Robust global state feedback stabilization of cement mills

peer reviewedPlugging 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 pluggin

A method for the reconstruction of unknown non-monotonic growth functions in the chemostat

We propose an adaptive control law that allows one to identify unstable steady states of the open-loop system in the single-species chemostat model without the knowledge of the growth function. We then show how one can use this control law to trace out (reconstruct) the whole graph of the growth function. The process of tracing out the graph can be performed either continuously or step-wise. We present and compare both approaches. Even in the case of two species in competition, which is not directly accessible with our approach due to lack of controllability, feedback control improves identifiability of the non-dominant growth rate.Comment: expansion of ideas from proceedings paper (17 pages, 8 figures), proceedings paper is version v

Fine-Scale Movements of the Broadnose Sevengill Shark and Its Main Prey, the Gummy Shark

Information on the fine-scale movement of predators and their prey is important to interpret foraging behaviours and activity patterns. An understanding of these behaviours will help determine predator-prey relationships and their effects on community dynamics. For instance understanding a predator's movement behaviour may alter pre determined expectations of prey behaviour, as almost any aspect of the prey's decisions from foraging to mating can be influenced by the risk of predation. Acoustic telemetry was used to study the fine-scale movement patterns of the Broadnose Sevengill shark Notorynchus cepedianus and its main prey, the Gummy shark Mustelus antarcticus, in a coastal bay of southeast Tasmania. Notorynchus cepedianus displayed distinct diel differences in activity patterns. During the day they stayed close to the substrate (sea floor) and were frequently inactive. At night, however, their swimming behaviour continually oscillated through the water column from the substrate to near surface. In contrast, M. antarcticus remained close to the substrate for the entire diel cycle, and showed similar movement patterns for day and night. For both species, the possibility that movement is related to foraging behaviour is discussed. For M. antarcticus, movement may possibly be linked to a diet of predominantly slow benthic prey. On several occasions, N. cepedianus carried out a sequence of burst speed events (increased rates of movement) that could be related to chasing prey. All burst speed events during the day were across the substrate, while at night these occurred in the water column. Overall, diel differences in water column use, along with the presence of oscillatory behaviour and burst speed events suggest that N. cepedianus are nocturnal foragers, but may opportunistically attack prey they happen to encounter during the day

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. © 2009 IEEE

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 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

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. (C) 1997 Elsevier Science Ltd