Abstract:
In this thesis, the COMAC ARJ21 fuselage’s final assembly process is used as a
case study. High production rate (i.e. number of aircraft assembled per year) with
reasonable cost is the overall aim in this example. The output of final assembly
will essentially affect the prior and subsequent processes of the overall ARJ21
production. From the collected field data, it was identified that a number of
disruptions (or bottlenecks) in the assembly sequence were caused by
breakdowns and maintenance of the (semi-)automatic assembly machines like
portable computer numerical control (CNC) drilling machine, rivet gun and
overhead crane. The focus of this thesis is therefore on the maintenance
strategies (i.e. Condition-Based Maintenance (CBM)) for these equipment and
how they impact the throughput of the fuselage assembly process.
The fuselage assembly process is modelled and analysed by using agent-based
simulation in this thesis. The agent approach allows complex process interactions
of assembly, equipment and maintenance to be captured and empirically studied.
In this thesis, the built network is modelled as the sequence of activities in each
stage. Each stage is broken down into critical activities which are parameterized
by activity lead-time and equipment used. CBM based models of uncertain
degradation and imperfect maintenance are used in the simulation study. A
scatter search is used to find multi-objective optimal solutions for the CBM
regime, where the maintenance-related cost and production rate are the
optimization objectives. In this thesis, in order to ease computation intensity
caused by running multiple simulations during the optimization and to simplify a
multi-objective formulation, multiple Min-Max weightings are applied to trace
Pareto front. The empirical analysis reviews the trade-offs between the
production rate and maintenance cost and how these objectives are influenced
by the design parameters.
