The
operation optimization problem (OOP) is an important issue
in production process control and optimization in process industries,
because the desired solution of OOP is the optimal setting for control
variables, and this setting affects the product quality to a great
extent. In this paper, the OOP in the hot-rolling production process
of iron and steel industry is investigated. The OOP lies between the
production scheduling layer and the process control layer in the integrated
automation system in iron and steel industry, and its main task is
to set the optimal values for control variables (i.e., rolling force,
exit thickness, etc.) based on the production process constraints.
These values are then set as the targets for the process control layer.
Different from previous operation optimization of hot rolling process
considered in the literature, the mathematical model constructed in
this paper considers more practical process constraints such as the
ramping constraints, to get high-quality products. To efficiently
solve this problem, a hybrid self-adaptive genetic algorithm (HSaGA)
is presented. The main feature of the HSaGA is that it utilizes four
different crossover operators and can self-adaptively select the operators
that are most appropriate for the current problem. Such a strategy
can help to improve the convergence speed and robustness of the genetic
algorithm. Besides this strategy, a solution selection strategy is
also proposed to select parent solutions to perform the crossover
operation. This strategy divides the entire population into two partsone
with good quality in the objective function value and the other one
with good quality in diversityand then the parent solutions
are selected from them, to improve the search diversity during evolution
and, thus, avoid being trapped in a local optimum. Experiments are
carried out based on benchmark test problems and practical OOP of
the hot-rolling production process. The computational results show
that the proposed HSaGA is superior to many state-of-the-art evolutionary
algorithms in the literature for benchmark problems and can obtain
better results than the empirical method for the OOP of the hot-rolling
process.