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number of containers handled per hour, should be increased. Meanwhile, en-
ergy consumption needs to be reduced to adapt sustainability. In contrast to
building new terminal infrastructures, terminal management can be improved in
order to maximize the performance of the existing infrastructure, possibly in an
economical way.
Despite of the accumulation of literature on container terminal control (see,
e.g., [12]), there is a remarkable absence of research that provides energy-ecient
management of equipment at the operational level, considering the dynamics
and constraints of equipment. Object-oriented approaches [2,9], agent-oriented
programming [10, 15] and Mathematics-based approaches [1, 4] emphasize the
throughput without consideration for energy consumption, which is driven by
continuous-time dynamics. Little attention has been paid to sustainability of
container terminals. Emissions and energy consumption in container terminals
are emphasized in [13, 14]. Nevertheless, there, this issue was addressed at the
strategic level, instead of the operational level. Consequently, it is still not clear
how energy consumption can be reduced when it comes to operational container
terminal management.
The aim of this paper is to investigate how to improve the performance at
the operational level when combining throughput and energy consumption ob-
jectives. A container terminal is modeled as the combination of discrete-event
dynamics and continuous-time dynamics. Previous work [16] considered a hy-
brid model predictive control (MPC) approach. The MPC approach proposed
integrates throughput and energy consumption at the operational level, taking
into account dynamics and constraints of the system. However, the controller
involves solving a mixed-integer quadratic programming problem, which can be
very time-consuming. Therefore, in this paper a hierarchical controller is pro-
posed, based on a decomposition of the control problem into a control problem for
higher level discrete-event dynamics and one for lower level continuous-time dy-
namics. This approach aims at achieving energy ecient management of equip-
ment, while minimizing the makespan at the operational level. The actions for
each piece of equipment are determined to achieve the desired performance.
This paper is organized as follows. Section 2 describes the modeling of three
different pieces of equipment. Section 3 proposes a hierarchical control architec-
ture of the equipment. Section 4 illustrates the behavior of the proposed approach
in a simulation study. Section 5 concludes this paper and provides discussions
for future research.
2 Modeling of Equipment
In general, in a container terminal there are multiple types of equipment used to
handle containers. A container terminal is referred to as an automated container
terminal when the equipment can be controlled fully automatically without any
human intervention. There are multiple quay cranes (QCs), multiple automated
guided vehicles (AGVs) and multiple automated stacking cranes (ASCs) for trans-
porting containers from a vessel to the stacking area and vice versa. In this paper,
