Fabrice Jadot

Global stabilization of exothermic chemical reactors under input constraints

This paper is devoted to the temperature control and the stabilization under input constraints of exothermic chemical reactors. We first consider a reactor in which a single and exothermic reaction takes place and design state feedback controllers to achieve the global and robust stabilization under input constraints of the reactor. Then, we extend these results to a general class of exothermic reactors in which multiple coupled chemical reactions can take place

Robust feedback stabilization of chemical reactors

This paper deals with the temperature stabilization of a large class of continuously stirred tank chemical reactors. We design state feedback controllers, and we show their ability to globally stabilize the temperature at an arbitrary set point in spite of uncertainties on the kinetics. Furthermore, it is also shown that these controllers can handle input constraints along the closed-loop trajectories in some instances. For the implementation purpose, we design a robust state observer for the case of partial state measurement, and we prove that its incorporation in the feedback loops does not impair the nominal stabilization properties of the controllers.

Adaptive Regulation of Vector-Controlled Induction Motors

This paper addresses the speed and flux regulation of induction motors under the assumption that the motor parameters are poorly known. An adaptive passivity-based control is proposed that guarantees robust regulation as well as accurate estimation of the electrical parameters that govern the motor performance. This paper provides a local stability analysis of the adaptive scheme, which is illustrated by simulations and supported by a successful experimental validation on an industrial product.

Robust Global Stabilisation of Stirred Tank Reactors by Saturated Output Feedback

This paper is concerned with the robust stabilisation of a wide class of unstable processes operated in continuous stirred tank reactors, For non-isothermal reactors, the regulated output is the temperature. For isothermal reactors, the regulated output is the single concentration of either an initial reactant or a final product. In both cases the proposed control law is a dynamic output feedback which can be interpreted as a straightforward modification of a standard PI controller. In accordance with the engineering constraints, the control action is positive and saturated With this control law: it is shown that the output variable may be regulated at a prescribed set point despite a wide kinetic uncertainty. Furthermore, the controller achieves a global stabilisation of the process in its domain of physical existence. When the reactor is minimum phase, the closed loop has a single equilibrium which is globally asymptotically stable. When the reactor is non-minimum phase phase, a global practical output regulation with state boundedness is obtained with the same controller.

Robust stabilization of a nonlinear cement mill model

Plugging is well known to be a major cause of instability in industrial cement mills. A simple nonlinear model able to simulate the plugging phenomenon is presented. It is shown how a nonlinear robust controller can be designed in order to fully prevent the mill from plugging.

Optimal adaptive control of a bioprocess with yield-productivity conflict

This paper is concerned with the optimization of biological production processes. The process is characterized by a conflict between yield and productivity as revealed by the analysis of the model. The optimization problem is to find an operating mode that achieves the best trade off between yield and productivity. It is shown how this problem can be formulated as a parametric optimization involving parameters that have a clear engineering meaning. This parametric optimization leads to the definition of a control problem which requires a feedback implementation under the form of an adaptive regulator combined with a software sensor. A simple mechanistic model is considered as a benchmark example for this optimization study

Antiwindup Design for Induction Motor Control in the Field Weakening Domain

Operation of induction machines in the high-speed and/or high-torque range requires field-weakening to comply with voltage and current physical limitations. This paper presents an anti-windup approach to this problem: rather than developing an ad-hoc field weakening strategy in the high-speed region, we equip an unconstrained vector-control design with an anti-windup module that automatically adjusts the current and flux set-points so that voltage and current constraints are satisfied at every operating point. The anti-windup module includes a feedforward modification of the set point aimed at maximizing the available torque in steady-state and a feedback modification of the controller based on an internal model-based antiwindup scheme. This paper includes a complete stability analysis of the proposed solution and presents encouraging experimental results on an industrial drive.

Global state feedback stabilisation of cement mills

Plugging is well known to be a major cause of instability in industrial cement mills. A simple nonlinear model able to simulate the plugging phenomenon is presented. It is shown how a robust state feedback controller can be designed in order to globally stabilise the process and thus prevent the mill from plugging.

Robust stabilisation of chemical reactors

The design of stabilising feedback control laws for unstable chemical reactors has been studied extensively. There are nevertheless important theoretical questions that are still open. One of them, which is the main concern of this paper, is the design of feedback control laws that are globally stabilising, robust against kinetic uncertainties and robust against control input saturations. In this paper, for a general class of continuous stirred tank reactors, we propose a set of controllers that guarantee the global temperature stabilisation in spite of strong uncertainties on the dependance of the kinetic functions with respect to the temperature. A main feature of these controllers lies on their capability of handling input constraints in some instances. Moreover, if the reactor is globally asymptotically stable in isothermal condition, then our results turn into global stabilisation of both temperature and concentrations. (Here, we point out that in spite of the global asymptotic stability in isothermal condition, the overall dynamics of the open loop reactor can be unstable). The design is based on I/O state feedback linearisation with an appropriate dynamic extension.

Adaptive Optimal Control of a Penicillin Production Process : Design and Limits of Performance*

Abstract This paper is concerned with the optimization of industrial penicillin production processes. The process under consideration is characterized by a conflict between yield and productivity as revealed by the analysis of a prototype model of the process. The optimization problem is then to find an operating mode that will achieve the best trade off between yield and productivity. It is shown how this problem can be formulated as a parametric optimization involving parameters that have a clear engineering meaning. This parametric optimization leads to the definition of a control problem which requires a feedback implementation under the form of an adaptive regulator combined with a software sensor.