estimation of the specific growth rate, and provides robustness against uncertainty and parametric changes.

An equivalent control based second order sliding mode observer using robust differentiators

In this paper a sliding-mode observer for a class of non-linear systems is proposed. The observer is based on the equivalent control method. The mathematical tools required to design such an observer are also presented. The proposed scheme can ensure finite time convergence of the observer and the reduction of chattering effect due to relay-type correction terms. Several examples are presented to illustrate the proposed method.