Department of

Chemical Engineering

Designing molecular technology for the 21st century with biology and chemistry


Associate Professor Antonios Armaou | Research

Optimal actuator/sensor placement for
Transport-reaction systems & Fault tolerant controller design

The issue of actuator and sensor choice and placement has long been recognized as an important controller design aspect. The proper placement of sensor and actuator networks is especially critical for a large number of industrially important chemical processes which exhibit both variation in space and excitation due to disturbances of the process variables.

Such processes can be categorized as transport-reaction processes and examples include chemical vapor deposition reactors and plasma etching processes as well as the more traditional thermal processes. Mathematical models can be derived from dynamic conservation equations and usually involve parabolic partial differential equation (PDE) systems.

The traditional approach to construct the device network is to select the sensors/actuators locations based on open-loop considerations to ensure that the necessary observability/controllability or detectability/reachability or power factor requirements are satisfied. In this collaborative work, we consider the optimal placement of actuators for transport-reaction processes, mathematically modeled by parabolic partial differential equations in the presence of disturbance.

Using modal decomposition to discretize the spatial coordinate, and based on the definitions of spatial and modal controllability, the infinite optimization problem is formulated as appropriate nonlinear optimization problems of small size. Standard optimal search algorithms can now used to obtain the optimal locations.

At the same time, actuator, sensor and component failures have too often plagued chemical processes, often leading to deteriorating product quality and potentially dangerous process operation, such as runaway conditions. Motivated by the importance of the aforementioned failures, the issue of fault tolerant and fault accommodating controller design has recently become an active research topic in the chemical engineering. To address the issue of fault tolerance within the prism of an integrated design of actuator selection, we embark on a completely new direction, whereby the actuators and sensors are placed to enhance fault tolerability.

By taking advantage of the spatial variability that transport-reaction processes naturally enjoy, we endeavor on an entirely new design idea for fault-accommodating controllers. Our intention is to identify simple fault accommodation policies that significantly reduces the costs associated with process supervision with the obvious economic and performance savings.

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