In the current work, we propose optimal sensor placement
for reliable
estimation of both steady-state as well as dynamical nonlinear systems.
While there is significant work on reliability-based sensor placement
for linear processes, there is hardly any work for nonlinear systems.
For nonlinear systems, we use appropriate structural matrices to check
system observability for a given set of measurements and hence, our
work is applicable at the design stage where exact operating conditions
or values of various parameters may not be known. Characterization
of system observability, along with knowledge of sensor failure probabilities
as functions of time, allows us to define system reliability of estimation
as a function of time. Subsequently, we propose to use an information
theoretic, cumulative residual Kullback–Leibler (CRKL) divergence-based
sensor placement design approach for reliable estimation of variables
for both steady-state and dynamical nonlinear processes where the
objective is to minimize the difference between a user-specified target
system reliability of estimation function and the one obtained by
a given set of sensors. Thus, this approach enables an end user to
obtain a tailored optimal design by specifying their preference as
the target system reliability in the objective function. Explicit
incorporation of the time-varying nature of system reliability in
computing the CRKL objective ensures a sensor placement design that
leads to desired reliability throughout the life of the plant. The
proposed sensor placement design problem is a nonlinear integer programming
problem, and a greedy heuristic is used to solve the problem. The
utility of the proposed approach is demonstrated on benchmark continuous
stirred tank reactor and Tennessee Eastman case studies taken from
the literature.